Model forecasts of atrazine in Lake Michigan in response to various sensitivity and potential management scenarios

For more than forty years, the herbicide atrazine has been used on corn crops in the Lake Michigan basin to control weeds. It is usually applied to farm fields in the spring before or after the corn crop emerges. A version of the WASP4 mass balance model, LM2-Atrazine, was used to assess the impact of the historical and future usage of this chemical on lake water concentrations. Long-term model forecasts were performed under various sensitivity and potential management scenarios. The model was calibrated to available lake data and results indicate that atrazine, under average conditions, is decaying very slowly in the lake (0.009/year). This kinetic decay translates into a half-life estimate of 77 years. If the average condition scenario were assumed to remain constant into the future and reflective of conditions in January 1, 2005, it is expected that the lake (excluding Green Bay) would eventually reach a volume-weighted average atrazine concentration of approximately 67 ng/L in the year 2157 (current model prediction is 48 ng/L for year 2011). These forecasted lake-wide concentrations are below known water quality criteria for the protection of aquatic ecosystems.     

废水中有机磷乐果降解菌的筛选及作用条件

由于乐果等有机磷农药的大量使用引起的土壤及水环境污染问题正威胁着生态安全及人类健康。微生物法降解有机磷农药因其经济有效性近年来成为研究的热点。实验采用室内培养方法,从吉化农药厂废水污泥中分离筛选出一株能在高浓度农药乐果中生长的细菌菌株。结果表明,该菌株最适生长pH值为7．0左右,具有相对稳定的pH值生长范围（pH6．0～8．0）,最适生长温度为30℃,3天后生长进入稳定期;得到的菌株对高浓度的乐果具有一定耐受性,在pH7．0、30℃温度条件下,1天内就可对乐果具有好的降解效果。     

表层稀土掺杂PbO_2电极及对苯酚电催化氧化性能研究

以钛电极为基体,用热分解法制备Sn-Sb中间层,电沉积方法制备稀土La掺杂PbO2电极,优化了制备改性PbO2电极的电沉积温度、电沉积时间及稀土掺杂量。以苯酚废水为目标有机物,借助于苯酚去除情况分析电极的电催化氧化能力;分析了电极结构与电催化特性之间的关系。采用SEM、EDX和XRD分析了制备电极的表面形貌、元素组成、晶体结构。实验结果表明:电沉积液温度50℃,电沉积2 h,稀土镧掺杂量4∶1的PbO2电极降解苯酚电催化性能有明显改善,其去除率达到90.9%。     

γ辐照后TBP—煤油对^95Zr的萃取和保留

研究了用不同浓度HNO_3预平衡和经γ辐照不同剂量后的TBP-煤油对~(95)Zr的萃取行为。测定了0.01mol/1HNO_3,5%Na_2CO_3洗涤后的有机相中~(95)Zr的保留百分率。比较了辐照后的TBP-煤油用碱和水萃洗分离得到的三个组份以及HDBP等7种辐解产物对~(95)Zr的萃取和洗涤后有机相中的保留情况。结果表明~(95)Zr的萃取和洗涤后的保留与溶剂所受的辐照剂量和预平衡酸度均有关系。在辐解产物中,单烷基长链酸性磷酸酯和异羟肟酸对Zr的萃取影响都较严重。前者在碱洗时容易产生乳化,而后者在碱洗后对Zr的保留更为严重。     

The significance of fullerene electron acceptors in organic solar cell photo-oxidation

Stability of organic solar cells requires development before their commercialisation is possible. This review will give a brief overview of organic solar cells and their stability, before focussing on the photochemical stability of the active layer. The photo-oxidation of the donor polymers will be looked at first which has been studied quite extensively and then fullerene electron acceptors, such as widely used phenyl-C61-butyric acid methyl ester, which has been considerably less studied. It has been shown that oxidation of the fullerene cage on phenyl-C61-butyric acid methyl ester results in oxides with a deeper lowest unoccupied molecular orbital (LUMO) level than the fresh electron acceptor. These oxides act as electron traps, leading to deterioration of the blend photoconductivity. The significance of fullerene photo-oxidation on device stability has been indirectly shown via research on: photoconductivity; organic solar cells made with an oxidised fullerene derivative and organic field effect transistors. Techniques that could be developed to increase photochemical stability of fullerene electron acceptor resistance to photo-oxidation include: reducing its LUMO level; increasing its crystallinity or aggregation and changing its chemical structure. Improving the photochemical stability of organic solar cells would move us one step closer to a more accessible solar power.     

