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21.
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水循环过程中因受自然因素和人类的生活生产活动的影响,杂质和异物带入水循环形成污水。污水主要包括城市生活污水、工业废水和径流污水。若这些污水若不经处理就排入地面水体,就会使河流、湖泊受到严重污染。污水经过二级处理后,仍可能有病原菌,因此必须对污水进行消毒。本文分析比较了紫外线消毒以及氯消毒技术的适用条件、优缺点,还比较分析比较了二氧化氯消毒以及臭氧消毒技术的适用条件与优缺点,并对污水消毒技术的发展方向进行了探讨。 相似文献
23.
Sedimentary record of polycyclic aromatic hydrocarbons in Lake Erhai,
Southwest China 总被引:1,自引:0,他引:1
Jianyang Guo Zhang Liang Haiqing Liao Zhi Tang Xiaoli Zhao Fengchang Wu 《环境科学学报(英文版)》2011,23(8):1308-1315
The temporal distribution of polycyclic aromatic hydrocarbons (PAHs) was investigated in a sediment core from Lake Erhal in Southwest China using gas-chromatography/mass spectrometry (GC/MS) method.The total organic carbon (TOC) normalized total PAHs concentrations (sum of US Environmental Protection Agency proposed 16 priority PAHs) ranged from 31.9 to 269 μg/g dry weight (dw),and were characterized by a slowly increasing stage in the deeper sediments and a sharp increasing stage in the upper sediments.The PAHs in the sediments were dominated by low molecular weight (LMW) PAHs,suggesting that the primary source of PAHs was low- and moderate temperature combustion processes.However,both the significant increase in high molecular weight (HMW) PAHs in the upper sediments and the vertical profile of diagnostic ratios pointed out a change in the sources of PAHs from low-temperature combustion to high-temperature combustion.The ecotoxicological assessment based on consensus-based sediment quality guidelines implied that potential adverse biological impacts were possible for benzo(ghi)perylenelene and most LMW PAHs.In addition,the total BaP equivalent quotient of seven carcinogenic polycyclic aromatic hydrocarbons (BaA,CHr,BbF,BkF,BaP,DBA and INP) was 106.1 ng/g,according to the toxic equivalency factors.Although there was no great biological impact associated with the HMW PAlls,great attention should be paid to these PAH components based on their rapid increase in the upper sediments. 相似文献
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25.
Modeling VOC-odor exposure risk in livestock buildings 总被引:1,自引:0,他引:1
This paper describes a novel idea of linking models of exposure, internal dosimetry, and health effects. Risk assessment approach that integrates predicted odor caused by volatile organic compounds (VOC-odor) of toluene/xylene concentrations in human tissues leads to predict exposure risks in livestock buildings. First, VOC transport model was developed to calculate airborne toluene/xylene concentrations. Based on a physiologically based pharmacokinetic (PBPK) model, concentrations within five compartments representing lung, liver, fat, slowly perfused tissues, and rapidly perfused tissues could be quantified. By using a pharmacodynamic (PD) Hill model, we can optimally fit data from rat and human experiments to reconstruct dose-response relationships for accounting human health effects from nose poke and eye irritation. Results demonstrated that peak tissue concentration occurring at 5-10h in that fat contains the highest concentration than other tissues at around 4ppm of toluene and 1.8ppm of xylene. The EC(10) values are 114 and 232ppm, whereas expected risks are estimated to be 0.71% and 0.26% of human exposure to toluene and xylene, respectively. Risk analyses indicate that inhalation exposure in livestock buildings poses no significant threat to human health under the present environmental conditions. This method provides a rigorous and effective approach to relate target tissue concentration to human nose poke or eye irritation. We suggest that our probabilistic framework and methods be taken seriously because they produce general conclusions that are more robust and could offer a risk-management framework for discussion of future establishment of limits for respiratory exposure to VOC-odor. 相似文献
26.
Short-term effects of gaseous pollutants on cause-specific mortality in Wuhan, China 总被引:3,自引:0,他引:3
Qian Z He Q Lin HM Kong L Liao D Yang N Bentley CM Xu S 《Journal of the Air & Waste Management Association (1995)》2007,57(7):785-793
In Asia, limited studies have been published on the association between daily mortality and gaseous pollutants of nitrogen dioxide (NO2), ozone (O3), and sulfur dioxide (SO2). Our previous studies in Wuhan, China, demonstrated long-term air pollution effects. However, no study has been conducted to determine mortality effects of air pollution in this region. This study was to determine the acute mortality effects of the gaseous pollutants in Wuhan, a city with 7.5 million permanent residents during the period from 2000 to 2004. There are approximately 4.5 million residents in Wuhan who live in the city's core area of 201 km2, where air pollution levels are highest, and pollution ranges are wider than the majority of the cities in the published literature. We used the generalized additive model to analyze pollution, mortality, and covariate data. We found consistent NO2 effects on mortality with the strongest effects on the same day. Every 10-microg/m3 increase in NO2 daily concentration on the same day was associated with an increase in nonaccidental (1.43%; 95% confidence interval [CI]: 0.87-1.99%), cardiovascular (1.65%; 95% CI: 0.87-2.45%), stroke (1.49%; 95% CI: 0.56-2.43%), cardiac (1.77%; 95% CI: 0.44-3.12%), respiratory (2.23%; 95% CI: 0.52-3.96%), and cardiopulmonary mortality (1.60%; 95% CI: 0.85-2.35%). These effects were stronger among the elderly than among the young. Formal examination of exposure-response curves suggests no-threshold linear relationships between daily mortality and NO2, where the NO2 concentrations ranged from 19.2 to 127.4 microg/m3. SO2 and O3 were not associated with daily mortality. The exposure-response relationships demonstrated heterogeneity, with some curves showing nonlinear relationships for SO2 and O3. We conclude that there is consistent evidence of acute effects of NO2 on mortality and suggest that a no-threshold linear relationship exists between NO2 and mortality. 相似文献
27.
