Heavy metal accumulation and depuration may alter the effectiveness of Meretrix meretrix as a biomonitoring organism for water quality assessment. Therefore, this study was conducted to evaluate the effects of heavy metal accumulation and depuration on M. meretrix, by immersing it in Copper (Cu), Zinc (Zn), and Lead (Pb)
solutions under laboratory conditions. The results showed that M. meretrix is able to accumulate Cu, Zn, and Pb at the rate of 0.99, 21.80, and 0.57 μg/g per day, respectively, and depurates at the rate of 0.42, 23.55, and 1.01 μg/g per day, respectively. These results indicate that M. meretrix could be effectively used as a biomonitoring organism for Cu because the accumulation rate is significantly (p ≤ 0.05) higher than the depuration rate. However, this was not the case for Zn because the accumulation rate was almost similar to the depuration rate, while for Pb, accumulation or depuration did not occur in M. meretrix.
The primary source of water on many small islands is the fragile freshwater lens that floats on saline water in its shallow aquifer. The management of such a limited groundwater resource on these islands is seriously constrained by the occurrence of seawater intrusion. Sipadan Island, the renowned and only oceanic island in Malaysia, had experienced in the over-extraction of its groundwater for more than ten years to cater for freshwater demand associated with tourism activities. This paper discusses the output of modelling of seawater intrusion into the island’s aquifer using SEAWAT-2000. The findings indicated that the island’s coastal aquifer has been encroached by seawater. The infiltration of isochlor (chloride concentration) of 2.5 and 45% of seawater and freshwater mixing ratios has moved 63.4 m and 12.7 m inland from the coastline, respectively. The upconing event at the pumping well, as simulated by the three-dimensional model, showed that 14.5% of seawater-freshwater mixing ratio took place below the bottom of each well. Intensive and unregulated exploitation of groundwater from such an unconfined aquifer of the island by pumping wells contributed to the upconing. In order to protect the fresh groundwater resources in the study area from seawater intrusion, adjustment of groundwater pumping rate is needed. This study showed that the model is useful in demonstrating the mechanism and movement of freshwater-seawater interface in the island, and thus provide a powerful management tool for such an aquifer.
Groundwater is the prime source of freshwater in most small islands. A detailed groundwater and seawater chemistry study was undertaken from March 2006 to January 2007 to examine the evolution of groundwater in the shallow aquifer of Manukan Island, Sabah, Malaysia. Coastal groundwater aquifers especially for small islands are often exposed to heavy pumping and consequently to risks of seawater intrusion. Major ion chemistry analysis showed that the groundwater quality of the island experienced changes attributed to seawater intrusion. The groundwater has undergone a compositional change from Ca-rich to Na-rich which can be explained mostly by simple mixing process and cation exchange process. From the PHREEQC simulation model, calcite, dolomite and aragonite solubility showed positive mean values (0.65; 1.11; 0.51, respectively) of the saturation indices (SI) indicating supersaturation which attributed from the simple mixing and eventually cation exchange process. This information is important in protecting and remediating the disturbed aquifer situation.
Ambient groundwater samples collected from five wells in Pulau Tiga have been studied for selected physico-chemical and biological parameters to understand general water quality of the island. This preliminary study on groundwater of Pulau Tiga was undertaken to provide guidance and baseline data for future references. Two field works were undertaken in August and November 2007 to collect the groundwater samples. Groundwater samples were collected from five representatives wells at the low lying area of Pulau Tiga in order to study the in-situ parameters such as DO (dissolved oxygen), EC (electrical conductivity), TDS (total dissolved solids), pH, salinity and temperature. In general, groundwater in Pulau Tiga is moderate in conductivity (330 μS/cm – 1005 μS/cm), and serves as a vital freshwater source to both tourists and local inhabitants. However, bacteriological analysis showed that the groundwater quality was poor, with fecal coliform counts exceeding the WHO permissible limits for drinking water. Through this study, human factor was to be blame for the fecal contamination coliform where the polluted ground water might be originated from sanitation facilities located too close to the wells. The occurrence of total and fecal coliform bacteria in counts suggests poor sanitary handling and warns of the potential presence of disease-causing organisms.
A study on water quality and aquatic insects has been conducted at the Lower Kinabatangan River Catchment, Sabah,
Malaysia. The quality of water surface and aquatic insects’ composition were studied in streams near to oil palm plantation
(OP), secondary forest (SF) and oxbow lake (OB). The study also aims to identify the seasonal variation in the aquatic
insects’ composition during the weak La Niña event. A total of 135 water samples and 1678 aquatic insect individuals
(four orders and 14 families) were collected during fieldwork campaign that spanned over the inter-monsoonal period,
wet and dry seasons between October 2004 and June 2005. OP has the highest abundance of aquatic insects particularly
during the dry season. Biological indices showed that all stations were in moderate water category. The water quality
index (WQI) was calculated and indicated that the quality of the river categorised into Class II. Discriminant analysis
(DA) was employed to classify the independent variables into mutually-exclusive groups. Suspended sediment (SS) and
chemical oxygen demand (COD) were high during the wet season. Suspended sediment was high in oxbow lake and could
be a strong reason behind low abundance of aquatic insects. Precipitation anomalies were found to affect seasonal
variations of water quality and aquatic insects at the Lower Kinabatangan River.