TRACE METALS IN SURFACE SEAWATERS IN THE RED SEA AND GULF OF ADEN-YEMEN

The present work has been done considering the constant spread pollution of heavy metals in water bodies. Pollution among water bodies is a major global problem. This contaminates not only the water but also the sediment and aquatic life such as fish. The water samples were collected from the three different Cities of Yemeni coasts. Aden, Al-Hodeidah and AL-Mukalla were chosen for the sample collection. The study was carried out in the all three seasons of winter 2011, summer 2012 and winter 2013 in order to check seasonal variation of heavy metal pollution.Total 81 samples of each Water were analyzed. The four heavy metals lead, Cadmium, Mercury and arsenic which are considered highly toxic were detected in the samples in the year 2010, 2012 and 2013. The heavy metal concentrations in the samples were measured using the Atomic Absorption Spectrophotometer. The obtained results showed that the concentration (mg/l) of the heavy metal in seawater (Pb-0.061±0.005, Cd-0.007±0.001, Hg0.007±0.0005 and As-0.008±0.0003) mg/l. The obtained results showed that the heavy metals concentrations were significantly higher, during the summer season for seawater samples in all stations during the study period. Because of the frequent use of water in the hot summer, resulting in an increase in sewage, as well as to the high rate of environmental variables in the summer. By comparing the results obtained with other data obtained from the local and international studies, in addition to, comparing the results standard levels of these metals contaminated and adopted internationally and domestically and the pollution levels in Yemen is currently within the lower limits of pollution. However, the study recommends continuing the study of these pollutants and other contaminants and their impact on the environment and marine life especially invertebrates.


INTRODUCTION
The pollution of aquatic systems has become a major concern worldwide 1 . There are a variety of sources that will pollute aquatic systems with heavy metals. These include animal matter, wet and dry fallouts of atmospheric particulate matter and human activities. The concentration, bioavailability and toxicity of heavy metals in aquatic systems can be affected by various factors, including pH and temperature 2 . Poor quality of surface water is caused in two ways. The pollution of surface water can either be due to point source (PS) or nonpoint source pollution (NPS). Point source pollution is mainly municipal sewage discharge and industrial wastewater loads. Municipal sewage discharge is from urban or highly residential areas, while industrial wastewater is from a variety of manufacturers 3 . When rainfall or irrigation water runs over land it will carry and deposit pollutants into rivers, lakes and coastal waters. This is seen as nonpoint source pollution 3 . Heavy metals will be distributed between the aqueous phase and bed sediments in aquatic systems 4 . Only a small percentage of the free metal ions stay dissolved in water. The majority of the ions get deposited in the sediment due to adsorption, hydrolysis and co-precipitation of the free ions 4 . There are various routes through which heavy metals can pollute aquatic systems. Deposition of atmospheric pollutants on solid surfaces, or on the surface of water bodies as well as the erosion of soil is the more natural routes for heavy metal pollution 5 . The concentration of most metals is usually low in pristine environments 4 .

ISSN: 2456-8058
54 CODEN (USA): UJPRA3 The main anthropogenic sources of heavy metal pollution are mining, smelting activities, disposal of untreated and partially treated effluents which contain toxic metals as well as metal chelates from various industries. According to human activities, which include mining, will produce pollutants that are discharged into aquatic systems either in dissolved or suspended form 6 . This can significantly decrease water quality and increase the ecological risk to human health. Pollutants can enter the environment through a variety of ways, such as storm water sinks, surface runoff, leaching and effluent discharge among others. Heavy metals can be released into aquatic systems either as pulses or discontinuously 6 . When heavy metals are released into aquatic systems it will bind to particulate and organic matter. Eventually the heavy metals will be incorporated into the sediment. Sediment is an important reservoir of heavy metals. Many studies were done that investigated the presence and effects of heavy metals in aquatic ecosystems as well as aquatic organisms 6,7,8 .

