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1.
An automated system for continuous measurement of N 2O fluxes on an hourly basis was employed to study N 2O emissions in an intensively managed low carbon calcareous soil under sub-humid temperate monsoon conditions. N 2O emissions occurred mainly within two weeks of application of NH 4+-based fertilizer and total N 2O emissions in wheat (average 0.35 or 0.21 kg N ha −1 season −1) and maize (average 1.47 or 0.49 kg N ha −1 season −1) under conventional and optimum N fertilization (300 and 50-122 kg N ha −1, respectively) were lower than previously reported from low frequency measurements. Results from closed static chamber showed that N 2O was produced mainly from nitrification of NH 4+-based fertilizer, with little denitrification occurring due to limited readily oxidizable carbon and low soil moisture despite consistently high soil nitrate-N concentrations. Significant reductions in N 2O emissions can be achieved by optimizing fertilizer N rates, using nitrification inhibitors, or changing from NH 4+- to NO 3ˉ-based fertilizers. 相似文献
3.
With the aim of understanding the origin of acid rains in South China, we analyzed rainwaters collected from Guangzhou, China, between March 2005 and February 2006. The pH of rainwater collected during the monitoring period varied from 4.22 to 5.87; acid rain represented about 94% of total precipitation during this period. The rainwater was characterized by high concentrations of SO 42−, NO 3−, Ca 2+, and NH 4+. SO 42− and NO 3−, the main precursors of acid rain, were related to the combustion of coal and fertilizer use/traffic emissions, respectively. Ca 2+ and NH 4+ act as neutralizers of acid, accounting for the decoupling between high SO 42− concentrations and relatively high pH in the Guangzhou precipitation. The acid rain in Guangzhou is most pronounced during spring and summer. A comparison with acid precipitation in other Chinese cities reveals a decreasing neutralization capacity from north to south, probably related to the role and origin of alkaline bases in precipitation. 相似文献
4.
Agricultural soils may account for 10% of anthropogenic emissions of NO, a precursor of tropospheric ozone with potential impacts on air quality and global warming. However, the estimation of this biogenic source strength and its relationships to crop management is still challenging because of the spatial and temporal variability of the NO fluxes.Here, we present a combination of new laboratory- and field-scale methods to characterise NO emissions and single out the effects of environmental drivers.First, NO fluxes were continuously monitored over the growing season of a maize-cropped field located near Paris (France), using 6 automatic chambers. Mineral fertilizer nitrogen was applied from May to October 2005. An additional field experiment was carried out in October to test the effects of N fertilizer form on the NO emissions. The automatic chambers were designed to measure simultaneously the NO and N 2O gases. Laboratory measurements were carried out in parallel using soil cores sampled at same site to test the response of NO fluxes to varying soil N–NH 4 and water contents, and temperatures. The effects of soil core thickness were also analysed.The highest NO fluxes occurred during the first 5 weeks following fertilizer application. The cumulative loss of NO–N over the growing season was estimated at 1.5 kg N ha ?1, i.e. 1.1% of the N fertilizer dose (140 kg N ha ?1). All rainfall events induced NO peak fluxes, whose magnitude decreased over time in relation to the decline of soil inorganic N. In October, NO emissions were enhanced with ammonium forms of fertilizer N. Conversely, the application of nitrate-based fertilizers did not significantly increase NO emissions compared to an unfertilized control. The results of the subsequent laboratory experiments were in accordance with the field observations in magnitude and time variations. NO emissions were maximum with a water soil content of 15% (w w ?1), and with a NH 4–N content of 180 mg NH 4–N kg soil ?1. The response of NO fluxes to soil temperature was fitted with two exponential functions, involving a Q10 of 2.0 below 20 °C and a Q10 of 1.4 above. Field and laboratory experiments indicated that most of the NO fluxes originated from the top 10 cm of soil. The characterisation of this layer in terms of mean temperature, NH 4 and water contents is thus paramount to explaining the variations of NO fluxes. 相似文献
5.
