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991.
电化学方法生成羟基自由基及其在酸性铬蓝降解脱色中的应用1) 总被引:26,自引:3,他引:23
在电解槽中,以Na2SO4为支持电解质,多孔石墨电极为阴极,金属铁为阳极,在10mA·cm-2的阴极电流密度下,电解生成的过氧化氢与阳极溶解的Fe2+进行反应,生成羟基自由基(Fenton试剂),进而对有机染料进行氧化反应,使其不饱和双键断裂,从而达到有机染料降解、脱色的目的,在生成Fentonn试剂的反应中,Fe2+被氧化为 Fe3+,生成的 Fe3+在阴极得电子后重新被还原为Fe2+,因此,在电解槽中 Fe2+起着催化剂的作用.COD的去除率大于80%,脱色率达100%.脱色速率的测定表明其为一级反应,反应速度常数k等于l.98 × 10-4s-1. 相似文献
992.
993.
994.
Some potential hazardous trace elements contamination and their ecological risk in sediments of western Chaohu Lake, China 总被引:3,自引:0,他引:3
Liu-Gen Zheng Gui-Jian Liu Yu Kang Ren-Kang Yang 《Environmental monitoring and assessment》2010,166(1-4):379-386
The Chaohu is one of the largest five freshwater lakes in China. It provides freshwater for agriculture, life, and part of industry. The quality of water becomes worst and worst due to the toxic matter. In this study, we collected the samples from the sedimentary mud in the lake. The distribution of some potential hazardous trace elements (Cu, Ni, Cr, As, Pb, Cd, and Hg) in the sediments of western Chaohu Lake, has been determined and studied, and the enrichment factors, the index of geoaccumulation, and potential ecological risk were analyzed and calculated. The results show that: the levels of selected potential hazardous trace element vary from different sampling sites and significant anthropogenic impact of Pb and Cd occur in sediments. The contamination rank of Pb and Cd are moderate, and Pb has a light potential ecological risk, but Cd is heavy. The total potential ecological risk of the selected hazardous trace elements in this study in Chaohu Lake is moderate. Cluster and correlation analysis indicate that the selected potential hazardous trace element pollutant has different source and co-contamination also occur in sediments. 相似文献
995.
Urban wetland parks are a new type of urban park that have developed rapidly in recent years and have caught the attention
of multiple governmental departments. The objective of this paper was to describe the trophic states of creeks and their relationship
to water levels in an urban wetland park in Xixi, China. The study was based on temporal and spatial data collected monthly
between March 2009 and March 2010. The results indicated that: (1) water quality significantly changed from upstream to downstream
in study creeks. From upstream to downstream, water quality of creeks I and III improved; however, the water quality of creek
IV and V declined; (2) trophic states in Xixi creeks differed according to seasons. Overall, the nutrition in creeks was measured
at the slight eutrophication level. Nutrition was highest in summer and lowest in winter; (3) the relationship between water
quality and water level differed dramatically between creeks. Water quality and water level in creek I was significantly negatively
correlated, while no obvious trends were observed in other creeks. In order to improve water quality in creeks, the valid
technique is to strengthen the management of inflowing water quality and then control water levels. 相似文献
996.
以2005年以后太湖无锡区域底质为研究对象,分析了太湖底泥中重金属的含量分布及富集状况,采用地积累指数法和潜在生态危害指数法对重金属的生态危害进行评价。结果表明:太湖无锡区域底质受重金属轻度污染,含量高于全国水系沉积物平均值;地积累指数法显示太湖无锡区域底质中重金属污染排序为Cu=As〉Pb〉Zn〉Cr〉Cd〉Hg;金属对太湖无锡区域底质构成的潜在生态危害由强到弱为Hg〉Cu〉As〉Cd〉Pb〉Cr〉Zn;从区域上看,2种评价方法均表明底质中重金属危害程度为宜兴沿岸区〉梅梁湖〉五里湖〉贡湖无锡水域。 相似文献
997.
