Accumulation Characteristics Of Heavy Metals In Soil And Crops And Environmental Evaluation Of Eiable Crop Production For Food Security In Geological Anomaly Area In Northern Part Jiangsu Province

A basic balance has been achieved between the total supply and demand, with even a surplus during harvest years, by the sharply development of.agricultural production since the end of the21st century in China. However, many quality safety risks have still existed in the food production. Production, processing and marketing are three pillars affecting food security, among which production process is the crucial part. In recent years, based on the soil environment quality investigation in many areas of China,, the accumulation of heavy metals in surface soil has been found to be one of the important factors that affect agricultural products safety. As in Jiangsu Province, the latest finding of geochemical survey also showed that the enrichment of heavy metals were founded in arable soils in many regions, which has potential risk on the security of agricultural products. Apart from the pollution caused by human activities such as industrial emissions and vehicle exhausts, geological anomaly is one of the essential reasons for the enrichment of heavy metals, especially in the northern part of Jiangsu Province. The northern region, however, is vital in the production of agricultural products, where grain and vegetable annual output is more than a half of the total production in the province. In previous studies, more attention was paid to the impacts of human activities on the surrounding environment and security of agricultural products, such as chemical enterprise and road traffic, with little concern on the potential risks of soil heavy metal enrichment in surface soils caused by geological anomaly. Therefore, present study systematically analyses the accumulation characteristics of heavy metals in soil in geological anomaly area located in Jiangsu northern part and the potential risks of heavy metal accumulation to the agricultural products, which is expected to provide reference for the monitoring and evaluation of soil quality of arable land and food security in geological anomaly area. The main findings of this study are as follows:1. Based on the soil sampling and monitoring in the typical geological anomaly area (Guanyun and Guan South district in Lianyungang, Feng and Pei County in Xuzhou, Xuyi western part in Huaian), the enrichment of As, Pb, Cr, Cd and Cu primarily exist in the surface soil. The contents of these heavy metals are higher than the background and average values of Jiangsu Province, but has still not surpassed the limits of level-two standard in national soil quality.2. In the rice samples collected from these regions, the average and maximum content of Hg and Cd in rice and rice bran are less than national limits for food secutiy, but the contents of As, Pb and Cr in some samples of polished rice and rice bran has gone beyond the limits. The average and maximum contents of Hg and Cr in wheat grains have not exceeded the national limits, but the contents of As, Pb and Cd in some samples have already surpassed the national limits. The heavy metals contents in the edible organs of garlic, lettuce, leeks, onions and cabbages are low, far less than the national limits. These findings indicate that the enrichment of heavy metals, such as As and Pb, in surface soil in geological anomaly area poses a security risk on rice and wheat, but less risk is found in the vegetables.3. The correlations between heavy metals in crops and soils were further conducted; and the results showed that the contents of heavy metals in polished rice and vegetables had low relevance to that in soil. The Cd content in wheat grains showed strong correlation with that in soil. But, little relevance was found between the contents of As and Pb in wheat grains and soil. Therefore, in the evaluation of potential risk caused by soil heavy metals enrichment in geological anomaly area, the Cd content in soil can be referred to in the evaluation of potential of potential risk of Cd content in wheat grains. However, as for other heavy metals, the impacts of bioavailable contents, soil physical and chemical nature as well as agronomy measures must also be integrated into account.4. On the basis of the above study, a comprehensive evaluation has been carried on about risks of soil heavy metal contents and suitability of edible food production for food security. In the study area, soil heavy metal contents are on the security level in most regions and suitable for the production of green and non-pollution agricultural products. The area of these regions accounted for about88%of the entire study area. The regions in the medium risk level mainly located in the south-west part in Xuyi and some areas along both sides of Xinyi River in Guanyun and Guan South, where has certain security risk to some edible crops. The area of these regions makes up12%of the total area. But only small part distributed in south-west part of Xuyi is in high-risk level, whose area is only0.1%of the total area. This region is not suited to the production of edible crops.