Traffic-generated air pollutant emissions can be classified into exhaust and non-exhaust emissions. Increased attention is focussing on non-exhaust emissions as exhaust emissions are progressively limited by regulations. To characterise metal-rich emission from abrasion processes, size-segregated analysis of atmospheric aerosol particles sampled with micro-orifice uniform deposit impactors (MOUDI) in March 2007 in London was performed. The samples were collected at a roadside and a background site and were analysed for Al, Ba, Cu, Fe, Sb, Ti, V, Zn, Ca 2+, K +, Mg 2+, Na +, and NH 4+. Most components showed a clear roadside increment, which was evident as a higher mass concentration and a change in the size distribution. In particular, Fe, Cu, Ba, and Sb correlated highly, indicative of a common traffic-related source. Using complementary information on the fleet composition, vehicle number and average speed, the brake wear emission was calculated using the EMEP/CORINAIR emission database. The total PM 10 and barium emission of the traffic was determined by ratio to NO x whose source strength was estimated from published emission factors. Barium was found to comprise 1.1% of brake wear (PM 10) particles from the traffic fleet as a whole, allowing its use as a quantitative tracer of brake wear emissions at other traffic-influenced sites. 相似文献
6.
Land use conversion and fertilization have been widely reported to be important managements affecting the exchanges of greenhouse gases between soil and atmosphere. For comprehensive assessment of methane (CH 4) and nitrous oxide (N 2O) fluxes from hilly red soil induced by land use conversion and fertilization, a 14-month continuous field measurement was conducted on the newly converted citrus orchard plots with fertilization (OF) and without fertilization (ONF) and the conventional paddy plots with fertilization (PF) and without fertilization (PNF). Our results showed that land use conversion from paddy to orchard reduced the CH 4 fluxes at the expense of increasing the N 2O fluxes. Furthermore, fertilization significantly decreased the CH 4 fluxes from paddy soils in the second stage after conversion, but it failed to affect the CH 4 fluxes from orchard soils, whereas fertilizer applied to orchard and paddy increased soil N 2O emissions by 68 and 113.9 %, respectively. Thus, cumulative CH 4 emissions from the OF were 100 % lower, and N 2O emissions were 421 % higher than those from the PF. Although cumulative N 2O emissions were stimulated in the newly converted orchard, the strong reduction of CH 4 led to lower global warming potentials (GWPs) as compared to the paddy. Besides, fertilization in orchard increased GWPs but decreased GWPs of paddy soils. In addition, measurement of soil moisture, temperature, dissolved carbon contents (DOCs), and ammonia (NH 4 +-N) and nitrate (NO 3 ?-N) contents indicated a significant variation in soil properties and contributed to variations in soil CH 4 and N 2O fluxes. Results of this study suggest that land use conversion from paddy to orchard would benefit for reconciling greenhouse gas mitigation and citrus orchard cultivation would be a better agricultural system in the hilly red soils in terms of greenhouse gas emission. Moreover, selected fertilizer rate applied to paddy would lead to lower GWPs of CH 4 and N 2O. Nevertheless, more field measurements from newly converted orchard are highly needed to gain an insight into national and global accounting of CH 4 and N 2O emissions. 相似文献
7.
以天然矿物质沸石、细砂及煤渣取代传统滤料构建复合基质生态床,表面种植景观植物,采用下向流-上向流运行方式修复北方景观水体。分别进行静态实验及不同循环速率下的动态实验,考察对水体污染物去除过程。结果表明,2种运行方式下对水体NH +4-N去除率都在85%以上,其中以1 h为循环周期的运行方式去除率达97%,较静态提高12.8%;TN去除率最高为84%;TP去除不稳定,过程缓慢。煤渣层对NH +4-N的去除效果差,硝化作用不彻底与反硝化作用的加强使下层出水NH +4-N 、NO -2-N及NO -3-N浓度均高于上层。提高循环速率有利于对氮的去除。 相似文献
8.
