Bowman, JC, Zhou, JL & Readman, JW 2002, 'Sediment–water interactions of natural oestrogens under estuarine conditions', Marine Chemistry, vol. 77, no. 4, pp. 263-276.
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The natural human female hormones oestrone and 17β-oestradiol have been implicated in the disruption of endocrine systems in some wildlife adjacent to sewage effluents. The sorption behaviour of these two compounds under estuarine conditions was studied by spiking either 2.55 μg of oestrone or 2.65 μg of 17β-oestradiol in kinetic experiments. In equilibrium experiments, 3 ng of oestrone or 3.2 ng of 17β-oestradiol was added in each of the centrifuge tubes. Sorption onto sediment particles was relatively slow, with sorption equilibrium being reached in about 70 and 170 h for oestrone and 17β-oestradiol, respectively. The effects of a variety of environmental parameters on sorption were studied including salinity, sediment concentration (SC), the presence of a third phase, particle size and, also, surfactant concentrations. Results show that although salinity did not induce any statistically significant effect on the sorption of 17β-oestradiol, it did statistically enhance the sorption of oestrone, and a salting constant of 0.3 1 mol-1 was derived. The partition coefficient for both compounds decreased with increasing sediment concentration, a phenomenon that has been widely reported and attributed to the presence of colloids (which could enhance dissolved concentrations). In this paper, the true partition coefficients for sediment particles (Kptrue) and colloidal particles (Kctrue) have been calculated, and a Kptrue value of 141 and 102 ml g-1 was obtained for oestrone and 17β-oestradiol, respectively. In addition, Kctruevalues for oestrone (222 × 102 ml g-1) and 17β-oestradiol (135 × 102 ml g-1) were two orders of magnitude higher than their respective Kptrue values, suggesting that the colloidal particles are significantly stronger sorbents for natural oestrogens than sediment particles. Particles of different sizes were found to have different partition coefficients due to the strong relationships between partition coefficients for the two compounds a...
Bowman, JC, Zhou, JL & Readman, JW 2002, 'Sorption and desorption of benzo(a)pyrene in aquatic systems', Journal of Environmental Monitoring, vol. 4, no. 5, pp. 761-766.
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The sorptive behaviour of polycyclic aromatic hydrocarbons (PAHs) is critical to controlling their transport, fates and effects in the environment. Experiments are described which detail the behaviour of a model compound (benzo(a)pyrene) under simulated aquatic conditions. The kinetics of sorption were comparable to those of other PAH compounds. The sorption equilibrium was extensively studied and found to be affected by several key parameters, notably sediment concentration. The sorption coefficient decreased substantially with the sediment concentration, from 9580 ml g-1 at a sediment concentration of 0.067 g 1-1 to 1110 ml g-1 at a sediment concentration of 9.8 g 1-1. The results are consistent with previous reports and often explained by the presence of colloids. In this paper the dry weight concentration of colloids was determined and used for deriving the true sorption coefficient, which is up to an order of magnitude higher than the observed partition coefficient. The sorption of benzo(a)pyrene was also dependent on some of the particle properties, and the sorption coefficient was found to increase with the organic carbon content and specific surface area of sediment particles. The desorption of benzo(a)pyrene from sediment was shown to be relatively rapid, with implications for the potential remobilisation of benzo(a)pyrene and similar compounds.
Chang, S 2002, 'Experimental assessment of filtration of biomass with transverse and axial fibres', Chemical Engineering Journal, vol. 87, no. 1, pp. 121-127.
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Chang, S, Fane, AG & Vigneswaran, S 2002, 'Modeling and optimizing submerged hollow fiber membrane modules', AIChE Journal, vol. 48, no. 10, pp. 2203-2212.
