除草剂莠去津对过氧化氢酶中酪氨酸微区的影响

应用紫外差光谱和荧光光谱研究了除草剂莠去津对过氧化氢酶中酪氨酸微区的影响.通过紫外差光谱发现,当9.1＜pH＜9.9之间变化时,差光谱吸收△A_260nm急剧变化,酪氨酸酚羟基的表观离解常数pK_侧链=9.5莠去津与过氧化氢酶作用后,可能是由于氢键的作用,紫外差光谱和荧光光谱都有一定的红移现象产生,但其表观离解常数未发生改变.SDS对其荧光性质有较大的影响;过氧化氢酶的荧光能被KI碰撞猝灭研究表明,酪氨酸残基可能是处于过氧化氢酶的亲水内核,莠去津可能与过氧化氢酶形成氢键,但对酪氨酸微区影响不大.     

Effects of Modified Starch and Different Molecular Weight Polyvinyl Alcohols on Biodegradable Characteristics of Polyvinyl Alcohol/Starch Blends

The common biodegradable properties of polymer make them an excellent pair for blending, and the water solubility of polyvinyl alcohol (PVA) makes it easy to mix evenly with the starch. In this study, PVAs with different molecular weights were blended with various compositions of cross-linked starch (CLS) to explore the effects of molecular weight of PVA on the biodegradable characteristics of the PVA/starch blends. Comparing the biodegradability of all the various PVA/starch blends, a PVA was singled out from the PVA/starch blends of higher biodegradability. Further, the chosen PVA was then blended with the acid-modified starch (AMS) to systematically investigate the effects of the modified processing of starch on the biodegradable characteristics of the PVA/starch blends. Differential scanning calorimetry (DSC) analysis of PVA and PVA/starch specimens reveal that the T_m values of PVA/starch specimens reduce gradually as their CLS or AMS contents increase. After the CLS is blended in PVAs of different molecular weights, the tensile strength (??_f) and elongation at break (??_f) values of (P₁₀₀S₀)G₂₀M₁ specimen increase and simultaneously reduce, respectively, as their molecular weights of PVA increase from about 80,000 (PVA_BF-17) to 120,000 (PVA_BF-26). The ??_f and ??_f values of the PVA/modified-starch blends decrease with an increase in the modified starch contents. The ??_f values of the PVA/AMS specimens decrease with an increase in the concentrations of hydrochloric acid. Comparing the ??_f values of the PVA/CLS specimens with those of the PVA/AMS specimens, the ??_f values of the PVA/CLS specimens are better than those of the PVA/AMS specimens. On the contrary, the ??_f values of the PVA/AMS specimens are better than those of the PVA/CLS specimens. According to the biodegradability of all the PVA/starch blends, PVA with higher molecular weights displays higher biodegradability. The biodegradability of the PVA/modified-starch blends increase as the modified starch contents of the PVA/modified-starch blends increase. As evidenced by the results of the biodegradability test, the biodegradability of the PVA/modified-starch blends, therein PVA is blended with 1N AMS, shows better biodegradability. The result of bio-reaction kinetics experiment can evaluate the decomposition tendency of the PVA/starch blends up to any biodegradable rate under ambient environment. Using the kinetic model of the first order reaction, it is estimated that 16.20?years and 12.47?years will be needed for the PVA_BF-17/starch blends, containing 20 and 40% of CLS respectively, to be degraded up to 70% under ambient environment. In addition, it is 1.68?years for the PVA_BF-26 blends with the 40% 2N AMS under decomposition environment while it is 1.94?years for the 40% 1N AMS. Overall, the decomposition potential of PVA/AMS specimens is better than PVA/CLS specimens. Furthermore, the 1N(26P₆₀AS₄₀)₁₀₀G₂₀M₁ specimen is coincidence the biodegradable material criteria of Environmental Protection Administration (EPA) of Taiwan.     

Leaching of heavy metals from solidified waste using Portland cement and zeolite as a binder

