Regional patterns of heavy metal exposure and contamination in the fish fauna of the Kharaa River basin (Mongolia)

Abstract

Past and present gold mining operations scattered throughout the Kharaa River basin, Mongolia, have been identified as a major source of heavy metal and metalloid contamination. However, the potential accumulation of toxic contaminates including Cr, Zn, As, Cd, Hg, Cu, Ni and Pb in the resident fish fauna and the subsequent human health risks associated with their consumption have previously not been quantified. In the current study, contaminates in water, sediment and five consumed fish species (Leuciscus baicalensis, Thymallus baicalensis, Brachymystax lenok, Lota lota and Silurus asotus) were examined. The results indicated that concentrations of As and Hg exceeded the national permissible limits for drinking water in the Gatsuurt tributary of 10 lg L -1 and 0.05 lg L -1 respectively, while Hg contents detected in the sediment of the Boroo tributary were highly elevated (0.78 lg g -1 ). Heavy metal and arsenic accumulation was evident in all five fish species sampled across the basin, with maximum muscle contents of Cr, As, Hg and Pb detected in several species caught in the middle and lower river reaches, while Zn was highly elevated in B. lenok collected in the upper tributaries. Elevated median contents of Cr, Cu, Hg and Pb increased with trophic level, with Hg accumulation posing the greatest threat to humans as 10.7 % of all fish sampled in the study exceeded the internationally recommended threshold for Hg in consumable fish tissue. Although recreational fishing is rapidly growing throughout Mongolia, the overall level of fish capture and consumption remains relatively low. However, increasing pollution and accumulation in resident fish species could lead to chronic heavy metal intoxication in people who consume them regularly from the most polluted regions of the basin, while additionally being exposed to other sources of contamination.

Environmental change in the Selenga River—Lake Baikal Basin

“…The results of the various international research programs such as the Russian Geographical Society project "Expedition Selenga-Baikal", UNDP-GEF project "Integrated Natural Resource Management in the Baikal Basin Transboundary Ecosystem", and the German BMBF-funded Thematically, the manuscripts consider hydrological changes and their drivers, pollutant and sediment input, transport and deposition and their role for the aquatic ecosystem of the Selenga, its tributaries and its delta. The spatial focus of the manuscripts ranges from basinwide studies (Malsy et al 2016;Frolova et al 2017) to specific subregions such as the Selenga's headwaters (Kopp et al 2016;Kaus et al 2016;Thorslund et al 2012) or its delta (Chalov et al 2016) ( Table 1). These studies provide an important contribution for a better understanding of spatial and temporal processes regarding hydrology, sediment and pollutant fluxes and aquatic ecology in the Selenga River-Lake Baikal Basin, adding novel insights into this unique ecosystem as compared to previous reports in literature (Table 1).…”

“…Snapshot field measurements of heavy metals in water and sediments (Thorslund et al 2012) and fish communities (Kaus et al 2016) were conducted to assess river system change (Brumbaugh et al 2013) Sediment transport (Chalov et al 2015), heavy metal fluxes (Lychagin et al 2017) Annual average flow, annual maximum hourly flows and annual minimum 30-day flows (Frolova et al 2017) Water quality parameters (Malsy et al 2016) Selenga river tributaries/subcatchment Heavy metal and arsenic accumulation in five fish species (Kaus et al 2016) Stormflow and decreasing low-flow condition headwaters (Kopp et al 2016) Sediment budget in the Kharaa River basin (Theuring et al 2015) n/a Local hot spots (Tuul and Sharyngol rivers)…”

“…The study also focused on the importance of predicting potential future changes in the bioavailable dissolved fractions under changing ambient conditions from a health risk perspective. Kaus et al (2016) examined the spatial pattern of heavy metal contamination in fish in the meso-scale Kharaa river basin, which is located in the central part of the Selenga-Baikal basin. The authors reported heavy metal and arsenic accumulation in five fish species sampled, particularly in the middle and lower reaches of the river.…”

“…Currently, there are different views regarding their impact on Lake Baikal itself (Chebykin et al 2010;Pavlov et al 2008). However, bioaccumulation and toxicological effects observed in aquatic biota ranging from insects to fish provide indication that water quality deterioration in the Selenga river system does have an ecological impact (Avlyush 2011;Kaus et al 2016;Komov et al 2014).…”

Seasonal home range shifts of the Siberian taimen (Hucho taimenPallas 1773): Evidence from passive acoustic telemetry in the Onon River and Balj tributary (Amur River basin, Mongolia)

“…Along with habitat loss (Hartwig and Borchardt, 2014;Hartwig et al, 2016), water pollution (Stubblefield et al, 2005;Hofmann et al, 2010Hofmann et al, , 2011Thorslund et al, 2012;Pfeiffer et al, 2014;Nadmitov et al, 2015;Kaus et al, 2016), water abstraction (Karthe et al, 2015a) and climate change (Menzel et al, 2011;Karthe et al, 2013;Malsy et al, 2016), the primary threat facing many resident fish populations is their intentional mortality resulting from rapidly growing recreational fishing activities by both local and foreign fishers Ocock et al, 2006;Vander Zanden et al, 2007). Along with habitat loss (Hartwig and Borchardt, 2014;Hartwig et al, 2016), water pollution (Stubblefield et al, 2005;Hofmann et al, 2010Hofmann et al, , 2011Thorslund et al, 2012;Pfeiffer et al, 2014;Nadmitov et al, 2015;Kaus et al, 2016), water abstraction (Karthe et al, 2015a) and climate change (Menzel et al, 2011;Karthe et al, 2013;Malsy et al, 2016), the primary threat facing many resident fish populations is their intentional mortality resulting from rapidly growing recreational fishing activities by both local and foreign fishers Ocock et al, 2006;Vander Zanden et al, 2007).…”