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Anthropogenic addition of bioavailable nitrogen to the biosphere is increasing and terrestrial ecosystems are becoming increasingly nitrogen-saturated, causing more bioavailable nitrogen to enter groundwater and surface waters. Large-scale nitrogen budgets show that an average of about 20-25 per cent of the nitrogen added to the biosphere is exported from(More)
E xcessive nitrogen (N) concentrations, often in the form of nitrate, present a water-quality problem of growing concern. Nitrate concentrations in groundwater and rivers in developed areas of the world have risen substantially as a result of the use of synthetic N fertilizers and cultivation of N-fixing crops (Turner and Rabalais 2003). Increasing N export(More)
Nitrous oxide (N(2)O) is a potent greenhouse gas that contributes to climate change and stratospheric ozone destruction. Anthropogenic nitrogen (N) loading to river networks is a potentially important source of N(2)O via microbial denitrification that converts N to N(2)O and dinitrogen (N(2)). The fraction of denitrified N that escapes as N(2)O rather than(More)
We measured denitrification rates using a field 15 N–NO { 3 tracer-addition approach in a large, cross-site study of nitrate uptake in reference, agricultural, and suburban–urban streams. We measured denitrification rates in 49 of 72 streams studied. Uptake length due to denitrification (S Wden) ranged from 89 m to 184 km (median of 9050 m) and there were(More)
We measured uptake length of 15 NO { 3 in 72 streams in eight regions across the United States and Puerto Rico to develop quantitative predictive models on controls of NO { 3 uptake length. As part of the Lotic Intersite Nitrogen eXperiment II project, we chose nine streams in each region corresponding to natural (reference), suburban–urban, and(More)
Compared to the well-studied open water of the ''growing'' season, under-ice conditions in lakes are characterized by low and rather constant temperature, slow water movements, limited light availability, and reduced exchange with the surrounding landscape. These conditions interact with ice-cover duration to shape microbial processes in temperate lakes and(More)
Obtaining spatially separated, high-frequency water samples from rivers and lakes is critical to enhance our understanding and effective management of fresh water resources. In this paper we present an aerial water sampler and verify the system in field experiments. The aerial water sampler has the potential to vastly increase the speed and range at which(More)
n contemporary society, scientists hold a considerable degree of respect, trust, admiration, and authority. Surveys show that North American and European citizens hold a deep belief in the promise of science to solve problems, as well as to improve quality of life and the on controversial topics such as climate change, many Americans believe scientists have(More)
A ll organisms have to make a living by harnessing energy, collecting nutrients, and expelling waste. The joining together, or coupling, of elemental cycles occurs when elements required for biosynthesis are assimilated into microbial, plant, and animal biomass, and again when that biomass is decomposed; in both cases, elements cycle in proportion to their(More)
Saltwater incursion carries high concentrations of sea salts, including sulfate, which can alter anaerobic microbial processes and plant community composition of coastal freshwater marshes. We studied these phenomena in a recently restored wetland on the coastal plain of North Carolina. We measured water inundation patterns, porewater chemistry, microbial(More)