Toxicity assessment of contaminated soils from an antitank firing range

Explosives are released into the environment at production and processing facilities, as well as through field use. These compounds may be toxic at relatively low concentrations to a number of ecological receptors. A toxicity assessment was carried out on soils from an explosive-contaminated site at a Canadian Forces Area Training Center. Toxicity studies on soil organisms using endpoints such as microbial processes (potential nitrification activity, dehydrogenase activity, substrate-induced respiration, basal respiration), plant seedling and growth (Lactuca sativa and Hordeum vulgare), and earthworm (Eisenia andrei) growth and reproduction were carried out. Results showed that 1,3,5,7-tetranitro-1,3,5,7-tetrazacyclooctane (HMX) was the principal polynitro-organic compound measured in soils. Soils from the contaminated site decreased microbial processes and earthworm reproduction; whereas plant growth was not significantly reduced. Toxicity to aquatic organisms and genotoxicity were also assessed on soil elutriates using Microtox (Vibrio fischeri), growth inhibition of algae (Selenastrum capricornutum), and SOS Chromotest (Escherichia coli). Results indicated that soil elutriates were generally not toxic to bacteria (Microtox) and algae. However, genotoxicity was found in a number of soil elutriate samples. Thus, the explosive-contaminated soils from the antitank firing range may represent a hazard for the soil organisms. Nevertheless, the global toxicity might have partially resulted from HMX as well as from other (not identified) contaminants such as heavy metals.     

Soil DNA libraries for anticancer drug discovery

Soil has the largest population of microbes of any habitat, but only about 0.3% of soil microbes are cultivable with current techniques. Cultured soil microbes have been an incredibly productive source of drugs, for example the cancer chemotherapeutics doxorubicin hydrochloride, bleomycin, daunorubicin and mitomycin. Unfortunately, the current yield of new drugs from soil microbes is low due to repeated cultivation of the same small fraction of cultivable microbes. Uncultured soil species represent a tremendous untapped resource of new antineoplastic agents. Methods have recently been developed to access the diversity of secondary metabolites from uncultured soil microbes. Briefly, total DNA is extracted from soil samples, purified, partially digested, and fragments inserted into vectors for expression in readily fermented microbes such as Escherichia coli. Clones expressing enzymatic and antibiotic activities that are encoded by novel sequences have been reported.     

Heavy metals in soil, vegetables and fruits in the endemic upper gastrointestinal cancer region of Turkey

The environmental exposure to heavy metals is a well-known risk factor for cancer. We investigated levels of seven different heavy metals, (Co, Cd, Pb, Zn, Mn, Ni and Cu) in soil, fruit and vegetable samples of Van region in Eastern Turkey where upper gastrointestinal (GI) cancers are endemic. Heavy metal contents of the samples were determined by flame atomic absorption spectrometer. Four heavy metals (Cd, Pb, Cu and Co) were present in 2- to 50-fold higher concentrations whereas zinc levels were present in 40-fold lower concentrations in soil. The fruit and vegetable samples were found to contain 3.5- to 340-fold higher amounts of the six heavy metals (Co, Cd, Pb, Mn, Ni and Cu) tested. The volcanic soil, fruit and vegetable samples contain potentially carcinogenic heavy metals in such a high levels that these elements could be related to the high prevalence of upper GI cancer rates in Van region.     

Influences of Quinclorac on Culturable Microorganisms and Soil Respiration in Flooded Paddy Soil

Objective To investigate the potential effects of herbicide quinclorac (3,7-dichloro-8-quinolinecarboxylic) on the culturable microorganisms in flooded paddy soil. Methods Total soil aerobic bacteria, actinomycetes and fungi were counted by a 10-fold serial dilution plate technique. Numbers of anaerobic fermentative bacteria (AFB), denitrifying bacteria (DNB) and hydrogen-producing acetogenic bacteria (HPAB) were numerated by three-tube anaerobic most-probable-number (MPN) methods with anaerobic liquid ertrichment media. The number of methanogenic bacteria (MB) and nitrogen-fixing bacteria (NFB) was determined by the rolling tube method in triplicate. Soil respiration was monitored by a 102G-type gas chromatography with a stainless steel column filled with GDX-104 and a thermal conductivity detector. Results Quinclorac concentration was an important factor affecting the populations of various culturable microorganisms. There were some significant differences in the aerobic heterotrophic bacteria. AFB an     

