Assessment of persistent organic pollutants in water samples from River Challawa in Kano, Nigeria

Almost every type of industrial process releases some amounts of toxic organic and inorganic compounds that ends up in water bodies and/or other environmental compartments. This study was aimed at assessing the levels Persistent Organic Pollutant in Challawa River Basin of Kano State, Nigeria. The investigation was particularly plan to assess the presence of PCBs and PAHs in River Challawa and compare the concentrations of the pollutants with the acceptable limit set by Nigerian Standard and other international regulatory agencies. Data were collected using reconnaissance survey; laboratory experiment as well as other secondary data sources. A total of 26 water samples were collected through stratified and systematic random sampling. Three sampling points were chosen and designated A, B and C along the stretch of the river (i


Introduction
Environmental pollution is the presence of toxic substances naturally or due to man's activities in the environment at a level where acute effect can be recognized.These toxic substances do not only remain in the environment but are transferred directly or indirectly into the body of man in different ways.Direct transfer into the body of man as a result of ingestion of contaminated food and water may affect organs, such as liver (Duffus, 1990).Industries have been identified as the major source of these pollutants either as products or by-product.Almost every type of industrial process involves the release of trace quantity of toxic organic and inorganic compounds that can contaminate soil, water, air, aquatic organisms and crops thereby posing health hazard to human lives as well as natural functions of ecosystem.
The Persistent Organic Pollutants (POPs) are twelve toxicant, this are Dioxin, Mirex, Dichlorodiphenyl trichloroethane (DDT), Chlordane, Polyaromatic hydrocarbon (PAH), Polychlorinated biphenyls (PCBs), Furans, Aldrin, Dieldrin, Eldrin, Heptachlor and Toxaphene.POPs persist in the environment, bioaccumulate through food chain and possess risk to human (European Commission, 2009).POPs are grouped according to their use and origin.PCBs and PAHs originate industrial chemicals.Other 8 are pesticides introduced into environment from various activities or uses and the remaining two Furans and Dioxin from unintended industrial processes (Langer, 2005).
PCBs are a group of man-made chemicals.They are oily liquids or solids, clear to yellow in color, with no smell or taste.PCBs are very stable mixtures that are resistant to extreme temperature and pressure and therefore are group of synthetic organic chemicals that can cause a number of different harmful effects.There are no known natural sources of PCBs in the environment and are widely used in electrical equipment like capacitors, transformers, heat transfer fluids, lubricants, and plasticizers (Illinois, 2009).
Adults and children may come into contact with PCBs while swimming in contaminated water and by accidental swallowing of the water during swimming.However, both of these exposures are far less serious than exposures from ingesting PCB-contaminated food or inhalation of PCB-contaminated air.
The abbreviation PAHs denotes polycyclic aromatic hydrocarbons, which are a class of organic compounds, characterised by two or more fused aromatic rings.PAHs that occur in the environment are a cause for concern because of their mutagenic and carcinogenic effects (Kim & Vane, 2007).They are mostly anthropogenic in origin and commonly arises from run-off, industrial sewage discharges, spillage, shipping activities and many more.The natural sources could for instance be oil seepage from underground.Additionally, but to a lesser extent, petrogenic PAHs in sediments can originate from the digenesis of natural precursors like terpenes, pigments and steroids (Kim & Vane, 2007).
Most exposures to PAHs happen at very low levels through the air we breathe and the foods we eat.However, some PAHs are used to make dyes, plastics, and pesticides (Al-Rashdan, Murad, Helaleh, Nisar, Ibtisam & Al-Ballam, 2010).
Nigeria and International agencies such as EPA has a threshold limit of 0.0007 and 0.0005 milligrams of PAHs per litre of drinking water (Adeyemi, Grace, Chimezie & John, 2009).Documented information on local status of Persistent Organic Pollutant (POPs) in Nigeria in respect of the extent of use; toxicology; residues, occupational accidents; persistence and bioaccumulation is very scanty (Soyombo, 2000).The analysis persistent POPs analysis is expensive, which deters the scientists in developing countries to participate in their investigation.This is clear from the relative lack of publications and information on POPs from countries in Africa, South Asia and South/Central America (Derek, 2003).Thus, there is dearth of information on the concentrations of POPs especially PAH and PCBs in the study area.There is therefore the need to carry out this investigation to determine the concentrations of the POPs and assess their possible threat on human health and other living organisms that interact directly and indirectly with the river ecosystem.
Challawa River as shown in figure 2 is located on the southern part of Kano has a confluence with River Kano at Tamburawa and is about fifty kilometers (50km) in length.It flows from south to west and is about 500 meters above the sea level.

