Interspecific variation of accumulation in vegetables under the PCNB and Cd combined contaminated soil

Objective Different vegetable varieties exhibit significant differences in their accumulation capacities when grown in environments contaminated by pentachloronitrobenzene (PCNB) and cadmium (Cd). To explore this phenomenon and provide a basis for the rational use of contaminated farmland, this study selected several common vegetables and analyzed their growth responses and pollutant accumulation capacities in PCNB-Cd contaminated environments.

Method Through pot experiments, the growth status of Lactuca sativa, Lactuca sativa var. longifolia, Brassica rapa subsp. chinensis, Raphanus sativus, and Lactuca sativa var. angustata under combined PCNB and Cd contamination was investigated. The study also examined the absorption and accumulation performance of these vegetables in response to the pollutants.

Result The light and medium soil PCNB polluting (0.44～6.74 mg·kg⁻¹) promoted the growth of leafy vegetables, but severe soil PCNB (9.88～9.96 mg·kg⁻¹) contamination inhibited the growth of leafy vegetables. Root vegetables were inhibited by PCNB at all levels of contamination in this study. The soil Cd polluting level of 0.35～1.96 mg·kg⁻¹ reduced the biomass of all five vegetables. Co-contamination with PCNB and Cd (PCNB: 0.47～9.88 mg·kg⁻¹; Cd: 0.46～1.63 mg·kg⁻¹) inhibited the effects of PCNB and Cd on vegetable growth. On the severe PCNB contaminated soil, PCNB contents in the edible parts of Lactuca sativa）、Lactuca sativa var. longifolia、Brassica rapa subsp. chinensis and Lactuca sativa var. angustata leaves exceeded the food safety critical value, while those of Red Raphanus sativus and Lactuca sativa var. angustata stem did not exceed the standard. The five test vegetables were contaminated with different degrees of on the Cd contaminated soil, among which Lactuca sativa var. angustata leaves were the most seriously contaminated, with the highest Cd content exceeding the standard by 60 times, followed by Lactuca sativa var. angustata stems and Red Raphanus sativus. The ability of vegetables to accumulate PCNB was Lactuca sativa var. angustata leaves ＞ Brassica rapa subsp. chinensis ＞ Lactuca sativa var. angustata stems ＞ Lactuca sativa var. longifolia ＞ Lactuca sativa ＞ Red Raphanus sativus. The accumulation capacity for Cd was highest in Lactuca sativa var. angustata leaves, followed by Lactuca sativa var. angustata stems, Red Raphanus sativus, Brassica rapa subsp. chinensis, Lactuca sativa, and lowest in Lactuca sativa var. longifolia, with significant differences (P＜0.05, n=5).

Conclusion The combined pollution of PCNB and Cd does not significantly promote the absorption of PCNB and Cd by vegetables. In summary, Lactuca sativa and Lactuca sativa var. longifolia have lower accumulation capacities for PCNB and Cd, making them suitable for cultivation in soils with mild PCNB-Cd contamination. The results of this study provide theoretical support for optimizing and adjusting the vegetable planting structure in the Chengdu Plain