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661.
主要研究柠檬酸和EDTA淋洗剂对六价铬污染土壤的淋洗修复效果,重点考察淋洗剂浓度、液固比、淋洗时间和淋洗方式对土壤六价铬去除效果的影响。研究结果表明:随着淋洗剂浓度的增加,柠檬酸淋洗剂对供试土壤六价铬的去除率逐渐升高,最高为54.0%,而EDTA淋洗剂对供试土壤的去除率先升高后降低,浓度在0.4 mol·L-1时达到最高,为66.3%;土壤六价铬去除率随液固比的增加呈现先升高后降低的趋势,当液固比为7:1时,0.5 mol·L-1柠檬酸和0.1 mol·L-1 EDTA淋洗剂对供试土壤六价铬的去除率最高,分别为69.6%和61.9%;增加淋洗时间,供试土壤六价铬的去除率逐渐升高,2 h后增幅不大;就清洗方式而言,EDTA淋洗剂一次加入对土壤六价铬的去除效果最好,而柠檬酸淋洗剂宜采用二次加入一次分离的方式。 相似文献
662.
随着大庆市畜禽养殖业的发展,畜禽养殖过程中产生的粪便、尿液及其他物质处理不及时,会对环境造成污染、人体产生危害,特别是近年来社会环境意识不断加强,长期积累的畜禽养殖污染问题越发凸显出来.2015年,大庆市畜禽养殖业化学需氧量、氨氮的排放量分别为11.62万吨、0.2万吨,占全市总排放量的84.94%、37.99%,占农业源排放量的99.9%、89.79%,畜禽养殖业已成为农业面源污染的主要根源.根据大庆市畜禽养殖的污染及减排现状,分析了畜禽养殖污染存在的问题及成因,提出了科学的污染防治对策,为保护大庆市生态环境、促进畜禽养殖业发展提供参考. 相似文献
663.
Preliminary investigation of phosphorus adsorption onto two types of iron oxide-organic matter complexes 总被引:1,自引:0,他引:1
Iron oxide(FeO)coated by natural organic matter(NOM)is ubiquitous.The associations of minerals with organic matter(OM)significantly changes their surface properties and reactivity,and thus affect the environmental fate of pollutants,including nutrients(e.g.,phosphorus(P)).In this study,ferrihydrite/goethite-humic acid(FH/GE–HA)complexes were prepared and their adsorption characteristics on P at various p H and ionic strength were investigated.The results indicated that the Fe O–OM complexes showed a decreased P adsorption capacity in comparison with bare Fe O.The maximum adsorption capacity(Q_(max))decreased in the order of FH(22.17 mg/g)FH-HA(5.43 mg/g)GE(4.67 mg/g)GE-HA(3.27 mg/g).After coating with HA,the amorphous FH–HA complex still showed higher P adsorption than the crystalline GE–HA complex.The decreased P adsorption observed might be attributed to changes of the Fe O surface charges caused by OM association.The dependence of P adsorption on the specific surface area of adsorbents suggests that the Fe O component in the complexes is still the main contributor for the adsorption surfaces.The P adsorptions on Fe O–HA complexes decreased with increasing initial p H or decreasing initial ionic strength.A strong dependence of P adsorption on ionic strength and p H may demonstrate that outer-sphere complexes between the OM component on the surface and P possibly coexist with inner-sphere surface complexes between the Fe O component and P.Therefore,previous over-emphasis on the contributions of original minerals to P immobilization possibly over-estimates the P loading capacity of soils,especially in humic-rich areas. 相似文献
664.
665.
