贵阳市表层土壤中镉的环境地球化学基线研究

以土壤环境地球化学研究为主线,以贵州省贵阳市8　046　km²为研究区域,将土壤重金属污染元素镉的空间分布规律与环境地球化学机理研究相结合,建立区域土壤环境地球化学基线,选用合适的判别指标判识自然作用过程与人类活动过程对土壤环境的影响.通过对487个样品的镉含量的统计分析,结果表明,贵阳市表层土壤中镉的基线值为0.068　mg/kg,镉元素含量大于1.010　mg/kg的样品可能遭受人为污染的影响.地质累积指数分析结果显示,贵阳市40%的表层土壤未受镉污染,19%的表层土壤在无污染与中度污染之间,14%受中度污染,19%的表层土壤介于中度污染到强污染之间,7%受强污染,1%的表层土壤介于强污染到极强污染之间.污染程度指数分析则显示,贵阳市57.9%的表层土壤未受到镉污染,镉的污染程度最大为12.1,96%的表层土壤污染程度小于4,总污染程度大于0,即总体受到污染.     

Oxidative stress and DNA damages induced by cadmium accumulation

Experimental evidence shows that cadmium （Cd） could induce oxidative stress and then causes DNA damage in animal cells, however, whether such effect exists in plants is still unclear. In the present study, Vicia faba plants was exposed to 5 and 10 mg/L Cd for 4 d to investigate the distribution of Cd in plant, the metal effects on the cell lipids, antioxidative enzymes and DNA damages in leaves. Cd induced an increase in Cd concentrations in plants. An enhanced level of lipid peroxidation in leaves and an enhanced concentration of H2O2 in root tissues suggested that Cd caused oxidative stress in Vicia faba. Compared with control, Cd-induced enhancement in superoxide dismutase activity was significant at 5 mg/L than at 10 mg/kg in leaves, by contrast, catalase and peroxidaseactivities were significantly suppressed by Cd addition. DNA damage was detected by neutral/neutral, alkaline/neutral and alkaline/alkaline Comet assay. Increased levels of DNA damages induced by Cd occurred with reference to oxidative stress in leaves, therefore, oxidative stress induced by Cd accumulation in plants contributed to DNA damages and was possibly an important mechanism of Cd-phytotoxicity in Vicia faba plants.     

Organic matter and concentrated nitrogen removal by shortcut nitrification and denitrification from mature municipal landfill leachate

An UASB＋Anoxic/Oxic （A/O） system was introduced to treat a mature landfill leachate with low carbon-to-nitrogen ratio and high ammonia concentration. To make the best use of the biodegradable COD in the leaehate, the denitrifieation of NOx^--N in the reeireulation effluent from the elarifier was carried out in the UASB. The results showed that most biodegradable organic matters were removed by the denitrifieation in the UASB. The NH4^＋-N loading rate （ALR） of A/O reactor and operational temperature was 0.28- 0.60 kg NH4^＋-N/（m^3-d） and 17-29℃ during experimental period, respectively. The short-cut nitrification with nitrite accumulation efficiency of 90%-99% was stabilized during the whole experiment. The NH4^＋-N removal efficiency varied between 90% and 100%. When ALR was less than 0.45 kg NH4^＋-N/（m^3.d）, the NH4^＋-N removal efficiency was more than 98%. With the influent NH4^＋-N of 1200-1800 mg/L, the effluent NH4^＋-N was less than 15 mg/L. The shortcut nitrification and denitrifieation can save 40% carbon source, with a highly efficient denitrifieation taking place in the UASB. When the ratio of the feed COD to feed NH4^＋-N was only 2-3, the total inorganic nitrogen （TIN） removal efficiency attained 67%-80%. Besides, the sludge samples from A/O reactor were analyzed using FISH. The FISH analysis revealed that ammonia oxidation bacteria （AOB） accounted for 4% of the total eubaeterial population, whereas nitrite oxidation bacteria （NOB） accounted only for 0.2% of the total eubaeterial population.     

Bioaccumulation of heavy metals in fishes from Taihu Lake, China

The Cr,Zn,Cu,Cd,Pb contents were determined in Cyprinus carpio Linnaeus,Carassius auratus Linnaeus,Hypophthalmichthys molitrix and Aristichthys nobilis,which were caught from Meiliang Bay,Taihu Lake,a large,shallow and eutrophic lake of China.The results showed that:(1)the Cr,Cu,Pb,Cd contents in the edible parts of the four fish species were much lower than Chinese Food Health Criterion(1994),but the Zn contents were higher than the Criterion;(2)Cd contents were the highest in the liver of fish,Pb contents were almost the same in all organs of fish,Cr contents mainly enriched in the skin and gonads,Zn contents were the highest in the gonad(♀),and Cu contents were the highest in the liver;(3)the total metal accumulation was the greatest in the liver and the lowest in the muscle.The total metal accumulation was the highest in C.auratus L.This investigation indicated that fish products in Taihu Lake were still safe for human consumption,but the amount consumed should be controlled under the Chinese Food Health Criterion to avoid excessive intake of Zn.     

