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71.
72.
Tollestrup K Frost FJ Cristiani M McMillan GP Calderon RL Padilla RS 《Environmental geochemistry and health》2005,27(1):47-53
Populations living in the Southwest United States are more likely to be exposed to elevated drinking water arsenic levels compared to other areas of the country. Skin changes, including hyperpigmentation and generalized hyperkeratosis, are the most common signs of chronic arsenic ingestion from drinking water. The purpose of this study was to determine the feasibility of using dermatology practices in New Mexico, Arizona, and western Texas as a surveillance system for arsenical skin disorders related to drinking water. Postcard questionnaires were mailed to practicing dermatologists. The number of cases of arsenical hyperpigmentation/keratoses seen by these dermatologists during the past 10 years and the past year were estimated. Of 240 dermatologists who were mailed questionnaires, 37 reported seeing 237 patients with arsenical hyperpigmentation/keratoses in the past 10 years and 35 patients in the past year. Since approximately one-eighth of dermatologists practicing in the Southwest saw at least one patient with arsenical hyperpigmentation/keratoses during one year, it appears feasible to complete a population-based study of these conditions. 相似文献
73.
Zoran S. Petrović Wei Zhang Alisa Zlatanić Charlene C. Lava Michal Ilavskyý 《Journal of Polymers and the Environment》2002,10(1-2):5-12
Polyurethane networks from soybean oil have a number of valuable properties, which are determined by their chemical composition and cross-linking density. Changing the molar ratio of reacting groups can vary the latter. In this work we have varied the NCO/OH molar ratio (isocyanate index) from 1.05 to 0.40 in a soy polyol/MDI system, and tested physical and mechanical properties. The degree of swelling in toluene increased from 52–206% by decreasing isocyanate index from 1.05–0.4. The sol fractions and network densities determined from swelling in toluene were compared with ones obtained using the network formation theory based on branching processes. The comparison of experimental sol fractions and network densities with those predicted by theory of network formation suggest that 5–10% of bonds are lost in cycles and that high entanglement contributions increase the network densities. Polymers prepared with NCO/OH ratios from 1.05–0.8 were glassy while the others were rubbery, and that was reflected in their properties. Glass transition temperature (DSC) of the networks decreased from 64–7°C, tensile strength from 47–0.3 MPa, and elongation at break increased from 7–232%. The activation energy of the glass transition, determined from dielectric spectra, varied from 222–156 kJ/mol as the molar ratio of NCO to OH groups decreased from 1.05–0.4. 相似文献
74.
Michael Sheehan 《Journal of the American Water Resources Association》1981,17(2):275-279
ABSTRACT: This article discusses the implications of accepting various standards of scientific evidence in disputes arising over the dumping of potentially hazardous materials into public waterways and drinking water supplies. Standards based on the types of risks and levels of benefits suffered and received by adjacent populations are evaluated within the context of the several pieces of federal legislation which relate to water quality. A case study of Reserve Mining Corporation's dumping of taconite wastes into Lake Superior is presented to illustrate the ramifications of decisions based on differing perspectives of the problem and its impacts by the courts, the affected public, RMC, and the regulatory agencies involved. 相似文献
75.
聚氨酯的回收利用技术 总被引:7,自引:0,他引:7
随着聚氨酯工业的迅速发展,大量的聚氨酯废弃物需要回收利用,文章介绍发展和应用现状。 相似文献
76.
C. Tashiro R.E. Clement S. Davies T. Dann P. Steer M. Bumbaco B. Oliver T. Munshaw J. Fenwick B. Chittim M.G. Foster 《Chemosphere》1990,20(10-12)
A laboratory intercomparison study was carried out to determine the current capability of Canadian laboratories for the analysis of dioxins and furans in ambient air. Seven laboratories (government and private) participated in the analysis of exposed foam/filter samples, ambient air extracts and standard mixtures. The results indicated that a number of laboratories were capable of the aforementioned analyses; however, further analytical methodology development is also required. 相似文献
77.