Effects of ozone treatment on pesticide residues in food: a review

In agriculture, pesticide residues have always posed a major safety hazard to human health. With the development of agricultural production and improvements in science and technology, additional methods for degradation of pesticide residues have emerged. Amongst them, ozone treatment recently became a popular method owing to its outstanding technical advantages. This review is an in-depth analysis of the mechanisms by which ozone treatment degrades pesticide residues. The main mechanism involves direct oxidation by oxygen atoms, and indirect oxidation driven by hydroxyl radicals. The effects of ozone treatment on pesticide residues in food with respect to the ozone concentration, duration of ozone treatment, type of food, variety of pesticides, level of pesticide residues and environmental factors have been discussed. Furthermore, the impact of ozone treatment on the quality of food is highlighted. Low levels of ozone result in minor changes to the visual and sensory characteristics of food. In addition, this article discusses several restrictions surrounding the current application of ozone treatment for the degradation of pesticide residues. More specifically, the most crucial issue is the potential toxicity of ozonation byproducts generated by the process, which is also the current focus of research on ozone treatment for the degradation of pesticide residues. After weighing the advantages and disadvantages of ozone treatment, it is recommended as a method of degrading pesticide residues.     

聚合物溶液流经多孔介质时剪切降解的实验研究

测定了３种分子量的浓度１００ｐｐｍ ＨＰＡＭ水溶液，以不同的剪切速度流过低、中、高３种渗透率的人造砂岩岩芯后的粘度和特性粘数损失。研究了流经多孔介质时的剪切除解与剪切速率、介质渗透率、分子量之间的关系，得到了一些定性规律。     

铁改性锐钛矿型TiO2降解有机物试验

研究以Fe3+改性TiO2光催化剂对有机物的处理效果,确定了它对甲醛溶液的光催化降解工艺条件。结果表明:所制备的Fe3+改性TiO2为锐钛矿型TiO2(A-TiO2)。可见光照射下,用自制的Fe3+改性的锐钛矿型TiO2降解甲醛溶液的优化条件是:20 mg.L-1的甲醛溶液中加入0.1647 g掺2%Fe3+(摩尔比)A-TiO2粉末,溶液pH=6,室温下恒温反应4 h,降解率达到70.90%。同样条件下,分别以Fe3+掺杂量为0,5%和8%的自制的A-TiO2为催化剂,甲醛的降解率分别为16.41%,32.09%和26.12%。     

褐煤催化降解生烃过程的动力学研究

利用微量热天平模拟装置，对山西繁峙褐煤进行了热降解模拟实验，考察了作为催化剂介质的粘土矿牧无机盐类对褐煤生烃过程的影响，求得了催化生烃过程的动力学参数。结果表明：催化剂介质不同程度也降低了热降解反应的表观活化能，从而加速了反应的进行。     

Degradation of phthalate esters in an activated sludge wastewater treatment plant

Efficient removal of phthalate esters (PE) in wastewater treatment plants (WWTP) is becoming an increasing priority in many countries. In this study, we examined the fate of dimethyl phthalate (DMP), dibutyl phthalate (DBP), butylbenzyl phthalate (BBP), and di-(2-ethylhexyl) phthalate (DEHP) in a full scale activated sludge WWTP with biological removal of nitrogen and phosphorus. The mean concentrations of DMP, DBP, BBP, and DEHP at the WWTP inlet were 1.9, 20.5, 37.9, and 71.9 μg/L, respectively. Less than 0.1%, 42%, 35%, and 96% of DMP, DBP, BBP, and DEHP was associated with suspended solids, respectively. The overall microbial degradation of DMP, DBP, BBP, and DEHP in the WWTP was estimated to be 93%, 91%, 90%, and 81%, respectively. Seven to nine percent of the incoming PE were recovered in the WWTP effluent. Factors affecting microbial degradation of DEHP in activated sludge were studied using [U-¹⁴C-ring] DEHP as tracer. First order rate coefficients for aerobic DEHP degradation were 1.0×10⁻², 1.4×10⁻², and 1.3×10⁻³ at 20, 32, and 43 °C, respectively. Aerobic degradation rates decreased dramatically under aerobic thermophilic conditions (<0.1×10⁻² h⁻¹ at 60 °C). The degradation rate under anoxic denitrifying conditions was 0.3×10⁻² h⁻¹, whereas the rate under alternating conditions (aerobic-anoxic) was 0.8×10⁻² h⁻¹. Aerobic DEHP degradation in activated sludge samples was stimulated 5-9 times by addition of a phthalate degrading bacterium. The phthalate degrading bacterium was isolated from activated sludge, and maintained a capacity for DEHP degradation while growing on vegetable oil. Collectively, the results of the study identified several controls of microbial PE degradation in activated sludge. These controls may be considered to enhance PE degradation in activated sludge WWTP with biological removal of nitrogen and phosphorus.