Monitoring microbial biomass and respiration in different soils from the Czech Republic--a summary of results

The microbial biomass (Cbio), respiration (basal respiration (BR) and potential respiration (PR)), and derived indices for 520 independent soil samples of 117 different soils from the Czech Republic were statistically analysed. The broad range of soil samples allowed the stepwise breakdown of the database into six reasonable categories of soil: arable soils, loamy grassland soils, sandy grassland soils with weak organic matter content, sandy grassland soils with moderate organic matter content, forest soils with moderate organic matter content, and forest organic soils with rich organic matter content. Because soil microbiology lacks benchmarking values, the ranges of the microbial characteristics for these categories were stated and are presented here. The separation into soil groups narrowed the ranges enough to be useful for comparative purposes. The groups displayed significant differences in basal microbial parameters. The lowest microbial biomass was found in arable soils and grassland sandy soils with weak organic matter content. The highest microbial biomass was shown by loamy grassland soils and organic forest soils. Respiration displayed similar results to the microbial biomass. The derived indices revealed less significant differences confirming their inner-standard nature. The relationships between the soil contamination and microbial parameters were not explored because of the confounding effect of soil organic matter. However, it was not shown by the category of grassland sandy soils with weak organic matter content suggesting they could be especially suitable for the biomonitoring of harmful effects of chemicals on soil microorganisms.     

Novel approach to monitoring of the soil biological quality

In this study, a new approach to interpretation of results of the simple microbial biomass and respiration measurements in the soil microbiology is proposed. The principle is based on eight basal and derived microbial parameters, which are standardized and then plotted into sunray plots. The output is visual presentation of one plot for each soil, which makes possible the relative comparison and evaluation of soils in the monitored set. Problems of soil microbiology, such as the lack of benchmarking and reference values, can be avoided by using the proposed method. We found that eight parameters provide enough information for evaluation of the status of the soil microorganisms and, thus, for evaluation of the soil biological quality. The usage of rare parameters (potential respiration PR, ratio of potential and basal respiration PR/BR, biomass-specific potential respiration PR/C(bio), available organic carbon C(ext), and biomass-specific available organic carbon C(ext)/C(bio)) can be recommended, besides classical and well-known parameters (microbial biomass C(bio), basal respiration BR, metabolic coefficient qCO(2)). The combination of basal parameters and derived coefficients can also extend our knowledge about the condition of the soil microorganisms. In monitoring the case studies presented, we observed that soils evaluated to possess good biological quality displayed generally higher values of organic carbon, total nitrogen, clay, and cation exchange capacity. The soils of good biological quality can display higher levels of contaminants. This is probably related with the higher content of organic carbon and clay in these soils.     

Ecophysiological indicators of microbial biomass status in chernozem soils of the Central Caucasus (in the territory of Kabardino-Balkaria with the Terek variant of altitudinal zonation)

A comparative assessment of the biological properties of chernozem soils in agro- and biogeocenoses has been made by determining the rates of basal and substrate-induced soil respiration and using these data to calculate ecophysiological indices characterizing the potential and stability of soil microbial biomass. The results show that the rate of CO₂ emission and the contents of microbial biomass carbon in agriculturally exploited chernozem soils have decreased by factors of 3 and 2.6, respectively. The values of microbial metabolic quotients are indicative of medium-to-strong disturbance to the stability of microbial communities in chernozem soils of agrocenoses.     

Effect of indigenous bacterial activity on arsenic mobilization under anaerobic conditions

Batch biochemical leaching tests were carried out to investigate the mobility of arsenic from a contaminated soil collected from a French gold mining site. The specific objective of this research was to examine the effect of indigenous bacterial activity on arsenic mobilization under anaerobic conditions. In a first step, physical and chemical characterizations were performed to provide data concerning the liquid-solid partitioning and mobility of arsenic and other inorganic constituents. In a second step, batch bioleaching tests were conducted in shaker flasks to determine the effect of indigenous bacterial activity under different anaerobic conditions (i.e., addition of mineral nutrients and carbon sources) on arsenic mobilization. Results indicated that arsenic release during contact with deionized water was limited by its very low solubility in the interstitial solution and by the stability of the different arsenic compounds formed with the amorphous solid phases of the soil (mainly iron (oxy)hydroxides). However, an increased mobilization potential was observed over the long term under anaerobic conditions with indigenous bacterial activity enhanced by the addition of carbon sources.     

