Effect of sawdust amendment on mineralization of organic nitrogen in a 2,4,5-trichlorophenol contaminated soil

Previous studies have demonstrated that the toxic effects of 2,4,5trichlorophenol (2,4,5-TCP) are greater in agricultural soils than in forest soils; therefore these effects appear to be influenced by the total C content and soil pH. Agricultural soils (usually low in organic C) contaminated with 2,4,5-TCP may be able to be remediated by the addition of organic waste products. To test this hypothesis, an agricultural soil was artificially contaminated with 5000 mg kg-1, 500 times the Generic Reference Level (GRL) of 2,4,5-TCP, then pine sawdust was added to the contaminated soil at doses equivalent to 5% and 10% of the soil weight. The effect of the sawdust on the toxicity of the contaminant was studied by measuring the degree of mineralization of the organic nitrogen in the soil. The addition of 2,4,5-TCP produced a large increase in the amount of inorganic N present (basically ammoniacal forms), which suggests that the 2,4,5-trichlorophenol caused the death of a large part of the edaphic microbiota. The addition of sawdust buffered this effect, particularly at the highest dose (10%) as the degree of mineralization was similar to that observed in the control sample treated with the same amount of sawdust, this indicating that 10% dose of sawdust is capable of mitigating the toxic effects of 2,4,5-TCP.