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1.
A fragment constant QSAR model for evaluating the EC50 values of organic chemicals to Daphnia magna.
Shu Tao Xiaohuan Xi Fuliu Xu Bengang Li Jun Cao R Dawson 《Environmental pollution (Barking, Essex : 1987)》2002,116(1):57-64
The quantitative relationship between the median effective concentration (EC50) of organic chemicals to Daphnia magna and the number of molecular fragments was investigated based on experimental EC50 values for 217 chemicals derived from the literature. A fragment constant model was developed based on a multivariate linear regression between the number of fragments and the logarithmically transformed reciprocal values of EC50. Functional correction factors were introduced into the model. The model was verified using an independent set of randomly selected data. The mean residual of the final model was 0.4 log-units. The robustness of the model was discussed based on the results of three jackknife tests. 相似文献
2.
炼油厂污水处理负荷的削减措施 总被引:1,自引:0,他引:1
总结和分析了某厂削减污水处理负荷的主要措施及效益,预测该厂在达到16000kt/a以上加工规模时的污水处理负荷。 相似文献
3.
L. Jeffrey Lefkoff Donald R. Kendall 《Journal of the American Water Resources Association》1996,32(3):451-463
ABSTRACT: A non-linear optimization model is applied to the California State Water Project (SWP) and portions of the Central Valley Project (CVP). The model accounts for the major hydrologic, regulatory, and operational features of both projects. The model maximizes long-term SWP yields over a 70-year period, using a quarterly time step. The potential for increased yield associated with a proposed facility improvement is evaluated with the model. The proposed facility is an extension of the Folsom-South Canal, which would allow water to be conveyed from the American River below Folsom Reservoir into New Melones Reservoir on the Stanislaus River or into the California Aqueduct. Model results indicate that extension of the Folsom-South Canal has the potential to increase SWP yields by 13 percent. 相似文献
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Using resource-monitoring data from seven protected areas, the effectiveness of three campfire policies—campfire ban, designated campfires, and unregulated campfires—were assessed based on the number of fire sites and the amount of tree damage. Results indicate that unregulated campfire policies permitted substantial numbers of fire sites and tree damage in campsites, although fire bans did not eliminate or even substantially decrease these problems. A designated campfire policy was effective in decreasing number of fire sites, but little difference was found among policies regarding tree damage. Given the importance of campfires to visitor experiences, campfire prohibitions could be viewed as unnecessarily restrictive based on their limited success in preventing resource damage. Conclusions encourage protected-area managers to consider designated campfire policies and prohibitions on axes, hatchets, and saws to better meet resource protection and visitor experience mandates. 相似文献
7.
VanWoert ND Rowe DB Andresen JA Rugh CL Fernandez RT Xiao L 《Journal of environmental quality》2005,34(3):1036-1044
Urban areas generate considerably more stormwater runoff than natural areas of the same size due to a greater percentage of impervious surfaces that impede water infiltration. Roof surfaces account for a large portion of this impervious cover. Establishing vegetation on rooftops, known as green roofs, is one method of recovering lost green space that can aid in mitigating stormwater runoff. Two studies were performed using several roof platforms to quantify the effects of various treatments on stormwater retention. The first study used three different roof surface treatments to quantify differences in stormwater retention of a standard commercial roof with gravel ballast, an extensive green roof system without vegetation, and a typical extensive green roof with vegetation. Overall, mean percent rainfall retention ranged from 48.7% (gravel) to 82.8% (vegetated). The second study tested the influence of roof slope (2 and 6.5%) and green roof media depth (2.5, 4.0, and 6.0 cm) on stormwater retention. For all combined rain events, platforms at 2% slope with a 4-cm media depth had the greatest mean retention, 87%, although the difference from the other treatments was minimal. The combination of reduced slope and deeper media clearly reduced the total quantity of runoff. For both studies, vegetated green roof systems not only reduced the amount of stormwater runoff, they also extended its duration over a period of time beyond the actual rain event. 相似文献
8.
碳质气溶胶是细颗粒物(PM2.5)的重要组成部分,可影响全球气候变化、大气能见度、区域空气质量和人类健康. 为了探究减排背景下碳质气溶胶的长期变化特征,通过实时在线监测获取了2018~2021年成都市PM2.5样品中的有机碳(OC)、元素碳(EC)、挥发性有机物(VOCs)浓度以及相应的气象数据. 结果表明,监测期间ρ(OC)和ρ(EC)均值分别为(10.9 ±5.7)μg·m-3和(2.6 ±1.9)μg·m-3,在PM2.5中占比分别为25.2%和6.0%,ρ(SOC)均值为(5.7 ±3.3)μg·m-3,在OC中的占比为52.9%. OC和EC浓度随PM2.5年际变化趋势一致,2018~2020年呈下降趋势[PM2.5:年均下降浓度为-7.1 μg·(m3·a)-1,年均降幅为-14.6 %·a-1;OC:年均下降浓度为-1.7 μg·(m3·a)-1,年均降幅为-14.2 %·a-1;EC:年均下降浓度为-0.1 μg·(m3·a)-1,年均降幅为-4.4 %·a-1],2021年各污染物浓度较2020年均有不同幅度反弹. PM2.5和OC浓度大小为:冬>春>秋>夏,EC浓度大小为:冬>秋>春>夏,OC和EC占比分别呈夏季和秋季高于其他季节,对应季节OC和EC占比分别为26.8%和6.9%. 随着污染程度的加重,OC、EC和SOC浓度逐步上升,但在PM2.5中的占比却呈下降趋势,说明成都市PM2.5污染的控制因子并不是碳组分. 源解析结果表明,成都市碳质气溶胶主要受机动车、工业源、生物质燃烧源、VOCs二次转化影响. 2019~2021年,EC受VOCs中机动车特征组分影响逐年下降,春季和秋季OC和EC受VOCs影响大于其他季节,春秋季节应加大VOCs排放治理,减少二次转化影响. 相似文献
9.
陶黎 《生态与农村环境学报》1995,(2)
对内蒙古草原区典型草原不同区域内土壤氟水平及分布规律进行了研究。结果表明,典型草原土壤氟含量从东到西呈上升趋势,典型草原土壤表层氟含量平均值为285.46mg/kg,与国内外有关文献值相比属中等水平,处于内蒙古土壤表层氟背景值范围内。 相似文献
10.
环境管理、规划管理与项目管理 总被引:1,自引:0,他引:1
文章从深入分析环境管理的内涵出发,进而提出树立项目管理意识,强化项目管理的概念,说明项目管理在环境管理中的地位和作用,从这个意义上讨论环境管理与项目管理的关系,简述环境保护项目管理的主要环节,达到提高环境管理效能的途径的目的。 相似文献