Secondary arsenic minerals in the environment: A review

Information on arsenic (As) speciation in solid materials is critical for many environmental studies concerned with As stability and/or mobility in natural As-impacted soils and mining or industrial sites contaminated by As. The investigation of these systems has provided evidence for a number of secondary As minerals that have often played a significant role in As mobility in the solid phase–water system. This paper presents a list of environmentally important secondary As minerals in contaminated soil and waste systems, summarizes the information about their origin, occurrence, environmental stability and thermodynamics, and proposes several important avenues for further investigation.     

Mitigation of arsenic contamination in irrigated paddy soils in South and South-east Asia

It has recently become apparent that arsenic-contaminated groundwater used for irrigation in several countries of South and South-east Asia is adding arsenic to soils and rice, thus posing a serious threat to sustainable agricultural production and to the health and livelihoods of affected people in those countries. This paper describes the many environmental, agricultural and social factors that determine practical mitigation strategies and research needs, and describes possible mitigation measures that need to be tested. These measures include providing alternative irrigation sources, various agronomic measures, use of soil amendments, growing hyperaccumulator plants, removing contaminated soil and using alternative cooking methods.     

Enhanced transfer of arsenic to grain for Bangladesh grown rice compared to US and EU

A field survey was conducted in arsenic impacted and non-impacted paddies of Bangladesh to assess how arsenic levels in rice (Oryza sativa L.) grain are related to soil and shoot concentrations. Ten field sites from an arsenic contaminated tubewell irrigation region (Faridpur) were compared to 10 field sites from a non-affected region (Gazipur). Analysis of the overall data set found that both grain and shoot total arsenic concentrations were highly correlated (P<0.001) with soil arsenic. Median arsenic concentrations varied by 14, 10 and 3 fold for soil, shoot and grain respectively comparing the two regions. The reason for the sharp decline in the magnitude of difference between Gazipur and Faridpur for grain arsenic was due to an exponential decline in the grain/shoot arsenic concentration ratio with increasing shoot arsenic concentration. When the Bangladesh data were compared to EU and US soil-shoot-grain transfers, the same generic pattern could be found with the exception that arsenic was more efficiently transferred to grain from soil/shoot in the Bangladesh grown plants. This may reflect climatic or cultivar differences.     

邹城东滩矿区复垦土壤微生物量碳与#br# 基础呼吸的特征

探究复垦土壤微生物量碳与基础呼吸的特征及其演变归因，有助于监测复垦土壤质量演变，并为提高复垦土壤质量提供科学依据。利用“空间代替时间”的方法研究了邹城东滩矿区复垦土壤微生物量碳（MBC）与基础呼吸（SBR）随复垦年垦的变化及其与土壤环境因子的关系。结果表明：复垦土壤MBC和微生物熵（qSMBC）随复垦年限呈增加趋势；复垦土壤SBR均显著高于对照，土壤代谢熵（qCO2）随复垦年限趋于降低，复垦后土壤微生物量逐渐恢复，同时土壤微生物对碳源利用效率逐渐提高，说明土壤环境逐渐有利于土壤微生物的生长。土壤MBC与碱解氮、总氮和有机碳呈极显著正相关（p＜0.01），反映土壤养分缺乏是复垦后土壤微生物生长的主要限制因素。土壤代谢熵（qCO2）与土壤碱解氮、速效磷和MBC均呈极显著负相关（p＜0.01）与pH呈显著正相关（p＜0.05），说明氮磷等元素的缺乏以及较高的土壤pH环境是限制微生物生长的重要因素。这些对全面监测复垦后土壤质量的演变，并指导今后的复垦工作具有重要理论与实践意义。 关键词： 采煤塌陷区；土壤微生物量碳；土壤微生物熵；基础呼吸     

