Heavy Metal Contamination of Ganga River at Varanasi in Relation to Atmospheric Deposition

Tropical Ecology 51(2S): 365-373, 2010 ISSN 0564-3295 © International Society for Tropical Ecology www.tropecol.com Heavy metal contamination of Ganga river at Varanasi in relation to atmospheric deposition J. PANDEY*, K. SHUBHASHISH & RICHA PANDEY Centre of Advanced Study in Botany, Banaras Hindu University, Varanasi 221 005, India Abstract: We investigated the mid stream water quality of Ganga river as influenced by aerially - driven heavy metals at Varanasi, India. Twelve sampling stations were selected along a 20 km long stretch of the river. Mid stream sub-surface water samples collected at fortnightly intervals from all the sites were acid digested and analyzed for Cd, Cr, Cu, Ni, Pb and Zn. The data revealed that the mid-stream water of river Ganga at Varanasi is invariably contaminated by heavy metals. Highest concentrations of Cd, Cr, Cu, Ni and Pb were recorded during winter and that of Zn during summer season. The overall concentration of heavy metals in water showed the trend : Zn > Ni > Cr > Pb > Cu > Cd. Concentrations of all the heavy metals were high in down - stream sampling stations. Correlation analysis showed that heavy metal concentration in mid-stream water had significant positive relationship with rate of atmospheric deposition at respective sites. Although the concentrations of these metals in water remained below the permissible limits of Indian standards for drinking water, levels of Cd, Ni and Pb at three stations, were above the internationally recommended (WHO) maximum admissible concentrations (MAC). These observations suggest that use of such water for drinking may lead to potential health risk in long-run. The study has further relevance in understanding the atmosphere - water interaction in polluted environment and for management of water bodies even those situated away from direct anthropogenic discharge. Resumen: Investigamos la calidad del agua de la corriente media del río Ganges en relación con los metales pesados transportados por aire en Varanasi, India. Se seleccionaron doce estaciones de muestreo sobre una sección del río de 20 km de largo. Las muestras de agua sub-superficial del centro de la corriente recolectadas quincenalmente en todos los sitios fueron sometidas a digestión ácida para analizar su contenido de Cd, Cr, Cu, Ni, Pb y Zn. Los datos revelaron que el agua de la corriente media del río Ganges en Varanasi está invariablemente contaminada por metales pesados. Las concentraciones más altas de Cd, Cr, Cu, Ni y Pb fueron registradas durante el invierno y la de Zn durante el verano. Las concentraciones generales de metales pesados en el agua mostraron la tendencia Zn > Ni > Cr > Pb > Cu > Cd. Las concentraciones de todos los metales pesados fueron altas en las estaciones de muestreo ubicadas corriente abajo. Un análisis de correlación mostró que la concentración de metales pesados en el agua de la corriente media tuvo una relación positiva significativa con la tasa de deposición atmosférica en los sitios respectivos. Si bien las concentraciones de estos metales en el agua permanecieron debajo de los límites permisibles de los estándares para el agua potable en la India, los niveles de Cd, Ni y Pb en tres estaciones superaron las concentraciones máximas admisibles (CMA) recomendadas internacionalmente (OMS). Estas observaciones sugieren que el uso de esta agua para consumo humano puede conducir a riesgos potenciales de salud a largo plazo. El estudio tiene además relevancia para el entendimiento de la interacción atmósfera - agua en un ambiente contaminado y para el manejo de cuerpos de agua, incluso de aquellos que se sitúan lejos de descargas antropogénicas directas. Resumo: Investigámos a influência dos metais pesados transportados pelo ar na qualidade do caudal da água do rio Ganga em Varanasi, Índia. Doze estações amostra foram seleccionadas N * Corresponding Author; e-mail: [email protected] 366 ATMOSPHERIC DEPOSITION AND WATER POLLUTION ao longo de 20 km do percurso do rio. As amostras de água da sub-superfície da corrente do rio foram colhidas quinzenalmente de todas as estações, foram digeridas em meio ácido e analisadas em relação ao Cd, Cr, Cu, Ni, Pb e Zn. Os dados revelaram que as águas da corrente do rio Ganga, em Varanasi, estavam invariavelmente contaminadas por metais pesados. As concentrações mais elevadas de Cd, Cr, Cu, Ni e Pb foram registadas durante o inverno enquanto no verão era o Zn. A concentração global em metais pesados na água mostrou a seguinte tendência: Zn > Ni > Cr > Pb > Cu > Cd. As concentrações de todos os metais pesados eram mais elevadas nas estações amostra mais a jusante. A análise de correlação mostrou que a concentração em metais pesados na corrente apresentava uma relação positiva com a taxa de