运动对2,3,7,8-四氯二苯并二噁英持续暴露大鼠肝脏氧化应激的影响

为探索运动对2,3,7,8-四氯二苯并二噁英(2,3,7,8-TCDD)持续暴露大鼠肝脏氧化应激的影响,本研究将7周龄雄性SD大鼠适应性喂养1周后,随机分为对照(NC)、运动对照(EC)、染毒1(NT1)、运动染毒1(ET1)、染毒2(NT2)、运动染毒2(ET2)、染毒3(NT3)、运动染毒3(ET3)、染毒4(NT4)及运动染毒4(ET4)共10组。染毒组(NTs、ETs)腹腔注射TCDD(溶于玉米油),对照组及各染毒组首次剂量依次为0、0.4、1.6、6.4、25.6μg·kg~(-1)(以单位体重计),之后每周给予上述剂量的21%作为维持剂量,持续染毒8周;运动组尾部负重5%游泳,每周5 d,每次30 min。实验结束取材,测定血清丙氨酸氨基转移酶(ALT)、天冬氨酸氨基转移酶(AST)、肝组织超氧化物歧化酶(SOD)、过氧化氢酶(CAT)、谷胱甘肽过氧化物酶(GSH-Px)活性及丙二醛(MDA)、活性氧(ROS)含量。结果显示:1)染毒可升高各染毒组大鼠血清AST活性及NT4组大鼠血清ALT活性,增加NT2、NT3组肝脏MDA含量,而降低NT1、NT2组大鼠血清ALT活性;2)运动可升高大鼠血清AST及ALT活性,增加大鼠肝组织GSH-Px活性;3)运动可升高染毒大鼠血清AST活性(T1剂量),降低染毒大鼠血清ALT活性(T1剂量),降低染毒大鼠血清AST活性(T3剂量),升高染毒大鼠血清ALT活性(T3、T4剂量),增加染毒大鼠肝组织SOD活性(T2、T3剂量)、CAT活性(T1、T2、T3剂量)及GSH-Px活性(T2、T3、T4剂量),降低染毒大鼠肝组织MDA含量(T2、T3、T4剂量)及ROS含量(T1、T3剂量)。结果表明,2,3,7,8-TCDD持续暴露8周可引起大鼠肝细胞氧化应激损伤,并产生剂量依赖效应;而有氧运动可增加2,3,7,8-TCDD持续暴露(T2、T3剂量)大鼠肝组织抗氧化酶活性,有效降低氧化应激损伤而减轻肝毒性。     

硫酸盐在偶氮染料厌氧生物脱色中的作用

以沼泽红假单胞菌W1为研究对象,考察了厌氧条件下硫酸盐还原对活性黑5(Reactive Black 5,RB5)和直接黄11(Direct Yellow 11,DY11)生物脱色的影响。结果表明,硫酸盐本身对2种染料脱色无明显影响,而硫酸盐的还原产物———硫化物能通过氧化还原介体使2种染料化学脱色,其脱色过程能在3 min内迅速完成。在无介体加入的情况下,硫化物能够通过RB5自身产生的介体加速RB5的脱色;而对于不能产生氧化还原介体的DY11,硫化物对其脱色无明显影响。硫化物经染料氧化后形成的硫单质能够被菌株W1重新转化为硫化物,继续还原染料。     

The rate of soil reduction as affected by levels of methyl parathion and 2, 4‐D

Abstract

A simple technique was demonstrated for determining the potential for synthetic organics to stress microbial populations. Oxidized Crowley and Cecil soil materials were amended with varying concentrations of 2,4‐D and methyl parathion, flooded, and then analyzed for changes in pH, redox potential, and levels of soluble plus exchangeable Fe, Mn, and Zn, all of which may be directly or indirectly influenced by the activity of soil microorganisms. At the concentrations tested (up to 75 ppm), there was little effect of 2,4‐D, but methyl parathion apparently did affect microbial activity contributing to changes in the measured soil properties upon flooding. This approach may be a useful technique for screening various compounds for their potential to stress microbial activity that, for many researchers, would be easier than direct observations of microbial parameters such as population numbers and classifications, and enzyme levels.     

土壤砷污染及修复技术

综述了土壤中砷污染的主要来源,探讨了土壤砷污染的不同修复技术研究现状及特点,并分析了土壤砷污染未来研究需强化的几个方面。     

GROUNDWATER GEOCHEMISTRY IN THE SEMINOLE WELL FIELD,CEDAR RAPIDS,IOWA1

The City of Cedar Rapids obtains its municipal water supply from four well fields in an alluvial aquifer along the Cedar River in east-central Iowa. Since 1992, the City and the U.S. Geological Survey have cooperatively studied the groundwater-flow system and water chemistry near the well fields. The geochemistry in the alluvial aquifer near the Seminole Well Field was assessed to identify potentially reactive minerals and possible chemical reactions that produce observed changes in water chemistry. Calcite, dolomite, ferrihydrite, quartz, rhodochrosite, and siderite were identified as potentially reactive minerals by calculating saturation indexes. Aluminosiicate minerals including albite, Ca-montmorillonite, gibbsite, illite, K-feldspar, and kaolinite were identified as potentially reactive minerals using hypothetical saturation indexes calculated with an assumed dissolved aluminum concentration of 1 microgram per liter. Balanced chemical equations derived from inverse-modeling techniques were used to assess chemical reactions as precipitation percolates to the water table. Calcite dissolution was predominate, but aluminosilicate weathering, cation exchange, and redox reactions also likely occurred. Microbial-catalyzed redox reactions altered the chemical composition of water infiltrating from the Cedar River into the alluvial aquifer by consuming dissolved oxygen, reducing nitrate, and increasing dissolved iron and manganese concentrations. Nitrate reduction only occurred in relatively shallow (3 to 7 meters below land surface) groundwater near the Cedar River and did not occur in water infiltrating to deeper zones of the alluvial aquifer.     

