Accumulation of phthalates under high versus low nitrogen addition in a soil-plant system with sludge organic fertilizers instead of chemical fertilizers

Abstract

Nitrogen is the main nutrient in soil. The long-term addition of N leads to changes in the soil dissolved organic matter (DOM) and other quality indicators, which affects the adsorption and accumulation of organic pollutants. The use of organic fertilizer is important for the development of green agriculture. However, organic fertilizers (especially sludge organic fertilizers (SOFs) contain phthalates (PAEs) that may accumulate in the soil and result in environmental contamination. How this accumulation response varies with the magnitude of long-term N addition, especially in different soil layer profiles, remains unclear. Here, changes in the content of PAEs in the soil–plant system without and after SOFs application were studied through field experiments in soils with different N addition backgrounds (CK, N1, N3 (0, 100, 300 kg N ha−1 yr−1 respectively)). Our results showed that the application of SOFs increase the accumulation of PAEs in soil profiles and plant systems, increasing human health risks. The content of Σ5PAEs in the topsoil increased from 0.96 ± 0.10 to 1.86 ± 0.09 mg kg−1. Moreover, under a high N addition background and SOFs application, the characteristics of soil DOM change, and the accumulation of PAEs in soil was nearly 30% higher compared with the low N group. Some suggestions such as removing PAEs from SOFs during preparation, conducting soil surveys before applying PAEs, and using soil amendments, which are provided for optimizing the trialability and environmental safety of SOFs application.