Pollution assessment of the lower basin of Lakes Kainji/Jebba, Nigeria: heavy metal status of the waters, sediments and fishes

The objective of this investigation was to examine the heavy metal status of the lower basin of Kainji dam (used for hydroelectricity generation), which includes Lakes Kainji/Jebba, Nigeria, and the potential for human exposure to heavy metals from eating fish caught in the lakes. Water, sediments and fish were sampled from the lakes and evaluated for As, Cu, Co, Cr, Fe, Hg, Mn, Ni, Pb, Sb, Ti, V and Zn using the EDXRF technique. Fe and Mn were found to be present at high mean concentrations in the water (13 and 9 μg L^-1), sediment (7092 and 376 μg g^-1) and fish (11.4 and 4.6 μg g^-1) samples. Sb (3.2 μg L^-1), Ti (4.1 μg L^-1), Cr (2.2 μg L^-1), Co (1.2 μg L^-1), Cu (1.3 μg L^-1) and Pb (1.2 μg L^-1) in the water samples and Sb (29 μg g^-1), Ti (27 μg g^-1), V (27 μg g^-1), Cr (27 μg g^-1), Co (40 μg g^-1), Ni (33 μg g^-1), Cu (25 μg g^-1), Zn (59 μg g^-1) and Pb (19 μg g^-1) in the sediment samples were found to be of medium mean concentrations. The other metals were present at trace levels (<1 μg), including As and Hg in the fish and sediment samples. There was an appreciable increase in␣metal concentrations in going from the water to the sediment samples. The probable source of the pollutants is anthropogenic, arising from agricultural activities, corrosion/abrasion of the ferrous steel material and additives in the lubricants and insulation used for auxiliary services on the turbine floor of the dam constructed on the lakes. However, natural geological sourcing from the underlying lake rock cannot be totally ignored, particularly the high levels of Fe and Mn in the sediment samples. The potential risk for human exposure to these metals emanates from the fish caught in the lakes and subsequently consumed, as there are already significant levels of these metals in the two fish species analysed, Tilapia (Oreochromis niloticus) and Chrysicthys (Chrysicthys auratus).     

Trace elements and organochlorine pollutants in selected fish species from Lake Phewa,Nepal

Lake water and fish livers and gills of sahar (Tor putitora), spiny eel (Mastacembelus armatus), African magur (Clarias gariepinus), and tilapia (Oreochromis niloticus) from Lake Phewa, Nepal, were assessed for the concentrations of trace metals/elements and persistent organic pollutants. The lake water was neutral with low ionic and metallic concentrations as compared to high-altitude lakes of Nepal. The four elements Cu, Zn, Se, and Cd had highest concentrations in livers, indicating uptake from diet, whereas four other metallic elements Cr, Mn, Ni, and Pb had highest concentrations in gills, indicating uptake from lake water. O. niloticus tended to have most of trace metals in the liver at higher concentrations than the other species but significant differences among the different species were found only for Mn, Ni, and Zn in the gills. A pilot study on the concentrations of persistent organic pollutants in muscle revealed that dichlorodiphenyltrichloroethane and related compounds were the dominant organochlorine pesticides, having highest concentrations in C. gariepinus and lowest in O. niloticus.     

Risk assessment of heavy metal contamination in shrimp farming in Mai Po Nature Reserve, Hong Kong

