Chromium contamination of groundwater and soils continues to pose a major environmental concern. Soils may have become contaminated with chromium through former industrial activities geochemical enrichment. The nature of the industrial activity will determine the form and concentration of the chromium as well as the presence of co-contaminants and the pH and redox of the soil. Chemical reductants have been widely used for the transformation of hexavalent chromium in the environment. Over recent decades attention focused on the chemical reductant calcium polysulphide which has performed effectively in the treatment of groundwater and soil samples contaminated with Cr(VI). Yet a detailed understanding of calcium polysulphide (CaSx) performance has not yet been established. Hexavalent chromium concentrations in aqueous and groundwater samples were significantly reduced by calcium polysulphide and CaSx:chromate molar ratio of 1.5 was sufficient to prevent partitioning of Cr(VI) into solution and to precipitate the solution phase. Calcium polysulphide was used for the remediation of solid chromite ore processing residue (COPR) samples. Prior to the application of calcium polysulphide to COPR, each of the key steps were optimized. A range-finding experiment was conducted to understand the dosage and treatment regime at which Cr(VI) immobilization within COPR was optimal. The results indicated that unsaturated deployment of CaSx into the medium outperformed that in saturated systems. A higher polysulphide amendment dose of 5% w/v concentration enhanced the final treatment of Cr(VI) within COPR. The toxicity and carcinogenicity of Cr(VI) over Cr(III) requires a technique capable of discriminating between valencies. The EPA Method 7196A specifically quantifies the concentrations of Cr(VI) in environmental samples and was used for all analysis to differentiate between Cr(VI) and Cr(III). Cr(III) was calculated as the difference between the Cr(VI) and Cr-total concentrations. In addition to the EPA 7196A, a novel ion exchange resin (IER) procedure was developed to differentiate the two species of chromium. After optimisation, Amberlite resins IRA 400 and IR-120 were used for the specific sorption and subsequent analysis of aqueous Cr(VI) and Cr(III) solutions. For the selective removal of chromate from groundwater, waste water and soil samples, Amberlite IRA 400 achieved a consistent performance of >97% removal in a range of trials. The IERs in this work were applied as analytical tools however they could be applied as remediation tools. While aqueous treatment of chromium contaminated media using CaSx was very successful, COPR treatment proved to be difficult due to the complex nature of the system. An understanding of stoichiometric responses to CaSX has been established, but the nuances of soil physicochemical interactions require more thorough investigation.

Over the last decades, arsenic (As) contamination of soil-plant-water systems has become a major concern for Bangladesh and West Bengal, India. The geochemistry of the sediment depositional environment which subsequently, on sediment burial, give rise to elevated As in Holocene groundwater’s of Southeast Asia, may provide clues to unravelling the mechanistic basis and spatial heterogeneity of this phenomenon. The Sundarbans mangrove ecosystem, Bangladesh, is a modern analogue, and indeed forms a continuum with, the Holocene sediments of concern and thus studying As cycling in surface Sundarbans sediments. Similarly, rice paddy fields in many regions of the Bengal Basin form a continuum with Holocene sediments. Sediment cores were collected from a wide range of locations within the Sundarbans to study surface spatial, as well as down the profile (~1 m), As distribution and it’s association with other geochemical parameters. Pore and surface water, and Diffusive Gradients in Thin films (DGT) were sampled from 4 different interlocked sub-habitats over 0.29 km2: major river bank, main tributary, forest floor and minor tributary. Further experiments were conducted to observe As dynamics in mangrove surface sediments on application of mangrove detritus. Finally 3 interlinked experiments (field manuring, soil batch culture, greenhouse growth trials) were conducted to assess the effect of farm-yard manure (FYM) and rice straw, at a field application rate practised in Bangladesh (5 t/ha), on As mobilization in soil and subsequent assimilation by rice. As concentration in mangrove sediment down the profile was found to be more associated with elevated Fe and Mn than with organic matter (OM), with significant spatial variations among the locations. Sediment particle size was an important factor determining As retention and mobilization, which is also true for deeper Bengal Bay sediments. Proximity to mangrove vegetation and to water bodies was found to have significant effect on As dynamics. Porewaters from coarse textured, low OM riverbank sediment were high in As, but with only a small pool of As for resupply from the solid phase, showing similarities with grey aquifer sediments compared to fine textured and high OM content forest floor sediments. The As column dynamics study showed that As release into porewater was strongly associated with Fe release, indicating the strong association of the 2 elements, with OM playing a major role in their dissolution. The desorption studies also showed OM driving As mobilization within short time. Due to strong redox cycling very little evidence of As methylation was observed in biologically active mangrove porewaters. But we found 10-fold increase in dimethylarsinic acid (DMA) production compared to a non-amended control using the same sediments treated with mangrove detritus in the laboratory. OM amendments lead to considerable mobilization of As into both soil porewaters and standing surface waters in rice paddy. In a greenhouse rice cultivation experiment, flooding initially caused greatly enhanced As mobilization in porewater (< 24 d), but the effects of flooding on As mobilization decreased during later rice growth, particularly at grain fill. However, OM amendment did not cause significant As accumulation in grain and straw compared to control. It was noted in field trials and greenhouse studies that OM fertilization greatly enhanced As mobility to surface waters, which may have major implications for fate of As in paddy agronomic ecosystems.

