| Summary: | Karst groundwater is one of the primary water resources in most provinces of Southwestern China where karst topography is strongly featured. In Guizhou Province, a prominent geologic sedimentary formation is the dolomite stratum which exists as the restricted platform facies and potentially provides a large reservoir for drinking water. A proper understanding and evaluation of its hydrogeochemical characteristics and water quality is the key to ensuring the drinking water safety. In the present study, groundwater samples were collected from 25 locations of the dolomite aquifer across Guizhou to determine their major chemical compounds, including the cations (<inline-formula><math display="inline"><semantics><msup><mi mathvariant="normal">K</mi><mo>+</mo></msup></semantics></math></inline-formula>, <inline-formula><math display="inline"><semantics><msup><mi>Na</mi><mo>+</mo></msup></semantics></math></inline-formula>, <inline-formula><math display="inline"><semantics><msup><mi>Ca</mi><mrow><mn>2</mn><mo>+</mo></mrow></msup></semantics></math></inline-formula>, <inline-formula><math display="inline"><semantics><msup><mi>Mg</mi><mrow><mn>2</mn><mo>+</mo></mrow></msup></semantics></math></inline-formula>) and the anions (<inline-formula><math display="inline"><semantics><msubsup><mi>HCO</mi><mn>3</mn><mo>−</mo></msubsup></semantics></math></inline-formula>, <inline-formula><math display="inline"><semantics><msup><mi mathvariant="normal">F</mi><mo>−</mo></msup></semantics></math></inline-formula>, <inline-formula><math display="inline"><semantics><msup><mi>Cl</mi><mo>−</mo></msup></semantics></math></inline-formula>, <inline-formula><math display="inline"><semantics><msubsup><mi>NO</mi><mn>3</mn><mo>−</mo></msubsup></semantics></math></inline-formula>, <inline-formula><math display="inline"><semantics><msubsup><mi>SO</mi><mn>4</mn><mrow><mn>2</mn><mo>−</mo></mrow></msubsup></semantics></math></inline-formula>), as well as the pH, total hardness, and total dissolved solids. <inline-formula><math display="inline"><semantics><msubsup><mi>HCO</mi><mn>3</mn><mo>−</mo></msubsup></semantics></math></inline-formula> and <inline-formula><math display="inline"><semantics><msup><mi>Ca</mi><mrow><mn>2</mn><mo>+</mo></mrow></msup></semantics></math></inline-formula> were found to be the dominant anion and cation, respectively, which is characteristic of typical karst groundwater and supports the overall observation of a slightly weak acid to weak alkaline environment in the studied groundwater, as the pH measurements ranged from 6.80 to 8.37. Fuzzy comprehensive evaluation method is used to evaluate the groundwater quality based on typical drinking water safety standard. The results show that the groundwater in most of the studied aquifers is of reasonably good quality. However, in some aquifers, concentrations of <inline-formula><math display="inline"><semantics><msubsup><mi>NO</mi><mn>3</mn><mo>−</mo></msubsup></semantics></math></inline-formula> and/or <inline-formula><math display="inline"><semantics><msubsup><mi>SO</mi><mn>4</mn><mrow><mn>2</mn><mo>−</mo></mrow></msubsup></semantics></math></inline-formula> were found to be excessively high. Overall, the studied dolomite aquifer in its natural environment as investigated in the present study can be considered as a potential geological stratum for water resources exploitation in Guizhou.
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