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241.
矿化垃圾(稳定化垃圾)是一种良好的生物介质,可作为生物反应床的填料处理NOX废气。实验室研究表明,稳定化垃圾反应床可有效地处理NOX气体,其硝化能力(以N计)可达0.83g/(kg·d)(干重)。NOX去除率受停留时间的影响显著,NOX去除率随着停留时间的缩短而降低。当空床停留时间为1.5min时,NOX气体的平均去除率为76.7%;空床停留时间为15min时,NOX气体的平均去除率为91.0%。在NOX进气负荷低于110mmol/(m3·h)时,NOX消除能力随进气负荷的增加而线性增加。当进气流量一定时,NOX去除能力随着进气NOX浓度的增加而线性增加。 相似文献
242.
R. Rai M. Agrawal S.B. Agrawal 《Atmospheric environment (Oxford, England : 1994)》2007,41(40):9543-9554
The present study deals with the evaluation of effects of ambient gaseous air pollution on wheat (Triticum aestivum L. var. HUW-234) growing in a suburban area situated in eastern Gangetic plain of India, using open top chambers. Eight hourly air monitoring was conducted for ambient concentrations of SO2, NO2 and O3 in filtered chambers (FCs), non-filtered chambers (NFCs) and open plots (OPs). Various morphological, physiological and biochemical parameters were assessed during different developmental stages and finally yield parameters were quantified at the time of harvest.Mean concentrations of SO2, NO2 and O3 were 8.4, 39.9 and 40.1 ppb, respectively during the experiment in NFCs. Concentrations of SO2, NO2 and O3 reduced by 74.6%, 84.7% and 90.4%, respectively in FCs as compared to NFCs. Plants grown in FCs showed higher photosynthetic rate, stomatal conductance, chlorophyll content and Fv/Fm ratio as compared to the plants in NFCs and OPs. Lipid peroxidation, proline, total phenol and ascorbic acid contents and peroxidase activity were higher in plants grown in NFCs. There were improvements in morphological parameters of plants growing in FCs as compared to those in NFCs and OPs. Yield of plants also increased significantly in FCs as compared to those ventilated with ambient air (NFCs) or grown in OPs. During the vegetative phase, NO2 concentrations were higher than O3, but O3 became dominant pollutant during the time of grain setting and filling. The study concludes that O3 and NO2 are the main air pollutants in the sub-urban areas causing significant yield reductions in tropical wheat plants. 相似文献
243.
Xiaodong Zou Zhemin Shen Tao Yuan Shan Yin Jingping Cai Liping Chen Wenhua Wang 《Atmospheric environment (Oxford, England : 1994)》2006,40(40):8068-8073
In this paper, a shifted power-law model, based on the wind profile model, had been supposed to simulate concentration gradient of nitrogen dioxide (NO2) with distance from a highway. Field experiments were performed for NO2 gradients from a highway in Shanghai by using passive samplers. The shifted power-law model was fitted well with experimental results of field experiments both in this study and in the literature. The results not only verified the validity of shifted power-law relationship between NO2 concentration and the distance from a highway, but also partially demonstrated that there were some significant similarities between wind profile and air pollutants concentration profile near highway. With known concentration of chosen reference point and appropriate value of the parameter k, the model could be practically applied for predicting the NO2 distributions near a highway. The methods of determining the parameter k were also discussed for further detailed studies. 相似文献
244.
对ABR反应器的水力流态进行了示踪剂试验,分析了特征截面面积对ABR水力特性的影响,采用停留时间分布(RTD)法研究了不同进水COD浓度和HRT条件下ABR反应器的水力特性,结果表明:不同进水COD浓度时ABR反应器的RTD曲线相似,表明进水COD浓度不是影响ABR水力特性的主要因素;不同HRT条件下RTD曲线差异很大,表明HRT对ABR的水力特性影响较大,随着水力停留时间的延长,Ⅳ值增大,1/Pe减小,ABR的流态趋于推流流态,随着HRT的缩短,Ⅳ值减小,1/Pe数增大,ABR反应器趋于完全混合流态。 相似文献
245.
Patrick Martinez Donald K. Brandvold 《Atmospheric environment (Oxford, England : 1994)》1996,30(24):4177-4182
This research consists of a laboratory study and a field study. The laboratory research reports the formation of NOx from a point to plane corona discharge. Discharge polarity and relative humidity determined the amount of NOx that was produced. The positive point discharge caused more NOx to form than the negative point discharge. For both polarities NOx production showed a nonlinear increase with current. Relative humidity enhanced the NOx formation for both polarities. In each case, the amount of NOx formed was comparable to the quantity of N2O produced from corona discharge. The research also reports the results from a field study that measured the amounts of 03 and NO2 produced by corona discharge during a thunderstorm. The study found that the ambient concentrations of 03 and NO2 increased several fold due to corona discharge and returned to original levels after the thunderstorm. 相似文献
246.
