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排序方式: 共有1453条查询结果,搜索用时 390 毫秒
491.
Fromme H Gruber L Schlummer M Wolz G Böhmer S Angerer J Mayer R Liebl B Bolte G 《Environment international》2007,33(8):1012-1020
Phthalates are ubiquitous environmental chemicals with potential detrimental health effects. The purpose of our study was to quantify dietary intake of phthalates and of DEHA (Di-ethylhexyl adipate) using duplicate diet samples and to compare these data with the calculated data based on urinary levels of primary and secondary phthalate metabolites. 27 female and 23 male healthy subjects aged 14-60 years collected daily duplicate diet samples over 7 consecutive days. Overall, 11 phthalates were measured in the duplicates by GC/MS and LC/MS methods. Urinary levels of primary and secondary phthalate metabolites are also available. The median (95th percentile) daily intake via food was 2.4 (4.0) microg/kg b.w. (Di-2-ethylhexyl phthalate, DEHP), 0.3 (1.4) microg/kg b.w. (Di-n-butyl phthalate, DnBP), 0.6 (2.1) microg/kg b.w. (Di-isobutyl phthalate, DiBP) and 0.7 (2.2) microg/kg b.w. for DEHA. MEPH (Mono-2-ethylhexyl phthalate) was detectable only in minor concentrations in the samples, thus conversion of DEHP to MEHP and dietary intake of MEHP were negligible. When comparing back-calculated intake data of the DEHP metabolites with dietary DEHP intake from the day before significant correlations were observed for most of the metabolites. No correlation was found for DnBP and only a weak but significant correlation for DiBP. The median and 95th percentile daily dietary intake of all target analytes did not exceed the recommended tolerable daily intake. Our data indicated that food was the predominant intake source of DEHP, whilst other sources considerably contributed to the daily intake of DnBP and DiBP in an adult population. 相似文献
492.
493.
A kinetic model for the Ti(IV)-catalyzed H2O2/O3 process was established, and the experimental results demonstrated that the model could well describe this ozone-based oxidative system mathematically and chemically. 相似文献
494.
495.
荆州市中心城区集中式饮用水源保护区优化研究 总被引:1,自引:1,他引:0
荆州市中心城区集中式饮用水源位于长江,为河流型水源地,在长江荆州城区段23 km范围内分布6个集中式饮用水源地,实际日取水量为设计规模的32.37%。为此提出将饮用水源保护区进行优化调整,将6个集中式饮用水源保护区减少为3个,保护区水域岸线长度从15.3 km缩减为9.9 km,一级保护区从8.3 km调整为3.3 km,并通过分析优化调整前后该江段水环境容量、减少饮用水源安全隐患和充分合理地发挥岸线资源功能等方面论证优化的合理性。 相似文献
496.
497.
MBR污水处理工艺中活性污泥动力学参数测定 总被引:5,自引:1,他引:4
缺乏可靠的污泥动力学设计参数是膜-生物反应器(membrane bioreactor,MBR)工艺在实际应用中遇到的主要问题之一.以某座处理城市污水的实际规模MBR工程的好氧活性污泥为对象,采用耗氧速率表征方法,测定计算得到以下动力学参数值:异养菌产率系数YH=0.693、自养菌产率系数YA=0.263、异养菌衰减系数KdH=0.108 d-1、自养菌衰减系数KdA=0.089 d-1、COD最大比去除速率vmS=1.94 mg·(mg·d)-1、COD去除半饱和常数KS=34.6 mg·L-1、氨氮最大比去除速率vmN=0.18 mg·(mg·d)-1、氨氮去除半饱和常数KN=1.06 mg·L-1.以上结果与传统活性污泥法工艺(CAS)中污泥的文献报道值相比,YH和KdH较高,而vmS和vmN较低.MBR的高污泥浓度条件可能是导致上述差异出现的主要原因. 相似文献
498.
好氧颗粒污泥能有效降解氯苯胺类化合物,然而,其同步高效降解的性能和基质间作用模式尚不清楚。文章考察好氧颗粒污泥体系降解和矿化氯苯胺类化合物的性能,并深入探讨同步降解过程中,各基质间的促进或抑制效应。实验结果表明,该体系降解单一氯苯胺类化合物遵循合Luong动力学模型,邻氯苯胺(2-CA)、间氯苯胺(3-CA)、对氯苯胺(4-CA)最大降解浓度(Sm)分别为:678.1 mg/L,837.7 mg//L和819.8 mg/L;好氧颗粒污泥体系能够完全降解和矿化总浓度低于750 mg/L的氯苯胺混合物,各化合物间降解速率符合3-CA>4-CA>2-CA。当氯苯胺类化合物共存时,相互间存在竞争性抑制作用,其中,2-CA对3-CA和4-CA的抑制作用明显小于后两者混合的相互抑制作用;对于2-CA的生物降解,3-CA的抑制作用小于4-CA。 相似文献
499.
Abstract The measurement of urban population carrying capacity is the basis for cities’ sustainable development. However, the traditional study on population carrying capacity which was based on food supply is not applicable to the single urban area. This paper built a model for the analysis of urban carrying capacity, and took Haidian District in Beijing as an example to calculate the urban carrying capacity of Haidian District in the future, which was the basis for the improvement of the population carrying capacity. This study would also provide a reference to the measurement of the urban population carrying capacity for other cities and districts in China. 相似文献
500.
《International Journal of Sustainable Engineering》2013,6(4):240-247
ABSTRACTThe biogas constituting majorly CH4 and CO2 has been produced by Ca(OH)2 pre-treated wheat straw with pre-digested cow dung. Some of the key thermodynamic parameters like specific heat capacity, density and heating capacity of the biogas produced have also been calculated per day as well as throughout the hydraulic retention time. The governing equations of biogas with appropriate phase and interfacial conditions describing the physics of the biogas have been derived. The control volume approach has been used to predict the total volume (ml) of biogas, CH4 and CO2 throughout the experiment and on the daily basis. The effects of feedstock, temperature and pressure on the production of biogas, CH4 and CO2 in anaerobic digestion have also been studied. The average number of molar fraction and conversion ratio of CH4 and CO2 are correlated with number of carbon atoms available in feedstock. Numerical calculations by using developed model and Modified Gompertz model have shown proficient agreement with the experimental observations. 相似文献