Speciation of sulfur and iron was investigated in the solid phase Black Sea sediments and high-temperature hydrothermal vent fluids of the 9°50'N East Pacific Rise and Lau Basin. Other than pyrite, solid phase sulfur in the upper Black Sea sediments existed as inorganic S(0) and…
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I examine links between catastrophic events, climate variability, and biotic modulation on evolution at the ecosystem-level of orbitally-paced Early Mesozoic Pangean great lakes. One of the largest controls on the diversity of taxa within ecosystems is mass extinction. High-reso…
This dissertation focuses on Trichodesmium spp., a N 2-fixing cyanobacterium that can alter the supply of nutrients to the ocean. For this reason, its abundance has been linked to local dynamical processes, regional elemental cycling, and global climate patterns on glacial-inter…
To evaluate the clam Amiantis umbonella as a bio-indicator of metal contamination, the concentrations of a number of metals (Hg, Cd, Pb, Cu, Ni, Mn, Cr, V, Zn, and Fe) were determined in clam's soft tissues, in different organs, water, and sediment in Kuwait Bay of the Arabian G…
Phosphorus deficiencies are limiting crop production in agricultural soils worldwide. Locally available sources of phosphate rock (PR) are being recognized for their potential role in soil fertility improvement. For applications of PR to be effective, the phosphorus must be made…
Organic and inorganic geochemical proxies from two cores in the northeastern (NE) and western Arabian Sea were employed to study orbital and suborbital climate variability of the Indian Ocean monsoons. In the NE Arabian Sea 230Th-nonnalized 232Th fluxes and authigenic uranium co…
Natural arsenic contamination of groundwater in Southeast Asia has caused the largest mass poisoning in history: nearly 100 million people routinely drink well water with hazardous arsenic concentrations. The mechanism for arsenic release to the aqueous phase, the subsequent res…
Quantifying soil nitrogen transformation processes associated with soil aggregates is noteworthy as microbial communities that are central to N cycle reside in the soil aggregate size fractions. The objectives of this research were: (1) to determine the population size of N mine…
Since the Clean Air Act Amendments of 1990, lakes in Maine and much of the Northeastern US have seen significant shifts in response to reduced atmospheric deposition as well as climate change. The organisms that inhabit lakes are susceptible to environmental change, but our unde…
Novel molecular isotope proxies measured in bivalve tissues represent a wide range of approaches for tracing ecological and climatological change through time and space. In comparison to other oceanographic data used to reconstruct modern and past biogeochemical cycles (e.g., ma…
The effect of denitrification within continental margin sediments and suboxic water columns upon the isotopic composition of dissolved nitrogen was studied with the goal of constraining the present and past global oceanic "fixed" (forms other than N\sb2) nitrogen budgets. Sedime…
Iron oxidation in the presence of lake sediment collected from an acidic alpine lake was three orders of magnitude faster than in filtered lakewater without sediment. When kinetic rates in the presence of sediment were normalized on a surface area basis, they fell within a narro…
The archaeological site of Kültepe (ancient Kanesh), located in south-central Anatolia, in the present-day Republic of Turkey, was the capital city of a native Anatolian kingdom during the early Middle Bronze Age (20th - late 18th c. BC). Uninterrupted archaeological excavations…
A pilot-scale constructed wetland treatment system (CWTS) was designed and built to produce biogeochemical conditions that promoted targeted processes for removal of arsenic from simulated groundwater. Two series were designed to promote co-precipitation and sorption of arsenic …
Arsenic contamination of drinking water sources threatens the health of over 50 million people around the world. Sustainable implementation of arsenic removal technologies requires disposal options for produced wastes that limit the release of arsenic. Arsenic contamination is p…
Increased climate variability, rising costs of chemical inputs and marginally productive soils have recently become a challenge for dryland winter wheat (Triticum aestivum L.) farmers who mainly rely on tillage management. Conventional (CT) and organic or chemical-free (CF) farm…
Cover crops improve soil aggregate stability, increase water infiltration, and legume cover crops also fix nitrogen and scavenge nutrients that are subject to leaching. Greenhouse and field experiments were conducted in Indiana to measure growth of different cover crops and thei…
L'objectif de cette etude etait de modeliser la teneur en eau et le rendement de la pomme de terre a Quebec. Pour cela, la performance des modeles SUBSTOR et SWACROP a ete evaluee pour la teneur en eau et le rendement durant deux saisons de croissance (1992 et 1993). En utilisan…
This research was designed to measure total water-soluble organic N, as well as the contribution of urea and dissolved free amino acids, in rain, aerosols, and ice cores collected from a variety of global locations. In addition to site-specific studies, a UV photo-oxidation meth…