H51B-0439
GROUND AND SURFACE WATER QUALITY OF TSUNAMI AFFECTED SOUTHWESTERN COASTAL AREA OF SRI LANKA
The major tsunami of December 2004 hit many South Asian countries bordering the Bay of Bengal and severely devastated the coastal region of Sri Lanka. In the coastal areas of south western Sri Lanka the majority of the population, relies on groundwater for their domestic and agricultural activities, predominantly through traditional private shallow open-dug wells. The study area is located 100 km south of the capital city of Colombo, and was greatly affected by flood waves. The coastal plain is characterized by shallow natural lagoons. Analyses of major parameters (NO3-, PO43-, F-, NH4+, Fe, As, pH, chemical oxygen demand (COD) and electric conductivity) in 40 randomly selected dug wells and surface lagoon water samples were made using field pack test method. Lagoon water parameters (pH, conductivity, dissolved oxygen (DO), total dissolved solid (TDS) oxidation reduction potential (ORP) and salinity) were tested at 18 different locations at varying depths. Soil and tsunami sediment samples where analyzed using XRF for major oxides and trace elements. Results showed that some wells were contaminated with NO3- and many wells had higher COD and salinity. Lagoon water parameters showed High salinity and low DO. ORP of the lagoon water showed reduced conditions occurred even in shallow water depth with more negative values for lagoon sediment samples. The XRF analyses showed that high concentrations of Cl, Br and I in lagoon sediments. The results show that dug-wells can be further contaminated with lagoon water, Water from mash lands and by tsunami sediments. Halogen compounds in lagoon sediments are also released in to the groundwater and increase salinity. Contamination is highly dependent on local and regional flow conditions of the groundwater. Key words: Sri Lanka, tsunami, groundwater, dug-wells
H51B-0440
Polar Organic Compounds in Surface Waters Collected Near Lead-Zinc Mine and Milling Operations in Missouri
Surface-water samples were collected near a lead mine and mill tailings about 70 miles southwest of St. Louis, Missouri, during the summer of 2006. The purpose of this sampling was to determine if polar organic compounds were present that could be a cause of documented negative impacts to biota downstream. Water samples contained relatively high concentrations of dissolved organic carbon for surface waters (greater than 20 mg/L), but were colorless, which precluded naturally occurring aquatic humic or fulvic acids. Previous analysis indicated that samples were devoid of pesticides and acid/base/neutral extractable semi-volatile organic compounds, such as polycyclic aromatic hydrocarbons. After isolation by three different types of solid phase extraction, samples were analyzed by electrospray ionization/mass spectrometry. Polar organic compounds commonly used in the milling process, such as alkyl xanthates, were not found; however, xanthate degradation products were detected. Most of the polar organic compounds identified contained sulfonate groups, which are characteristic of some of the reagents used in the milling process. Sulfonate compounds may have low sorption onto soil or sediments and be mobile in the aqueous environment.
H51B-0441
Benthic Fluxes of Dissolved Macro- and Micronutrients to the Water Column of Upper Klamath Lake, Oregon
Hypoxic, environmentally stressful conditions for endangered fish populations have been generated over the past century by an annual phytoplankton bloom in Upper Klamath Lake, OR. The bloom is consistently dominated by the nitrogen-fixing cyanophyte Aphanizomenon flos–aquae (AFA), thus a quantitative understanding of processes affecting the transport of biologically available phosphorus (P), presumably the limiting nutrient, is critical for resource management in the lake. This work was undertaken to help develop sound remediation or restoration strategies, and to set realistic expectations for water-quality improvements. Particle-reactive phosphate can adsorb or complex onto particles that settle and accumulate in the lake bed. Biogeochemical processes near the sediment-water interface can remobilize particle-bound P and generate a benthic flux of bioavailable P. This study provides estimates of the benthic flux of dissolved macronutrients (i.e., phosphorus and nitrogen species) before, during and after the period of: (1) increased water-column nutrient concentrations that cannot be accounted for by riverine inputs, and (2) the annual bloom of AFA. Benthic flux of dissolved orthophosphate was consistently positive (i.e., out of the sediment into the overlying water column) and ranged between 0.5 and 6.1 mg m-2 d-1. Assuming a lake area of 200 km2, this converts to a mass flux to the entire lake of 8,000 to 100,000 kg over a 3-month AFA bloom season which is comparable in magnitude to riverine inputs. An additional concern related to fish toxicity was that dissolved ammonium also displayed consistently positive benthic fluxes of 4 to 100 mg m-2 d-1; also comparable to riverine inputs. In contrast, dissolved nitrate exhibited a consistently negative flux (consumed by the sediment) with values ranging between -20 to -0.1 mg m-2 d-1. Macroinvertebrate densities of the order of 105 individuals-m-2 suggest that the diffusive-flux estimates may be significantly lower than actual values due to bioturbation. Although phosphorus is a logical choice for the limiting nutrient when nitrogen-fixing cyanophytes dominate, initial trace-metal results in the form of coordinated benthic flux, water-column and tributary-inlet data suggest that iron availability to primary producers in the lake is possibly a limiting factor. http://wwwrcamnl.wr.usgs.gov/solutetransport/index.htm
H51B-0442
Temporal and Spatial Variations in Total Suspended and Dissolved Solids in the Upper Part of Manoa Stream, Hawaii
Hawaiian watersheds are small and steep and receive large amounts of rainfall with a strongly non-uniform distribution. Therefore streams are flashy in nature which has its effect on water quality. Total suspended solids (TSS) and total dissolved solids (TDS) were used to investigate the variability in water quality parameters in the upper part of Manoa Stream in Honolulu. With a few interruptions, water samples were taken on a daily basis between October 2005 and June 2006. TSS and TDS varied from nearly nothing to 724 and 302 mg/l, respectively. TSS and TDS did not show a correlation with discharge. Data from a separate study by US Geological Survey, performed between 1991 and 2001 for the same stream, showed values for TSS up to 1320 mg/l for discharges higher than measured in this study. For the high discharges of the USGS data TSS showed an increasing and TDS a decreasing trend. It is concluded that the rainfall leading to extreme discharges (> 5 m3/s) causes more land and channel erosion and dilutes the solutes in base flow. At lower, more common discharges the system is supply-limited and affected by local conditions. The results of this study stresses the necessity of recognizing the variability in small streams for setting up a monitoring strategy, building a model to describe water quality or extrapolating water quality data to annual loads.
