共查询到20条相似文献,搜索用时 843 毫秒
1.
Impacts of diazinon (O,O-diethyl O-2-isopropyl-6-methylpyrimidin-4-yl phosphorothioate), imidacloprid [1-(6-chloro-3-pyridylmethyl)-N-nitroimidazolidin-2-ylideneamine] and lindane (1,2,3,4,5.6-hexachlorocyclohexane) treatments on ammonium, nitrate, and nitrite nitrogen and nitrate reductase enzyme activities were determined in groundnut (Arachis hypogaea L.) field for three consecutive years (1997 to 1999). Diazinon was applied for both seed- and soil-treatments but imidacloprid and lindane were used for seed treatments only at recommended rates. Diazinon residues persisted for 60 days in both the cases. Average half-lives (t1/2) of diazinon were found 29.3 and 34.8 days respectively in seed and soil treatments. In diazinon seed treatment, NH4(+), NO3(-), and NO2(-) nitrogen and nitrate reductase activity were not affected. Whereas, diazinon soil treatment indicated significant increase in NH4(+)-N in a 1-day sample, which continued until 90 days. Some declines in NO3(-)N were found from 15 to 60 days. Along with this decline, significant increases in NO2(-)N and nitrate reductase activity were found between 1 and 30 days. Imidacloprid and lindane persisted for 90 and 120 days with average half-lives (t1/2) of 40.9 and 53.3 days, respectively. Within 90 days, imidacloprid residues lost by 73.17% to 82.49% while such losses for lindane residues were found 78.19% to 79.86 % within 120 days. In imidacloprid seed-treated field, stimulation of NO3(-)N and the decline in NH4+NO2(-)-N and nitrate reductase enzyme activity were observed between 15 to 90 days. However, lindane seed treatment indicated significant increases in NH4(+)-N, NO2(-)-N and nitrate reductase activity and some adverse effects on NO3(-)N between 15 and 90 days. 相似文献
2.
Impacts of diazinon, imidacloprid and lindane treatments on dehydrogenase and alkaline phosphomonoesterase enzyme activities were determined in groundnut (Arachis hypogaea L.) field for three consecutive years (1997-1999). Diazinon was applied as both seed and soil treatments but imidacloprid and lindane were used for seed treatments only at recommended rates. Experiments were conducted at Agricultural Research Station Durgapura, Jaipur, Rajasthan, India. Diazinon residues were persist up till 60 days in both the cases. Average half-lives (t(1/2)) of diazinon were found 29.3 and 34.8 days, respectively, for seed and soil treatments. Diazinon seed treatment had no significant effect on dehydrogenase and alkaline phosphomonoesterase enzymes activities. In diazinon soil treatment, there were a significant increase in dehydrogenase and decrease in alkaline phosphomonoesterase activities after 24 h of treatment, which continued till 30 days. In seed treatments, imidacloprid and lindane were present in soil up to 90 and 120 days with average half-lives (t(1/2)) of 40.9 and 53.3 days, respectively. Within 90 days, imidacloprid residues were declined up to 73.17% to 82.49% while decline in lindane residues ranged from 78.19% to 79.86% within 120 days. In imidacloprid seed treated field, both dehydrogenase and phosphomonoesterase activities were increased between 15 and 60 days after sowing. However, a significant decreases in both dehydrogenase and phosphomonoesterase enzyme activities were observed between 15 and 90 days after lindane seed treatment. 相似文献
3.
Pseudomonas sp. Y-5, a strain with simultaneous nitrification and denitrification (SND) capacity, was isolated from the Wuhan Municipal Sewage Treatment Plant. This strain could rapidly remove high concentrations of inorganic nitrogen. Specifically, Pseudomonas sp. Y-5 removed 103 mg/L of NH4+-N in 24 h without nitrate or nitrite accumulation when NH4+-N was its sole nitrogen source. The NH4+-N removal efficiency (RE) was 97.26%, and the average removal rate (RR) was 4.30 mg/L/h. Strain Y-5 also removed NO3?-N and NO2?-N even in aerobic conditions, with average RRs of 4.39 and 4.23 mg/L/h, respectively, and REs of up to 99.34% and 95.81% within 24 h. When cultured in SND medium (SNDM-1), strain Y-5 achieved an NH4+-N RE of up to 97.80% and a total nitrogen (TN) RE of 93.01%, whereas NO3?-N was fully depleted in 48 h. Interestingly, high nitrite concentrations did not inhibit the nitrification capacity of Y-5 when grown in SNDM-2, the RE of NH4+-N and TN reached 96.29% and 94.26%, respectively, and nitrite was consumed completely. Strain Y-5 also adapted well to high concentrations of ammonia (~401.68 mg NH4+-N/L) or organic nitrogen (~315.12 mg TN/L). Our results suggested that Pseudomonas sp. Y-5 achieved efficient simultaneous nitrification and denitrification, thus demonstrating its potential applicability in the treatment of nitrogen-polluted wastewater. 相似文献
4.
