Malaysian Soil Research Articles

Endocrine-Disrupting Compounds in Urban Soils of Malaysia: Occurrence, Contamination, and Impacts on Health and the Environment

Endocrine-disrupting compounds (EDCs) have garnered increasing concern in recent years due to their association with severe health issues and significant environmental impacts. EDCs, which can interfere with endogenous hormone systems, are diverse in structure and are often characterized by low molecular mass and halogen substitutions. Their presence in the environment, originating from both natural and synthetic sources, has been well-documented in water bodies, but studies on their occurrence in soils remain limited. This review provides a comprehensive overview of the occurrence, contamination, and impacts of EDCs in the urban soils of Malaysia. The paper discusses the primary sources of EDCs, including pharmaceuticals, pesticides, industrial chemicals, and combustion byproducts, and examines the pathways through which these compounds enter the soil. Health risks associated with exposure to EDCs, as well as their ecological consequences, are also explored. The review highlights the current status of EDCs contamination in Malaysian soils, identifies gaps in research, and outlines the challenges in monitoring and mitigating these contaminants. Understanding the dynamics of EDCs in soil is crucial for developing effective strategies to protect human health and the environment in urban settings.

Evaluation of new sorghum varieties for grain production cultivated in mineral soil

Sorghum bicolor L. (Sorghum) has been recognized as the fifth largest cereal crop in the world, following maize, wheat, rice, and barley, with a mean annual production of more than 5.89 million tons over the past five years. Grain sorghum is one of the cultivated varieties of the sorghum genus. It is primarily used as human food and animal feed due to the beneficial effects of bioactive compounds in the grain. Sorghum is less popular and unrecognizable in Malaysia, as it was not included in the reports by the Agriculture Department regarding plantation areas. In Malaysia, sorghum is limited because this crop is considered new, and no studies were conducted on the adaptability of its varieties to Malaysian soil and local climatic conditions. Crop production practices such as variety selection, planting density and fertilization will affect yield production. Therefore, a study on grain sorghum varieties (Brachy Sorgho, Jumbo Super, India and Pacific Seed 99) was conducted to evaluate the growth and yield performance of sorghum. Jumbo Super had a significantly higher value for plant height, followed by Brachy Sorgho, India and Pacific Seed 99. India showed the highest value of leaf fresh and dry weight, but no significant difference compared with Brachy Sorgho. Brachy Sorgho recorded the highest value of stem fresh and dry weight, while the least was recorded for Pacific Seed 99. Brachy Sorgho and India showed significantly higher grain yields than Jumbo Super and Pacific Seed 99 in terms of panicle length, panicle weight without grain, grain weight without panicle per plant, number of grains per panicle, and 100-grain weight. The highest gross weight of grain sorghum is Brachy Sorgho (140.00 g/plant), which showed no significant difference compared to the India variety (131.13 g/plant). Meanwhile, Jumbo Super and Pacific Seed 99 varieties showed the lowest grain weight, 77.27 g/plant and 80.16 g/plant, respectively. Overall, all four varieties are adaptable in mineral soil and are considered potential alternative crops for grain production. Bachy Sorgho and India varieties showed the best performance on grain yield compared to Jumbo Super and Pacific Seed 99 varieties. Thus, Brachy Sorgho and India varieties can be recommended for future grain production in mineral soil.

Estimation of soil erodibility in Peninsular Malaysia: A case study using multiple linear regression and artificial neural networks

