Will spent mushroom substrate application affect the dissipation and plant uptake of phthalate esters?

PURPOSE: The objective of this study was to investigate whether spent mushroom substrate (SMS) amendment was an appropriate way to reduce di(2-ehylhexyl) phthalate (DEHP) and di-n-butyl phthalate (DnBP) contents in soil and whether SMS could reduce DnBP accumulation in bok choy (Brassica rapa subsp. chinensis). MATERIALS AND METHODS: Microcosm and pot experiments were carried out to study the influence of spent Agaricus bisporus substrate application on DnBP and DEHP dissipation in soils and plant uptake of DnBP. Variations in soil pH and enzyme activities were determined. The concentrations of phthalate esters (PAEs) in soils, bok choy, and atmosphere were examined with gas chromatography or gas chromatography–mass spectrometry. RESULTS AND DISCUSSION: Adding sterilized or non-sterilized SMS can increase soil pH and urease activity, and non-sterilized SMS can promote soil laccase activity. The results show that the dissipation of DEHP is accelerated after incubation with SMS for 25 days; however, little effect can be found with continuing incubation due to low DEHP bioavailability. In this research, SMS amendment exhibits no effect on DnBP dissipation in soils and DnBP accumulation in bok choy. It was proposed that atmospheric deposition of DnBP might be the main source of DnBP in bok choy in the study, since equivalent amounts of DnBP were detected in the vegetables grown in soils with or without DnBP spiking. CONCLUSIONS: This study indicates that the application of SMS as an organic fertilizer is less likely to affect the fate of PAEs in soils, and proper strategies should be conducted to reduce PAE levels in atmosphere to control PAE contamination in vegetables.