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AbstractThe filtration behavior of submerged hollow fiber membranes with constant permeate flow operational mode was modeled on two different conditions: the maximum initial flux along the fiber is smaller than the critical flux (Jimax < Jcr); the maximum initial flux along the fiber is greater than the critical flux, but the averaged imposed flux is smaller than the critical flux (Jimax > Jcr but Jmi < Jcr). When the maximum initial flux along the fiber is lower than the critical flux, no particle deposition occurs and the flux distribution can be characterized by a dimensionless parameter ξ = 4LRR. On the other hand, for Jmi < Jcr and Jimax > Jcr, a steady state can be achieved after some initial deposition. The theoretical model shows that the filtration resistance caused by the initial deposition can be affected by Jmi/Jcr and fiber characteristics (L, Ri and Rm) and becomes significant for narrow and long fibers with a high Jmi/Jcr. The models were also used to determine the optimal fiber length and radius for the submerged hollow fiber module. The simulation suggests that the optimal fiber lumen radius for fiber lengths of 0.5–3 m is 0.2–0.35 mm. These results should be relevant to the design of submerged hollow fiber modules.
Chapman, H, Vigneswaran, S, Ngo, HH, Dyer, S & Ben Aim, R 2002, 'Pre-flocculation of secondary treated wastewater in enhancing the performance of microfiltration', DESALINATION, vol. 146, no. 1-3, pp. 367-372.
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In this study, a new design of static floating medium flocculator was examined for its ability to remove suspended solids, organics and phosphorus. The floating medium flocculator also produced uniform microflocs, which could be removed easily by cross flow microfiltration. Flocs formed enhanced the permeate flux of microfiltration. The floating medium flocculator was able to be operated at high velocities of up to 40 m/h, producing filterable flocs of around 20 μm. Using a filter bed depth of 1m, the floating medium flocculator was able to remove 45% of suspended solids, to as low as 1.3 mg/L; 83% of turbidity, achieving values <1 NTU; 97% of phosphorus, reducing orthophosphate to 0.07 mg/L and 45% of organics, to as low as 1.02 ppm C total organic carbon (TOC). A periodic backwash for duration of 1 min every 90 min enabled the floating medium flocculator to run continuously without termination. A series of experiments was conducted with a combined system of flocculation-microfiltration to assess its capability in removing solids and organics. The improvement of flux by the pre-flocculation was also investigated. The purpose of the floating medium flocculator was to produce filterable flocs and also removal of solids and organics. The critical flux of kaolin clay suspension of 10-100 mg/L was measured with a 0.2 μm membrane, in the presence of 0-4 mg/L of fulvic acid. The pretreatment of flocculation leads to 50% removal of organics, while producing uniform microflocs of 13-16 μm. It enhanced the critical flux by 70% and resulted in a further 30-70% removal of organics by microfiltration.
Jegatheesan, V, Lamsal, PR, Visvanathan, C, Ngo, HH & Shu, L 2002, 'Effect of natural organic compounds on the removal of organic carbon in coagulation and flocculation processes', Water Supply, vol. 2, no. 5-6, pp. 473-479.
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Natural organic matter (NOM) in water contains organic compounds that are both hydrophobic and hydrophilic with a wide range of molecular weights. It is composed of non-homogeneous organic compounds such as humic substances, amino acids, sugars, aliphatic and aromatic acids, and other chemical synthetic organic matters. NOM in water is a major concern not only because of its contribution to the formation of disinfection by-products (DBPs) and taste and odor, but also its influence on the demand for coagulants and disinfectants, the removal efficiency of water treatment processes, etc. This research aims at identifying the influence of NOM in coagulation and flocculation processes in order to optimize the coagulation and flocculation conditions. In this study, pretreated pond water was used as the source water. It was observed from the experimental results that:The optimum pH for coagulation to remove NOM is around 7.The optimum alum dose at this pH can vary from 125-1,225 mgl-1 when the TOC is increased from 4 to 25 mgl-1.The presence of secondary compounds such as Ca2+, Mg2+ divalent cations had no significant effect on the removal of organic matter.The presence of clay increased the organic removal by 15%.The organic compound with higher molecular weight has higher removal affinity in coagulation process.Floc size and settling velocity of floc and sludge production all increased with the increase in NOM concentration. From the results of Capillary Suction Time (CST) tests, the floc formed with lower TOC readily released the water to make the dewatering process easier.The organic removal efficiency was significantly different for natural water containing non-homogeneous organic compounds compared to the synthetic water containing humic acid only (homogeneous organic matter). For example, the NOM removal efficiency was 80% for the synthetic water containing humic acid with TOC of 7 mgl-1 at pH 7; but the NOM remov...
