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161.
Min Xu Zirui Liu Bo Hu Guangxuan Yan Jianan Zou Shuman Zhao Jingxiang Zhou Xianhui Liu Xueping Zheng Xiaoyan Zhang Jing Cao Mengshuang Guan Yirong Lv Yanyun Zhang 《环境科学学报(英文版)》2022,34(5):265-276
Luoyang is a typical heavy industrial city in China, with a coal-dominated energy structure and serious air pollution. Following the implementation of the clean air actions, the physicochemical characteristics and sources of PM2.5 have changed. A comprehensive study of PM2.5 was conducted from October 16, 2019 to January 23, 2020 to evaluate the effectiveness of previous control measures and further to provide theory basis for more effective policies in the future. Results showed that the aerosol pollution in Luoyang in autumn and winter is still serious with the average concentration of 91.1 μg/m3, although a large reduction (46.9%) since 2014. With the contribution of nitrate increased from 12.5% to 25.1% and sulfate decreased from 16.7% to 11.2%, aerosol pollution has changed from sulfate-dominate to nitrate-dominate. High NO3−/SO42− ratio and the increasing of NO3−/SO42− ratio with the aggravation of pollution indicating vehicle exhaust playing an increasingly important role in PM2.5 pollution in Luoyang, especially in the haze processes. Secondary inorganic ions contributed significantly to the enhancement of PM2.5 during the pollution period. The high value of Cl−/Na+ and EC concentration indicate coal combustion in Luoyang is still serious. The top three contributor sources were secondary inorganic aerosols (33.3%), coal combustion (13.6%), and industrial emissions (13.4%). Close-range transport from the western and northeastern directions were more important factors in air pollution in Luoyang during the sampling period. It is necessary to strengthen the control of coal combustion and reduce vehicle emissions in future policies. 相似文献
162.
The impact of reducing industrial emissions of volatile organic compounds (VOCs) on ozone (O3) pollution is of wide concern particularly in highly industrialized megacities. In this study, O3, nitrogen oxides (NOx) and VOCs were measured at an urban site in the Pearl River Delta region during the 2018 Chinese National Day Holidays and two after-holiday periods (one with ozone pollution and another without). O3 pollution occurred throughout the 7-day holidays even industrial emissions of VOCs were passively reduced due to temporary factory shutdowns, and the toluene to benzene ratios dropped from ∼10 during non-holidays to ∼5 during the holidays. Box model (AtChem2-MCM) simulations with the input of observation data revealed that O3 formation was all VOC-limited, and alkenes had the highest relative incremental reactivity (RIR) during the holiday and non-holiday O3 episodes while aromatics had the highest RIR during the non-pollution period. Box model also demonstrated that even aromatics decreased proportionally to levels with near-zero contributions of industrial aromatic solvents, O3 concentrations would only decrease by less than 20% during the holiday and non-holiday O3 episodes and ozone pollution in the periods could not be eliminated. The results imply that controlling emissions of industrial aromatic solvents might be not enough to eliminate O3 pollution in the region, and more attention should be paid to anthropogenic reactive alkenes. Isoprene and formaldehyde were among the top 3 species by RIRs in all the three pollution and non-pollution periods, suggesting substantial contribution to O3 formation from biogenic VOCs. 相似文献
163.
Vapor wall losses can affect the yields of secondary organic aerosol. The effects of surface-to-volume (S/V) ratio and relative humidity (RH) on the vapor-wall interactions were investigated in this study. The oxygenated volatile organic compounds (OVOCs) were generated from toluene-H2O2 irradiations. The average gas to wall loss rate constant (kgw) of OVOCs in a 400 L reactor (S/V = 7.5 m−1) is 2.47 (2.41 under humid conditions) times higher than that in a 5000 L reactor (S/V = 3.6 m−1) under dry conditions. In contrast, the average desorption rate constant (kwg) of OVOCs in 400 L reactor is only 1.37 (1.20 under humid conditions) times higher than that in 5000 L reactor under dry conditions. It shows that increasing the S/V ratio can promote the wall losses of OVOCs. By contrast, the RH effect on kgw is not prominent. The average kgw value under humid conditions is almost the same as under dry conditions in the 400 L (5000 L) reactor. However, increasing RH can decrease the desorption rates. The average kwg value under dry conditions is 1.45 (1.27) times higher than that under humid conditions in the 400 L (5000 L) reactor. The high RH can increase the partitioning equilibrium timescales and enhance the wall losses of OVOCs. 相似文献
164.
