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Introduction Excess nitrogen concentrations in surface waters and eutrophication continue to be a problem for many North Carolina watersheds (North Carolina Division of Water Quality, 2010). Approximately two million onsite [...], The objective of the study described in this article was to evaluate the nitrogen contributions from two onsite wastewater systems (sites 1 and 2) to groundwater and adjacent surface waters in coastal Beaufort County, North Carolina. Groundwater levels and water quality parameters including total nitrogen, nitrogen species, temperature, and pH were monitored from October 2009 to May 2010. Nitrogen was also tested in groundwater from deeper irrigation or drinking water wells from the two sites and six additional neighboring residences. Mean total nitrogen concentrations in groundwater beneath onsite wastewater systems 1 and 2 were 34.3 ± 16.7 mg/L and 12.2 ± 2.9 mg/L, respectively, and significantly higher than background groundwater concentrations (< 1 mg/L). Groundwater in the deeper wells appeared not to be influenced by the onsite systems. Groundwater nitrogen concentrations typically decreased with distance down-gradient from the systems, but were still elevated relative to background conditions more than 15 m from the systems and near the estuary. This was a pioneering effort to better understand the link of onsite systems, the fate of nitrogen in the environment, and public health.

Quantifying [N.sub.2]O emissions from corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] fields under different fertilizer regimes is essential to developing national inventories of greenhouse gas emissions. The objective of this study was to compare [N.sub.2]O emissions in plots managed for more than 15 yr under continuous corn (C/C) vs. a corn--soybean (C/S) rotation that were fertilized during the corn phase with either anhydrous N[H.sub.3] (AA) or urea (U). During three growing seasons, [N.sub.2]O emissions from corn following corn were nearly identical to corn following soybean. In both systems, however, [N.sub.2]O emissions with AA were twice the emissions with U. After accounting for [N.sub.2]O emissions during the soybean phase, it was estimated that a shift from C/S to C/C would result in an increase in annual emissions of 0.78 kg N [ha.sup.-1] (equivalent to 0.11 Mg C[O.sub.2]-C [ha.sup.-1]) when AA was used, compared with only 0.21 kg N [ha.sup.-1] (0.03 Mg C[O.sub.2]-C [ha.sup.-1]) with U. In light of trends toward increased use of U, these results suggest that fertilizer-induced soil [N.sub.2]O emissions may decline in the future, at least per unit of applied N, although further study is needed in different soils and cropping systems. While soil C[O.sub.2] emissions were 20% higher under C/C, crop residue from the prior year did not affect soil inorganic N or dissolved organic C during the subsequent season. We also compared different flux-calculation schemes, including a new method for correcting chamber-induced errors, and found that selection of a calculation method altered [N.sub.2]O emissions estimates by as much as 35%. Abbreviations: AA, anhydrous ammonia; C/C, continuous corn; Cc, corn after corn; C/S, corn--soybean; Cs, corn after soybean; DOC, dissolved organic carbon; GHG, greenhouse gas; Sc, soybean after corn; U, urea; UAN, urea--ammonium nitrate; WFPS, water-filled pore space. doi:10.2136/sssaj2009.0078

A continuous, 13-yr record of environmental data and phytoplankton species and assemblage structure in the mesohaline Neuse River Estuary (biweekly, April-October; monthly, November March) was used to evaluate phytoplankton assemblage responses to changing environmental conditions. Ordination techniques including nonmetric multidimensional scaling, indicator species analysis, and BIO-ENV software were used to investigate potential environmental predictors of phytoplankton assemblage patterns under chronic eutrophication. Phytoplankton assemblages were strongly related to temperature and total nitrogen : total phosphorus ratios, with expected seasonal changes in species composition. Interannual changes in river discharge influenced whether phytoplankton assemblages were dominated by diatoms and phototrophic flagellates or by mixotrophic and heterotrophic dinoflagellates. Increasing ammonium concentrations also have been an important influence on phytoplankton assemblages. Raphidophytes (including the potentially toxic species Heterosigma akashiwo), haptophytes, chlorophytes, and the bloom-forming dinoflagellate Heterocapsa rotundata have increased in more recent years (2000-2006), concomitant with increasing ammonium concentrations. Abundance of the potentially toxic dinoflagellates Prorocentrum minimum and the grouping Pfiesteria spp., 'pfiesteria-like' dinoflagellates, and Karlodinium veneficum remained stationary over time and rarely exceeded [10.sup.3] cells [mL.sup.-1]. Abundance of P. minimum was positively related to dissolved organic nitrogen and suspended solids concentrations, whereas the highest abundance of the grouping Pfiesteria spp., 'pfiesteria-like' dinoflagellates, and K. veneficum occurred during summer and fall, related to high total phosphorus concentrations, temperature, and salinity. Overall, this study provides new species-level insights to advance understanding about anthropogenic influences on phytoplankton assemblages. The data suggest an increasingly important role of ammonium in controlling phytoplankton assemblage structure, including increased abundance of some harmful species, in eutrophic estuaries.