An ecological survey was carried out to determine the sediment concentrations of nutrients and heavy metals and bioaccumulation of heavy metals in fish and shrimp including tilapia (Oreochromis mossambicus×O. nilotica), grey mullet (Mugil cephalus), gei wai shrimp (Metapenaeus ensis) and caridean shrimp (Macrobrachium nipponensis) in the traditional tidal shrimp ponds (gei wais) of Mai Po Nature Reserve, Hong Kong. The sediments collected from the landward sites contained higher nutrient contents, as well as zinc (Zn), chromium (Cr), copper (Cu), nickel (Ni) and cadmium (Cd) than those collected from the seaward sites, but vice versa for lead (Pb) and mercury (Hg). However, the concentrations of all metals were exceptionally high in the two sites located outside the reserve, suggesting that waters from Deep Bay might be the possible source of metal contamination affecting the reserve. All metals studied seemed to accumulate in the viscera of fish. Body size was the determining factor for the accumulation of heavy metals in caridean shrimp and gei wai shrimp but not fish. Concentrations of the metals studied in tissues of grey mullet and gei wai shrimp were found to be safe for human consumption. Concentrations of Cr in tilapia whole body (0.68–1.10 mg kg⁻¹ wet weight) were close to or over the guideline value of 1 mg kg⁻¹ set by the Food Adulteration (Metallic Contamination) Regulations of Hong Kong. Tilapia flesh and small caridean shrimp collected from gei wais were contaminated by Cr and Pb but still fit for human consumption. Caution is required if large caridean shrimp is to be consumed in large amounts continuously because the concentration of Pb exceeded the maximum permitted concentration (6 mg kg⁻¹). The rather high Cr concentrations in tilapia whole body should not be overlooked as the fish will serve as a food source for migratory birds visiting the site.     

Trace metals in fish of economic interest from the west of Alexandria,Egypt

The concentration of some heavy metals (Cd, Cu, Fe, Mn, Ni, Pb, and Zn) in the muscle, liver, and gills in eight fish species, Caranx crysos, Euthynnus alleferatus, Scomberomorus commerson, Sphyraena viridensis, Sargus sargus, Siganus rivulatus, Mugil species, and Sardinella aurita were collected seasonally from the Mediterranean Sea in the region of Alexandria. The highest concentrations of Cd, Cu, Fe, and Zn were measured in liver tissue, while gill tissue yielded the highest concentrations of Mn, Ni, and Pb. Muscle is the organ of poor accumulation factor for all metals under investigation. Concentration of cadmium in muscle in Mugil species exceeds the permissible limit in summer, while Siganus rivulatus exceeds it in the summer and autumn seasons. On the other hand, copper, nickel, lead, and zinc are still much lower than the permissible levels. The metal pollution index (MPI) for metals was studied, revealing that Siganus rivulatus, Mugil species and Sardinella aurita had the highest MPI. Provisional tolerable daily intake (PTDI) indicates that the concentration levels of Cd, Cu, Fe, Mn, Ni, Pb, and Zn in the muscle of all fish species under investigation are much lower than recommended PTDI values, and accordingly there is no risk for the human consumption of these fish species.     

A study on the accumulation of nine heavy metals in some important fish species from a natural reservoir in Riyadh,Saudi Arabia

Concentrations of nine heavy metals (Cr, Cd, Pb, Ni, Cu, Zn, Mn, As, and Fe) in the muscles of four fish species (O. niloticus, C. gariepinus, P. latipinna, and A. d. dispar) collected from the Riyadh River were detected using atomic absorption spectrophotometry in two different seasons in 2012. The concentrations of the studied heavy metals except Cd, Pb, Ni, and Cu in Aphanius d. dispar and Poecilia latipinna were found to be below the safe limits suggested by various authorities. This study also showed that Zn was predominant, while Cr was least accumulated metal in the studied fish muscles. Data demonstrated that there was a significant variation in the heavy-metal concentrations in different fish species in the Riyadh River. Significant positive correlations between heavy-metal concentrations in fish muscles were also found both in pre- and post-monsoon seasons. Metal pollution index was calculated to distinguish polluted from unpolluted ecosystems based upon current knowledge of metal bioavailability, bioconcentration, and bioaccumulation patterns. From the human health point of view, this study showed that there was a possible health risk to consumers due to the intake of Aphanius d. dispar and Poecilia latipinna under the current consumption rate in the country.     