Sorption of tylosin and sulfamethazine on solid humic acid 总被引:3,自引:0,他引:3
Tylosin(TYL) and sulfamethazine(SMT) are ionizable and polar antimicrobial compounds,which have seeped into the environment in substantial amounts via fertilizing land with manure or sewage. Sorption of TYL and SMT onto humic acid(HA) may affect their environmental fate. In this study, the sorption of TYL and SMT on HA at different conditions(pH, ionic strength) was investigated. All sorption isotherms fitted well to the Henry and Freundlich models and they were highly nonlinear with values of n between 0.5 and 0.8, which suggested that the HA had high heterogeneity. The sorption of TYL and SMT on HA decreased with increasing p H(2.0–7.5), implying that the primary sorption mechanism could be due to cation exchange interactions between TYL~+/SMT~+ species and the functional groups of HA.Increasing ionic strength resulted in a considerable reduction in the K_d values of TYL and SMT,hinting that interactions between H bonds and π–π EDA might be an important factor in the sorption of TYL and SMT on HA. Results of Fourier transform infrared(FT-IR) and ~13C-nuclear magnetic resonance(NMR) analysis further demonstrated that carboxyl groups and O-alkyl structures in the HA could interact with TYL and SMT via ionic interactions and H bonds,respectively. Overall, this work gives new insights into the mechanisms of sorption of TYL and SMT on HA and hence aids us in assessing the environmental risk of TYL and SMT under diverse conditions. 相似文献
666.
Changzhou Xu Rongjun Qu Shasha Li Changmei Sun Ying Zhang Jingjing Gao Yuzhong Niu Qianli Ma Xiquan Song Shuangcheng Wang Chunxia Li 《Journal of Polymers and the Environment》2016,24(3):206-220
A series of nanaoscale aramid-based adsorbents were prepared by the functionalization of poly (p-phenylene terephthalamide) (PPTA) with different content of ethylenediamine (EDA). Their structures were characterized by field emission scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis, and elemental analysis. Metal ions, including Hg2+, Pb2+, Ag+, Cu2+, Cd2+, and Ni2+ were chosen as the models to explore the binding behaviors of PPTA–ECH–EDA in aqueous medium. Results showed that PPTA–ECH–EDA exhibited higher adsorption capacity for Hg2+ due to their nanoscale structures. In particular, the adsorption rate was so high that equilibrium was achieved within 15 min for Hg2+. The adsorption of Hg2+ on PPTA–ECH–EDA followed the pseudo second-order model well. Langmuir and Freundlich models were employed to fit the isothermal adsorption, and the results revealed that Freundlich isotherm was a better model to predict the experimental data. The adsorption mechanism was revealed by X-ray photoelectron spectroscopy. It is preconceived that PPTA–ECH–EDA could be used as an effective adsorbent for fast removal of heavy ions from wastewater. 相似文献
667.
668.
669.
Sang-Keun Song Zang-Ho Shon Ki-Hyun Kim 《Atmospheric environment (Oxford, England : 1994)》2009,43(18):3015-3023
The photochemical oxidation and dispersion of reduced sulfur compounds (RSCs: H2S, CH3SH, DMS, CS2, and DMDS) emitted from anthropogenic (A) and natural (N) sources were evaluated based on a numerical modeling approach. The anthropogenic emission concentrations of RSCs were measured from several sampling sites at the Donghae landfill (D-LF) (i.e., source type A) in South Korea during a series of field campaigns (May through December 2004). The emissions of natural RSCs in a coastal study area near the D-LF (i.e., source type N) were estimated from sea surface DMS concentrations and transfer velocity during the same study period. These emission data were then used as input to the CALPUFF dispersion model, revised with 34 chemical reactions for RSCs. A significant fraction of sulfur dioxide (SO2) was produced photochemically during the summer (about 34% of total SO2 concentrations) followed by fall (21%), spring (15%), and winter (5%). Photochemical production of SO2 was dominated by H2S (about 55% of total contributions) and DMS (24%). The largest impact of RSCs from source type A on SO2 concentrations occurred around the D-LF during summer. The total SO2 concentrations produced from source type N around the D-LF during the summer (a mean SO2 concentration of 7.4 ppbv) were significantly higher than those (≤0.3 ppbv) during the other seasons. This may be because of the high RSC and SO2 emissions and their photochemistry along with the wind convergence. 相似文献
670.
国内近年来在建筑施工中经常发生土方坍塌事故,给人民生命财产造成了巨大损失。为此我们必须认真分析事故原因,总结经验教训,采取有效改进措施,才能防止类似事故重复发生。 相似文献