Spatial variation of chemical variables in the critical zone of the Luan River catchment in north China plain

Traditional chemical methods have mainly focused on the variation and transportation of elements in the aquifer layer. The primary goal of this paper was to establish a spatial distribution model of chemical elements in the critical zone (CZ). The effects of anthropogenic activities (AA) and CZ structure on these models are quantitatively described. To this aim, 200 sediment and pore water samples were collected from ten drills in two profiles and analyzed for 16 variables. The most important influencing factors were identified from CZ structure parameters, and the effects of AA and CZ structure on chemical variables in the CZ were quantitatively characterized. Distribution models of the influences of AA and CZ structure were established for these two profiles. The correlation coefficient of the clay fraction content was greater than the other parameters, which was negative with total dissolved solids (TDS) and the arsenic of pore water and was positive with the arsenic in sediments. The distribution model of chemical variables was divided into three components: CZ1, CZ2, and A-A, which represent the effects of the first and second most important influencing factors and AA. The distribution models of chemical variables and their A-A part had the strongest similarity. The clay fraction content was more important than the other CZ structure parameters. It can inhibit the TDS and arsenic of pore water migration, resulting in greater arsenic ion adsorption on the sediment. AA is a triggering factor for chemical variables transportation, and CZ structure has an amplification effect on AA. According to characterize the spatial distribution of chemical variables in sediment and pore water within the CZ, the effects of AA and CZ structure can be quantitatively described, providing a rapid and effective technique for ecological environmental protection.