H51B-0443
Experimental Observation and Modeling of Effects of Precipitation on the Stream-Subsurface Exchange of Copper
Assessment of contaminated rivers and effective remediation of streams affected by acid mine drainage require a thorough understanding of the dominant mechanisms controlling the fate and transport of contaminants. Such studies are generally complicated due to the complex coupling of hydrologic and geochemical processes. The importance of hyporheic exchange has become increasingly recognized because of its important role in regulating the transport of particles, contaminants, and ecologically relevant substances. Substantial accomplishments of fundamental understanding of the transport processes have been achieved by several researchers. However, a variety of issues still limit the application of the current process-based transport models in natural streams. One of the critical limitations arises from the fact that a wide range of additional processes such as metal precipitation reactions are also expected to influence contaminant transport in natural streams significantly but have not been adequately represented in any fundamental process-based stream-subsurface exchange models. In this study, laboratory flume experiments were carried out using copper (CuCl2) to examine the effects of pH-dependent metal precipitation on the stream-subsurface exchange process. Batch experiments were conducted to characterize the precipitates formed and the extent of sorption occurring at different pHs. Column experiments were used to determine the mobility of copper precipitates formed. A multi-phase reactive exchange model which accounts for the metal precipitation process was developed and applied to interpret the flume experiment results.
H51B-0444
Assessment of Groundwater Vulnerability for Antropogenic and Geogenic Contaminants in Subwatershed
Groundwater is an important natural resource that providing drinking water to more than five million people in Korea. Nonpoint source nitrate was frequently observed contaminant and the investigation result for small potable water supply system that mainly consisted of 70 percent groundwater showed that about 5 percent of water samples exceeded potable water quality standards of Korea. The geogenic contanminants such as arsenic and fluoride also frequently observed contaminants in Korea. In order to protect groundwater and to supply safe water to public, we need to assess groundwater vulnerability and to know the cause of occurrence of contaminants. To achieve this goal, we executed groundwater investigation and assessment study for Keumsan subwatershed with 600km2 in Keum-river watershed. The geostatistical and GIS technique were applied to map the spatial distribution of each contaminants and to calculate vulnerability index. The results of logistic regression for nitrate indicated the close relationship with land use. The results of hydrogeochemical analyses showed that nitrates in groundwater are largely influenced by land use and had high values in granitic region with dense agricultural field and resident. The high nitrates are closely related to groundwater of greenhouse area where large amount of manure and fertilizer were usually introduced in cultural land. The soil in granitic region had high contents of permeable sand of weathered products of granite that play as a role of pathway of contaminants in agricultural land and resident area. The high values of bicarbonate are originated from two sources, limestone dissolution of Ogcheon belt and biodegradation organic pollutants from municipal wastes in granitic region with dense agriculture and residence. It is considered that the anomalous distribution of arsenic and fluoride is related to limestone and metasedimentry rock of Ogcheon belt with high contents of sulfide minerals and F bearing minerals. The ubiquitous old fluorite and coal mines in Ogcheon belt are considered the main source of arsenic and fluoride in groundwater.
H51B-0445
Seasonal and Interannual Variations of Stream Chemistry in an Urban Fringe Watershed in Southern California
Understanding the hydrological, geochemical and biological watershed processes involved in ecosystem evolution involves numerous scientific challenges. The transition from undisturbed to urbanized landscapes has impacted ecosystems worldwide. Of critical concern is ecosystem degradation in undisturbed watersheds due to regional atmospheric deposition. This study focuses on the undeveloped, upper reaches of the Arroyo Seco watershed, located on the eastern edge of the Los Angeles basin, where estimates of dry deposition are considered some of the highest in North America. Weekly water quality grab samples were collected from April 2004 to December 2006 and analyzed for standard geochemical constituents. Atmospheric wet deposition for different constituents was obtained from the National Atmospheric Deposition Program (NADP) site located in eastern Los Angeles County. Hydrologic, geochemical and atmospheric data were assessed at various time scales to evaluate current hydro-geochemical dynamics and ecosystem response to the impacts of large-scale regional urbanization. For almost all the constituents, streamwater concentrations are higher in the fall and lower in the spring, while atmospheric wet deposition values are higher in the summer and lower in the winter. The streamwater chemistry also exhibits interannual variation which can be primarily explained by the interactions of the hydrological and biogeochemical cycles. Seasonal stream concentration-discharge relationships were developed using a hyperbolic dilution model. In general, the developed model results in a better fit for the cations rather than anions. Model results were used to predict seasonal and annual mass loadings to downstream urban streams. Both observations and model predictions indicate the watershed is a sink for atmospheric nitrate and a source for various cations.
H51B-0446
Effects of Levee Construction on Hydro-chemical Conditions in the Kushiro Mire, Northern Japan
In most cases, drastic changes in mire ecosystems have arisen from cumulative effects of nutrient loads and changes in the water balance of the catchment associated with various human activities. Such changes are serious issues in Japan, for example, in Kushiro Mire, the largest floodplain mire in the country. A rapid transition from a sedge/reed-dominant fen to an alder forest has occurred, especially in mire areas where levees have been constructed for flood management. Although hydro-chemical conditions are suspected to have occurred because of the levee, few attempts have been made to clarify the levee effects on conditions. This study clarifies the levee effects on hydro-chemical conditions. Mire areas around levees showing vegetation changes were investigated. The levee effects were examined through comparison of areas inside and outside of the levee. Three transects (almost 1.5 km long) were set to intersect the levee, and observation wells were set at 50 m intervals in each transect. Groundwater tables and chemical compositions were measured during 2005–2007. Furthermore, the vertical hydraulic gradient (VHG) was measured using a new method with a digital manometer. Although groundwater tables were generally higher near the end of transect inside the levee area, the dry season water tables became lower and fluctuations gradually increased with proximity to the levee. These effects were caused by a drainage ditch that was dug to protect the levee. However, no significant differences were found between conditions inside and outside of the levee. The groundwater chemistry indicated that nutrients such as NO3-, SO42-, K+, Mg2+ and Ca2+ concentrations were significantly higher near the levee because chemical fertilizers used for grass planted on the levee slope ran off into the mire. In the centers of the transects inside the levee, Na+ and Cl- were higher and upwelling of groundwater were identified using VHG distributions. Moreover, the Na+/Cl- ratio resembled that of seawater. These results indicate that seawater existing under the peat layer is upwelling. Although the reasons were not clarified, the upwelling might be an effect of the levee's existence because these were observed at each transect.
