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721.
介绍了埕岛油田海上固定导管架式平台的振动安全检测方法,重点对振动隐患治理的程序和方法进行了探讨.  相似文献   
722.
中国降水量区域变化稳定性研究   总被引:3,自引:2,他引:1  
利用中国气象中心160站点的实际观察资料,对中国半个世纪的降水变化进行了系统分析,发现中国的夏季降水变化稳定性有显著的纬度与海拔效应:纬度越高,方差值越小,降水变化的幅度也越小,稳定性越大;从海拔来看,海拔越高,降水稳定性越好,降水量的变化稳定性与海拔是成反相关关系.除过受区域水汽来源稳定性的影响,主要受全球降水稳定性的分布规律所制约;在海拔上,降水量稳定性的分布,除过受水汽来源影响外,还与水汽凝结的高度效应有一定的关系.  相似文献   
723.
附着剑菌对三氯联苯的吸附及降解机制研究   总被引:1,自引:0,他引:1  
实验研究附着剑菌(Ensifer adhaerens.R2)对持久性有机污染物三氯联苯(2,4,4′-TCB,PCB28)的去除机制,探究菌株对2,4,4′-TCB的生物吸附和生物降解作用,以及其随时间、pH值、温度、菌体密度、金属离子(Ca2+、Mg2+)的变化.灭活菌体对PCBs的去除机制为生物吸附,吸附率在2h基本达到平衡,为85.97%;活体菌株可以通过生物吸附及生物降解作用去除2,4,4′-TCB,在本次实验周期内主要以吸附作用为主,2h吸附率为60.59%,明显高于降解率的12.90%.单因素条件下,pH值为6.0、35℃、OD为0.8、添加1mol/L的Ca2+、Mg2+处理可使活菌对2,4,4′-TCB的吸附达到最优;pH值为7.5,30℃,添加0.05mol/L的Ca2+、Mg2+处理可使活菌对2,4,4′-TCB的降解达到最优.  相似文献   
724.
贾宁  董欣  宁雄  刘毅 《中国环境科学》2016,36(6):1905-1912
快速的城镇化使城市间距不断减小,上下游城市间水质的相互影响愈发显著.本研究提出基于水质的城市安全距离概念,建立基于BP神经网络水质模型的城市安全距离量化方法,并选择长江沿岸相邻的芜湖、马鞍山两市为案例,评估未来两市建成区扩张后城市间距的安全性,计算两市建成区的最小安全距离.结果显示,2020年芜湖与马鞍山4.6km的间距属于安全距离,能够保证下游城市马鞍山上游控制断面地表II类的水功能要求.但与2010年相比,控制断面水质变差,COD与氨氮浓度分别提高了29.2%与23.2%.为了保证控制断面的水功能要求,芜湖与马鞍山两市的最小安全距离为3.2km.  相似文献   
725.
The quality of cultivated consumed vegetables in relation to environmental pollution is a crucial issue for urban and peri-urban areas, which host the majority of people at the global scale. In order to evaluate the fate of metals in urban soil–plant–atmosphere systems and their consequences on human exposure, a field study was conducted at two different sites near a waste incinerator (site A) and a highway (site B). Metal concentrations were measured in the soil, settled atmospheric particulate matter (PM) and vegetables. A risk assessment was performed using both total and bioaccessible metal concentrations in vegetables. Total metal concentrations in PM were (mg kg?1): (site A) 417 Cr, 354 Cu, 931 Zn, 6.3 Cd and 168 Pb; (site B) 145 Cr, 444 Cu, 3289 Zn, 2.9 Cd and 396 Pb. Several total soil Cd and Pb concentrations exceeded China’s Environmental Quality Standards. At both sites, there was significant metal enrichment from the atmosphere to the leafy vegetables (correlation between Pb concentrations in PM and leaves: r = 0.52, p < 0.05) which depended on the plant species. Total Cr, Cd and Pb concentrations in vegetables were therefore above or just under the maximum limit levels for foodstuffs according to Chinese and European Commission regulations. High metal bioaccessibility in the vegetables (60–79 %, with maximum value for Cd) was also observed. The bioaccessible hazard index was only above 1 for site B, due to moderate Pb and Cd pollution from the highway. In contrast, site A was considered as relatively safe for urban agriculture.  相似文献   
726.