Bacterial, azotobacter, actinomycetes, and fungal populations were determined in groundnut (Arachis hypogaea L.) fields between July and November for three consecutive years (1997-1999) after insecticide treatments. Diazinon was applied for both seed and soil treatments. However, imidacloprid and lindane were used for seed treatments. An average half-life (t1/2) of diazinon in seed- and soil-treated fields was found to be 29.32 and 34.87 days, respectively. Its residues were found for 60 days in both cases. In diazinon seed treatment, an increase in azotobacter, fungi, and actinomycetes populations was observed in samples from the 15th and 30th days, and this trend continued until crop harvest. However, the bacterial population had not been affected by this treatment. The diazinon soil treatment had indicated some significant adverse effects on fungi and actinomycetes population, which recovered after 30 days. The population of bacteria and azotobacter increased significantly in this treatment. The residues of imidacloprid and lindane were found for 90 and 120 days with an average half-life of 40.9 and 53.3 days, respectively. Imidacloprid had no significant effect on fungi and actinomycetes populations up to 15 days, and between 15 to 60 days some adverse effects were indicated. However, some significant increases in bacterial and azotobacter population were observed. Lindane had no effect on bacterial and fungal population. However, its adverse effects were observed in actinomycetes and azotobacter populations between 30 to 60 days. 相似文献
5.
The aims of this study are to investigate whether and how the nitrogen form (nitrate (NO 3 –) versus ammonium (NH 4 +)) influences cadmium (Cd) uptake and translocation and subsequent Cd phytoextraction by the hyperaccumulator species Sedum plumbizincicola. Plants were grown hydroponically with N supplied as either NO 3 – or NH 4 +. Short-term (36 h) Cd uptake and translocation were determined innovatively and quantitatively using a positron-emitting 107Cd tracer and positron-emitting tracer imaging system. The results show that the rates of Cd uptake by roots and transport to the shoots in the NO 3 – treatment were more rapid than in the NH 4 + treatment. After uptake for 36 h, 5.6 (0.056 μM) and 29.0 % (0.290 μM) of total Cd in the solution was non-absorbable in the NO 3 – and NH 4 + treatments, respectively. The local velocity of Cd transport was approximately 1.5-fold higher in roots (3.30 cm h ?1) and 3.7-fold higher in shoots (10.10 cm h ?1) of NO 3 –- than NH 4 +-fed plants. Autoradiographic analysis of 109Cd reveals that NO 3 – nutrition enhanced Cd transportation from the main stem to branches and young leaves. Moreover, NO 3 – treatment increased Cd, Ca and K concentrations but inhibited Fe and P in the xylem sap. In a 21-day hydroponic culture, shoot biomass and Cd concentration were 1.51 and 2.63 times higher in NO 3 –- than in NH 4 +-fed plants. We conclude that compared with NH 4 +, NO 3 – promoted the major steps in the transport route followed by Cd from solution to shoots in S. plumbizincicola, namely its uptake by roots, xylem loading, root-to-shoot translocation in the xylem and uploading to the leaves. S. plumbizincicola prefers NO 3 – nutrition to NH 4 + for Cd phytoextraction. 相似文献
6.
Abstract The Reedy River branch of Lake Greenwood, SC, has repeatedly experienced summertime algal blooms, upsetting the natural system. A series of experiments were carried out to investigate atmospheric nitrogen (N) input into the lake. N was examined because of the insignificant phosphorus dry atmospheric flux and the unique nutrient demands of the dominant algae ( Pithophora oedogonia) contributing to the blooms. Episodic atmospheric measurements during January and March 2001 have shown that the dry N flux onto the lake ranged from 0.9 to 17.4 kg N/ha-yr, and on average is caused by nitric acid (HNO 3; 31%), followed by nitrogen dioxide (NO 2; 23%), fine ammonium (NH 4 +; 20%), coarse nitrate (NO 3 ?; 16%), fine NO 3 + (5%), and coarse NH 4 + (5%). Similar measurements in Greenville, SC (the upper watershed of the Reedy River), showed that the dry N deposition flux there ranged from 1.4 to 9.7 kg N/ha-yr and was mostly caused by gaseous deposition (40% NO 2 and 40% HNO 3). The magnitude of this dry N deposition flux is comparable to wet N flux as well as other point sources in the area. Thermodynamic modeling showed low concentrations of ammonia, relative to the particulate NH 4 + concentrations. 相似文献
7.
