Degradation rates of CFC-11, CFC-12 and CFC-113 in anoxic shallow aquifers of Araihazar, Bangladesh

Chlorofluorocarbons CFC-11 (CCl(3)F), CFC-12 (CCl(2)F(2)), and CFC-113 (CCl(2)F-CClF(2)) are used in hydrology as transient tracers under the assumption of conservative behavior in the unsaturated and saturated soil zones. However, laboratory and field studies have shown that these compounds are not stable under anaerobic conditions. To determine the degradation rates of CFCs in a tropical environment, atmospheric air, unsaturated zone soil gas, and anoxic groundwater samples were collected in Araihazar upazila, Bangladesh. Observed CFC concentrations in both soil gas and groundwater were significantly below those expected from atmospheric levels. The CFC deficits in the unsaturated zone can be explained by gas exchange with groundwater undersaturated in CFCs. The CFC deficits observed in (3)H/(3)He dated groundwater were used to estimate degradation rates in the saturated zone. The results show that CFCs are degraded to the point where practically no (<5%) CFC-11, CFC-12, or CFC-113 remains in groundwater with (3)H/(3)He ages above 10 yr. In groundwater sampled at our site CFC-11 and CFC-12 appear to degrade at similar rates with estimated degradation rates ranging from approximately 0.25 yr(-1) to approximately 6 yr(-1). Degradation rates increased as a function of reducing conditions. This indicates that CFC dating of groundwater in regions of humid tropical climate has to be carried out with great caution.     

蚯蚓生态滤池处理农村生活污水现场试验研究

对蚯蚓生态滤池处理太湖流域农村生活污水进行现场试验研究.通过对蚯蚓同化容量与污染负荷进行单因素分析,得出蚯蚓生态滤池处理农村生活污水的运行参数与运行方式,并据此进行连续运行试验.结果表明,在表面水力负荷1 m3/(m2*d)、湿干比(布水时间和落干时间之比)1∶3、蚯蚓负荷(以单位体积填料中蚯蚓的质量计)12.5 g/L的条件下,蚯蚓生态滤池处理农村生活污水具有可行性与高效性,单级系统的COD、总氮、氨氮和总磷的去除率分别在81%、66%、82%和89%左右.改进蚯蚓床填料、设计通风结构和采取适宜运行方式,是蚯蚓生态滤池成功应用于农村生活污水处理的三大重要因素.     

膜基活化溶液中活化剂在回收温室气体CO2过程中的作用

将AMP和PZ作为活化剂添加于MDEA溶液中,形成活化溶液,研究了膜基活化溶液回收温室气体CO2性能,着重考察活化剂的活化作用和对膜接触器传质加强的影响,提出一个活化机理来解释活化现象,建立了阻力层方程模型, 并模拟膜基活化溶液回收CO2的传质过程。结果表明,活化剂对膜接触器传质的加强起到重要作用,具有双氨基环状结构的PZ对传质的加强作用高于具有空间位阻结构的AMP;活化溶液的CO2回收率和传质通量明显高于未活化的MDEA溶液,活化性能PZ＞AMP;活化剂的活化效应与分子结构有关;流体力学的改变对传质的影响有限,活化剂的反应动力学对传质的加强起主导作用;阻力层方程模型能较好地模拟膜基活化溶液回收CO2传质过程,传质通量和总传质系数的模型值与实验值符合较好。     

Wastewater-nitrogen removal using polylactic acid/starch as carbon source: Optimization of operating parameters using response surface methodology

The use of PLA/starch blends for nitrogen removal was achieved. The influence of different operating parameters on responses was verified using RSM. The conditions for desired responses were successfully optimized simultaneously. Blends material may have a promising application prospect in the future. Nitrogen removal from ammonium-containing wastewater was conducted using polylactic acid (PLA)/starch blends as carbon source and carrier for functional bacteria. The exclusive and interactive influences of operating parameters (i.e., temperature, pH, stirring rate, and PLA-to-starch ratio (PLA proportion)) on nitrification (Y₁), denitrification (Y₂), and COD release rates (Y₃) were investigated through response surface methodology. Experimental results indicated that nitrogen removal could be successfully achieved in the PLA/starch blends through simultaneous nitrification and denitrification. The carbon release rate of the blends was controllable. The sensitivity of Y₁, Y₂, and Y₃ to different operating parameters also differed. The sequence for each response was as follows: for Y₁, pH>stirring rate>PLA proportion>temperature; for Y₂, pH>PLA proportion>temperature>stirring rate; and for Y₃, stirring rate>pH>PLA proportion>temperature. In this study, the following optimum conditions were observed: temperature, 32.0°C; pH 7.7; stirring rate, 200.0 r·min^-1; and PLA proportion, 0.4. Under these conditions, Y₁, Y₂, and Y₃ were 134.0 μg-N·g-blend^-1·h^-1, 160.9 μg-N·g-blend^-1·h^-1, and 7.6 × 10³ μg-O·g-blend^-1·h^-1, respectively. These results suggested that the PLA/starch blends may be an ideal packing material for nitrogen removal.     

