ASSESSMENT OF HEAVY METALS CONTAMINATION AND SEDIMENT QUALITY IN SHATT AL-ARAB RIVER, S IRAQ

In Shatt Al-Arab river, there is high concentration of population, industries, domestic sewage, and industrial effluents with high organic matter discharged untreated, in addition to oil spilling accidents caused to dump a lot of heavy metals cause to health risk for people that live in Basrah city. Concentrations of six heavy metals (Cr, Cu, Ni, Pb, Mo, and Zn) of the sediments in Shatt Al-Arab river were detected in this study to evaluate their level in five selected sites in Shatt Al-Arab river, Site 1 in Maaqal port, site 2 in Basrah center, Site 3 in Abu Flus port, Site 4 in Seeba area in Abu AlKhassib, and Site 5 in Fao area. The range of the measured concentrations in the studied sediments are as follows: 170 – 491 mg/l for Cr, 31 – 40 mg/l for Cu, 99.7 – 116 mg/l for Ni, 11 – 17 mg/l for Pb, 2 – 7.96 mg/l for Mo, and 108 – 127 mg/l for Zn. arrange of heavy metals from higher to lower mean content of this area as : Cr > Zn > Ni > Cu > Pb > Mo. Correlation coefficient between heavy metals could be indicate to same source area. To assess metal contamination of sediments, contamination factor (CF) was applied. The CF for Cr in sites 1 and 2 was very high contamination, while it was considerable contamination in site 3 for Cr, and sites 1 and 2 for Mo. CF for Ni, Zn , and Cu was moderate contamination, and the same degree of contamination for Mo in sites 3, 4 and 5. CF for Pb was low contamination in the most studied sites. Maximum degree of contamination was found in sites 1 and 2 as indicator to higher contamination in these areas. Sediments are enriched for metals in the following order: Cr > Mo > Ni > Zn > Cu > Pb. US environmental Protection Agency’s (USEPA) Guidelines and contaminant limits of heavy metals according to the environmental management (C.F.M) were also applied and evaluated by comparison with studied heavy metals and showed that concentrations of Cr, Ni, Mo, Zn and Cu were heavily to moderately polluted, while all the selected sites were un polluted by Pb element.


INTRODUCTION
Sediment chemistry data represent a fundamental element of sediment quality assessments that are focused on evaluation of the effects of toxic and bioaccumulative substances.Therefore, sediment chemistry is routinely selected as one of the key ecosystem health indicators in most sediment quality investigations.Heavy metals are elements having specific gravity great than 4.0 that is, at least 5 times than the water.
Metals and metal compounds are natural constituents of all ecosystems, moving between atmosphere, hydrosphere, lithosphere, and biosphere (Bargagli, 2000), it is widely accepted that heavy metal contamination in sediment, soil, and groundwater is one of the largest threats to environmental and human health (Salomons and Forstner, 1984).Toxic compounds including metals tend to accumulate in sediments of water bodies through complex physical and chemical adsorption mechanisms which depend on the nature of the sediment matrix and the properties of adsorbed compounds (Raulinaitis et al., 2012).Heavy metals exist in water, in colloidal, particulate and dissolve forms (Adepoju-Bello et al., 2009).Two main sources of heavy metals in soils can be condensed by the natural pedo-geochemical background, which represents the heavy metals concentration inherited from the parent rock, second source is anthropogenic contamination which be directed via wastes, a mind manure, compost, sewage sludge, diffuse via aerosol deposition, harbor channel dredging (Parizanganeh et al., 2012).Some of the metals such as calcium, magnesium, potassium and sodium are essential to sustaining life and must be present for normal body functions.While others such as cobalt, copper, iron, manganese, molybdenum and zinc are needed at low levels as catalyst for enzyme activities (Adepoju-Bello et al., 2009).Excess exposure to these essential metals can however, be toxic.Water has unique chemical properties due to its polarity and hydrogen bonds which makes it is able to dissolve, absorb, adsorb or suspend many different compounds (WHO, 2007).Heavy metals contamination of soils is widespread and there is a risk of transfer of toxic and available metals to human, animals, and agriculture crops (Gaetke and Chow, 2003).Sediments represent significant sources of heavy metals pollution in the aquatic environment as a result of change in pH, Eh, diagenesis or physical perturbation within their primary sedimentary sinks (Raulinaitis et al., 2012).The negative impacts of the industry on the ecological systems cannot be over emphasized due to the released waste which is mostly heavy metals into the environment long-term effects of industrial pollution on the environment may be disastrous for not only people but for all living organisms if not carefully controlled.Sediments near urban areas common by contain high level of contamination which constitute a major environmental problem faced by many anthropoginically impacted aquatic environment (Magalhaes et al., 2007).Many of industries and hospitals have set up in and around the Basrah city during the last decades, and the sewage lines that flowed directly in Shatt Al-Arab river without any treatment may dump huge volumes of toxic wastes which contain lots of heavy metal into it day and night.Heavy metals contamination in aquatic environment is critical concern, due to toxicity of metals and their accumulation in aquatic habitats (Saha and hossain, 2011).
These metals are non-biodegradation and they persist in the environment and may become concentration in the food chain (Eja et al., 2003).Many of contamination studies achieved in Basrah city, such as study of Mustafa (1985) mentioned that Cd, Cu, Ni, Mn, Pb, and Zn metals in the Corbicula fluminae of Shatt Al-Arab river are 35.37, 291.25, 1.81, 2.24, 1.64, and 56.22 μg/g, respectively. Al-Khafaji et al. (1997) concluded the Cd, Co, Cr, Cu, and Pb metals in water of Shatt Al-Arab estuary were 33.11, 6.3, 52.1, 2.25, and 30.7 mg/l respectively.Salman (2007)

