Assessment of the pollution levels of potential toxic elements in urban vegetable gardens in southwest China

Abstract

Vegetable gardens are increasingly common in urban areas and can provide numerous societal benefits; however, contamination with potential toxic elements (PTEs) due to urbanization and industrialization is cause for concern. The present study aimed to assess the source of contamination and pollution levels in urban garden soils, as well as the health risks for adults and children consuming vegetables grown in such environments. Various types of vegetable samples and their corresponding soils from 26 community gardens were collected throughout Chengdu City in southwestern China. The results showed that leafy vegetables, particularly lettuce leaves and Chinese cabbage, had relatively higher levels of Cd (0.04 mg/kg FW) and Pb (0.05 mg/kg FW), while higher levels of As (0.07 mg/kg FW), Cr (0.07 mg/kg FW), and Hg (0.003 mg/kg FW) were found in amaranths, tomatoes, and Houttuynia cordatas, respectively. The pollution indices revealed that the vegetable purplish soils were relatively more polluted by Cd and As, and the concentrations of these metals in vegetables were correlated with their concentrations in the soils. Principal component analysis grouped the PTEs in two dimensions that cumulatively explained 62.3% of their variation, and hierarchical clustering identified two distinct clusters indicating that Cr originated from a unique source. The health risk assessment revealed that exposure to As and Cd induced the greatest non-carcinogenic risk, whereas Cr was most likely to cause cancer risks. Furthermore, contaminated vegetable consumption was riskier for children than adults. The critical factors contributing to PTE contamination in vegetable gardens were determined to be vegetable species, total soil element content, soil pH, and soil organic matter content. Overall, Cr and As pollution present the greatest concern, and community health care services must enact more effective regulatory and preventative measures for urban gardens in terms of PTEs.

Lead exposure dose-dependently affects oxidative stress, AsA-GSH, photosynthesis, and mineral content in pakchoi (Brassica chinensis L.)

“…Pb residues are found in both industrial and residential soils, and are transferred to, and accumulated in plants ( Doris et al., 2021 ; Gao et al., 2021 ). Pb is known to cause chlorosis, oxidative stress, and growth and development disorders in plant leaves ( Kanwal et al., 2020 ).…”

“…Moreover, the Pb content in soils approximately 20 kilometers away from the La Oroya metallurgical complex in Peru was 217.81 ± 39.48 mg/kg, of which 9.5% was transferred to the surrounding grasses (Doris et al, 2021). The Pb content in lettuce leaves and Chinese cabbage grown in urban garden soils reached 0.05 mg/kg fresh weight, and the Pb concentration in these vegetables was positively correlated with the Pb soil levels (Gao et al, 2021;Calabro ́et al, 2022). The over-standard rate of Pb in 673 plant samples provided by a typical intensive production system in Hainan Province is 2.67%, and leafy vegetables are more polluted than non-leafy vegetables (Yang et al, 2021).…”

Lead exposure dose-dependently affects oxidative stress, AsA-GSH system, photosynthesis, and mineral element content in pakchoi (Brassica Chinensis L.)

“…Pb residues were found in both industrial and human living soils, which will be further transferred to plants to accumulate (Doris, Jorge et al, Gao, Zhang et al 2021). A study reported that Pb can cause chlorosis, oxidative stress and growth and development disorders in plant leaves ).…”

“…In urban garden soil planting leafy vegetables, the Pb content in lettuce leaves and Chinese cabbage reached 0.05 mg/kg FW and found that the metal concentration in vegetables was positively correlated with the metal consistence in the soil (Gao, Zhang et al 2021). The over-standard rate of Pb in the 673 plant samples provided by the typical intensive production system in Hainan Province is 2.67%, and leafy vegetables have a higher degree of pollution than non-leaf vegetables (Yang, Wang et al 2021).…”

The impact of chromium ion stress on plant growth, developmental physiology, and molecular regulation

“…Soil contaminated with heavy metals such as chromium further degrade the quality of agricultural crops growing on them and pose a potential threat to human food security. Previous research has suggested that excessive chromium levels severely affected crops of sweet potatoes ( Ipomoeabatatas ) (Gao et al, 2021 ) and wheat ( Triticum aestivum ) (Wang et al, 2017 ), and studies on heavy metals have revealed that the threat of chromium contaminated soil is imminent ( Figure 1 ).…”