2.1: Description of the Study Area 2.1.1: Aden City
Aden is a port city in Yemen, located by the eastern approach to the Red Sea (the Gulf of Aden), some 170 kilometres (110 mi) east of Bab-el-Mandeb.It is a semi island and consists of rocks. Aden's population is 774000 in 2013 (Yemen Statistical Yearbook, 2013), The convenient location of Aden's natural Port on the major sea route between the Far East and Europe has resulted in a rich history as a trading center. Aden's importance as shipping center peaked in early 1960s, when it was the fourth busiest port in the world (Nasr et al., 2006).has a port with an oil refinery and an oil import/ export terminal. This terminal handles around 9.8 million tons per year. Nine, characteristic stations on the coastal area of the Aden port were sampled during this study (Surface seawater and sediments). The nine sites were picked up precisely and according to the importance of each one of the selected sites. The locations are shown on the map presented in the Figure 1.

2.1.2: AL-Hudaydah City
Location map (Figure 2) shows the study area, AL-Hudaydah Fishery port, from which the samples were collected for the determination of heavy trace metals. The study area was selected depending on many reasons, among which sewage effluent which is located to the south and north of the study area. In addition, the area receives the wastewater from treatment plant, which discharges large quantity of untreated sewage to the south of the Fishery Port, and to the north of Al-Hodiedah Commercial Port. AL-Hudaydahis located along the western coast of Yemen. Coast of AL-Hudaydah city , Yemen. AL-Hudaydah is the largest coastal city in the region, and is one of the major port in Yemen, with the estimated population of 979.000 in 2013 (Yemen Statistical Yearbook, 2013). It is the city having a sewerage system of treatment plants in the region. Its municipal sewage is discharged into a series of eleven oxidation ponds which serves nearly 35% of the residential population, with about 18000 cubic meters daily discharged. It contains several types of industrial liquid effluent and animal waste. About 70% of the municipal sewage is used for agriculture purposes, including windbreaks. The remainder (30 %) is discharged through a small open channel north of the city into the seawater close to khawr Al Kathib.   (Table 1).

2.3: Surface Seawater Sampling and Analysis 1. Surface Seawater Sampling
Seawater samples were collected seasons for analysis from one levels; the surface Seawater of each station along with sediment samples. In principle, collect seawater samples at high tide and avoid windy or rainy days). Before sampling, the bottles of samples were rinsed at least three times with water from the sampling station. The bottles were immersed to about 20-30 cm below the water surface to prevent contamination of heavy metals from air. For mercury analysis water samples kept in a sealable glass container that has been well washed before being transported 9 . For Arsenic analysis water samples were collected according to the Method 1632 USEPA 10 . A total of 81 of seawater samples were collected using cleaned plastic water sampler. Each sample was taken in 1 liter polyethylene bottles. All water samples were immediately brought to the laboratory where filtered through Whatman No.41 (0.45 μm pore size) filter paper. The samples were acidified with 2ml nitric acid to prevent precipitation of metals, reduce adsorption of the analyses onto the walls of containers and to avoid microbial activity, and then stored at 4°C until the chemical analyses.

Surface seawater digestion and analysis i. Surface Seawater Digestion for Pb and Cd Analysis by GFAAS
Five milliliter of concentrated HCl was added to 250 ml of each surface seawater sample placed in 600 ml beaker and evaporated to 25 ml volume. The concentrate was transferred to a 50 ml volumetric flask and diluted to mark with deionized water. Prior analysis, the solutions were filtered through Whatman No.41 (0.45 μm pore size) filter paper. Analyzed for Lead (Pb) and Cadmium (Cd) using Buck Model 210 VGP, USA Made -Graphite furnace Atomic Absorption Spectrophotometer (GF AAS) in Seawater samples, before proceeding Method 200.13 US EPA 11 . Triplicate sub-samples of each sample were aspirated separately to compute mean metal concentrations in a given sea water and sample.

ii. Surface Seawater Digestion for Hg and As Analysis by Hydride Analyzer
Forty five millilter of surface seawater sample was measured .A volume of 5 ml of concentrated nitric acid (HNO 3 , 65 %), 1ml of concentrated hydrochloric acid (HCl, 35 %) was added to each sample . Vessels Sealed and placed in microwave system. Samples were heated according to time versus pressure profiles. Vessels allowed cooling to the room temperature and then each sample transferred to a final volume of 25 ml using deionized water. The Sample may represent a safety hazard. Pre-digest sample in a hood, with vessel loosely capped to allow gases to escape, before proceeding Method 3015A US EPA 12 . Triplicate sub-samples of each sample were aspirated separately to compute mean metal concentrations in a given sea water and sample. Blanks Three types of blanks are required for the analysis. The calibration blank is used in establishing the analytical curve, the laboratory reagent blank is used to assess possible contamination from the sample preparation procedure, and the laboratory fortified blank is used to assess routine laboratory performance. This study focused on determination on the levels of selected heavy metals namely: lead, cadmium, mercury and Arsenic in filtered surface Seawater of the major