Polycyclic aromatic hydrocarbons in urban soils of Hangzhou: status,distribution, sources,and potential risk 总被引:1,自引:0,他引:1
Guoguang Yu Zhiheng Zhang Guiling Yang Weiran Zheng Lihong Xu Zheng Cai 《Environmental monitoring and assessment》2014,186(5):2775-2784
Concentration, composition profile, spatial distribution, sources, and health risk of 16 polycyclic aromatic hydrocarbons (PAHs) were analyzed in 69 surface soil samples collected from Hangzhou urban districts. ∑PAHs ranged from 180.77 to 1,981.45 μg kg?1 with a mean of 611.28 μg kg?1. Among different functional areas, a higher level of PAHs was found in the roadsides, followed by commercial districts, residential areas, parks, and greenbelts. The composition of PAHs was characterized by high molecular weight PAHs (4?~?6 rings). Principal component analysis (PCA) and PAH isomeric ratios indicated that PAHs mainly originated from combustion, especially vehicle exhaust. The incremental lifetime cancer risks (ILCRs) associated with exposures to PAHs in soil were calculated separately for children and adults under normal and extreme conditions. The results showed that ILCRs for urban soil of Hangzhou were acceptable. However, attentions should be attracted on the sites of high PAH concentrations because the ILCRs were closed to 10?4 under extreme conditions, especially for children. 相似文献
998.
999.
Li Z Mulholland JA Romanoff LC Pittman EN Trinidad DA Lewin MD Sjödin A 《Journal of environmental monitoring : JEM》2010,12(5):1110-1118
Non-occupational inhalation and ingestion exposure to polycyclic aromatic hydrocarbons (PAHs) has been studied in 8 non-smoking volunteers through personal air sampling and urinary biomonitoring. The study period was divided into 4 segments (2 days/segment), including weekdays with regular commute and weekends with limited traffic related exposures; each segment had a high or low PAH diet. Personal air samples were collected continuously from the subjects while at home, at work, and while commuting to and from work. All urine excretions were collected as individual samples during the study. In personal air samples, 28 PAHs were measured, and in urine samples 9 mono-hydroxylated metabolites (OH-PAHs) from 4 parent PAHs (naphthalene, fluorene, phenanthrene and pyrene) were measured. Naphthalene was found at higher concentrations in air samples collected at the subjects' residences, whereas PAHs with four or more aromatic rings were found at higher levels in samples taken while commuting. Urinary OH-PAH biomarker levels increased following reported high inhalation and/or dietary exposure. On days with a low PAH diet, the total amount of inhaled naphthalene during each 24-hour period was well correlated with the amount of excreted naphthols, as was, to a lesser extent, fluorene with its urinary metabolites. During days with a high dietary intake, only naphthalene was significantly correlated with its excreted metabolite. These findings suggest that this group of non-occupational subjects were exposed to naphthalene primarily through indoor air inhalation, and exposed to other PAHs such as pyrene mainly through ingestion. 相似文献
1000.
基于Landsat-8数据和劈窗算法的地表温度反演及城市热岛效应研究 总被引:2,自引:0,他引:2
陆地表面温度(Land Surface Temperature,LST)是地表能量平衡组分中的一个重要参数。随着卫星遥感技术的快速发展,遥感反演成为获取区域LST的一个重要手段。目前已有学者提出多种基于遥感数据反演LST的算法,其中劈窗算法被证明是一种精度较高的算法。基于Landsat-8卫星30 m空间分辨率的陆地成像仪(OLI)数据和100 m分辨率的热红外传感器(TIRS)数据,采用劈窗算法计算了无锡地区的LST,并采用地面实测水温数据和同步的MODIS温度产品对Landsat-8的计算结果进行了验证和对比分析。结果表明:基于Landsat-8数据和劈窗算法获取的LST精度较高,误差1K。在计算的LST结果基础上,进一步提取了热场变异指数来分析城市热岛空间分布特征,给出了城市热岛效应的定量化描述,并就不同地表覆盖类型对热岛效应的影响进行了分析。 相似文献