Tham Fatt Ng

Cumulative impacts of dissolved ionic metals on the chemical characteristics of river water affected by alkaline mine drainage from the Kuala Lipis gold mine, Pahang, Malaysia

This paper describes the variations in levels of dissolved metals with spatial and hydrological conditions along the Kermoi River, which drains a gold mining area. The spatial analysis of data on metal levels in the river indicates that the levels of almost all types of studied ionic species tend to increase when moving from an upstream location towards the mining area; significant enrichments of 91%, 55%, 8% and 75% in As, Mn, Zn and levels, respectively, were observed, indicating that the mining area is a source of these metals. From the mining area towards a downstream location, metal levels tended to decrease, suggesting that a natural attenuation process occurred for all metals except As. We also found that different hydrological conditions clearly impacted the level of metals in and the water quality of the river. Correlation analyses revealed that different types of metals were associated with different flow conditions. We recommend that remediation strategies such as the construction of wetlands and the installation of phytoremediation technology at mining sites be considered.

Effects of Lateral Variation in Vegetation and Basin 'Dome' Shape on Tropical Lowland Peat Stabilisation in the Kota Samarahan-Asajaya Area, West Sarawak, Malaysia

Field surveys indicate lateral variation in peat humilIcation levels (von Post) in dominantly occurring fibric, fibric to hemic, sapric and hemic to sapric peats across a gradient from the margin towards the centre of tropical lowland peat domes. Cement-peat stabilisation can be enhanced by adding mineral soil fillers (silt, clays and line sands) obtained from Quaternary floodplain deposits and residual soil (weathered schist). The unconfined compressive strength (UCS) of the stabilised cement-mineral soil filler-peat mix increases with the increased addition of selected mineral soil filler. Lateral variation in the stabilised peat strength (UCS) in the top 0 to 0.5 m layer was found from the margin towards the centre of the tropical lowland peat dome. The variations in the UCS of stabilised tropical lowland peats along a gradient from the periphery towards the centre of the peat dome are most likely caused by a combination of factors due to variations in the mineral soil or ash content of the peat and horizontal zonation or lateral variation in the dominant species of the plant assemblages (due to successive vegetation zonation of the peat swamp forest from the periphery towards the centre of the tropical lowland peat dome).

Failure mechanisms in weathered meta-sedimentary rocks

The weathering profile of the extended cut slope within the quartz mica schist along Pos Selim Highway in Perak State, Malaysia shows three broad morphological zones; bedrock zone, intermediate zone, and residual soil zone. Further thinner horizons within these broad morphological zones were differentiated based on differences particularly in textures and structures of original bedrock and degree of preservation of the constituent minerals. Both large and small scale discontinuities observed in the schist provide slip surfaces for failures, and field investigation showed evidence of failures in this extended cut slope. The implications of the micro-structures revealed through petrography showed shearing components along planes of weakness. From the determined index properties of the weathered profile, the quartz mica schist is not suitable for structural support. This is also evidenced by the high values of sand over silt and clay deduced from the sieve analysis. In the bedrock zone, weathering manifests itself by opening up of discontinuities within the rock mass rather than weakening of the material itself. From the kinematic analyses carried out on the rock cuts, there are possibilities of wedge, planar and toppling failures across this extended cut slope.

Assessment of groundwater salinity and quality in Gaza coastal aquifer, Gaza Strip, Palestine: An integrated statistical, geostatistical and hydrogeochemical approaches study

A comprehensive study was conducted to identify the salinization origins and the major hydrogeochemical processes controlling the salinization and deterioration of the Gaza coastal aquifer system through a combination approaches of statistical and geostatistical techniques, and detailed hydrogeochemical assessments. These analyses were applied on ten physicochemical variables for 219 wells using STATA/SE12 and Surfer softwares. Geostatistical analysis of the groundwater salinity showed that seawater intrusion along the coastline, and saltwater up-coning inland highly influenced the groundwater salinity of the study area. The hierarchical cluster analysis (HCA) technique yielded seven distinct hydrogeochemical signature clusters; (C1&C2: Eocene brackish water invasion, C3 saltwater up-coning, C4 human inputs, C5 seawater intrusion, C6 & C7 rainfall and mixing inputs). Box plot shows a wide variation of most of the ions while Chadhas plot elucidates the predominance of Na-Cl (71.6%) and Ca/Mg-Cl (25%) water types. It is found that, the highest and the lowest levels of salinization and the highest level of nitrate pollution were recorded in the northern area. This result reflects the sensitivity of this area to the human activities and/or natural actions. Around 90.4% of the wells are nitrate polluted. The main source of nitrate pollution is the sewage inputs while the farming inputs are very limited and restricted mostly in the sensitive northern area. Among the hydrogeochemical processes, ion exchange process was the most effective process all over the study area. Carbonate dissolution was common in the study area with the highest level in clusters 6, 7, 4 and 2 in the north while Gypsum dissolution was significant only in cluster 1 in the south and limited in the other clusters. This integrated multi-techniques research should be of benefit for effective utilization and management of the Gaza coastal aquifer system as well as for future work in other similar aquifers systems.

Influence of discontinuities on the stability of cut slopes in weathered meta-sedimentary rocks

The meta-sedimentary rocks along Pos Selim Highway in Perak State, Malaysia showed a gradational weathering profile based on differences particularly in textures, hardness, lateral changes in colour and consistency of material extension. Both large and small scale discontinuities observed in the investigated rocks reduce the physical and mechanical properties of the rocks, and provide slip surfaces for failures. Rock and soil samples were tested using established standards to determine their characteristics and responses under a wide variety of disturbances. Kinematic analyses were also carried out to determine the modes and likely modes of failures. Petrographic analyses revealed associated micro-structures, and the implications of these micro-structures showed shearing components along planes of weakness. From the determined index properties of the tested soil samples, the weathered quartz mica schist is not suitable for structural support. Further study involving unconsolidated undrained direct shear box tests carried out under total stress, revealed a non-uniform response of the rocks to shearing disturbance along discontinuity planes, and the rate and depth of deformation. The shear strength components of the investigated rocks were thereby prescribed in terms of cohesion and friction angle. From the kinematic analyses across this extended cut slope, there are possibilities of wedge and planar failures.