Evaluating the Heavy Metal Risks of Soil and Rice from a Farmland in a Nanjing Suburb through In-vitro Simulation Tests
Chenghui Han 1  
,   Weifang Xie 1  
,   Chen Chen 2  
,   Ting Cheng 1  
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School of Environment and Ecology, Jiangsu Open University, Nanjing 210036, China
School of Environmental and Chemical Engineering, Jiangsu University of Science and Technology, Zhenjiang 212003, China
Chenghui Han   

School of environment and ecology, Jiangsu Open University, China
Submission date: 2020-06-07
Final revision date: 2020-09-10
Acceptance date: 2020-09-15
Online publication date: 2021-01-29
The risks from heavy metals in soil and rice from a farmland in a Nanjing suburb, southeastern China, were evaluated using the geo-accumulation index, a health risk assessment and an in-vitro simulation. The concentrations of heavy metals (Pb, Cr, Zn, Cu, Cd, Hg, and As) in the soil and rice were determined in the present study. The results showed that at the two stages measured, the order of geoaccumulation index values (except those of Pb and Zn) was Cd>As>Hg>Cu>Cr. Moreover, the heavy metals with lower Igeo values exhibited lower risks at both stages in the study area. The farmland in the study area was not polluted by heavy metals, according to the evaluation of the total heavy metal contents and their chemical speciation. The order of bio-concentration factor was Cd>Cu>Zn>Pb>As>Cr>Hg. For all heavy metals, the non-carcinogenic doses of the different exposure pathways indicated that CDIing-nc>CDIdermal>CDIinh-nc for children and adults. The HI values for adults and children from heavy metals before rice sowing were 0.0984 and 0.634, respectively, indicating that these metals had little influence on the human body. The HI values for adults and children for heavy metals at the rice harvesting stage were 0.146 and 0.879, respectively. Before rice sowing, the lifetime carcinogenic risk values for local adults and children were 5.60 × 10−5 and 8.15 × 10−5, respectively. At the rice harvesting stage, the lifetime carcinogenic risk values for local adults and children were 3.01 × 10−5 and 4.48 × 10−5, respectively. At both stages, the order of CF values for adults and children was Cd>Cr>As>Pb. The total amounts and bioavailable amounts of the heavy metals ingested by adults and children through eating the local rice did not exceed the tolerable weekly intake values, indicating that there is no health risk from eating the local rice. However, draining and drying the field at the proper time would improve the Eh value of the paddy soil.