The source and fate of sediment and mercury in Hunza River basin, Northern Areas, Pakistan

Abstract

This article presents results of mercury in surface waters from Hunza River basin, Northern Areas, Pakistan. Small‐scale gold mining activities along the Hunza and Gilgit rivers are long known to be discharging mercury in the amalgamation and roasting processes. Previous studies reported high mercury concentrations in soils close to mining operations as well as serious health problems for miners. However, none of the studies have focused on the level of contamination in aqueous environments. This is the first study on the investigation of source and fate of sediment and river‐borne mercury in the Hunza River. The samples collected near gold panning sites showed higher mercury concentrations than critical levels established by the U.S. Environmental Protection Agency. The observed dissolved mercury concentrations ranged from 5.10 to 25.25 ng/l, whereas particulate‐bound mercury ranged from 4.85 to 154.62 ng/l. Particulate‐phase mercury corresponded to more than 75% of the total observed mercury concentrations for all of the sampled rivers. Thus, suspended sediments represented the major pathway of the riverine mercury transport. A mass balance calculation suggested an annual mercury flux of 48.6 g/km2 into the Hunza River basin. The samples collected from the most affected river, the Shimsal River, averaged to have 108 ng/l total mercury. This amount was close to the average soil mercury data of 151 ng/l as reported by the Pakistan Mineral Development Corporation in 2001. The dominant source of contamination was shown to be the leaching of large quantities of mercury from the mercury‐rich sediment and flood plain soil into the rivers, rather than the direct release from mining activities. Significant decrease in both dissolved and particulate‐bound mercury concentration downstream of Attabad Lake suggested that mercury is being accumulated or consumed in the lake. Although minimization or elimination of mercury loses from the mining process seems important for the well‐being of the miners, preventing the remobilization of accumulated mercury is equally important in mercury control in this region. Copyright © 2014 John Wiley & Sons, Ltd.

Artificial lake expansion amplifies mercury pollution from gold mining

“…Given the correlation between total suspended solids (TSSs) and water column total Hg concentration found in this study (P < 0.0001, r 2 = 0.62; fig. S3) and other studies (23)(24)(25), as well as the higher concentration of TSS in downstream rivers compared with the other measured water bodies (P < 0.0001; fig. S4), we expect that Hg is transported bound to sediment particles (i.e., as particulate Hg) rather than in the dissolved fraction.…”

Reflectance spectroscopy and remote sensing data for finding sulfide-bearing alteration zones and mapping geology in Gilgit-Baltistan, Pakistan

“…However, there is a great need to explore the economic potential of the region through advanced level geophysical, geochemical and spectroscopic and remote sensing techniques. The occurrence of gold particles in the Indus river and its tributaries flowing through this region (Tahirkheli 1974;Austromineral 1976Austromineral , 1978Halfpenny and Mazzucchelli 1999;Shah and Khan 2004;Ali et al 2014;Biber et al 2014) and the hydrothermally altered sulfide-bearing zones reported in various parts of the region (Sheikh et al 2014;Miandad et al 2014;Rehman et al 2015) suggest that there could be the possibility of occurrence of source rocks for precious and base metals mineralization in the region. But due to the remoteness and inaccessibility to rugged terrains in this part of the Himalayan region, we need to adopt such techniques which can scan the whole region for the differentiation of various lithological units and hydrothermally altered mineralized and un-mineralized zones.…”

Contamination Assessment and Potential Human Health Risks of Heavy Metals in Urban Soils from Grand Forks, North Dakota, USA

“…It can cause miscarriages in pregnant women, severely damage the brain and kidneys of developing fetuses and, ultimately, causing death [ 26 , 27 , 28 ]. Mercury is regarded as more toxic than other non-essential metals [ 29 , 30 ] and can cause cancer [ 31 , 32 ] and a variety of other disorders affecting the immune system, heart, kidneys, lung and liver [ 29 , 33 , 34 , 35 , 36 , 37 , 38 ]. Essential elements at high levels can also have toxic effects [ 39 ].…”