苏南水稻土有机碳矿化特征及其与活性有机碳组分的关系

通过对江苏省常熟市全市范围代表性水稻土采样并布置室内短期（20 d）培育实验，研究土壤有机碳矿化过程动态，并分析其与微生物生物量碳和水溶性有机碳含量的关系。结果表明：研究区域水稻土有机碳含量变化为488～2731 g/kg，平均为1807 g/kg，全氮含量变化为058～284 g/kg，平均为186 g/kg；微生物生物量碳、氮及水溶性有机碳含量分别为2940～1 2874，1854～8178和701～2879 mg/kg，且不同土属间存在显著差异（〖WTBX〗p〖WTBZ〗＜005）；土壤呼吸强度为3476～19168 mgCO2/（kg·d），平均为7993 mgCO2/（kg·d），不同土属间高低顺序为乌栅土＞乌黄泥土＞灰黄泥土＞白土＞黄泥土＞乌沙土；培养期内有机碳日均矿化量为1076～6520 mgCO2/kg，平均为4046 mgCO2/kg，有机碳累计矿化量为21525～1 30213 mgCO2/kg，平均为80720 mgCO2/kg，不同土属间有机碳日均矿化量和累计矿化量变化趋势为乌栅土＞乌黄泥土＞乌沙土＞白土＞灰黄泥土＞黄泥土；研究区域水稻土有机碳矿化率为307%～758%，但不同土属间差异不显著（p＞005）。统计结果表明，土壤有机碳呼吸强度和日均矿化量与微生物生物量碳及水溶性有机碳之间均呈显著正线性关系，相关系数分别为0686、0594、0826、0749。〖     

Risk assessment and pathway study of arsenic in industrially contaminated sites of Hyderabad: a case study

Different areas in the industrial region of Patancheru near Hyderabad, Andhra Pradesh (A.P), India are contaminated with high concentration of arsenic, which is attributed to industrial source like veterinary chemicals, pharmaceuticals, pesticide industries, etc. Fourteen villages of this area of Patancheru were assessed for arsenic contamination by collecting samples of water (surface and ground), soil, fodder, milk, and vegetables. The total arsenic content in the whole blood, urine, hair, and nails of the residents showing arsenical skin lesions and other clinical manifestations were also studied. To understand the bioavailability of arsenic in this environment and its possible entry into human food chain, speciation studies of arsenic was carried out and the results are presented in this paper.     

Effect of soil properties on arsenic fractionation and bioaccessibility in cattle and sheep dipping vat sites

Historical use of high arsenic (As) concentrations in cattle/sheep dipping vat sites to treat ticks has resulted in severe contamination of soil and groundwater with this Group-A human carcinogen. In the absence of a universally applicable soil As bioaccessibility model, baseline risk assessment studies have traditionally used the extremely conservative estimate of 100% soil As bioaccessibility. Several in-vitro, as well as, in-vivo animal studies suggest that As bioaccessibility in soil can be lower than that in water. Arsenic in soils exists in several geochemical forms with varying degree of dissolution in the human digestive system, and thus, with highly varying As bioaccessibility. Earlier batch incubation studies with As-spiked soils have shown that As bioaccessibility is a function of soil physicochemical properties. We selected 12 dipping vat soils collected from USA and Australia to test the hypothesis that soil properties exert a significant effect on As bioaccessibility in As-contaminated sites. The 12 soils varied widely in terms of soil physico-chemical properties. They were subject to an As sequential fractionation scheme and two in-vitro tests (IVGS and IVGIA) to simulate soil As bioavailability in the human gastrointestinal system. Sequential As fractionation results showed that the majority of the As measured in the dipping vat soils resided either in the Fe/Al hydroxide fraction, or the Ca/Mg fractions, or in the residual fraction. Water-extractable As fraction of the 12 soils was typically <10% of the total, reaching values up to 23%, indicating minimal leaching potential, and hence, lower risk of As-contamination from exposure to groundwater, typically used as drinking water in many parts of the world. Partial individual correlations and subsequent multiple regression analyses suggested that the most significant soil factors influencing As bioaccessibility were total Ca+Mg, total P, clay content and EC. Collectively, these soil properties were able to explain 85 and 86% of the variability associated with the prediction of bioaccessible As, using IVGS and IVGIA in-vitro tests, respectively. This study showed that specific soil properties influenced the magnitude of soil As bioaccessibility, which was typically much lower than total soil-As concentrations, challenging the traditional risk assessment guideline, which assumes that soil As is 100% bioaccessible. Our study showed that total soil As concentration is unlikely to provide an accurate estimate of human health risk from exposure to dipping vat site soils.     

