Limitations of soil microbial biomass carbon as an indicator of soil pollution in the field

The size of the soil microbial biomass carbon (SMBC) has been proposed as a sensitive indicator for measuring the adverse effects of contaminants on the soil microbial community. In this study of Australian agricultural systems, we demonstrated that field variability of SMBC measured using the fumigation-extraction procedure limited its use as a robust ecotoxicological endpoint. The SMBC varied up to 4-fold across control samples collected from a single field site, due to small-scale spatial heterogeneity in the soil physicochemical environment. Power analysis revealed that large numbers of replicates (3-93) were required to identify 20% or 50% decreases in the size of the SMBC of contaminated soil samples relative to their uncontaminated control samples at the 0.05% level of statistical significance. We question the value of the routine measurement of SMBC as an ecotoxicological endpoint at the field scale, and suggest more robust and predictive microbiological indicators.     

Kinetics of Zn and Cd accumulation in the isopod Porcellio scaber exposed to contaminated soil and/or food

To derive accumulation kinetics from different exposure matrices and account for the contribution of different exposure routes, the isopod Porcellio scaber was exposed to Cd and Zn, either in soil or in food, and a combination of both. Accurate uptake and elimination kinetics of Zn and Cd were determined using radioisotopes, allowing non-destructive time measurements. To describe the data, a simple kinetic model was used accounting for the internal distribution of the metals. A strong influence of the elimination kinetics, together with the metal fraction that is compartmentalized in a storage fraction, was found explaining the Cd steady-state level reached in the isopods. Zn turnover kinetics were relatively fast within the first days of exposure and elimination, followed by slow Zn kinetics from the storage compartment. The storage fraction appeared to be inert for elimination of both Zn and Cd within the experimental duration of 32 days and the fraction of metal taken up that was stored in this fraction was influenced by the uptake source. The quantity of metals taken up from soil or food depended on the concentration. For both Zn and Cd, the uptake rate constant from soil equalled the uptake rate constant from food, moreover, the uptake from both routes was shown to be additive. Therefore, it is concluded that the relative contribution of both routes (via soil or food) is explained by the partitioning of metals between soil and food.     

Solubilization of toxic metal minerals and metal tolerance of mycorrhizal fungi

This work investigates the ability of ericoid mycorrhizal (ErM) and ectomycorrhizal (EcM) fungi to solubilize different toxic metal (Cd, Cu, Pb, Zn)-containing minerals. Minerals were incorporated into solidified agar media and solubilization assessed by measuring clearing of the agar after fungal growth. Measurement of radial growth and biomass dry weight provided indications of metal tolerance: accumulated metal in the biomass was measured by atomic absorption spectrophotometry. Metal tolerance and solubilizing ability varied widely between different mineral and fungal species, and strains derived from sites of differing degrees of metal pollution. Zinc phosphate exhibited the least toxicity and was the easiest to solubilize by the majority of tested fungal isolates. Solubilization of toxic metal minerals was connected with both the pH of the medium and growth and tolerance of fungi and it seems that acidification of the medium was the main mechanism of mineral dissolution for most of the mycorrhizal fungi studied. A very strong lethal effect was observed for ectomycorrhizal isolates (>60% of strains) in the presence of Pb phosphate, carbonate, sulphide and tetraoxide. In contrast, ericoid mycorrhizal isolates were able to grow on Pb-mineral-amended media. A significant proportion of ericoid mycorrhizal cultures (70-90%) solubilized Cd and Cu phosphates and cuprite. None of the ericoid mycorrhizal and ectomycorrhizal fungi were able to produce a clear zone in Pb mineral-containing agar. However, many fungi were able to accumulate mobilized Pb in their mycelia. Differences in toxic metal mineral tolerance, mineral solubilization and metal uptake between populations isolated from metal-polluted and uncontaminated sites were related to the toxic metal which was the main pollutant in the original contaminated environment. In general, metal-tolerant fungi grew and solubilized toxic metal minerals better than non-tolerant isolates.     

Assessment of tillage erosion by mouldboard plough in Tuscany (Italy)

This study was designed to characterise the soil translocation effect induced by mouldboard ploughing with an implement traditionally used in the Tuscany region (Central Italy). We discuss the results of a set of field experiments performed to measure soil displacement along slopes of varying gradient in different directions and at several depths of tillage. Using the Soil Erosion by Tillage (SETi) model, soil translocation patterns for different tillage scenarios were analysed, with special attention paid to the effects of the direction and depth of tillage on the extent and spatial pattern of soil movement. The lateral slope gradient S_P and tillage depth D were found to be the dominant controlling factors for total soil displacement. The effect of the slope gradient in a direction parallel to tillage S_T was much less pronounced. These findings reveal the importance of the asymmetric nature of the soil movement produced by mouldboard ploughing and the predominant effect of the lateral displacement d_P on the actual trajectory of soil motion. Results demonstrate that spatial patterns of soil redistribution due to mouldboard ploughing are highly variable and depend on the particular characteristics of the implement used. This dependence is so strong that maximum downslope soil translocation can occur during both, contour tillage or up–down tillage. For this particular mouldboard plough, maximum downslope soil transport took place at a tillage direction ca. 70° and not when tillage was conducted along the steepest slope direction (0°). These findings highlight the potential of the combined approach applied. The physically based SETi model can be properly calibrated using a relatively limited dataset from field experiments. Once calibrating, the SETi model can then be used to generate synthetic tillage translocation relationships, which can predict the intensity and spatial pattern of soil translocation over a much wider range of tillage scenarios than the particular experimental conditions, in terms of topography complexity (slope gradients and morphology) and the direction and depth of tillage. These synthetic relationships are useful tools for evaluating strategies designed to reduce tillage erosion.     