Number of samples collected
A total of 26 water samples were collected according to the procedures.The required number of samples for a mobile matrix such as stream water, fish, etc. may be estimated as follows: Where: N = number of samples t = Student-t statistic for a given confidence level of 95% s = overall standard deviation, and U = acceptable level of uncertainty, Where: s = 0.5 mg/l U = 0.2 mg/l t = 95% Using the curves, it was found that approximately 25 to 30 samples must be taken (APHA, 2005).

Water Sampling Techniques
Data were collected using reconnaissance survey, laboratory analysis and other secondary data.A total of 26 water samples were collected through stratified and systematic random sampling.Three sampling points were chosen at designated sites (A, B and C) along the stretch of the river (i.e.upstream, midstream, and downstream) respectively to the point of discharge from Yan Danko to Tamburawa bridges.Thus, 4 samples each were collected at the 3 designated sampling points and another sample at the control site making a total of 13 samples.The sampling procedure was performed for 2 seasons (wet and dry seasons) making a total of 26 water samples.
Water samples were collected by slowly lowering a tilted wide-mouth sample bottle into the water until the water began to run into it.The bottle was then turned slowly upright keeping the lip just under the surface of the water so that the whole sample was surface water and the bottle was carefully lifted with disposable wiping cloths and capped.Each water sample collected measured up to 4 litres.Samples were stored in a dark cool container and taken immediately to laboratory after placing the inscribed label, showing the name of the sample collector, location, time, date, sample number and sample name.All contaminated materials were then placed into a plastic bag for disposal or decontamination.Samples were transported to the laboratory in an ice chest (USEPA, 2004).

Laboratory Analysis
The whole sample reagents, apparatus and machine for this research were obtained from National Research Institute for Chemical Technology, Nigeria (NARICT), Environmental Pollution laboratory in Ahmadu Bello University Zaria.Digital Gas Chromatograph Mass Spectrophotometer (GCMS) was used in determining PCBs and PAHs.

PAHs and PCBs -GC/MS Analysis
PAHs were prepared by dissolving about 0.01 g of sample in hexane.From these solutions, mixed solution of PAHs ranging from 100-1000 pg/l were prepared in hexane.These solutions were stored in amber flasks at 21 o C. Three PAHs calibration points were prepared: 100, 500, and 1000 pg/l.d-PAHs (1000 pg/l) were added to stock calibration solutions as well as to the samples before extraction.The samples were corrected for a recovery by applying an internal standard method, since PAHs and d-PAHs follows the similar steps in extraction and analysis.Similar method adopted from (Al-Rashdan, et al., 2010).
All solvents were of HPLC-grade.Hexane and dichloromethane were supplied by (NARICT).The chromatographic column was used for clean up of the extract, filled with 2 g of silica gel and 1 g of Aluminium oxide.Nitrogen gas was used to concentrate the extract.

Extraction Procedure and Sample Preparation
5g water samples were spiked with d-PAHs, and extracted with mixed solvents of 150 ml hexane: dichloromethane (1 : 1), using a Soxhlet apparatus for 16 h.The solvents were reduced to 1 ml using a rotary evaporator and N2 gas.The extract was then passed through a cleanup column filled with 2 g of 100-200 mesh silica gel, followed by 1 g of aluminum oxide (considered to be the most efficient and selective for column chromatography separation) and anhydrous sodium sulfate.The column was washed with 10 ml of hexane and the PAHs were collected by eluting the column with 8 ml of hexane and 5 ml of dichloromethane.Finally, the extract was concentrated to 1 ml under a weak nitrogen flow at ambient temperature.This solution is then injected to GC/MS for PAHs analysis.Quantification of individual PAHs was based on internal calibration standard containing known concentrations of 26 PAHs and d-PAHs (Al-Rashdan et al., 2010)

