Chen Lin, Li Hong, Ma Jian-Jun, Wang Jin-Bao, Wang Jun-Mei, Liang Xiang-Yu, Jia Biao, Pang Dan-Bo, Xue Bin, Ma Kun
Key Laboratory for Restoration and Reconstruction of Degraded Ecosystem in Northwest China of Ministry of Education, Ningxia University, Yinchuan 750021, China.
Breeding Base for State Key Laboratory of Land Degradation and Ecological Restoration in Northwest China, Ningxia University, Yinchuan 750021, China.
Huan Jing Ke Xue. 2024 Dec 8;45(12):7209-7217. doi: 10.13227/j.hjkx.202312211.
Heavy metals are characterized by toxicity，non-biodegradability，and accumulation in the food chain；hence，o the distribution of heavy metals in farmland soils and crop food safety have attracted much attention. A total of 1 274 soil samples and crop samples were collected from farmland in Ningxia from 2017 to 2021 and bioconcentration coefficients were used based on the analysis of the elemental contents of Zn，Cr，Ni，Cu，Pb，As，Cd，and Hg. The ecological risk index and correlation analysis were used to characterize the heavy metal content and health risk assessment of the soil-crop system in Ningxia. The results showed that the soils in the study area were alkaline and the mechanical composition was dominated by pulverized and sandy grains，with a relatively small content of clay grains. The heavy metal contents in the soils were in the following order：Zn>Cr>Ni>Cu>Pb>As>Cd> Hg. Except for that of Cu and Ni，the contents of other heavy metals in the soils of the northern region were higher than those of the central and southern regions. The ecological risk index of soil heavy metals was Hg>Cd>As>Cu>Pb>Ni>Cr>Zn and the proportion of points with low and medium ecological risk index levels was high（98.58%），indicating that the soil environment was generally good. The average content of the eight heavy metals in crops did not exceed the limit value，and the average health risk index value was <1. However， the health risk index（HRI）of As in individual crops existed at points >1 in all three sub-regions and individual points with high values of HRI（HRI>1）for Cu and Ni were observed in crops in the northern region and for Pb in the north and south of the country，which require further attention. From the bioconcentration factor，crops showed no accumulation effect （BCF<1）for heavy metals such as As，Cd，Cr，Cu，Ni，Pb，and Zn and although the average uptake of Hg by crops did not show accumulation，a total of 31 crops in the three ecological zones showed some accumulation（BCF>1），which also requires further monitoring. Analysis using the Mantel's test showed that except for As and Ni in crops，which had a weak correlation with Cu content in the soil（0.05>Mantel's >0.01），the other heavy metals in crops did not have a significant correlation with the corresponding soil heavy metals （Mantel's ≥0.05），indicating that the heavy metal contents in crops were less affected by soil heavy metals. RDA analysis showed that the sand content had a strong positive correlation with the transfer coefficients of heavy metals such as Hg，Ni，Pb，and Cd，while the powder content showed a strong negative correlation；however，the transfer coefficients of Cu，Zn，As，and Cr were not much affected by the mechanical composition of soils，and the correlation between the soil organic matter content and the transfer coefficients of heavy metals was also small. In summary，the quality of the soil environment and crops in the study area is generally good；however，attention must still be paid to the areas with high heavy metal content or exceeding the standard value to strictly control the input of pollutants，and at the same time，establishing long-term monitoring of the quality status of soil and agricultural products in the crop production area is a necessary control initiative.
重金属具有毒性、不可生物降解性以及在食物链中累积的特点；因此，农田土壤中重金属的分布以及作物食品安全备受关注。2017年至2021年期间，从宁夏农田采集了共计1274份土壤样本和作物样本，并在分析锌、铬、镍、铜、铅、砷、镉和汞的元素含量的基础上，采用了生物富集系数。利用生态风险指数和相关性分析对宁夏土壤-作物系统中的重金属含量及健康风险评估进行了表征。结果表明，研究区土壤呈碱性，机械组成以粉粒和砂粒为主，黏粒含量相对较少。土壤中重金属含量顺序为：锌>铬>镍>铜>铅>砷>镉>汞。除铜和镍外，北部地区土壤中其他重金属含量高于中部和南部地区。土壤重金属生态风险指数为汞>镉>砷>铜>铅>镍>铬>锌，低、中生态风险指数水平的点数占比高（98.58%），表明土壤环境总体良好。作物中8种重金属的平均含量未超过限值，平均健康风险指数值<1。然而，所有三个子区域个别作物中砷的健康风险指数（HRI）均存在>1的点位，北部地区作物中铜和镍以及南北部地区作物中铅出现了个别HRI高值点位（HRI>1），需要进一步关注。从生物富集系数来看，作物对砷、镉、铬、铜、镍、铅和锌等重金属无累积效应（BCF<1），虽然作物对汞的平均吸收未表现出累积，但三个生态区共有31种作物表现出一定累积（BCF>1），这也需要进一步监测。利用Mantel检验分析表明，除作物中的砷和镍与土壤中铜含量呈弱相关（0.05>Mantel's>0.01）外，作物中其他重金属与相应土壤重金属无显著相关性（Mantel's≥0.05），表明作物中的重金属含量受土壤重金属影响较小。冗余分析（RDA）表明，砂含量与汞、镍、铅和镉等重金属的转移系数呈强正相关，而粉粒含量呈强负相关；然而，铜、锌、砷和铬的转移系数受土壤机械组成影响不大，土壤有机质含量与重金属转移系数之间的相关性也较小。综上所述，研究区土壤环境和作物质量总体良好；然而，仍需关注重金属含量高或超标区域，严格控制污染物输入，同时，对农作物生产区土壤和农产品质量状况建立长期监测是必要的管控举措。