Soil erodibility (K) is an essential component in estimating soil loss indicating the soil's susceptibility to detach and transport. Data Computing and processing methods, such as artificial neural networks (ANNs) and multiple linear regression (MLR), have proven to be helpful in the development of predictive models for natural hazards. The present case study aims to assess the efficiency of MLR and ANN models to forecast soil erodibility in Peninsular Malaysia. A total of 103 samples were collected from various sites and K values were calculated using the Tew equation developed for Malaysian soil. From several extracted parameters, the outcomes of correlation and principal component analysis (PCA) revealed the influencing factors to be used in the development of ANN and MLR models. Based on the correlation and PCA results, two sets of influencing factors were employed to develop predictive models. Two MLR (MLR-1 and MLR-2) models and four neural networks (NN-1, NN-2, NN-3, and NN-4) optimized using Levenberg-Marquardt (LM) and scaled conjugate gradient (SCG) were developed and evaluated. The model performance validation was conducted using the coefficient of determination (R2), mean squared error (MSE), root mean squared error (RMSE), and Nash-Sutcliffe efficiency coefficient (NSE). The analysis showed that ANN models outperformed MLR models. The R2 values of 0.446 (MLR-1), 0.430 (MLR-2), 0.894 (NN-1), 0.855 (NN-2), 0.940 (NN-3), and 0.826 (NN-4); MSE values of 0.0000306 (MLR-1), 0.0000315 (MLR-2), 0.0000158 (NN-1), 0.0000261 (NN-2), 0.0000318 (NN-3), and 0.0000216 (NN-4) suggested the higher accuracy and lower modelling error of ANN models as compared with MLR. This study could provide an empirical basis and methodological support for K factor estimation in the region.

Column percolation leaching test for rare-earth processed residue: Standard laboratory column elution experiments towards development permanent disposal facility (PDF)

The rare-earth industry in Malaysia primarily produces two main by-products in vast quantities: Water Leach Purification (WLP) and Neutralisation Underflow (NUF) residue. The average total concentration of rare earth elements (TREE) in WLP and NUF was discovered to be 54.2 g/kg and 29.5 g/kg, respectively. The heavy metal (HM) concentration for both was below the Malaysian soil intervention threshold except for arsenic and lead. The average thorium (Th) concentration of WLP exceeded the 1 Bq/g regulatory threshold. Such Th concentration prompted the need for WLP residues to be stored in a permanent disposal facility (PDF). The proposed PDF intends to take advantage of the gypsum properties of the NUF by deploying it as a liner material. It was discovered that the repurposing of NUF increases the pH of a single composition of WLP from 3.6 to a less acidic condition. The three different layer mixes of composition ratio NUF to WLP (PC3, PC4, PC5) of the study lead the pH of the effluent to range between 5 and 6, as compared to the pH range of 9.8–10.2 for NUF composition solely. The optimum composition ratio of NUF to WLP proposed by the study for the PDF is 1:19 (PC5), as the leaching of Th, HM, and REE in this condition is shown to be insignificant.

Land-use classification of Malaysian soils by ultra-high performance liquid chromatography (UHPLC)-based untargeted data combined with chemometrics for forensic provenance

Soil has become the most precious trace evidence attributed to its transference and persistence, but little is known about the capability of non-volatile organic fractions of soil in predicting land-use class. Hence, this study devoted to discriminating soils into four land-use classes based on chromatographic data and predictive modelling. Nine sites representing four different land-use classes were selected for collecting 73 soil samples via a grid method. Then, all the soil samples were dried, homogenized, sieved and eventually extracted using acetonitrile. The extracts were further analyzed via an isocratic elution in an ultra-high performance liquid chromatography (UHPLC) system. The pixel-level chromatograms were carefully assessed via diverse data preprocessing (DP) methods including baseline correction, normalization and derivative algorithms. Furthermore, the retention time (RT) window was also segmented into several sub-windows and thoroughly evaluated. Prediction accuracy of classification and regression tree (CART) modelling as estimated using 100 subsets of training samples on the corresponding testing and blind samples were ranked using TOPSIS method for identifying the most desired sub-window and DP strategy. The sub-RT window covering 0–5 min preprocessed via modified polynomial fitting algorithm followed by vector normalization emerged to be the most desired sub-dataset. The best sub-dataset modelled using CART and partial least squares-discriminant analysis (PLS2-DA) algorithms achieved 79.5 % and 97.4 % accuracy in predicting the land-use classes of 13 mixed samples. In conclusion, UHPLC-based fingerprint technique coupled with predictive modelling shows great potential in inferring land-use class of trace amount of soil.

