Nature of distribution of mercury in the sediments of the River Yamuna (tributary of the Ganges), India

Abstract

Suspended Particulate Matter (SPM), surface (bed sediments) and short length cores of sediments collected from the largest tributary of the river Ganges, namely the river Yamuna, were analysed for total mercury as well as its fractionation in various size and chemical sites in the sediments following standard procedures. Also, attempts were made to determine the vertical distribution in sediments in relation to the recent timescale of a few decades. Our observations indicate that the SPM in general showed higher levels of total mercury compared to the surface sediments while at places the enhancement could be by a factor of 10, say around 25 microg g(-1) in the downstream region that integrates the industrial midstream and agricultural downstream terrain near its confluence with the Ganges. Surface sediments in the upstream direction near the Himalayan foothills and SPM in the lower reaches showed significant high Index of Geoaccumulation (Igeo) as defined by Müller. Size fractionation studies indicate that the finer fraction preferentially showed higher levels of mercury while in the lower reaches of the river, the total mercury is equitably distributed among all size fractions. The proportion of the residual fraction of mercury in relation to mobile fractions, in general decreases downstream towards its confluence with the Ganges river. In sediment cores, the vertical distribution show systematic peaks of mercury indicating that addition of this toxic metal to the aquatic system is in direct proportion to the increase in various types of human activities such as thermal power plants, land use changes (urbanisation) in the midstream region and intensive fertiliser application in lower reaches of this vast river basin.

Human impacts on open ocean mercury concentrations

“…V w = volume of model compartments; A w = water surface area of each ocean basin; Q r = freshwater discharges from rivers into each ocean basin based on data from Dai and Trenberth [2002]; C ss Q r = discharge of suspended solids from rivers into oceans estimated from the average suspended sediment loads of rivers from Ludwig et al [1996]; C Hg(P) and C Hg(d) are the particulate and dissolved phase concentrations of Hg in rivers flowing into the ocean from sources listed below; k w = empirically calibrated water‐side mass transfer coefficients used to estimate evasion of Hg(0) from each basin; F Hg(0) = average fraction of Hg(0) relative to total Hg in seawater estimated from empirical data; PP = primary productivity of each ocean basin from Antoine et al [1996]; n/a = not applicable. River Hg concentrations from the following sources: North Atlantic/Antarctic, Coquery et al [1995]; Surface/Intermediate Atlantic, Maurice‐Bourgoin et al [2003] and Quemerais et al [1999]; Mediterranean, Cossa et al [1997]; Pacific/Indian, Subramanian et al [2003], Tariq et al [1996], and Woitke et al [2003]; North Pacific, Han et al [2004] and Choe et al [2003].…”

Seasonal behavior of mercury species in waters and sediments from the Negro River Basin, Amazon, Brazil

“…5 In waters and sediments, mercury can be transformed into methylmercury under both biotic and abiotic conditions. [17][18][19][20][21][22] Methylmercury concentrations in water rarely exceed 10% the mercury amount, while in sediments this value is lower, 19,[23][24][25] ranging from 0.1 to 2 %. Methylmercury is a species of particular interest because of its biomagnification in the food chain, its high toxicity, bioavailability and persistence in the environment.…”

Mercury contamination in the Red river watershed: a review of the contaminated sites

“…As suspected, they are really lower than those of the Lot River (880µg/kg, e.g. Coynel et al, 2009), the Yamuna (tributary of the Ganges River, 5000µg/kg, (Subramanian et al, 2003) …”