| Heavy metals are the most common pollutants in the soil environment,which are characterized by invisibility,universality and irreversibility,etc.The level-by-level translocation through the “soil-plant/ water-human body” way not only causes existing or potential soil quality degradation,ecological and environmental degradation and other soil pollution phenomena,but also poses certain hazards to the growth and development of plants and human life and health.Heavy metals often exceed the standard in traditional Chinese medicine due to the enrichment of heavy metals in soil by plants.Li medicine is an essential part of traditional Chinese medicine,if heavy metals in Li medicine exceed the standard,it would not only damage the quality and reputation of Li medicine,but also hinder the development,utilization,and export trade of Li medicine resources.Therefore,it is of great importance to explore the enrichment and translocation characteristics of heavy metals in the soil-Li medicine system and evaluate the residual heavy metals and their risks in Li medicine for promoting the production of pollution-free and sound Li medicine,and sustainable development of the Li medicine industry in Hainan Province and the improvement of product quality.Taking major Li medicine like Hongkong Pavetta,Sharpleaf Galangal Fruit,Alpiniae Katsumadai Semen,Whitefruit Amomim Fruit and Fructus Amomi Longiligularis in Hainan Province as research objects,the soil physical and chemical properties,like the soil p H,organic matter content,available nutrient concentration,and the content of Cr,Cu,Cd,and Pb in the soil-Li medicine system were determined in this paper and the accumulation status,pollution,translocation and enrichment characteristics of heavy metals in the soil-Li medicine system were analyzed,and the target hazard coefficient method was used to assess the health risk of heavy metals in the medicinal parts of Li medicine.The research findings suggest:(1)The root soil of 6 kinds of Li medicine was acidic or faintly acidic with rich organic matter and available phosphorus,low potassium content and severely low nitrogen content.(2)The evaluation findings on the heavy metal accumulation index for the root soil of Li medicine indicated that the root soil of 6 kinds of Li medicine was severely polluted by Cd and Cr,followed by Cu and was free from Pb pollution.(3)The translocation capacity of Cr,Cd and Pb between stems and leaves was higher than those between roots and stems,while the translocation capacity of Cu within Li medicine plants was relatively weak.The enrichment coefficient of Cr,Cu,Cd and Pb in the roots,stems,and leaves of Li medicine indicated that the enrichment capacity of the roots and stems of Li medicine to the studied heavy metals was Cu>Cd>Cr>Pb,and the enrichment capacity of the leaves of Li medicine to the studied heavy metals was Cd>Cu>Cr>Pb.(4)The content of heavy metals in the root soil of Li medicine plants and their correlation with the soil’ s physical and chemical properties showed that there was a significant correlation between Cr and Cd,and a very significant correlation among Pb and Cu,Cd in heavy metals in the root soil of Li medicine plants.The soil p H is a primary factor affecting the content of Cr,Cu,Cd and Pb in the soil of Li medicine root system and nutritious elements for soil like ammonia-nitrogen,nitrate nitrogen,available phosphorus,organic matter and rapidly available potassium,are essential factors affecting heavy metal content in soil of Li medicine root system.(5)The content of heavy metals in the roots,stems and leaves of Li medicine plants and their correlation with the content of heavy metals in the root soil showed that i.There was a significant correlation between Cr and Cd in the roots,a significant correlation between Pb and Cu and Cr and Pb in the leaves,and a significant negative correlation between Pb and Cu in the stems of Li medicine plants.ii.There was a relatively weak correlation between Cr and Cd in the roots and the soil physical and chemical properties of the root soil,a significant correlation between Cu and ammonium nitrogen and nitrate nitrogen,a significant negative correlation between Cu and available phosphorus and available potassium,and a significant negative correlation between Pb and p H in the roots of Li medicine plants.iii.There was a relatively weak correlation between Cr and the soil’ s physical and chemical properties,a significant correlation between Cu and p H,ammonium nitrogen,available phosphorus,and available potassium,a significant correlation between Cd and nitrate nitrogen,a significant negative correlation between Cd and available potassium and an extremely negative correlation between Pb and p H in the stems of Li medicine plants.iv.There was no significant correlation between Cr and the soil’ s physical and chemical properties and an extremely significant correlation between Cu and p H,ammonia-nitrogen,available phosphorus and rapidly available potassium,no significant correlation between Cd and the soil’ s physical and chemical properties,and a negative correlation between Pb and the p H of root soil in the leaves of Li medicine plants.(6)The risk of heavy metal contamination in the roots of Li medicine was greater than that in the stems and leaves.The content of Cr and Cu in Li medicine plants was as follows,roots>stems>leaves and the content of Cd and Pb in was roots>leaves>stems.(7)The target hazard quotient(THQ)was adopted to conduct the health risk assessment of heavy metal content in medicinal parts of Li medicine,indicating that the residual heavy metal Cr in the medicinal parts of 6 kinds of Li medicine like Hongkong Pavetta(planted)and Hongkong Pavetta(wild),Sharpleaf Galangal Fruit,Alpiniae Katsumadai Semen,Whitefruit Amomim Fruit and Fructus Amomi Longiligularis,poses an intake risk to exposed populations,while Cu,Cd,and Pb have no significant impact on the physical health of adults and children.The findings of the exposure analysis also showed that the exposure levels of Cr in medicinal parts of the six kinds of Li medicine in the study area present an exposure risk to 100% of adults and children,while the exposure levels of Pb presented an exposure risk to 1.7% of adults and0.4% of children,and Cu and Cd presented no heavy metal exposure risk. |
