*4.3. Visual Minteq Model Analysis*

*4.3. Visual Minteq Model Analysis* In order to further analyze the possible ionic forms that could be formed as a result of chemical reactions between As ions and other ions in the water environment of the study area, Visual Minteq was used to simulate the pH, ion concentrations, and possible products of the water environment. The data to be entered included pH, temperature, K+, Na+, Ca2+, Mg2+, Fe2+, and As. The possible compounds of As produced by the simulations in the study area context are depicted in Figure 7 and include AsO43−, H2AsO4−, H3AsO4 and HAsO42−. As can be seen from Figure 7, among all the possible ionic forms of As formed during the wet and dry seasons of 2017 and 2018, the activity of HAsO42<sup>−</sup> had the largest logarithmic value while that of H3AsO4 had the smallest value, regardless of pH change. The minimum and maximum values for HAsO42<sup>−</sup> were −7.331 and −5.784 in the 2017 dry season and −7.274 and −5.645 in the wet season, respectively. The minimum and maximum values for HAsO42<sup>−</sup> were −7.85 and −5.371 in the 2018 dry season and −7.342 and −6.212 in the wet season, respectively. The minimum and maximum values for H3AsO4 were −15.142 and −12.222 in the dry season and −14.648 and −11.895 in the rainy In order to further analyze the possible ionic forms that could be formed as a result of chemical reactions between As ions and other ions in the water environment of the study area, Visual Minteq was used to simulate the pH, ion concentrations, and possible products of the water environment. The data to be entered included pH, temperature, K<sup>+</sup> , Na<sup>+</sup> , Ca2+, Mg2+, Fe2+, and As. The possible compounds of As produced by the simulations in the study area context are depicted in Figure 7 and include AsO<sup>4</sup> <sup>3</sup>−, H2AsO<sup>4</sup> <sup>−</sup>, H3AsO<sup>4</sup> and HAsO<sup>4</sup> <sup>2</sup>−. As can be seen from Figure 7, among all the possible ionic forms of As formed during the wet and dry seasons of 2017 and 2018, the activity of HAsO<sup>4</sup> <sup>2</sup><sup>−</sup> had the largest logarithmic value while that of H3AsO<sup>4</sup> had the smallest value, regardless of pH change. The minimum and maximum values for HAsO<sup>4</sup> <sup>2</sup><sup>−</sup> were <sup>−</sup>7.331 and <sup>−</sup>5.784 in the 2017 dry season and −7.274 and −5.645 in the wet season, respectively. The minimum and maximum values for HAsO<sup>4</sup> <sup>2</sup><sup>−</sup> were <sup>−</sup>7.85 and <sup>−</sup>5.371 in the 2018 dry season and −7.342 and −6.212 in the wet season, respectively. The minimum and maximum values for H3AsO<sup>4</sup> were −15.142 and −12.222 in the dry season and −14.648 and −11.895 in the rainy season, respectively. The minimum and maximum values of H3AsO<sup>4</sup> were −14.75 and −12.129 in the 2018 dry season and −14.666 and −12.509 in the rainy season, respectively.

season, respectively. The minimum and maximum values of H3AsO4 were −14.75 and −12.129 in the 2018 dry season and −14.666 and −12.509 in the rainy season, respectively.

**Figure 7.** Logarithmic values of the activities of the possible compounds of As generated by the simulations. **Figure 7.** Logarithmic values of the activities of the possible compounds of As generated by the simulations.

### **5. Conclusions and Recommendations 5. Conclusions and Recommendations**

In this study, 49 sets of observations from relatively continuous and complete monitoring sites were used to compare the health risks posed to adults and children by oral intake and dermal contact with drinking water in Yinchuan during the dry and rainy seasons in 2017 and 2018, assessing the health risks of Mn, NO2−, Fe, F, Pb, Cr6+, Cd, As, and ammonia nitrogen. According to these data, the HI index exceeded the value of 1 at 17 sampling points for adults and 67 for children. The average CR values for adults for As in the study area for 2017 were 2.94 × 10−0.5 and 5.93 × 10−0.5 for the dry and rainy seasons, respectively, while for 2018 they were 5.48 × 10−0.5 and 3.59 × 10−0.5, respectively. In parallel, the CR values for children for 2017 were 6.28 × 10−0.5 and 1.27 × 10−0.4, respectively, and 1.17 × 10−0.4 and 7.67 × 10−0.5, respectively, indicating a considerably higher carcinogenic risk for In this study, 49 sets of observations from relatively continuous and complete monitoring sites were used to compare the health risks posed to adults and children by oral intake and dermal contact with drinking water in Yinchuan during the dry and rainy seasons in 2017 and 2018, assessing the health risks of Mn, NO<sup>2</sup> <sup>−</sup>, Fe, F, Pb, Cr6+, Cd, As, and ammonia nitrogen. According to these data, the HI index exceeded the value of 1 at 17 sampling points for adults and 67 for children. The average CR values for adults for As in the study area for 2017 were 2.94 <sup>×</sup> <sup>10</sup>−0.5 and 5.93 <sup>×</sup> <sup>10</sup>−0.5 for the dry and rainy seasons, respectively, while for 2018 they were 5.48 <sup>×</sup> <sup>10</sup>−0.5 and 3.59 <sup>×</sup> <sup>10</sup>−0.5, respectively. In parallel, the CR values for children for 2017 were 6.28 <sup>×</sup> <sup>10</sup>−0.5 and 1.27 <sup>×</sup> <sup>10</sup>−0.4, respectively, and 1.17 <sup>×</sup> <sup>10</sup>−0.4 and 7.67 <sup>×</sup> <sup>10</sup>−0.5, respectively, indicating a considerably higher carcinogenic risk for children than for adults.

