Study On The Absorption Of Chromium By Different Peanuts Varieties And It's Regulation Measures

Along with the accelerated process of urbanization and industrialization, a large number of industrial and urban pollutants have poured into rural areas,and the increasing rate of pesticide and fertilizer utilization as well as livestock emissions have led to serious heavy metal pollution in farmland, posing a serious threat to crop quality and safety of peanuts. Therefore, screening peanut varieties of low heavy metal accumulation could ensure agricultural production and food quality and safety. Through heavy metal content determination of peanut grain and their corresponding planting soil, two kinds of peanutswith grain chromium accumulation in magnitudes of difference were selected from 347 peanuts varieties collected from all around the country. Their growth status of the twovarietiesunder different chromium concentrationsand their chromium accumulation after application biochar or citric acid were also investigated. The major results of the study are summariesd as follows:The heavy metal contents of chromium, copper and cadmium in peanut grains of 347 different peanut varieties were measured, and the results showed that the heavy metal contents of different varieties are quite different.The chromium content ranged from 0.02 to10.62 mg·kg^-1, the copper content ranged from 0.04 to 23.92 mg·kg^-1, and the cadmium content ranged from 0.33 to 6.30 mg·kg^-1.Two peanut varieties, one named Dayingjiju with high level chromium concentration 10.62 mg·kg^-1while another named Shigou with low level chromium concentration 0.02mg·kg^-1in grain, were chosen as material for the next experiment.Two peanut varieties Dayingjiju and Shigou were exposed to 100 and 200 mg/kg soil chromium to investigate their growingresponses and chromiumaccumulation.The results showed that chromium contamination caused a marked reduction of plant height, root length and biomass in both peanut varieties. And the damage of chromium on roots was more obvious than that on the shoots of peanuts.Roots had the most accumulation of chromium in peanuts, and followed by stems, leaves.The data demonstrated that chromium was mainly distributed in the cell wall components in root, stem and leaf of peanuts. Chromium concentration in stems and leaves for Dayingjiju was significantly higher than that for Shigou when under low chromium contaminated soil.The soil p H and total nitrogen content increased after adding biochar, but the physicochemical properties of soil was unchanged when treated by critric acid. The content of hexavalent chromium in soilcould be significantly reduced by adding biochar and critic acid, and more than 80 percent chromium existed with residual forms in soil. Adding biochar could enhance residual chromium contents, and reduce the amount of the other forms such as oxidizable, reducible and exchangeable chromium in soil. But adding critric acid could reduce residual chromium contents. It indicated that biochar evidently decreased bioavailability of chromium in soil, alleviated the damage of chromium to penuts, and the contents of chromium in plants declined because dilution effect.