Home About us Contact | |||
Low Organic Matter Content (low + organic_matter_content)
Selected AbstractsAvoidance tests in site-specific risk assessment,influence of soil properties on the avoidance response of collembola and earthworms,ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 5 2008Tiago Natal-da-Luz Abstract The ability of organisms to avoid contaminated soils can act as an indicator of toxic potential in a particular soil. Based on the escape response of earthworms and Collembola, avoidance tests with these soil organisms have great potential as early screening tools in site-specific assessment. These tests are becoming more common in soil ecotoxicology, because they are ecologically relevant and have a shorter duration time compared with standardized soil toxicity tests. The avoidance response of soil invertebrates, however, can be influenced by the soil properties (e.g., organic matter content and texture) that affect behavior of the test species in the exposure matrix. Such an influence could mask a possible effect of the contaminant. Therefore, the effects of soil properties on performance of test species in the exposure media should be considered during risk assessment of contaminated soils. Avoidance tests with earthworms (Eisenia andrei) and springtails (Folsomia candida) were performed to identify the influence of both organic matter content and texture on the avoidance response of representative soil organisms. Distinct artificial soils were prepared by modifying quantities of the standard artificial soil components described by the Organization for Economic Co-operation and Development to achieve different organic matter and texture classes. Several combinations of each factor were tested. Results showed that both properties influenced the avoidance response of organisms, which avoided soils with low organic matter content and fine texture. Springtails were less sensitive to changes in these soil constituents compared with earthworms, indicating springtails can be used for site-specific assessments of contaminated soils with a wider range of respective soil properties. [source] Soil metaproteomics: a review of an emerging environmental science.EUROPEAN JOURNAL OF SOIL SCIENCE, Issue 6 2009Significance, methodology, perspectives Summary Soil is a dynamic system in which microorganisms perform important tasks in organic matter transformations and nutrient cycles. Recently, some studies have started to focus on soil metaproteomics as a tool for understanding the function and the role of members of the microbial community. The aim of our work was to provide a review of soil proteomics by looking at the methodologies used in order to illustrate the challenges and gaps in this field, and to provide a broad perspective about the use and meaning of soil metaproteomics. The development of soil metaproteomics is influenced strongly by the extraction methods. Several methods are available but only a few provide an identification of soil proteins, while others extract proteins and are able to separate them by electrophoresis but do not provide an identification. The extraction of humic compounds together with proteins interferes with the latter's separation and identification, although some methods can avoid these chemical interferences. Nevertheless, the major problems regarding protein identification reside in the fact that soil is a poor source of proteins and that there is not enough sequence-database information for the identification of proteins by mass spectrometric analysis. Once these pitfalls have been solved, the identification of soil proteins may provide information about the biogeochemical potential of soils and pollutant degradation and act as an indicator of soil quality, identifying which proteins and microorganisms are affected by a degradation process. The development of soil metaproteomics opens the way to proteomic studies in other complex substrates, such as organic wastes. These studies can be a source of knowledge about the possibility of driven soil restoration in polluted and degraded areas with low organic matter content and even for the identification of enzymes and proteins with a potential biotechnological value. [source] Growth of Frankia strains in leaf litter-amended soil and the rhizosphere of a nonactinorhizal plantFEMS MICROBIOLOGY ECOLOGY, Issue 1 2009Babur S. Mirza Abstract The ability of Frankia strains to grow in the rhizosphere of a nonactinorhizal plant, Betula pendula, in surrounding bulk soil and in soil amended with leaf litter was analyzed 6 weeks after inoculation of pure cultures by in situ hybridization. Growth responses were related to taxonomic position as determined by comparative sequence analysis of nifH gene fragments and of an actinomycetes-specific insertion in Domain III of the 23S rRNA gene. Phylogenetic analyses confirmed the basic classification of Frankia strains by host infection groups, and allowed a further differentiation of Frankia clusters within the Alnus host infection group. Except for Casuarina -infective Frankia strains, all other strains of the Alnus and the Elaeagnus host infection groups displayed growth in the rhizosphere of B. pendula, and none of them grew in the surrounding bulk soil that was characterized by a very low organic matter content. Only a small number of strains that all belonged to a distinct phylogenetic cluster within the Alnus host infection group grew in soil amended with ground leaf litter from B. pendula. These results demonstrate that saprotrophic growth of frankiae is a common trait for most members of the genus, and the supporting factors for growth (i.e. carbon utilization capabilities) varied with the host infection group and the phylogenetic affiliation of the strains. [source] Impact of Dredging on Phosphorus Transport in Agricultural Drainage Ditches of the Atlantic Coastal Plain,JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION, Issue 6 2008Francirose Shigaki Abstract:, Drainage ditches can be a key conduit of phosphorus (P) between agricultural soils of the Atlantic Coastal Plain and local surface waters, including the Chesapeake Bay. This study sought to quantify the effect of a common ditch management practice, sediment dredging, on fate of P in drainage ditches. Sediments from two drainage ditches that had been monitored for seven years and had similar characteristics (flow, P loadings, sediment properties) were sampled (0-5 cm) after one of the ditches had been dredged, which removed fine textured sediments (clay = 41%) with high organic matter content (85 g/kg) and exposed coarse textured sediments (clay = 15%) with low organic matter content (2.2 g/kg). Sediments were subjected to a three-phase experiment (equilibrium, uptake, and release) in recirculating 10-m-long, 0.2-m-wide, and 5-cm-deep flumes to evaluate their role as sources and sinks of P. Under conditions of low initial P concentrations in flume water, sediments from the dredged ditch released 13 times less P to the water than did sediments from the ditch that had not been dredged, equivalent to 24 mg dissolved P. However, the sediments from the dredged ditch removed 19% less P (76 mg) from the flume water when it was spiked with dissolved P to approximate long-term runoff concentrations. Irradiation of sediments to destroy microorganisms revealed that biological processes accounted for up to 30% of P uptake in the coarse textured sediments of the dredged ditch and 18% in the fine textured sediments of the undredged ditch. Results indicate that dredging of coastal plain drainage ditches can potentially impact the P buffering capacity of ditches draining agricultural soils with a high potential for P runoff. [source] |