Kalam, MA & Majsuki, HH 2002, 'Use of an additive in biofuel to evaluate emissions, engine component wear and lubrication characteristics', Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering, vol. 216, no. 9, pp. 751-757.
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This paper presents the results of experiments carried out to evaluate the effect of adding an anticorrosion additive to blended biofuel and lubricating oil on emissions, engine component wear and lubrication characteristics. The blended biofuels consist of 7.5 and 15 per cent palm olein (PO) with ordinary diesel oil (OD). Pure OD was used for comparison purposes. Exhaust emission gases such as NOx, CO and hydrocarbons (HCs) were measured by an exhaust emission analyser for engine operation on 50 per cent throttle at speeds of 800-3600 r/min. To measure engine component wear and lubricating oil characteristics, the engine was operated at 50 per cent throttle at a speed of 2000 r/min for a period of 100 h with each of the fuel samples. The same lubricating oil, conventional SAE 40, was used in all the fuels. A multielement oil analyser (MOA) was used to measure the increase in wear of metals (Fe, Cu, Al, Pb) and the decrease in lubricating oil additives (Zn, Ca) in the lubricating oil used. An ISL automatic Houillon viscometer (ASTM D445) and potentiometric titration (ASTM D2896) were used to measure viscosity and total base number (TBN) respectively. The results show that the addition of anticorrosion additive with biofuel and lubricating oil improves the emission and engine wear characteristics; both the exhaust emission gases (NOx, CO and HCs) and the wear of metals (Fe, Cu, Al and Pd) decrease with the blended fuels in comparison with the base fuel OD. Detailed results, including engine brake power, are discussed.
Kalam, MA & Masjuki, HH 2002, 'Biodiesel from palmoil—an analysis of its properties and potential', Biomass and Bioenergy, vol. 23, no. 6, pp. 471-479.
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Kim, SH, Ngo, HH, Chaudhary, D, Kim, JC, Vigneswaran, S & Moon, H 2002, 'Characterization procedure for adsorption of DOC (Dissolved Organic Carbon) from synthetic wastewater', KOREAN JOURNAL OF CHEMICAL ENGINEERING, vol. 19, no. 5, pp. 888-894.
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Laroussi, M, Dobbs, FC, Wei, Z, Doblin, MA, Ball, LG, Moreira, KR, Dyer, FF & Richardson, JP 2002, 'Decontamination of water by excimer UV radiation', IEEE TRANSACTIONS ON PLASMA SCIENCE, vol. 30, no. 4, pp. 1501-1503.
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Water is one of the most important substances on which life depends. However, water may also serve as a medium by which disease is spread to humans, animals, and plants. Therefore, the biological decontamination of this vital substance is of paramount im
Mahlia, TMI 2002, 'Emissions from electricity generation in Malaysia', Renewable Energy, vol. 27, no. 2, pp. 293-300.
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Mahlia, TMI, Masjuki, HH & Choudhury, IA 2002, 'Development of energy labels for room air conditioner in Malaysia: methodology and results', Energy Conversion and Management, vol. 43, no. 15, pp. 1985-1997.
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Mahlia, TMI, Masjuki, HH & Choudhury, IA 2002, 'Potential electricity savings by implementing energy labels for room air conditioner in Malaysia', Energy Conversion and Management, vol. 43, no. 16, pp. 2225-2233.
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Mahlia, TMI, Masjuki, HH & Choudhury, IA 2002, 'Theory of energy efficiency standards and labels', Energy Conversion and Management, vol. 43, no. 6, pp. 743-761.
