GS23B-01
The Physical Effects of an Intraaggregate Structure on Soil Shrinkage
Clay and soil containing it have shrinkage curves that are qualitatively different in shape. These differences and their origin require a scientific explanation based on an intraaggregate soil structure. The current models are based on the approximation of an experimental shrinkage curve by some a priori taken mathematical expression and do not explain the above differences. The objective of this work is to show how a clay shrinkage curve turns into a soil shrinkage curve. Because of the crack volume the measured shrinkage curve is not the single-valued feature of a soil. We introduce a new concept of the reference shrinkage curve that is only stipulated by soil shrinkage without cracking, single-valued, and qualitatively similar to an observed shrinkage curve. We also introduce new concepts of an intraaggregate soil structure: (i) a rigid superficial layer of aggregates that loses water during shrinkage; and (ii) lacunar pores (micro-cracks) inside an intraaggregate clay that change in volume during shrinkage. Then, through a series of consecutive steps we transit from a clay shrinkage curve to a soil shrinkage curve with experimentally observed qualitative features. Thereby we demonstrate the qualitative physical impact of the intraaggregate structure on soil shrinkage. The physical understanding of the transformation of the clay shrinkage curve to the soil shrinkage curve and of the new features of the intraaggregate structure underlying this transformation, are essential for numerous applications; first of all, for the physical modeling of soil shrinkage, water retention, hydraulic conductivity, water flow, and solute transport. In addition, the concepts and results of the model can also be useful for the physical explanation of crack contribution into a measured shrinkage curve, the hysteretic shrinkage-swelling phenomenon, the effects of compaction and consolidation on soil shrinkage-swelling in the field, the effects of the non-total closing shrinkage cracks at soil wetting in field conditions, and soil crusting.
GS23B-02
HYDROGEOCHEMICAL CHARACTERIZATION OF FORMATION WATERS IN CRETACEOUS ROCKS FROM SOUTHEAST MEXICO
Formation waters were sampled from ten different producing wells in several Cretaceous oil fields in central and north Tabasco, southeast of Mexico. All of them were analyzed for mayor and trace ions, as well as for 18O and D isotopes. The salinity in the central oil fields (TSD in ppm) ranges from 221,972 ppm to 243,372 ppm. The salinities are very similar in different oil wells. These salinities are 1 to 14 times higher than the salinity found in another fields (15,299 to 16,557 ppm), and 1 to 5 times higher than other field. A northern oil field salinity is characterized also by an important heterogeneity of it salinity due to salt intrusion and interaction with non uniform structures. The major ions analysis (Na+, Ca2+, K+, Mg+, Cl+, SO42-, HCO3-) suggests water-rock interactions in all the oil fields. This is the case, particularly marked in the central fields, where the brines are enriched in Mg in a range from 10 to 274 ppm. This is due to brines/dolomites interaction, while in other oil field, the higher concentration of Mg was only of 1.17 ppm. The central oil fields present depletion on sulfate concentrations (<5.9 ppm). This could be due to precipitation of metal sulfide (thermal reduction) in the form of pyrite and marcasite. Halogens (Br, Cl) concentration indicates three different origins for the formation waters. Water from the central wells is plotted on the evaporated marine water evolution line. Water from the southern wells is located close to marine water in the halite dissolution zone, whereas water form the northern wells is plotted in the diluted waters zone. Cl and Br evolution in the central field samples shows two different groups, and clearly reveal mixing processes between marine water and highly evolved evaporated seawater. Whereas water from the northern wells is plotted in the mixing zone between seawater with low salinity water trapped in Tertiary sediments which can migrate until mixed with older formation waters. The D-O stable isotopes results show some differences between the southern water and other waters. The 18O values were range between +8.37 to +12.28 for all waters, not showing strong differences between them. Whereas the D content was higher for southern wells (-0.83 °) than for other waters (range: -21 to -13°), which very likely indicates an isotopic composition of evaporated water in equilibrium with the host rock (carbonate cement).