A full-scale sequencing batch reactor (SBR) system was evaluated for its ability to remove carbon and nitrogen from swine wastewater. The SBR was operated on four, six-hour cycles each day, with each cycle consisting of 4.5 hours of "React," 0.75 hours of "Settling", 0.75 hours for "Draw" and "Fill." Within each cycle, an amount of wastewater equivalent to about 5% of the reactor volume (5,500 litres) was removed and added. The SBR system was able to remove 82% of biochemical oxygen demand (BOD) and more than 75% of nitrogen. Even though the SBR effluent, with an average effluent BOD5 of about 588 mg L(-1), did not meet the discharge criteria, it enabled a reduction of the land base required for land application of swine wastewater by about 75%. Results indicated that the SBR system was a viable method for the treatment of swine wastewater. 相似文献
28.
Survey of heavy metal pollution and assessment of agricultural soil in Yangzhong district, Jiangsu Province, China 总被引:37,自引:0,他引:37
We investigated concentrations of Hg, Cd, Pb, Zn, Cu, As, Ni, and Cr in samples of soil, cereal, and vegetables from Yangzhong district, China. Compared to subsoils, the sampled topsoils are enriched in Hg, Cd, Cu, Pb, Zn, and As. High levels of Cd and Hg are observed in most agricultural soils. Concentrations of Cr and Ni show little spatial variation, and high Cu, Pb, and Zn contents correspond well to areas of urban development. High As contents are primarily recorded at the two ends of the sampled alluvion. The contents of Cd, Hg, and total organic carbon (TOC) increase gradually to maximum values in the upper parts of soil profiles, while Cr and Ni occur in low concentrations within sampled profiles. As, Pb, Cu, and Zn show patterns of slight enrichment within the surface layer. Compared to data obtained in 1990, Cd and Hg show increased concentrations in 2005; this is attributed to the long-term use of agrochemicals. Cr and Ni contents remained steady over this interval because they are derived from the weathering of parent material and subsequent pedogenesis. The measured As, Cu, Pb, and Zn contents show slight increases over time due to atmospheric deposition of material sourced from urban anthropogenic activity. Low concentrations of heavy metals are recorded in vegetables and cereals because the subalkaline environment of the soil limits their mobility. Although the heavy metal concentrations measured in this study do not pose a serious health risk, they do affect the quality of agricultural products. 相似文献
29.
Yi-Tang Chang Jiunn-Fwu Lee Keng-Hua Liu Yi-Fen Liao Vivian Yang 《Environmental science and pollution research international》2016,23(5):4024-4035
Nonionic surfactant-modified clay is a useful absorbent material that effectively removes hydrophobic organic compounds from soil/groundwater. We developed a novel material by applying an immobilized fungal laccase onto nonionic surfactant-modified clay. Low-water-solubility polycyclic aromatic hydrocarbons (PAHs) (naphthalene/phenanthrene) were degraded in the presence of this bioactive material. PAH degradation by free laccase was higher than degradation by immobilized laccase when the surfactant concentration was allowed to form micelles. PAH degradation by immobilized laccase on TX-100-modified clay was higher than on Brij35-modified clay. Strong laccase degradation of PAH can be maintained by adding surfactant monomers or micelles. The physical adsorption of nonionic surfactants onto clay plays an important role in PAH degradation by laccase, which can be explained by the structure and molecular interactions of the surfactant with the clay and enzyme. A system where laccase is immobilized onto TX-100-monomer-modified clay is a good candidate bioactive material for in situ PAHs bioremediation. 相似文献
30.
光照条件对跑道池光生物反应器内蛋白核小球藻生长特性的影响 总被引:1,自引:0,他引:1
本文采用多孔曝气管的曝气方式,以蠕动泵为藻液循环的动力,研究了气体流量、光照强度、光照周期等因素对跑道池光生物反应器内蛋白核小球藻生长与代谢特性的影响,并利用傅里叶红外光谱半定量法对不同光照条件下藻细胞内蛋白质、油脂以及多糖含量变化进行了分析。研究结果表明,适当的气体流量、光照强度和光照周期有利于跑道池内蛋白核小球藻细胞的生长和代谢。在本实验条件下,在最佳气体流量2 000 m L/min条件下,光照强度为3 500μW/cm2,光照周期为16∶8时最有利于蛋白核小球藻的生长;光照强度为2 000μW/cm2和光照周期为16∶8的条件均有利于藻细胞内油脂的积累。 相似文献