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111.
基于卫星遥感与地面监测分析北京大气NO_2污染特征 总被引:5,自引:2,他引:3
分析了1999—2010年北京大气NO2地面质量浓度、2004年以来北京及周边NO2柱浓度的变化.结果表明:1999—2007年来北京大气NO2质量浓度以升高为主.2008年实施奥运空气质量保障措施极大地缓解了北京NO2污染状况,地面质量浓度与垂直柱浓度都出现不同程度的回落.2009年北京大气NO2污染又有所反弹,但低... 相似文献
112.
This work was designed to explore the characteristics of photodegradation of herbicides in the copper-polluted water body. The
results showed that Cu(II) alone could induce a photo Fenton-like reaction to enhance the degradation of atrazine, in which hydroxyl
radical ( OH) was a main active species. Humic acids restrained atrazine degradation, nevertheless, when introducing Cu(II), the
photodegradation was accelerated, in which singlet oxygen (1O2) replaced OH acting as the prevailing species. A feasible mechanism
for the photochemical process was also proposed, which is helpful for better understanding the environmental photochemistry of
atrazine in the copper-polluted water. 相似文献
113.
Seepage from Hg mine wastes and calcines contains high concentrations of mercury (Hg). Hg pollution is a major environmental
problem in areas with abandoned mercury mines and retorting units. This study evaluates factors, especially the hydrological and
sedimentary variables, governing temporal and spatial variation in levels and state of mercury in streams impacted by Hg contaminated
runo . Samples were taken during di erent flow regimes in theWanshan Hg mining area in Guizhou Province, China. In its headwaters
the sampled streams/rivers pass by several mine wastes and calcines with high concentration of Hg. Seepage causes serious Hg
contamination to the downstream area. Concentrations of Hg in water samples showed significant seasonal variations. Periods of
higher flow showed high concentrations of total Hg (THg) in water due to more particles being re-suspended and transported. The
concentrations of major anions (e.g., Cl??, F??, NO3?? and SO4
2??) were lower during higher flow due to dilution. Due to both sedimentation
of particles and dilution from tributaries the concentration of THg decreased from 2100 ng/L to background levels (< 50 ng/L) within
10 km distance downstream. Sedimentation is the main reason for the fast decrease of the concentration, it accounts for 69% and 60%
for higher flow and lower flow regimes respectively in the upper part of the stream. Speciation calculation of the dissolved Hg fraction
(DHg) (using Visual MINTEQ) showed that Hg(OH)2 associated with dissolved organic matter is the main form of Hg in dissolved
phase in surface waters in Wanshan (over 95%). 相似文献
114.
Potassium-modified ceria-zirconia catalyst was synthesized by wetness impregnation method. The ageing treatment was performed in static air at 800℃ for 20 hr to evaluate the thermal stability of the catalyst. The catalysts were characterized by X-ray diffraction,BET surface area, oxygen storage capacity, NOx-temperature programmed desorption and soot-temperature programmed oxidation measurements. By introduction of potassium, the maximum soot oxidation rate temperature (Tm) of the ceria-zirconia based catalyst decreased from 525 to 428℃ in the presence of NO under a loose contact mode. The shift of Tm of the K-modified catalyst after ageing is only 15℃. The enhanced activity of the aged catalyst mainly lies in the promotional effect of potassium on the NOx/oxygen storage cacity as well as the soot-catalyst contact. 相似文献
115.
116.
The nitrogen changes and the nitrogen mass balance in a free water surface flow constructed wetland (CW) using the four-year monitoring data from 2008 to 2012 were estimated. The CW was composed of six cells in series that include the first settling basin (Cell 1), aeration pond (Cell 2), deep marsh (Cell 3), shallow marsh (Cell 4), deep marsh (Cell 5) and final settling basin (Cell 6). Analysis revealed that the NH4+-N concentration decreased because of ammonification which was then followed by nitrification. The NO4+-N and NO4+-N were also further reduced by means of microbial activities and plant uptake during photosynthesis. The average nitrogen concentration at the influent was 37,819 kg/year and approximately 45% of that amount exited the CW in the effluent. The denitrification amounted to 34% of the net nitrogen input, whereas the accretion of sediment was only 7%. The biomass uptake of plants was able to retain only 1% of total nitrogen load. In order to improve the nutrient removal by plant uptake, plant coverage in four cells (i.e., Cells 1, 3, 4 and 5) could be increased. 相似文献
117.
五日生化需氧量是一种表间接表示水体中有机物含量,是水质监测的一个重要参数。本文对水样的保存、溶解氧、pH值、温度、接种稀释水和稀释度等影响测定五日生化需氧量成败的因素进行探讨,并提出相应的解决方法。 相似文献
118.
采用了等体积浸渍法制备二氧化钛负载钒氧化物催化剂(V2O5/TiO2),研究了V2O5负载量、反应温度、烟气流量、氨氮比以及运行时间各因素对NH3选择性催化还原NO反应(SCR)效率的影响.研究结果表明:经过500℃温度下煅烧,烟气流量为200ml/min,负载量为7wt%的V2O5/TiO2催化剂,在400℃温度下反应,NO脱除率可达70.5%. 相似文献
119.
120.
春节期间南京市大气气溶胶粒径分布特征 总被引:15,自引:4,他引:11
为研究春节期间燃放烟花爆竹对城市大气气溶胶数浓度粒径谱分布的影响,对2012年1月19~31日南京大气气溶胶数浓度、污染气体浓度和质量浓度进行了观测分析.结果表明,烟花爆竹的燃放期间10~20 nm气溶胶浓度远低于非燃放期,50~100、100~200和200~500 nm数浓度有较大增加,20~50 nm和0.5~10μm气溶胶数浓度变化不大.烟花爆竹的燃放对气溶胶数浓度谱影响较大,非燃放期数浓度谱为双峰型分布;在燃放期数浓度谱为单峰性分布,且峰值向大粒径段偏移.烟花爆竹燃放期间质量浓度谱为双峰型分布,对细粒子的质量浓度影响较大,燃放期间PM2.5/PM10和PM1.0/PM10的值可升高10%.烟花爆竹的大量燃放对1.0~2.1μm粒径段气溶胶密度影响最大,对其他粒径段密度影响较小. 相似文献