Development of a human community are not without changes in its environment. Such changes result in either beneficial or adverse effects on human health. In Malaysia, in the wake of the New Economic Policy aimed at the redressing of the poor population and income distribution, development of the nation has brought about various changes in the environment. Some of these changes have elevated basic public health problems, while others, particularly new agricultural practices and industrialisation programmes with urbanisation trends, have brought a new set of problems due to water pollution and sanitation. Various measures are being taken to protect and to improve the environment so that progress can be realised with minimum adverse effects. This also calls for assistance from international sources, in terms of expertise, training and funds.
Matched MeSH terms: Water Pollutants, Chemical/adverse effects
Solid-phase extraction (SPE) of organochlorine pesticide residues from environmental water samples was evaluated using octadecyl (C18)-bonded porous silica. The efficiency of SPE of these pesticide residues from reagent water samples at 1-5 micrograms dm-3 levels was compared with those obtained by solvent extraction with hexane and Freon TF (trichlorotrifluoroethane). Average recoveries exceeding 80% for these organochlorine pesticides were obtained via the SPE method using small cartridges containing 100 mg of 40 microns C18-bonded porous silica. The average recovery by solvent extraction with hexane and Freon TF exceeded 90% in both instances. It was concluded that the recoveries and precision for the SPE of organochlorine pesticides were poorer than those for the solvent extraction method. Organochlorine pesticide residue levels in environmental water samples from two major rivers flowing through predominantly rice-growing areas were monitored by gas chromatography using the solvent extraction method with hexane. Exceptionally high levels of organochlorine pesticide residues such as BHC, DDT, heptachlor, endosulfan and dieldrin were found in these water samples.
Matched MeSH terms: Water Pollutants, Chemical/analysis*
Trace elements, such as As, Co, Cr, Hg, Sb, and Zn, were determined by neutron activation analysis (NAA), whereas Cd, Cu, and Pb were determined by graphite furnace atomic absorption spectroscopy (GFAAS) in clam, crab, prawn, swamp cerith, and mussel samples after digestion by microwave heating under controlled conditions before eluting the solutions through a column of a chelating resin, Chelex-100. The standard used in the determination of percentage volatile elements retained by microwave digestion and also in the activation process was Lobster Hepatopancreas TORT-1, whereas known mixed standards were prepared from nitrate salts to determine the efficiency of the separation procedure at a controlled pH. Mercury and lead detected in crabs exceeded the maximum permissible level. Some species also showed a high affinity toward certain elements, and their levels of accumulation in the tissues of these species corresponded with the concentration of these elements in sediments, especially at sites in the vicinity of an industrial zone.
Matched MeSH terms: Water Pollutants, Chemical/analysis*
Three species of tropical estuarine invertebrates were exposed to copper sulfate and cadmium chloride to investigate their potential as test specimens for sediment toxicity assays in the South-east Asian regions. The larvae of the reef sea urchin (Diadema setosum), the oyster (Crassostrea iradalei), and the mud crab (Scylla seratta Forskall) were used in the 48-hr assays with copper and cadmium as reference toxicants. In addition the sea urchin were tested for end point measurements at different stages of the larval development and a 60-min sperm bioassay. The study revealed that the sea urchin first cleavage, which is an assay end point and which takes place about 1 hr after fertilization, was the most sensitive stage for both toxicants, with copper being more toxic than cadmium. Sensitivity comparisons between the three invertebrate larvae revealed the mud crab zoea larvae to be most sensitive for cadmium with an LC50 value of 0.078 microgram/ml, while the sea urchin was more sensitive for copper, with EC50 values of 0.01 microgram/ml at the first cleavage stage and 0.04 microgram/ml at the pluteus larva stage. All the invertebrates tested gave responses that made them suitable test organisms for metal bioassays in the tropical estuarine environment.
Matched MeSH terms: Water Pollutants, Chemical/toxicity*
A study on the kinetics of accumulation and depuration of Zn, Cu, Pb and Cd by the oysters (Crassostrea iredalei and Crassostrea belcheri) cultured at two locations in the Merbok Estuary, Malaysia was conducted. A first-order kinetic model was employed to fit the experimental data in order to estimate the rate constants for uptake and elimination processes and to predict the bioconcentration factors (BCF). Among the four metals studied, only the Zn accumulation process could not be modelled using first-order kinetics. The elimination rate constants estimated from depuration data for C. iredalei are found to be much greater than those from accumulation data. The results suggest that the values of kinetic parameters and BCFs derived under conditions of both aqueous and dietary exposure are probably more site- than species-specific.
