Degradation of Triclosan and Carbamazepine in Two Agricultural and Garden Soils with Different Textures Amended with Composted Sewage Sludge

Composted sewage sludge (CSS) has been extensively used in agriculture and landscaping, offering a practical solution for waste disposal. However, some pharmaceutical and personal care products (PPCPs) like triclosan (TCS) and carbamazepine (CBZ) have restricted its land application. In this study, CSS was added to agricultural soil and garden soil at 0%, 5%, 10%, and 25% (w/w soil), and 4 mL of TCS and CBZ stock solution (1000 mg/L in methanol) was spiked into soil amended with CSS of each bottle to arrive at the concentration of 10 mg/kg. Samples were then collected after incubation for 120 days and analyzed for concentrations and half-life (t(1/2)) of TCS and CBZ, and soil physicochemical properties, together with enzyme activities. The results showed that TCS was degraded completely during the incubation period. In contrast, only about 5.82-21.43% CBZ was degraded. CSS amendment inhibited TCS and CBZ degradation and prolonged t(1/2) compared to the control, and the t(1/2) of TCS and CBZ increased with CSS addition amount in all treatments except for CBZ in the garden soil amended with 10% CSS. Correlation studies showed a significantly positive relationship between t(1/2) of TCS and CBZ and total organic carbon (TOC), while a significantly negative relationship between t(1/2) of the two PPCPs and pH was observed. Alkaline phosphatase showed a significantly negative relationship with the C-t/C-0 of TCS in garden soil amended with 25% CSS and CBZ in the control. The urease activity was negatively correlated with the C-t/C-0 of TCS in 10% and 25% CSS treatments and CBZ in 10% CSS treatment for garden soil.