A SIAN J OURNAL OF C HEMISTRY A SIAN J OURNAL OF C HEMISTRY Spatial and Monthly Variation in Co, Zn and Cd Concentrations of Surface Water of Shatt Al-Hilla River, Babylon, Iraq

This study was focused on the spatial and monthly variation in the concentration of Co, Zn and Cd in surface water of Shatt Al-Hilla river. Fourteen sampling sites have been selected of pollution located on the both banks of Shatt Al-Hilla river. Samples were analyzed by flame atomic absorption spectrometry. Several physico-chemical properties of water samples were measured during period of study such as pH values, electric conductivity and temperature of water. Study was started from November 2011 and finished in October 2012. The concentrations of heavy metals under concern exhibit wide variation from site to site and from month to month. The pH values were ranged between 6.4 to 8.9, while electric conductivities were ranged between 819 to 1250 µS. The concentrations of Co and Zn were ranged 0.012 to 5.400 and 0.10 to 2.30 mg/L, respectively whereas Cd was detected in 0.007-1.550 mg/L range.


INTRODUCTION
The contamination of water resources by heavy metals is a serious problem that can affect the environment since some of the heavy metals are very harmful 1 . Heavy metals are among the most persistent of contaminants in the ecosystem such as biota, sediments and water, because of their resistance to decompose in natural condition. Toxicity appears after increasing the level of indispensability. Heavy metals become toxic when they are be not metabolize by the human body and accumulate in the soft tissues of this body 2 . Generally, in uninfected environment, most of the heavy metals are in very low levels and natural geological weathering of soil and rocks, directly exposed to surface waters, is usually the largest natural source. Main pollution with heavy metals by anthropogenic sources are mining, disposal of partially treated and untreated effluents contain toxic metals, as well as metal chelates from several industrial factories and indiscriminate use of fertilizer containing heavy metals. Heavy metals discharged into aquatic system by anthropogenic sources or natural during their transport are distributed between two phases: aqueous and sediments. Because of the following processes such as adsorption, hydrolysis and co-precipitation only a small portion of free metal ions stay dissolved in water while a large quantity of the metals deposited in the sediment. Although heavy metals are refractory though natural processes in the environment, they can be chemically changed by microorganisms and Spatial and Monthly Variation in Co, Zn and Cd Concentrations of Surface Water of Shatt Al-Hilla River, Babylon, Iraq convert to organic complexes, some of which may be more hazardous to aquatic animals and human life 3 . Potentially toxic heavy metals, including zinc, cadmium and others, may participate in reactions and accumulate, causing deleterious effects in aquatic organisms 4 . The maximum allowed concentrations in drinking water of heavy metals are in the ppb range (e.g., 5 ppb for Cd and 110 ppb for Co) 5 . There are over 50 heavy metals that can be classified as heavy metals, only 17 of which are considered to be very toxic and relatively accessible 1 . The heavy metals in drinking water linked most often to human poisoning are copper, cadmium, zinc, etc. They are required by the body in small concentrations, but can also be toxic in large amounts. Cadmium is extremely toxic metal even in low amounts, it has a long biological half-life in the human body and the half-life of cadmium is range from 10 to 33 years. Long term exposures to this element also induce renal damage 6 .
Recently several techniques were used to determine heavy metals in environmental samples. These techniques include inductively coupled plasma mass spectrometry (ICP-MS) 7-14 ; flame and graphite furnace atomic absorption spectrometry 15 ; inductively coupled plasma optical emission spectrometry (ICP-OES) [16][17][18][19][20][21][22][23] ; neutron activation analysis 24 , electrothermal vaporization inductively coupled plasma mass spectrometry (ETV-ICP-MS) 25 ; inductively coupled plasma emission spectrometry (ICP-ES) 26 ; flow injection solid phase extraction inductively coupled plasma mass spectrometry (FI-SPE-  27 and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) 28 . In Iraq and particularly in study area (Al-Hilla city), urban agriculture has been a normal practice along both river banks. The objective of this work is monitoring the rivers water over a long period of time in order to describe average metal pollution and its trend, which is essential component of any pollution control management.

EXPERIMENTAL
Description of study area: Shatt Al-Hilla river is one of the main sources of water in the Babylon Governorate. This river starts from Saddat Al-Hindya and finishes on the southern borders of Al-Hilla city. Study area was described in previous work 29 .
Sampling, collection of water samples and analytical methods: Water samples have been collected from fourteen sites once monthly during the study period started in November 2011 and finished in October 2012. Sampling method was mentioned in previous work 30 . The operating parameters of the atomic absorption analysis are given in Table-1.

RESULTS AND DISCUSSION
The results of the determination are presented in Tables  2-4 Table- Table-4. The higher concentration of cadmium than limits which is 0.003 ppm is very dangerous as cadmium is poisonous metal and can cause serious health problems and it has the tendency to accumulate in the body tissues that results in lung problems and kidney damage 35 . Effluents from battery industries, dyes, pigments and alloy making are the major sources of cadmium in the water. The conductivity values (Table-6) for surface water ranged 822-1250 are within the safe limit of application.
The mean pH values in Table-5 for surface water ranged between 7.815 to 8.644, increasing in the range of pH value start from the upstream to downstream of the river which refer to increase the alkalinity in down direction of the river. The observed pH of the river water was well within the safe limit values for drinking and EU as well as for crop production. The conductivity values (Table-6) for surface water ranged 822-1250 are within the safe limit of application.

Conclusion
In conclusion, Co, Zn and Cd have shown elevated levels of heavy metals at many sites along Shatt Al-Hilla river in different seasons of the study. The increased levels of heavy metals in the water lead to accumulation of them in the agricultural soils and plants grown on the contaminated soils leading to great harm to humans and animals. Hence, it is obligatory to rectify the various heavy metals resources which lead to addition of these metals into the river. Also, water should be tested systematically and regularly to keep monitoring process on the heavy metals pollutant into the water and purify the water, if necessary. Further, as the heavy metals enter the food chain and get accumulated at each levels from producers to consumers the heavy metal concentrations in soil and in various crops grown in the area is to be examined in addition to the river sediments which will affect the aquatic life in the river.