Thermodynamics and kinetics of cadmium adsorption onto oxidized granular activated carbon

Cadmium sorption behavior of granular activated carbon oxidized with nitric acid was systematically studied by sets of the equilibrium and time-based experiments under various conditions.The cadmium adsorption capacity of oxidized granular activated carbon enlarged with an increase in pH,and reduced with an increase in ionic strength.Experimental data were evaluated to find out kinetic characteristics.Adsorption processes were found to follow pseudo-second order rate equation.Adsorption isotherms correlate well with the Langmuir isotherm model and the maximum sorption capacity of cadmium evaluated is 51.02μmol/g.Thermodynamic parameters were calculated based on Van't Hoff equation.Equilibrium constant Kd was evaluated from Freundlich isotherm model constants,Langmnir isotherm model constants,and isotherms,respectively.The average change of standard adsorption heatΔH~0 was -25.29 kJ/mol.NegativeΔH~0 andΔG~0 values indicate the adsorption process for cadmium onto the studied activated carbon is exothermic and spontaneous.The standard entropyΔS~0 was also negative,which suggests a decrease in the freedom of the system.     

金鱼藻对14CO2的吸收和积累动态

为了探明14CO2(14C)在环境中的行为,采用同位素示踪技术研究了金鱼藻对14CO2的吸收和积累动态,并探讨了金鱼藻作为监测大气14CO2污染指示植物的可能性.结果表明,生长在水中的金鱼藻会通过某些途径吸收空气中14CO2并形成积累趋势,吸收途径主要是金鱼藻通过光合作用从水体中吸收游离14CO2和H14CO3-.金鱼...     

镉对长江华溪蟹金属硫蛋白mRNA表达的诱导及低分子量壳聚糖的联合作用

采用实时荧光定量PCR法,研究了不同浓度镉（Cd2＋）对长江华溪蟹（Sinopotamon yangtsekiense）金属硫蛋白（metallothionein,简称MT）在肝胰腺、鳃、肌肉和心脏中mRNA表达的诱导作用及低分子量壳聚糖（lowmolecular weight chitosan,简称LMWC）的联合作...     

水蚯蚓对硝化细菌活性影响的试验研究

采用SBR反应器富集培养富含硝化细菌的活性污泥,利用填料挂载的方法向SBR反应器投加水蚯蚓,考察了水蚯蚓对SBR反应器硝化效率及硝化细菌活性的影响.结果表明,SBR反应器挂载水蚯蚓后,SBR系统的硝化速率降低了16.65%,NO2--N氧化率减少量约为24%.通过对SBR系统单一周期各形态氮素浓度变化规律进行考察,发现...     

Historical trends of heavy metal contamination and their sources in lacustrine sediment from Xijiu Lake, Taihu Lake Catchment, China

Concentrations of Cd, Cr, Cu, Pb, Zn and Hg in Xijiu Lake sediment from the Taihu Lake catchment, China, were analyzed. Their contamination state was investigated based on the geoaccumulation index and enrichment factors. Statistical analysis was used to differentiate the anthropogenic versus natural sources of heavy metals (HMs), and the anthropogenic accumulation fluxes were calculated to quantify anthropogenic contribution to HMs. The results indicated that the lake sediment had been heavily contaminated by Cd, enrichment of Zn and Hg was at a relatively high level, while that of Cu and Pb was in the lower-to-moderate level and Cr was in the low enrichment level. Sources of Cr in the sediment were mainly from natural inputs, while other metals, especially Cd, were predominantly derived from anthropogenic sources. In the past century, anthropogenic accumulation fluxes of Pb, Zn and Hg increased by 0.1-47.3 mg/(cm².yr), 2.4-398.1 mg/(cm².yr), and 3.7-110.3 ng/(m².yr), respectively, accounting for most inputs of HMs entering the sediment. The contamination state of HMs varied with industrial development of the catchment, which demonstrated that contamination started in the early 20th century, reached the maximal level between the mid-1970s and mid-1990s, and decreased a little after the implementation of constraints on high contamination industries, although the contamination of some HMs, such as Cd, Zn and Hg, is still at high levels.     

三种植物对南京秦淮河重金属污染的监测

调查了南京外秦淮河小行站至汉中门附近7个不同采样点的三种植物-沉水植物空心莲子草(Alternanthera philoxeroides)及沿岸植物酸模(Rumex acetosa L)和石龙芮(Ranunculus sceleratus L)共64个样品中Zn、Fe、Mn、Cu、Ti及Al等金属含量.结果表明,调查的...