Assessment of groundwater quality of middle – Upper pleistocene aquifer in Ca Mau peninsula

Abstract

Groundwater quality is a matter of concern in Ca Mau Peninsula. There have been many organizations, domestic and foreign scientific researchersworking on the issue, and they have produced various results regardinggroundwater pollution (arsenic, heavy metal, minerals, or saltwater intrusion…). In this paper, the authors assess groundwater quality by using the water quality index (WQI) to transform complex data into simple indicators that are easy to understand, and let people in the studied areas be aware of the pollution issue of the water resources they are using. Groundwater samples are collected from national monitoring wells and from exploitation works in the area. Indicators such as pH, TDS (total dissolved solids), total hardness (TH), total alkalinity (Na ++ K +), sulfate (SO42-), chloride (Cl), and nitrate ( NO3) are used to calculate WQI values.The WQI values of the middle Pleistocene aquifers of Ca Mau Peninsula range from 36.09 to 1,344. Based on these values, authors have classified groundwater samples into 5 groups of different qualities, from the very high quality to the unusable one. The very high quality accounts for 14% of the samples; good quality accounts for 49%, average quality accounts for 24%, poor quality accounts for 7%, and unusable accounts for 6% of the total samples.There is about 10% of the samples exceeding permissible limits of TDS, whereas the sulfate and chloride range from 20% to 21%. Samples of poor and unusable qualityare mainlyfrom Soc Trang province. Most of themhavethe TDS levels greater than 1, and some have an abnormally high level ofsulfatewhen compared with other samples in the area. The study hasyielded a more comprehensive assessment of groundwater quality, allowing regulators to plan water resources more reasonably and be able togive in time advices tothe people.