**2. Description of the Study Area**

The study area is located in the northwestern part of Xinxiang City, Henan Province (Figure 1), with a temperate continental monsoon climate and a multi-year average temperature of 14 ◦C. The multi-year average precipitation is 586.32 mm, with more than 70% occurring in the rainy season spanning June to September. The multi-year average evaporation is 1772.62 mm, which is three to four times the precipitation with the strongest evaporation in June.

**Figure 1.** Location of the study area and the sampling sites. DGW represents deep groundwater. SGW represents shallow groundwater. Dots represent shallow sampling points. Triangles represent deep sampling points. The boundary represents the boundary of the numerical model. Henan is located in the central part of China. Xinxiang City is located in the north of Henan Province.

Xinxiang City is located at the southeastern foot of Taihang Mountains and the northern edge of the alluvial plain in the middle and lower reaches of the Yellow River. The terrain generally inclines from northwest to southeast. The regional landform types are divided into three types of landforms: alluvial valley, alluvial sloping plains and alluvial plains. The geomorphological type of the study area is alluvial sloping plain. The surface of the study area reveals the Quaternary river-phase sedimentary layer with a thickness of 50–60 m, and the lithology is mainly clay and sand. The groundwater type is pore water of loose rock of the Quaternary, and the media of the aquifer are mainly medium sand and fine sand, with coarse sand locally. According to the profile, it can be seen that the lithology from 56 m to 49 m is silty clay and silt. The lithology from 59 m to 49 m is silty clay and silt. This is followed by a shallow aquifer with a thickness of 3 m. However, the aquifer thickness increased significantly at borehole S22. The lithology from 46 m to 36 m is mainly silty clay. The bottom lithology is mainly fine sand. The aquifer is mainly recharged by atmospheric precipitation, lateral runoff and irrigation recharge, and groundwater discharge is mainly exploitation, evaporation and lateral runoff.

Chromium salt chemical plants existed in the study area during the historical period, and chromium slag from the production process brought serious contamination to the site

soil and groundwater (Figure 2). Test results showed that the average concentration of total chromium in the soil was 12,100 mg/kg, and work has been carried out to remediate the soil and groundwater.

**Figure 2.** The hydrogeological cross section along the A–B and pollution conceptual model. In the pollution plume, the red color represents the high concentration value. Yellow color represents low concentration value.