Ph.D. / Environmental Science and Engineering / Chromate-containing precipitates can affect the mobility of toxic Cr(VI) in the subsurface, control its concentration in groundwater, limit its bioavailability, and impede remediation of chromium contaminated sites. This dissertation focuses on two iron-chromate precipitates, KFe [subscript 3](CrO4)[subscript 2](OH)[subscript 6] (the chromate analog of the sulfate mineral jarosite) and KFe(CrO4)[subscript 2].2H2O, that we identified in a soil contaminated by chrome plating solutions. The precipitates were identified using scanning and transmission electron microscopy, as well as powder x-ray diffraction. KFe[subscript 3](CrO4)[subscript 2](OH)[subscript 6] occurs as small (2-5 um) crystals interspersed within the bulk soil. KFe(CrO4)[subscript 2].2H2O forms crusts of larger crystals (10-50 um) in cracks and fractures of the soil. / Due to highly mathematical nature of the abstract, only the first paragraph is shown.

Thesis (Ph. D.) in Food and Nutrition Sciences--University of Maine, 2002. / Includes vita. Includes bibliographical references (leaves 93-98).

Thesis (M.S.)--Auburn University, 2007. / Abstract. Vita. "This thesis has produced the following three journal publications: 1) V. Srinivasan, T.P. Clement, and K.K. Lee. "Domenico solution -- Is it valid?", Ground Water, 25(2): 136-146, May 2007 ; 2) V. Srinivasan and T.P. Clement. "Analytical solutions for sequentially coupled reactive transport problems. Part I: Mathematical derivations", submitted May 2007, Advances in Water Resources ; 3) V. Srinivasan and T.P. Clement. "Analytical solutions for sequentially coupled reactive transport problems. Part II: Special cases, implementation and testing", submitted May 2007, Advances in Water Resources." -- From p. v. Includes bibliographic references (ℓ. 91-98)

Thesis (Ph. D.)--University of Texas at Austin, 1998. / Vita. Includes bibliographical references (leaves 314-329). Available also in a digital version from Dissertation Abstracts.

Thesis (Ph. D.)--Washington State University, August 2009. / Title from PDF title page (viewed on Sept. 1, 2009). "Department of Civil and Environmental Engineering." Includes bibliographical references..

Thesis (Ph. D.), Oregon Graduate Institute of Science & Technology, 1996.

Thesis (Ph. D.)--Washington State University, August 2009. / Title from PDF title page (viewed on Sept. 9, 2009). "Department of Civil and Environmental Engineering." Includes bibliographical references.

The social construction and the behavior of organization transform continuously, and the relative prices keep changing. When the relative prices changing will cause the negotiating power of the organization to change and further affects institutional evolution? "The Remedial Institution of Soil and Groundwater Pollution¡¨ had passed through successively institutional evolution during 10 years, how does the pollutant and interest group affect the institutional evolution. Through Douglass C. North¡¦s view of the institutional evolution, I collected many different Taiwanese articles of evolvement policy and rules of soil and groundwater pollution to understand the relationship between the lawmaking of "The remedial institution of soil and groundwater pollution" and the organization of behavior. Besides that, using ¡§The Remedial Fee of Soil and Groundwater Pollution," the subsidiary bill of ¡§The Remedial Institution of Soil and Groundwater Pollution" as a case study. Deeply understand the North¡¦s Theories of institutional evolution in formal rule, informal rule and enforce characteristic and their relationship. According to the analysis of the interaction between institutions and organizations, it explained that the formal rule, The Remedial Institution of Soil and Groundwater Pollution, cause it 10 years for revising. Under such structure of the institutions, the network of the administration, legislative agency and different ideology, had affected the actors who take the action regulate the transaction costs and caused new arrangement of the institution to generate stable and slow changes. It proves that our notion of the behavior of organizations exists transaction cost and has interacted effect on the construction of institutional evolution to be right, and also proves that under North's theory of institutional evolution, provided a good explanation for "The Remedial Institution of Soil and Groundwater Pollution¡¨ can't quickly revise in Taiwan¡¦s current institutions. At the same time, this statement has enhanced the explanation capability of the theories toward the environment policies of Taiwan.