Availability and immobilization of 137Cs in subtropical high mountain forest and grassland soils

To understand the behavior of (137)Cs in undisturbed soils after nuclear fallout deposition between the 1940s and 1980s, we investigated the speciation of (137)Cs in soils in forest and its adjacent grassland from a volcano and subalpine area in Taiwan. We performed sequential extraction of (137)Cs (i.e., fractions readily exchangeable, bound to microbial biomass, bound to Fe-Mn oxides, bound to organic matter, persistently bound and residual). For both the forest and grassland soils, (137)Cs was mainly present in the persistently bound (31-41%) and residual (22-62%) fractions. The proportions of (137)Cs labile fractions--bound to exchangeable sites, microbial biomass, Mn-Fe oxides, and organic matter--were lower than those of the recalcitrant fractions. The labile fractions in the forest soils were also higher than those in the grassland soils, especially in the volcanic soil. The results suggest that the labile form of (137)Cs was mostly transferred to the persistently bound and resistant fractions after long-term deposition of fallout. The readily exchangeable (137)Cs fraction was higher in soils with higher organic matter content or minor amounts of 2:1 silicate clay minerals.     

Effect of heavy metals and PAH on soil assessed via dehydrogenase assay

Dehydrogenase enzyme activity (DHA) assay method using resazurin was accommodated for measuring of toxicity of compound contaminants on uncharacterized microbial communities present in any given soil. The method was used to compare the toxic effect of heavy metal and polycyclic aromatic hydrocarbon (PAH) contaminant mixture (Cr, Pb, Cu, Cd, Pyrene) on four typical Estonian soils covering a range of compositions. The method proved to be useable on all soils; the sensitivity of soil microbiology to toxic effect of contaminants was found to have a negative correlation with Ca and organic matter (OM) content and a positive correlation with amorphous phase content of soils.     

The effect of pollutants (heavy metals and diesel fuel) on the respiratory activity of constructozems (artificial soils)

Young (1 month old) and mature (2 years old) constructozems (artificial soils) were supplemented with individual heavy metal salts or diesel fuel at different concentrations. The polluted and control constructozem variants were incubated and sampled at different time points to determine microbial biomass carbon (C_mic) and microbial respiration (MR). These parameters were found to be almost twice higher in the young than in the mature constructozem, with all pollutants causing an increase in C_mic, MR, and MR/C_mic = qCO₂ values. The pollutant type had an effect on MR and qCO₂ variances, and the time of exposure, on C_mic. The qCO₂ value showed a strong positive correlation with pollutant concentrations, allowing this parameter to be regarded as a suitable indicator of urban environmental pollution.     

Photosynthesis and growth responses of giant reed (Arundo donax L.) to the heavy metals Cd and Ni

Giant reed (Arundo donax L.) was grown on surface soil and irrigated with mixed heavy metal solutions of Cd(II) and Ni(II) to study the impact of these heavy metals on its growth and photosynthesis. The tested concentrations were 5, 50, and 100 ppm for each heavy metal against the control and resulted in high cadmium and nickel (DTPA extractable) concentrations in the top zone of the pot soil. The examined parameters, namely, stem height and diameter, number of nodes, fresh and dry weight of leaves, and net photosynthesis (Pn) were not affected, indicating that plants tolerate the high concentrations of Cd and Ni. As giant reed plants are very promising energy plants, they can be cultivated in contaminated soils to provide biomass for energy production purposes.     

Soil respiration of forest ecosystems in gradients of environmental pollution by emissions from copper smelters

The effect of industrial pollution on soil respiration measured in situ has been studied along two gradients formed by emissions from large copper smelters: the Middle Ural Copper Smelter (spruce-fir forests) and Karabash Copper Smelter (birch forests). Pollution has proved to have a slight effect on soil respiration: its rate drops only in the zone of industrial barren. There is no correlation between soil respiration and distance to the emission source, metal contents in the litter, or litter acidity. A hypothesis is proposed that this may be due to a shift in the ratio of the root and microbial components of respiration in the pollution gradient.     

