Patterns of soil contamination, erosion and river loading of metals in a gold mining region of northern Mongolia

Abstract

Mining has become one of the main causes of increased heavy metal loading of river systems throughout the world. There is however an evident gap between assessments of soil contamination and metal release at the mined sites and estimates of river pollution. The present work focuses on Zaamar Goldfield, which is one of the largest placer gold mines in the world, located along the Tuul River, Mongolia, which ultimately drains into Lake Baikal, Russia. It combines field observations in the river basin with soil erosion modelling and aims at quantifying the contribution from natural erosion of metal-rich soil to observed increases in mass flows of metals along the Tuul River. Results show that the sediment delivery from the mining area to the Tuul River is considerably higher than the possible contribution from natural soil erosion. This is primarily due to excessive mining-related water use creating turbid wastewaters, disturbed filtering functions of deposition areas (natural sediment traps) close to the river and disturbances from infrastructures such as roads. Furthermore, relative to background levels, soils within Zaamar Goldfield contained elevated concentrations of As, Sr, Mn,V, Ni, Cu and Cr. The enhanced soil loss caused by mining-related activities can also explain observed, considerable increases in mass flows of metals in the Tuul River. The present example from Tuul River may provide useful new insights regarding the erosion and geomorphic evolution of mined areas, as well as the associated delivery of metals into stream networks.

Sedimentation patterns in the Selenga River delta under changing hydroclimatic conditions

“…Water stream velocity and discharge measurements in 2014 were collected using propeller‐type velocity current meters deployed from boats. Associated discharge conditions were estimated using a trapezoidal rule described by Jarsjö et al (). The water surface velocity measurements in 2016 were collected using the float method, whereby data were corrected (a factor φ = 0.91) for sand‐bed channels to estimate depth‐average velocities (Gutry‐Korycka & Werner‐Więckowska, ).…”

“…One exception is the herein studied Selenga River basin that drains into Lake Baikal (Russia). Despite the absence of dams, this system is impacted by mining activities, which locally increase soil loss from the basin that leads to significant sediment and metal contamination of the tributary streams (Jarsjö, Chalov, Pietroń, Alekseenko, & Thorslund, ; Pietroń, Chalov, Chalova, Alekseenko, & A., Jarsjö J., ; Pietroń, Jarsjö, Romanchenko, & Chalov, ; Thorslund et al, ; Thorslund, Jarsjö, Chalov, & Belozerova, ). Moreover, the Selenga River basin is currently subject to climate driven shifts in hydrology and water discharge patterns.…”

Special issue «environmental change on the Mongolian plateau: atmosphere, forests, soils and water»

“…Hydrological effects include decreasing runoff trends and desiccation of some streams (Frolova et al 2017;Moreido and Kalugin 2017) and the shrinkage of lakes across the entire plateau (Tao et al 2015;zhou et al 2019). Land cover changes in the region are related to both climate change Miao et al 2015) as well as anthropogenic impacts related to urbanization (Allington et al 2017;Fan et al 2016), livestock herding (Allington et al 2017, Sternberg 2012, mining (Batbayar et al 2019;Jarsjö et al 2017) and logging (Batkhuu et al 2011;Tsogtbaatar 2004). In vast parts of the Mongolian Plateau, forest degradation and losses (Gradel et al 2017;Juřička et al 2019a) as well as desertification of grasslands (Khodolmor et al 2013;Wei et al 2019) have modified a natural land cover.…”

“…In vast parts of the Mongolian Plateau, forest degradation and losses (Gradel et al 2017;Juřička et al 2019a) as well as desertification of grasslands (Khodolmor et al 2013;Wei et al 2019) have modified a natural land cover. The key drivers of these processes are mining, agriculture / urbanization and deforestation, which are at the same time major water users and polluters (Batbayar et al 2019;Jarsjö et al 2017;Karthe et al 2017). The above mentioned processes have also had strong effects on the soils, which are affected by anthropogenic impacts in three major ways: nutrient depletion due to intensive agriculture (Hofmann et al 2016); soil erosion due to land use change, mining and increasing livestock densities (Sasaki et al 2018;Sternberg 2012;Wei et al 2019); and soil pollution (mostly with heavy metals) due to mining, industry and coal combustion in urban areas (Jarsjö et al 2017;Kosheleva et al 2019).…”

Biogeochemical specialization of macrophytes and their role as a biofilter in the Selenga delta

“…Selenga accounts for 60% of the total river water flow and 82% of sediment load to Lake Baikal (Pietroń 2017). The anthropogenic impact on ecosystems in the Selenga River basin has increased in the recent decades, e.g., by the extraction of minerals, primarily gold, urbanization, and agricultural development, especially in the upper, Mongolian, part of the basin Jarsjö et al 2017;Malsy et al 2013). In addition, changing climatic conditions in the basin, such as increasing air temperatures (0.022ºC/year, nearly two times faster than the global average; Törnqvist et al 2014) can also significantly affect the regional ecosystems.…”