Persistent, Bio-accumulative and Toxic Contaminants in Coastal Marine Environment of Pakistan

Abstract

The present work is the first of its kind to describe in detail the fate and distribution pattern of Persistence Bio-accumulative and Toxic (PBTs) in the coastal area of Pakistan bordering North Arabian Sea. The PBTs included OCPs, PAHs and Dioxins and Dioxin like PCBs. Despite their widespread use and injurious effect of PBTs, little information is available on contamination levels of these pollutants in the coastal marine environment of Pakistan. Mangrove swamps, intertidal mudflats and Indus Deltaic creek represent main feature of the coastal marine environment. The coastal areas are of significance as there are spawning, breeding and nursery grounds of commercially important fishery resources. These living resources are under continuous threat of untreated industrial effluents and sewages discharges into coastal areas via several sources. To evaluate the contamination levels of PBTs, 61 sampling sites were selected along coastal Pakistan, 09 sites were identified along the Balochistan coast, while 47 sites were identified along the coastal Sindh, and 5 sites were located in the Indus River. In the current study, the analytical method routinely used in Environmental Toxicological Lab and Queensland Health Lab was adopted for identification quantification of organochlorine Pesticides, PCBs and PAHs. Analysis was carried out by using Varian 3400 Gas Chromatograph equipped with a Finnigan A 200S auto sampler and Finnigan SSQ710 Single Stage Quadrapole Mass Spectrometer. Sediments were sent to the ERGO Laboratory in Hamburg for the determination of 2,3,7,8-substituted PCDD/PCDF and dioxin-like PCB. Identification of PCDD/Fs was carried out by using retention times of the 13 C-labelled standard and isotope ratios. The results on the contamination levels of PBTs revealed that residual concentration of Organochlorine Pesticides were considerably higher (17.5 ng g -1 dry wt.) in semi-enclosed area (Creeks and Karachi Harbour) in the effluent discharge areas, this was attributed to low tidal flushing. However, in the areas where port and harbour activities and untreated effluents from industrial and domestic sources are discharged, are reflective of highest PAHs contamination levels (2610.812 ng g -1 dry wt.) in the vicinity of Kemari jetty, Karachi Harbour area. Dioxin and Dioxin-like chemicals were detectable in all samples collected from Pakistan coastal environment. However, OCPs contamination levels in the sediment collected from Balochistan coastal environment were found below detection limit at almost all the sampling sites. Spatial distribution pattern were significantly different among the localities sampled (p<0.004). Distribution pattern of most of the PBTs were well correlated with total sediment organic carbon contents (p>0.767 & R 2 =0.66). A larger variation of ∑OCPs contamination levels (>0.002-17.5 ng g -1 dry wt. with a mean concentration of > 4.5 ng g -1 dry wt.) was observed in the samples collected from various localities of coastal area of Pakistan. The DDT’s metabolites DDE were found in soft tissue of the marine biota (fishes, crab, shrimps and molluscs) collected from Coastal area. The residue of DDT mainly its metabolites DDE and DDD were detected in most of the samples in relatively higher concentrations, compared with the concentration obtained for other OCPs. The high proportion of pp′-DDE at most of the site (41–95%) and ratio of ∑DDT and DDT (0.04 –0.24) suggests old inputs of DDTs in the environment, it is restriction have been made on the use of these chemicals. Pakistan has also switched over to natural pest control or using safer formulas. The concentrations of ∑ 16 PAHs varied amongst the localities, highest concentrations (2610.81 ng g -1 dry wt.) were detected in sediment samples collected in vicinity of Karachi harbour. Relatively lower levels (>400ng/g) observed in Korangi creek area south-east of Karachi. Higher concentrations of higher molecular weight PAHs such as (Benz(b+k) Fluoranthenen (>442.5 ng g -1 dry wt.), Ind(123cd)pyr (>270 ng g -1 dry wt.) and B(ghi) pryl (242.1 ng g -1 dry wt.) were detected near the discharge points of Lyari and Malir River. The Phen/Anth and Flth/Pyr concentration ratios indicated that mixture of pyrolytic and petrogenic PAHs sources at most of the site along the coast. First time water borne PAHs contaminations were estimated using Triolein- passive sampler Semi-Permeable Membrane Devices (SPMDs) as an alternative monitoring tool for coastal waters of Pakistan. The estimated water concentration was found to be highest in the harbour area (Cw SPMDs 4.6ng/l) that is well correlated (R 2 =0.5) with the evaluated contamination levels (Cw Sed. 35.67ng/l) using the levels observed in the sediment. According to the sediment quality standards of the USEPA and Canadian Council of Ministers of the Environment, observed levels of OCPs, PAHs and Dioxin contamination levels were generally lower than the threshold known to harm wildlife by OCPs. However, PAHs levels demonstrate moderate to low risk. Overall PCDD contributed to about 50 % of the TEQ in the samples with concentrations above 2 pg TEQ g-1 dwt and TCDD together with 1,2,3,7,8-PeCDD and 3,3',4,4',5-Penta-CB were the key contributors to the TEQ. The results clearly indicate the pollution problem regarding these contaminants was found localized and much lower than the concentrations reported from neighbouring and regional countries.