Accumulation and Chemical Forms of Cadmium in Tissues of Different Vegetable Crops

Abstract

Large areas of arable lands in China have been contaminated by heavy metals, in which cadmium (Cd) contamination was the most prevalent. Cd accumulation in main food crops and leafy vegetables grown in Cd-contaminated fields has aroused considerable attention in recent years. The present study investigated the Cd pollution of farmland soils and vegetables in Qujing city of Yunnan Province, China. By comparing the Cd uptake capacities of different crops, this study aimed to provide guidance for agricultural production in Cd-contaminated farmland, and clarify the influence of Cd bioavailability in soil and chemical forms of Cd in plant roots on its migration. Results showed that soil Cd concentration was up to 37 mg kg−1, which was 61-fold higher than the soil environmental quality standard in China. Concentration of Cd in 73% of the investigated vegetable samples, with the mean value of 5.43 mg Cd kg−1 (dry weight basis), exceeded the food safety standard of China. Leafy vegetables had the highest bioaccumulation factors (BF) and transfer factors (TF), with the mean values of 0.53 and 0.41, respectively. Water spinach (Ipomoea aquatica Forsk.), cole (Brassica campestris L.), and fennel (Foeniculum dulce Mill.) had the highest Cd TFs, with averages of 0.67, 0.66, and 0.64, respectively. On the contrary, garlic (Allium sativum L.), onions (Allium fistulosum L.), and pea (Lathyrus odoratus L.) had the lowest Cd TFs, with averages of 0.04, 0.03, and 0.04, respectively. The main chemical fraction of Cd in garlic root was insoluble phosphate (35%–48%), whereas in water spinach root, it was pectate, protein binding or sorbed fraction (50%–64%), resulting in a higher TF value of water spinach than garlic. These results indicate that there were significant differences in Cd uptake and accumulation between vegetables, and the Cd accumulation in leafy vegetable was significantly higher than that in alliums. Therefore, it is possible to reduce the uptake and accumulation of Cd in crop edible parts by the selection of vegetable species with low Cd accumulation capacity. The chemical fractions of Cd in crop roots, especially the proportions of more mobile fractions, might be an important reason for the root-to-shoot Cd transport and Cd accumulation in the aerial portions.

Health Risk and Quality Assessment of Vegetables Cultivated on Soils from a Heavily Polluted Old Mining Area

“…The present study showed that the leafy vegetable lettuce had higher a Cd enrichment capacity than root vegetables. Some previous studies showed that leafy vegetables were more likely to accumulate Cd than non-leafy vegetables [36], which is consistent with the results of the present study. The BAF was also affected by the bioavailability of elements in soil and their interactions.…”

Enrichment, Bioaccumulation and Health Risks of Trace Metals in Soils and Leafy Vegetables Grown on the Banks of the Ugandan Lifeline River, River Rwizi

“…Taken together, the level of bioaccumulation of the TMTs followed the order Cd > Zn > Cu > Pb > Mn > Cr. Hyperaccumulation of Cd in leafy vegetables has been reported previously in leafy vegetables such as B. oleracea [59], Brassica campestris L., Brassica chinensis L. and Brassica juncea L. [60].…”

Transfer of heavy metals from soil to vegetables: A comparative assessment of different irrigation water sources

“…The study reported that the TF of elements from soil to plants differs, with the TF for Cd being greater than that of Cr and Pb [ 57 ]. Xiao et al [ 58 ] also found that the TF of Cd from root to leaf is higher than from root to stem [ 58 ].…”