Effect of natural antibacterial clays against single biofilm formation by Staphylococcus aureus and Salmonella Typhimurium bacteria on a stainless-steel surface

Staphylococcus aureus and Salmonella Typhimurium have a propensity to develop biofilms on food contact surfaces, such as stainless-steel, that persist despite rigorous cleaning and sanitizing procedures. Since both bacterial species pose a significant public health risk within the food chain, improved anti-biofilm measures are needed. This study examined the potential of clays as antibacterial and anti-biofilm agents against these two pathogens on appropriate contact surfaces. Natural soil was processed to yield leachates and suspensions of both untreated and treated clays. Soil particle size, pH, cation-exchange capacity, and metal ions were characterized to assess their importance in bacterial killing. Initial antibacterial screening was performed on nine distinct types of natural Malaysian soil using a disk diffusion assay. Untreated leachate from Kuala Gula and Kuala Kangsar clays were found to inhibit S. aureus (7.75 ± 0.25 mm) and Salmonella Typhimurium (11.85 ± 1.63 mm), respectively. The treated Kuala Gula suspension (50.0 and 25.0 %) reduced S. aureus biofilms by 4.4 and 4.2 log at 24 and 6 h, respectively, while treated Kuala Kangsar suspension (12.5 %) by a 4.16 log reduction at 6 h. Although less effective, the treated Kuala Gula leachate (50.0 %) was effective in removing Salmonella Typhimurium biofilm with a decrease of >3 log in 24 h. In contrast to Kuala Kangsar clays, the treated Kuala Gula clays contained a much higher soluble metal content, especially Al (301.05 ± 0.45 ppm), Fe (691.83 ± 4.80 ppm) and Mg (88.44 ± 0.47 ppm). Elimination of S. aureus biofilms correlated with the presence of Fe, Cu, Pb, Ni, Mn and Zn irrespective of the pH of the leachate. Our findings demonstrate that a treated suspension is the most effective for eradication of S. aureus biofilms with a potential as a sanitizer-tolerant, natural antibacterial against biofilms for applications in the food industry.

Thoron activity concentration in Malaysian soil gas: Geogenic impact assessment

Given the rather short half-life of thoron (220Rn), at 56 s, its contribution to radiation exposure is often overlooked. Nevertheless, in a thorium (232Th) rich environment potential hazard does exist, in particular regarding prolonged duration exposures to 220Rn and its short-lived alpha-particle emitting progeny [polonium (216Po)]. Herein, concerning the geology and major soil types in the Malaysian state of Perak, an activity concentration map has been established for 220Rn in soil gas, with the use made of a RAD7 detector and the THORON protocol for in-situ measurements. The detector has been coupled to a soil probe driven to a depth of 0.8 m. The activity concentration of 220Rn in the soil ranged from undetectable to 563 kBq m−3 with a mean value of 38 ± 11 kBq m−3. Granite and Triassic-Jurassic formations in the region showed more elevated 220Rn activity while Quaternary and Silurian formations revealed low 220Rn values. Moreover, while elevated 220Rn activity concentrations were found in peat, riverine, and granite source soils, the activity concentrations in marine and other soils were low. A primary map of 220Rn in the soil gas has been developed based on geogenic impact assessment, with a greater 220Rn activity concentration in the central part of the state.

Diary of a French Missionary: Penang During the Japanese Occupation by Marcel Rouhan