We examined the role of chronic low-level nutrient enrichment on the productivity of heterotrophic marsh bacteria via a marsh fertilization experiment in which we mimicked the conditions of widespread coastal eutrophication by enriching entire salt marshes to approximately 15x background nutrient concentrations. We measured the uptake of tritiated leucine, as a proxy for bacterial production, in both low and high marsh habitats in four salt marshes, two of which were enriched with nutrients. We hypothesized that adding nitrogen in these detritus-rich systems would directly stimulate bacterial decomposition of marsh peat. Contrary to our expectations, we found no response to added nutrients in high marsh habitats, where there is a significant supply of organic matter from marsh vegetation. Bacterial production did increase in the low marsh habitats, where fertilization increased the standing stock of benthic chlorophyll. Fertilization did not directly increase bacterial production by providing added nutrients that could be used to decompose organic matter derived from nutrient-poor marsh grasses. Rather, bacterial productivity was indirectly stimulated by the concomitant increase in labile benthic microalgae in low marsh habitats. Decomposition of salt marshes may therefore have a greater resilience to the threat of chronic eutrophication than has been previously recognized.

Net primary productivity (NPP) is enhanced under future atmospheric [C[O.sub.2]] in temperate forests representing a broad range of productivity. Yet questions remain in regard to how elevated [C[O.sub.2]]-induced NPP enhancement may be affected by climatic variations and limiting nutrient resources, as well as how this additional production is distributed among carbon (C) pools of different longevities. Using 10 years of data from the Duke free-air C[O.sub.2] enrichment (Duke FACE) site, we show that spatially, the major control of NPP was nitrogen (N) availability, through its control on canopy leaf area index (L). Elevated C[O.sub.2] levels resulted in greater L, and thus greater NPP. After canopy closure had occurred, elevated [C[O.sub.2]] did not enhance NPP at a given L, regardless of soil water availability. Additionally, using published data from three other forest FACE sites and replacing L with leaf area duration ([L.sub.D]) to account for differences in growing season length, we show that aboveground NPP responded to [C[O.sub.2]] only through the enhancement of [L.sub.D]. For broadleaf forests, the fraction of aboveground NPP partitioned to wood biomass saturated with increasing [L.sub.D] and was not enhanced by [C[O.sub.2]], whereas it linearly decreased for the conifer forest but was enhanced by [C[O.sub.2]]. These results underscore the importance of resolving [C[O.sub.2]] effects on L to assess the response of NPP and C allocation. Further study is necessary to elucidate the mechanisms that control the differential allocation of C among aboveground pools in different forest types. carbon allocation | global change | nitrogen availability | pine plantation

A single-stage phosphorylated polyvinyl alcohol immobilized-cell reactor with three operation modes was employed to investigate the efficiency of simultaneous carbon/nitrogen removal from raw swine wastewater. In continuous aeration mode, the removal efficiency of chemical oxygen demand (COD) and total nitrogen (T-N) exceeded 70 and 8%, respectively, at hydraulic retention time of 10 days. In intermittent aeration (IA) mode, the removal efficiency of COD and T-N was more than 85 and 46%, respectively, when the reactor was set at 50% aeration duration to cycle time to operate at three aerobic-anoxic cycles per day. When oxidation-reduction-potential control was adopted to control the duration of the anoxic period in the real-time controlled (RTC) IA mode for a 4 h aeration period, the total cycle time was reduced by about 20% with a slight increase in removal efficiency of COD (87%) and T-N (47%). The system with no extra chambers required is efficient in simultaneous carbon/nitrogen removal. DOI: 10.1061/(ASCE)0733-9372(2006)132:3(423) CE Database subject headings: Simulation; Abatement and removal; Carbons; Nitrogen; Wastewater management; Reactors.