deposição atmosférica nas respectivas estações. Embora as concentrações neste metais pesados na água se encontre abaixo dos limites permissíveis pelos standards indianos para a água de beber, os níveis de Cd, Ni e Pb em três estações, encontravam-se acima dos níveis internacionalmente recomendados (OMS) para as concentrações máximas admissíveis (CMA). Estas observações sugerem que o uso desta água para beber pode conduzir a longo prazo a potencias riscos para a saúde. O estudo tem, ainda, relevância para a compreensão da inter-acção atmosfera - água em ambientes poluídos e para a gestão das massas de água, mesmo daquelas distantes das descargas antropogénicas directas. Key words: Aerial catchment, atmospheric deposition, contamination, Ganga river, heavy metals, pollution. Introduction implications including carcinogenesis induced tumor promotion (Schwartz 1994). The growing cons- Atmospheric depositions of heavy metals have ciousness about the health risks associated with dramatically altered the biogeochemical cycles of environmental chemicals has brought a major shift these elements (Azimi et al. 2003; Friedland & in global concern towards prevention of heavy metal Miller 1999). The impact of long - distance atmos- accumulation in soil, water and vegetables. Atmos- pheric transport of pollutant aerosols on terrestrial pherically driven heavy metals have been shown to environment is well documented, but the impact of significantly contaminate soil and vegetables aerially driven pollutant aerosols on inland water causing a serious risk to human health when plant bodies has received attention only recently (Pan- based foodstuffs are consumed (Pandey & Pandey dey & Pandey 2009a; Thornton & Dise 1998). In 2009b, 2009c; Voutsa et al. 1996). Dietary intake of India, the data so far available on these lines have trace elements depends also on irrigational water been mainly confined to acidic depositions (Kumar use. There may not always be a strong relationship et al. 2001). Less attention has been paid towards between the concentrations of trace elements in atmospheric deposition - linked heavy metal conta- soil and plants (Siegel 2002), but there always mination of freshwater bodies, especially rivers. exists a strong relationship between their During recent years, anthropogenic activities have concentrations in irrigational water and plants dramatically increased the atmospheric deposition (Ahmad & Goni 2009; Sharma et al. 2006). Thus, of pollutant elements even in areas far away from the deposition of heavy metals in water bodies can direct human influence (Pandey & Pandey 2005, doubly increase the human intake through food 2009a). Although the atmospheric deposition of po- chain as well as through drinking water. Most of llutant aerosols is of global concern, this problem the surface discharge sources contaminate soil and is rapidly increasing in developing countries inc- water bodies under limited spatial range, aerial luding India due to continued population pressure emissions being prone to long range transport, coupled with accelerated urban - industrial growth contaminate wider range of ecosystems especially and lack of efficient control measures (Borbely - down wind to emission sources. Furthermore, unlike Kiss et al. 1999; Pandey & Pandey 2009b; Singh & surface discharge, where stream flow restricts mid Agrawal 2005). stream contamination, atmospheric deposition dir- Heavy metals are known to have serious health ectly adds contaminants on water surfaces. PANDEY, SHUBHASHISH & PANDEY 367 The present study was an attempt to investi- different sampling sites is presented in Table 1. gate the relationship between the concentrations The bulk atmospheric deposition was collected of heavy metals in mid stream Ganga water and using bulk samplers which combine the precipi- their input through atmospheric deposition at tation and dry fallout in the same container. These Varanasi. The River Ganga rises in the Gangotri collection systems were maintained at a height of 2 glacier in the Himalaya Mountains at an elevation m to avoid collection of re - suspended soil parti- of 7138 m above mean sea level. It enters the culates and were devised to avoid bird nesting as plains at Hardwar and meanders over a distance described in Pandey & Pandey (2009b). The bulk of above 2290 km across UP, Bihar and West collectors were replaced by clean ones at fort- Bengal, and receives a wide array of chemical nightly intervals. As soon as the samples were constituents including toxicants from a variety of brought to the laboratory, they were acidified with natural and anthropogenic sources (Kar et al. HNO3 (Merck), filtered and stored in dark at 2008). Earlier studies have indicated urban sewage ambient temperature before analysis. and industrial

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