Differences in the accumulation of pentachloronitrobenzene and cadmium in vegetables grown in contaminated soils

The capability of different vegetable species to accumulate Pentachloronitrobenzene (PCNB) and cadmium (Cd) in soils varies significantly. Investigating these characteristics can guide the rational use of farmland contaminated with PCNB and Cd. The growth of five common vegetables (three vegetable species and three varieties of one species) in PCNB and Cd co-contaminated soils in Southwest China was investigated through a 100-day simulated contamination pot experiment. Interspecific and intervariety differences in the uptake and accumulation of PCNB and Cd were also examined. These vegetables included leafy types such as Lactuca sativa (CL), Lactuca sativa var. longifolia (RL), and Brassica rapa subsp. chinensis (BC), and root types such as Red Raphanus sativus (RR) and Lactuca sativa var. angustata (AL). Results showed that light to medium PCNB contamination (0.44-6.74 mg kg^-1) promoted the growth of leafy vegetables, while severe contamination (9.88-9.96 mg kg^-1) inhibited their growth. Root vegetables were inhibited by PCNB. Soil Cd contamination reduced the biomass of all five vegetables. In co-contamination soil (PCNB: 0.47-9.88 mg kg^-1; Cd: 0.46-1.63 mg kg^-1), vegetable growth was affected by the interaction between PCNB and Cd. In severely PCNB-contaminated soil, PCNB contents of CL, RL, BC, and AL leaves exceeded food safety limits, while those in RR and AL stems did not. The five vegetables showed varying Cd contamination, with AL leaves being the most contaminated, exceeding the standard by 60 times. PCNB accumulation followed the order: AL leaves > BC > AL stems > RL > CL > RR. Cd accumulation was highest in AL leaves, followed by stems, RR, BC, CL, and lowest in RL, with significant differences (P < 0.05). Co-contaminated soil did not promote PCNB and Cd uptake in vegetables. CL and RL, with low PCNB and Cd accumulation capacities, could be considered low-accumulation varieties for lightly contaminated soils.