Effects of ethylenediaminetetraacetic acid-assisted phytoremediation on soil physicochemical and biological properties

Ethylenediaminetetraacetic acid is increasingly used to improve heavy metal mobility and bioavailability in soil for phytoremediation, although little empirical data exist on its potential effects on soil properties essential to phytoremediation success and ecosystem health. In this study, field-based ethylenediaminetetraacetic acid-, nitrogen–phosphorus–potassium fertilizer-, and combination of ethylenediaminetetraacetic acid and nitrogen–phosphorus–potassium fertilizer-assisted phytoremediation were used to determine the effects of ethylenediaminetetraacetic acid on some soil physicochemical and biological parameters. Ethylenediaminetetraacetic acid reduced the levels of pH, organic matter, calcium, potassium, magnesium, total fungi and bacteria and improved microbial carbon and nitrogen as well as nitrate and ammonium contents. However, it had no effect on soil field capacity. In general, ethylenediaminetetraacetic acid had a greater explanatory power for the variations in pH, organic matter and total bacteria relative to the other treatments and time. Nitrogen–phosphorus–potassium fertilizer reduced the effects of ethylenediaminetetraacetic acid on soil pH, organic matter, potassium, phosphorus, microbial carbon and nitrogen. Hence, combination of ethylenediaminetetraacetic acid and nitrogen–phosphorus–potassium fertilizer was the most effective in improving the soil conditions for phytoremediation. The most significant changes in the effects of the treatments on all but nitrogen were observed in the first six months of the study, corresponding with the wet season, suggesting the need to consider the season or timeframe when designing field-based assisted phytoremediation. The results broadly demonstrate the effectiveness of nitrogen–phosphorus–potassium fertilizer in compensating for the potentially negative effects of ethylenediaminetetraacetic acid on soil properties during phytoremediation.