H51B-0447
Effects of Levee Construction on Groundwater Flow in the Kushiro Mire, Northern Japan
Degradation of mire ecosystems has resulted from changing hydrological conditions associated with watershed developments because the biota are related strongly to hydrological conditions. In Kushiro Mire, the largest in Japan, drastic changes in vegetation have been observed since the 1970s. Those changes have been manifested as a transition of a sedge/reed-dominated area into alder forests. Furthermore, large levees were constructed throughout the mire for flood management. After their construction, vegetation changes have occurred around the levee. It was presumed that the changes resulted from hydrological condition changes. This study is intended to clarify effects of the levee on hydrological conditions. This study was conducted in the mire, which has both the levees and vegetation changes. Each groundwater investigation and numerical analysis of ground-water flow was performed using MODFLOW software. A belt transect (1.5 km long) was set to intersect the levee; observation wells were set at 50 m intervals. Investigations of the groundwater table and vertical hydraulic gradient (VHG) were performed with a digital manometer during 2005–2006. Because of the investigation, the water table was lower than the ground surface in summer. The water table varied more in areas closer to the levee. The VHG distribution indicates that down-welling occurred near the levee, and upwelling occurred at the middle transect area in the protected area. Results suggest that groundwater was drained by a drainage ditch which was set to protect the levee. Two-dimensional cross-sectional analysis was conducted in each case before and after (present status) levee construction. Results indicate that flow directions differed between the former and the latter cases, and that the present water table is lower. The latter case showed that water in the levee is infiltrating into the mire area because the water table at the levee was higher than around the mire area. As shown by results of VHG investigation, upwelling at the middle transect area was shown for the latter case. In contrast, it was never shown for the former case. These results suggest that the upwelling was caused by the levee. The existence of the levee lowered the mire water table and influenced the direction of groundwater flow around the levee.
H51B-0448
Trend Analysis For Nitrate And Chloride Concentrations Of Groundwater In Jeju Island
The purpose of this study is to evaluate the trend of groundwater contamination in Jeju Island. We collected and analyzed 8,795 groundwater quality data which has been reported from 1989 to 2006 by Jeju Provincial Institute of Health and Environment. To analyze the trend of groundwater quality, we focused on the variations of chloride and nitrate concentration which are considered to be the most influencing components for groundwater quality in Jeju Island. The regional trend of groundwater quality was evaluated by using the lattice concept. Single grid was determined to be 500m x 500m considering aquifer features of volcanic rocks and low-slope topography and 7,361 rectangle grids were drawn for the whole island. All data within each lattice were collected and arranged in time series order and analyzed by using Sen's method. Although any trends of the average monthly concentrations for chloride and nitrate are not found, 32 lattices (16.2 percent) of total 198 lattices showed upward trend of chloride concentration and 46 lattices (22.5 percent) of total 205 lattices showed upward trend of nitrate concentration. Especially, upward trends for nitrate concentration are distinct in the low mid-mountainous areas (EL 100 to 250m) of western and southern watersheds, which original forests have been continuously urbanized or cultivated since early ¡®90s. Therefore, to maintain good groundwater quality in Jeju Island, future groundwater management needs to be carefully focused on the land use decisions in the mid-mountainous areas near Halla Mountain.
H51B-0449
Watershed Scale Observation and Analysis of Stream Temperatures in the Ibogawa River, Japan
In this study, we reported monitoring results of stream temperatures in the Ibogawa river basin, Hyogo prefecture, Japan. We, then, examined relative contributions of each component in a theoretical solution of stream temperature conservation equation. The solution of the thermal energy equation was derived with the method of characteristics and Taylor-series approximation. In the Ibogawa River, 27 observation points were set up in order to sequentially monitor the stream temperatures in the whole watershed extent. Spatial distributions of the monthly averaged stream temperatures, spectral characteristics of the temperature time series, and one-day moving averaged temperatures with meteorological and hydrological data were discussed in detail. The spatial distributions of the monthly averaged stream temperatures showed their increase behavior from the upper stream to the river mouth. Comparison of the temperature time-series between the main stream and tributary indicated much difference in their temperature change. Moreover, the Spectral analysis showed that the diurnal fluctuation of the solar radiation affected very much on thermal energy balance in the whole river system. It was also found that the temporal fluctuations longer than the diurnal fluctuation were formed mainly due to the changes of meteorological and hydrological conditions, i.e., the sunlight duration, precipitation, and the river discharge. Then, we examined relative contributions of each component in the thermal energy equation in terms of different time scales. It was found out that the equilibrium temperature, i.e., the solar radiation influence, was of much importance for the monthly averaged stream temperatures in the watershed, while the convection and unsteady terms in the thermal energy equation, i.e., hydrological influence, emerged to be significant in the shorter, less than the 5-day, averaged stream temperatures.
