Fig 1.
Location of the study area.
Fig 2.
PXRF and portable VNIR analyzers.
Fig 3.
Representative soil spectrum of XRF, highlighting the qualification ranges of soil heavy metals.
Table 1.
Table 2.
Descriptive statistics for heavy metal concentrations in soils (mg/kg).
Table 3.
Comparison between the prediction accuracy of PLSR models with different spectral preprocessing methods.
Fig 4.
Prediction scatter plot of pH (a) and VIP scores of optimized PLSR model (b).
Table 4.
Descriptive statistics for heavy metal concentrations in soils by PXRF methods (mg/kg).
Fig 5.
Regression of PXRF measurements against ICP-AES analysis for trimmed datasets.
The red, green and blue dotted lines represent the national standard value of heavy metals when pH <6.5, 6.5–7.5 and >7.5.
Table 5.
Comparison of heavy metal pollution grade classification between PLSR and chemical analysis.