children than for adults. The results of the sensitivity analysis of Cr6+ and As using Crystal Ball software showed that in 2017 the association values were 0.9958 and 1 for As and 0.0948 and 0 for Cr for the dry and rainy seasons, respectively, while in 2018 they were 0.7424 and 0.5759 for As and 0.6237 and 0.8182 for Cr for the dry and rainy seasons, respectively. This means that the association values for As were lower than those for Cr only in the 2018 rainy The results of the sensitivity analysis of Cr6+ and As using Crystal Ball software showed that in 2017 the association values were 0.9958 and 1 for As and 0.0948 and 0 for Cr for the dry and rainy seasons, respectively, while in 2018 they were 0.7424 and 0.5759 for As and 0.6237 and 0.8182 for Cr for the dry and rainy seasons, respectively. This means that the association values for As were lower than those for Cr only in the 2018 rainy season, indicating that As is most sensitive to overall carcinogenic risk.

season, indicating that As is most sensitive to overall carcinogenic risk. The results of the visual coinage model analysis allowed us to conclude that the activity of HAsO42<sup>−</sup> had the largest logarithmic value, while that of H3AsO4 had the smallest logarithmic value among all the possible ionic forms of As, regardless of the The results of the visual coinage model analysis allowed us to conclude that the activity of HAsO<sup>4</sup> <sup>2</sup><sup>−</sup> had the largest logarithmic value, while that of H3AsO<sup>4</sup> had the smallest logarithmic value among all the possible ionic forms of As, regardless of the change in pH. This indicates that HAsO<sup>4</sup> 2 is the ionic form of As with the main carcinogenic factor in the hydrogeological environment of the study area.

change in pH. This indicates that HAsO42 is the ionic form of As with the main carcinogenic factor in the hydrogeological environment of the study area. Based on these results, it is recommended to strengthen the monitoring and control Based on these results, it is recommended to strengthen the monitoring and control of As, especially of HAsO<sup>4</sup> <sup>2</sup>−, levels in groundwater in the study area.

**Author Contributions:** Conceptualization, Z.M. and J.L.; methodology, M.Z.; software, D.Y.; validation, Z.M., J.L. and M.Z.; formal analysis, Y.Z.; investigation, Z.M.; resources, Y.Z.; data

of As, especially of HAsO42−, levels in groundwater in the study area.

**Author Contributions:** Conceptualization, Z.M. and J.L.; methodology, M.Z.; software, D.Y.; validation, Z.M., J.L. and M.Z.; formal analysis, Y.Z.; investigation, Z.M.; resources, Y.Z.; data curation, M.Z.; writing—original draft preparation, M.Z.; writing—review and editing, D.Y.; visualization, Z.G.; supervision, Z.G.; project administration, Y.Z.; funding acquisition, Z.G. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research is funded by Open project of Hebei key laboratory of geological resources and environmental monitoring and protection (JCYKT202101); Natural Science Foundation of Hebei Province of China (D2022403016); Hebei water conservancy science and technology plan project (2021-45). Hebei University Science and technology research project (ZD2022119); Science and technology innovation team project of Hebei GEO University (KJCXTD-2021-14); Introduction of foreign intelligence project in Hebei province in 2021 (2021ZLYJ-1).

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** Data availability statement can be said to be the monitoring data of Hebei Institute of hydrogeology and engineering geology, real and reliable.

**Acknowledgments:** The author thanks Hebei Geological Environment Monitoring Institute, and Hebei Institute of hydrogeology and engineering geology providing real and reliable data.

**Conflicts of Interest:** The authors declare no conflict of interest.