In this paper, we present two years of seasonal nitric oxide (NO), ammonia (NH3), and nitrous oxide (N2O) trace gas fluxes measured in a recovering riparian zone with cattle excluded and adjacent riparian zone grazed by cattle. In the recovering riparian zone, average NO, NH3, and N2O fluxes were 5.8, 2.0, and 76.7 ng N m−2 s−1 (1.83, 0.63, and 24.19 kg N ha−1 y−1), respectively. Fluxes in the grazed riparian zone were larger, especially for NO and NH3, measuring 9.1, 4.3, and 77.6 ng N m−2 s−1 (2.87, 1.35, and 24.50 kg N ha−1 y−1) for NO, NH3, and N2O, respectively. On average, N2O accounted for greater than 85% of total trace gas flux in both the recovering and grazed riparian zones, though N2O fluxes were highly variable temporally. In the recovering riparian zone, variability in seasonal average fluxes was explained by variability in soil nitrogen (N) concentrations. Nitric oxide flux was positively correlated with soil ammonium (NH4+) concentration, while N2O flux was positively correlated with soil nitrate (NO3−) concentration. Ammonia flux was positively correlated with the ratio of NH4+ to NO3−. In the grazed riparian zone, average NH3 and N2O fluxes were not correlated with soil temperature, N concentrations, or moisture. This was likely due to high variability in soil microsite conditions related to cattle effects such as compaction and N input. Nitric oxide flux in the grazed riparian zone was positively correlated with soil temperature and NO3− concentration. Restoration appeared to significantly affect NO flux, which increased ≈600% during the first year following restoration and decreased during the second year to levels encountered at the onset of restoration. By comparing the ratio of total trace gas flux to soil N concentration, we show that the restored riparian zone is likely more efficient than the grazed riparian zone at diverting upper-soil N from the receiving stream to the atmosphere. This is likely due to the recovery of microbiological communities following changes in soil physical characteristics. 相似文献
247.
通过介绍环境空气中二氧化氮的测定方法──自动仪器监测法,对有关问题进行了初步探讨和研究,为正确使用该方法和仪器,确保监测工作的顺利进行提供了依据。 相似文献
248.
249.
Nitrogen in pond sediments is a major water quality concern and can impact the productivity of aquaculture. Dissolved oxygen is an important factor for improving water quality and boosting fish growth in aquaculture ponds, and plays an important role in the conversion of ammonium-nitrogen (NH4+-N) to nitrite-nitrogen (NO2?-N) and eventually nitrate-nitrogen (NO3?-N). A central goal of the study was to identify the best aeration method and strategy for improving water quality in aquaculture ponds. We conducted an experiment with six tanks, each with a different aeration mode to simulate the behavior of aquaculture ponds. The results show that a 36 hr aeration interval (Tc = 36 hr: 36 hr) and no aeration resulted in high concentrations of NH4+-N in the water column. Using a 12 hr interval time (Tc = 12 hr: 12 hr) resulted in higher NO2?-N and NO3?-N concentrations than any other aeration mode. Results from an 8 hr interval time (Tc = 8 hr: 8 hr) and 24 hr interval time (Tc = 24 hr: 24 hr) were comparable with those of continuous aeration, and had the benefit of being in use for only half of the time, consequently reducing energy consumption. 相似文献
250.
The effect of dissolved oxygen concentration on long-term stability of partial nitrification process
Dissolved oxygen (DO) concentration is regarded as one of the crucial factors to influence partial nitrification process. However, achieving and keeping stable partial nitrification under different DO concentrations were widely reported. The mechanism of DO concentration influencing partial nitrification is still unclear. Therefore, in this study two same sequencing batch reactors (SBRs) cultivated same seeding sludge were built up with real-time control strategy. Different DO concentrations were controlled in SBRs to explore the effect of DO concentration on the long-term stability of partial nitrification process at room temperature. It was discovered that ammonium oxidation rate (AOR) was inhibited when DO concentration decreased from 2.5 to 0.5 mg/L. The abundance of Nitrospira increased from 1011.5 to 1013.7 copies/g DNA, and its relative percentage increased from 0.056% to 3.2% during 190 operational cycles, causing partial nitrification gradually turning into complete nitrification process. However, when DO was 2.5 mg/L the abundance of Nitrospira was stable and AOB was always kept at 1010.7 copies/g DNA. High AOR was maintained, and stable partial nitrification process was kept. Ammonia oxidizing bacteria (AOB) activity was significantly higher than nitrite oxidizing bacteria (NOB) activity at DO of 2.5 mg/L, which was crucial to maintain excellent nitrite accumulation performance. 相似文献