Elevated Concentrations Of NO Research Articles

Response of the West Bear Brook Watershed, Maine, USA, to the addition of (NH 4) 2SO 4: 3-year results

Addition of 1800 eq (NH 4) 2SO 4 ha −1 year −1 for 3 years to a catchment that originally produced low acid neutralizing capacity (ANC) runoff has resulted in significant episodic acidification during high discharge and slight chronic acidification during base flow. These relationships imply that the response to chemical amendments is occurring largely in upper soil horizons and shallow flow paths. The principal responses in stream water chemistry include: elevated volume-weighted concentrations of NO 3, SO 4, base cations, Al, and H, coupled with decreased ANC. The export of dissolved organic carbon may have decreased slightly. Export of SiO 2 has not changed significantly; thus the increase in base cations is interpreted to be largely from desorption from soil. Effects of the manipulation increase from Year 1 to Year 2 to Year 3. Percentage retention of the added SO 4 is declining; retention of NH 4 remains at 100% while export of NO 3 is increasing with time, implying nitrogen saturation and an important change in N dynamics. The export of base cations and Al continues to increase.

Infiltration of Wastewater in a Newly Started Pilot Sand‐Filter System: III. Transformation of Nitrogen

AbstractThe objective of the study was to monitor the chemical dynamics associated with N transformations from start‐up until a steady state was reached in a pilot sand‐filter system consisting of a three‐chambered septic tank, a sand filter with a one person capacity, and eight columns. The system was loaded with 67 L m−2 d−1 of an artificial wastewater. The untreated wastewater contained 114 mg Kjeldahl N L−1 and 0.12 mg NH+4‐N L−1. Mineralization reached a steady state in the septic tank after 2 wk of operation; thereafter, 65 ± 6% of the effluent N was NH+4‐N. In the column effluent the concentrations of NH+4‐N increased during the first 6 wk of operation, whereafter a stabilization at 60 to 80 mg NH+4‐N L−1 occurred. The mean proportion of effluent N in mineralized form for the whole period was 88 ± 6%. Three weeks after start‐up, all effluent N from the sand filter was in mineralized form and remained high for the rest of the study period. The effluent concentrations of NH+4‐N increased rapidly during the first 2 wk after which it decreased to less than 3 mg L−1. The concentration of NO−3‐N was initially low. It then increased until about Day 30 when it stabilized at 64 to 71 mg NO−3‐N L−1. Elevated concentrations of NO−2‐N were observed between Days 8 and 45. Nitrifying activity reached a steady state after 6 wk of operation. During this state a considerable amount of nitrification took place in the upper 1.5 cm and all wastewater N had been nitrified after 15 cm of percolation. By the end of the operating period the total amount of influent N in the septic tank had been reduced by 17%. Corresponding reductions for the columns and sand filter were 18 and 33%, respectively.

Aerobic ethanol production by leaves: Evidence for air pollution stress in trees of the Ohio River Valley, USA.

We measured the frequency with which leaves of trees in the Ohio River Valley produced ethanol aerobically, to determine if aerobic ethanol production might provide a viable field assay for air pollution stress. Leaves were collected from trees during the summers of 1985 and 1986 and ethanol production was determined using headspace GC. Frequency of ethanol production was compared with environmental factors, including air pollution concentrations. We found frequent foliar ethanol production and elevated alcohol dehydrogenase activity in the leaves of several species of trees in the Ohio River Valley, USA. The ethanol concentrations measured were often equivalent to those produced by anaerobic leaves. Ethanol production was associated with hot, hazy weather and elevated NO(2) concentrations. Ethanol production was more frequent in urban and industrialized areas. Ethanol production was not associated with natural stresses such as flooding and herbivory. We propose that aerobic ethanol production is the result of cell acidification due to the accumulation of acidic gases in the cytoplasm. The use of ethanol production as a diagnostic tool for detecting stress imposed by acidic gases is discussed.

Nitrate contamination of shallow groundwaters in Ontario, Canada

Highly elevated concentrations of NO 3 − have been found in the groundwaters from shallow aquifers at several locations in Ontario. The nitrate is derived either from the fertilizers applied to the agricultural soils, or from industrial point sources, and should be regarded as a major water quality problem. However, the nitrate levels may be reduced by denitrification processes under reducing conditions in the aquifer. The distributions of ammonia, chloride, dissolved oxygen, redox potential, methane, calcium and magnesium are presented and related to the hydrogeochemical changes undergone by the pollutant nitrate during flux along the groundwater flow systems.

Aerosols and Trace Gases in the Effluents Produced by the Launch of Large Liquid- and Solid-Fueled Rockets

Abstract Airborne measurements over periods of several hours were made in the effluents that collected in the boundary layer in the form of “ground clouds” when an Atlas/Centaur and Titan III rocket were launched at night-time from Cape Canaveral, Florida. The ground cloud produced by the ATLAS was dry, whereas that produced by the TITAN was initially wet, then dry, and finally wet again. Both clouds dispersed primarily in the horizontal plane. Their volumes at time t (min) were given by V = V0tn where V0 = 1.3 × 106 m3 and n = 0.98 for the ATLAS and V0 &equals 1.76 × 107 m3 and n = 0.94 for the TITAN. The ATLAS ground cloud initially contained elevated concentrations of NO, N02, hydrocarbons and particulate mass. However, dispersion of the cloud quickly reduced these concentrations and the light-scattering coefficient of the cloud. Gas-to-particle conversion (postulated to be the result of the oxidation of NO to NO2 followed by the Formation of NH4NO3) produced smoke particles at a rate of - ∼1016 s−1 in...