Degradation of nonylphenol in spiked soils and in soils treated with organic waste products

Widespread application of sewage sludge to agricultural soils in Denmark has led to concern about the accumulation and effects of nonylphenol (NP) in the soil ecosystem. We have thus studied the degradation of NP and possible uptake in agricultural plants in greenhouse pot experiments. Different waste products including anaerobic and aerobic sludge, compost, and pig manure were incorporated into a sandy soil. In addition, NP was used to spike soil to known concentrations. Rape (Brassica napus L. cv Hyola 401) was sown in the pots and harvested after 30 d. In order to investigate the influence of plant growth on the degradation, plant-free pots were established. The concentrations in the soil were between 13 and 534 ppb dry weight. No plant uptake was observed above the detection limit at 100 ppb dry weight. When NP was added as waste to the soil, plant growth significantly stimulated the degradation. In experiments with anaerobic and aerobic sludge, respectively, 13 and 8.3% of NP remained in the soil from pots planted with rape compared with 26 and 18% in soil without plant growth. When NP was added as a spike to soil, the degradation was more complete and plant growth did not influence the degradation. Percentages of 2.2 and 1.8 were still in the soil at harvest for planted and plant-free pots, respectively. The degradation of NP was more extensive in sludge-amended soil compared with compost.