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461.
北京城市雨水、树冠水和地表径流中有机氯农药的污染特征 总被引:1,自引:0,他引:1
对北京降雨过程中雨水、树冠水、地表径流等介质中有机氯农药(OCPs)的污染特征进行了研究,研究的污染物包括六氯苯(HCB)、六六六(HCH)和滴滴涕(DDT)。结果显示,在雨水、树冠水和地表径流中,HCH含量最高(几何平均浓度分别为11.1、21.6和25.1 ng/L),其次是HCB(几何平均浓度分别为3.71、3.54和5.91 ng/L)和DDT(几何平均浓度分别为2.64、4.66和10.6 ng/L)。对地表径流样品中所测的OCPs组分浓度与径流水质参数和气象参数的相关分析显示,所测各OCPs组分浓度与pH呈显著负相关,与径流的溶解性有机碳含量呈显著正相关,降雨量和雨前晴天数对不同组分OCPs的影响并不完全相同。平均贡献率的计算表明,雨水是城市地表径流中OCPs的一个重要来源,树冠水的贡献也不可忽视。 相似文献
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In this study, aerobic granules were cultivated in sequencing batch reactors with activated sludge as the seed. The reactors were operated for 12 h per cycle with the organic loading rate (OLR) increasing in double stepwise from 0.5 to 4.0 g COD L−1 d−1. Within the 40 d running, black granules with regular and smooth morphology were cultivated, which had high wet density and high settling velocity. During the granulation process, foams emerged and disappeared in the reactor, coinciding with the proliferation of filamentous microorganisms in the granules, implying that surfactants might exist and play an important role in the granulation. Using ultra performance liquid chromatography-tandem mass spectrometry, the surfactants were identified as homologous compounds of polyethylene glycol (PEG) with molecular weights ranging mainly from 100 to 500 Da. Their general formulas were proposed as HO-[CH2-CH2-O]n-H. The source of PEG still needs further investigation. 相似文献
464.
Thermal removal of PCDD/Fs from medical waste incineration fly ash--effect of temperature and nitrogen flow rate 总被引:2,自引:0,他引:2
The fly ash used in this study was collected from a bag filter in a medical waste rotary kiln incineration system, using lime and activated carbon injection followed by their collection as mixed fly ash. Experiments were conducted on fly ash in a quartz tube, heated in a laboratory-scale horizontal tube furnace, in order to study the effect of temperature and nitrogen flow rate on the removal of PCDD/Fs. Results indicated that in this study PCDD/Fs in the fly ash mostly were removed and desorbed very little into the flue gas under thermal treatment especially when the heating temperature was higher than 350 °C, and dechlorination and destruction reactions took important part in the removal of PCDD/Fs. However, in terms of flow rate, when flow rate was higher than 4 cm s−1, destruction efficiency of PCDD/Fs decreased dramatically and the main contributors were P5CDF, H6CDF and H7CDF desorbed to flue gas, the PCDD/Fs in the fly ash decreased with enhanced flow rate. 相似文献
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Tong Chen Xiaodong Li Jianhua Yan Shengyong Lu Kefa Cen 《Atmospheric environment (Oxford, England : 1994)》2011,45(36):6567-6575
Levels of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) were determined in fourteen ambient air samples collected in twelve cities of five provinces and one large municipality in China. The PCDD/F concentrations varied from 2.6 to 120 pg m−3 (or from 0.04 to 1.93 pg I-TEQ m−3). Generally, TCDF was the dominant homologue group and as a rule the homologue concentration of PCDF decreased with rising chlorine substitution number of PCDF. In all cases 2,3,4,7,8-PeCDF was the most important contributor to the I-TEQ value, accounting for 35–57% of the total I-TEQ value. Higher PCDD/F levels in ambient air were found during winter. The highest PCDD/F levels were found in Chengdu, Sichuan Province. In general, the PCDD/F levels in this study were in the same range as in other studies in China. 相似文献
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Mi Yan Xiao Dong Li Sheng Yong Lu Tong Chen Yong Chi Jian Hua Yan 《Journal of Material Cycles and Waste Management》2011,13(3):213-218
The huge amount of medical waste (MW) has caused a tough challenge to environmental protection in China because of its serious
infectious potential. At present, incineration is the most common technology for MW disposal. Unfortunately, the medical waste
incinerator (MWI) is considered one of the major sources of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs). This study was conducted to investigate the generation and the components of MW; the
fingerprint of PCDD/Fs in MWI; and PCDD/F, polychlorinated biphenyl (PCB) and hexachlorobenzene concentrations in residue
ash. The estimated annual production of MW was estimated to be 0.97 million tons in China in 2008; in addition, plastic and
rubber accounted for 24.5% of MW contents. PCDD/F emissions from MWI could be divided into two main groups according their
fingerprints, and the ratio of PCDFs/PCDDs was mostly over 1.5, with a mean value of 3.43. The toxic equivalent of PCDD/Fs
was over 30 times that of the value of PCBs in the residue ash, and PCDD/F contents in fly ash accounted for approximately
67% of the total output of PCDD/Fs, which was in line with the UNEP default emission factors for MWI (class 3, 63.7%). 相似文献