Groundwater resources assessment using numerical model: a case study in low-lying coastal area

The impacts of climate change and human pressure in groundwater have been greatest threats facing small islands. This paper represents a case study of groundwater responses towards the climate change and human pressures in Manukan Island Malaysia. SEAWAT-2000 was used for the simulations of groundwater response in study area. Simulations of six scenarios representing climate change and human pressures showed changes in hydraulic heads and chloride concentrations. Reduction in pumping rate and an increase in recharge rate can alter the bad effects of overdrafts in Manukan Island. In general, reduction in pumping rate and an increase in recharge rate are capable to restore and protect the groundwater resources in Manukan Island. Thus, for groundwater management options in Manukan Island, scenario 2 is capable to lessen the seawater intrusion into the aquifer and sustain water resources on a long-term basis. The selection of scenario 6 is the preeminent option during wet season. The output of this study provides a foundation which can be used in other small islands of similar hydrogeological condition for the purpose of groundwater resources protection

Heavy metals in mangrove surface sediment of mengkabong lagoon, Sabah: Multivariate and geo-accumulation index approaches

The inter-tidal mangrove environment of Mengkabong lagoon is important as it supports the local fishing activities, nursery grounds for many fish and shellfish species, and as well as being central for ecotourism activities. The study showed that in general, the physicochemical parameters [pH, salinity and electrical conductivity], granulometric fractions, organic matter, base cations [Na, K, Ca and Mg] and heavy metals [Fe, Cu, Pb, Zn and Al] showed increasing loadings at high tide compared to low tide. Multivariate statistical techniques, principal components analysis [PCA] and cluster analysis [CA], were employed to better interpret information about the sediment and its controlling factors. The PCA results revealed six controlling factors at high tide while seven at low tide. In CA there are two district clusters were identified at high and low tides. The calculation of geoaccumulation index [Igeo] suggests the Mengkabong mangrove sediments are having background concentrations for Al, Cu, Fe, and Zn and unpolluted for Pb

Application of sediment quality guidelines in the assessment of mangrove surface sediment in Mengkabong Lagoon, Sabah, Malaysia

There have been numerous sediment quality guidelines developed to monitor the sediments. Sediment quality guidelines are very useful to screen sediment contamination by comparing sediment contaminant concentration with the corresponding quality guideline, provide useful tools for screening sediment chemical data to identify pollutants of concern and prioritise problem sites and relatively good predictors of contaminations. However, these guidelines are chemical specific and do not include biological parameters. Aquatic ecosystems, including sediments, must be assessed in multiple components [biological data, toxicity, physicochemistry] by using integrated approaches in order to establish a complete and comprehensive set of sediment quality guidelines. Numerous sediment quality guidelines Washington Department of Ecology Sediment Quality Guideline, Australian and New Zealand Environment and Conservation Council, Swedish Environmental Sediment Quality, Screening Quick Reference Table, Portuguese Legislation on the Classification of Dredged Materials in Coastal Zones and Interim Sediment Quality Guideline for Hong Kong have been applied to the Mengkabong lagoon mangrove sediment and discussed. The most appropriate guideline that meets the prioritization criteria consistent with international initiatives and regulations is interim sediment quality values for Hong Kong. The guideline verifies that all the metals are below the Interim Sediment Quality Value-low. However, site-specific, biological testing and ecological analysis of exisiting benthics community structure related to sediment contamination are needed for final decision making in the case of Mengkabong lagoon