H51B-0450
Spatio-Temporal Controls of Stream Water Nitrogen Export in a Rapidly Developing Watershed in the Northern Rockies
Human alteration of the patterns of land use/land cover (LULC) on the earths surface is one of the most profound impacts on the functioning of natural ecosystems. At the watershed scale, we expect that not only the amount and type of landscape alteration, but also its spatial distribution and the corresponding watershed characteristics, hydrologic conditions, and biological season will dictate the spatio-temporal patterns of streamwater nitrogen (N). We conducted six synoptic sampling events (50 sites) and weekly streamwater sampling (7 sites) in the West Fork Watershed, a 212 km2 mountainous watershed in Southwestern Montana, which drains the rapidly developing Big Sky resort community. Synoptic sampling campaigns captured each season and a range of hydrological conditions and biologic activity. Samples were analyzed for inorganic and organic forms of nitrogen. We performed exploratory multiple regression analysis to determine the explanatory variables for spatio-temporal streamwater nitrogen (N) patterns. Variables considered included DEM derived hydrologic features (e.g. stream order, upland travel time, slope, aspect, riparian area, riparian buffer ratios, and watershed area), geology, forest cover, and septic locations. These variables were used in generalized least squares with a spatial correlation model based on weighted stream distance to predict streamwater nitrate concentrations. We found greatest correlation (adj r2 =0.90) in the winter with variables including number of septic locations, upland fertilization, and geology. This suggests nitrogen loading to the watershed was more conservatively transported through the uplands and stream network in the winter. In the late summer, however, transport and related biological variables became more important, and included travel time weighted septic loading locations, riparian hillslope buffer ratios, and stream order (adj. r2 =0.21). Here, we present the results of our exploratory statistical analysis as a first step toward modeling the impact of watershed location and spatial distribution of LULC change on the spatial, seasonal, and speciation patterns of streamwater N.
H51B-0451
Transient Storage of Suspended Particulate Material in a New England Stream
Suspended particulate material (SPM) poses physical, chemical, and biological concerns for water quality. These particles can disrupt the connection between stream and ground water, as well as serve as carriers for sorbed pollutants, such as heavy metals and phosphorus. Excess SPM can degrade overall stream habitat and ecosystem health. Although watershed sediment loads are often monitored, less is known about the hydrologic transport of these particles through the stream network to the watershed outlet or monitoring location. The in- stream transport of SPM can be influenced by transient storage mechanisms, such as settling and resuspension, stagnation in pools, exchange with the streambed or hyporheic zone, and entrapment on stream vegetation and behind coarse woody debris. A tracer injection experiment was performed in order to compare the hydrologic transport of suspended clay-sized particles, composed of titanium dioxide (TiO2, 0.5 μm diameter), with that of a conservative solute, bromide (Br). The solute and particle tracers were added to a second-order, ungaged stream in northwestern Connecticut. Water samples were collected at six downstream locations over a 500 m stream reach, containing both run and step-pool geomorphology. A one-dimensional numerical model was applied in inverse mode to the measured breakthrough curve data in order to quantify the processes that governed solute and particle transport. The results of this analysis indicate that solute and particle transport was influenced by advection, dispersion, and transient storage. Transient-storage processes, particularly in pools, exerted influence on the transport of bromide and TiO2 with different timescales of release. Bromide was often released more quickly from pools than TiO2. Results of our analysis illustrate the mechanisms and relative timescale of SPM transport within a stream reach and provide insight into the potential response of SPM concentrations to elevated sediment inputs.
H51B-0452
Experimental Study and Modeling of the Stream-Subsurface Exchange of p,p'-DDE in the Presence of Naturally Occurring Fine Particles
The stream-subsurface exchange process plays a significant role in the fate and transport of contaminants in streams due to the increased interactions between contaminants and bed sediments. The presence of suspended sediments such as naturally occurring fine particles is known to introduce large reactive surface areas which allow them to sorb contaminants and modify the contaminant behavior in natural streams. In this study, experiments were conducted in a recirculating flume to investigate the stream-subsurface exchange of p,p'-DDE in the presence of kaolinite colloids and natural river sediments. p,p'-DDE was analyzed using a gas chromatography with an electron capture detector combined with a solid-phase microextraction (SPME) technique. A process-based multi-phase exchange model considering kinetic sorption/desorption of DDE to both the bed sediments and suspended particles was applied to interpret the experimental results. The model input parameters were obtained using independent small-scale batch experiments. Results presented here will contribute to the mechanistic understanding of the complex transport processes in natural streams and to the development of reliable, predictive models for the assessment of contaminated streams.
H51B-0453
In-Stream Nitrate Immobilization Across Development Gradients and Stream Network Position in a Rapidly Developing Mountain Watershed, West Fork of the Gallatin River, Big Sky, Montana.
Nitrogen immobilization in streams is an important process and partially determines the balance between N removal and N export from headwater catchments. In-stream immobilization of streamwater N is well-studied, yet poorly understood, especially as one moves from reach to stream network scales, and across morphologic or ground water- surface water exchange gradients, seasons, and ranges of ambient N concentrations. Our goal was to quantify the range of in-stream NO3- immobilization rates across the stream network by comparing low and elevated ambient NO3- streams and to assess the role of the stream network in modifying observed watershed N loading patterns and export dynamics. We focused on the 200 km2 rapidly developing montane watershed of the West Fork of the Gallatin River, Big Sky. This site provides an ideal natural laboratory for analysis of landuse change impacts on water quality because of its montane ecosystem, accelerated land development, and adjacent wilderness. We conducted 31 stream tracer tests (15 steady-state and 16 slug additions) across eight, 400-1250m stream reaches, with a range of ambient NO3- concentrations (<0.01-2.17 mg/l) and watershed size (0.408-85 km2). Each of the eight streams was paired for comparison based on similar watershed area and total discharge; each pair included a stream of high and low ambient NO3-, reflecting varying degrees of exurban development and upland wastewater disposal. Quarterly assessments of montane in-stream N immobilization were also conducted to assess seasonality. For each stream addition, we tracked a concurrent conservative (NaCl) and non-conservative (KNO3) tracer with synoptic and breakthrough curve sampling. We further characterized gross and net streamflow gains/losses over each reach with mass recovery methods. This work represents a first step toward integrating watershed and stream network biogeochemistry in a rapidly developing mountain watershed.
