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…
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Over the last few decades, new technologies in the form of observational satellites, measurement instruments, and model simulations have enabled the scientific community to make substantial strides to understand the drivers, mechanics, and impacts of climate change. This dissert…
Reactive iron mineral coatings in redox transition zones play an important role in contaminant attenuation. These mineral coatings include poorly crystalline to crystalline iron sulfides, carbonates, and oxyhydroxides, and are a signature of the biogeochemical processes occurrin…
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…
Understanding the temporal and depth-related spatial controls on microbial functional redundancy and community interactions remains a central issue in microbial ecology and Critical Zone science. Microorganisms are influenced by and influence biogeochemical reactions in the soil…
Northern peatlands have accumulated approximately one third of all soil carbon (C) and therefore play an important role in the global C cycle. Besides the C sink function, peatlands are one of the largest biological sources of atmospheric methane (CH4) and represent approximatel…
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 …
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…
The accuracy of past climate estimates utilizing planktonic foraminifera is limited by our knowledge of their habitats, which determine the stable isotopic (\delta¹⁸O, \delta¹³C) signals carried by their tests. This study refines habitat estimates of the species Globigerinoides …
Surface horizon samples from two Vertisols, an Andisol, and an Alfisol were collected from farmers' fields, research station farms, and uncultivated/non-fertilized areas to characterize the organic and inorganic forms of P, to describe the equilibrium P sorption-desorption chara…
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 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…
Analyses of concentration, and absorption and fluorescence spectroscopy of the dissolved organic carbon were performed on waters collected during cruises to the West Florida Shelf (WFS), eastern Caribbean, and the Arabian Sea. The cruise to the WFS was designed to measure the ef…
The goal of this research is to understand how and why tree diversity changes during 200 years of shifting cultivation in a tropical rainforest. To determine the relative importance of dispersal and nutrient limitation to tree diversity, I collected data on changes in the struct…
A mooring time series of physical and bio-optical variables and complimentary data were collected during the Arabian Sea Process Study in 1994-1995. The mooring data-set was collected continuously for one year. This allowed observation of two mixed layer (ML) deepening events, d…
Changes in carbon dioxide concentration and/or ocean circulation are generally invoked to explain both equable early Miocene climates and subsequent rapid East Antarctic ice sheet (EAIS) expansion in the middle Miocene. However, pCO\sb2 trends and absolute magnitudes must be inf…
I have developed a computer model, called GEOMOD, to simulate land use change and its consequences on biotic carbon exchanges between terrestrial ecosystems and the atmosphere, using a spatial modeling approach. Land use change is a most important part of the anthropogenic distu…
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…