Urine contains about 50 % of the phosphorus (P) and about 90 % of the nitrogen (N) excreted by humans and is therefore an interesting substrate for nutrient recovery. Source-separated urine can be used to precipitate struvite or, through a newly developed technology, nitrified urine fertilizer (NUF). In this study, we prepared 33P radioisotope- and stable 15N isotope-labeled synthetic NUF (SNUF) and struvite using synthetic urine and determined P and N uptake by greenhouse-grown ryegrass ( Lolium multiflorum var. Gemini) fertilized with these products. The P and N in the urine-based fertilizers were as readily plant-available in a slightly acidic soil as the P and N in reference mineral fertilizers. The ryegrass crop recovered 26 % of P applied with both urine-based fertilizers and 72 and 75 % of N applied as struvite and SNUF, respectively. Thus, NUF and urine-derived struvite are valuable N and P recycling fertilizers. 相似文献
9.
Abstract Annual applications of (NH 4) 2SO 4 NH 4NO 3 and urea on a Solonetzic soil at 112 kg N/ha for 10 consecutive years reduced pH levels from 5.6 for the check to 4.4 , 4.9 and 5.3, respectively for (NH 4) 2SO 4, NH 4NO 3 and urea. (NH 4) 2SO 4 generated twice as much exchange acidity as NH 4NO 3 and four times as much as urea. Net extractable cations leached from the Ap horizon closely approximated the amount of exchange acidity generated by (NH 4) 2SO 4 and NH 4NO 3 fertilizers. The levels of soil extractable Al and Mn were greatly enhanced by (NH 4) 2SO 4 as were plant contents. Similar acidifying effects to that produced by the (NH 4) 2SO 4 occurred when NH 4NO 3 was applied at 300 kg N/ha annually for 12 consecutive years in another field experiment on the same soil. Liming samples of the field (NH 4) 2SO 4 acidified soils in the greenhouse, significantly increased yields and lowered the Al and Mn contents of the plants to normal levels. 相似文献
10.
A method is developed to estimate wet deposition of nitrogen in a 11×14 km (0.125°Lon.×0.125°Lat.) grid scale using the precipitation chemistry monitored data at 10 sites scattered over South Korea supplemented by the routinely available precipitation rate data at 65 sites and the estimated emissions of NO 2 and NH 3 at each precipitation monitoring site. This approach takes into account the contributions of local NO 2 and NH 3 emissions and precipitation rates on wet deposition of nitrogen. Wet deposition of nitrogen estimated by optimum regression equations for NO 3− and NH 4+ derived from annual total monitored wet deposition and that of emissions of NO 2 and NH 3 is incorporated to normalize wet deposition of nitrogen at each precipitation rate class, which is divided into 6 classes. The optimum regression equations for the estimation of wet deposition of nitrogen at precipitation monitoring sites are developed using the normalized wet deposition of nitrogen and the precipitation rate at 10 precipitation chemistry monitoring sites. The estimated average annual total wet depositions of NO 3− and NH 4+ are found to be 260 and 500 eq ha −1 yr −1 with the maximum values of 400 and 930 eq ha −1 yr −1, respectively. The annual mean total wet deposition of nitrogen is found to be about 760 eq ha −1 yr −1, of which more than 65% is contributed by wet deposition of ammonium while, the emission of NH 3 is about half of that of NO 2, suggesting the importance of NH 3 emission for wet deposition of nitrogen in South Korea. 相似文献
11.
ABSTRACT The annual average concentrations (1986–1997) of the major ions SO 4 2-, NO 3 -, Cl -, NH 4+, Na+, Mg 2+, Ca 2+, and K+ in precipitation are analyzed for selected EMEP stations. The objective is to determine the ion patterns or typologies in precipitation by principal component analysis (PCA) combined with a cluster analysis. SO 4 2- and NO 3 - ions are predominant in central and eastern Europe. This area corresponds to high emissions of SO 2 and NO 2. Sea spray ions are predominant in coastal sites. The soil components show an important contribution in southern Europe, possibly due to the soil dust transported from northern Africa. 相似文献
12.