H51B-0454
Effects of a Flash Flood on Physical Stream Characteristics and Nitrate Uptake in an Urban Stream
High flow conditions can influence the characteristics and behavior of streams. We performed a study comparing physical stream characteristics and how they are related to nitrate uptake on three reaches of an urban stream before and after a flash flood. We developed a detailed protocol for characterizing physical attributes along the stream reach, including pebble counts, longitudinal thalweg survey, width variability survey, cross-section surveys, hydraulic measurements, and spatial distribution of physical habitat units. Along with the physical characterization of each reach, we performed nutrient injections to estimate the amount of nitrate uptake occurring over the reach. Benthic organic matter content and whole-stream metabolism were also measured in each reach. Comprehensive data sets were collected at each of three reaches along one stream at pre- and post- flood conditions. By comparing variations in physical stream characteristics and nitrate uptake before and after flash flood conditions, we explored how sudden increases in flow can modify physical attributes of the stream that may influence the uptake of nitrate. We further investigated if particular physical characteristics of the stream reach are associated with nitrate uptake.
H51B-0455
Groundwater flow system and Nitrogen cycle in volcanic aquifer of pyroclastic flow uplands, Japan
Study area is well-known agriculture area in Southern Kyushu, Japan and highly depends on groundwater resources for their everyday use. Local unconfined groundwater aquifer is widely polluted by Nitrate-Nitrogen originated from agriculture and cattle farming. It will become serious problem if this unconfined Nitrate pollution enlarges into the confined aquifer system which is used for local city water source. The detailed three dimensional groundwater flow system study has been done by using existing wells in the basin to understand the three dimensional distribution pattern of Nitrate-Nitrogen in the aquifer. However, the detailed groundwater age analysis by using Tritium for unconfined and confined groundwater has not been succeeded because of present low atmosphere tritium concentration. Thus we applied to challenge the CFCs dating method. Although the CFCs method has been widely used for dating the young groundwater instead of tritium in many countries, in Japan CFCs has been used only by Oceanographic study and has not been used in the field of Hydrology. The history and fate of Nitrate contamination have been shown in multidisciplinary local transect studies in areas with agricultural sources (Bohlke and Denver 1995). However, identification of Nitrogen sources can be difficult in larger regional studies because of co-occurrence of multiple anthropogenic Nitrogen sources and uncertainty in Nitrogen transformation pathways. Thus, the characterization of N geochemistry remains challenging, particularly in aquifer-scale assessments (Stephen 2006). In this study, the evidence of the shallow groundwater flowing towards deep aquifer was verified by the groundwater dating and the detailed Nitrogen reduction process was confirmed along the groundwater flow.
H51B-0456
Identification of Water Source Areas Using a Multi Tracer Approach in a Semiarid Catchment in Inner Mongolia, PR China
The upscaling of hydrologic process understanding to mesoscale catchments is challenging, in part because of measurement limitations: we cannot characterize the hydrometric response of large catchments using standard hydrometric measurement protocols. Tracer-based approaches, however, do have significant potential to contribute to our understanding in larger catchments. The application of tracer-based approaches to catchment characterization are increasingly common, and are of particular interest to a number of recent research initiatives including PUB, which have been formulated based upon the clear need for the hydrologic sciences to more fully contribute to watershed management strategies at larger scales. This study was designed to identify water source areas and flow paths in the previously ungauged basin of the 3600 km2 comprising catchment of the Xilin river, Inner Mongolia, P.R. China, in order to improve process understanding for further model development. The catchment is characterized by a relatively homogenous land use consisting of large steppe and sand dune areas used for grazing purposes and few small villages. There is no industry which could act as contaminating point sources to the river. We hypothesize that the water chemistry of the Xilin river reflects the composition of the underlying soils and geology. Snapshot sampling was conducted during summers of 2005 and 2006. Samples taken were analyzed for elemental composition with an inductively coupled plasma mass spectrometer (ICP-MS) and for anions with an ion chromatograph (IC). Also, in situ measurements of pH and EC were conducted. In this paper we present mixing diagrams and results of multivariate statistical analysis to better understand and quantify the sources of streamflow. Our results suggest that a simple three component mixture model is capable of describing the water composition during the vegetation period. The three components identified are one groundwater, one tributary and a headwater source.
H51B-0457
Effects Of Leaky Sewers On Groundwater Quality
The impact of urban areas on groundwater quality has become an emerging research field in hydrogeology. Urban subsurface infrastructures like sewer networks are often leaky, so untreated wastewater may enter the urban aquifer. The transport of wastewater into the groundwater is still not well understood under field conditions. In the research platform WASSER Leipzig (Water And Sewershed Study of Environmental Risk in Leipzig- Germany) the effects of leaky sewers on the groundwater quality are investigated. The research is focused on the occurrence and transport of so-called "xenobiotics" such as pharmaceuticals and personal care product additives. Xenobiotics may pose a threat on human health, but can also be considered a marker for an urban impact on water resources. A new test site was established in Leipzig to quantify mass fluxes of xenobiotics into the groundwater from a leaky sewer. Corresponding to the leaks which were detected by closed circuit television inspections, monitoring wells were installed up- and downstream of the sewer. Concentrations of eight xenobiotics (technical-nonylphenol, bisphenol-a, caffeine, galaxolide, tonalide, carbamazepine, phenazone, ethinylestradiol) obtained from first sampling programmes were found to be highly heterogeneous, but a relation between the position of the sampling points and the sewer could not be clearly identified. However, concentrations of sodium, chloride, potassium and nitrate increased significantly downstream of the sewer which may be due to wastewater exfiltration, since no other source is known on the water flowpath from the upstream to the downstream wells. Because of the highly heterogeneous spatial distribution of xenobiotics at the test site, a monitoring concept was developed comprising both high-resolution sampling and an integral approach to obtain representative average concentrations. Direct-push techniques were used to gain insight into the fine-scale spatial distribution of the target compounds. An integral pumping test was performed to determine the total xenobiotic mass fluxes along control planes down- and upstream of the leaky sewer. The new monitoring concept helped to obtain robust estimates of xenobiotic mass fluxes into the groundwater.