Human urine contributes 80% of the total nitrogen and 40-50% of the total phosphate load to municipal wastewater. This study examines the impact of separate urine collection and treatment on wastewater treatment. An integrated wastewater and urine treatment process was defined, in which single high-rate ammonium removal over nitrite and anaerobic ammonium oxidation processes and struvite recovery are at the heart of the nutrient management. The model study demonstrated that if 50% or more of urine were collected and treated separately, integrated wastewater treatment with more compact and energy-efficient processes would be possible. The integrated wastewater and urine treatment is compared to an existing state-of-the-art treatment process. The main advantage of urine separation is not only a better effluent quality. Existing processes including tertiary treatment can already produce very good effluent quality with total effluent nitrogen and phosphate concentrations of 2.5 and 0.5 g/[m.sup.3], respectively. The main advantage of urine separation is the production of this same good effluent quality with a remarkable saving in resources. With sufficient urine separation, generation of net primary energy is possible. DOI: 10.1061/(ASCE)0733-9372(2006)132:3(331) CE Database subject headings: Wastewater management; Nitrogen; Municipal wastes; Nutrients.

The likely magnitude of nonlinearities in the source-receptor relationship for sulfur and oxidized nitrogen and their causes were identified by examining the emission and deposition data for the UK. The dry deposition process was found to be strongly influenced by ambient concentrations of NH(sub 3) resulting in a substantial increase in deposition rate on decline of both SO(sub 2) concentrations and the ratio of SO(sub 2)/NH(sub 3) whereas during the period form 1987 to 2001, the concentrations and deposition of NO(sub 3) in precipitation have declined little following a reduction in emissions of 45 percent.

We quantified anaerobic [N.sub.2] production through bacterial denitrification and anaerobic N[H.sup.+.sub.4] oxidation (anammox) in first-year ice from Young Sound (74[degrees]N) and in an ice floe off Northeast Greenland (79[degrees]N). Bacterial denitrification activity (100-300 nmol N [L.sup.-1] sea ice [d.sup.-1]) occurred in the lower 0.5 m of the sea ice, which had high concentrations of N[O.sup.-. sub.3], N[H.sup.+.sub.4], and dissolved organic carbon (DOC). Despite sea-ice algal production in the lower sea-ice layers, heterotrophic activity resulted in a net [O.sub.2] consumption of 13 [micro]mol [O.sub.2] [L.sup.-1] sea ice [d.sup.-1] in the lower 0.5-m ice layers. Together with melting of deoxygenated ice crystals, this led to anoxic conditions in the brine system favoring conditions for anaerobic N[O. sup.-.sub.3] reduction. Numbers of anaerobic N[O.sup.-.sub.3]-reducing bacteria in the same ice layers were high (1.1 x [10.sup.5] cells [ml. sup.-1] sea ice, corresponding to 1.2 x [10.sup.6] cells [ml.sup.-1] brine). Area-integrated denitrification rates were 10-45 [micro]mol N [m.sup.-2] sea ice [d.sup.-1], which corresponds to 7-50% of the sediment activity in the area. Although the proportion of anammox to total [N.sub.2] production was up to 19% in layers of the ice floe from the Greenland Sea, the integrated rate only accounted for 0-5% of total N[O.sup.-.sub.3] reduction at the investigated localities.

Coastal lagoons are a common land-margin feature worldwide and function as an important filter for nutrients entering from the watershed. The shallow nature of lagoons leads to dominance by benthic autotrophs, which can regulate benthic-pelagic coupling. Here we demonstrate that both microalgae and macroalgae are important in controlling dissolved inorganic as well as organic nitrogen (DIN and DON) fluxes between the sediments and the water column. Fluxes of nitrogen (N[H.sup.+.sub.4], N[O.sup-.sup.3], DON, urea, and dissolved free and combined amino acids [DFAA, DCAA]) and [O.sup.2] were measured from October 1998 through August 1999 in sediment cores collected from Hog Island Bay, Virginia. Cores were collected from four sites representing the range of environmental conditions across this shallow lagoon: muddy, high-nutrient and sandy, low-nutrient sites that were both dominated by benthic microalgae, and a mid-lagoon site with fine sands covered by dense macroalgal mats. Sediment--water column DON fluxes were highly variable and comparable in magnitude to DIN fluxes; fluxes of individual compounds (urea, DFAA, DCAA) often proceeded simultaneously in different directions. Where sediment metabolism was net autotrophic because of microalgal activity, TDN (total dissolved nitrogen) fluxes, mostly comprised of DIN, urea, and DFAA, were directed into the sediments. Heterotrophic sediments, including those underlying macroalgal mats, were a net source of TDN, mostly as DIN. Macroalgae intercepted sediment--water column fluxes of DIN, urea, and DFAA, which accounted for 27-75% of calculated N demand. DON uptake was important in satisfying macroalgal N demand seasonally and where DIN concentrations were low. Up to 22% of total N uptake was released to the water column as DCAA. Overall, macroalgae assimilated, transformed, and rereleased to the water column both organic and inorganic N on short (minutes--hours) and long (months) time scales. Microalgae and macroalgae clearly regulate benthic-pelagic coupling and thereby influence transformations and retention of N moving across the land-sea interface.