Manure-based soil amendments (herein “amendments”) are important fertility sources, but differences among amendment types and management can significantly affect their nutrient value and environmental impacts. A 6-month in situ decomposition experiment was conducted to determine how protection from wintertime rainfall affected nutrient losses and greenhouse gas (GHG) emissions in poultry (broiler chicken and turkey) and horse amendments. Changes in total nutrient concentration were measured every 3 months, changes in ammonium (NH 4+) and nitrate (NO 3?) concentrations every month, and GHG emissions of carbon dioxide (CO 2), methane (CH 4), and nitrous oxide (N 2O) every 7–14 days. Poultry amendments maintained higher nutrient concentrations (except for K), higher emissions of CO 2 and N 2O, and lower CH 4 emissions than horse amendments. Exposing amendments to rainfall increased total N and NH 4+ losses in poultry amendments, P losses in turkey and horse amendments, and K losses and cumulative N 2O emissions for all amendments. However, it did not affect CO 2 or CH 4 emissions. Overall, rainfall exposure would decrease total N inputs by 37% (horse), 59% (broiler chicken), or 74% (turkey) for a given application rate (wet weight basis) after 6 months of decomposition, with similar losses for NH 4+ (69–96%), P (41–73%), and K (91–97%). This study confirms the benefits of facilities protected from rainfall to reduce nutrient losses and GHG emissions during amendment decomposition. Implications: The impact of rainfall protection on nutrient losses and GHG emissions was monitored during the decomposition of broiler chicken, turkey, and horse manure-based soil amendments. Amendments exposed to rainfall had large ammonium and potassium losses, resulting in a 37–74% decrease in N inputs when compared with amendments protected from rainfall. Nitrous oxide emissions were also higher with rainfall exposure, although it had no effect on carbon dioxide and methane emissions. Overall, this work highlights the benefits of rainfall protection during amendment decomposition to reduce nutrient losses and GHG emissions. 相似文献
13.
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 (t 1/2) of diazinon were found 29.3 and 34.8 days respectively in seed and soil treatments. In diazinon seed treatment, NH 4 +, NO 3 ?, and NO 2 ? nitrogen and nitrate reductase activity were not affected. Whereas, diazinon soil treatment indicated significant increase in NH 4 +-N in a 1-day sample, which continued until 90 days. Some declines in NO 3 ?N were found from 15 to 60 days. Along with this decline, significant increases in NO 2 ?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 (t 1/2) 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 NO 3 ?N and the decline in NH 4 +NO 2 ?-N and nitrate reductase enzyme activity were observed between 15 to 90 days. However, lindane seed treatment indicated significant increases in NH 4 +-N, NO 2 ?-N and nitrate reductase activity and some adverse effects on NO 3 ?N between 15 and 90 days. 相似文献
14.
Livestock production and the use of synthetic fertilizer are responsible for about half of the global emission of NH 3. Depending on the animal category between 10 and 36% of the N in animal excreta is lost as NH 3. The current annual NH 3 emission in developing countries of 15 million ton N accounts for of the global emission from animal excreta. In addition, 7.2 million tons NH 3N of synthetic N fertilizers are lost as NH 3 in developing countries. This is 80% of the global NH 3 emission from synthetic fertilizer's use. Along with human population increase and economic growth, livestock production in developing countries may even increase by a factor of 3 between now and 2025. The net result of rapid increase of livestock production combined with higher efficiency is an increase in NH 3 emissions of only 60% from 15 to 24 million tons NH 3N between 1990 and 2025 in developing countries. Livestock production is an important consumer of feedstuffs, mainly cereals, thereby inducing additional demand for synthetic fertilizers. Despite the projected major increase of synthetic fertilizer use from 42 to 106 million ton N between 1990 and 2025, the NH 3 loss in developing countries may decrease if a shift towards other fertilizer types, that are less vulnerable to NH 3 volatilization, is realized. According to the scenario, the total emission of NH 3 associated with food production in developing countries will increase from 22 to 30 million ton N yr −1 between 1990 and 2025. Although the NH 3 emission increases more slowly than food production, in particular, animal production may show geographic concentration in certain regions, which may lead to high local emission densities and associated environmental problems. 相似文献
15.
