Zainudin Othman

Historical variations of Bera Lake (Malaysia) sediments geochemistry using radioisotopes and sediment quality indices.

The Bera Lake basin is a lacustrine mire system and the largest natural lake in Peninsular Malaysia. Three cores were collected from the lake sediments in order to assess sediment quality and ecological risks for aquatic life and human health. An index analysis approach (Cf, Cd, Er, and IR) and fallout 210Pb and 137Cs radioisotopes were applied to assess the impacts of environmental evolutionary changes. Sediment chronology was determined using the Constant Rate of Supply model with the resultant ages verified by 137Cs horizons. Although the general contamination factors indicate low risk conditions in Bera Lake the risks associated with individual layers ranged from moderate to considerable. Five deforestation phases can be identified in the dated sediment cores with distinct variations in heavy metal influxes since 1972. These phases are in excellent agreement with the dates of land clearance and development projects undertaken over the past four decades. This study has highlighted the capability of contamination factors and chronological methods in environmental evolutionary studies where catchments have experienced extensive land use changes. The destiny of heavy metal influxes into a lake can also be revealed using this methodology.

Sedimentation rates in Bera Lake (Peninsular Malaysia) using 210Pb and 137Cs radioisotopes

The evolutionary environmental history of Bera Lake was studied using the fallout radioisotopes137Cs and 210Pb. 317Cs horizons in the all ten studied cores showed a constant rate of 210Pb supply along all distinctive layers in each core. The lithology of layers significantly affected the variation of 210Pb value with depth. The chronology of Bera Lake sediment was conducted using the Constant Rate of Supply (CRS) model. The 1963 fallout maximum 137Cs from atmospheric testing of nuclear weapons found in all selected master cores at the depth of 40 cm. The mean pre-1950 sediment accumulation rate was ranged between 0.06 ± 0.02 and 0.16 ± 0.2 g cm−2 y−1. Environmental impacts of five deforestation projects performed from 1972 to 1995 at the catchment area, contributed significantly toward increasing the sedimentation rate within Bera Lake. Besides the 137Cs horizons, the charcoal horizon at the lower contact of white sandy mud revealed the datum of maximum deforestation in the study area. 210Pb dates using the CRS model correlated historical sediment fluxes to anthropogenic changes in Bera Lake catchment area. Organicrich sediments deposited mostly at the top of the Bera Lake sediment columns with a mean rate of 0.2 ± 0.1 g cm−2 y−1 since 1994. High biomass productivity of mature oil palm plantations, which were developed in the catchment area, dictated organic-rich deposit distribution. This study highlighted capability of radioisotopes to reconstruct long-term (100–150 years) history of a natural lake at a tropical area where surrounding catchment has extensively deforested over the recent decades.

Analysing the local geography of the relationship between residential property prices and its determinants

Abstract This paper analyses the local geography of the relationship between residential property prices and its determinants. A semiparametric geographically weighted regression (S-GWR) technique is employed to explore this relationship. Selling prices, structural and locational attributes data were collected from the database of the Department of Valuation and Services of Malaysia, selected maps and reports. The outcome of this paper shows a strong geographically varying relationship between residential property prices and its determinants in which the residential property price determinants have a positive impact on prices in some areas but negative or no impact on the others. The magnitude of the effect is also found to be geographically varied; the capitalisation in residential property prices is found greater in some areas but less or with no effect in some other parts of the areas. The use of S-GWR technique makes it possible to reveal such geographically varying relationships, thus leading to a better understanding of the relationship between residential property prices and its determinants.