Concentrations of Cd,Ni, Pb,and Cr in the two edible fish species Liza klunzingeri and Sillago sihama collected from Hara biosphere in Iran

The concentrations of four metals (Cd, Ni, Pb, and Cr) were determined in the muscles, gills, and livers of two edible fish species (Liza klunzingeri and Sillago sihama) caught from the Hara biosphere of Southern Iran. In both fish species, metal concentrations and bioaccumulation factors were in the sequence liver?>?gill?>?muscle. Bioaccumulation factors were found to be highest in S. sihama. The metal concentrations were descending in the order of Ni?>?Cr?>?Pb?>?Cd, except for muscle samples from S. sihama showing an inversion of Pb and Cr. There is a significant negative correlation between the concentrations of the metals in each tissue with length, weight, and age, except for muscle in L. klunzingeri. Some metal levels in the muscle exceeded the limits recommended by FAO, WHO, and FEPA.     

Metal partitioning in sediment pore water from the Ondo coastal region,Nigeria

Distribution and equilibrium partitioning of metals (Cd, Cu, Cr, Fe, Ni, Pb, Mn, and Zn) between pore water and surface sediments at the Ilaje coast of Ondo State, Nigeria, were studied. The Ilaje River can be one of the interesting research locations because of its economic nature and history of oil pollution. Seasonal variations were observed to investigate possible variations in the availability of metals for organisms throughout the year. The concentrations in both sediments and pore water during the dry and wet seasons were as follows: Cu?>?Fe???Mn?>?Pb?>?Ni?>?Cr?>?Cd?>?Zn. The pore water–sediment partition coefficient (K _p) showed that Zn and Cd were highly mobile while Fe and Cu have restricted mobility. Dissolved organic carbon (DOC) in pore water had a strong influence on mobility and bioavailability of all the metals (p?K _oc), increased levels of Fe and Cu were linked to lithological origin. Concentrations of Pb and Ni were associated with petroleum-related sources. The significance of the field-based techniques for ecotoxicological purposes is discussed.     

Heavy metal concentration in water,sediment, and tissues of fish species (Heteropneustis fossilis and Puntius ticto) from Kali River,India

The river Kali has been one of the major recipients of industrial effluents in the Muzaffarnagar district of western Uttar Pradesh. The present studies revealed the occurrence and bioaccumulation of heavy metals (Cd, Cr, Pb, Zn, Mn) in riverine water, sediment, and muscles of two fish species, Heteropneustis fossilis and Puntius ticto. Data showed that the order of occurrence of heavy metals was Pb > Zn > Mn > Cr > Cd in river water, Mn > Zn > Pb > Cr > Cd in sediment, Zn > Mn > Cr > Cd > Pb in Puntius ticto and Cr > Zn > Mn > Cd > Pb in Heteropneustis fossilis. Results indicate that the concentrations of Cd, Pb, and Zn in river water, Pb, Zn, and Mn in sediment, Cd, Cr, Pb, and Zn concentration in muscles of Puntius ticto and Cr, Pb, and Zn concentration in in muscles of Heteropneustis fossilis are higher than the permissible standard limits. The presence of heavy metals contributed to toxicity in different organs of fish in River Kali. The bioaccumulation of heavy metals in different biotic organisms in river ecosystem may have adverse consequences on humans and livestock.     

Concentrations of cadmium,manganese, copper,zinc, and lead in the tissues of the oyster (Crassostrea iredalei) obtained from Setiu Lagoon,Terengganu, Malaysia

Heavy metals pollution in aquatic environments is a major problem contributing to human health issues. The study of these pollutants through bioindicators such as the oyster Crassostrea iredalei is important for (1) determining the levels and sources and (2) regulating the quantity of pollutants. The concentrations of cadmium (Cd), manganese (Mn), copper (Cu), zinc (Zn), and lead (Pb) in tissues of C. iredalei, sediment and surrounding water was measured, and data was analyzed to determine the relationship between sampling periods and between oyster tissue, sediment, and water. The highest concentration of metals in oyster tissue was Zn, followed by Cu, Mn, Cd, and Pb. Concentrations of Cd, Cu, and Zn exceeded the maximum level allowed according to the Malaysian Food Act of 1983, which is equivalent to the WHO recommended levels of heavy metals in organisms used for consumption. The highest metal concentration in sediment was Mn followed by Zn, Pb, Cu, and Cd. Concentrations of heavy metals in surrounding water were Zn, Pb, Cu, Mn, and Cd. There was no correlation between metal concentration in oyster tissue and in sediment for all five metals.     