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Mahlia, TMI, Masjuki, HH, Choudhury, IA & Ghazali, NNN 2002, 'Economical and environmental impact of room air conditioners energy labels in Malaysia', Energy Conversion and Management, vol. 43, no. 18, pp. 2509-2520.
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Masjuki, HH, Mahlia, TMI, Choudhury, IA & Saidur, R 2002, 'Potential CO2 reduction by fuel substitution to generate electricity in Malaysia', Energy Conversion and Management, vol. 43, no. 6, pp. 763-770.
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Maskaoui, K, Zhou, JL, Hong, HS & Zhang, ZL 2002, 'Contamination by polycyclic aromatic hydrocarbons in the Jiulong River Estuary and Western Xiamen Sea, China', Environmental Pollution, vol. 118, no. 1, pp. 109-122.
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The distribution of 16 polycyclic aromatic hydrocarbons (PAHs) was determined in water, sediment and pore water of the Jiulong River Estuary and Western Xiamen Sea, China. Total PAH concentrations varied from 6.96 to 26.9 μg/l in water, 59-1177 ng/g dry weight in surficial sediments, and 158-949 μg/l in pore water. The PAHs were present in higher levels in pore water than in surface water, due possibly to higher concentrations of dissolved organic carbon or colloids with which the hydrophobic pollutants were strongly associated. Such a concentration gradient implies a potential flux of pollutants from sediment pore water to overlying water. The levels of PAHs in water and pore water were significantly higher than those found in 1998, suggesting recent inputs of these compounds into the area and re-working of sediment phase. The composition pattern of PAHs in the three phases was dominated by high molecular weight PAHs, in particular 5-ring PAHs. The salinity profile of dissolved PAHs suggested that they all behaved non-conservatively due to deviation from the theoretical dilution line. No correlation was found between PAH concentrations in sediment and those in pore water, and the correlation between the partition coefficients of PAHs and sediment organic carbon content was not significant, suggesting the complexity of the partition behaviour of PAHs. As a result of high PAH concentrations in water and pore water, it is likely that they may have caused mortality to certain exposed organisms. © 2002 Elsevier Science Ltd. All rights reserved.
Ngo, HH, Vigneswaran, S, Hu, JY, Thirunavukkarasu, O & Viraraghavan, T 2002, 'A comparison of conventional and non-conventional treatment technologies on arsenic removal from water', Water Supply, vol. 2, no. 5-6, pp. 119-125.
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In this study, four treatment methods were used to remove arsenic from water, namely: (i) chemical precipitation, (ii) arsenic adsorption onto iron-oxide-coated sand, (iii) high-rate saturated floating-medium flocculator/filter and (iv) membrane hybrid system (adsorption-microfiltration). The results indicated that more than 90% of total arsenic was removed by using FeCl3 (40 mg/L) as coagulant. The removal efficiency was 10% lower when polysilicato-iron (PSI, 2.5 mg/L) was used as a flocculant. The results of both the batch and column adsorption studies showed that iron-oxide-coated sand can effectively be used to achieve very high levels of arsenic removal (less than 5 μm/L as As in drinking water). Arsenic was removed up to 78% from the packed polystyrene beads filter with in-line FeCl3 addition at a high loading rate of 30 m3/m2.h. When powder activated carbon (PAC) was used in the membrane hybrid system, 87% removal of arsenic was achieved. A mixing time of 2.7 min with the mixing intensity of 87.8 s-1 were used. A very high filtration (permeate flux of 760 L/m2.h) was observed with a membrane of pore size of 0.2 μm.
Ralph, PJ & Short, FT 2002, 'Impact of the wasting disease pathogen, Labyrinthula zosterae, on the photobiology of eelgrass Zostera marina', MARINE ECOLOGY PROGRESS SERIES, vol. 226, no. N/A, pp. 265-271.
