The pollution of Manchar Lake is serious issue, various studies has been carried out on Manchar Lake (Arain et al., 2008; Kazi et al., 2009; Arain et al., 2009; Abdul et al., 2009). We know that water is essential for sustaining the life on planet earth. This vital resource makes up more than 60% of the living organisms. Pollutant  derived  from a growing number of diverse sources (Industrial waste, urban run-off, sewage treatment plants, boating activities, agricultural fungicides, domestic garbage, dumps, anthropogenic activities and mining operations) have increasingly affected aquatic ecosystem (Garrett, 2000; Lashari et al., 2012). Heavy metals aquatic system have attracted considerable attention owing to their toxicity and accumulation in aquatic biota (Elllis 1989; Mason, 1998). The human health is directly concern to the quality of water, sanitation and hygiene. Water required for human consumption must be free from concentration of chemical substances that may be health hazards; as water is highly prone to contamination by bacteria, viruses, protozoa, pathogens, helminthes parasite, and toxic organic, inorganic compounds (Hari et al., 1994; Miranzadeh et al., 2011). Polluted water causes various diseases in consumers such as, diarrhea, dysentery, typhoid, cholera, hepatitis etc (Waheed and Kausar, 1987). The children under the age five have been killed by waterborne diseases and it is reported that the death ratio due to unsafe water is more than all forms of violence including war worldwide annually (World health organization, 1996, 2003). Amongst the water borne diseases diarrhea is considered as one of the major killer among the children. Each year 1.8 million people die from diarrhoeal diseases, and 90% of these deaths are of children under five (World health organization, 2003; WHO/UNICEF, 2004). Moreover, each year 4 billion cases of diarrhea has been reported worldwide and results in 2.2 million deaths occurred mostly of the children under five. This shows that 15% of child deaths every year are attributable to this dreadful disease. It is reported that child is dying every 15 s because of diarrhea worldwide. In India, half million children has dying each year due to diarrhea (UNICEF, WHO, 2009).  As, in Pakistan fifty thousands three hundreds children under five year are dying due to diarrhea annually; and Pakistan is ranked sixth among fifteen countries (WHO/UNICEF, 2004). In the source of Industrialization, the quantity of heavy metals and toxic compounds are continuously released into Manchar Lake, hence, the aim of current study was to investigate the heavy metals content from Manchar lake water. 

In the study area of the Manchar lake five sampling stations was selected which includes zero points (waste entrance point into lake), near to zero point (inside the Manchar lake), mid of the Manchar, Danistar Wah (Manchar Lake) and Aral Wah (Manchar Lake) respectively. Sampling was carried out throughout the year; which includes August, 2011, November, 2011. Each sampling was carried out after the interval of three months. Water samples were collected according to the method of in pre-cleaned one liter plastic bottles of scraped caps. The sample bottle was plunged necks downwards about 15 cm below the water surface and about 60 cm from the side of local fisher man boats. The samples were stored in the laboratory at the room temperature on top of cupboards until required for use. All the analyses were conducted according to the standards of American Public Health Association (APHA, 1992). The entire chemicals and study standards solution were obtained from Sigma Fluka. 

Natural fresh water contains impurities of trace elements/heavy metals as it dissolves these substances while moving downward as a hydrological cycle (Aamir and Tahir, 2003). Metals can be lethal or harm the organism without killing it directly. Adverse effects on an organism's activity, growth, metabolism, and reproduction are examples of sub lethal effects (Wright and Pamela, 2002). These metals include lead (Pb), Cadmium (Cd), Zinc (Zn), Mercury (Hg), Arsenic (As), Silver (Ag) Chromium (Cr), Copper (Cu) Iron (Fe), and the Platinum group elements (Haijian et al., 2011). Many of these metals are considered essential for human health. Like Iron, Copper, Zinc, Nickel and other trace elements are needed for proper functioning of biological systems, but overexposure can lead to adverse health consequences (Rippey et al., 2008; Ley et al., 2011). However, deficiencies of these trace elements may lead to a number of disorders as well (Prabu, 2009). Generally heavy metal bioaccumulat during metabolic processes (Borgmann et al., 1993; Sharma and Aqrawal, 2005) and yet their biotoxic effects in human biochemistry are hugely unexplored (Duruibe et al., 2007). Their potential accumulation in biosystems and food chain has been documented. Thus a better understanding of heavy metal contamination profiles and their effect in water, soil and plant systems has attracted a lot of research interest (Prabu, 2009). In Pakistan toxic metals in both ground and surface waters, often exceed the maximum admissible concentrations recommended by WHO.

 

Cobalt

 

The result shows that maximum concentration of Cobalt was noted up to 7 µg/L in sample Station-1 in the month of August, 2011. However, at sampling Station-5 the minimum value of the cobalt was equal to 3 µg/L. The average value of the samples in the month of August noted 4.6 µg/L, whereas result obtained from the Month of November, 2011 was range as 4.5 to 9.5 µg/L. The average value in November was 7.1 µg/L (Tables 1 to 2). Cobalt content in Keenjhar Lake is Low as compare to that of Manchar Lake. Cobalt concentration were higher than that WHO/UNICEF (2004)) but our result are not in agreement with the result of Lashari et al. (2012) and Korai et al. (2008).

 

 

 

 

 

From this study it was found that lake is contaminated with trace elements including lead, cobalt, zinc, nickel, copper and chromium. The concentration of these elements was high from the standard limit of World Health Organization. The aquatic organisms were found in danger other hand local human population is also at risk because they are utilizing the water of lake without any treatment. This lake also a major source of fishing and fish cached from lake may be highly contaminated by various toxic species. Hence it is highly recommended that government should take necessary steps to save the precious fresh water lake.

The authors have not declared any conflict of interest.