Microbial activity promotes the enrichment of cobalt over nickel on hydrogenetic ferromanganese crusts     

P. P. Sujith  D. Ramanan  P. A. LokaBharathi 《Marine Georesources & Geotechnology》2017,35(8):1158-1167

The different mineral phases of the ferromanganese (Fe–Mn) crusts stem from the interaction of biotic and abiotic components. It is therefore vital to study the activity of these components to decipher their contribution to the enrichment/depletion of metals in the crust. Thus, the present study examined sorption and release of Co and Ni by Fe-Mn crusts with associated microbial communities in the presence and absence of the metabolic poison sodium azide (15?mM). The study was conducted in the presence (G⁺) and absence (G^?) of added glucose (0.1%) at temperatures of 4?±?1°C and 28?±?2°C. Results showed that the microbial community had maximal sorption of Co of 66.12?µg?g^?1 at 4?±?1°C in the absence of added glucose and 479.75?µg?g^?1 at 28?±?2°C in the presence of added glucose. Maximum sorption of Ni in the absence of added glucose was 1.89?µg?g^?1 at 4?±?1°C and release of Ni was 51.28?µg?g^?1 in the presence of added glucose. Under abiotic conditions with 15?mM sodium azide as a metabolic inhibitor, significant amounts of Co and Ni were released in the G⁺ medium. Total cell counts on the Fe-Mn crust in the presence of added glucose increased by an order of magnitude from 10⁶ to 10⁷ cells g^?1 and in the absence of added glucose remained within the order of 10⁶ cells?g^?1 irrespective of temperature of incubation. Microscopic observation of the samples from biotic incubations showed numerous bacterial cells, exopolysaccharides, and structures resembling secondary minerals formed by bacteria. The results indicate that bacteria promote the enrichment of Co and Ni on the hydrogenetic Fe-Mn crusts by sorption processes and release of Ni by reductive dissolution of the oxides. The higher enrichment of Co than Ni is attributed to the way in which microbes interact with the metals.  相似文献   

Assessment of the impact of pore-scale mass-transfer restrictions on microbially-induced stable-isotope fractionation     

《Advances in water resources》2014

Stable-isotope fractionation has become an established method for the assessment of contaminant biodegradation in groundwater. At the pore scale however, mass-transfer processes can limit the bioavailability of chemical species and therefore affect the observed fractionation. This can challenge the application of stable-isotope analysis in practice. A linear-exchange model provides a computational link between the microbially-induced isotope fractionation, determined under ideal conditions, and the fractionation observed under conditions of limited bioavailability. This simplifying conceptual approach allows for accurately estimating the mass-transfer limited degradation rates but its applicability for stable-isotope fractionation at the pore scale has not been evaluated yet. In this study, we perform high-resolution numerical simulations of microbial degradation and stable-isotope fractionation of a chemical species in a pore-scale model. The numerical results are compared to theoretical predictions derived from the linear-exchange model. Our results show an overall good agreement between numerical simulations and theoretical predictions, which confirms the applicability of the theoretical approach and of the value for the mass-transfer coefficient previously derived from the geometry of the pore space. In addition we provide a quantitative link between the value of the observable fractionation factor and the effective bioavailability of a biodegradable contaminant.  相似文献   

煤岩吸附二氧化碳气体的CT实验研究   总被引：1，自引：0，他引：1  

郝耐  ;毛灵涛  ;魏峰  ;马甲年 《CT理论与应用研究》2014,(3):425-433

利用工业CT技术及应变测量研究不同气压下煤岩的二氧化碳气体吸附性质。研究发现：煤样的应变随吸附时间和气体压力的增加而增加,且在不同方向是不同的,吸附气体导致煤样孔隙率增加;煤样CT图像的灰度均值和灰度标准差随吸附时间和气体压力的增长都表现出增加的趋势。结果表明：吸附二氧化碳导致煤样总体发生膨胀变形,这为吸附提供更多的孔隙表面积而使吸附气体量增加,含气煤样的密度也因此而增大;气体吸附导致的煤样密度均值增加的效应大于体积膨胀导致的煤样密度均值减小的效应;吸附使煤样内部物质分布不均匀程度增加。  相似文献   

UV/Peroxyacetic Acid Mediated Chlorophenol Congener Degradation          下载免费PDF全文

Swati Sharma  Zagabathuni Venkata Panchakshari Murthy 《洁净——土壤、空气、水》2014,42(3):276-283

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Bioaccumulation of cadmium in the ascidian Styela clava (Herdman 1881)     

《African Journal of Marine Science》2013,35(3):289-295

The processes of bioaccumulation and elimination of cadmium by tissues of Styela clava (Herdman 1881) were investigated based on a semi-static two-compartment model. The kinetic parameters (accumulation rate constant k ₁, elimination rate constant k ₂, bioconcentration factor BCF, biological half-life t _1/2 and maximum equilibrium concentration C _Amax) were obtained by non-linear regression. The results showed that S. clava accumulates cadmium from its aquatic environment. BCF decreased with increasing metal concentration in the water, and when the accumulation achieved balance, C _Amax correlated positively with metal concentrations in the water. Concentrations of cadmium in different tissues of S. clava were: gonad > digestive gland ≈ other parts > tunic. The t _1/2 values for cadmium were 15.54-50.40 days in the accumulation process and 11.53-24.55 days in the elimination phase. The high rate of accumulation and elimination of cadmium from the body reveals the potential of the organism to be used as a biomonitor of short-term cadmium fluctuation in marine systems.  相似文献   