H51B-0458
Hydrogeochemical modelling of a saline pollution in alluvial groundwater: the example of the Rhine aquifer
One of the newest challenges to the earth science is to build numerical approaches that are able to combine both hydrological and geochemical constraints. The objectives are broad and may concern both the water quality and the determination of reaction rates at the water/rock interface. To explore the hydrogeochemical behavior of groundwater, we focused on the alluvial water table of the Upper Rhine valley because it has undergone a huge pollution related to the exploitation of the Alsace potash mines during the XXth century. This offers the opportunity to know with precision the nature of the pollution by infiltration of saline waters and point zero in space and time. Examination of Na+ and Ca2+ concentration values revealed that a loss of Na compared to Cl occurs together with a gain in Ca. This chemical observation is not consistent with a single dilution process and strongly advocate for ion exchanges at the water-rock interface. The hypothesis of cation exchange in the aquifer clays has been done, as it contains Montmorillonite which enables such an exchange. We have then modelled the water chemistry along on few kilometres downstream from a salt dirt heap. The 1D model is built after the existing hydrochemical numerical code KIRMAT. The aquifer rock is modelled by 1% of Montmorillonite and 99% of inert rock. KIRMAT deals with clays as solid solutions, in the present case with a Na- pole and a Ca-pole. Through the history pollution modelling over approximately hundred years, the calculated values show a good agreement with measurements relating to the spatialized chloride concentrations, pH, sodium and calcium concentrations. These results validate the cation exchange hypothesis: they enhance our understanding of the aquifer system submitted to a saline pollution; they also show the interest of the coupled hydrogeochemical approach for natural systems.
H51B-0459
Fate of 3-tert-Butyl-4-hydroxyanisole, 1,3,4,6,7,8-hexahydro-4,6,6,7,8,8- hexamethylcyclopenta(g)-2-benzopyrane and chlorpyrifos in a Conventional Wastewater Treatement Plant
Emerging contaminants (ECs) are a major concern in the environment, particularly those found in waters. Wastewater treatment plants (WWTPs) play a key role in reducing the concentrations in the environment because compounds may be transformed under either aerobic or anaerobic conditions or may sorb to wastewater sludges and therefore be removed from waters. If these ECs are not contained or treated then effluent discharged from the WWTP and to a receiving stream may contain hazardous levels of these contaminants. Reported here is a study of the fate of three emerging contaminants (ECs): 3-tert-Butyl-4-hydroxyanisole (BHA), 1,3,4,6,7,8-hexahydro-4,6,6,7,8,8-hexamethylcyclopenta(g)-2-benzopyrane (HHCB) and chlorpyrifos. Experiments were conducted on a laboratory scale by emulating conditions of a conventional WWTP in San Antonio, TX. The goal of the research was to determine general characteristics for both sorption (to wastewater sludges) and degradation. The sorption experiments were performed by exposing the sludge to a variety of initial concentration of ECs for 24 hours. After exposure these three ECs were extracted and analyzed using gas chromatography followed by flame ionization detector (GC/FID). Sorption experiments indicated that HHCB and chlorpyrifos are more hydrophobic than BHA and, therefore, would be mostly contained in the sludges. The degradation rates for these ECs were also considered for both aerobic and anaerobic conditions using different bench-scale reactor setups for 21 days. The differences between the reactor setups included volume of reactor, amount of sludge, mode of supply of nutrients and acclimatization of sludge to the ECs. One sludge was first acclimated to EC concentrations and then used in the experiment. The acclimated reactor had reaction rate constants approximately double that of the non-acclimated sludge reactor setups and followed first order reaction kinetics. Aerobic degradation occurred more readily for all three compounds than anaerobic degradation. These experiments supported the hypothesis that the WWTPs do capture and transform most of these compounds and, therefore, limit their reach to the effluent. However it cannot be supported that the compounds in the sludge phase are degraded to very low concentrations. Because of the changing dynamics of the sludge phase with time, further work needs to be conducted on the influence of time on sorption coefficients and, subsequently the effect of these temporal changes on degradation of these compounds.
H51B-0460
Dissolved Gases as Indicators for Stream-Ground Water Interactions
The connection between groundwater and surface water varies along stream corridors, but these hydrologic changes are typically difficult to observe or measure. Many dissolved gases entering streams via groundwater discharge are either undersaturated or supersaturated with respect to atmospheric equilibrium due to physical or biological mechanisms. Because such gases behave non-conservatively (e.g., via losses to the atmosphere) within the stream channel, their longitudinal patterns can potentially help identify where groundwater enters or exits a stream system. Such information can be very useful for understanding stream water quality and the impacts of land management. Unfortunately, dissolved gases (other than oxygen) have not been frequently employed in studies of stream systems, and their full potential as hydrologic tools has not been established. A better understanding of how dissolved gases can be used to study the groundwater/surface water connection is needed. In this study we present and interpret longitudinal patterns of several gases along an 8 km stretch of a baseflow dominated stream located in a predominantly agricultural sand plain watershed of central Wisconsin. Dissolved gas measurements included oxygen, carbon dioxide, methane, nitrous oxide, chlorofluorocarbons, and noble gases. Major and minor ions were also measured. Sampling locations were sited at 350-m intervals along the thalweg of the stream into headwater tributaries. Losing stream sections had CFCs, nitrous oxide, and methane concentrations near atmospheric equilibrium. Gaining stream sections were supersaturated with nitrous oxide, methane, and carbon dioxide and undersaturated with CFCs and oxygen. High concentrations of nitrous oxide accompanied nitrate entering the stream.