Reviewed by: Diary of a French Missionary: Penang During the Japanese Occupation by Marcel Rouhan Shanthini Pillai Diary of a French Missionary: Penang During the Japanese Occupation. By Marcel Rouhan, Translated and Introduced by Serge Jardin. Penang: Areca Books, 2021, 224 pp. ISBN 9789675719431 The College General in Penang has stood on Malaysian soil from the onset of the 19th Century, with even earlier links to Thailand reaching far back into the 17th Century. For the Malaysian Catholic community, the institution holds a special place of reverence because of its role as a major seminary for prospective young Catholic priests in the making, symbolising hope for the sustainability of the Catholic church, with certain quarters of academia probably more well versed with the intricacies of its historical foundations. Most references to the College General exist primarily in the French language. As such the publication of this diary written by Mgr Rouhan, one of the Directors of the institution before its transference to solely Malaysian clergy, and duly translated into English by Serge Jardin, a Malaysian domiciled French, is a significant contribution for awareness and understanding among the circles of Anglophone academia. The publication is organised into three sections. We are first provided with the translator's introduction to the diary, followed by excerpts from the translated diary itself and finally, a list of appendices that includes a timeline of key milestones pertaining to the rise and fall of Japanese Occupation in Malaya, informative lists of people and places mentioned in the diary as well as key Catholic missions. The translator must be commended for bringing to attention an especially valuable collection of day-to-day entries of a French missionary who not only held an important administrative position in a transnational Catholic educational institution, but who also possessed sufficient clout in the community to enable him to engage effectively with both the colonial government as well as their Japanese usurpers. The substance of this influence is revealed in the very first entry of the diary where we are told of a covert agreement to allow the British government temporary use of land belonging to the College General to prepare for the defence of Penang against the encroaching Japanese army. The extensive possessions of this French-administered religious institution in Penang are immediately gleaned from references not only to land owned but the acres that it spread over, which we learn later extended to numerous properties, coconut plantations as well as other agricultural holdings. We learn of multi-national tenants of the many bungalows that they owned including British, French, Danes and even Japanese. This is further underscored by the possessive pronouns used in abundance throughout when the diarist refers to the gazetting of the land by the government or the 'sacrifice' of numerous coconut trees and their abundant fruit, as well as other possessions scattered across the island of Penang. Seen collectively, these episodes draw attention to the fact that the College General was perceptibly a full-fledged financial arm of the Société des Missions Étrangères de Paris (M.E.P) or Paris Foreign Missions Society, generating income that would have been crucial for the maintenance of not only the college but also mission development work among the vast network of French-based religious societies operating in Penang at that juncture. [End Page 125] The diarist reveals the close-knit network that existed between the various French religious communities, mainly the missionaries of the M.E.P. responsible for the formation of Catholic parishes, and the La Salle brothers who, along with the Dames of Saint-Maur (more popularly known in Malaysia as the Infant Jesus Sisters or I.J.S.), set up various schools and orphanages. A strong sense of territoriality also surfaces when faced with secular encroachments into the grounds of the institutions founded by the French sisters especially. These constantly remind us that the discursive imaginary is Catholic at its core, as do the numerous references to prayers for the intercession of Saints, especially Saint Joseph, celebrations of high mass, community mass and various Catholic feast days. Of significant interest also are the references to several local Catholic priests who started out as seminarians during...

Evaluation of Row-wise Manipulations for the Forensic Differentiation of Malaysian Soils based on Ultra-performance Liquid Chromatographic Profiles

Evaluation of Row-wise Manipulations for the Forensic Differentiation of Malaysian Soils based on Ultra-performance Liquid Chromatographic Profiles

Antibacterial Activity of Clay Soils against Food-Borne Salmonella typhimurium and Staphylococcus aureus.

Natural clays have recently been proven to possess antibacterial properties. Effective natural antimicrobial agents are needed to combat bacterial contamination on food contact surfaces, which are increasingly more prevalent in the food chain. This study sought to determine the antibacterial activity of clays against the food-borne pathogens Salmonella typhimurium ATCC 14028 and Staphylococcus aureus ATCC 13565. Soils were processed to yield leachates and suspensions from untreated and treated clays. Soil particle size, pH, cation-exchange capacity, metal composition and mineralogy were characterized. Antibacterial screening was performed on six Malaysian soils via the disc diffusion method. In addition, a time-kill assay was conducted on selected antibacterial clays after 6 h of exposure. The screening revealed that Munchong and Carey clays significantly inhibit Salmonella typhimurium (11.00 ± 0.71 mm) and S. aureus (7.63 ± 0.48 mm), respectively. Treated Carey clay leachate and suspension completely kill Salmonella typhimurium, while S. aureus viability is reduced (2 to 3 log10). The untreated Carey and all Munchong clays proved ineffective as antibacterials. XRD analysis confirmed the presence of pyrite and magnetite. Treated Carey clays had a higher soluble metal content compared to Munchong; namely Al (92.63 ± 2.18 mg/L), Fe (65.69 ± 3.09 mg/L) and Mg (88.48 ± 2.29 mg/L). Our results suggest that metal ion toxicity is responsible for the antibacterial activity of these clays.