RESULTS
Analysis of heavy metals for 81 Sea water samples was carried out, for the study period of three years (three seasons). The overall means results of analysis heavy metals in the filtered water surface for the three seasons, for the study sites in Yemen are presented in Table 2.
The results of the present study showed that there were significant differences (P<0.01), using one way ANOVA, regarding the concentration of Pb , Cd and Hg, however, there was no significant difference (P>0.05) regarding the concentration of As in the filtered surface water of Aden, for the period of  Table 2.
On the other hand, the results showed that there were significant differences (P<0.01), using one way ANOVA, regarding the concentration of Pb, Cd and Hg, however, there was no significant difference (P>0.05) regarding the concentration of As in the  Table 2.
The results of present study were analyzed by using two ways ANOVA in filtered surface water of Yemen sites during the seasons, it showed that there were significant differences (P<0.01) regarding the concentration of Pb, Hg and As, however, there was significant difference (P<0.05) regarding the concentration of Cd in the filtered surface water of Aden, AL-Hudaydah and AL-Mukalla station.
The highest concentration of Pb in filtered surface water of AL-Hudaydah was 0.080 mg/L, whereas the lowest concentration was 0.050 mg/L of Aden station; however, the highest concentration of Cd in filtered surface water of Aden was 0.008 mg/L, whereas the lowest concentration was 0.007mg/L of AL-Hudaydah station. The concentration of Hg in filtered surface water had the same pattern of Pb and Cd ; but, the highest concentration of Hg in the filtered surface water of AL-Mukalla was 0.0075 mg/L, whereas the lowest concentration was 0.005 mg/L of Aden station. The highest concentration of As in filtered surface water of AL-Mukalla was 0.010 mg/L, whereas the lowest concentration was 0.006 mg/L of Aden site ,as summarized in Table 2.
In addition, when the results of present study were analyzed by using two ways ANOVA in filtered surface water of Yemen sites during the seasons, it showed that there was significant differences (P<0.01) , analyze by using two ways ANOVA, regarding the concentration of Cd and Hg , however, there was significant difference (P<0.05) regarding the concentration of As, however, there were no significant difference ( Yemen sites was 0.007 mg/L on winter, whereas the lowest concentration was 0.006 mg/L on summer, the highest concentration of As in filtered surface water was 0.0083 mg/L on summer, whereas the lowest concentration was 0.0077 mg/L on winter, as summarized in Table 2.