Physicochemical characteristics and distribution of some metals in the ecosystem of Lake Nasser,Egypt

To know the interrelationship between some metals in different ecosystem components (water, sediment, aquatic plant and fish), many samples from these components were collected from four bights at the Nasser Lake, Egypt, and analyzed for Fe, Mn, Zn, Ca, Mg, Pb, Cd, Ni, Co, Cu and Cr using atomic absorption spectrophotometer. Different distribution factors (bioaccumulation factor – BF, discrimination factor – DF and enrichment factor – EF) were applied on the results of analysis. Data showed that the relatively high concentration of measured metals in water samples are derived from fish farms, and discharge of tourism and trade ships. Applying single leaching sequential technique on sediment samples, using different extracting solutions, revealed a strong ability of trace metals to adsorb on or co-precipitate with amorphous Fe/Mn oxides. High concentrations of Fe, Mn, Co and Ni were measured in the intestine while high Cd and Cr concentrations were recorded in the stomach in both Tilapia (nilotica and galilea). Tilapia galilea accumulated high Pb, Cu and Zn concentrations in their stomach, while in nilotica high concentrations of Pb, Cu and Zn were measured in the intestine, liver and muscles, respectively. Myriophyllum spicatum (an aquatic plant) in the lake recorded high concentrations of Fe, Mn and Zn. Bioaccumulation factors of studied elements in the different bights components indicate that the elevated concentration of measured elements in the aquatic plant and Tilapia (nilotica and galilea) are derived from water, reflecting the increase of human activities in Nasser Lake in recent years. However, the present study concluded that all the elements studied were still below the natural back-ground levels, except Zn and Cu.     

Toxicity and bioaccumulation of heavy metals in mullet fish Liza klunzingeri (Mugilidae: Perciformes)

The mullet fish, Liza klunzingeri, commercially important and widely relished by Kuwaiti residents, and the stressed ecosystem in Kuwait Bay instigated us to conduct toxicity and bioaccumulation tests on heavy metals (Pb, Ni, V, Cu and Fe). Among five metals, Pb had the lowest observed effect concentration (LOEC) at 1 μg?l ^?1. Using multi-factor Probit analysis, toxicity tests (72 h) on L. klunzingeri reared in filtered sea water in the laboratory showed Pb with maximum effect at median lethal concentration (LC₅₀) followed by V, Ni, Cu and Fe. Their bioaccumulation factor (BAF) was in the sequence Pb>V>Fe>Cu and Ni. For fish exposed for 30 d, bioaccumulation exhibited increasing metal levels in liver followed by gills and muscles. These results suggest the potential use of L. klunzingeri as a bioindicator of metal pollution in the future.     

Heavy metal accumulation in water, sediments and fishes of Nallihan Bird Paradise, Turkey

The accumulation of some heavy metals such as Pb, Cd, Cu and Ni was determined in water sediment and fish samples (Albumus escherichii, Cyprinus carpio and Silurus glanis) collected from Nallihan Bird Paradise (NBP) and its vicinity (Sariyar Dam). The results showed that these metals are found widespread throughout the study area, but metal concentrations in the water samples are below the detection limits (BDL). Pb, Cd, Cu and Ni contamination were determined in sediments and in fish tissues (muscle and liver) and it was seen that they were accumulated and biologically magnified in lish tissues. Metal concentration levels in sediment samples were higher than that of water and fish tissues. The highest amount of metal concentrations in sediment samples among seven stations were determined in Usakbuku (Pb: 0.49 ppm), Sakarya River (Cu: 1.12 ppm) and Sariyar (Ni: 0.77 ppm). Unlikely to the other stations, no metal residues were determined in the sediment samples ofAladag Creek Station.     