Effect of Earthworm（Pheretima sp.） Density on Revegetation of Lead/zinc Metal Mine Tailings Amended with Soil

The objective of this study was to investigate the effects of earthworm density on the availability of nutrients and heavy metals in metal contaminated soils. Pb/Zn mine tailings were mixed throughly with a red yellow podzolic soil at the ratio （w/w） of 75：25. Earthworms （Pheretima sp.） were introduced to the mixture at four different densities, zero, three, six and nine individuals per pot planted with ryegrass （Loliun multiflorum）. The results indicated that earthworm activity significantly enhanced ryegrass shoot biomass. However, as denser earthworm population was introduced, shoot biomass tended to decrease. Earthworm activity significantly increased soil pH and availability of N, P and K in the tailings and soil mixture. There was a general tendency that uptake of Zn by ryegrass increased after earthworm inoculation, although the increase in extractable Zn in tailings and soil mixture was not significant. On the contrary, there seemed to be a lower uptake of Pb by ryegrass under earthworm inoclation, despite the fact that higher extractable Pb concentrations were observed. The present project indicated that the improved growth of ryegrass was due to improved nutrient availability and other soil conditions, by inoculation of earthworms at an appropriate rate. Further studies are needed to illustrate the relationship between metal availability and earthworm activity in the field.     

Radiocesium storage in soil microbial biomass of undisturbed alpine meadow soils and its relation to 137Cs soil-plant transfer

This study focuses on radiocesium storage in soil microbial biomass of undisturbed alpine meadow sites and its relation to the soil-to-plant transfer. Soil and plant samples were taken in August 1999 from an altitude transect (800-1600m.a.s.l.) at Gastein valley, Austria. Soil samples were subdivided into 3-cm layers for analyses of total, K(2)SO(4)-extractable and microbially stored (137)Cs. Microbial biomass was measured by the fumigation extraction method, and fungal biomass was quantified using ergosterol as biomarker molecule. In general, the quantity of (137)Cs stored in the living soil microbial biomass was relatively small. At the high-altitude meadows, showing high amounts of fungal biomass, microbially stored (137)Cs amounted to 0.64+/-0.14kBqm(-2) which corresponds to about 1.2-2.7% of the total (137)Cs soil inventory. At lower altitudes, microbial (137)Cs content was distinctly smaller and in most cases not measurable at all using the fumigation extraction method. However, a positive correlation between the observed soil-to-plant aggregated transfer factor, microbially stored (137)Cs and fungal biomass was found, which indicates a possible role of fungal biomass in the storage and turnover of (137)Cs in soils and in the (137)Cs uptake by plants.     

Phytoextraction for clean-up of low-level uranium contaminated soil evaluated

Spills in the nuclear fuel cycle have led to soil contamination with uranium. In case of small contamination just above release levels, low-cost yet sufficiently efficient remedial measures are recommended. This study was executed to test if low-level U contaminated sandy soil from a nuclear fuel processing site could be phytoextracted in order to attain the required release limits. Two soils were tested: a control soil (317 Bq 238U kg(-1)) and the same soil washed with bicarbonate (69 Bq 238U kg(-1)). Ryegrass (Lolium perenne cv. Melvina) and Indian mustard (Brassica juncea cv. Vitasso) were used as test plants. The annual removal of soil activity by the biomass was less than 0.1%. The addition of citric acid (25 mmol kg(-1)) 1 week before the harvest increased U uptake up to 500-fold. With a ryegrass and mustard yield of 15,000 and 10,000 kg ha(-1), respectively, up to 3.5% and 4.6% of the soil activity could be removed annually by the biomass. With a desired activity reduction level of 1.5 and 5 for the bicarbonate-washed and control soil, respectively, it would take 10-50 years to attain the release limit. However, citric acid addition resulted in a decreased dry weight production.     

Screening plant species native to Taiwan for remediation of 137Cs-contaminated soil and the effects of K addition and soil amendment on the transfer of 137Cs from soil to plants

This study aims to screen plant species native to Taiwan that could be used to eliminate (137)Cs radionuclides from contaminated soil. Four kinds of vegetables and two kinds of plants known as green manures were used for the screening. The test plants were cultivated in (137)Cs-contaminated soil and amended soil which is a mixture of the contaminated one with a horticultural soil. The plant with the highest (137)Cs transfer factor was used for further examination on the effects of K addition on the transfer of (137)Cs from the soils to the plant. Experimental results revealed that plants cultivated in the amended soil produced more biomass than those in the contaminated soil. Rape exhibited the highest production of aboveground parts, and had the highest (137)Cs transfer factor among all the tested plants. The transfer of (137)Cs to the rape grown in the soil to which 100 ppm KCl commonly used in local fertilizers had been added, were restrained. Results of this study indicated that rape, a popular green manure in Taiwan, could remedy (137)Cs-contaminated soil.