This study focused on the sorption isotherms of 1,1,1-trichloro-2,2-bis(p-chlorophenyl) ethane (p,p'-DDT) and 1,1-dichloro-2,2-bis(p-chlorophenyl) ethylene (p,p'-DDE) on different original clays (i.e., zeolite, montmorillonite and attapulgite) and organoclay complexes. Sorption of organic pollutants was determined using gas chromatographic (GC) techniques to investigate the sorption behavior, and characterize the effect of, different organic cations. The original clays only sorbed low amounts of p,p'-DDT and p,p'-DDE, and the sorptive curves can be classified as L-shaped. Organoclays exhibited higher amounts of p,p'-DDT and p,p'-DDE sorption. The p,p'-DDT and p,p'-DDE sorption increased with increasing total organic carbon (OC) content of the organoclays. For hexadecyltrimethylammonium (HDTMA)-modified organoclays, the dominant adsorptive medium showed the partitioning sorption of hydrophobic-hydrophobic interaction, indicating no competitive sorption. The sorptive curves can be classified as C-shaped of constant partition (CP). However, benzyltrimethylammonium (BTMA)-modified organoclays exhibited competitive sorption. The sorption isotherm curves can be classified as S-shaped. The sorptive capacity of the HDTMA-modified organoclays for p,p'-DDT were higher than those for p,p'-DDE, but the BTMA-modified organoclays showed a reverse trend. This can be attributed to the different structures and shapes of organic cations, giving different sorptive mechanisms. The p,p'-DDT and p,p'-DDE sorption onto HDTMA-modified organoclays were caused by chemical interaction, with the BTMA modified organoclays occuring due to physical sorption. 相似文献
Laboratory incubation trials were conducted to investigate the effects of several factors on the persistence as well as the
dissipation of three synthetic pyrethroid pesticides in red soils obtained from the Yangtze River Delta region in China. The
pyrethroids selected for investigation were cypermethrin, fenvalerate, and deltamethrin, which continue to be used extensively
to control pests on farmland in the region despite the concern that they are highly toxic to certain vertebrate and mammalian
species. Data from this exploratory study showed that the dissipation half-lives (T1/2) tended to correlate with soil pH and soil organic matter contents, but not with soil cation-exchange capacity. The T1/2 values were seen to be shorter in soil samples fertilized with glucose than without. The rates of pyrethroid dissipation
also tended to increase with increasing initial soil concentration, but were largely unaffected by whether the pesticides
were present in the soil separately or as a mixture. Another noteworthy observation is that microbial activity appeared to
dominate the degradation process. Findings of this type could offer valuable clues for future research directions in reducing
pesticide persistence in soil, which in turn could lead to the ultimate reduction of environmental pollution caused by pyrethroid
application to farmland in the region.
Project supported by Chinese Academy of Sciences (Project No. KSCX2-YW-N-038) and the National Key Basic Research Support
Foundation (973), China (No. 2002CB4108010). 相似文献
The aim of this study was to assess the acute health effects of individual ozone (O3) exposure on the respiratory system in the elderly. A total of 40 non-smoking elderly volunteers completed personal 24 h of measurement for O3 and fine particulate matter (PM2.5). To assess health effects, we measured the pulmonary function and five inflammatory biomarkers in exhaled breath condensate (EBC), including interleukin-2 (IL-2), interferon-γ (IFN-γ), prostaglandin E2 (PGE2), and tumor necrosis factor α/β (TNFα/β). We used the generalized additive model to analyze the association between O3 and these health effects, after adjusting PM2.5, BMI, and sex as confounders. As a result, we found a negative correlation between O3 and forced vital capacity (FVC) or forced expiratory volume-one second (FEV1). With the increasing of O3 by 10 μg/m3, FVC and FEV1 decreased by 0.13 L (95% CI 0.01, 0.26) and 0.11 L (95% CI 0.02, 0.20), respectively. We found no statistical significance between O3 and biomarkers in EBC. The results suggested that individual 24-h O3 exposure was associated with decreased pulmonary function in the elderly.
Chlorinated hydrocarbons are the most common organic pollutants in groundwater systems worldwide. In this study, we developed bio-beads with immobilized anaerobic bacteria, zero-valent iron (ZVI), and activated carbon (AC) powder and evaluated their efficacy in removing 1,1,1-trichloroethane (TCA) from groundwater. Bio-beads were produced by polyvinyl alcohol, alginate, and AC powder. We found that the concentration of AC powder used significantly affected the mechanical properties of immobilized bio-beads and that 1.0 % (w/v) was the optimal concentration. The bio-beads effectively degraded TCA (160 mg L?1) in the anaerobic medium and could be reused up to six times. The TCA degradation rate of bio-beads was 1.5 and 2.3 times greater, respectively, than ZVI + AC treatment or microbes + AC treatment. Measuring FeS produced by microbial reactions indicated that TCA removal occurred via FeS-catalyzed dechlorination. Analysis of clonal libraries derived from bio-beads demonstrated that the dominant species in the community were Betaproteobacteria and Gammaproteobacteria, which may contribute to the long-term stability of ZVI reactivity during TCA dechlorination. This study shows that the combined use of immobilized anaerobic bacteria, ZVI, and AC in bio-beads is effective and practical for TCA dechlorination and suggests they may be applicable towards developing a groundwater treatment system for the removal of TCA. 相似文献
The aim of this research was to reuse blast furnace slag (BFS) as a mud cake modifier (MCM) to improve the annular isolation quality in oil and gas wells. For the optimum formula of drilling fluid, the effects of MCM on the drilling fluid rheology were investigated. The relationship between the MCM addition and shear strength at cement–formation interface (SSCFI) was evaluated. The experimental results showed that the optimized formula of the drilling fluid has 1.0 wt% MCM and 0.5 wt% XY-27. The simulation results showed that SSCFI increased significantly with the addition of MCM. Based on the mechanism analysis of BFS as an MCM to improve SSCFI, it is found that the transformation of mud cake to agglomerated cake can be the main reason. The application results showed that the success rate of five wells reached 100%, and the rate of quality in cement was 100%. Especially, the average high quality rate of five wells reached 83.7%. Compared with conventional methods, the average high quality rate is increased by 32.6% points. This research provides a new way for sustainable utilization of BFS. 相似文献