Determination of selected organochlorine pesticide (OCP) compounds from the Jukskei River catchment area in Gauteng, South Africa

Organochlorine pesticides (OCPs) are continually detected in the environment due to their increasing applications in agriculture and industry. The presence of OCPs in the environment is not desirable since they are well known to have negative impact in humans, animals and birds. Thus, there has been a continual demand to monitor the presence of OCPs within the environment. Liquid-liquid extraction (LLE) and Soxhlet extraction (SE) methods (using dichloromethane as the extracting solvent,) were optimised and evaluated for the determination of these compounds in surface water (unfiltered and filtered) and sediment samples. The crude extracts obtained were subjected to column chromatography for clean-up. Thereafter, 1 μℓ of the cleaned extracts were injected into the GC equipped with ECD.Percentage recoveries obtained for OCPs ranged from 98.90±7.32 (2,4’-DDE) - 124.1±8.23 endosulfan II (ENDO II) % and from 98.99±5.30 (2,4’-DDE) - 121.1±0.38 (4,4’-DDE) % in spiked triply distilled water and sediment samples respectively. The levels of OCPs obtained in unfiltered environmental water samples ranged from 0.631±0.03 (γ-HCH) -1 540±0.19 ng·mℓ-1 (4,4’-DDT) while levels in filtered water samples ranged from 0.895±0.01 (γ-HCH) - 9 089±0.08 ng·mℓ-1 (HEPTA). Levels of analysed OCPs obtained in sediments ranged from 0.266±0.01 (δ-HCH) - 22 914±2.85 ng·gdw-1 (2,4’-DDE). Analytes adsorbed on the sample bottles used for water samples collection gave levels which ranged from 0.01±0.01 - 1.06±0.02 ng·mℓ-1 for OCPs.The levels obtained from the catchment were significantly higher than the water criteria values recommended by USEPA and DWAF for the protection of the aquatic environment. Levels obtained were also higher than those of other studies conducted so far in South African aquatic environments. There is, therefore, a definite pollution of the Jukskei River catchment by the OCPs studied.Keywords: OCPs, surface water, sediments, liquid-liquid extraction, GC-EC

Levels of selected alkylphenol ethoxylates (APEs) in water and sediment samples from the Jukskei River catchment area in Gauteng, South Africa

There has been a continual search to develop sensitive analytical methods for detecting and determining organic compounds such as alkylphenol ethoxylates (APEs) in environmental samples, since they occur at very low concentration levels. Studies conducted so far in some South African waters have offered little or no information on APEs. The presence of these compounds in environmental samples is not desirable and therefore, needs to be monitored. Water and sediment samples were collected from different sites in the Jukskei River catchment area in the 2005 summer and winter seasons. Liquid-liquid extraction (LLE) and Soxhlet extraction (SE) methods (using 1:1 dichloromethane and methanol as extracting solvents) were optimised, evaluated and used to determine APEs of interest in water (unfiltered and filtered) and sediment samples, respectively. Mean percentage recoveries obtained for APEs in spiked double-distilled water were between 83.1±1.0 (OPnEOS3) and 108.1±3.5 (OP) and for sediments the range was between 96.6±0.9 (OPnEOS1) and 117.1±0.6 (OPnEOS3). The concentration levels of APEs studied in unfiltered environmental water samples were in the range of 0.25(0.03) ng/mℓ (NP) to 92.7(1.11) ng/mℓ (OPnEOS3) and 0.31(0.02) ng/mℓ (NP) to 60.1(0.51) ng/mℓ (OPnEOS3) for filtered environmental water samples. Concentration levels obtained in sediments were from 1.94(0.14) ng/gdw to 941(0.50) ng/gdw (OPnEOS3). Analytes adsorbed on the sample bottle gave concentration levels which ranged from 0.02(0.02) ng/mℓ to 0.42(0.02) ng/mℓ for APEs. All the compounds studied were found at levels higher than the European Union (EU) set levels for the protection of the aquatic environment. Keywords: APEs, surface water, sediments, liquid-liquid, soxhlet, GC-FI

Source apportionment of polycyclic aromatic hydrocarbons in sediments from polluted rivers

Over the past few decades, in response to growing concerns about the impact of polycyclic aromatic hydrocarbons (PAHs) on human health, a variety of environmental forensics and geochemical techniques have emerged for studying organic pollutants. These techniques include chemical fingerprinting, receptor modeling, and compound-specific stable isotope analysis (CSIA). Chemical fingerprinting methodology involves the use of diagnostic ratios. Receptor modeling techniques include the chemical mass balance (CMB) model and multivariate statistics. Multivariate techniques include factor analysis with multiple linear regression (FA/MLR), positive matrix factorization (PMF), and UNMIX. This article reviews applications of chemical fingerprinting, receptor modeling, and CSIA; comments on their uses; and contrasts the strengths and weaknesses of each methodology.http://www.iupac.org/publications/pac/index.htmlhb2014mn201

Highly Effective Removal of Toxic Cr(VI) from Wastewater Using Sulfuric Acid-Modified Avocado Seed

Sulfuric acid modified avocado seed (ASSA), as a low-cost carbonized adsorbent, was investigated for the removal of toxic Cr­(VI) from water/wastewater in batch experiments. A low temperature (100 °C) chemical carbonization treatment was employed for the production of the adsorbent. FE-SEM and HR-TEM images revealed the formation of agglomerated and rodlike structured particles after carbonization of avocado seed. BET and TGA analyses of ASSA demonstrated its mesoporous structure and thermal stability up to 200 °C. The presence of oxo-functional groups on the ASSA surface was confirmed by ATR-FTIR and XPS studies. Adsorption of Cr­(VI) onto ASSA was highly pH dependent and found to be an optimum at pH 2.0. Adsorption isotherm results suggested that the capacity increases with an increase in temperature. Nonlinear regression analysis revealed that the Freundlich isotherm model provides a better correlation than the Langmuir isotherm model for Cr­(VI) adsorption onto ASSA. The maximum Cr­(VI) adsorption capacity of 333.33 mg/g was obtained at 25 °C, which is higher than most of the previously reported carbonized adsorbents used for Cr­(VI) removal. Adsorption kinetics was best described by the pseudo-second-order model. The presence of coexisting ions slightly affected the Cr­(VI) removal efficiency of ASSA. Experiment with real wastewater sample containing 47.34 mg/L of Cr­(VI) demonstrated that by the use of only 0.03 g/25 mL of ASSA, almost 100% removal was achieved at pH 2.0, which suggests its potential application in wastewater treatment plants. The ASSA retained its original Cr­(VI) sorption capacity up to three consecutive adsorption–desorption cycles. Finally, from XPS analysis, electrostatic attraction of Cr­(VI) species to the adsorbent and its subsequent reduction to Cr­(III) were identified as the leading removal mechanisms