DISCUSSION Heavy metals in filtered surface water
Overall, the results of the present study showed that they were significant differences (P<0.01), using one way ANOVA, regarding the concentration of Pb, Cd, Hg and As in the filtered surface water of Yemen coast (Aden, AL-Hudaydah and AL-Mukalla) sites, except As in Aden and AL Mukallala, and except Pb and Cd in AL-Hudaydah, for the period of seasons: winter 2011, summer 2012 and winter 2013 ( Table 2). On the other hand, thus results were analyzed by using two ways ANOVA, there were significant differences (P<0.01), regarding the concentration of Cd and Hg, however, there was a significant difference (P<0.05) regarding the concentration of As in the filtered surface water of Yemen sites for the period of seasons: winter 2011, summer 2012 and winter 2013. The highest concentration of Pb, Cd and As were (0.065± 0.027, 0.008±0.002 and 0.0083±0.002 mg/L, respectively) in the filtered surface water of Yemen coast was obtained in the summer, whereas the highest concentration of Hg was 0.007±0.002 mg/L in the filtered surface water of Yemen coast was achieved in winter ( Table 2). This result may be explained by the fact that amount of draining sewage on summer were higher compared with winter and also due to high water temperature on summer season. The interpretation of these results is comparable to those reported in a previous study 15 that the concentrations of metals are increased during summer due to increase the water temperature; and 16 reported that the high heavy metal concentration during the summer may be attributed to increased water temperature during the summer that may result in increased metal toxicity. Also Hg has a different character than Pb, Cd and As and has able to evaporate in the air; As supported also by a study 17 who pointed out that the distribution of Hg was different to the other heavy metals due to Hg is easy to vaporize and to move from one place to another . Also the above results and the initial interpretation given are comparable to those reported in 2014 by a previous study 18 that the highest concentration of Pb in summer, but the highest concentration of Hg in the filtered surface water was from Khawr-Mukalla, Hadhramout Coast, Yemen, in Autumn 18 . However, our results showed low concentration compared with other studies which mentioned by a previous study 19 showed that the concentration of Cd was 0.014 mg/L and As was 0.013 mg/L in summer, but the concentration of Pb was 0.012 mg/L and Hg was 0.014 mg/L in Winter from near seashore of Bay of Bengal in Marina, it's the longest urban beach in India 19 . However, our results are in a good agreement with those found by 20 showed that the concentration of Pb was 0.034 ± 0.002 mg/L and Cd was 0.012 ± 0.001 mg/L in water from the Kolleru Lake, India, on summer 20 . The results of the present study were analyzed by using two ways ANOVA in filtered surface water of Yemen sites during the seasons, it showed that there were significant differences (P<0.01) regarding the concentration of Pb, Hg and As, however, there was a significant difference (P<0.05) regarding the concentration of Cd in the filtered surface water of Aden, AL-Hudaydah and AL-Mukalla station. The highest concentration of Pb was 0.080± 0.008 mg/L achieved in AL-Hudaydah, however, the highest concentration of Cd was 0.008±0.002 mg/L achieved in Aden, but the Hg was 0.0075±0.001 mg/L and As was 0.010±0.000 mg/L in the filtered surface water were found in AL-Mukalla. The CSBTS 21 , ANZECC and ARMCANZ 22 and ASEAN 23 guidelines for maximum permissible limit of Lead in Seawater is 0.001, 0.0044 and 0.0085 mg/l. As the range of Lead detected was higher than the permissible limit. There are several possible explanations for this result perhaps attributed to partially caused also by atmospheric input of local particulates from motor vehicle, mountainous regions which drain its water from Yemen highland to the Red Sea through different vallies, precipitation, petroleum rich substrate of the area, influence of sewage discharge, agricultural and industrial effluents into this site, chemical distribution and partitioning between seawater and the sediment and the vigorous mixing of shallow coastal sediments increases the solubility of Pb in seawater as a result of oxygen saturated water 24,25,26,27 .
The CSBTS 21 and ANZECC and ARMCANZ 22 guidelines for maximum permissible limit of Cadmium in Seawater is 0.001 and 0.0007 mg/l. As the range of Cadmium detected was higher than the permissible limit. But ASEAN 23 guidelines for maximum permissible are limit of Cadmium in Seawater is 0.01 mg/l. As the range of Cadmium detected is below than the permissible limit. These high concentrations of Cd in Aden may be attributed to point source and nonpoint source pollution among which are PVC products, runoff from waste Ni-Cd batteries, paint, color pigments and solid waste 28 . These results further support the idea of Scrap-iron store at Labour Island in Aden site is the most likely source of Pb and Cd in the Seawater 29 . These results corroborate the ideas of a previous study 30 suggested that when contaminated particulate or sedimentary material is dispersed through an ecosystem, it equilibrates with water, detritus, and living food materials, resulting in ongoing contamination of all environmental compartments 30 . The detected positive correlation between the concentration of Cd in the filtered surface water and sediment, in the present study, supports this argument. The CSBTS 21 , ANZECC and ARMCANZ22 and ASEAN 23 guidelines for maximum permissible limit of Mercury in Seawater is 0.00005, 0.0001 and 0.00016 mg/l. As the range of Mercury detected was higher than the permissible limit. The CSBTS 21 guidelines for maximum permissible limit of Arsenic in Seawater is 0.020 mg/l. As the range of Arsenic detected is below than the permissible limit. The present high ISSN: 2456-8058 58 CODEN (USA): UJPRA3 concentration of Hg and As in AL-Mukalla may be due to the petroleum rich substrate of the area, oil pollution and atmospheric fallout could be responsible for the increased levels, also high values of As in the site may be attributed to agriculture. Also the above results and the initial interpretation given are comparable to those reported by a previous study 27 that the concentration of Pb was 0.03±0.004 mg/L and Cd was 0.02±0.004 mg/L in summer from along the coast of Al-Shaykh Younes facing AL-Hudaydah city, Yemen 27 . The interpretation of these results is comparable to those reported by a previous study 18 pointed out that the concentration of Pb was 0.058 -0.132 mg/L, Cd was 0.014 -0.030 mg/L, Hg was 0.005 -0.008 mg/L in Khawr-Mukalla, Hadhramout Coast, Yemen. This differs from the findings presented here may be attributed to drain sewage at first time into Khawr-Mukalla and noncoastal currents 18 and a good agreement with those are found by a previous study 31 pointed out that the concentration of Pb was 0.064-0.082 mg/L, Cd was 0.002-0.005 mg/L in Jeddah Coast, Saudi Arabia 31 . However, our results are in a good agreement with those founded by a previous study 32 that reported that the concentration of Hg of filtered surface seawater was 0.002 -0.005 mg/L in the Langkawi island, Malaysia 32 . Besides a previous study pointed out that the concentration of Pb was 0.03-0.07 mg/L, which is below the permissible limit of 0.1 mg/L set for inland surface water, in the water samples collected from sea water in Międzyzdroje, Baltic coast, Poland 33 . However, our results were high concentration compared with other studies which mentioned by 26 showed that the concentration of Pb was 0.050 µg/L and Cd was 0.760 µg/L in winter from AL-Hudaydah Coast, Yemen 26 . Also a previous study 25 17 . Besides a previous study 33 pointed out that the concentration of Cd was 0.39-0.52 mg/L, the values obtained were found to be below the permissible limit of 2.0 mg/L set for inland surface water. Hg was 0.03-0.05 mg/L which was very much above the maximum limit of 0.01 mg/L set for inland surface water in the water samples collected from sea water in Międzyzdroje, Baltic coast, Poland 33 . Based on these information's, Yemen coast of the present study is low polluted compared with other locations.

