The microplastics distribution characteristics and their impact on soil physicochemical properties and bacterial communities in food legumes farmland in northern China.

Microplastics (MPs) pose a threat to farmland soil quality and crop safety. MPs exist widely in food legumes farmland soil due to the extensive use of agricultural film and organic fertilizer, but their distribution characteristics and their impact on soil environment have not been reported. The abundance and characteristics of MPs, soil physical and chemical properties, and bacterial community composition were investigated in 76 soil samples from five provinces in northern China. The results showed that the abundance of MPs ranged from 1600 to 36,200 items/kg. MPs in soil were mostly fibrous, less than 0.2 mm, and white. Rayon, polyester and polyethylene were the main types of MPs. The influences of MPs on soil physicochemical properties and bacterial communities mainly depended on the type of MPs. Notably, polyethylene significantly decreased the proportion of silt particles, and increased the nitrate nitrogen content as well as the abundance of MPs-degrading bacteria Paenibacillus (p < 0.05). Moreover, bacteria were more sensitive to polyesters in soil with low concentration of organic matter. This study indicated that MPs in food legumes farmland soil presented a higher-level. And, they partially altered soil physicochemical properties, and soil bacteria especially in soil with low organic matter.

Cadmium-induced phytotoxicity and tolerance response in the low-Cd accumulator of Chinese cabbage (Brassica pekinensis L.) seedlings.

In vegetable production, Chinese cabbage can readily accumulate cadmium (Cd) into its edible parts and exceed food safety standards. However, there are still some ecotypes that respond differently to cadmium stress. This study aimed to investigate the differences of Cd-induced (0, 10, 50, 100, 200 µM) response under hydroponic culture between two Chinese cabbage ecotypes which were promoted in northeastern China from the characteristics of biomass, uptake kinetic, accumulation, and initial oxidative stress. In this paper, it was confirmed that Jinfeng (JF) was a Cd-tolerant cultivar and had low Cd accumulation in edible part, while Qiutian (QT) was Cd-sensitive, exhibiting a faster Cd uptake rate but lacking effective Cd detoxication mechanisms, and was severely damaged by 10 µM Cd treatment. Conversely, even at a high Cd concentration of 200 µM, Jinfeng had weaker biomass inhibition, lower root Cd affinity, more difficult root-to-leaf translocation, and stronger antioxidant enzyme activity than Qiutian. In conclusion, Jinfeng can endure mild Cd stress (<10 µM), and Qiutian can be used as a Cd indicator. This study provides reliable materials and related data support for vegetable production in areas with mild Cd pollution.Novelty statement: This work further investigates the unique features of low-Cd accumulator in Chinese cabbage (Brassica pekinensis L.) seedlings as an interesting material for vegetable production in areas with mild Cd pollution. It also explains the differences between Cd-tolerant and Cd-sensitive cultivars under different cadmium stress levels and how these differences can alter their response. With the increase of Cd concentration, Cd-tolerant cultivars compared to Cd-sensitive cultivars showed less biomass decrease, lower accumulation, lower TF, more chemically stable Cd in roots and more active antioxidant enzymes under the same Cd stress level. With the development of seedlings, the uptake of Cd in roots and the translocation to the leaves were effectively restricted by the poor Cd affinity of roots, the conversion of Cd chemical forms and the promotion of antioxidase activities, in a Cd-tolerant low accumulator, Jinfeng.