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Labyrinthula zosterae is clearly shown to be a primary pathogen of eelgrass Zostera marina L., not merely a secondary infection of senescent leaves or an indication of decomposition, The results of this investigation using a Diving-PAM fluorometer indicate that the regions of tissue photosynthetically compromised by Labyrinthula are substantially larger than previously thought. Labyrinthula moves through Zostera marine tissue at a rate of up to 0.8 h-1 during daylight periods. The photosynthetic efficiency of apparently healthy green leaf tissue can be reduced by almost 50% in areas up to 3 mm from a necrotic region infected with Labyrinthula. Once a necrotic spot expands to bisect the eelgrass leaf, the condition of all acropertal tissue diminished; lead tissue up to 5 cm away has severely reduced photosynthetic activity.
Ralph, PJ, Gademann, R, Larkum, AWD & Kuhl, M 2002, 'Spatial heterogeneity in active chlorophyll fluorescence and PSII activity of coral tissues', MARINE BIOLOGY, vol. 141, no. 4, pp. 639-646.
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Chlorophyll-a fluorescence was measured in six species of coral, using pulse-amplitude-modulated fluorometers employing fibre-optic probes with diameters of 8 mm, 1 mm and 140 μm. The 8-mm probe integrated responses over a large area, giving more weight to coenosarc than polyp tissue for Acropora nobilis. With 1-mm and 140-μm fibre-optic probes, the photosynthetic responses of zooxanthellae in the coenosarc and the polyp tissue of Acropora nobilis were distinguished. The polyp tissue exhibited a lower maximum in relative electron transport rate than did the coenosarc tissue, and was subject to down-regulation at higher irradiances. Coenosarc and polyp tissue (both containing zooxanthellae) showed a wide range of responses in the other corals. Down-regulation of photosynthesis in a single polyp of Pocillopora damicornis was followed after exposure to moderate irradiance, with recovery occurring over a further 4 h of shade conditions. All the corals (Acropora millepora, A. nobilis, Cyphastrea serailia, Montipora tuberculosa, Pocillopora damicornis and Porites cylindrica) showed evidence of strong down-regulation of photosynthesis under high irradiance, and little evidence of photoinhibitory damage to photosystem II.
Ralph, PJ, Polk, SM, Moore, KA, Orth, RJ & Smith, WO 2002, 'Operation of the xanthophyll cycle in the seagrass Zostera marina in response to variable irradiance', JOURNAL OF EXPERIMENTAL MARINE BIOLOGY AND ECOLOGY, vol. 271, no. 2, pp. 189-207.
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Changes in the photobiology and photosynthetic pigments of the seagrass Zostera marina from Chesapeake Bay (USA) were examined under a range of natural and manipulated irradiance regimes. Photosynthetic activity was assessed using chlorophyll-a fluorescence, and photosynthetic pigments were measured by HPLC. Large changes in the violaxanthin, zeaxanthin, and antheraxanthin content were concomitant with the modulation of non-photochemical quenching (NPQ). Photokinetics (Fv/Fm, rapid light curves (RLC), and non-photochemical quenching) varied as a result of oscillating irradiance and were highly correlated to xanthophyll pigment content. Zeaxanthin and antheraxanthin concentrations increased under elevated light conditions, while violaxanthin increased in darkened conditions. Unusually high concentrations of antheraxanthin were found in Z. marina under a wide range of light conditions, and this was associated with the partial conversion of violaxanthin to zeaxanthin. These results support the idea that xanthophyll intermediate pigments induce a photoprotective response during exposure to high irradiances in this seagrass.
Schreiber, U, Gademann, R, Bird, P, Ralph, PJ, Larkum, AWD & Kuhl, M 2002, 'Apparent light requirement for activation of photosynthesis upon rehydration of desiccated beachrock microbial mats', JOURNAL OF PHYCOLOGY, vol. 38, no. 1, pp. 125-134.
