Mercury species of sediment and fish in freshwater fish ponds around the Pearl River Delta, PR China: human health risk assessment

This study investigated total mercury (THg) and methylmercury (MeHg) concentrations in five species of freshwater fish and their associated fish pond sediments collected from 18 freshwater fish ponds around the Pearl River Delta (PRD). The concentrations of THg and MeHg in fish pond surface sediments were 33.1-386 ng g(-1) dry wt and 0.18-1.25 ng g(-1) dry wt, respectively. The age of ponds affected the surface sediment MeHg concentration. The vertical distribution of MeHg in sediment cores showed that MeHg concentrations decreased with increasing depth in the top 10 cm. In addition, a significant correlation was observed between %MeHg and DNA from Desulfovibrionacaea or Desulfobulbus (p<0.05) in sediment cores. Concentrations of THg and MeHg in fish muscles ranged from 7.43-76.7 to 5.93-76.1 ng g(-1) wet wt, respectively, with significant linear relationships (r=0.97, p<0.01, n=122) observed between THg and MeHg levels in fish. A significant correlation between THg concentrations in fish (herbivorous: r=0.71, p<0.05, n=7; carnivorous: r=0.77, p<0.05, n=11) and corresponding sediments was also obtained. Risk assessment indicated that the consumption of largemouth bass and mandarin fish would result in higher estimated daily intakes (EDIs) of MeHg than reference dose (RfD) for both adults and children.     

Distribution, speciation and availability of antimony (Sb) in soils and terrestrial plants from an active Sb mining area

Here, we present one of the first studies investigating the mobility, solubility and the speciation-dependent in-situ bioaccumulation of antimony (Sb) in an active Sb mining area (Xikuangshan, China). Total Sb concentrations in soils are high (527-11,798 mg kg⁻¹), and all soils, including those taken from a paddy field and a vegetable garden, show a high bioavailable Sb fraction (6.3-748 mg kg⁻¹), dominated by Sb(V). Elevated concentrations in native plant species (109-4029 mg kg⁻¹) underpin this. Both chemical equilibrium studies and XANES data suggest the presence of Ca[Sb(OH)₆]₂, controlling Sb solubility. A very close relationship was found between the citric acid extractable Sb in plants and water or sulfate extractable Sb in soil, indicating that citric acid extractable Sb content in plants may be a better predictor for bioavailable Sb in soil than total acid digestible Sb plant content.     

蜈蚣草吸收和氧化As(Ⅲ)的试验及动力学研究

通过蜈蚣草室内水培试验,研究了蜈蚣草对As(Ⅲ)的吸收特性和动力学规律.结果表明,蜈蚣草在吸收As(Ⅲ)的同时,可以将As(Ⅲ)氧化为As(Ⅴ),然后再进行吸收;当培养液中As(Ⅲ)初始浓度较低(10.00 mg/L)时,蜈蚣草对砷的吸收和氧化过程较好地符合一级动力学规律,表观速率常数为0.104 h-1,当初始质量浓...     

环境因素对聚乙烯醇降解菌系降解效果的影响研究

针对在前期研究中已筛选到的一种聚乙烯醇(PVA)降解混合菌系,考察了种龄、菌悬液接种量、培养基装液量、培养温度、初始pH、渗透压及光照等外部环境因素对其PVA降解能力的影响.结果表明,种龄对混合菌系降解PVA的能力影响较小,实际运用中保持种龄为24～48 h较佳;菌悬液接种量过多时,会影响其正常生长,最佳的接种量为4～...     

新型复合混凝吸附药剂对无铅皮蛋废水的处理

皮蛋废水水质相当复杂,既属于含重金属离子废水,又属于中等浓度含盐有机废水.针对皮蛋废水特点,采用混凝+吸附方法预处理皮蛋废水,将PAC与粉煤灰按2:5的投加比混合复制成一种新型复合混凝吸附剂,通过正交实验考察了复合药剂的较佳处理条件.结果表明,在投加量为5 g/L,pH为6.5左右,搅拌时间约为14 min,处理温度为...     

草甘膦母液膜分离的电渗析预处理

研究了用电渗析法去除草甘膦母液中影响膜通量的亚磷酸根,主要考察了pH值、工作电压、反应时间和温度等因素对亚磷酸根去除率的影响,并对电渗析预处理后母液纳滤膜分离的膜通量进行实验验证。实验表明：淡化液、浓缩液流量为30 L/h,pH值约为8.1,工作电压为20 V,反应时间为2 h左右,温度〈30℃时,电渗析对母液中亚磷酸...     

氨氮浓度对次氯酸钠消毒中水的影响

研究了氨氮浓度对次氯酸钠消毒中水的影响,讨论了中水氨氮浓度、氯胺浓度、总余氯浓度、消毒接触时间和总大肠菌群指标的变化关系。结果表明,氨氮随消毒接触时间呈先降低再升高的趋势,中水氨氮浓度越高,其变化幅度越小,反之,则变化幅度较大;氯胺浓度随消毒接触时间的延长先升高再降低,而总余氯量则逐渐降低,并有一定的持续消毒作用;此外,总余氯随次氯酸钠投加量的增加呈先升高后降低再逐渐升高的趋势,整个反应过程符合折点加氯消毒理论;当次氯酸钠投加量与氨氮的比值（以后简称C1／N）为25／1时,氨氮消耗掉的次氯酸钠量最多,生成的总余氯量最少;当C1／N比大于25／1时,消毒后中水氨氮浓度为零,反之,则随C1／N比升高逐渐降低;而当氨氮浓度相同时,中水消毒达标的主要影响因素是水中总大肠菌群的数量。     

UASB-好氧曝气-深度处理工艺处理聚酯废水和回用

介绍了气提-厌氧-好氧曝气-深度处理工艺在聚酯废水处理及回用技术中的实际应用,分析并总结了工程设计及运行的经验。实践表明,运用气提塔先对高浓度聚酯废水进行预处理,可以去除废水中大部分有机物,保证后续生化处理的稳定运行。经气提-厌氧-好氧曝气-深度处理后可以回用于生产过程中。该工艺具有运行稳定和处理效率高等优点,为企业带来了良好的经济效益和社会效益。     

造纸废水处理工艺试验研究

采用UASB-A/O工艺处理难降解造纸废水.试验结果表明:在系统稳定运行阶段,UASB的HRT为24 h的条件下,平均进水COD为2 777 mg/L时,平均UASB出水COD为l 274 mg/L,平均二沉池出水COD为210mg/L,平均总COD去除率为92.4％;平均进水ρ(氨氮)为40.7 mg/L时,平均UA...     

一种面向灾害应急的UAV影像快速拼接方法

洪涝、地震等自然灾害发生突然,特别是对城郊设防水平较低地区,短时间内能造成巨大的损失.及时、准确、快速地获得足够的灾情信息是减灾救灾的前提;依靠无人机采集的灾区遥感影像越来越成为减灾部门提取第一手灾情信息的首选数据源.结合无人机影像特点,优化利用影像局部不变特征进行特征匹配,通过RANSAC算子剔除匹配粗差,并用变换优化法求取最佳变换模型参数,然后采用基于动态规划的最佳拼接缝搜索策略和加权平均相结合的融合策略,在保证灾害应急精度要求的前提下,很好地消除了拼接缝和“融合鬼影”现象,为城郊区应急情况下的灾情信息获取提供了新的技术手段和支持.