Potential of Carbofuran Degradation by Soil Bacteria in Malaysia: A Review

Carbofuran is a very toxic and systemic carbamate pesticide which is used as an extensive carbamate insecticide, nematicide andacaricide. It is applied to the soil as a treatment to manage or destroy pests and parasites to improve the quality of agricultural production. It is also an anticholinesterase carbamate which is highly toxic to plants, animals andhumans. The consequences have received great concern as many health-associated problems have still been reported due to pesticide poisoning. In humans, carbofuran is associated with the inhibition of cholinesterase, which could develop a cholinergic crisis known as sludge syndrome. Therefore, it is essential to take quick action to eliminate this pesticide from the environment. Bacterial degradation is a very eco-friendly method for the elimination of carbofuran. Bacterial enzymes and degradation genes play an essential role in catalyzing new biochemical pathways during the bacterial degradation process. A complete screening of bacterial carbofuran metabolic pathway can develop marker genes or enzymes to determine useful bacteria in the contaminated sites capable to degrade carbofuran residues. Therefore, this review focused on the understanding of bacterial degradation of carbofuran in Malaysian soils and to explore the possibility of soil bacteria to degrade carbofuran effectively. Thus, we emphasize on the carbofuran toxicity, bacterial degradation, metabolic and molecular mechanisms of carbofuran's degradation process.

Growth Performance of Malaysian Parthenium hysterophorus under Various Environmental Variables

Parthenium weed is an invasive weed species of economic importance worldwide. Native to the American tropics, the infestation ability of Parthenium weed to a new habitat is largely influenced by environmental factors. Despite Parthenium weed invasion in Malaysia dated back to 2013, investigation on its ecological behavior is still lacking. Hence, extensive studies on the ecological behavior of two predominant Malaysian Parthenium weed populations were executed. In the Petri dish seed bioassay, germination of Parthenium weed seeds was evident at temperatures up to 80 °C. Parthenium weed was also germinable in saline condition of up to 250 mM, osmotic pressure ranging from −1.2 to 0 MPa, and a wide range of pH (4–9), thus these abiotic conditions are by no means the limiting factors for the Parthenium weed. The pot trial observed that this invasive weed grew readily in various Malaysian soil textures. Parthenium weed successfully emerged from 0 cm to not beyond 2 cm soil burial and retained its emergence capacity under different submergence periods in water. The most favorable soil moisture condition for Parthenium weed emergence was saturated (0 kPa), followed by field capacity (−30–−50 kPa), while no emergence occurred in drought (−70 kPa) as well as flooded soils. These indicate that both Parthenium weed populations possess high tolerance to various abiotic conditions in Malaysia. Results obtained in the current study have crucially become guidelines for the local government authorities in predicting wide spread of Parthenium weed in diverse ecological zones, to further manage this pernicious weed efficiently.