A survey of lead pollution in Chhattisgarh State, central India

Lead (Pb) is of major environmental concern due to its toxicological importance. The anthropogenic emission of Pb is at least 100 times higher than natural emissions. Soil and dust are significant sources of Pb exposure. Lead is generally immobile in soil and accumulates in the upper layers. Lead particles may enter homes via shoes, clothes, pets, and windows. Central India is rich in deposits of natural resource materials such as coal, pyrite, dolomite, and alumina that contain Pb and other heavy metals at the trace levels, and the substantial exploitation of these materials has tended to increased contamination of water and geological formations. Here we present data on Pb concentrations in the water, soil and sediment samples (n=158) collected from 70 locations in Chhattisgarh state, Raipur region. Lead concentrations in the surface water (n=44), groundwater (n=44), soils (n=60) and sediments (n=10) ranged from 6 to 1410, 3 to 52, 12.8 to 545, and 31 to 423 μg g⁻¹, with mean values of 305, 16, 102 and 190 μg g⁻¹, respectively. Most of the Pb fractions of >80% can be leached out with the chemical extractants EDTA, acetic acid, and hydroxylamine hydrochloride. Lead has accumulated in the soil clay fraction due to its relatively large surface area and decreases with increasing depth in the soil profile.     

Sources and Distribution of Heavy Metals in East China Sea Surface Sediments

Box cores and surficial sediments collected from the shelf, slope and Okinawa Trough of the East China Sea were analyzed for loss on ignition, and concentration and speciation of Al, Fe, Mn, Pb, Cd, Cu and Zn. in general, concentrations of these metals are higher in the inner shelf and lower in the midshelf, but the highest LOI, Cd and Mn levels are found in the Okinawa Trough. Spatial distributions of these metals in surficial sediments indicate that the Yangtze River is the major source for materials deposited in the inner shelf. the results of a six-stage sequential leaching experiment indicate that the fluvial input includes natural (e.g., Al and Fe) and anthropogenic (e.g., Pb) materials. the depletion concentration of these metals in the midshelf sediments reflects the dominance (～ 70%) of coarse, relict sand, while the enrichments in the inner shelf and the Okinawa Trough sediments are due to the fine grained, organic-rich sediments. the speciation of Mn in the sediments of the Okinawa Trough indicates that its distribution is diagentically or hydrothermally controlled.     

A comparison of metals in sediments and water in the River Nahr-Ibrahim,Lebanon: 1996 and 1999

Rivers whose basins are underlain by carbonate rocks exhibit high pH, lower desorption of metals and possess high buffering capacity against acidic inputs to the river. The catchment of River Nahr-Ibrahim, Lebanon, is largely underlain by limestone. Compared to neighbouring countries, Lebanon is relatively fortunate since precipitation is high. However, recently a warming in temperature and a drop in precipitation has occurred, thus causing low water levels in rivers. The objective of this study is to investigate the variation of the total metal content (Fe, Mn, Zn, Cu, Pb and Cd) in bed sediments and water of River Nahr-Ibrahim between 1996 and 1999 (two years); and relate these variations to the effect of changes in human activities and/or due to the variations of precipitation rate, temperature and pH of water. Bed load sediments and stream water were collected simultaneously from five sampling sites. Water pH and temperature were determined in situ. Sediment samples were dried at room temperature and sieved; the sediment size <75 m size was retained. Water was analysed for major constituents and trace metals. Metals were extracted from sediments with aqua regia. Metal concentration in water and sediments were determined using ICP-MS technique. Data revealed a drop in metal concentrations (Zn, Cu, Pb, Cd) in sediments at quarry site after its closure. The decrease in precipitation rate, lowering the level of water and the dilution of industrial discharges and decrease in water pH led most probably to the desorption of metals from sediments into the water.     