Mobility,bioavailability, and toxic effects of cadmium in soil samples

Total concentration is not a reliable indicator of metal mobility or bioavailability in soils. The physicochemical form determines the behavior of metals in soils and hence the toxicity toward terrestrial biota. The main objectives of this study were the application and comparison of three approaches for the evaluation of cadmium behavior in soil samples. The mobility and bioavailability of cadmium in five selected soil samples were evaluated using equilibrium speciation (Windermere humic aqueous model (WHAM)), extraction procedures (Milli-Q water, DMSO, and DTPA), and a number of bioassays (Microtox, growth inhibition test, contact toxicity test, and respiration). The mobility, represented by the water-extractable fraction, corresponded well with the amount of cadmium in the soil solution, calculated using the WHAM (r(2)=0.96, P<0.001). The results of the ecotoxicological evaluation, which represent the bioavailable fraction of cadmium, correlated well with DTPA extractability and also with the concentration of free cadmium ion, which is recognized as the most bioavailable metal form. The results of the WHAM as well as the results of extraction experiments showed a strong binding of cadmium to organic matter and a weak sorption of cadmium to clay minerals.     

Aspects of the biomonitoring studies using mosses and lichens as indicators of metal pollution

It has been shown that mosses and lichens, in spite of all disadvantages, are good tools for air pollution monitoring, but best results could be achieved while using both of them together, because of differences in their metal uptake and retention. The researcher dealing with biomonitoring faces many difficulties; for example, in the use of lichens, those of similar composition are not easy to find, because of the differences caused by the tree on which the lichens are growing. Also, terrestrial moss is not always a good choice because of variations in its composition caused by the area it is growing on. The "bag" technique seems to be suitable in many cases because it gives the possibility of comparing wet and dry deposition and there are no differences in its content at the beginning of research. The bag construction should be made to keep the humidity of the sample stable to avoid its drying. For a complete and informative data set the biomonitor content should be compared with precipitation, particulate matter fractionation, and speciation data and also with medical statistics to evaluate the correlation between the amount of pollutants in the atmosphere and the human reaction to them.     

HCH distribution and microbial parameters after liming of a heavily contaminated soil in Rio de Janeiro

The closing down of a lindane factory near Rio de Janeiro, over 45 years ago, left an area heavily contaminated with hexachlorocyclohexane (HCH). Remediation by soil liming was applied by government authorities in 1995. This study aims to evaluate the HCH distribution and impact on soil microbiota due to contamination and liming. Microcosm experiments with uncontaminated soil mixed with HCH and lime indicated that lime-promoted dechlorination of HCH molecules led to leaching and volatilization of metabolites. The treatment applied transformed but did not solve the problem as most of the HCH remains in the soil. Reduced microbial respiratory activity was measured in contaminated field samples. Higher respiration rates in uncontaminated soil were reduced by HCH and lime addition; the sole addition of HCH caused a temporary increase in soil respiration, and stimulation occurred with oxygen and/or nutrient addition. A heterotrophic bacterial population around 10(9)CFU/g was found in polluted field soil, some well-known degraders having been isolated. Native soil microbiota showed resistance to high amounts of HCH and alkaline pH. The results allow considering bioremediation rather than chemical treatments to clean up the area.     

山东省部分地区土壤、作物中汞含量及背景水平

1975～1983年对山东青岛、烟台、临沂、昌滩地区农业土壤及作物中汞的含量做了分析研究,并确定了其背景值,为评价农业土壤中有害物质的含量及作物中汞污染对人体健康的影响以及制定土壤及作物中有害物质的卫生标准提供依据。     

Soil <Emphasis Type="Italic">Pseudomonas</Emphasis> Community Structure and Its Antagonism Towards <Emphasis Type="Italic">Rhizoctonia solani</Emphasis> Under the Stress of Acetochlor

In a microcosm experiment, the amplified ribosomal DNA restriction analysis was adopted to investigate the Pseudomonas community structure in soils applied with different concentrations (0, 50, 150, and 250 mg/kg) of acetochlor, and an in vitro assay was made to examine the antagonistic activity of isolated Pseudomonas strains acting on soil-borne pathogen Rhizoctonia solani. The results showed that acetochlor application changed the community structure of Pseudomonas in aquic brown soil. The diversity of Pseudomonas and the amount of isolated Pseudomonas strains with antagonistic activity decreased with an increasing acetochlor concentration, and the toxic effect of acetochlor reached to a steady level at 150–250 mg/kg.     

复合土钉在医院门诊楼工程中的应用

针对土钉支护对基坑变形的调节和控制能力较差，不适于对变形控制较严格的深基坑工程问题，论述了采用微型桩加土钉支护的复合土钉支护方式实施工程建设的策略及方法，并通过现场监测数据对比分析验证了其科学性和实用性。