To improve the efficiency of nitrogen removal with lower energy consumption, the study of feedforward control was carried out on a pilot-scale anaerobic-anoxic-oxic (AAO) plant for the treatment of municipal wastewater. The effluent qualities of the pilot plant under different control strategies were investigated. The results indicated that the change of external recycle was not a suitable approach to regulate the sludge concentration of plug-flow reactors; adjusting the aeration valve and dissolved oxygen set-point according to ammonia load could overcome the impact of influent fluctuation; and the denitrification potential could be estimated based on the transit time of anoxic zone and the relative content of carbon resource entering the anoxic zone. Simple feedforward control strategies for aeration and internal recycle were subsequently proposed and validated. The nitrogen removal was successfully improved in the pilot plant. The effluent total nitrogen had decreased by 29.9% and was steadily controlled below 15 mg·L-1. Furthermore, approximately 38% of the energy for aeration had been saved.  相似文献   
727.
Dissolved organic matter (DOM) transformation in sequence batch reactor (SBR) fed with carbon sources of different biodegradability was investigated. During the biologic degradation process, the low molecular weight (MW) fraction (< 1 kDa) gradually decreased, while the refractory compounds with higher aromaticity were aggregated. Size exclusion chromatography (SEC) and fluorescence of excitation emission matrices (EEM) demonstrated that more biopolymers (polysaccharides or proteins) and humic-like substances were presented in the extracellular polymeric substance (EPS) extracted from the SBR fed with sodium acetate or glucose, while the EPS from SBR fed with slowly biodegradable dissolved organic carbon (DOC) substratestarch had relatively less biopolymers. Comparing the EfOM in sewage effluent of three SBRs, the effluent from SBR fed with starch is more aromatic. Organic carbon with MW>1 kDa as well as the hydrophobic fraction in DOM gradually increased with the carbon sources changing from sodium acetate to glucose and starch. The DOC fractionation and the EEM all demonstrated that EfOM from the effluent of the SBR fed with starch contained more fulvic acid-like substances comparing with the SBR fed with sodium acetate and glucose.  相似文献   
728.
分析了饮食业后堂噪声的频率特性,采取隔声、吸声、消声控制技术和防油雾措施,并独创设计了一种排油烟通风复合消声器,解决了同时排油烟和降噪的难题,得出了饮食业后堂噪声综合控制的有效工艺。经2年的实际应用证明,降噪能力强,可满足60dB(A)的区域环境标准的要求,效果稳定,是一项值得推广的技术。特别是排油烟通风复合消声器、通风消声窗及“声闸”的设计参数,可在同类噪声控制中推广应用。  相似文献   
729.
以银洞坡金矿为例,对选矿厂含氰废水进行了水质调查,采用碱性氯化法处理银洞坡金矿尾矿库的含氰废水,在去除氰化物和重金属方面都取得了较好的效果,提出了采用间歇式方法处理含氰废水工艺方案.  相似文献   
730.
Xie B  Zhang H  Cai P  Qiu R  Xiong Y 《Chemosphere》2006,63(6):956-963
BiVO4 powder with monoclinic structure was prepared and used as a visible-light catalyst simultaneously for the photooxidation of phenol and the photoreduction of Cr(VI). The photocatalytic efficiency was found to be rather low for either single phenol solution or single Cr(VI) solution. However, the photocatalytic reduction of Cr(VI) and photocatalytic oxidation of phenol proceed more rapidly for the coexistence system of phenol and Cr(VI) than for the single process, showing synergetic effect between the oxidation and reduction reactions. For the simultaneous photocatalytic reduction-oxidation process, the first-order kinetic constant of phenol degradation was 0.0314 min-1, being about six times higher than that for the photocatalytic process of single phenol. This result reveals the feasibility of using Cr(VI) as the electron scavenger of mBiVO4-mediated photocatalytic process of phenol degradation, and gives us an enlightenment to employ other semiconductor with a better visible light response but with a more positive band edge to efficiently degrade organic pollutants. This is the first report for simultaneous photocatalytic reduction of Cr(VI) and removal of phenol under visible light irradiation using photocatalyst mBiVO4.  相似文献   
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