GS23B-03
NATURAL RADIATION FOR IDENTIFICATION AND EVALUATION OF RISK ZONES FOR AFFECTATION OF ACTIVATED FAULTS IN AQUIFER OVEREXPLOITED.
In basins as Mexico, Michoacán, Guanajuato, Queretaro, Aguascalientes and San Luis Potosi, the existence of
faults and fractures have affected the urban infrastructure, lines of conduction of drinkable water, pipelines, etc.,
that when not being identified and considered, they don't reflect the real impact that these cause also to the
aquifer system, modifying the permeability of the means and in occasions they work as preferential conduits that
communicate hydraulically potentially to the aquifer with substances pollutants (metals, fertilizers, hydrocarbons,
waste waters, etc.) located in the surface.
In the Valley of San Luis Potosi, Villa of Reyes, Arista, Ahualulco and recently The Huizache-Matehuala is being
strongly affected by faulting and supposedly due cracking to subsidence, however, the regional tectonic could
also be the origin of this phenomenon. To know the origin of the faults and affectation to the vulnerability of the
aquifer few works they have been carried out in the area. A preliminary analysis indicates that it is possible that a
tectonic component is affecting the area and that the vulnerability of the aquifer in that area you this increasing.
Before such a situation, it is necessary to carry out the isotopic study of the same one, for this way to know among
other things, isotopic characterization, recharge places and addresses of flow of the groundwater; quality of
waters and the behavior hydrochemistry with relationship to the faults.
High radon values were measured in San Luis Potosi Valley, the natural source of radon could be the riolites and
however, these are located to almost a once thousand meters deep for what the migration of the gas is not very
probable. The anomalies radiometrics was not correlation with the faults in this case.
In some areas like the Valley of Celaya, the origin of the structures and the tectonic activity in the area was
confirmed, identifying the structural arrangement of the faulting, the space relationships of the fault trend and
evolution and elevation of the piezometric level in the aquifer, detecting high values of Radon-222, anomalies of
radiation gamma and the presence of grooves in the basalts. Anomalies of radiation gamma were detected in the
shears area. The profile of the anomalies of radiation gamma evidences and it confirms the high fracturing grade
and permeability in the shears area.
http:www.ipicyt.edu.mx
GS23B-04
Visible-Near Infra Red Spectroscopic Analysis of Black Peaks & Javalina Paleosols
Paleosols from the Black Peaks formation (65-60 ma) and from the Javalina formation (70-65 ma) were sampled adjacent to the Big Bend National Park in Brewster county, Texas. They were examined for visible and near- infrared (0.4 - 2.2 µm) spectroscopic signatures using an Ocean Optics USB2000/NIR spectrometer. We discuss the mineral composition of the soils from the measured spectral signatures, and the influence of a laccolith intrusion at about 35 ma on mineral composition.
GS23B-05
Improving Geological Map of Soil Covered Area in Yogyakarta Region by Using FTIR and ASTER Image, Response to 2006 Earthquake
Yogyakarta region is located in the southeastern part of Central Java, Indonesia, that mostly covered by product of Quaternary deposits of Merapi volcano and was entirely mapped as single geologic unit (i.e. the Young Volcanic Deposits of Merapi Volcano). This simplicity will be affected for making detail hazard map regarding to last divesting earthquake. The problem for tropical region with highly weathered is make soil covered almost the entire surface and difficult to distinguish kinds of parent/ origin rock. However the research on soil in relation to the spread of lithology in this region is rarely conducted. Geologists are challenged to improve the existing geological map by using the recent data and methods especially in soil covered area in this case by using FTIR and ASTER image. At least 50 samples of various rocks and soils were taken for FTIR which is combining with ASTER Image to create new border of geological units for improving Geological Map especially on Quaternary unit. Soil distribution related to parent rock can be recognize such as Tertiary units of tuffaceous limestone of Sentolo Fm, volcanic breccia of Nglanggran Fm, diorite from Godean and Gendol, more detailed of Quaternary Merapi's sediments and new unit as black clay from Gantiwarno which all have different physical properties. Each soils distribution and border is delineated by using satellite image from ASTER. Hopefully this research will be able to support other research which is need more accurate sedimentary unit border in Yogyakarta region.
