Study On Wheat Safety-production In Arable Soil And Regional Warning

Wheat is one of the three major staple crops in China.Recently,cadmium has exceeded the limt in several wheat growing regions.It is an effective measure to ensure wheat production safety to accurately predict cadmium content of wheat grains in risk areas by using existing soil test data.It could also provide scientific basis for local government to ensure food safety production and management.In this study,320 sets of soil-wheat collaborative test samples were collected from soil heavy metal pollution risk blocks and surrounding farmland in Henan Province from 2020 to2022.Soil physical-chemical properties were determined,including soil p H and organic matter,as well as the contents of cadmium,lead,copper,zinc,manganese and iron in soil and wheat grains.Prediction model of heavy metal cadmium in wheat grain was established,and the warning value of cadmium in soil for wheat safe production was deduced based on the characteristics of soil studied.It could provide scientific basis for the safe production of wheat in Henan province.The main results and conclusions are as follows:(1)According to the risk screening value in "Soil Environmental Quality Standard for Soil Pollution Risk Control of Agricultural Land(Trial)"(GB 15618-2018),the point exceeding rate of cadmium in soil from risk blocks and surrounding farmland reached 40%,the point exceeding rate of lead content in soil was 10%,and the exceeding rate of copper and zinc content in soil were only 1.25% and 5.94%,respectively.The proportion of wheat grains with cadmium and lead content exceeding the limits of the National Food Safety Standard for Pollutants in Foods(GB 2762-2017)could arrive at 32% and 8%,respectively.(2)In this study,soils was mainly alkaline(p H>7.5).Among these alkaline soil sites investigated,it accounted for 12%,6%,13%,and 6% of slight pollution,mild pollution,moderate pollution and severe pollution induced by cadmium,respectively.If only considering the factor of soil cadmium content,a linear regression equation could be established with wheat grains: lg[Cd]grain=0.74×lg[Cd]soil-0.96.For the basis,if the cadmium content in wheat grains is to comply with the limit in GB 2762-2017,soil cadmium should be less than 0.87 mg kg-1 theoretically.(3)In the alkalinesites with soil cadmium content lower than 0.87 mg kg-1,about 4% of wheat grains still exceeded the standard of cadmium,and further measures for safety production should be taken.After comprehensive analysis of soil cadmium content,p H,organic matter and co-existing elements such as lead,copper,zinc,manganese and iron,multiple regression equation: lg[Cd]grain=0.83×lg[Cd]soil-0.34×lg[Zn]soil-0.26×lg[OM]+0.06 could better explain the relationship between soil and wheat grain cadmium.(4)The cadmium content in wheat grains from alkaline soil was influenced by organic matter and soil zinc content.Therefore,soil cadmium warning value was estimated at 0.61 mg kg-1 in order to achieve safe production of wheat in alkaline soil,which was close to the risk screening value in GB 15618-2018.When the soil had high levels of organic matter or zinc,it could effectively inhibit the accumulation of cadmium in wheat grains,and thus soil cadmium warning value should be relaxed appropriately.