Assessment of PAHs in water and fish tissues from Great Bitter and El Temsah lakes,Suez Canal,as chemical markers of pollution sources

Sea water and fish tissue samples were collected from nine sampling stations from the Great Bitter and El Temsah lakes in the Suez Canal and analysed for polycyclic aromatic hydrocarbon (PAH). The compositions of PAH determined in the dissolved fraction of sea water were measured in order to use them as chemical markers for identifying different sources of PAH pollution in this region. PAHs determined in fish tissues were measured for comparison with human health standards as consumption. The total mean PAHs concentrations in the sea water samples ranged from 0.28 to 39.57 μg l^?1 with an overall mean of 10.78 and 12.38 μg l^?1 for El Temsah and Bitter Lakes water, respectively. Total PAHs fractions recorded in muscle tissues of all different Osteicthyes fishes collected from Great Bitter lakes ranged from 5.8 to 218.5 μg g^?1 with an overall mean of 57.98 μg g^?1 during all seasons. However, they ranged from 68 to 623 μg g^?1 with an overall mean of 87.69 μg g^?1 recorded in El Temsah lake during four seasons (2003–2004). Benzo(a)pyrene was the most dominant PAHs found in the sea water samples from both lakes with an average concentration of 3.8 μ g l^?1. Dibenzo(a,h)anthracene (DBA) was the most dominant PAHs recorded in fish samples. A maximum of 533 μg g^?1 of DBA was recorded in Dahbana sp. collected from Bitter lakes during January 2004. However, a maximum of 68.7 μ g g^?1 was recorded in Liza carinata species collected from El Temsah lake during July, 2004. The simultaneous occurrence of isomer ratios PHE/ANT<10 for all stations indicated that the major PAH input to water was from combustion of fossil fuel (pyrolytic source). The average ratios were 1.21 and 12.9 during winter (January 2004) and 4.3 and 8.63 during spring (April 2004) for all water samples of Great Bitter lakes and El Temsah lake, respectively. In addition, the present data demonstrate that PAHs from fossil fuel sources (MW<178) were the least significant source of PAHs in this region.     

Assessment of heavy metals in water,sediment, Anabas testudineus and Eichhornia crassipes in a former mining pond in Perak,Malaysia

The concentrations of Al, As, Cd, Cr, Cu, Fe, Hg, Mn, Ni, Pb, Sn and Zn were analysed in water, sediment, muscle of climbing perch fish (Anabas testudineus), and tissue of water hyacinth plants (Eichhornia crassipes) collected from a former tin-mining pond in Perak, Malaysia. The monitoring was performed during the minimum and maximum rainfall periods. The concentrations of As, Cr, Fe, Ni, Pb and Zn in water exceeded the permissible limits set by the Interim National Water Quality Standards for Malaysia (INWQS). The risk index (RI) values determined for As, Cd, Cr, Cu, Hg, Pb and Zn in sediment presented a low degree of ecological risk. The order of the top three heavy metals measured in fish muscle was Zn?>?Fe?>?Al. The estimated daily intake (EDI) of As and Cr exceeded the allowable limits in both rainfall periods. The bioconcentration factor (BCF) and translocation factor (TF) values of Zn in water hyacinth were 24.865 and 3.214, respectively. The concentrations of Cu and Zn in the plant tissue were significantly correlated (p?<?.05) with the concentrations of heavy metals in water. Overall, climbing perch and water hyacinth are excellent bioindicators of environmental impacts on water bodies.     

