Arsenic sources and its mobilization in upper and central gangetic plain regions of India

Transcription

1 Arsenic sources and its mobilization in upper and central gangetic plain regions of India AL. Ramanathan, Shailesh Kumar Yadav Sc h o o l o f E n v ir o n me n t al Sc ie nc e s, JNU, Ne w De lhi, India

2 Worldwide Groundwater status Groundwater is more vulnerable than surface water. Sources: Foster, S., Chilton, J., Nijsten, G. J., & Richts, A. (2013). Groundwater a global focus on the local resource. Current Opinion in Environmental Sustainability, 5(6), Various threats to surface and subsurface water Natural Contaminants such as As, U, Trace metals, Anions and Cations. Air Pollution deposition on surface Uncontrolled Hazardous wastes. Chemical and Road Salts Uses of Pesticides and Fungicides Fertilizers and Manure Storage and Application Septic Tanks Landfills Storm Water Unused well Waste Water injection Overexploitation

3 Arsenic Contamination Scenario Bangladesh, India, China Taiwan, Myanmar, Nepal, and Vietnam, Cambodia, Pakistan, Myanmar, Argentina, Chile, Mexico, Southwest United States, Hungary, Romania. According to Ministry of water resources, 10 states West Bengal, Bihar, Uttar Pradesh, Assam, Manipur, Jharkhand, Chhattisgarh, Punjab, Haryana, Karnataka and Manipur reported elevated level of As (>50 ppb).

4 Some geomorphic features of the Southern and Northern part of the Ganga River studied by JNU team Gorakhpur Bhagalpur, Bihar Ponds Buxar, Bhojpur, Bihar Bihar Fig. Area map of studies done by JNU group, Red dots shows on the Southern part of the Ganga river while blue shows Northern. Km

5 Study area: Ghazipur, Uttar Pradesh The triggering factors of arsenic mobilization in shallow ground water is mainly anthropogenic activities like fertilizers use in the agriculture practices Map showing the study area around Ghazipur in eastern Uttar Pradesh, India with the sampling locations. (Kumar et al. 2010)

6 As showed poor correlation between As (tot) vs NO 3- and As (tot) vs Fe, less anthropogenic contribution and Fe precipitation may be the reason A scatter plot between As (μgl - ) to NO 3 (mgl - ) in Ghazipur groundwater Relation of As (μg/l) to Fe (mg/l) in Ghazipur groundwater (Kumar et al. 2010).

7 As in groundwater shows strong depth dependency till m below the ground surface and decreases rapidly below ~40 m Variation of As (μg/l) with Depth (m) in groundwater of Ghazipur District (Kumar et al. 2010)

8 Study area: Bhagalpur, Bihar The heterogeneous distributions of arsenic (elemental signature) governed by redox reactions at shallow depth which support the dissolution of arsenic from arseniferous iron oxyhydroxides General geomorphology of the Bhagalpur district, including sampling locations (Kumar P. et al. 2010). Maximum As concentration was observed at a depth of 20 to 40 m where the active terminal electron accepting processes (TEAPs) perhaps driving the As mobilization (Bhattacharya et al., 2002)

9 Depiction of the spatial distribution of arsenic concentration (µg L -1 )in the premonsoon season by contouring Contour map of arsenic concentration (µg L 1- ) in the post-monsoon season (Kumar et al. 2010)

10 Study area: Bhojpur, Bihar Table: Metal enrichment in Semria Ojhapatti Village, Bhojpur District, Bihar Map of study area Semria Ojhapatti Village, Bhojpur District, Bihar Intense metal enrichment in the aquifer observed due to heavy enrichment ability at certain depths with changing redox conditions (Kumar A. et al. 2012)

11 Due to high organic matter and fine grain size of sediments showed high metal concentration in 10m. In Samaria Ojhapatti, Bhojpur, Bihar Variation of metals concentration (in mg kg -1 ) with depth (Kumar A. et al. 2012)

12 Study area: Buxar, Bihar Study area showing Buxer district of Bihar, India Chakani Village (Buxar, Bihar) A Arsenic Hot spot along a abounded channel of Ganga, where depth ranging from 40fts-170fts have Arsenic concentration up-to 1000 ppb. Arsenic in groundwater above WHO Standard (>10ppb) area alternated with several As free and few As Hot spot Zones (Unpublished)

13 Study area: Samastipur, Bihar Two core has been collected utilizing the hand-flapper drilling method. The depth of the Core 1 was 46.2m from Methrapur (Dal Singh Sarai) However, Core 2 collected from Haral Chapar which is 33.5m deep. Kumar et al., 2016

14 Total and inorganic As in subsurface sediment: On the basis sediment color tools On the basis of texture and lithology, the sediment was categorized into five distinct lithofacies for both cores. A modified Munsell Color Chart which was reduced into a four color tool. Kumar et al., 2016

15 Core 1. Methrapur (Dal Singh Sarai) Kumar et al., 2016

16 Core 2. Haral Chapar Kumar et al., 2016