Screening Of Crop Varieties For Planting Structure Adjustment In Farmland Contaminated By Heavy Metals

The present situation of heavy metals pollution in farmland in China is serious.How to control the risk of heavy metals pollution in farmland is an urgent problem to be solved.In this experiment,18 varieties of rice（Oryza sativa L.）,14 varieties of corn（Zea mays L.）,8 varieties of balsam pear（Momordica charantia L.）,5 varieties of pea pods（Pisum sativum L.）,and 7 varieties of tomato（Lycopersicon esculentum Mill.）were selected as experimental varieties.The experimental site was the farmland with heavy cadmium pollution around Shaoguan Thermal Power Plant in Wushi Town,Qujiang District,Shaoguan City.The purpose of this experiment was to study the differences of accumulation of heavy metals Cd,Pb and As in soil among different crop varieties,and to screen out crops with high safety.The results provide a theoretical basis for the adjustment of planting structure of heavy metals polluted farmland.The field test results are as follows:（1）The Cd content in brown rice（Oryza sativa L.）of 18 varieties ranged from 2.77mg·kg^-1to 4.04 mg·kg^-1with an average of 3.41 mg·kg^-1,the Pb content ranged from 0.105mg·kg^-1to 0.187 mg·kg^-1with an average of 0.145 mg·kg^-1,the As content ranged from0.059 mg·kg^-1to 0.127 mg·kg^-1with an average of 0.092 mg·kg^-1.Among them,the Cd content in rice（Oryza sativa L.）was much higher than the 0.2 mg·kg^-1defined by the national food safety standards（GB2762-2017）,but neither Pb nor As content exceeded the standard.（2）The Cd content of 14 corn（Zea mays L.）seeds of different varieties ranged from0.023 mg·kg^-1to 0.606 mg·kg^-1with an average of 0.263 mg·kg^-1,the Pb content ranged from 0.006 to 0.206 mg·kg^-1with an average of 0.093 mg·kg^-1,and the As content ranged from 0.009 to 0.045 mg·kg^-1with an average of 0.023 mg·kg^-1.Among them,only Zhuyunuo No.1,Zhengda 999 and Zhongnuo No.1 had lower Cd,Pb and As contents than the limits of national food safety standards（GB2762-2017）.（3）The Cd content in edible parts of 8 different varieties of balsam pear（Momordica charantia L.）ranged from 0.007 mg·kg^-1to 0.014 mg·kg^-1with an average of 0.010 mg·kg^-1,the Pb content ranged from 0.023 to 0.061 mg·kg^-1with an average of 0.040 mg·kg^-1,the As content ranged from 0.001 to 0.005 mg·kg^-1with an average of 0.003 mg·kg^-1.The Cd content of edible parts of 5 varieties of pea pods（Pisum sativum L.）ranged from 0.010 to0.041 mg·kg^-1with an average of 0.021 mg·kg^-1,Pb content ranged from 0.001 to 0.017mg·kg^-1with an average of 0.007 mg·kg^-1,As content ranged from 0.0011 to 0.0023mg·kg^-1with an average of 0.0014 mg·kg^-1.The contents of Cd,Pb and As in the edible parts of balsam pear（Momordica charantia L.）and pea pods（Pisum sativum L.）are all lower than the limit value of national food safety standard（GB2762-2017）.（4）The content of Cd in edible parts of 7 varieties of tomatoes（Lycopersicon esculentum Mill.）ranged from 0.036 to 0.064 mg·kg^-1with an average of 0.047 mg·kg^-1,Pb content ranged from 0.001 to 0.013 mg·kg^-1with an average of 0.005 mg·kg^-1,As content ranged from 0.0002 to 0.0010 mg·kg^-1with an average of 0.0007 mg·kg^-1.Among them,the content of Cd in Golden Pearl and Golden Consort tomato（Lycopersicon esculentum Mill.）is slightly higher than the national food safety standard（GB2762-2017）,which is 0.05mg·kg^-1.The content of Cd,Pb and As in the other five varieties（Black Pearl,Jade Girl,Millennium,Jin Linglong and Jin Bao）tomatoes（Lycopersicon esculentum Mill.）are not beyond the standard,which are the kind of low accumulation of heavy metals.（5）The cumulative capacity of Cd in soil of different crops was rice（Oryza sativa L.）>corn（Zea mays L.）>tomato（Lycopersicon esculentum Mill.）>pea pods（Pisum sativum L.）>balsam pear（Momordica charantia L.）.The accumulative ability of Pb and As in soil was rice（Oryza sativa L.）>corn（Zea mays L.）>balsam pear（Momordica charantia L.）>pea pods（Pisum sativum L.）>tomato（Lycopersicon esculentum Mill.）.