Monthly nitrogen isotopes of ammonium and nitrate in wet deposition in the city of Guangzhou, and the causes of their variability, are reported in this paper. Nitrate δ 15N showed nearly constant values around zero in the dry season (October to April), but oscillating values from negative to positive in the rainy season (May to September). By contrast, ammonium δ 15N displayed lower values during the rainy season than in the dry season. The rural area north of the city was considered as the prominent source of ammonium and nitrate in spring and early summer (May and June), as suggested by their concurrent negative isotopic trends and higher NH 4+/NO 3? ratios. From July to September, different dominating sources from the city, i.e., fossil fuel combustion for nitrate, and sewage and waste emission for ammonium, caused disparate δ 15N trends of the two species, showing positive nitrate δ 15N, but still negative ammonium δ 15N. During the cool dry season, the high values of ammonium δ 15N and concurrently low NH 4+/NO 3? ratios suggested the decrease in NH 3 volatilization and relatively important thermogenic origin of ammonium, but the intermediate nitrate δ 15N values around zero may be a result of a balanced emission of NO x from the city and the rural areas. The isotopic effects of chemical conversion of NO x to nitrate and washout of nitrate were ruled out as significant causes of nitrate δ 15N variability, but ammonium washout, during which 15N is assumed to be preferentially removed, may partly contribute to the ammonium δ 15N variability. 相似文献
8.
Abstract The long-term stability of a biofilter loaded with waste gases containing NH 3 concentrations larger than 100 ppmv was studied in a laboratory-scale compost reactor. At an empty bed residence time (τ) of 21 sec, elimination capacities of more than 300 g NH 3/m 3/day were obtained at elimination efficiencies up to 87%. Because of absorption and nitrification, almost 80% of the NH 3-N eliminated from the waste gas could be recovered in the compost as NH 4+-N or NO 2 ?/NO 3 ?-N. The high elimination capacities could be maintained as long as the NH 4+/NO x concentration in the carrier material was less than 4 g NH 4+/NO x ?-N/kg wet compost. Above this critical value, osmotic effects inhibited the nitrifying activity, and the elimination capacity for NH 3 decreased. To restore the biofilter performance, a carbon source (methanol) was added to reduce NH 4+/NO x ? accumulated in the compost. Results indicate that methylotrophic microorganisms did convert NH 4+/NO x ? into biomass, as long as the NO 3 ? content in the compost was larger than 0.1 g NO 3 ?-N/kg compost. Removal efficiencies of CH 3OH of more than 90% were obtained at volumetric loads up to 11,000 g CH 3OH/m 3/day. It is shown that addition of CH 3OH is a suitable technique for regenerating the compost material from osmotic inhibition as a result of high NH 3 loading. The biofilter was operated for 4 months with alternating loading of NH 3 and CH 3OH. 相似文献
9.
In order to discuss the dry deposition fluxes of atmospheric fixed nitrogen species, observations of aerosol chemistry including nitrate (NO 3?) and ammonium (NH 4+) were conducted at two islands, Rishiri Island and Sado Island, over the Sea of Japan. Although the atmospheric concentrations of particulate NH 4+–N showed higher values than those of particulate NO 3?–N at both sites, the dry deposition fluxes of the particulate NO 3?–N were estimated to be higher than those of the particulate NH 4+–N. This was caused by the difference of particle sizes between the particulate NO 3? and NH 4+; NH 4+ was almost totally contained in fine particles ( d < 2.5 μm) with smaller deposition velocity, whereas NO 3? was mainly contained in coarse particles ( d > 2.5 μm) with greater deposition velocity. Fine mode NO 3? was strongly associated with fine mode sea-salt and mineral particles, of which higher concentrations shifted the size of particulate NO 3? toward the fine mode range. This size shift would decrease the dry deposition flux of the fixed nitrogen species on coastal waters and accelerate atmospheric transport of them to the remote oceanic areas. 相似文献
10.