GS23B-06
Germination and Seedling Growth of Perennial Ryegrass in Acid Sulfate Soil Treated by Pyrite Nano-Encapsulation
The trial pot experiment was conducted to validate the effect of encapsulation in reduction of acid rock drainage. Six different treatments were performed: A = control, four times spraying of distilled water; B = four times of 0.01 M H2O2; C = once-encapsulated and three times spraying of distilled water; D = twice-encapsulated and twice spraying of distilled water; E = three times-encapsulated and once spraying of distilled water and F = four times-encapsulated for the acid sulfate soil with pyrite bearing andesite powder and sand. After the encapsulation treatment, the perennial ryegrass (Loium perenne) was sowed to evaluate germination rate and growth for three months. The leachate was examined for the chemical properties. The leachate from the A pot (control) is characterized as acidic (pH below 3) and high concentrations of SO4-2: 12,022 mg/L, Al: 85.8 mg/L and Mn: 34.1 mg/L which can be toxic effect to the plant growth. However, the leachate from encapsulated pots showed near neutral (pH 6 to 7) and low concentrations of SO4-2 (below 3,000 mg/L), Al (below 45mg/L) and Mn (24 gm/L). The frequency of encapsulation treatment is related to reduction of acidic drainage. It was hard to identify the significant difference of the seed germination rate of ryegrass between the treatments, although root and shoot growth showed three times difference between the control (1.90g/pot) and four times encapsulated treatment (6.33g/pot) after 2 month growth. It is suggested that encapsulation of pyrite in acid sulfate soil causes the reduction of acidic drainage resulting in the higher growth of herbaceous plants.
GS23B-07
Leached Metals in Surface Sediments in the Southern Gulf of Mexico
Surface sediment samples have been collected a board of R/V "Justo Sierra" in the Gulf of Mexico from 1996 to 2005. Leached metals Ba, Cd, Cu, Ni, and V were analyzed in order to establish their distribution at three levels of surface sediments (0-1, 4-5, 8-10 cm depth), and to document their spatial distribution in the study area. Statistical treatments, linear and Spearman correlation and principal components analysis were applied to the data. Results show that the barium average concentration was 667 ìg/kg during 1998. During subsequent years, this average value decreased, but in 2005 the value increased four times respect to 1998 levels (>2,800 μg/kg). Cadmium average concentrations were relatively high between 1998 and 2001, afterwards low concentrations were observed (<45 ìg/kg). Leached copper average concentrations decreased consistently through the years. But an increase in the two first sedimentary levels ranged between 4.4 -15,540 μg/kg was observed in 2005. Leached nickel had fairly low concentrations between 1998 to 2004, but an increase in the three levels were observed in 2005, and later on, its average concentration reached 186 μg/kg, similar to 2005 values. Leached vanadium concentrations were variable through the years, with high values observed in 2006 (235 μg/kg). Metal concentration values mapped with respect to sampling sites permit to investigate on the spatial and temporal distributions, establishing a micro-zonification in the study area.