葡萄红色素稳定性的研究

[目的]提高葡萄皮红色素在食品中使用时的稳定性。[方法]以红提葡萄为材料提取葡萄皮红色素,研究温度、VC和金属离子对葡萄皮红色素稳定性的影响。[结果]葡萄皮红色素的最大吸收波长为530 nm,其残存率随温度上升而逐渐降低,18、25、40、60和80℃条件下的残存率分别为81.77%、80.98%、79.41%、78.80%和75.72%。葡萄皮红色素的残存率受食品添加剂VC浓度的影响不显著。葡萄皮红色素的残存率受K+影响较小,受Fe3+影响较大,在Zn2+、Mg2+、Al3+、Cu2+、Ca2+、Fe3+和K+影响下,其残存率分别为85.05%、85.47%、91.30%、88.72%、85.58%、83.23%和93.47%。[结论]葡萄皮红色素不耐高温,VC对其稳定性的影响不显著,K+对其稳定性影响较小,Fe3+、Cu2+对其稳定性影响较大。     

壳聚糖和羧甲基壳聚糖与金属配位的研究进展

壳聚糖对金属离子有良好的配位作用。经化学改性之后,壳聚糖衍生物-羧甲基壳聚糖对金属离子的配位能力进一步增强。该文主要就壳聚糖和羧甲基壳聚糖与不同金属离子的配位机制、配位条件以及配合物的物化性质做一综述。     

金属离子对蒙古口蘑菌体及胞外多糖的影响

研究了5种金属离子Fe2＋、Zn2＋、ca2＋、Cu2＋、Mg2＋对蒙古口蘑的茵体生长及胞外多糖的影响。结果表明,在培养基中添加5种金属离子Fe2＋、zn2＋、ca2＋、Mg2＋和Cu2＋,对茵体的生长都有一定的抑制作用,但却都能提高胞外多糖的产量,促进作用依次为Zn2＋〉Fe2＋〉Ca2＋〉Cu2＋）Mg2＋,最大比对照分别提高了280．3％、160．5％、83．6％、52．6％和19．2％。     

Effect of composting on extractability and relative availability of heavy metals present in Calcutta municipal solid waste

How composting affects heavy metal content is largely unknown. Accordingly, we investigate the total content of six heavy metals, Cd/Zn ratio and the Zn-equiv, the relative availability and fractionation study to assess the suitability of compost derived out of those for environmental concerns. During composting, total metal content increased but their RA decreased. As a result of composting bioavailable form of metals also decreased. High significant correlations between different forms of heavy metals content and degree of humification were found for all the elements. Composting increases humic acid content than fulvic acid. This transformation is mainly responsible to serve as binding agent for metal thereby moderating the rapid metal mobilization.     

再生金属工业园区土壤重金属污染特征及来源分析

[目的]为了揭示土壤中锌、铜、铅、镍的分布状况及污染情况.[方法]以路桥峰江再生金属工业园区域土壤中锌、铜、铅、镍为主要研究对象,通过系统的土壤取样调查,研究园区土壤锌、铜、铅、镍的空间结构和分布规律.[结果]随着与园区距离的增加,土壤铅、锌、铜、镍含量呈显著下降趋势.由于铅、锌、铜、镍都受到工业活动的影响,它们的分布特征几乎一致.这与该区工业类型单一性和工厂布局的聚集性有关,园区西部方向土壤受污染程度要比东部方向重.园区东西方向100 m内土壤铅污染程度较重,是土壤国家二级标准的1.86 ～5.25倍,已不适宜用于农业种植、畜牧等用途.[结论]该研究可以为后续土壤环境质量评价或治理提供参考.     

大麦萌发过程中几种金属离子含量的跟踪监测

金属离子在大麦发芽过程中有两种状态:结合态与游离态。利用空气-乙炔火焰原子吸收光谱法跟踪监测大麦发芽过程中金属离子总含量和游离态含量的变化,结果显示,它们在大麦发芽过程中的变化呈现出很大的不同,总的离子含量一般呈现出单调的变化,而游离态的离子含量随发芽时间的不同呈现出波动变化。由于金属离子不同的存在状态有着不同的生理功能,通过跟踪监测离子2种状态的含量变化,可以为研究金属离子在大麦发芽过程中的生理作用提供新的方法。