利用MATLAB/SIMULINK对序批式生物膜反应器内的氨氧化细菌与亚硝酸盐氧化菌的生化反应进行仿真预测。模型的验证结果表明,适当的选择模型中的溶解氧浓度、碱度以及温度3种参数,SIMULINK仿真动力学模型能够比较准确地对氨氧化细菌与亚硝酸氧化细菌处理生活污水的过程进行仿真和预测.NH4+-N、NO2--N和NO3--N 3种基质仿真值的绝对平均误差最大为15.88,最小为1.13;NH4+-N、NO2--N和NO3--N的Nash.Suttcliffe模拟效率系数分别为99.36%、98.64%和99.25%;此外,还对SIMULINK仿真动力学模型中的溶解氧浓度、碱度以及温度进行了灵敏度分析,结果表明,温度的灵敏度最大、溶解氧次之、碱度灵敏度相对最小。 相似文献
11.
利用氮素计量关系和批式实验研究了SBR系统中基于短程硝化的单级自养脱氮特性和脱氮途径。结果表明,SBR系统获得良好脱氮效果,TN最高去除负荷和去除速率分别达0.49 kg N/(m3.d)和0.20 kg N/(kg VSS.d);系统中82%的氨氮转化成气体脱除,10%的氨氮转化成硝酸盐氮。批式实验结果表明,SBR系统中的污泥同时具有厌氧氨氧化、亚硝酸盐氧化和自养反硝化活性,三者的反应速率分别为0.12 kg NH4+-N/(kg VSS.d)、0.04 kg NO2--N/(kg VSS.d)和0.03 kg NO2--N/(kg VSS.d)。综上,SBR系统中氮的脱除是短程硝化、厌氧氨氧化和反硝化共同作用的结果,产生的硝酸盐是厌氧氨氧化和硝化作用所致。 相似文献
12.
ABSTRACTThis study investigated spatio-temporal variations of selected pesticide residues in the Kurose River in Higashi-Hiroshima city (Hiroshima Prefecture), Japan. Water samples were collected from the river at seven sites every month for 1 year (March 2016 to February 2017). Pesticide residues were extracted from the samples by a solid phase extraction using Sep Pack C 18 cartridges. Once extracted, the samples were analyzed for cyanazine, simetryn, fenarimol, isoprothiolane, and diazinon using a reversed-phase high-performance liquid chromatography ultraviolet visible (HPLC-UV Vis) system. The limits of detection were 3.60, 4.10, 2.80, 6.50, and 7.30 ng L -1 for cyanazine, simetryn, fenarimol, isoprothiolane, and diazinon, respectively. Good recovery rates (88%–102%), and mean percent relative standard deviation range (1.00%–5.70%) ( n = 6) were obtained with a spiking at 0.20 µg L -1. The maximum concentrations of 282, 391, 60, 1086, and 1194 ng L -1 were obtained for cyanazine, simetryn, isoprothiolane, fenarimol, and diazinon, respectively. Cyanazine was the most frequently detected pesticide (64% of the samples, n = 84), followed by simetryn (58%), and then diazinon (57%). The highest and lowest pesticide concentrations were measured during the periods May–June, and January–February, respectively. Principal component analysis revealed three principal components in which the pesticides were linked to dissolved organic matter and total suspended solids. The major water quality parameters (electrical conductivity, pH, Na +, K +, Mg 2+, Ca 2+, NH 4+, NO 3?, Cl ?, SO 42?, NO 2?, and temperature) showed no clear trends for these pesticides. The presence of simetryn and isoprothiolane was largely attributed to rice paddy farms, whereas diazinon was associated mostly with vegetable farms and orchards. The diazinon and isoprothiolane patterns were consistent with their use of controlling insects and fungi in the prefecture. The maximum diazinon concentration detected was higher than the human safe level specified by the European Union (100 ng L -1) in Council Directive 98/83/EC. This is of concern because of the bioconcentration potential of these residues in fish and other marine animals consumed by humans. 相似文献
13.