GS23B-08
Age and Variability of Riverine Dissolved Organic Carbon in the St. Lawrence River
Riverine export of dissolved organic carbon (DOC) to the global ocean represents about 0.25 x 10E15gC/yr.Various studies have shown that this DOC mainly derives from terrestrial organic matter (OM). It is generally considered to be refractory and transported conservatively to the ocean. However, recent work has shown that many rivers carry a high-14C content DOC. Knowledge of the age (residence time) of both labile/refractory components of DOC and of its variability is essential for a robust assessment of riverine DOC role in the global carbon budget. Here, we report chemical and isotopic composition of DOC from the St. Lawrence River, with a focus on 14C ages of labile vs. total fractions, and on the spatial, seasonal to interannual variability of DOC-export. Alkaline CuO oxidation was used to collect refractory fractions of DOC and to identify sources and degradation stages of terrestrial organic matter. Our results indicate some variability in total DOC from year to year, but more notably, in temporal and spatial variability of 14C-activities of refractory components, which represent approximately 5 to 15% of total DOC and yielded 14C-activities ranging between 75 and 96% of modern carbon (pMC). From these values, 14C-activities of labile compound were estimated. They range from 100 to 111pMC. It is concluded that labile DOC compounds have a very young age/short residence time. This residence time is much shorter than the one estimated for water in the Great Lakes/St. Lawrence River system, thus suggesting prominent terrestrial sources for this reactive organic carbon. Although representing lesser overall fluxes, refractory material display ages pointing towards their previous significant residence time in soils.
GS23B-09
Stable Carbon Isotope Characterization of CO2 Loss in Acid Mine Drainage Impacted Stream Water: Observations from a Laboratory Experiment
Water from an acid mine drainage spring, ground water from a mine tailings pile, stream water and tap water were acidified to simulate acid mine drainage (AMD) contamination. The objective was to determine how acidification of stream water by AMD affected DIC loss and carbon isotope fraction. Two 20 L HDP containers (reactors) containing samples from each source were left un-acidified and allowed to evolve under ambient conditions for several weeks in the laboratory and two others were acidified. Acidification was carried out progressively with sulfuric acid to pH <3. For acidified samples, one reactor was acidified open to the atmosphere and the other closed from contact with atmosphere and CO2(g) was collected under vacuum. The un-acidified samples did not show significant alkalinity and DIC loss, and the 13C of DIC was enriched with time. The acidified samples showed decrease in alkalinity and DIC and increase in the 13C of DIC and CO2(g) with progressive acidification. The enrichment of 13C of DIC for un-acidified samples was due to exchange with atmospheric CO2. On the other hand, the 13C enrichment in the acidified samples was due to fractionation during dehydration of HCO3- and diffusive loss of CO2(g) from the aqueous phase. The actual values measured depended on the amount of CO2 lost from the aqueous phase during acidification. Samples with greater CO2 loss (closed acidification) had greater 13C enrichment. Beyond the HCO3- titration end point, the δ13C of DIC and CO2(g) was similar and nearly constant. The result of this study suggests that AMD effects on DIC can be modeled as a first order kinetic reaction and the isotope enrichment modeled using Rayleigh distillation.
GS23B-10
Helium and Argon Everywhere in the Earth's Crust
Noble gas abundances and isotopic ratios in minerals and rocks are used in many fields of the Earth Sciences. Besides primordial abundance in the solar system, radiogenic 4He and 40Ar are found in minerals that contain their parent elements, principally K, U, Th and Sm. It is generally supposed that He and Ar are generated and stored in a reduced set of minerals. A systematic study of about 40 common minerals, not investigated previously for radiogenic nobles gases, shows that most contain significant amounts of helium and argon and therefore are potential candidates for noble gas transport and storage. We measured 4He and 40Ar concentrations and 40Ar/36Ar ratios and found that every studied mineral contains measurable He and/or Ar. Argon ratios are variable, from almost 100% radiogenic to entirely atmospheric, but for most minerals a radiogenic component can be measured. At the present stage of the study, we have not yet measured the parent concentrations for age determination, so the role of excess argon is unknown. Nevertheless, with the advent of high reproducibility multicollector noble gas mass spectrometers, the dating of many minerals not considered previously for geochronology will be probably feasible, and direct dating of diverse ore deposits, sedimentary sequences, etc. will become a reality.