Distribution of thifluzamide,fenoxanil and tebuconazole in rice paddy and dietary risk assessment

Distribution behaviors of thifluzamide, fenoxanil, and tebuconazole applied to rice were investigated in South China. Analysis was by a modified QuEChERS method with gas chromatography (thifluzamide and fenoxanil) and liquid chromatography mass spectrometry (tebuconazole). Thifluzamide and tebuconazole partitioned mainly into the soil, with half-lives in the paddy soil of 12–14 and 5.3–7.8 days, respectively. Fenoxanil partitioned mainly into the rice plants, with half-lives of 3.3–4.4 days. The half-lives of thifluzamide, fenoxanil, and tebuconazole in paddy water were 0.17–0.89, 1.8–3.0, and 1.6–4.0 days, respectively. The residues in rice grains at the pre-harvest interval of 14 days were all below the established maximum limit values. The dietary risks assessed as hazard quotients at the pre-harvest interval were less than 1.     

重金属污染下龟壳攀鲈组织中ACP和AKP的活力比较

龟壳攀鲈是一种在极端污染水域中具备生存优势的鱼类,收集重污染区和轻污染区的龟壳攀鲈,并通过比较其体内各组织中的酸性磷酸酶(ACP)及碱性磷酸酶(AKP)活性来揭示其耐污能力。贵屿作为重污染区有4个采样点:大陇村、市上村、联堤村和北林村;潮州作为轻污染区有2个采样点:卧石村和洗马桥。水质结果表明,贵屿采样地水中的Pb、Cd、Cr、As、Hg含量分别是潮州采样点的27.6倍、3.9倍、5.8倍、3.9倍和3.5倍,说明贵屿采样地的污染远高于潮州的。酶活结果表明,在龟壳攀鲈所有组织中,内脏组织(胃肠、性腺、肝脏、脾脏、肾脏)中的ACP和AKP活力均高于外周组织(肌肉、鳞片、鳃);重金属污染均能提高攀鲈体内所有组织的ACP和AKP活力;AKP活性更容易受到重金属的影响,各组织的AKP活力增幅普遍超过ACP活力增幅;其中,受重金属影响最大的组织是脾脏,ACP和AKP活力可增长到2.37倍和6.21倍。这些结果说明了龟壳攀鲈可以通过显著升高内脏组织(如肠胃、肝脏、肾脏等)中ACP和AKP活性,以便更好地应对高污染环境;其中AKP更容易受到重金属的影响,适合用于作为评估污染的指标。     

固相萃取-气相色谱法测定水中硝基氯苯类化合物

建立固相萃取-气相色谱法测定水中15种硝基氯苯类化合物的方法。选用HLB柱为固相萃取柱,选用环己烷∶丙酮(3∶1,V∶V)混合溶剂作洗脱剂,得到方法检出限为0.011～0.040μg/L。空白水样加标回收率为73.6%～119%,相对标准偏差为6.1%～13.9%,精密度和准确度良好。对成分不复杂的实际水样进行测定,加标回收率为64.1%～118%,相对标准偏差为5.8%～15.6%,该方法能够基本满足成分不复杂的环境水体中痕量硝基氯苯类化合物的测定。     

我国典型南方城市臭氧污染特征

分析了我国典型南方城市的臭氧污染特征,选取我国4个有代表性的南方重点城市武汉、宁波、中山和南宁的2013—2015年监测数据,使用EXCEL、ORIGIN和MATLAB等统计软件开展研究,结果表明:我国南方典型城市的臭氧质量浓度分布有明显时间变化特征,超标时间跨度大,部分南方城市与氮氧化物存在较明显负相关性,相关系数高于-0.6;受城市所在不同地理位置、气象因素、大气扩散条件及可能的不同本地排放污染源构成等因素影响,4个城市的近3年臭氧浓度月均值、超标情况和年内峰值均存在一定差异和分组相似性;与部分气象因素也表现出显著相关性。     

研究海洋环境质量生物标准的意义及其内容

阐述研究制订海洋环境质量生物标准的必要性和重要意义，介绍生物标准应用的概况和国际上应用的鱼贝类污染物含量标准。依据海洋污染研究进展和我国海洋监测管理水平，探讨我国生物标准制订的内容，提出宜选用海洋双壳类，以有毒污染物含量以及微生物污染指标和赤潮毒素等为主要内容，研究制订适应我国国情的生物标准     

石油化工项目环境风险评价实例分析

环境风险评价是石油化工项目环境影响评价的一项重要内容。笔者以某拟建沥青厂为例,利用有关事故统计资料类比分析和世界银行推荐的爆炸危害关系式,对石油化工项目环境风险半定量评价进行了初步探讨。结果表明,该厂发生泄漏事故不会波及外环境,爆炸事故将造成厂区严重破坏并对局地大气环境产生一定影响。