This study investigates ammonium, nitrate, and sulfate (NH 4+, NO 3?, and SO 42?) in size-resolved particles (particularly nano (PM 0.01–0.056)/ultrafine (PM 0.01–0.1)) and NO x/SO 2 collected near a busy road and at a rural site. The average (mass) cumulative fraction of secondary inorganic aerosols (SO 42?+NO 3?+NH 4+) in nano or ultrafine particles at the roadside was found to be three to four times that at the rural site. The above three secondary inorganic aerosol species were present in similar cumulative fractions in particles of size 1–18 μm at both sites; however, dissimilar fractions were observed for Cl ?, Na +, and K +. The nitrogen ratios (NRs: NR = NO 3??N/(NO 3??N + NO 2–N)), sulfur ratios (SRs: SR = SO 42??S/(SO 42??S + SO 2–S)), dNR/D P (derivative of NR with respect to D P (particle diameter)), and dSR/D P (derivative of SR with respect to D P) at the roadside were higher than those at the rural site for nano/ultrafine particles. At both sites (particularly the roadside), the nanoparticles had significantly higher dNR/D P and dSR/D P values than differently sized particles, implying that NO 3?/SO 42? (from NO 2/SO 2 transformation or NO 3?/SO 42? deposition) were present on these particles. 相似文献
14.
Simultaneous daily measurements of water-soluble organic nitrogen (WSON), ammonium and nitrate were made between July and November 2008 at a rural location in south-east Scotland, using a ‘Cofer’ nebulizing sampler for the gas phase and collection on an open-face PTFE membrane for the particle phase. Average concentrations of NH 3 were 82 ± 17 nmol N m ?3 (error is s.d. of triplicate samples), while oxidised N concentrations in the gas phase (from trapping NO 2 and HNO 3) were smaller, at 2.6 ± 2.2 nmol N m ?3, and gas-phase WSON concentrations were 18 ± 11 nmol N m ?3. The estimated collection efficiency of the nebulizing samplers for the gas phase was 88 (±8) % for NH 3, 37 (±16) % for NO 2 and 57 (±7) % for WSON; reported average concentrations have not been corrected for sampling efficiency. Concentrations in the particle phase were smaller, except for nitrate, at 21 ± 9, 10 ± 6 and 8 ± 9 nmol N m ?3, respectively. The absence of correlation in either phase between WSON and either (NH 3 + NH 4+) or NO 3? concentrations suggests atmospheric WSON has diverse sources. During wet days, concentrations of gas and particle-phase inorganic N were lower than on dry days, whereas the converse was true for WSON. These data represent the first reports of simultaneous measurements of gas and particle phase water-soluble nitrogen compounds in rural air on a daily basis, and show that WSON occurs in both phases, contributing 20–25% of the total water-soluble nitrogen in air, in good agreement with earlier data on the contribution of WSON to total dissolved N in rainfall in the UK. 相似文献
15.
Abstract The removal capacity of carbon and nitrogen from an artificial leachate was evaluated by using laboratory-scale columns, and a design was proposed to remove nitrogen more efficiently from a semiaerobic landfill. Five columns (i.e., two artificial municipal waste columns under anaerobic and semiaerobic conditions, an artificial construction waste column under semiaerobic conditions, and two crushed stone columns under anaerobic and semiaerobic conditions) were used. The influent load rates of organics [g chemical oxygen demand (COD)/m 3 ·day], NH 4 +, NO 3 ?, and aeration conditions for the columns were varied, and the removal capacities of the columns for COD, NH 4 +-N, and NO 3 ?-N were measured. Among the packed column materials, crushed stone was shown to be most effective in removing COD, NH 4 +-N, and NO 3 ?-N from artificial leachate. Average removal rates of crushed column under the semiaerobic condition (column D) for COD and NH 4 +-N were estimated at about 150 g COD/m 3·day and 20 g COD/m 3 ·day, while those of crushed column under anaerobic condition (column E) for COD and NO 3 ?-N at about 400 and 150 g COD/m 3 ·day, respectively. It also was found that denitrification and nitrification reactions in column D occurred at the same time, and the ratio of denitrification to nitrification was estimated to be about 80%. Therefore, an anaerobic structure, which could be attached to the bottom of a main pipe in a semiaerobic landfill, is suggested to remove nitrogen and organic substances more effectively. 相似文献
16.
TSP and PM 2.5 samples were collected at Xi'an, China during dust storms (DSs) and several types of pollution events, including haze, biomass burning, and firework displays. Aerosol mass concentrations were up to 2 times higher during the particulate matter (PM) events than on normal days (NDs), and all types of PM led to decreased visibility. Water-soluble ions (Na +, NH 4+, K +, Mg 2+, Ca 2+, F ?, Cl ?, NO 3?, and SO 42?). were major aerosol components during the pollution episodes, but their concentrations were lower during DSs. NH 4+, K +, F ?, Cl ?, NO 3?, and SO 42? were more abundant in PM 2.5 than TSP but the opposite was true for Mg 2+ and Ca 2+. PM collected on hazy days was enriched with secondary species (NH 4+, NO 3?, and SO 42) while PM from straw combustion showed high K + and Cl ?. Firework displays caused increases in K + and also enrichments of NO 3? relative to SO 42?. During DSs, the concentrations of secondary aerosol components were low, but Ca 2+ was abundant. Ion balance calculations indicate that PM from haze and straw combustion was acidic while the DSs samples were alkaline and the fireworks' PM was close to neutral. Ion ratios (SO 42?/K +, NO 3?/SO 42?, and Cl ?/K +) proved effective as indicators for different pollution episodes. 相似文献
17.
