Denitrification of the Arctic winter stratosphere has been calculated using a 3-D micro-tion is assumed to occur through the sedimentation of low number concentrations of large nitric acid trihydrate (NAT) particles, as observed extensively in 1999/2000. We 5 examine whether the meteorological conditions that allowed NAT particles to grow to the very large sizes observed in 1999/2000 also occur...

The ability of natural attenuation to mitigate agricultural nitrate contamination in recharging aquifers was investigated in four important agricultural settings in the United States. The study used laboratory analyses, field measurements, and flow and transport modeling for monitoring well transects (0.5 to 2.5 km in length) in the San Joaquin watershed, California, the Elkhorn watershed, Nebr...

A fundamental challenge in understanding the global nitrogen cycle is the quantification of denitrification on large heterogeneous landscapes. Because floodplains are important sites for denitrification and nitrogen retention, we developed a generalized floodplain biogeochemical model to determine whether dams and flood-control levees affect floodplain denitrification by altering floodplain inu...

This paper investigates denitrification of brines originating from membrane treatment of groundwater in an upflow sludge blanket (USB) reactor, a biofilm reactor without carrier. A simulated brine wastewater was prepared from tap water and contained a nitrate concentration of 125 mg/l as N and a total salt concentration of about 1%. In order to select for a suitable energy source for denitrific...

Bacillus azotoformans MEV2011, isolated from soil, is a microaerotolerant obligate denitrifier, which can also produce N2 by co-denitrification. Oxygen is consumed but not growth-supportive. The draft genome has a size of 4.7 Mb and contains key genes for both denitrification and dissimilatory nitrate reduction to ammonium.

Nitrate and nitrite concentrations in the water and nitrous oxide and nitrite fluxes across the sediment-water interface were measured monthly in the River Colne estuary, England, from December 1996 to March 1998. Water column concentrations of N(2)O in the Colne were supersaturated with respect to air, indicating that the estuary was a source of N(2)O for the atmosphere. At the freshwater end ...

[1] Longitudinal and diel measurements of dual isotope composition (dN and dO) in nitrate (NO3-N) were made in the Ichetucknee River, a large ( 8 m s ), entirely spring-fed river in North Florida, to determine whether isotopic variation can deconvolve assimilatory and dissimilatory removal. Comparing nitrate concentrations and isotope composition during the day and night we predicted (1) daytim...

A membrane aerated biofilm reactor (MABR), in which O(2) was supplied from the bottom of the biofilm and NH(4)(+) and organic carbon were supplied from the biofilm surface, was operated at different organic carbon loading rates and intra-membrane air pressures to investigate the occurrence of simultaneous chemical oxygen demand (COD) removal, nitrification and denitrification. The spatial distr...

background contamination of water resources with nitrate is a serious environmental problem in many regions of the world. in addition, this problem has been observed in some regions of iran. as nitrate is threatening for human health and environment, it must be decreased to standard levels in drinking water. objectives the purpose of this research was to model the nitrate removal from water by ...