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161.
利用Model-3/CMAQ及京津冀地区高分辨率排放源清单,选取文献[19]中污染峰值当天启动50%污染源削减方案的同时,进一步设置了3种污染源控制方案(峰值当天启动75%源削减;峰值日前1d、2d开始启动25%源削减),比较了峰值日前启动适量减排与峰值日当天启动大幅度减排的效果差异.结果表明:污染峰值当天启动50%、75%减排时,北京市PM2.5浓度下降率分布不均匀,高值区集中于PM2.5浓度高值区,减排后PM2.5浓度分布较减排前均匀.提前1~2d启动25%源削减时,峰值日北京市PM2.5浓度整体下降.城、郊PM2.5下降率均表现为当天减排50%小于提前1d开始减排25%;当天启动减排提高到75%时,城区PM2.5下降率大于提前2d启动25%减排,郊区表现为峰值前2d启动25%削减优于当天减排75%.将峰值前1d、2d启动25%减排分别与当天启动50%、75%减排时北京市峰值日PM2.5浓度下降率相减,北京市绝大部分区域下降率差值为正;峰值前1d、2d启动25%减排分别比峰值日启动50%、75%减排时北京市平均PM2.5多下降4.7μg/m3(6%)、2.9μg/m3(4%).综上所述,在污染峰值来临之前采取适量减排较污染当天才启动大幅度减排更有利于北京市整体空气质量达标. 相似文献
162.
A combined nitritation–anammox reactor was developed to treat the digestion supernatant under various C/N ratios. Due to the difficulties for heterotroph to utilize the refractory organics, the reactor presented relatively stable performance with increasing supernatant addition. Nevertheless, the adverse effects of supernatant would accumulate during the long-term operation and thus weakened the activity and shock resistance of microbes,which further led to the gradual decrease of reactor performance after 92 days' operation.Under this circumstance, supernatant with volatile fatty acids(VFAs) residuals was further introduced into the reactor to investigate the performance of combined nitritation–anammox process with VFA addition. With the appearance of VFAs, the nitrogen removal performance gradually restored and the reactor finally achieved stable and efficient performance with C/N ratio of 0.35. The VFA residuals within 150 mg/L in the supernatant served as the extra electron donors and stimulated the heterotrophic denitrification process, which was vital for the enhancement of reactor. The nitrogen removal rate and total nitrogen removal efficiency reached 0.49 kg N/(m3·day) and 88.8% after 140 days' operation, respectively. The combined nitritation–anammox reactor was proved suitable to treat digestion supernatant. 相似文献
163.
利用09年夏季在黄山光明顶气象站采集的25个云雾水样本及气象站常规资料,分析了云雾过程雾水的化学特征、污染来源与微物理特性.结果表明,观测期间云雾水呈弱酸性,平均值pH值为6.4,主要的离子浓度由大到小排列为:SO42->NH4+>Ca2+>NO3->Na+>Cl-,表明二次污染物对黄山云雾水的贡献较大.统计分析显示,各云雾过程中雾水组分变化,主要缘于不同云雾过程中污染源与海洋源的贡献率不同.结合后向轨迹进一步分析显示,影响气团主要来源于海洋和周边地区,不同气团影响下雾水离子组分及云雾微物理特征差别明显. 相似文献
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167.
Mary Ann Thomas 《Journal of the American Water Resources Association》2000,36(5):1023-1038
ABSTRACT: Two water‐quality studies were done on the outskirts of the Detroit metropolitan area to determine how recent residential development has affected ground‐water quality. Pairs of monitor and domestic wells were sampled in areas where residential land use overlies glacial outwash deposits. Young, shallow waters had significantly higher median concentrations of nitrate, chloride, and dissolved solids than older, deeper waters. Analysis of chloride/bromide ratios indicates that elevated salinities are due to human activities rather than natural factors, such as upward migration of brine. Trace concentrations of volatile organic compounds were detected in samples from 97 percent of the monitor wells. Pesticides were detected infrequently even though they are routinely applied to lawns and roadways in the study area. The greatest influence on ground‐water quality appears to be from septic‐system effluent (domestic sewage, household solvents, water‐softener backwash) and infiltration of storm‐water runoff from paved surfaces (road salt, fuel residue). No health‐related drinking‐water standards were exceeded in samples from domestic wells. However, the effects of human activities are apparent in 76 percent of young waters, and at depths far below 25 feet, which is the current minimum well‐depth requirement. 相似文献
168.