2,4,6-三氯酚在环境中广泛分布,是典型的持久性有机污染物.脱卤呼吸菌能还原分解氯酚,使其毒性大大降低,继而被其他微生物氧化分解并矿化.然而脱卤呼吸菌在自然环境中丰度较低,代谢速率慢,对电子利用能力较差,因此传统的生物添加或生物激活等原位修复方法往往导致效能受限,可应用性差.本研究驯化富集了具有稳定厌氧还原脱氯2,4,6-三氯酚能力的混合菌群,在添加乙酸钠(5 mmol·L-1)和氢气(10 mL)的情况下,在6 d内将2,4,6-三氯酚还原脱卤为4-氯酚.研究采用聚氨酯泡沫作为生物载体材料,在聚氨酯泡沫表面负载电气石,发现在无氢气额外添加的情况下,2,4,6-三氯酚的还原脱氯速率提高了6倍,且脱卤性能稳定.对强化后混菌的群落结构及潜在核心脱氯功能菌属进行分析,16S rRNA测序鉴定结果表明假单胞菌属(Pseudomonas sp.)在混合菌群中的占比超过90%,为体系中的核心脱氯功能菌.本研究为地下水中还原脱卤菌群的应用提供了理论技术. 相似文献
78.
Ningombam Linthoingambi Devi Shihua Qi Paromita Chakraborty Gan Zhang Ishwar Chandra Yadav 《环境科学学报(英文版)》2011,23(5):808-815
Thirty-six polyurethane foam disk passive air samplers (PUF-PAS) were deployed over a year during January to December, 2009
at three locations, i.e., Imphal (urban site), Thoubal (rural site) and Waithou (alpine site) of Manipur, to assess the seasonal local
atmospheric emission of selected organochlorine pesticides (OCPs). The average concentration of HCHs monitored at mountain site
during hot season (Mar, Apr, and May) and rainy seasons (Jun, Jul, Aug, and Sep) were 403 and 349 pg/m3, respectively. DDTs had a
high concentration with 384 pg/m3 at rural site and 379 pg/m3 at urban site during hot seasons. Endosulfans and chlordane were found
high in concentration during hot seasons (260 pg/m3) and low during retreating monsoon seasons (44 pg/m3) at rural site. Most of the
OCPs concentrations were high during cultivation period. The OCP concentrations of rainy season were highly correlated (p < 0.01)
with OCPs of hot seasons. Further, positive correlation (p < 0.05) was also obtained between cold seasons and retreating monsoon.
Principal component analysis showed a significant correlation among the four seasons and distribution pattern of OCPs in air. Back
trajectory analysis by using HYPSLIT model showed a long range air transport of OCPs to the present study area. Present OCP levels
at Manipur is an outcome of both local emission and also movement of air mass by long range atmospheric transport. 相似文献
79.
Nitrification performance of nitrifying bacteria immobilized in waterborne
polyurethane at low ammonia nitrogen concentrations 总被引:1,自引:1,他引:0
Suspended and waterborne polyurethane immobilized nitrifying bacteria have been adopted for evaluating the e ects of environmental
changes, such as temperature, dissolved oxygen (DO) concentration and pH, on nitrification characteristics under conditions
of low ammonia concentrations. The results showed that nitrification was prone to complete with increasing pH, DO and temperature.
Sensitivity analysis demonstrated the e ects of temperature and pH on nitrification feature of suspended bacteria were slightly greater
than those of immobilized nitrifying bacteria. Immobilized cells could achieve complete nitrification at low ammonia concentrations
when DO was su cient. Continuous experiments were carried out to discuss the removal of ammonia nitrogen from synthetic micropollute
source water with the ammonia concentration of about 1 mg/L using immobilized nitrifying bacteria pellets in an up-flow inner
circulation reactor under di erent hydraulic retention times (HRT). The continuous removal rate remains above 80% even under HRT
30 min. The results verified that the waterborne polyurethane immobilized nitrifying bacteria pellets had great potential applications
for micro-pollution source water treatment. 相似文献
80.
文章以甲苯二异氰酸酯(TDI)、聚氧化丙烯二醇(PPG)为基本原料,二羟甲基丙酸(DMPA)为亲水化改性单体、三羟甲基丙烷(TMP)为扩链剂通过预聚体法制备了淀粉改性水性聚氨酯环保型固沙剂,研究了淀粉用量对固沙剂乳液及其所成胶膜性能的影响。研究结果表明:在扩链聚合时加入可溶性淀粉,可以得到稳定的聚氨酯乳液;随着可溶性淀粉用量的增加,乳液的粘度增加,粒径呈增大趋势,胶膜拉伸强度减小;动态热力学分析显示胶膜储能模量E’随着淀粉含量的增加而减小,而玻璃化转变温度升高;保水实验显示保水效果随淀粉含量的增加而提高。当可溶性淀粉与纯聚氨酯的质量比为10%时,胶膜的拉伸强度和断裂伸长率分别为16.7 MPa和662%,而应用此配比固沙液的沙土在测试条件下10 h的失水率仅为55.7%,达到固沙剂保水性和胶膜力学性能之间较好的平衡。 相似文献