网格划分参数对城市街谷行人温湿风模拟的影响——以ENVI-met为例

在基于ENVI-met的城市微气候模拟中,存在计算量与网格划分精度权衡问题。本文以高宽比H/W=1的街谷为例,开展计算域的水平网格分辨率（r）、垂直网格伸缩率（k）、嵌套网格数量（n）3个网格划分参数的选择对行人呼吸面计算结果的影响分析。结果表明：首先,在3个参数中,r的合理设置使计算效率提升最显著,应优先考虑r的取值,r取2m×2 m最适宜,比1 m×1 m的设置快5倍,仅带来较小的计算差异;其次,k取25%最适宜,带来较小偏差的同时节省约1/5的计算时间;最后,计算时间随着n的增加而减小,但差异越来越大,n>4时,差异增幅更大,建议n值取4,差异较小且可提升1倍计算效率。     

Impact of artificial waterfall using reclaimed water to VOCs and its health risk assessment

To study the impact of an artificial waterfall using reclaimed water on volatile organic compounds （VOCs） in air, air samples around the waterfall sight and over the CASS pond of a wastewater treatment plant were collected and VOCs were analyzed by MC-MS with USEPA Method TO-14. The total volatile organic compounds （TOVCs） concentration of a background sample is 2112 μg/m^3, and the sample over the CASS pond has a TVOC concentration of 1858μg/m^3. The TVOC concentrations of air samples within 10 m of the artificial waterfall are between 3216 μg/m^3 and 6362 μg/m^3, which are 1.52 - 3.0 times that of the background sample. The VOCs in air sample impacted by reclaimed water or waste water exhibit a relatively high proportion of toluene but low proportion of benzene. B/T/E/X （ Benzene/Toluene/Ethylbenzene/Xylene ） ratio of the air sample around the artificial water fall is（O. 36/11.78/1/1.10）. Health risk assessment （HRA） was done with the USEPA four-step approach. The result indicates that the artificial waterfall using reclaimed water indeed leads to the increase of human risk value. The total risk value of the sample around the waterfall is 2. 8 - 1.6 times that of the background sample. However, the total risk value of the air sample around the waterfall （2. 8 × 10^-6 ） for common people is still lower,compared to the acceptable public risk level（ 10^-5 ）. For occupational workers of the wastewater treatment plant, the sum of lifetime non-carcinogenic and carcinogenic risk values （ 1.26 × 10^ -5 ） is higher than that of the acceptable public risk level.     

炸药的多相界面环境行为与归趋研究进展

以三硝基甲苯(TNT)、环三亚甲基三硝胺(RDX)和环四亚甲基四硝胺(HMX)为代表的含能化合物具有较强的毒性,进入环境后会在土壤?水体?生物体系中发生复杂的再分配和迁移转化,并危害生态系统和人类健康。在总结国内外场地含能化合物污染现状的基础上,综述了土壤中TNT、RDX和HMX三种炸药溶解/沉淀、挥发、吸附/解吸、光解、水解、还原、微生物降解以及被植物吸收和转化等环境行为的研究进展,分析了炸药和土壤的物理化学性质以及场地环境条件对这些复杂环境行为的影响,并简要介绍了六硝基六氮杂异伍兹烷(CL?20)等新型炸药环境行为的最新研究成果。综合国内外研究现状,建议进一步加强对海洋弹药污染以及含能化合物与重金属复合污染效应的研究,并注重应用单体同位素等最新技术研究炸药的环境行为和归趋。