In vitro Cytotoxicity and Antioxidant Study of Rhodomyrtus tomentosa (Aiton) Hassk. Ethanolic Leaf Extract on LPS-induced RAW 264.7 Macrophage Cells

Aims: Ethanol extract of Rhodomyrtus tomentosa leaves found specifically on Malaysian soil was used to further investigate the antioxidant properties and cytotoxicity against RAW 264.7 macrophage cells in the search for a safer and effective natural antioxidant agent.
 Study Design: Antioxidant potential of R. tomentosa were analyzed through series of spectrometric assays and cell-based bioassays model.
 Place and Duration of Study: This study was carried out at Faculty of Pharmacy, Universiti Teknologi MARA (UiTM), Puncak Alam Campus, 43200, Selangor, Malaysia from the year of 2019 to 2021.
 Methodology: R. tomentosa leaves were subjected to extraction with 95% ethanol. The extracts were then denoted as ethanolic leaves extract of R. tomentosa or EtRT extract. EtRT extract were then screen for its antioxidant activity (AOA) and total antioxidant capacity (TAC) through DPPH radical scavenging assay and ferric reducing antioxidant power (FRAP) assay. After that, EtRT extract were brought to observe its toxicity against RAW 264.7 macrophage cells in MTT assay. Once their toxicity was obtained, EtRT extracts were finally tested for their ability to inhibit intracellular reactive oxygen species (ROS) and nitric oxide (NO) inhibition in RAW 264.7 macrophage cells to further analyze their antioxidant properties.
 Results: In this study, EtRT extracts dose dependently showed the ability to scavenge DPPH radicals and reduce ferric ions during DPPH radicals scavenging activity assay and ferric reducing antioxidant power assay (FRAP), respectively. In DPPH radical scavenging activity assay, EtRT extracts showed EC50 value at 12.37 ± 1.73 µg/mL with ARP value of 0.08 almost as near as ascorbic acid’s ARP value which is 0.09. Further into the study, EtRT extract were not cytotoxic to RAW 264.7 macrophage cells at concentrations 3.91 µg/mL and lower which showed more than 86.4% cell viability with IC50 value at 204.70 ± 5.30 µg/mL. EtRT extract possessed the ability to inhibit ROS production on LPS-induced RAW 264.7 macrophage cells at 7.813 µg/mL and lower, with the highest concentration can reduce up to 30.20% ± 1.01 out of the total ROS produced by the induced cells. Furthermore, EtRT extract also have evidenced that it is able to significantly inhibit NO production by the LPS-induced RAW 264.7 macrophage cells at 7 µg/mL and lower being the highest at 56.73% ± 0.11 inhibition of the highest concentration tested.
 Conclusions: This study suggests that EtRT extracts have the potential to reduce LPS-induced oxidative stress due to the antioxidant activities of phenolic compounds in the extracts, and that at low doses, EtRT extracts had low to no cytotoxicity on RAW 264.7 macrophage cells. As a result, EtRT extract could be a promising natural medicinal agent for the treatment of oxidative stress.

Empirically Based Rainfall Threshold for Landslides Occurrence in Peninsular Malaysia

Empirical rainfall thresholds for the purpose of shallow landslide forecasting are proposed for Peninsular Malaysia where numerous slope failures are reported due to the intense rainfall in conjunction with the humid tropical climate. Thirty-seven cases of landslide-triggering-rainfall were selected from 1993 to 2018 to identify the correlation between rainfall and shallow landslide through the analysis of specific rainfall events. The derived rainfall parameters were applied to establish two rainfall thresholds of (Imean-D) and (Imax-D) via practical methods. For the identical range of event duration 1 < D < 263 h, the (Imean-D) threshold formula was expressed as I = 17.5 D−0.722, while the (Imax-D) threshold was defined as I = 37.8 D−0.114. Both thresholds performed different functionalities with a primary goal of predicting shallow landslides. When both (Imean-D) and (Imax-D) thresholds were compared with the thresholds proposed by various studies worldwide, both dominated the upper positions. More rainfall is required for land sliding due to the high thickness of the Malaysian soil that is associated with the abundant tropical downpour. From the perspective of the antecedent, the period of prolonged precipitation or short heavy rainfall from 1 to 10 days can result in shallow landslides for Peninsular Malaysia. In the context of geology, the igneous rock type of granite has the highest susceptibility to the shallow landslide at 65%, despite other rock types of sedimentary and metamorphic. The threshold validation depicted all True Positive events for the (Imax-D) threshold, and one Negative False event for the (Imean-D) threshold. The (Imean-D) threshold was revised to acquire the new value, but it needed to deal with the possibility of False Alarm and the (Imax-D) threshold seemed to be more credible to represent the rainfall-induced shallow landslide threshold for Peninsular Malaysia.

