Hydrocarbon Pollution in the Sediment of Some Malaysian Coastal Areas

A study was carried out at some selected coastal areas of Malaysia to determine the present status of hydrocarbon pollution. Five sites were chosen and these include Pulau Langkawi and Pulau Ketam in the west coast, Tanjung Piai in the south, and Pulau Tioman and Kemaman in the east coast of Peninsular Malaysia. The levels of total hydrocarbon in the sediments are found to vary from 18.2 to 847.4 mg kg-1 with sediments from Pulau Langkawi and Tanjung Piai recorded the highest values (691.2 to 847.4 mg kg-1) while Kemaman and Pulau Ketam recorded the lowest values (18.2 to 59.8 mg kg-1). It was noted that these values are related not only to possible sources of hydrocarbon but also to the physical characteristics of the sediments analysed. Sandy sediment generally contains less hydrocarbon than clayey sediment. Further analyses of the sediment extracts indicate that the sources of the hydrocarbon pollution are predominantly petrogenic with significant contribution from biogenic hydrocarbon.     

Prediction of Soil and Nutrient Losses in A Highland Catchment

Highland catchments in tropical regions are frequently subjected to soil erosion and the transport of chemicals downstream. Any drastic changes in land use will increase the severity of these processes of land degradation. A simulation study using GLEAMS (Groundwater Loading Effects of Agricultural Management Systems) was conducted at a catchment presently under tea farming in Cameron Highlands, Malaysia. Soil, water and nutrient transport associated with several alternative land uses was studied. In addition, the effect of a disruptive form of land clearing on soil, water and nutrient losses was also investigated. Modelling with GLEAMS required information from field measurements and observations, laboratory analyses, guide tables, industry records, maps and reports published by soil survey and meteorological departments. The most critical step in simulating soil and water movement using GLEAMS is the identification of a representative flow sequence. In the catchment under study, the representative flow sequence was overland flow–channel 1–channel 2. Input data on soil erodibility, porosity and surface roughness were manipulated to represent various degrees and forms of disturbance to the surface soil layer. For all land uses studied, the highest soil loss was predicted for the overland flow area where slope gradient is high and the soil friable. The variations in soil loss, runoff and nutrient loss between landscape elements and between land uses were consistent with soil erosion features observed in the field. Soil and nutrient losses were substantial for crops such as cabbage that required land shaping activities and frequent ploughing of the soil. Predicted data on enrichment ratio of specific surface (ERSS) are consistent with nutrient enrichment processes in the field and could prove to be useful in studies on chemical transport in highland catchments.     

Phenolic water pollutants in a Malaysian River basin

Phenolic chemicals with their very low taste and odour thresholds, high persistence and toxicity, are of growing concern as water pollutants. The compounds are known to exist in raw water as well as in treated water. The level of phenolic priority pollutants in water within the catchment area of the Linggi River Treatment Plant in Negeri Sembilan, Malaysia, which includes the Linggi river basin, was monitored. The 4-aminoantipyrin colourimetric method was used to determine total phenols whereas capillary column gas chromatography was used to determine the individual compounds. The results show that at most sampling stations, particularly those within the Seremban municipality, the level of phenols was found to exceed the recommended Malaysian standard of 2.0 g/L^-1 for raw water. This is seen as the direct impact of industrial and urbanization of the area and clearly indicates the unhealthy state of the Linggi river. The results also indicate the need to improve the water quality if the river is going to be used as a source of raw water.     

Kinetic adsorption of application of carbon nanotubes for Pb(Ⅱ) removal from aqueous solution

The capability of carbon nanotubes (CNTs) to adsorb lead (Pb) in aqueous solution was investigated. Batch mode adsorption experiment was conducted to determine the effects of pH, agitation speed, CNTs dosage and contact time. The removal of Pb(Ⅱ) reached maximum value 85% or 83% at pH 5 or 40 mg/L of CNTs, respectively. Higher correlation coeffcients from Langmuir isotherm model indicates the strong adsorptions of Pb(Ⅱ) on the surface of CNTs (adsorption capacity Xm = 102.04 mg/g). The results indicates tha...     

Synthesis and antithyroid activity of 6‐n‐propyl‐5‐arylazo‐2‐thiouracils †

The synthesis of several 6‐n‐propyl‐5‐arylazo‐2‐thiouracil derivatives was achieved. The antithyroid activity of these derivatives has been determined using iodine‐125‐thiocyanate discharge technique in rats, and 6‐n‐propyl‐2‐thiouracil (PTU) as a standard. None of the 5‐arylazo‐2‐thiouracil analogs showed antithyroid activity as compared to PTU. The structure‐activity relationships (SAR) of position 5 in the PTU molecule and the requirements for better binding to the proposed receptor are discussed.     

