Preconcentration of trace arsenite and arsenate with titanium dioxide nanoparticles and subsequent determination by silver diethyldithiocarbamate spectrophotometric method.

A novel method of preconcentration of trace arsenite and arsenate by using titanium dioxide nanoparticles as adsorbent was described. The concentrations of preconcentrated arsenite and arsenate were determined by a silver diethyldithiocarbamate spectrophotometric method without desorption. Batch adsorption experiments were carried out as a function of the pH, contact time, amount of titanium dioxide nanoparticles, and solution volume. In the pH range 5 to 6, adsorption rates of arsenite and arsenate were higher than 98%. The calibration coefficient was 0.9991, and the linear range was 0 to 100 microg/L. The developed method was precise, with the relative standard deviation <5% at concentration level of 10 microg/L, with a detection limit (3sigma, n=6) of 0.44 microg/L. The accuracy of the method for total arsenic was validated by standard reference materials (SRM 3103a) (National Institute of Standards and Technology, Gaithersburg, Maryland). The method was also applied to the analysis of arsenite and arsenate in natural water samples to verify the accuracy. The recovery values remained in a narrow range, from 95 to 103%.     

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The cover image is based on the Original Article Noninvasive prenatal paternity testing by means of SNP-based targeted sequencing by Jacqueline Chor Wing Tam et al., https://doi.org/10.1002/pd.5595 .

     

浅层淹水条件下不同施肥处理对黑土温室气体排放的影响

以东北黑土区长期耕作土壤为对象,通过室内培养试验研究了浅层淹水条件下不同施肥处理对黑土温室气体排放的影响.结果表明,浅层淹水条件下,与不施肥对照处理相比,单施氮肥处理对土壤CO₂排放没有显著影响,氮肥配施猪粪或者秸秆则显著促进了CO₂的排放,使得CO₂排放速率提高了一个数量级,氮肥配施秸秆处理的CO₂排放量最高.浅层淹水条件下,与不施肥对照处理相比,施用氮肥显著促进了土壤N₂O的排放.而与单施氮肥处理相比,氮肥配施猪粪和秸秆则显著抑制了N₂O的排放,表现为土壤对N₂O的微量吸收,氮肥配施秸秆处理的N₂O吸收量相对较高.浅层淹水条件下施用氮肥抑制了土壤CH₄的排放,而与单施氮肥处理相比,氮肥配施猪粪或者秸秆则促进了土壤CH₄的排放.     

纳污河流抗性基因和微生物群落相关性

通过Miseq高通量测序分析和荧光定量PCR技术,研究某纳污河流中四环素类与磺胺类抗性基因（ARGs）的分布特征、传播情况及微生物群落结构相关性.结果表明：在河流地表水与沉积物中均检测到四环素类抗性基因tetA和tetB与磺胺类抗性基因sul1和sul2,四环素类抗性基因和磺胺类抗性基因的绝对丰度分别为5.09×10³~1.26×10⁷,3.94×10⁵~1.32×10⁹copics/L,磺胺sul1抗生素抗性基因丰度显著高于其它基因;河流主要优势菌门为Proteobacteria,Bacteroidetes,Firmicutes,Actinobacteria和Cyanobacteria,其平均总相对丰度占总比例的95.62%,且总体差异较小.抗性基因与微生物群落冗余分析显示,Methylotenera菌属是影响tetA抗性基因分布丰度的主要因素,Dechloromonas和Clostridium sensu stricto 1菌属是影响tetB抗性基因分布丰度的主要因素,Dechloromonas、Clostridium sensu stricto 1和Methylotenera菌属是影响sul1、sul2抗性基因分布丰度的主要因素.     

Distribution of health costs of pesticide use by household economy

We observed skewed distribution across household of benefits of pesticide use in vegetable farming in Nepal. However, economic burden or harm of pesticide use and exposure by household economy is poorly studied. It is hypothesized that exaggerated and incompetent pesticide use is likely to affect human health that may lead to decline in human productivity, and economic loss––that may further marginalize farmers. Thus, a study was conducted in the Ansi khola watershed of Kavrepalanchowk District of central Nepal. The primary aim of the study was to value risks of pesticide use and to estimate health costs of exposure by household category. We grouped household into “large-scale” who owns more than 1 ha of agricultural land, “small-scale” having <0.5 ha and “medium-scale” in between >0.5 and <1 ha. Data were collected through (1) an initial household survey conducted from May to June 2008, (2) monthly visit surveys accomplished from June to November 2008 and (3) a final household survey conducted during November to December 2009. The cost of pesticide use and exposure was highest for medium-scale household; however, the economic burden in relation to incomes was the highest for small-scale household. On the basis of area under vegetables, small-scale household incurred 23 % higher economic burdens compared to the large-scale household. Overall, the cost of pesticide use and exposure amounted 15 % of agricultural income and/or 5 % of gross household income. For small-scale households, the cost was equivalent to 18 % of agricultural income and 6 % of gross income. Small-scale households are not only deprived from benefits of agriculture intensification, but also incurred highest burden of pesticide use.     

一种船舶失控情况下桥区水域范围界定方法

为分析船舶失控状态下船-桥碰撞概率分布特征,定量界定船舶失控状态下桥区水域范围,提高桥区通航安全保障水平,对界定方法进行研究。以失控状态下船舶的运动模型为基础,建立基于失控运动特征的船-桥碰撞概率计算模型。在此基础上,根据船-桥碰撞概率可接受标准定量界定桥区水域范围。为验证算法的合理性,运用蒙特卡洛法模拟出不同气象、水文条件和船舶失控状态下的船-桥碰撞概率,基于随机模拟结果,计算出不同船-桥碰撞概率条件下桥区水域范围。仿真结果表明:用该方法界定的桥区水域范围与当前海事主管部门经验设置的范围一致。