Increasing application of nitrogen fertilizers in the irrigated lands of the studied area is likely to create a blanket non-point source of nitrate. Groundwater contamination from fertilizers, in this context, has been reported as derived from N0 3−, K + and 180 composition of groundwater. The data suggest both point and non-point sources of groundwater pollution. Thirty-three percent of the groundwater samples showed nitrate contents exceeding the general acceptable limit of 20 p.p.m. and 15% of the samples crossed the maximum permissible limit of 45 p.p.m. High nitrate levels are associated with high δ 18O values, clearly indicating that significant quantities of evaporated (isotopically enriched) irrigation water infiltrate along with fertilizer nitrate to the groundwater system. Different δ 18O--- N0 3− trends suggest isotopically distinct, non-point source origins which vary spatially and temporally, due to different degrees of evaporation/recharge and amounts of fertilizer applied. A scatter diagram of N0 3− vs K + suggests a common source of these ions when the concentration is less than 40 p.p.m. The investigation indicates that a combination of isotope ( 180) and hydrochemical data can clearly characterize the impact of fertilizer on groundwater. Application of high nitrate, high potassium groundwater irrigation can minimize the requirement for inorganic fertilizers and bring down the cost of cultivation considerably, through appropriate management of fertilizer and water and modifications in agronomic practices and strategies on crops grown. Such practices will help protect groundwater from further degradation. 相似文献
16.
Abstract This paper presents measurements of daily sampling of fine particulate matter (PM 2.5) and its major chemical components at three urban and one rural locations in North Carolina during 2002. At both urban and rural sites, the major insoluble component of PM 2.5 is organic matter, and the major soluble components are sulfate (SO 4 2?), ammonium (NH 4 +), and nitrate (NO 3 ?). NH 4 + is neutralized mainly by SO 4 2? rather than by NO 3 ?, except in winter when SO 4 2? concentration is relatively low, whereas NO 3 ? concentration is high. The equivalent ratio of NH 4 + to the sum of SO 4 2? and NO 3 ? is <1, suggesting that SO 4 2?and NO 3 ?are not completely neutralized by NH 4 +. At both rural and urban sites, SO 4 2?concentration displays a maximum in summer and a minimum in winter, whereas NO 3 ?displays an opposite seasonal trend. Mass ratio of NO 3 ? to SO 4 2?is consistently <1 at all sites, suggesting that stationary source emissions may play an important role in PM 2.5 formation in those areas. Organic carbon and elemental carbon are well correlated at three urban sites although they are poorly correlated at the agriculture site. Other than the daily samples, hourly samples were measured at one urban site. PM 2.5 mass concen trations display a peak in early morning, and a second peak in late afternoon. Back trajectory analysis shows that air masses with lower PM 2.5 mass content mainly originate from the marine environment or from a continental environment but with a strong subsidence from the upper troposphere. Air masses with high PM 2.5 mass concentrations are largely from continental sources. Our study of fine particulate matter and its chemical composition in North Carolina provides crucial information that may be used to determine the efficacy of the new National Ambient Air Quality Standard (NAAQS) for PM fine. Moreover, the gas-to-particle conversion processes provide improved prediction of long-range transport of pollutants and air quality. 相似文献
17.
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
18.