Matched MeSH terms: Water Pollutants, Chemical/pharmacokinetics*
Heavy metals in the aquatic environment have to date come mainly from naturally occurring geochemical materials. However, this has been enhanced by human activity such as gold mining in the case of heavy metal pollution in Sg Sarawak Kanan. The high suspended solid loads in the river have quite efficiently removed most soluble metals from the water and trapped them in the bottom sediment. Three freshwater mollusc species were collected at the point source of the heavy metal pollutants and analysed for the heavy metal contents in their tissues and shells. Two of the mollusc species (Brotia costula and Melanoides tuberculata) are purely freshwater species while the Clithon sp. nr retropictus is able to survive in fresh and brackish water environments. The Brotia costula and the Clithon sp. are the edible species which are sold in the market. Accumulation of As, Cu, Fe, Se and Zn in all the three mollusc species were determined and the level of As in the tissues of Brotia costula and the Clithon sp. was much higher than the permissible level for human consumption. The mollusc species also demonstrated different preferences for the uptake of different metals. Variations in the heavy metal contents in the shell and tissues of the same species were also observed.
Matched MeSH terms: Water Pollutants, Chemical/pharmacokinetics*
Speciation of arsenic and selenium was carried out on water samples taken from rivers used as water intake points in the vicinity of landfill areas used for land-based waste disposal system. Leachates from these landfill areas may contaminate the river water through underground seepage or overflowing, especially after a heavy downpour. Preconcentration of the chemical species was done using a mixture of ammonium pyrrolidinethiocarbamate-chloroform (APDTC-CHCl3). Because only the reduced forms of both arsenic and selenium species could be extracted by the preconcentrating mixture, suitable reducing agents such as 25% sodium thiosulfate for As(III) and 6M HCl for Se(IV) were used throughout the studies. Care was taken to exclude the interfering elements such as the alkali and alkali earth metals from the inorganic arsenic and selenium species by introducing 12% EDTA solution as the masking agent. The extracted mixture was irradiated in a thermal neutron flux of 4 x 10(12)/cm/s from a TRIGA Mk.II reactor at the Malaysia Institute of Nuclear Technology Research (MINT). Gamma rays of 559 keV and 297 keV from 76As and 75Se, respectively, were used in the quantitative determination of the inorganic species. Mixed standards of As(III) and Se(IV) used in the percentage efficiency procedure were prepared from salts of Analar grade. The water quality evaluation was viewed from the ratio of the inorganic species present.
Matched MeSH terms: Water Pollutants, Chemical/analysis*
Landfills are sources of groundwater and soil pollution due to the production of leachate and its migration through refuse. This study was conducted in order to determine the extent of groundwater and soil pollution within and around the landfill of Seri Petaling located in the State of Selangor, Malaysia. The condition of nearby surface water was also determined. An electrical resistivity imaging survey was used to investigate the leachate production within the landfill. Groundwater geochemistry was carried out and chemical analysis of water samples was conducted upstream and downstream of the landfill. Surface water was also analyzed in order to determine its quality. Soil chemical analysis was performed on soil samples taken from different locations within and around the landfill in the vadose zone (unsaturated zone) and below the water table (in the soil saturated zone). The resistivity image along line L-L1 indicated the presence of large zones of decomposed waste bodies saturated with highly conducting leachate. Analysis of trace elements indicated their presence in very low concentrations and did not reflect any sign of heavy metal pollution of ground and surface water or of soil. Major ions represented by Na, K, and Cl were found in anomalous concentrations in the groundwater of the downstream bore hole, where they are 99.1%, 99.2%, and 99.4%, respectively, higher compared to the upstream bore hole. Electrical conductivity (EC) was also found in anomalous concentration downstream. Ca and Mg ions represent the water hardness (which is comparatively high downstream). There is a general trend of pollution towards the downstream area. Sulfates (SO4) and nitrates (NO3) are found in the area in low concentrations, even below the WHO standards for drinking water, but are significantly higher in the surface water compared to the groundwater. Phosphate (PO4) and nitrite (NO2), although present in low levels, are significantly higher at the downstream. There is no significant difference in the amount of fluoride (F) in the different locations. In the soil vadose zone, heavy metals were found to be in their typical normal ranges and within the background concentrations. Soil exchangeable bases were significantly higher in the soil saturated zone compared to the vadose zone, and no significant difference was obtained in the levels of inorganic pollutants. With the exception of Cd, the concentration ranges of all trace elements (Cu, Zn, Cr, Pb, and Ni) of Seri Petaling landfill soils were below the upper limits of baseline concentrations published from different sources.
Matched MeSH terms: Water Pollutants, Chemical/analysis*