H51B-0461
Linking Atmospheric Deposition to Air Mass Chemistry at a Coastal Rural Site
Atmospheric deposition often provides a large part of the total nitrogen and organic matter entering surface waters, but the relationship between deposition and air mass chemistry is not well understood for many constituents. Wet deposition (WD) samples were collected at the Thompson Farm atmospheric observatory in coastal New Hampshire in conjunction with the AIRMAP program from November 2003 to January 2007. Samples were analyzed for DOC, TDN, DON, NO3, NH4, PO4, Cl, SO4, Oxalate, Na, K, Mg, Ca and SiO2. DOC and Cl were the dominant constituents in wet deposition and inorganic nitrogen species dominated wet N deposition. Constituents in wet deposition were compared to various metrics of average daily atmospheric chemistry (AC) occurring on the day of the wet deposition event using canonical correlation analysis (CCA) to infer sources of wet deposition. Atmospheric chemistry metrics included continuous measures of air quality, aerosols and various volatile organic compounds (VOCs). Three WD canonical variates (CVs) were significantly related (p<0.05) to three AC CVs and together could explain 62% of the variation in WD constituents. The AC CV loaded with VOCs mostly of biogenic origin explained 20.4% of the variation in the first WD CV loaded with DOC, TDN and NH4. The AC CV loaded with parameters representing urban or 2° processed air explained 30.8% of the variation in the second WD CV loaded with TDN, NH4, NO3 and SO4. The AC CV representing a mixture of ocean, urban and biogenic sources explained 11.0% of the variation in the third WD CV loaded with Na and Cl. Our results suggest that interaction with urban/processed air masses drives temporal variation in wet deposition of most solutes, but DOC deposition is driven more by biogenic sources.
H51B-0462
Ground Water, Surface Water and Land Interactions for Soluble Reactive Phosphorus and Nitrate at a Dairy Farm in a Catskill Mountains' Valley
Surface waters in many areas of the Northeastern United States are characterized by high phosphorus and low nitrate concentrations. Two best management practices (BMPs), fencing cattle path and stream cattle crossing, were implemented to remove or to limit production of pollutants from non-field areas. This research examines the potential of soluble phosphorus and nitrate contributions to stream waters on a valley dairy farm in the Cannonsville basin of the New York City reservoir system. Soluble reactive phosphorus (SRP), nitrate (NO3--N), dissolved organic carbon (DOC), and dissolved oxygen (DO) concentrations were measured at regular intervals over a 3 yr period, and analyzed via a mixed model statistical procedure to determine the cause of the observed trends in N and P levels. In addition, the effectiveness of the BMPs to improve the water quality in the streams was investigated. SRP concentrations in stream water were surprisingly low with concentrations between 0.001 and 0.100 mg L-1 but with peaks related to the time prior to the implementation of the stream cattle crossing. The effectiveness of the stream cattle crossing was determined in a 30 percent decrease for SRP concentrations in stream water. The highest nitrate and SRP concentrations were observed during the summer, and were influenced by the stream bottom remove for P and denitrification for N but not by inputs from groundwater. Results of the mixed model analysis highlighted the importance of rainfall, stream cattle crossing implementation and DOC in NO3--N and SRP availability in stream flow. These results demonstrate the importance of identifying processes that describe how pollutants move in the environment, which provides useful information for targeted water quality management.
H51B-0463
Processes Controlling Stream Flow Chemistry in Semiarid, Forested Catchments, Valles Caldera, New Mexico
Using mixing models and point and spatially distributed snow data, controls of stream flow chemistry from headwaters to higher order streams at the East Fork of the Jemez River were identified. The East Fork of the Jemez River, located in Valles Caldera in New Mexico, drains a total area of 1400 km2 and is primarily characterized by highly fractured tuff. Chemical data were collected from 2005 to 2007 from tributaries of the East Fork of Jemez River. Remotely sensed snow-covered area (SCA) data from MODIS were also used to determine snowmelt timing, estimate snowmelt quantity and help understand stream flow generation in these ungaged catchments. A new modeling procedure was developed to identify conservative chemical tracers and end-members contributing to stream flow using diagnostic tools of mixing models and end-member mixing analysis. Results indicate that stream flow chemistry is primarily controlled by mixing of shallow subsurface flow and groundwater (overland flow and in-stream chemical reactions are not important). From smaller to larger catchments, the number of end-members does not change, but chemical compositions of those end-members change with catchment size, slope and snow water equivalent. This new modeling tool set may be used elsewhere to examine processes controlling stream flow chemistry and the changes of stream flow chemistry with catchment characteristics.
H51B-0464
Trends and Sources of Low Stream Flow in the Merced River, Sierra Nevada, California
Evaluation of Upper Merced River low stream flow (streamflow from August to October) trends shows mean flows have declined significantly since 1984. For two water years, 2006 and 2007, stable isotopes and specific conductance were used to determine primary sources of low flow. These are two years with significantly different snowpacks. The Merced River Basin snow water equivalent (SWE) on April 1, 2007 was 45% of the historical April 1 average (based on monthly snow course data), while the April 1, 2006 was 124% of the April 1 average. For 2006, it has been determined that the primary sources of low flow are mountain-block recharge, lateral subsurface flow and overland flow. The mean contribution of mountain-block recharge to low flow was greater than 25% of total streamflow. Overland flow accounted for less than 30% and was primarily derived from higher elevations (>2,800 m). The contribution of lateral subsurface flow and overland flow decreased over time and responded to the timing of snowmelt and snow water equivalent in spring. These data were fitted with an exponential function to determine time response parameters. The response of lateral subsurface flow to snowmelt lagged two months behind the peak snowmelt, indicating that the mean travel time was about two months. Lateral subsurface flow appears to be more sensitive to the changes in snowmelt timing at higher elevations than lower elevations. In contrast, in 2007, overland flow contributions are significantly less and that the response of lateral subsurface flow to snowmelt was significantly shorter. These changes are attributed to the difference in snowpack distribution, with much less volume of snow at lower (<1,800 m) elevations than for 2006.
