利用PARAFAC及SOM研究不同来源及粒径胶体的三维荧光光谱特征

利用三维荧光光谱法(3D-EEM)结合平行因子分析(PARAFAC)和自组织神经网络分析(SOM),解析了不同来源水体中不同粒径胶体的荧光特性,同时与挑峰法进行比较,以期寻找一种更好的分析天然胶体来源、粒径、荧光特性间关系的方法.基于PARAFAC模型,研究区水体中不同粒径胶体共解析出2个类腐殖质荧光峰(C1和C3)及3个类蛋白荧光峰(C2、C4和C5).其中,300 k Da~1μm分级胶体荧光强度最高,C1、C2、C3组分的荧光强度随粒径增大而增强,C4、C5组分的荧光强度随粒径增大而减弱.不同来源胶体(生活污水:进水和出水;农业污水:大盈和天恩桥;天然水体:吴淞口)的荧光强度变化大致规律为:吴淞口进水大盈天恩桥出水.SOM分析结果与PARAFAC一致,且可视化程度更高,但EEM-SOM模型存在输入变量多、兼具挑峰法缺点的问题.而PARAFAC-SOM模型不仅兼具了前两者的优点,还具有输入变量少、运行时间短、可靠性高等优点.同时,该模型还成功应用于胶体其他理化参数的分析(Parameters-SOM模型),使得前期工作结果系统性更强、更直观.因此,PARAFAC-SOM模型是相对较好的分析天然胶体来源、粒径、荧光特性间关系的方法.     

Inorganic arsenic: A non-genotoxic carcinogen

Inorganic arsenic induces a variety of toxicities including cancer. The mode of action for cancer and non-cancer effects involves the metabolic generation of trivalent arsenicals and their reaction with sulfhydryl groups within critical proteins in various cell types which leads to the biological response. In epithelial cells, the response is cell death with consequent regenerative proliferation. If this continues for a long period of time, it can result in an increased risk of cancer. Arsenicals do not react with DNA. There is evidence for indirect genotoxicity in various in vitro and in vivo systems, but these involve exposures at cytotoxic concentrations and are not the basis for cancer development. The resulting markers of genotoxicity could readily be due to the cytotoxicity rather than an effect on the DNA itself. Evidence for genotoxicity in humans has involved detection of chromosomal aberrations, sister chromatid exchanges in lymphocytes and micronucleus formation in lymphocytes, buccal mucosal cells, and exfoliated urothelial cells in the urine. Numerous difficulties have been identified in the interpretation of such results, including inadequate assessment of exposure to arsenic, measurement of micronuclei, and potential confounding factors such as tobacco exposure, folate deficiency, and others. Overall, the data strongly supports a non-linear dose response for the effects of inorganic arsenic. In various in vitro and in vivo models and in human epidemiology studies there appears to be a threshold for biological responses, including cancer.     

Role of complex organic arsenicals in food in aggregate exposure to arsenic

For much of the world''s population, food is the major source of exposure to arsenic. Exposure to this non-essential metalloid at relatively low levels may be linked to a wide range of adverse health effects. Thus, evaluating foods as sources of exposure to arsenic is important in assessing risk and developing strategies that protect public health. Although most emphasis has been placed on inorganic arsenic as human carcinogen and toxicant, an array of arsenic-containing species are found in plants and animals used as foods. Here, we 2evaluate the contribution of complex organic arsenicals (arsenosugars, arsenolipids, and trimethylarsonium compounds) that are found in foods and consider their origins, metabolism, and potential toxicity. Commonalities in the metabolism of arsenosugars and arsenolipids lead to the production of di-methylated arsenicals which are known to exert many toxic effects. Evaluating foods as sources of exposure to these complex organic arsenicals and understanding the formation of reactive metabolites may be critical in assessing their contribution to aggregate exposure to arsenic.     

Oxidation state specific analysis of arsenic species in tissues of wild-type and arsenic (+ 3 oxidation state) methyltransferase-knockout mice

Arsenic methyltransferase(As3mt) catalyzes the conversion of inorganic arsenic(i As) to its methylated metabolites, including toxic methylarsonite(MAs~Ⅲ) and dimethylarsinite(DMAs~Ⅲ). Knockout(KO) of As3 mt was shown to reduce the capacity to methylate i As in mice. However, no data are available on the oxidation states of As species in tissues of these mice. Here, we compare the oxidation states of As species in tissues of male C57BL/6 As3mt-KO and wild-type(WT) mice exposed to arsenite(iA s~Ⅲ) in drinking water. WT mice were exposed to50 mg/L As and As3mt-KO mice that cannot tolerate 50 mg/L As were exposed to 0, 15, 20, 25 or30 mg/L As. iA s~Ⅲaccounted for 53% to 74% of total As in liver, pancreas, adipose, lung, heart, and kidney of As3mt-KO mice; tri- and pentavalent methylated arsenicals did not exceed 10% of total As. Tissues of WT mice retained iA s and methylated arsenicals: iA s~Ⅲ, MAs~Ⅲand DMAs~Ⅲ represented 55%‐68% of the total As in the liver, pancreas, and brain. High levels of methylated species, particularly MAs~Ⅲ, were found in the intestine of WT, but not As3mt-KO mice,suggesting that intestinal bacteria are not a major source of methylated As. Blood of WT mice contained significantly higher levels of As than blood of As3mt-KO mice. This study is the first to determine oxidation states of As species in tissues of As3mt-KO mice. Results will help to design studies using WT and As3mt-KO mice to examine the role of iA s methylation in adverse effects of iA s exposure.     