165.
水库溃坝损失及其计算方法研究 总被引:7,自引:1,他引:6
主要研究水库渍坝损失及其计算方法.分析了水库溃坝及其损失的特点,提出了溃坝洪水淹没损失的直接经济损失的实物型损失与收益型损失、间接经济损失、非经济损失的内容及其计算方法,并探讨了库区坍岸损失与清决工程损失计算方法. 相似文献
166.
BURAK K. PEKIN 《Conservation biology》2013,27(6):1439-1448
Although agricultural intensification is thought to pose a significant threat to species, little is known about its role in driving biodiversity loss at regional scales. I assessed the effects of a major component of agricultural intensification, agricultural chemical use, and land‐cover and climatic variables on butterfly diversity across 81 provinces in Turkey, where agriculture is practiced extensively but with varying degrees of intensity. I determined butterfly species presence in each province from data on known butterfly distributions and calculated agricultural chemical use as the proportion of agricultural households that use chemical fertilizers and pesticides. I used constrained correspondence analyses and regression‐based multimodel inference to determine the effect of environmental variables on species composition and richness, respectively. The variation in butterfly species composition across the provinces was largely explained (78%) by the combination of agricultural chemical use, particularly pesticides, and climatic and land‐cover variables. Although overall butterfly richness was primarily explained by climatic and land‐cover variables, such as the area of natural vegetation cover, threatened butterfly richness and the relative number of threatened butterfly species decreased substantially as the proportion of agricultural households using pesticides increased. These findings suggest that widespread use of agricultural chemicals, or other components of agricultural intensification that may be collinear with pesticide use, pose an imminent threat to the biodiversity of Turkey. Accordingly, policies that mitigate agricultural intensification and promote low‐input farming practices are crucial for protecting threatened species from extinction in rapidly industrializing nations such as Turkey. Efectos del Uso Extensivo de Agroquímicos sobre la Diversidad de Mariposas en Provincias Turcas 相似文献
167.
长江三峡花岗岩地区土壤流失时间分布特性 总被引:5,自引:1,他引:4
长江三峡花岗岩地区坡面土壤流失以耕地砂砾化面蚀和有部分植物覆盖坡面的鳞片状面蚀为主,该地土壤流失研究结果表明,由以上两类面蚀导致的土壤流失量月分布与月降雨量的分布基本趋势一致,二者呈现较为明显的线性相关关系。地面坡度>30°的裸地土壤流失量达5000t/km3·a以上,覆盖度≥0.70的林地土壤流失量<500t/km2·a,该流域土壤流失量为1544.14t/km2·a,产沙量为694.86t/km2·a 相似文献
168.
Daphnia magna, a freshwater microcrustacean, is currently tested as an alternative experimental species in research dealing with nerve agents poisonings treatment. Because of this, the toxicity of the nerve agent tabun (a cyanide-group containing organophosphate) to Daphnia had to be examined by estimating the EC50 values. The immobilization of daphnids was chosen as the end-point. It was found that D. magna is sensitive to small amounts of tabun, even after 15 min exposure, and tabun toxicity increases with time. The estimated EC50 values for 15, 30, 45, and 60 min exposure were as follows: 67.39, 38.10, 26.95, and 21.9 μg l-1. In addition, the toxicity of media to which tabun was added 24 h before the start of experiments was examined. The results obtained indicate that daphnids can be used in experiments with nerve-agent intoxication treatment. 相似文献
169.
介绍两种震害损失估算方法 总被引:1,自引:0,他引:1
本文介绍了两种震害损失估算方法:全概率法和单位面积法。并据此法对宁夏、青海等地震害作了估算。 相似文献
170.
震后灾害损失快速评估 总被引:6,自引:0,他引:6
本文论述了震后灾害损失快速评估的三种方法,分别适用于城市、整个受灾区及农村。文中还提供了一系列平均统计数据,如建筑物震害率,平均损失率等,为当地无详细资料时参考使用。并以地震烈度和人口密度为参数,给出快速评估人员伤亡的经验公式。最后还讨论了地震间接损失的估算方法。 相似文献