CONCLUSION AND RECOMMENDATIONS
The following can be concluded from this study results: The present work has been done considering the constant spread pollution of heavy metals in water bodies. Pollution among water bodies is a major global problem. This contaminates not only the water but also the sediment and aquatic life such as fish. Lead content in all locations in all seasons was higher than the permissible limits according to international standards. The Cadmium in Seawater in the Summer season shows that Site Aden is highly polluted in Summer 2012 with 0.008±0.002 mg/l . As the range of Cadmium detected is below than the permissible limit. The Arsenic concentration was found high at Site AL-Mukalla, 0.010±0.000 mg/l in Year 2012 (summer season). As the range of Arsenic detected is below than the permissible limit. The Mercury concentration was found high at Site AL-Mukalla, 0.0075±0.001 mg/l in Year 2011 (Winter season). Mercury content in all locations in all seasons was higher than the permissible limits according to international standards. From the heavy metal concentrations mentioned above we can see that somewhere the concentration is crossing the limits as permissible by the World Health Organization. It suggests a high risk to the health of human being on the consumption of contaminated fish. Therefore it is recommended that the practice of trace element detection should be continued in order to update whether the heavy metal concentration is above or below the permissible limits and if it is above the limit then precautions must be taken to avoid possible consumption of contaminated eatables. It is also recommended that awareness should be spread among the people regarding the hazards on consumption of polluted water and related eatables. It is also essential that farmers should be educated to reduce such contamination and should be encouraged to use the controlled amount of pesticides, to avoid the leaching of waste water and cultivating in a field far away from industrial area as well as areas prone to contamination.

RECOMMENDATIONS
From the study results outcome the following can be recommended: The following recommendations might be of particular interests • Enforcement of Marine Protection regulations in Yemen is urgently required. • Building-up of local capacities is highly recommended to acquire capabilities in assessing and monitoring marine pollution at regular bases. • There is a need for regulating cooperation among authorities whose major concern is protecting marine environment at national and international levels . • Initiating strategies for public awareness about marine pollution would be a major contribution in lowering activities that cause marine pollution. • Strengthening of a data-base information system would be a great help for researchers to carry out scientific studies in subsequent bases .
• Devoting more efforts for carrying out further studies on assessment of contamination in other marine species with other pollutant would help in drawing a complete picture with regards of pollution status in regional sea catchments area of Yemen.  Results are expressed as mean ± SD. Mean values in the same row with different superscript letters indicate significant (P<0.05) difference.