Deep percolation of nitrate can contribute to the deterioration of groundwater resources. Leaching of nitrate is a complex process affected by fertilizer and irrigation practices, efficiency of N use by the crop, and how the soil's water holding capacity and water transmission properties are affected by soil texture. Depleted ( 15NH 4) 2SO 4 fertilizer at N rates of 0, 125, 250 and 375 kg ha −1 was applied annually for 3 years to continuous corn grown within three different water regimes. This time period and the labeled N permitted an evaluation of N use efficiency by the crop and NO 3 leaching and carryover on a Weld silty clay loam, a fine-textured soil, typical of the “hardland” soils of the semi-arid Great Plains. Three water regimes, W1 ( 1.5 ET), W2 ( ET) and W3 ( 0.8 ET), were used. Beneath each plot within each water regime, Duke-Haise vacuum trough extractors were installed under undisturbed soil profiles at 1.22-m depth to measure weekly percolate and the NO 3 concentration in the percolate. The corn was harvested in the fall in the dent stage to measure the total above-ground biomass N uptake. Soil profiles (1.8 m) were sampled annually in the fall after crop harvest to determine NO 3---N in the soil or carryover.Great variability was encountered in measuring the amount of extractor water and its NO 3 content under each water regime, which made estimates of N03 leaching losses unreliable. Also, the variability demonstrates formidable problems in quantifying percolation losses with vacuum trough extractors under undisturbed fine-textured soil profiles. With the highest N rate of 376 kg ha −1 yr −1 and within the water regime W 1, where leaching was expected to be greatest, only 1% of the cumulative labeled N applied was found in extractor waters and most movement of the labeled N into extractors occurred the third year. The 125-kg-ha −1 yr −1 fertilizer N rate significantly increased the crop yield over the unfertilized plots without increasing residual NO 3---N accumulation; whereas fertilizer N rates of > 125 kg ha −1 yr −1 did not appreciably increase plant yields over the 125-kg-ha −1-N rate, but did appreciably increase residual NO 3. 相似文献
19.
Animal feeding operations (AFOs) produce particulate matter (PM) and gaseous pollutants. Investigation of the chemical composition of PM 2.5 inside and in the local vicinity of AFOs can help to understand the impact of the AFO emissions on ambient secondary PM formation. This study was conducted on a commercial egg production farm in North Carolina. Samples of PM 2.5 were collected from five stations, with one located in an egg production house and the other four located in the vicinity of the farm along four wind directions. The major ions of NH 4+, Na +, K +, SO 42?, Cl ?, and NO 3? were analyzed using ion chromatography (IC). In the house, the mostly abundant ions were SO 42?, Cl ?, and K +. At ambient stations, SO 42?, and NH 4+ were the two most abundant ions. In the house, NH 4+, SO 42?, and NO 3? accounted for only 10% of the PM 2.5 mass; at ambient locations, NH 4+, SO 42?, and NO 3? accounted for 36–41% of the PM 2.5 mass. In the house, NH 4+ had small seasonal variations indicating that gas-phase NH 3 was not the only major force driving its gas–particle partitioning. At the ambient stations, NH 4+ had the highest concentrations in summer. In the house, K +, Na +, and Cl ? were highly correlated with each other. In ambient locations, SO 42? and NH 4+ had a strong correlation, whereas in the house, SO 42? and NH 4+ had a very weak correlation. Ambient temperature and solar radiation were positively correlated with NH 4+ and SO 42?. This study suggests that secondary PM formation inside the animal house was not an important source of PM 2.5. In the vicinity, NH 3 emissions had greater impact on PM 2.5 formation. ImplicationsThe chemical composition of PM 2.5 inside and in the local vicinity of AFOs showed the impact of the AFO emissions on ambient secondary PM 2.5 formation, and the fate and transport of air pollutants associated with AFOs. The results may help to manage in-house animal facility air quality, and to develop regional air quality control strategies and policies, especially in animal agriculture-concentrated areas. 相似文献
20.
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
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