Experimental Study of Factors Controlling Sorption of Heavy Metals on Ariake Clay and Implication for Practice     

Y. J. Du  S. Hayashi 《Marine Georesources & Geotechnology》2013,31(2):103-118

A series of batch tests have been presented to investigate the effects of solid-solution contact time, solid:solution ratio, and pH of solution on sorption of Cd²⁺ and Pb²⁺ on Ariake clay from Kyushu region of Japan. The results show that, among the three investigated factors, solid:solution ratio (SD/SN) seems to be the crucial controlling factor. The Freundlich sorption parameters determined from the batch tests were applied to a typical field landfill in which the Ariake clay was used as soil barrier. The impacts of the landfill were assessed by numerical analysis. Based on the analysis result, the significance of selecting proper solid:solution ratio for determining sorption parameters from batch test has been discussed.  相似文献   

Mechanisms and factors affecting the adsorption of sodium alginate onto modified clays     

林勇新  曹西华  宋秀贤  王楠  俞志明 《中国海洋湖沼学报》2013,31(4):867-875

Algal organic materials (AOMs) are one critical factor affecting the efficiency of modified clays used for the mitigation of harmful algal blooms (HABs). This study was conducted to develop a deeper understanding of the mechanisms and factors affecting the adsorption of AOMs onto modified clays. Sodium alginate (polysaccharide) and kaolinite modified with polyaluminium chloride (PACl) were used as AOMs and modified clay model substances, respectively, and the effects of modifier dosage, contact time, solution pH and ionic strength were investigated through batch adsorption experiments. Kinetics revealed that the alginate adsorption rate was described well by a pseudo-second order model. PACl effectively enhanced the adsorption capacity of kaolinite and increased the adsorption rate, and the optimum additive amount of PACl was 5%. The experimental data fitted both the Freundlich and Langmuir adsorption equations well. The adsorption thermodynamics for alginate onto modified clays suggests that alginate adsorption is a spontaneous process. The adsorption of alginate onto modified clays was highly dependent on pH, with a decrease in adsorption observed with increased pH to 9.48, but the opposite was true above pH 9.48. Finally, adsorption increased with increasing ionic strength.  相似文献   

光助Fenton氧化法去除水中两种氯乙酸及其动力学研究     

李先国  周璇  刘金燕  李艳霞 《中国海洋大学学报(自然科学版)》2012,42(3):64-69

以二氯乙酸和三氯乙酸为目标污染物,研究了光助Fenton氧化去除水中卤乙酸的可行性及影响因素,并对其动力学进行了初步研究.结果表明,影响光助Fenton氧化的因素很多,氙灯功率500 W、H2O2和Fe2+投加量分别为5.0和1.0 mmol·L-1、pH=4.0反应60 min是所考察范围内的最佳降解条件,浓度为100 μg·L-1的二氯乙酸和三氯乙酸的降解率分别为90.32％、87.77％;在实际水质pH=7.0时,相同浓度的二氯乙酸和三氯乙酸的降解率分别为75.34％、68.80％.紫外辐射与Fenton氧化对二氯乙酸和三氯乙酸的降解具有协同效应.光助Fenton氧化对二氯乙酸和三氯乙酸的降解符合一级反应动力学,表观活化能分别为30.11、31.09 kJ·mo1-1,受温度影响不大.  相似文献   

粘土矿物的掺杂对沉积物吸持Cu、Zn能力的影响   总被引：3，自引：0，他引：3  

王晓丽  李鱼  王一喆  杜显元  王婷  刘建林 《吉林大学学报(地球科学版)》2010,40(1):183-187

通过考察粘土矿物及掺杂粘土矿物前后沉积物的吸附/解吸特性,分析了伊利石与蒙脱石对重金属污染沉积物中Cu与Zn稳定固定化的可行性。结果表明：伊利石与蒙脱石的掺杂均降低了沉积物吸持Cu的能力（最大下降量分别为5.4%和3.8%）,伊利石的掺杂同样降低了沉积物吸持Zn的能力（最大下降量为4.4%）,但蒙脱石掺杂后沉积物吸持Zn的能力明显增强,最高增加5.7%。因此,蒙脱石具有固定污染沉积物中Zn的能力,但不能提高污染沉积物中Cu的稳定性。  相似文献   

Kinetic Modelling of the Removal of Seven Common Pollutants in Subsurface Flow Constructed Wetlands     

SUN Guangzhi  Antony Ladson 《湿地科学》2010,8(4)

The main removal mechanisms for the degradations of seven pollutants in wastewater treatment wetlands were analysed, and a mathematical model was established to quantify the removal of each pollutant, based on its main removal mechanisms. Subsurface horizontal flow wetlands were treated as a series of continuous stirred - tank reactors (CSTRs). Kinetic models for the removal of biochemical oxygen demand, chemical oxygen demand, ammonia, total nitrogen and faecal coliforms were established by combining Monod or first - order kinetics with CSTR assumptions. These tentative models account for a wide range of factors that affect wetland performance, but the models have not been proven by ex periment data. Depending on the derivation of various coefficients in the models and verification by actual performance data, this study may provide a starting point for an integrated pollutant removal model to be developed, and experimen tally verified, thereby making a step forward from the current greenbox' approach of wetland design.  相似文献