Research on the Toxic Effects of Polyacrylamide and Cadmium on Plants During Soil Utilization of Municipal Sludge

This research aimed to examine the compound effects of polyacrylamide (PAM) and cadmium (Cd) on plant growth subsequent to the mixing of municipal sludge with soil and to explore the potential ecological risks associated with the use of sludge. A pot experiment was performed wherein four gradients (0, 5, 15, and 20 g/[kg dry sludge]) were established corresponding to different PAM concentrations to assess the effects on the physiological and biochemical parameters of Brassica campestris L. ssp. chinensis Makino and Brassica campestris L. and the effects on Cd and PAM concentrations in soil. The findings indicated that the biomass of both plants increased when the total PAM concentration ranged from 5 g to 15 g/(kg dry sludge). Concurrently, polyacrylamide (PAM) downplayed the uptake of Cd by the plants, reduced phytotoxicity, and increased the activities of antioxidant enzymes such as superoxide dismutase (SOD) and peroxidase (POD) in the roots. However, the biomass of Brassica campestris L. ssp. chinensis Makino and Brassica campestris L. decreased significantly when the total PAM concentration was exceeded 15 g/(kg dry sludge), and the toxic effect of Cd on pants was enhanced to some extent. Especially when the PAM concentration was 20 g/(kg dry sludge), apparent cell damage was observed in root cells. It was further noted that Brassica campestris L. portrayed a higher tolerance towards higher proportions of sludge compared with Brassica campestris L. ssp. chinensis Makino. Sludge holds a wider scale of applicability in landscaping than in agriculture. A fusion of polyacrylamide (PAM) and antioxidant enzymes could potentially counteract the effects of Cd within a specific concentration range, serving as a defense mechanism against stress. The data obtained from this study are crucial for unraveling anti-stress responses and detoxification mechanisms employed by different plant species under the influence of factors such as PAM, Cd, and others, thus providing novel insights into research related to land use involving sludges.