A study in Monterey Bay, CA, has indicated that a dissolved organic nitrogen (DON) pool functions as an intermediate between DIN assimilation and the net formation of particles for export, which will then affect carbon flow in the bay. The net and gross nitrogen uptake and DON release have been studied using 15N tracer techniques to measure rates of ammonium ion and nitrate uptake in the euphotic zone of the bay.

Oxidative degradation rates of aqueous 2,4,6-trinitrotoluene by ozone has been found to be dependent on ozone concentrations, pH levels, discharge energies and electrode gap lengths. Results of oxidation experiments in the electrohydraulic discharge reactor also reveal that rapid mineralization rates may be attributed to the action of UV light on the ozone to produce a high flux of hydroxyl radicals per dircharge.

Fourier transform infrared spectrometry was used to analyze the rate of production of nitrous acid (HONO) from the reaction between HO2 radicals and NO2. Results revealed that no evidence that HONO was generated by the reaction, whose upper limit for the rate coefficienct was determined to be 5 x 10(super -16) cubic centimeters per molecule per second. This indicates that the reaction cannot be a significant source of atmospheric HONO.

The feasibility of using organic tertiary hydroperoxides for reducing nitrogen oxide (NO) emissions of agricultural and industrial substances is evaluated. Experiments are conducted in a scrubber reactor system wherein a reaction mixture of nitrogen compunds is treated with different types of organic hydroperoxide solutions at constant operating temperature. Measurements obtained through a gas chromatograph show that cumenyl hydroperoxide performs better that its counterparts in minimizing the NO emissions of nitrogen compounds.

The effect of the addition of extra precipitation in summer and autumn on concentrations and fluxes of Total organic carbon (TOC) and total organic nitrogen (TON) in runoff is studied. The shorts droughts have a small effect on the overall fluxes of TOC and TON in runoff from small catchments at Storgama, throughout growing season.

Research has been conducted on replicated river biofilms cultivated in rotating annular reactors. The effect of seasonal variations and nutrient inputs on biofilms' genetic compositions and physiological activities has been investigated via the use of physiological and molecular biology techniques.

Nonthermal plasma chemical behavior of [N.sub.2]-[O.sub.2] mixed gases and nitrogen oxides such as [N.sub.2] O, NO, and [NO.sub.2] was investigated to obtain baseline information on the generation of active oxygen species and the formation of inorganic byproducts in the nonthermal plasma chemical processing of hazardous air pollutants (HAPs) with a ferroelectric packed-bed reactor. Ozone concentrations were too low, even in air, to oxidatively decompose 300-1000 ppm of HAPs. The [O.sub.2] concentration in [N.sub.2]-[O.sub.2] was the determining factor in the formation of all the nitrogen oxides. [N.sub.2]O formation was enhanced with increases in [O.sub.2] concentration and in specific energy density, while a threshold value was observed around at 5% of [O.sub.2] concentration in the formation of NO and [NO.sub.2]. Rate-suppressing effect by [O.sub.2], detailed byproduct analyses, and thermochemical data suggest that [NO.sub.x] decomposes in its reactions with nitrogen atoms derived from [N.sub.2] dissociation, and that the unimolecular N-O cleavage predominantly occurs for [N.sub.2]O. The behavior of nitrogen oxides and their precursors was not affected by hydrogen atoms evolved from hydrogen-rich HAPs such as ethylene and benzene. Halogenated HAPs enhanced [NO.sub.x] formation and [NO.sub.2] selectivity. Different additive effects of chlorinated and brominated HAPs were observed in the formation of [NO.sub.x] and [N.sub.2]O, indicating the involvement of different active oxygen species. Index Terms--Hazardous air pollutants, nitrogen molecule, nitrogen oxides, nonthermal plasma, reactivity.

A survey conducted by New Hampshire University scientists shows that nitrogen is exceeding the specified limits and saturating the atmosphere due to excessive fossil-fuel burning. Nitrogen is a useful fertilizer but a large amount will affect foliage and the ecological process. The early detection of higher quantities of nitrogen in the atmosphere will be useful in implementing immediate relief measures.

Researchers from Germany reported that NOx and SOx emissions from ships may help lower climate temperatures.