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Photosynthetic electron transport of beachrock microbial mats growing in the intertidal zone of Heron Island (Great Barrier Reef, Australia) was investigated with a pulse amplitude modulation chl fluorometer providing four different excitation wave-lengths for preferential excitation of the major algal groups (cyanobacteria, green algae, diatoms/dinoflagellates). A new type of fiberoptic emitter-detector unit (PHYTO-EDF) was used to measure chl fluorescence at the sample surface. Fluorescence signals mainly originated from cyanobacteria, which could be almost selectively assessed by 640-nm excitation. Even after desiccation for long time periods under full sunlight, beachrock showed rapid recovery of photosynthesis after rehydration in the light (t1/2 ∼ 15 min). However, when rehydrated in the dark, the quantum yield of energy conversion of PSII remained zero over extended periods of time. Parallel measurements of O2 concentration with an oxygen microoptode revealed zero oxygen concentration in the surface layer of rehydrated beachrock in the dark. Upon illumination, O2 concentration increased in parallel with PSII quantum yield and decreased again to zero in the dark. It is proposed that oxygen is required for preventing complete dark reduction of the PSII acceptor pools via the NADPH-dehydrogenase/chlororespiration pathway. This hypothesis is supported by the observation that PSII quantum yield could be partially induced in the dark by flushing with molecular oxygen.
Thiruvenkatachari, R, Ngo, HH, Hagare, P, Vigneswaran, S & Aim, RB 2002, 'Flocculation—cross-flow microfiltration hybrid system for natural organic matter (NOM) removal using hematite as a flocculent', Desalination, vol. 147, no. 1-3, pp. 83-88.
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Zhang, Z, Dai, M, Hong, H, Zhou, JL & Yu, G 2002, 'Dissolved insecticides and polychlorinated biphenyls in the Pearl River Estuary and South China Sea', Journal of Environmental Monitoring, vol. 4, no. 6, pp. 922-928.
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Persistent organic pollutants (POPs) such as organochlorine (OCl) insecticides and polychlorinated biphenyls (PCB), together with the new generation of organophosphorus (OP) insecticides, are of global concern, due to their widespread occurrence, persistence, bioaccumulation and hormone disruption potential. This paper represents an attempt to study the source and transportation of such pollutants in estuarine and coastal environments as an integrated ecosystem, by determining the levels of 18 OCl insecticides, 21 PCB congeners, and 17 OP insecticides in the Pearl River Estuary and South China Sea. The total concentrations varied from 126-1198 ng 1-1 for OCl insecticides, 33.38-1064 ng 1-1 for PCB congeners, and 4.44-6356 ng 1-1 for OP insecticides in the Pearl River Estuary. In comparison, their levels in the South China Sea were significantly lower, varying from 57.09-202 ng 1-1 for OCl insecticides, 21.72-144 ng 1-1 for PCBs, and 1.27-122 ng 1-1 for OP insecticides, respectively. The predominance of β-HCH in HCHs, and DDE in DDTs in all water samples was clearly observed, suggesting β-HCH and DDE's resistance to further degradation. The PCBs were dominated by those with 3-6 chlorines. The distribution characteristic of OP insecticides shows that five compounds (methamidophos, dimethoate, malathion, dichlorvos and omethoate) accounted for 56% and 72% of the total OP insecticide concentration. The relationship between pollutant concentrations and salinity in the estuary showed that they were all removed during the mixing process, therefore behaving non-conservatively.
Zhang, Z, Hong, H, Zhou, JL, Yu, G, Chen, W & Wang, X 2002, 'Transport and fate of organochlorine pesticides in the River Wuchuan, Southeast China', Journal of Environmental Monitoring, vol. 4, no. 3, pp. 435-441.