Ionic liquid (IL) mixtures are promising because they can optimize the involved properties according to industrial needs. It has already been demonstrated that IL flammability is due mainly to IL decomposition generating flammable substances. Four different ILs, 1-Butylimidazolium tetrafluoroborate ([BIM][BF4]), 1-butylimidazolium nitrate ([BIM][NO3]), 1-butyl-3-methylimidazolium tetrafluoroborate([BMIM][BF4]), and 1-butyl-3-methylimidazolium nitrate ([BMIM][NO3]), were selected as the parent salts to form the different imidazolium-based IL binary mixtures. These mixtures were tested via isothermal thermogravimetric analyzer (TGA) at different temperatures (120, 150, 180, 210, and 240 °C), then tested by the flash point analyzer after isothermal heating pretreatment at the above temperatures. Results show that the mixtures' flash point values decrease with the heating temperature increase. Vaporization of the IL mixtures’ decomposition products results in a higher concentration of flammable gases and a flash point decrease, which lead to the flammability hazard increasing. Moreover, results show that the flash points of the studied binary imidazolium IL mixtures are more similar to those of the more unstable IL in their parent ILs. Also, the flammability hazard of IL binary mixtures may obviously increase under the high temperature environment for a long time. 相似文献
169.
采用一步法分别合成了1,1,3,3-四甲基胍辛二酸盐离子液体([TMG][SUB])和1,1,3,3-四甲基胍聚乙二醇二羧酸盐离子液体([TMG][PBE]),并采用浸渍法将其分别固载到硅胶上,制备了2种硅胶固载胍盐离子液体脱硫材料(固载材料)。对离子液体和固载材料进行了表征,并考察了固载材料对SO2的吸附性能和再生性能。实验结果表明:固载材料对SO2的吸附发挥了离子液体和硅胶的协同作用,离子液体结构中的醚基基团可促进固载材料对SO2的吸附;在固载比为0.2∶1时,所制备的固载材料[TMG][PBE]-SiO2的SO2饱和吸附量为1.22 g/g(以离子液体计,下同),[TMG][SUB]-SiO2的SO2饱和吸附量为1.01 g/g,均大于纯离子液体,且[TMG][PBE]-SiO2的再生性能更好。 相似文献
170.
沉积物重金属污染及其生态风险评估日益受到关注,而沉积物质量基准是开展生态风险评估的有力工具。本研究通过物种敏感度分布法(species sensitivity distributions, SSD)和急慢性毒性比(acute to chronic ratios, ACR)推导了镍、铜、锌、镉和铅的沉积物质量基准(sediment quality guideline, SQG)。在获得合理的重金属沉积物慢性毒性数据的基础上,采用S-Logistic模型拟合镍、铜、镉和铅的慢性SSD曲线,采用S-Gompertz模型拟合锌的慢性SSD曲线。得到镍、铜、锌、镉和铅沉积物质量基准低值(sediment quality guideline low value, SQGlow)分别为18.6、69.9、107、1.26和38.4 mg·kg~(-1),应用ACRs,得到相应的沉积物质量基准高值(sediment quality guideline high value, SQGhigh)分别为167、226、556、10.1和384 mg·kg~(-1)。与加拿大和澳大利亚重金属沉积物基准值具有一定的可比性。选择花翅摇蚊(Chironomus kiiensis)、伸展摇蚊(Chironomus tentans)和霍甫水丝蚓(Limnodrilus hoffmeisteri)3种底栖生物作为受试生物,验证基准值对海河流域沉积物重金属毒性的预测能力。结果表明,利用SQGs预测沉积物毒性的总准确率为76.2%,3种底栖生物验证准确率从高至低为:花翅摇蚊>伸展摇蚊>霍甫水丝蚓。 相似文献