Some Physico-Chemical Characteristics of Surface Water in Mining Areas in the Lao PDR

抄録

Lao People's Democratic Republic (the Lao PDR), is naturally enriched with mineral resources having been the important potential in the country socio-economic development. Mining activities for utilizing such resource is expected to bring not only benefit but also environmental problems such as deforestation due to land opening, surface water quality decline. The objective of this study was to initially investigate the surface water quality of the two main rivers (Namkok and NamMo) near two mining areas (Sepon and PhuBia) in Savannakhet and Xaysomboun provinces, respectively. Water samples from 5 sampling sites on each river were analyzed for physical (pH, EC, temperature, turbidity, TDS,) and chemical (alkalinity, DO, COD, inorganic cations and anions, and some heavy metals) characteristics in two sampling times (May and July) in 2021. The finding results unveiled that the water of the two rivers had temperature of 23-32^oC, DO 8-16 mg/L and COD 1.8-64 mg/L. The water pH, EC, and alkalinity were found at values of 7-8, 83-576 µS/cm, and 48-174 mg-CaCO₃/L ranges, respectively. In contrast, the amount of TDS in the both rivers were 53-369 mg/L. The detected dominant cations were Na⁺, Ca²⁺ and Mg²⁺ and their concentration was in a concentration range of 0.5-34 mg/L, while main anions were F^-, Cl^- and SO₄^2- (3-9 mg/L). The particulate matter content in the water in the form of TSS (67-372 mg/L) were observed. The presence of both TDS and TSS might lead to the water turbidity of as low as 5 NTU or as high as 200 NTU. The investigated heavy metal concentration was typically low. Based on the findings, the water quality of the two rivers at the time of investigation was not beyond the Lao national environmental quality criteria.