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ASSESSMENT OF HEAVY METAL CONCENTRATIONS IN GROUND WATER IN CRITICAL AREAS OF VISAKHAPATNAM CITY, AP, INDIA

Presence of heavy metal concentration in the ground water may cause health problems during intake of through different ways. Present study focused on heavy metal concentration of ground water in the sub-urban areas of Visakhapatnam City, AP, India. Most of heavy metals i.e., Aluminum (Al), Chromium (Cr), Manganese (Mn), Iron (Fe), Nickel (Ni), Zinc (Zn), Arsenic (As), Cadmium (Cd), Mercury (Hg) and Lead (Pb) were analyzed using Inductive Coupled Plasma Mass Spectroscopy (ICP-MS). Mean values of Zn (1.845) > Mn (1.203) > Fe (0.664) > Al (0.334) > Pb (0.245) > Ni (0.082) > Cr (0.066) > As (0.028) > Cd (0.012) > Hg (0.010) results respectively. Results shows that all heavy metal concentrations were exceeded the water quality permissible limit and this area were not suitable for domestic purpose and use before proper treatment.


Introduction
Ground water is the major source of drinking water in both urban and rural areas (Saravanakumar and Ranjith Kumar, 2011). It is the most importantsource of water supply for drinking and irrigation purposes in rural areas. Ground water quality plays animportant role in groundwater protection and quality conservation. Hence it is very important to assess theground water quality not only for its present use but also from the view point of a potential source of water forfuture consumption (Kori et al., 2006). Water sources available for drinking and other domestic purpose must possess highdegree of purity, free from chemical contamination and micro-organism (Borul and Banmeru, 2012). The people of Visakhapatnam useswell, bore wells and municipal water for their daily activities and also for drinking purposes. Water resources arepoorly managed in rural areas. The good quality water supply to such citizens is basic need. Agriculturalwaste, domestic and community solid liquid waste further deteriorate the ground water quality.
The study area is located between latitude-17°30′15″ to 18°11′15″ North and longitude-82°57′37″ to 83°28′12″ East. Visakhapatnam has been notified as one of the most polluted industrial cluster by central pollution control board of India. The study area experiences a semi-arid climate, with temperature in the range of 15 -38°C. The annual average rainfall is 1080 mm. The sub-surface geology indicates that the average weathered rock portion extends up to 16m and the fractured rock zone up to 30m depth from the ground surface. The red sediments vary in depth from 1 to 3m, with an average of about 2m, from surface level, depending upon the topography. Rainfall is the main natural replenishable recharge source of groundwater. The depth to groundwater level ranges from 2 to 11m Below Ground Level (BGL). Shallow groundwater level less than 3m BGL was observed at topographic-lows (downstream), while deep groundwater level more than 9m BGL was found at elevated ground (upstream; Figure 1). The general slope of the area was towards the salt marsh land from all the directions. Hence, the direction of the groundwater flow followed the topography of the area. Water samples were drawn from bore wells, hand pumps and Visakhapatnam during monsoon period. Samples were collected during months of mid-June to Mid-September, 2017 from the selected sites. Borosilicate glass wares, distilled water and standard reagents were used throughout the analysis. The study includes collection of data on pollution backdrop of the area and collection of ground water samples during summer season of 2016. Twenty five tube well water samples were collected covering the southern industrial part of the study area for the subsequent laboratory analysis, for heavy metals like such as aluminium (Al), chromium (Cr), manganese (Mn), nickel (Ni),zinc (Zn), arsenic (As),cadmium (Cd),mercury (Hg), and lead (Pb) Using suprapure®nitric acid, MIBK and APDC analytical grade chemicals the solvent extraction procedure was performed in the pollution testing laboratory in school of environmental sciences, Andhra university, all the sample extracts were subjected to ICPMS analysis at center for studies on Bay of Bengal, Andhra University.  In the present study, the concentration of aluminum is ranges from 0.105 -0.957 ppm with mean of 0.334 ppm (shown in table. 1). Maximum value recorded at Paradesipalem (0.957ppm) while minimum values were recorded at Aganampudi (0.105ppm). About half of the samples exceeded the permissible level of 0.2ppm (BIS) the results indicated that there was an environmental impact on the ground water of these areas due to industrialization and solid waste dumping where the values were higher. Aluminium salts generally form complexes with phosphate and are excreted in the faeces (Thienes and Haley, 1972).

Results
In the present study, the concentration of chromium is ranges from 0.003 -0.385 ppm with mean of 0.066 ppm (shown in table.1). Maximum value at Boravanipalem (0.385ppm) while minimum at Vepagunta (0.003ppm) but Maximum contamination level ofchromium in ground water is 0.05ppm/L according to BIS. Because of the low solubility of chromium, generally the levels found in water are usually low (< 5 µg/L). There is a wide variation in the Cr (VI) contents in groundwater samples throughout the study area and the toxicity is depends on its physico-chemical shape; hexavalent salts are considered the most dangerous (Lauwerys, 1992).
The concentration of manganese is ranges from 0.007 -6.452 ppm with mean of 1. Cadmium is usually present in all soils and rocks. In the present study, the concentration of cadmium ranges from 0.00 -0.133 ppm with mean of 0.012 ppm (shown in table.1). Maximum concentrations of cadmium were recorded at Kapuluppadda (0.133ppm) while lowest concentrations recorded at Aganampudi (0.00ppm) and acceptable level is 0.003ppm (BIS, 1991). Chronic exposure to low doses of cadmium causes damage to the renal tubules, followed by proteinuria, pulmonary lesions and arterial hypertension (Bertouille, 1978).
In the present study, the concentration of mercury ranges from 0.002 -0.047 ppm with mean of 0.010 ppm (shown in Lead pipes also contribute dissolved lead to the water flowing through them (Lopez desa, 1989; Murrell, 1985;Wagner 1987). In the present study, the concentration of lead ranged from 0.024 -0.918 ppm with mean of 0.254 ppm (shown in table.1). Maximum concentrations of lead were recorded atBoravanipalem (0.918ppm) while lowest concentrations were recorded at Visalakshinagar (0.024ppm).The maximum acceptable level of lead is 0.001ppm(BIS, 1991). Lead also passes the blood brain barrier, although the brain does not accumulate lead (WHO 1980).

Conclusions and Recommendations
As the demand for water is increasing rapidly with the resources staying the same there is a huge rift in the demand-supply dynamics of water. As the surface water resources are becoming scarcer we are relying more and more on groundwater to meet our ever-increasing needs. The prominence and importance of water as an asset has been growing rapidly and the proper management of water is the most important necessity now. Drinking water standards with respect to heavy metals revealed that the Aluminum (Al) concentrations were high in all the sampling locations except Paradesipalem. The results indicate that there is an environmental impact on the ground water of these areas due to industrialization and solid waste dumping where the values were higher. Chromium concentrations were high only in Mindi followed by Boravanipalem, Steel Plant, Maridi, Rusikonda, Sriharipuram, Kurmannapalem and Paravada while remaining sampling locations indicated Cr within the permissible limit of drinking water standards.
Manganese concentrations similarly showed excess in Mindi, Steel Plant, Rusikonda, Sriharipuram, Kurmannapalem, Parawada and Pandurangapuram while remaining sampling locations indicated permissible limit. Iron concentrations were highest in Mindi followed by