Trace metals accumulation in soil irrigated with polluted water and assessment of human health risk from vegetable consumption in Bangladesh

Trace metals accumulation in soil irrigated with polluted water and human health risk from vegetable consumption was assessed based on the data available in the literature on metals pollution of water, soil, sediment and vegetables from the cites of Bangladesh. The quantitative data on metal concentrations, their contamination levels and their pollution sources have not been systematically gathered and studied so far. The data on metal concentrations, sources, contamination levels, sample collection and analytical tools used were collected, compared and discussed. The USEPA-recommended method for health risk assessment was used to estimate human risk from vegetable consumption. Concentrations of metals in water were highly variable, and the mean concentrations of Cd, Cr, Cu and As in water were found to be higher than the FAO irrigation water quality standard. In most cases, mean concentrations of metals in soil were higher than the Bangladesh background value. Based on geoaccumulation index (I _geo) values, soils of Dhaka city are considered as highly contaminated. The I _geo shows Cd, As, Cu, Ni, Pb and Cr contamination of agricultural soils and sediments of the cities all over the Bangladesh. Polluted water irrigation and agrochemicals are identified as dominant sources of metals in agricultural soils. Vegetable contamination by metals poses both non-carcinogenic and carcinogenic risks to the public. Based on the results of the pollution and health risk assessments, Cd, As, Cr, Cu, Pb and Ni are identified as the priority control metals and the Dhaka city is recommended as the priority control city. This study provides quantitative evidence demonstrating the critical need for strengthened wastewater discharge regulations in order to protect residents from heavy metal discharges into the environment.     

Trace metal pollution in aquatic sediments and some fish species from the Kwilu-Ngongo River,Democratic Republic of Congo (Bas-Congo)

In this study, the concentrations of some metals in sediments and consumable fish from the Kwilu Ngongo River, province of Bas-Congo, Democratic Republic of Congo, are investigated. The digested muscle tissue, whole fish, and river sediment samples were subjected to trace element analysis by inductively coupled plasma mass spectroscopy and by using an automatic mercury analyzer. The highest values of trace metals in fish muscle tissue were found for Cr, Cu, Pb and Hg, with maximum values of 8.6 (Cr), 15.7 (Cu), 6.0 (Pb) and 3.3 (Hg) mg kg^?1. These values are higher than maximum tolerable limits recommended by the European Commission Regulation for Food. The highest metal concentrations in sediments were 81 (Cr), 86 (Cu), 21 (Sb), 41 (Pb), and 0.8 (Hg) mg kg^?1. Sediment toxicity tests using benthic crustaceans (ostracods) revealed mortality rates of up to 30% after six days of exposure to the sediments near the sugarcane industry outlet pipe discharge. The contamination of the sediments and fishes by the elements and the bio-accumulation of mercury in fish most likely arise from the adjacent agricultural fields where intensive sugarcane cultivation since 1925 has probably contaminated the soils through the long-term use of fertilizers and pesticides.     

Trace metals in fish,sediment and water from the south west coast of the Arabian sea,Pakistan

Concentrations of ten metals (As, Cd, Cr, Cu, Fe, Mn, Ni, Pb, Zn and Hg) in the edible muscle of Arius maculatus captured from eight different near‐shore and off‐shore sites off the south west coast of the Arabian Sea, Pakistan, were determined by atomic absorption spectrophotometry. Relevant water and sediment samples from the sites were also analysed for the metals. Zinc showed the highest metal concentration (6.763 μg/g, wet weight) in the muscle of the fish, while Mn and Hg showed lowest level (0.019 μg/g, wet weight). Of all the metals investigated, largest scatter (measured as σ) was observed for Zn (σ = 2.058 /μg/g) in fish muscle, for Fe and Mn in sediment (σ = 27481 and 44.50 μg/g) and for As in water (σ = 0.270 μg/L). The metal distribution data pertaining to water, fish and sediment were examined on the basis of simple metal correlations. The statistical study revealed that Ni, Cr, Pb and Cu had significant positive correlations (r > 0.830 at ρ = 0.01). The finding substantiated a trace metal concentration gradient in the area, thereby indicating that the local marine environment is contaminated by anthropogenic sources.