Gas Chromatography-Mass Spectrometry Conditions
PAH Analyses were performed with the GCMS-QP2010 Plus Shimadzu, Japan interfaced to a mass selective detector.The separation of PAHs was performed using a 5% phenyl-methylsilicone (DB-5MS) bonded-phase fused-silica capillary column (Hewlett-Packard, 30 m 0.25 mm i.d., film thickness 0.25 m).The injector port was run in splitless mode.The oven temperature program was 20 o C for 2 min, raised to 32 o C and maintained at this temperature for 8 min.The transfer line was maintained at 31 o C. The mass spectra were collected by electronic impact at 70 eV.Stock solutions were used to establish the retention time of each analyte.Detection of PAHs was carried out using SIM mode, which is designed for preselected ion peaks, non-selected peaks are not identified and quantified (Al-Rashdan et al., 2010).

GC-MS Procedure Performance
The chromatograms of the 26 selected PAHs in the standards and water samples are shown in Figures 1.1 and 1.26, the PAHs shows a wide spectrum of volatility and all 16 PAHs behave the same in chromatographic area in the standard and the sample.The set of samples was analyzed along with a blank for PAH background correction.The results were corrected for recoveries using an internal standard method, assuming that PAHs and d-PAHs behave in a similar manner during extraction and analysis.Recoveries of d-PAHs were utilized to estimate recoveries of the native PAHs.The average recoveries of d-PAHs varied from 79.11% to 91.56% with relative standard deviation (RSDs) ranging from 7.02% to 8.86%.Chromatogram of polycyclic aromatic hydrocarbons (PAHs) obtained using the GC-MS method.Numbers on the chromatogram refer to the individual PAHs as indicated in different figures.The results obtained shows that the method is very accurate and precise.Similar method adopted from (Al-Rashdan et al., 2010).165

GCMS Performance Tests
At the beginning of each day that analyses are to be performed, the GC/MS system must be checked to see that acceptable performance criteria are achieved.A 2 μL volume containing sample ng of perfluourotributylamine (PFTBA) is injected into the GC/MS for this purpose.

Calculations of PAH and PCBs Concentration
The concentration of each identified analyte in the sample can be calculated as follows Anonymous (1999): Where:

Results and Discussion
The results of the assessment of the polycyclic aromatic hydrocarbons and polychlorinated biphenyls level of water samples analysed show that none of the PCBs congeners were detected while, PAH pollutant detected in the majority of the water samples analysed were Pyrene, Phenanthrene, Benzo(a) pyrene, Ethyl Pyrene, Chrysene, Benzo(a) pyrene, Fluorene etc.However, the total PAH concentrations detected in the water that ranges between 0.001 to 0.087mg/l were above the maximum permissible level of 0.0007 mg/L as stated by Nigerian standard organization for drinking water.
Analysis of Variance were obtained using Bartlett's test performance show that there is significant difference in the concentrations of PAHs in water samples at the various sampling points along the Challawa river.
Nigerian standard for drinking water set a threshold limit of 0.0007mg/L for PAH compound SON (2007).hwhile for U.S. Environmental Protection Agency Water 0.0001 mg/ L is the maximum

Bar chart representation of water concentration against density
The result of water analysis revealed that the concentrations of PAHs exceeded the acceptable limit of 0.0007mg/L set by Nigeria drinking water quality standard.
Polychlorinated biphenyls (PCBs) were not detected in the whole samples analysed while, polycyclic aromatic hydrocarbons (PAHs) were detected at the Challawa River.The total concentrations of PAH detected ranges between 0.001 to 0.087mg/l.Some selected PAHs compound notably Benz(a)anthracene, Benzo(b)fluoranthene, Benzo(a)pyrene, Dibenz(a,h)anthracene, and Indeno(1,2,3-c,d)pyrene Known animal carcinogens ATSDR (1995).While Benz(a)anthracene and Benzo(a)pyrene have been classified by Agency for Toxic Substances and Disease Registry (ATSDR) as Carcinogenic to humans Pyrene causes skin, lungs, bladder, gastrointestinal cancer, Naphthalene its produce toxic reactions, especially newborns.Other PAHs compound also causes cataracts, liver and kidney damage.They also cause in nausea and vomiting.The levels of PAHs in most of the water samples analyzed exceeded the acceptable limit set by Nigeria and U.S standard.
Surprisingly the result also revealed the presence of synchronous PAH compound.This can be predominantly attributed to the discharge and emission of the industrial effluent of incomplete combustion processes of organic materials and indiscriminant discharge of untreated effluent in the river from Sharada and Challawa Industrial estate in the Kano city.
The analytical results revealed that some chemical are presents in water at significantly very high levels at Zamawa village which is very close to Challawa industrial estate and also the main effluent discharge point.This also means that pollutants could possibly affect the ground water quality of the villages that falls within the study area.