H51B-0465
Net Organic Carbon Export From Two Temperate Mesotrophic Lakes With Contrasting Hydrologic Characteristics
Lakes are important to the transport, transformation, and retention of organic and inorganic carbon. Recent evidence strongly suggests that all but the most eutrophic lakes are net consumers of organic carbon (OC) due to inputs from the surrounding watershed and subsequent degradation within these lakes. We constructed a whole-lake carbon budget to test the relative importance of allochthonous carbon sources in two mesotrophic lakes with contrasting hydrologic characteristics; an open-basin lake which receives most of its water as stream input, and a closed-basin lake which receives water only as groundwater and precipitation. We also sought to determine the influence of allochthonous carbon on whole-lake carbon budgets. As expected, the load of allochthonous carbon was much greater in the open-basin lake (910 g C m-2 yr-1) than the closed- basin lake (85 g C m-2 yr-1) and was dominated by inorganic carbon (IC). Contrary to the findings of recent studies, both lakes were net exporters of OC despite the high allochthonous carbon loads and net flux of CO2 to the atmosphere. Gross primary production was sufficient to account for the carbon dioxide flux and the conversion of IC to OC resulting in the net export of OC. We believe that the carbon budget of these lakes is largely explained by their geological setting which strongly favors IC inputs. IC inputs can contribute to atmospheric CO2 flux and encourage macrophyte growth. The importance of the processes identified in this study to other lakes will depend on geologic setting.
H51B-0466
Modeling the fate and transport of saltwater discharged into a well during a tsunami event
The 2004 Asian tsunami caused considerable contamination of groundwater resources in Sri Lanka. Open wells are widely used in the coastal areas of Sri Lanka for accessing potable water and sea water inundation through these open wells was potentially a major source of groundwater contamination. Various organizations tried to remediate the contamination in these wells through pumping. However, these efforts were ill-coordinated and in most cases the pumping was done without any technical information or scientific basis. There were no guidelines available for pumping wells after a saltwater event at that time. Therefore, there is a strong need for understanding the saltwater migration processes in order to develop a set of guidelines for well cleanup. Our project, funded by international agencies was jointly conducted by a multi-disciplinary team of international scientists. We conducted field and laboratory experiments by simulating tsunami-type inundation events in wells. The field experiments were conducted at a pristine location, unaffected by the tsunami, on the west coast of Sri Lanka. Field experiments are hard to analyze without a supporting investigation, therefore we performed laboratory experiments. Since all real world scenarios cannot be modeled through physical experiments due to resource (time, money and manpower) constraints, well calibrated numerical models are often used to simulate various different cases. The widely used numerical code, SEAWAT, was used to numerically simulate the laboratory experiments and to develop a well-calibrated numerical model. The numerical model was further used to perform a scenario analysis by varying the hydraulic parameters. In the presentation we will discuss the results of the investigations conducted by the team based in the USA that assisted in the development of physical and numerical experiments. In particular, we will present the effect of varying hydraulic parameters on the fate and transport of saltwater discharged into a well.
H51B-0467
Seasonal Fluxes and Cycling of Trace Metals in Semi-Arid Fluvial Systems: Leichhardt River, Queensland, Australia
This paper examines the storage and transfer of trace metal contaminants in water and sediment within the upper Leichhardt River Catchment (1,113 km2), Mount Isa, north-west Queensland. The Leichhardt River runs adjacent to Mount Isa City and the Cu and Pb-Zn-Ag Mount Isa Mine and smelter (MIM) and feeds Lake Moondarra, Mount Isa's potable water supply. The river flows only during the monsoonal wet season (December- March) and for the remainder of the year is characterised by a series of disconnected temporary and permanent pools ranging in length from 10 m to 1 km. These pools are significant because they act as storage zones for water-soluble and sediment-associated metals and serve as refugia for native and domestic fauna during protracted intervals between wet season flows. To recognise seasonal fluxes and cycling patterns of trace metal contaminants in the Leichhardt River system this study investigates the physico-chemical water quality of the wet season flows and the subsequent seasonal variations in the dry season pool water. In January 2007 two floods were studied using sixteen rising stage water quality samplers along the Leichhardt River. The samplers were placed above and below MIM, and within selected tributaries draining MIM to ascertain the specific impacts from mining activities on water quality. Grab samples were also collected during the floods and on the falling stages of flow within the river system. Following this, dry season water quality sampling commenced on eleven remnant pools over a period of 8 months. Overall 60 wet season and 34 dry season water samples were collected and analysed for physico-chemical (pH, EC, DO, TDS, SS) variables in the field and total and water soluble cations, trace elements of concern (Cd, Cu, Pb, Zn) and anions via ICP-MS and ion chromatography, respectively. In addition, mineralogical and geochemical analysis was undertaken on 34 bottom sediment samples collected from the pools. Analysis of the temporal metal fluxes revealed two tributaries draining the MIM lease recorded the highest total (King Gully: Cd, 30, Cu, 3600, Pb, 3600, Zn, 4900 ug/L) and water soluble trace metal (Death Adder Creek: Cd, 17, Cu, 780, Pb, 61, Zn, 1500 ug/L) concentrations during the wet season flows. Concentrations were highest at the onset of the floods and although values decreased during the rising limb of the hydrograph, total and water soluble contaminants remained elevated with respect to Australian Government Guidelines and pose a potential environmental toxicology risk. Monitoring of the dry season pools commenced in February 2007 and showed highly variable water soluble trace metal concentrations ranging from below instrument detection to 140, 12, 12 and 7 ug/L for Zn, Pb, Cu and Cd, respectively. The highest concentrations were recorded towards the end of the dry season and within the pools adjacent to and downstream of the MIM lease. The results indicate that metal contaminants are predominately particulate bound during wet season flow and are removed from suspension upon capture and storage in Lake Moondarra and channel pools. The pool waters became more concentrated with soluble metal contaminants over the dry season and were controlled by evaporation and reduced pools size. Overall, sediment and water quality in the Leichhardt River and tributaries draining the MIM lease is seriously impaired with respect to Australian Government Guidelines. However, while it is clear that a potential environmental toxicology risk exists there remains an absence of ecotoxicological data examining the effects of metal contaminants on the biotic occupants of the system.