This study investigated the properties of solidified waste using ordinary Portland cement (OPC) containing synthesized zeolite (SZ) and natural zeolite (NZ) as a binder. Natural and synthesized zeolites were used to partially replace the OPC at rates of 0%, 20%, and 40% by weight of the binder. Plating sludge was used as contaminated waste to replace the binder at rates of 40%, 50% and 60% by weight. A water to binder (w/b) ratio of 0.40 was used for all of the mixtures. The setting time and compressive strength of the solidified waste were investigated, while the leachability of the heavy metals was determined by TCLP. Additionally, XRD, XRF, and SEM were performed to investigate the fracture surface, while the pore size distribution was analyzed with MIP. The results indicated that the setting time of the binders marginally increased as the amount of SZ and NZ increased in the mix. The compressive strengths of the pastes containing 20 and 40wt.% of NZ were higher than those containing SZ. The compressive strengths at 28 days of the SZ solidified waste mixes were 1.2-31.1MPa and those of NZ solidified waste mixes were 26.0-62.4MPa as compared to 72.9MPa of the control mix at the same age. The quality of the solidified waste containing zeolites was better than that with OPC alone in terms of the effectiveness in reducing the leachability. The concentrations of heavy metals in the leachates were within the limits specified by the US EPA. SEM and MIP revealed that the replacement of Portland cement by zeolites increased the total porosity but decreased the average pore size and resulted in the better containment of heavy ions from the solidified waste.     

Spatial and temporal distributions of air pollutant emissions from open crop straw and biomass burnings in China from 2002 to 2016

Environmental Chemistry Letters - Open biomass burning (OBB) with a main contribution from open crop straw burning (OCSB) plays a key role in the formation of heavy haze episodes during harvest...     

Residential emissions predicted as a major source of fine particulate matter in winter over the Yangtze River Delta,China

Environmental Chemistry Letters - Air pollution is an increasingly critical health issue responsible for numerous diseases and deaths worldwide. In China, to address severe air pollution in the...     

淹水条件对不同土壤中稀土元素钕形态分布的影响

以旱作条件为参照,研究淹水条件对钕形态分布的影响.结果表明,淹水条件对内源钕B1态(水溶态、可交换态与碳酸盐结合)、B2态(铁锰氧化物结合态)和B3态(有机质及硫化物结合态)的分布无显著影响.对于外源钕,淹水条件使B1和B3态浓度增加,而B2态浓度则因土壤性质而异,中性土壤中浓度稳定,酸性和碱性土壤中浓度分别增高和降低,其机制有待进一步研究;淹水条件对黄红壤和黄褐土中外源钕无显著影响,而砂姜黑土则相反;两种条件下,3种土壤中B2和B3态浓度顺序相同,B2态浓度顺序为:黄红壤黄褐土砂姜黑土,B3态浓度顺序为:砂姜黑土黄褐土黄红壤,而B1态在黄红壤中浓度最大;外源钕有进入残渣态的趋势,但并不明显,且不同土壤的各形态对残渣态的贡献不同.     

地理信息系统在环境安全中的应用与发展

随着社会的发展,环境安全的呼声日益高涨,信息时代的到来,使随之发展起来的地理信息系统成为解决环境问题的重要方法。从环境安全的角度出发,论述了地理信息系统在环境安全领域的应用及其在环境领域的发展。     

沸石负载壳聚糖对铬（Ⅵ）的吸附平衡和动力学研究

采用沸石负载壳聚糖作为吸附剂,对溶液中铬（Ⅵ）的吸附平衡和吸附动力学进行了研究。结果表明,溶液中铬（Ⅵ）在沸石负载壳聚糖上的等温吸附数据符合Freundlich模型;吸附体系属于物理吸附,吸附状态属于多层吸附;吸附行为符合二级速率方程。     

一体式膜生物反应器膜污染影响因素研究

试验采用聚丙烯中空纤维膜,通过正交试验考察了膜通量、抽停时间、曝气量对膜过滤压力的影响,得出适合的膜通量是减缓膜污染的决定性因素。并确定了适宜的运行条件：膜通量5L／（m2·h）,抽吸时间8min,停抽时间2min,曝气量0．6m3／h;同时考察了EPS中多糖和蛋白质对膜污染的影响,得出多糖是主要的污染物质。     

Characterizing the solid–solution partitioning coefficient and plant uptake factor of As,Cd, and Pb in California croplands

In risk assessment models, solid–solution partition coefficient, K_d, and plant uptake factor, PUF, are often employed to depict the fate and transport of trace elements in soils. The trustworthiness of risk assessments depends on the reliability of the parameters used. In this study, we examined K_d and PUF for As, Cd and Pb based on soils and plant tissues obtained from 70 crop production fields in California. We also examined the California portion of a nationwide survey of trace elements in cropland soils conducted by the Soil Survey, Natural Resources Conservation Service, USDA. Results showed that the K_d and PUF for cropland soils are probabilistic in nature and follow log-normal distributions. The trace element concentration of the soil solution did not appear to be a more appropriate estimator of PUF than the total soil element content. The K_d used in the CDFA (California Department of Food and Agriculture) study had a much wider range than that could occur in California croplands while the PUF used in the CDFA risk assessment was comparable to patterns observed in the field measurements.