Filters: Tags: nitrogen (X)1,434 results (77ms)
Trends in snowpack chemistry and comparison to National Atmospheric Deposition Program results for the Rocky Mountains, US, 1993?2004
Seasonal snowpack chemistry data from the Rocky Mountain region of the US was examined to identify long-term trends in concentration and chemical deposition in snow and in snow-water equivalent. For the period 1993?2004, comparisons of trends were made between 54 Rocky Mountain Snowpack sites and 16 National Atmospheric Deposition Program wetfall sites located nearby in the region. The region was divided into three subregions: Northern, Central, and Southern. A non-parametric correlation method known as the Regional Kendall Test was used. This technique collectively computed the slope, direction, and probability of trend for several sites at once in each of the Northern, Central, and Southern Rockies subregions....
We examined the content and isotopic composition of nitrogen within soils of a juniper woodland and found that a cryptobiotic crust composed of cyanobacteria, lichens, and mosses was the predominant source of nitrogen for this ecosystem. Disturbance of the crust has resulted in considerable spatial variability in soil nitrogen content and isotopic composition; intercanopy soils were significantly depleted in nitrogen and had greater abundance of 15N compared to intra-canopy soils. Variations in the 15N\14N ratio for inter- and intracanopy locations followed similar Rayleigh distillation curves, indicating that the greater 15N/14N ratios for inter-canopy soils were due to relatively greater net nitrogen loss. Coverage...
GIS-based spatial regression and prediction of water quality in river networks: A case study in Iowa
Nonpoint source pollution is the leading cause of the U.S.’s water quality problems. One important component of nonpoint source pollution control is an understanding of what and how watershed-scale conditions influence ambient water quality. This paper investigated the use of spatial regression to evaluate the impacts of watershed characteristics on stream NO3NO2-N concentration in the Cedar River Watershed, Iowa. An Arc Hydro geodatabase was constructed to organize various datasets on the watershed. Spatial regression models were developed to evaluate the impacts of watershed characteristics on stream NO3NO2-N concentration and predict NO3NO2-N concentration at unmonitored locations. Unlike the traditional ordinary...
The following topics are currently covered by the MineralCommodity Summaries: domestic production and uses; U.S. salientstatistics; recycling; import sources; tariff; depletionallowance; government stockpile; events, trends, and issues;world production, reserves, and reserve base; world resources;and substitutes.
Effect of a one-time application of municipal biosolids on plant growth at a metal mine tailings impoundment in a semi-arid climate, Utah, USA
Effects of chronic nitrogen amendments on production of dissolved organic carbon and nitrogen in forest soils
Renewal rate of semicontinuous cultures of the microalga Porphyridium cruentum modifies phycoerythrin, exopolysaccharide and fatty acid productivity
Effect of water and nitrogen amendments on photosynthesis, leaf demography, and resource-use efficiency in Larrea tridentata , a desert evergreen shrub.
Inputs, outputs, and accumulation of nitrogen in an early successional moss (Polytrichum ) ecosystem.
Effect of temperature, oxygen, salinity, and nutrient enrichment on estuarine denitrification rates measured with a modified nitrogen gas flux technique
Relationship between population dynamics of nitrifiers in biofilms and reactor performance at various C:N ratios