pH-dependent release characteristics of antimony and arsenic from typical antimony-bearing ores

The pH-dependent leaching of antimony (Sb) and arsenic (As) from three typical Sb-bearing ores (Banxi, Muli and Tongkeng Antimony Mine) in China was assessed using a pH-static leaching experiment. The pH changes of the leached solutions and pH-dependent leaching of Sb and As occurred in different ways. For the Banxi and Muli Sb ores, alkaline conditions were more favorable for the release of Sb compared to neutral and acidic conditions, but the reverse was true for the pH-dependent release of As. For the Tongkeng Sb ore, unlike the previous two Sb-bearing ores, acidic conditions were more favorable for Sb release than neutral and alkaline conditions. The ores with lower Sb and As contents released higher percentages of their Sb and As after 16 day leaching, suggesting that they are the largest potential sources of pollution. This work may provide key information on the geochemistry of Sb and As in the weathering zone.     

基于非对称流场流分离技术的纳米银分离监测方法

以纳米银(AgNPs)作为典型的纳米颗粒物,利用非对称流场流分离技术构建纳米颗粒物的分离监测方法。制备了柠檬酸盐稳定的AgNPs分散液,采用透射电镜、紫外可见分光光度计、Zeta电位分析仪对AgNPs分散液进行了表征。结果表明,AgNPs半径多数小于10 nm,最大吸收波长为400 nm,Zeta电位为-42.56 m V。采用非对称流场流分离仪对AgNPs进行粒径分离,得到UV-Vis信号谱图,并收集得到半径小于10 nm、10~30 nm、30~50 nm、50~70 nm、70~100nm范围的AgNPs颗粒,结合电感耦合等离子体质谱仪测定每个粒径范围内AgNPs的质量浓度。结果表明,该方法重现性良好,AgNPs在半径小于10 nm的范围内达到了UV-Vis吸收峰值,响应信号最高为0.022 5~0.027 5 V,表明半径小于10 nm的AgNPs浓度较高。半径小于10 nm、10~30 nm、30~50 nm、50~70 nm、70~100 nm范围内AgNPs的质量浓度分别为(1 021.86±61.74)μg/L、(323.23±45.83)μg/L、(72.90±32.14)μg/L、(44.64±9.28)μg/L、(39.12±5.04)μg/L,回收率为43.96%±0.84%。     

Evaluation of soil characteristics potentially affecting arsenic concentration in paddy rice (Oryza sativa L.)

Paddy rice may contribute considerably to the human intake of As. The knowledge of soil characteristics affecting the As content of the rice plant enables the development of agricultural measures for controlling As uptake.During field surveys in 2004 and 2006, plant samples from 68 fields (Italy, Po-area) revealed markedly differing As concentration in polished rice. The soil factors total As_{(aqua regia)}, pH, grain size fractions, total C, plant available P_(CAL), poorly crystalline Fe_(oxal.) and plant available Si_(Na-acetate) content that potentially affect As content of rice were determined.A multiple linear regression analysis showed a significant positive influence of the total As_{(aqua regia)} and plant available P_(CAL) content and a negative influence of the poorly crystalline Fe_(oxal.) content of the soil on the As content in polished rice and rice straw.Si concentration in rice straw varied widely and was negatively related to As content in straw and polished rice.     

水体冻结过程中荧光物质的迁移转化研究

本研究利用荧光区域积分法考察了在水体冻结过程中,溶解性有机物(DOM)组分中荧光物质的迁移转化.同时,利用XAD树脂,将DOM分为3个部分:疏水性有机酸(HPO-A)、过渡亲水性有机酸(TPI-A)和亲水性有机物(HPI).结果表明,在水体冻结过程中,HPO-A、TPI-A和HPI的DOC浓度在水相中逐渐增加,而在冰相中先减少后增加,并且这3种DOM组分在冰、水两相间的分配系数排序为:HPITPI-AHPOA.在水体冻结过程中,水相中HPO-A和HPI的总累计荧光强度(ΦT,n)值,以及冰相中3种DOM组分的总ΦT,n值随冻结时间的变化趋势均为先降低后升高.在水体冻结过程中,水相中3种DOM组分的类腐殖酸荧光峰发生蓝移.冻融作用导致HPO-A和HPI的荧光性降低.与HPO-A和HPI相比,TPI-A的荧光性受冻融作用的影响相对较小.此外,在4类荧光物质中,冻融作用对DOM组分中的类富里酸荧光物质和类腐殖酸荧光物质的影响较显著.     

巯基化膨润土对As~(3+)的吸附解吸性能研究

水体及土壤砷污染已引起社会的广泛关注。本研究从7种改性膨润土中筛选出1种对As3+吸附能力较强的材料,即巯基化膨润土。其对As3+的吸附解吸研究显示,吸附在120min后达到平衡;在材料投加量达到0.1 g后,As3+的吸附率基本不变;巯基化膨润土对As3+的吸附受p H、温度及离子强度影响较小,其对As3+的解吸受pH及离子强度影响也较小,且解吸率均小于1%。巯基化材料对As3+的饱和吸附量达到了1.18 mg/g,比钙基膨润土提高了12倍以上;其比表面积比钙基膨润土提高了6倍以上。因此,巯基化膨润土是一种较理想的As 3+吸附材料。