基于波谱响应特征的雄安新区农田土壤重金属含量反演

    Inversing heavy metal contents in farmland soil in Xiong’an New Area of China using spectral response characteristics

    • 摘要: 分析并监测雄安新区农田土壤污染状况,对于保障粮食安全、建设绿色雄安具有重要意义。该研究以雄安新区为研究区,基于多源遥感数据珠海一号(Zhuhai-1)OHS数据、哨兵二号(Sentinel-2)L2A级数据的波谱响应特征及实地测得的农田土壤重金属含量数据,在对土壤重金属含量单因子与多因子污染评价的基础上,筛选出3种超标的农田重金属元素铅(Pb)、铜(Cu)、锌(Zn),采用偏最小二乘回归方法(partial least squares regression,PLSR)建立农田土壤重金属含量反演模型。利用Zhuhai-1提取土壤样本点的原始光谱反射率以及4种变换后的光谱反射率,Sentinel-2提取7种对重金属胁迫敏感的植被指数,将其与3种土壤重金属含量作相关性分析,筛选出敏感波段与植被指数,即波谱响应特征,构建土壤重金属含量反演模型。结果表明,3种模型整体反演精度较为优良,Pb含量反演模型决定系数(determination coefficient,R2)为0.490,均方根误差(root mean squared error,RMSE)为4.66 mg/kg,平均绝对值误差(mean absolute error,MAE)为1.92 mg/kg;Cu含量反演模型R2为0.491,RMSE为16.85 mg/kg,MAE为3.69 mg/kg;Zn含量反演模型R2为0.664,RMSE为20.63 mg/kg,MAE为9.36 mg/kg。将该模型应用于雄安新区农田区域,得到大部分农田土壤中Pb含量均未超过风险筛选标准,在研究区西南部、西部部分区域Cu含量超过土壤污染风险筛选值,同时在研究区西部、西南部Zn污染较严重,雄安新区东南部部分农田有Zn零星分布,其他区域Cu和Zn含量未超过国家土壤污染风险管控值。因此,利用多源遥感数据波谱响应特征反演土壤重金属Pb、Cu和Zn含量,能够快速准确地实现对雄安新区土壤重金属污染情况的调查,同时为大面积土壤重金属含量监测提供解决方案。

       

      Abstract: Accurate monitoring of farmland environment and soil pollution is of great significance for food security and ecologically sustainable development in recent years. Taking Xiong'an New Area as the research area, this study aims to inverse the heavy metal content in farmland. Spectral response data of heavy metal content was extracted from multi-source remote sensing data Sentinel-2 (L2A), Zhuhai-1 (OHS), and field measurement. Pollution levels of heavy metal were evaluated in farmland soil using the one-factor and Nemero indexes. The heavy metal elements were screened to cause soil pollution in farmland, such as copper (Cu), zinc (Zn) and plumbago (Pb). Partial least squares regression (PLSR) was integrated with principal component and multiple linear regression. The quadratic inversion model was then established for the contents of the three heavy metal elements. The quantitative inversion of the heavy metal contents was realized in a wide range of soil. Sentinel-2 was used to extract seven vegetation indices, while Zhuhai-1 was to extract the original spectral reflectance of the sample points, as well as four transformed spectral reflectance of sample points. Pearson's correlation coefficient was used to analyze the correlation between spectral reflectance and vegetation index with the content of three heavy metal elements. A comparison was also made on the correlation coefficients, sensitive bands and vegetation indices. The spectral response indicators were modeled as the independent variables, while the measured parameters of the soil heavy metal contents were the dependent variables. The models were finally evaluated using the coefficient of determination (R2), mean absolute error (MAE), and root mean squared error (RMSE). The results showed that excellent performance was achieved in the overall inversion accuracy of the three models. The R2, RMSE, and MAE values of the Pb content inversion model were 0.490, 4.66, and 1.92 mg/kg, respectively. The inversion model was obtained for Cu with the R2 of 0.491, the RMSE of 16.85 mg/kg, and the MAE of 3.69 mg/kg. While, the inversion model of Zn was achieved with the R2 of 0.664, the RMSE of 20.63 mg/kg, and the MAE of 9.36 mg/kg. The spatial distribution of soil heavy metal content in farmland was mapped, according to the constructed inversion model of soil heavy metal content. The visualization of the inversion was conducive to the distribution of regional soil heavy metals from a more intuitive perspective. Among them, the Pb element content in soil in most areas was within the risk screening standard; Cu element exceeded the risk screening value of soil pollution in the southwestern and western parts of the test area; The western and southwestern parts of the test area were more seriously contaminated by Zn element, indicating the sporadic distributions in some farmlands in the southeastern part. The Cu and Zn contents in other areas were within the national risk control value of soil pollution. Therefore, the multi-source remote sensing data and spectral response can be expected to synergistically invert the Cu, Zn and Pb content of soil heavy metals. High feasibility and accuracy can also be obtained to investigate soil heavy metal pollution. At the same time, the findings can provide a theoretical basis for monitoring the heavy metal content of soil in large areas. A new idea can also be offered to construct the inverse model of heavy metal content in farmland soil.

       

    /

    返回文章
    返回