Heavy metals concentration
Metal concentrations for each sampling sites in sediments in this study are shown in Table 2 and Figure    Where Cm sample is the measured concentration of heavy metals in the studied samples, and Cm background is the geochemical background concentration of heavy metals (crystal average).The average abundances of Ni, Zn, Cu, and Pb metals in the earth crust are 44, 71, 25, and 17 mg/l respectively according to Taylor and Mclennan (1985), and average abundances of Cr and Mo in the earth crust are 69 and 1.6 mg/l, respectively according to Yuan-Hui Li (2000).In the present study, contamination factor (CF) for Cr, Cu, Mo, Ni, Pb and Zn was calculated, the results are present in  4 and 5).Contamination factor > 3 (considerable contamination) are found in site 3 for Cr and sites 1 and 2 for Mo.

CONCLUSIONS
It is has been reported that a large amount of heavy metals in soil causes environmental degradation and threatens all life forms because its toxicity.As a country develops economically, the expansion of industries, the building of new roads and infrastructure, and increasing population in Basrah city generates waste that has caused an accumulation of heavy metals in the soils of Shatt Al-Arab river.Sewage, industrial wastes, oil spelling and agricultural chemicals such as fertilizers and pesticides are the major causes of water pollution (Raulinaitis et al., 2012;Taraškevičius et al., 2013;Saha and Hossain, 2011;Akan et al., 2010).The order of main concentration of heavy metals in studied sites is Cr > Zn > Ni > Cu > Pb > Mo.Maximum degree of contamination factor was found in sites 1 and 2 respectively, and decrease gradually with move away from these sites as indicator to higher pollution in the sediments of Fao and Abu-AlKhssib areas as a result to oil spill from oil tanker ships, commercial ships, fish boats that passed from Abu-Flus port, manufacturing plant and ship repair such as Ur factory in Fao and in Abu AlKhassib, in addition to, Abadan oil refinery that built on Shatt Al-Arab banks in Iranian sides (Fig. 3) effected by throw the polluted wastes in Shatt Al-Arab river directly, and finally the agriculture lands that spread on the river banks of Abu Alkhassib and Fao areas, that all caused to accumulated of Cr, Ni, Zn, Mo and Cu elements in the river sediments and caused to increase the degree of contamination in these sites compare with sites of 3, 4, and 5 respectively (decrease gradually when move away from the source of contamination in sites 1 and 2) as shown in Figure 2A, B, C, D and E and Tables 5 and 6 determined the pollution level in the soil, dust, and shells in Basrah city, showed that the increase concentrate of Cr, Cd, Co, Pb with decrease of Fe, Cu, Ni.Study of Khwedim (2013), concluded that Pb, Ni, Cr, and Cd metals increased in the west and north of Basrah city, due to petroleum industries (AlSha'eiba oil refinery & oil fields) to the west of Basra city and the fuel combustion in the electrical power station (Al-Haritha and Al-Najebia) to the north of Basra city.Al-Jaberi (2014) cleared that Ba, Zn, Pb, Ni, Co, Cr, Sr, Cu, Mn and Fe in Corbiculafluminalis shells increased significantly from the beginning point toward the central part of Shatt Al-Arab River.The aim of this study is to detect the levels of contamination by Cr, Cu, Ni, Pb, Mo, and Zn metals in the sediments of Shatt Al-Arab river.

Fig
Fig. 2A, B, C, D and E: Concentrations of heavy metals (mg/l) in the sediments of the studied sites Contamination factor > 1 (moderate contamination) are found in all sites for Ni, Cu, Zn, sites 4 and 5 for Cr, site 1 for Pb, and sites 3, 4 and 5 for Mo.Contamination factor < 1 (low contamination) are found in sites 2, 3, 4 and 5 for Pb.On the basis of contamination factor, sediments are enriched for metals in the following order: Cr > Mo > Ni > Zn > Cu > Pb.
. Sediments are enriched for metals in the following order: Cr > Mo > Ni > Zn > Cu > Pb.According to quality guideline proposed by United States Environmental Protection Agency (USEPA) and contamination limit of heavy metals proposed by Environment management (soil quality standard), all the studied sediments were heavily polluted by Cr, and contaminated by both of Ni and Mo.Zn and Cu concentrations were moderately polluted, while all the sediments were un-polluted by Pb element.

Table (
Table 5) which indicator to exceed of contamination in the sediments of Shatt Al-Arab river towards Fao area.Contamination factor > 6 (indicate very high contamination) found in sites 1 and 2 for Cr (Tables 5).Maximum contamination factor was found in site 1, where degree of contamination was 19, degree of contamination values decreased gradually in sits

Table 5 : Contamination factor and degree of contamination for heavy metals
Table (6).The present study shows that sediments in studied sites are heavily polluted by Cr according to USEPA guideline, and contaminated by both of Ni and Mo metals according to Environmental management.Zn and Cu concentrations were moderately polluted according to USEPA guideline and non-contamination according to Environment management, while all the sediments were un-polluted by Pb according to both standards of USEPA guideline and Environment management.