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Persistent organic pollutants (POPs) such as chlorinated pesticides are of global concern due to their widespread occurrence, persistence, bioaccumulation and toxicity to animals and human. This paper summarises recent research on 18 chlorinated pesticides in an important catchment in China, by determining their concentrations and behaviour in water, sediment, soil and plants. The concentrations of the total pesticides were in the ranges 187-893 ng 1-1 in river water, 8.53-210 ng g-1 dry weight in soil, 2.66-13.45 ng g-1 dry weight in river sediment, and 651-2823 ng g-1 dry weight in plants. The predominance of β-HCH as the major isomer of HCHs in all water, soil, sediment and plant samples was clearly observed, due to β-HCH's resistance to biodegradation. On average β-HCH accounted for 44%, 53%, 50%, and 46% of the total HCH concentration in water, soil, sediment and plant, respectively. Of the DDTs, DDE accounted for 48%, 43%, 53%, 55% of the total DDT, which suggested that DDT had been transformed to its metabolites, DDE and DDD, of which DDE was the more stable. The chlorinated pesticide levels in the River Wuchuan were generally below the guideline values in China, but some sites displayed levels in excess of EC Environmental Quality Standards for HCHs and DDTs. The results therefore provide important information on the current contamination status of a key agricultural watershed in China, and point to the need for urgent actions to evaluate the long-term fate and toxicity of such persistent compounds and an appropriate remediation strategy.
Zhang, ZL, Hong, HS, Zhou, JL & Yu, G 2002, 'Occurrence and behaviour of organophosphorus insecticides in the River Wuchuan, southeast China', Journal of Environmental Monitoring, vol. 4, no. 4, pp. 498-504.
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Organophosphorus (OP) insecticides are used worldwide, yet their persistence in the environment is not well understood. This paper summarises recent research on 17 OP insecticides in the River Wuchuan, an important catchment in China, by determining their concentrations in water, soil, sediment and plants by gas chromatography with flame photometric detection (GC-FPD). The concentrations of the total OP insecticides ranged from 92.77 to 229 ng 1-1 in river water, 1.61 to 9.93 ng g-1 dry weight in soil, 1.24 to 7.56 ng g-1 dry weight in sediment and 75.28 to 326 ng g-1 dry weight in plants. There was a relatively high abundance of methamidophos, dichlorvos, malathion, omethoate and dimethoate in all water, soil, sediment and plant samples. On average, these five compounds collectively accounted for 64%, 71%, 71% and 54% of the total OP insecticide concentration in water, soil, sediment and plants, respectively, which was similar to the composition of OP insecticides in application formulations used in our study area and in China as a whole. The results therefore reflect the application pattern to some extent, and suggest that the sources of the OP insecticides are mainly from current usage. When compared with other areas, the levels of OP insecticides in the River Wuchuan were moderate. The animal and human risks from exposure to OP insecticides in water and plants were evaluated against relevant threshold values. The results therefore provide important information on the current contamination status of a key agricultural watershed in China, and point to the need for urgent action to control the use of some excessively applied and potentially persistent agrochemicals, such as methamidophos, omethoate and dimethoate.
Zhang, ZL, Hong, HS, Zhou, JL, Dai, MH, Maskaouib, K & Chen, WQ 2002, 'Contamination by organochlorine pesticides in the estuaries of southeast China', Chemical Research in Chinese Universities, vol. 18, no. 2, pp. 153-160.
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Persistent organic pollutants (POPs) such as organochlorine pesticides are of global concern due to their widespread occurrence and persistence. This paper reports recent research studying the distribution and fate of organochlorine pesticides in the Jiulong River, the Minjiang River and the Pearl River estuaries in Southeast China. Eighteen organochlorine pesticides were extracted from water, pore water and sediment samples, followed by analysis by GC-ECD. The results showed that the contamination levels were similar in these three estuaries. The levels of the total organochlorine pesticides in porewater were significantly higher than those in surface water, due to the high affinity of these hydrophobic compounds for sediment phase. Among the hexachlorocy-clohexane (HCH) compounds, β-HCH was found to be the most important isomer. The analysis of 1, 1, 1-trichloro-2, 2-bis-chlorophyenyl-ethane (DDT) and its metabolites showed that 1, 1-dichloro-2 [o-chloropheny1]-2 [p-chlorophenyl]-ethylene (DDE) was dominant in the group.