Conclusion and Recommendations
In conclusion, it can be said that industrial activities and effluent had impact on Challawa River basin and its environs especially those that are live in the immediate surroundings.The water resources in the study area are not properly managed.This is an indication that there is failure in the adoption of pollution abatement measures in the area.
Arising from the findings of this research, the following recommendations were made:-There should be a regular monitoring and evaluation of water, fishes and crops quality in the study area and water development should go hand in hand with water quality consideration.
The industries should treat their liquid properly using modern equipment.
The industries should construct sanitary land fill to dispose their liquid and solid waste properly instead of dumping openly in their premises and water bodies This research only checked the impact the industries has on environment with reference to surface water.It is also recommended that further work to be carried out in the future to check the impact on air quality It is important to initiate campaign, to inform the people on the level of water, crops and fish contamination and the sanitation steps to be followed for ensuring safe drinking water.
The public at large should be educated on the possible impact associated with living around or nearby industrial site and its consequence.
People of the communities around the industrial estate should be employed in order to give them a sense of belonging and job opportunity.

Figure 1 :
Figure 1: River Challawa showing the study area

Figure 1 . 1
Figure 1.1 Chromatographic illustration of Water Samples A00, A1, A2 and A3 at the Upstream of Challawa River during Dry Season ND -Indicates not detected RT -Retention time of each of the compound in the samples % Area -Percentage area the chromatogram of the compound Location -The point where samples collected along the trench of the river Challawa Analysis of Variance was obtained by Bartlett's test performance.Means values PAHs recorded in water samples collected from the various sampling points were compared and tested at 95% confidence.The difference was found to be significant (p < 0.05).

Table 1 .
Concentration (mg/l) of PAH and PCBs detected in Water Samples Collected at Challawa River during Dry The point where samples collected along the trench of the river Challawa Conc (mg/l) -The concentration of organic pollutants obtained from the % Area of the chromatogram Sample Code -The 2 -3 letters of the acronyms is the name given to the samples during laboratory analysis The concentration of organic pollutants obtained from the % Area of the chromatogram Sample Code -The 2 -3 letters of the acronyms is the name given to the samples during laboratory analysis ND -Indicates not detected RT -Retention time of each of the compound in the samples % Area -Percentage area the chromatogram of the compound Location -ND -Indicates not detected RT -Retention time of each of the compound in the samples % Area -Percentage area the chromatogram of the compound Location -The point where samples collected along the trench of the river Challawa Conc (mg/l) -

Table 3 :
Concentration (mg/l) of PAH and PCBs detected in Water Samples Collected at Challawa River during Dry The concentration of organic pollutants obtained from the % Area of the chromatogram Sample Code -The 2 -3 letters of the acronyms is the name given to the samples during laboratory analysis ND -Indicates not detected RT -Retention time of each of the compound in the samples % Area -Percentage area the chromatogram of the compound Location -The point where samples collected along the trench of the river Challawa Conc (mg/l) -

Table 4 :
Concentration (mg/l) of PAH and PCBs detected in Water Samples Collected at Challawa River during Retention time of each of the compound in the samples % Area -Percentage area the chromatogram of the compound Location -The point where samples collected along the trench of the river Challawa Conc (mg/l) -The concentration of organic pollutants obtained from the % Area of the chromatogram Sample Code -The 2 -3 letters of the acronyms is the name given to the samples during laboratory analysis

Table 5 :
Concentration (mg/l) of PAH and PCBs detected in Water Samples Collected at Challawa River during