环境条件变化对土壤中稀土元素溶解释放的影响

以模拟污染红壤为实验材料,在pH值为3.5、5.5和7.5条件下,通过向土壤悬浊液中通入O2或N2改变氧化还原电位Eh为－100,0和400mV,研究了氧化还原电位和pH值对红壤中稀土元素La和Ce溶解释放的影响．结果表明,随着pH值或Eh的减小,La和Ce释放量逐渐增大,Ce受电位的影响较La更为明显．同时还观察到La和Ce的释放量与Fe、Mn的释放量呈显著正相关,表明La和Ce可能主要吸附在Fe－Mn氧化物表面或滞留在Fe－Mn氧化物中．实验还发现,pH值和氧化还原电位的改变会影响红壤中La和Ce形态的变化,分离后沉淀物中的交换态和Fe－Mn氧化物结合态稀土随pH值或氧化还原电位的减小而减小．多元相关逐步回归分析表明．红壤中La和Ce两种元素的释放主要来自交换态和Pe－Mn氧化物结合态．     

萘厌氧降解菌群的富集及氧化还原介体的强化

为揭示氧化还原介体（ROMs）对萘厌氧降解的强化作用,以萘为唯一碳源富集到中温萘厌氧降解菌群.通过Illumina MiSeq测序对接种污泥和富集培养物进行了细菌群落结构解析,并考察了固定化蒽醌-2,6-二磺酸（AQDS）、蒽醌-2-磺酸（AQS）和腐殖酸强化萘厌氧降解的特征.Illumina MiSeq测序结果表明,Pseudomonas、Thauera、和Georgfuchsia是该富集培养物中的优势萘降解菌,其相对丰度分别为52.4%、13.8%和17.6%.在污泥接种量为0.23g/L和萘初始浓度10mg/L条件下,富集菌群9d内对萘的降解率约为64%.ROMs强化试验结果表明,3种ROMs对萘的厌氧降解均有一定的促进作用.其中,AQDS的强化效果最为显著,当AQDS浓度为0.8mmol/L,培养至第7d时,萘的去除率为92.0%,比同期的对照组高1.2倍.此外,硝酸盐对ROMs强化萘厌氧降解的影响研究结果表明,在NaNO₃浓度为0~0.8g/L范围内,萘的降解速率随着硝酸盐浓度增加呈现先增加后降低的趋势.当NaNO₃浓度为0.6g/L时,萘的去除率在第6d就达到了91.0%,比对照组提高了15.2%.由此可见,在厌氧条件下添加适量硝酸盐可提高ROMs对萘降解的强化效果.     

Conflicting processes in the wetland plant rhizosphere: Metal retention or mobilization?

Increasingly wetlands are used for treatment of metal-contaminated water or as a cover over metal-enriched mine tailings. Natural wetlands may also be contaminated with metals from anthropogenic sources. While wetland conditions tend to be favorable for immobilization of metals, wetland plants could influence metal mobility through redox and pH processes in the rhizosphere. Our current knowledge of these processes is reviewed, focusing on the question of whether the advantages of growing wetland plants in metal-contaminated sediments outweigh the disadvantages. Wetland plants alter the redox conditions, pH and organic matter content of sediments and so affect the chemical speciation and mobility of metals. Metals may be mobilized or immobilized, depending on the actual combination of factors, and it is extremely difficult to predict which effects plants will actually have on metal mobility under a given set of conditions. However, while the effects of plants can extend several tens of centimeters into the sediments, there are no reports suggesting large-scale mobilization of metals by wetland plants.     

Regulation of soil enzyme activities in constructed wetlands under a short-term drying period

The activities of extracellular enzymes are important in understanding decomposition of soil organic matter in wetlands subjecting to drying. The activity of soil extracellular enzymes (β-glucosidase, N-acetylglucosaminidase, and phosphatase), and related physicochemical parameters were monitored in constructed freshwater wetlands during a one-month drying manipulation. Drying increased redox potential and decreased soil water content significantly (P<0.05). Higher content of soil organic matter (P<0.05) and higher concentrations of inorganic N (nitrate, P<0.01; and ammonia, P<0.001) were also observed significantly under drying condition. Soil hydrolase enzyme activities were stimulated significantly (β-glucosidase, P<0.05; N-acetylglucosaminidase, P<0.01; and phosphatase, P<0.001), and a two-phase pattern of enzyme activities was revealed under drying condition. The increase of soil enzyme activities under drying condition was significantly related to soil redox potential (P<0.001). Drying strongly affected soil enzyme activities only when soil water content remained above an optimal level for enzymatic catalysis (higher than 23% w/w), corresponding to redox potentials below 250–300 mV. Our results suggest that, under drying condition, potential enzyme activities may be regulated by redox potential, in respect to soil moisture, and consequently alter nutrient availability in wetlands.     

BTEX污染含水层不同形态铁含量变化的试验模拟

通过砂柱试验模拟BTEX(苯、甲苯、乙苯和二甲苯的混合物)污染含水层的过程,分析了含水层中铁形态分布及氧化还原环境的变化.结果表明:发生铁还原反应区域介质中的w(TFe)降幅最大,达25.7%;而发生硫酸盐还原反应的区域介质中的w(TFe)因亚铁沉淀生成作用降幅减至11.7%~14.6%.铁还原菌电子受体主要来源于氧化物结合态铁;氧化物结合态铁首先转化为可交换态铁,进而被利用.硫化物结合态铁的形成可作为硫酸盐还原过程开始的标志.