The ecological complexity of the Thai-Laos Mekong River: I. Geology, seasonal variation and human impact assessment on river quality

Abstract

The objective of this study is to assess the variation of pollution in the Thai-Laos Mekong associated with seasonal dynamics concomitant with the natural geological features and human activities that impact on the adverse quality of the river. The complex ecology of the 1500 km stretch of the Thai-Laos Mekong River has been studied in this paper to understand the relationship with the geomorphology, with the sub-tropical monsoonal climate and the impact of human activity. Sub-surface geology controls the nature and extent of the drainage basin and of the river channel. The volume flow of the river varies naturally and dynamically in phase with the rainfall; traditional models based on steady state hydraulics are inappropriate. Continuous erosion of the river banks and bed generates a sediment load of impure silt, mica, quartz and clay minerals that inhibits light penetration and limits the primary productivity of the river. The river separates two countries at different stages of development; it flows through or close to eight non-industrial conurbations (Populations 350,000-2,000,000) but is otherwise sparsely populated. The river is used for subsistence agriculture, village transport, fishing including aquaculture and as a source of domestic water. Hydroelectricity is generated from the Laos tributaries. The river is a depository for partially treated urban waste and untreated village waste, hence populations of E.coli bacteria sometimes render the water unsuitable for drinking unless treated with the highest value of 240/100 ml found at station 7 during the summer season of 2003. Furthermore the river is polluted by trace metals, notably cadmium and mercury, and by Polycyclic Aromatic Hydrocarbons (PAHs), which are particularly concentrated in the sediments. Previous work has shown that cadmium and mercury exceed the Probable Effect Level (PEL) values of Canadian Environmental Quality Guidelines and that the PAH concentrations were also greater than the Interim Sediment Quality Guidelines (ISQG). Consequently the fish stock, a vital source of protein for the local human population maybe seriously affected. As conflict between the demands of human activities will be exacerbated by the continuing development of the basin; monitoring must be continued and a better model of the river's ecology is needed to predict the impact of development.

Functional expressions of adenosine triphosphate‐binding cassette transporters during the development of zebrafish embryos and their effects on the detoxification of cadmium chloride and β‐naphthoflavone

“…In addition, we could not rule out the possibility of involvement of other transporters such as BCRP or other members of Mrps and Pgp. More importantly, aquatic organisms are constantly exposed to complex mixtures of chemicals (Udomchoke et al ., ; Velinsky et al ., ), and various environmental pollutants, including pesticides, fragrances, pharmaceuticals and PAHs may inhibit ABC transporter activity and enhance their deleterious effects in exposed cells and organisms (Epel et al ., ; Faria et al ., ). Thus, it is important to find out whether powerful transporter inhibitors, also called chemosensitizers, exist in the environment.…”

Individual and joint toxic effects of cadmium sulfate and α-naphthoflavone on the development of zebrafish embryo

“…Aquatic organisms that inhabit environments are often contaminated with high levels of heavy metals and PAHs together (Terry and Stone, 2002;Udomchoke et al, 2010). However, studies on the joint effects of these pollutants are still rare.…”

Land use/land cover changes in the period of 2015–2020 in AngYai Village, Sikhottabong District, Vientiane Capital, Lao PDR

“…The Mekong River flows through the study area, providing self-sufficiency in agriculture, village transport, and fishing, and a source of domestic water. Hydroelectricity was generated from the tributaries of the river (Udomchoke et al 2010). In addition, artificial ponds were created to store water for agricultural purposes in the dry season.…”