选取了5种研究较少的固体材料,棉花、丝瓜络、甘蔗渣、可降解餐盒、木屑作为去除地下水硝酸盐的外加碳源。在锥形瓶中进行反硝化对比实验,研究了不同固态碳源下NO3--N、NO2--N、NH4+-N及pH的变化情况,分析了NO3--N及总氮的去除率。研究结果表明,反硝化过程中pH呈升高趋势,在6.9~8.5范围内浮动。可降解餐盒和丝瓜络相对于其他的固态碳源来说,对NO3--N和总氮有较高的去除率,但丝瓜络的总氮去除率明显低于可降解餐盒。可降解餐盒的硝酸盐去除率达到98.28%,总氮去除率达到93.48%。可降解餐盒能够有效地去除地下水硝酸盐,达到以废治废的效果,是经济有效的最佳固态碳源。 相似文献
18.
In order to investigate the treatment performance and microorganism mechanism of IVCW for domestic wastewater in central of China, two parallel pilot-scale IVCW systems were built to evaluate purification efficiencies, microbial community structure and enzyme activities. The results showed that mean removal efficiencies were 81.03 % for COD, 51.66 % for total nitrogen (TN), 42.50 % for NH 4 +-N, and 68.01 % for TP. Significant positive correlations between nitrate reductase activities and TN and NH 4 +-N removal efficiencies, along with a significant correlation between substrate enzyme activity and operation time, were observed. Redundancy analysis demonstrated gram-negative bacteria were mainly responsible for urease and phosphatase activities, and also played a major role in dehydrogenase and nitrate reductase activities. Meanwhile, anaerobic bacteria, gram-negative bacteria, and saturated FA groups, gram-positive bacteria exhibited good correlations with the removal of COD ( p?=?0.388), N ( p?=?0.236), and TP ( p?=?0.074), respectively. The IVCW system can be used to treat domestic wastewater effectively. 相似文献
19.
Nitric acid and ammonium-containing particulate species were measured by the annular denuder-filter pack technique at Manndorf, a rural site in South Germany, in July 1990. The analyses of filter packs indicated that nitrate was present as ammonium salt which mostly dissociated during sampling. Moreover, due to the NH +4/NO −3 ratios higher than unity found in back-up filters, NH 4Cl was assumed to represent an appreciable fraction of the total particulate ammonium. Finally, the molar ratios NH +4/SO 2−4 found on front (Teflon) filters, suggested a large predominance of (NH 4) 2SO 4 among the different forms of sulphate. The concentration levels of gaseous HNO 3 observed in the daytime were characterised by a maximum after midday, whereas particulate nitrate showed five times out of eight days an opposite trend with early afternoon minima. The total nitrate (HNO 3+NH 4NO 3) showed in turn a diurnal pattern similar to that of sulphate. These findings led to the conclusion that a significant HNO 3 production pathway involved the thermal dissociation of NH 4NO 3 rather than the reaction of NO 2 with OH radical. 相似文献
20.
Short-term increases in soil solution nitrate (NO 3−) concentration are often observed after forest harvest, even in N-limited systems. We model NO 3− leaching below the rooting zone as a function of site productivity. Using national forest inventories and published estimates of N attenuation in rivers and the riparian zone, we estimate effects of stem-only harvesting on NO 3− leaching to groundwater, surface waters and the marine environment. Stem-only harvesting is a minor contributor to NO 3− pollution of Swedish waters. Effects in surface waters are rapidly diluted downstream, but can be locally important for shallow well-waters as well as for the total amount of N reaching the sea. Harvesting adds approximately 8 Gg NO 3-N to soil waters in Sweden, with local concentrations up to 7 mg NO 3-N l −1. Of that, ∼3.3 Gg reaches the marine environment. This is ∼3% of the overall Swedish N load to the Baltic. 相似文献
|