Estimation and validation of biomass of a mountainous agroecosystem by means of sampling,spectral data and QuickBird satellite image

Biomass estimation in agroecosystems (AESs) is important to understand their role in carbon exchange for a sustainable environment. We used field spectra and sampled biomass of an AES including cultivated and abandoned croplands to develop a simple biomass estimation model. The digital number (DN) of a QuickBird (QB) satellite image was converted to a reflectance factor using the dark object subtraction method and the spectral reflectance of asphalt. The relationship between the reflectance factor of field-based spectra and the QB image obtained in early July 2007 was insignificant in the blue (R ² = 0.15) and green (R ² = 0.18) bands but was significant (p < 0.05) in the red (R ² = 0.57) and near-infrared (NIR, R ² = 0.45) bands in the AES. Better correlations were obtained between field-based and QB-based vegetation indices (VIs). The best correlations were obtained with the normalized difference vegetation index (NDVI) (R ² = 0.97, p < 0.001) and the ratio vegetation index (RVI) (R ² = 0.99, p < 0.001). Biomass was significantly correlated with both field-based NDVI and RVI (R ² = 0.79 and 0.72, respectively, p < 0.001). Although RVI saturated at higher biomass densities (>600 g m^?2), NDVI showed a linear relationship. Other field-based VIs showed poorer correlations with biomass. The model was evaluated by incorporating it into high-resolution QB images to obtain the observed biomass. The relationship between field-estimated and QB-observed biomass appeared to be a one-to-one linear relationship (R ² = 0.79). Thus, models using field spectra and sampled biomass can be applied to QB images for remote estimation of biomass in an AES.     

Distributions of total metals in the surface sediments of the Bandirma and Erdek Gulfs,Marmara Sea,Turkey

The aim of this study is to determine the contents of aluminum, iron, manganese, nickel, copper, zinc, chromium, cadmium, lead, and mercury in sediments at 1–30?m depths of the Band?rma and Erdek Gulfs in the Southern Inner Shelf of the Marmara Sea. Sediment samples were collected from different depths (1?m, 5?m, 10?m, 20?m, 30?m) at each region in February 2008. Primary hydrographic conditions, such as temperature (6.6–14.5°C), salinity (22.6–26.875 psu), percentage of dissolved oxygen saturation (35–83 %), and pH (8.0–8.4) were recorded for each sampling point. Moreover the total organic carbon (0.5–2.9%) and the total calcium carbonate contents (0.8–60%) of sediment samples were determined. In surface sediments of both gulfs, Pb (21–62?mg?kg^?1) and Cd (0.52–0.86?mg?kg^?1) contents were determined to be higher than the shale average (Pb 20?mg?kg^?1, Cd 0.2?mg?kg^?1) while the other metal contents were measured to be lower in general. On the other hand, generally Hg (0.06–1.1?mg?kg^?1) contents were higher than the shale average (0.3?mg?kg^?1)at all of the examined stations in the Band?rma Gulf and lower than the shale average in the Erdek Gulf.     

Assessment of heavy metals contamination in soils surrounding a gold mine: comparison of two digestion methods

This study investigated two digestion methods (USEPA 3051: microwave, HNO₃ or Hossner: hot plate, HF–H₂SO₄–HClO₄) for heavy metals analysis in contaminated soil surrounding Mahad AD'Dahab mine, Saudi Arabia. Moreover, contamination metal levels were estimated. The Hossner and USEPA 3051 methods showed, respectively, average total contents of 17.2 and 18.1 mg kg^?1 for Cd, 11.6 and 10.6 mg kg^?1 for Co, 45.7 and 34.7 mg kg^?1 for Cr, 1030 and 1100 mg kg^?1 for Cu, 33,300 and 27,400 mg kg^?1 for Fe, 963 and 872 mg kg^?1 for Mn, 33.2 and 22.8 mg kg^?1 for Ni, 791 and 782 mg kg^?1for Pb, and 6320 and 2870 mg kg^?1 for Zn. A lack of significant differences and a high correlation coefficient (>90%) for Cd, Pb and Cu between the two digestion methods suggest that the total-recoverable method (USEPA 3051) may be equivalent to the total-total digestion method (Hossner) for determining these metals in the studied soil. However, significantly higher concentrations of Cr, Fe, Ni and Zn were found by the Hossner method comapred with the USEPA 3051 method. The soil samples have very or extremely high levels of Zn, Cu, Cd and Pb contamination, indicating very high potential ecological risk.     

Factors influencing corrosion of metal pipes in soils

Deterioration of buried metal pipes due to corrosive soil environment is a major issue worlwide. Although failures of buried pipe due to corrosive soil is an old problem, yet such failures are still uncontrollable even with the application of advanced corrosion protection technologies. Therefore, understanding factors causing corrosion of buried pipes is necessary. This article reviews factors causing corrosion of buried pipes in soils. Factors include moisture content, soil resistivity, pH, dissolved oxygen, temperature and microbial activity. Moreover, we discuss the influence of manufacturing method and the comparison of corrosion behaviour of cast iron, ductile and mild steel pipes. We found that corrosion rate of pipes increases with moisture contents up to the critical moisture value. Although pH affects corrosion, there is no relationship between corrosion and pH and the corrosion rates of buried pipes are inversely proportional to soil resistivity. Soils containing more organic matter show high resistivity. Dissolved oxygen in soil develops differential cell which accelerates corrosion of metallic pipe. Different types of bacteria present in soil develop biofilms on metallic pipes, which deteriorates pipes with time.