Changes In Organic Matter Content Research Articles

Effects of Soil Organic Matter Content on Cadmium Toxicity in Eisenia Fetida: Implications for the Use of Biomarkers and Standard Toxicity Tests

Bioavailability is affected by soil physicochemical characteristics such as pH and organic matter (OM) content. In addition, OM constitutes the energy source of Eisenia fetida, a well established model species for soil toxicity assessment. The present work aimed at assessing the effects of changes in OM content on the toxicity of Cd in E. fetida through the measurement of neutral red uptake (NRU) and mortality, growth, and reproduction (Organisation for Economic Co-operation and Development [OECD] Nos. 207 and 222). Complementarily, metallothionein (MT) and catalase transcription levels were measured. To decrease variability inherent to natural soils, artificial soils (Organization for Economic Cooperation and Development 1984) with different OM content (6, 10, and 14%) and spiked with Cd solutions at increasing concentrations were used. Low OM in soil decreased soil ingestion and Cd bioaccumulation but also increased Cd toxicity causing lower NRU of coelomocytes, 100 % mortality, and stronger reproduction impairment, probably due to the lack of energy to maintain protection mechanisms (production of MT).Cd bioaccumulation did not reflect toxicity, and OM played a pivotal role in Cd toxicity. Thus, OM content should be taken into account when using E. fetida in in vivo exposures for soil health assessment.

Soil cultivation for enhanced wastewater infiltration in soil aquifer treatment (SAT)

Summary Soil aquifer treatment is often employed as a tertiary treatment component of reclamation proceeding of wastewater for irrigation in agriculture. Reductions in infiltration rates due to increase in water repellency have been reported to be associated with organic matter (OM) accumulation in the soil (mainly in the top soil layer) as a result of treated wastewater (TWW) infiltration. Our aim was to reduce OM content in soils extensively loaded with TWW. Four model infiltration ponds were built to simulate large infiltration basins: three for TWW infiltration using different application regimes, and the fourth for freshwater (FW) infiltration (control). We examined changes in OM content, hydraulic conductivity (HC) and water repellency in these model ponds as a result of soil plowing. In field experiment, four soil-plowing events were performed. Reduced OM content and water repellency, and increased HC were found in all TWW-applied ponds following each soil plowing. These changes were attributed to OM burial in deeper soil layers elimination of the continuity of the OM based crust, and surface exposure of soil with low OM content. An overall reduction in OM content was found at the end of the experiment in all soil layers as a consequence of plowing. No changes in OM content, water repellency or HC were found in the FW-applied pond as a result of soil plowing.