A Study on Perception on the Malay Language Proficiency among Bangladeshi Migrants Who are Involved in the Business Sector in Kuala Lumpur

Malaysia whom with open arms welcomes foreigners to help develop its economy catches the attention of especially the Bangladeshis. Undoubtedly, the presence of Bangladeshis has helped in filling in the vacancies in many sectors such as plantation, construction, services and manufacturing. Their work stint and experience gained leads to a paradigm shift, from an employee to an entrepreneur. Migration to Malaysia demands them to learn and acquire the Malay language for survival. In addition, proficiency in the Malay language is an added value as it makes them feel contented, secure and successful. This study aims to look at the perception on the proficiency of the Bangladeshis entrepreneurs who are adapting the Malay language as the main medium of communication. The relation between levels of education and proficiency in 1) speaking, 2) reading and 3) writing is analysed. This study also evaluates the importance of the Malay language usage among Bangladeshis in managing businesses. A survey was conducted on 56 Bangladeshi migrants who were involved in the business field in Kuala Lumpur. Surely, it is crucial for Bangladeshis who wish to work in this country to be proficient in the Malay language. This is to ensure their survival strategy is sustained, allowing them to tap a gold mine in Malaysian soil.

Forensic profiling of non-volatile organic compounds in soil using ultra-performance liquid chromatography: a pilot study

Soil is of particular interest to the forensic community because it can be used as valuable associative evidence to link a suspect to a victim or a crime scene. Liquid chromatography is a powerful analytical tool for organic compound analysis. Recently, high-performance liquid chromatography (HPLC) has proven to be an efficient method for forensic soil analysis, especially in discriminating soils from proximity locations. However, ultra-performance liquid chromatography (UPLC), which is much more sensitive than HPLC, has never been explored in this context. This study proposed a UPLC method for profiling non-volatile organic compounds in three Malaysian soils (red, brown and yellowish-brown soils). The three soils were analysed separately to assess the effects of individual chromatographic parameters: (a) elution programme (isocratic vs. two gradient programmes); (b) flow rate (0.1 vs. 0.2 mL/min); (c) extraction solvent (acetonitrile vs. methanol) and (d) detection wavelength (230 vs. 254 nm). The injection volume and total run time were set to 5 µL and 35 min, respectively. Consequently, each soil sample gave 24 different chromatograms. Results showed that the most desirable chromatographic parameters were (a) isocratic elution; (b) flow rate at 0.2 mL/min and (c) acetonitrile extraction solvent. The proposed UPLC system is expected to be a feasible method for profiling non-volatile organic compounds in soil, and is more chemical-efficient than a comparable HPLC system.

A Comparative Study of Shear Strength Equations for Unsaturated Granitic Residual Soil

Abstract Malaysia is extensively covered by residual soils, which are mostly in an unsaturated zone. Determining the unsaturated shear strength of residual soils using the empirical models is beneficial because of the limitations of experimental methods. Several shear strength models have already been developed, and the accuracy of some of these models has been examined. However, these examinations were developed based only on the particular soils initially studied and may not be applicable to Malaysian residual soils. This study aims to provide a comparative investigation of the accuracy of some of the published shear strength models for unsaturated soils in predicting the shear strength of a Malaysian granitic residual soil. The published shear strength results of the soils were used in this paper to provide comparisons between the predicted and measured shear strength values for a limited suction range. Nine various equations were evaluated. For each equation, a relationship between the predicted and measured shear strength data was generated. The linear regression line with zero intercept was drawn, and the slope of the linear regression line (SL) and coefficient of determination (R2) were calculated. This study showed that all shear strength models provide relatively acceptable comparisons between measured and predicted shear strengths by a maximum of 10 % difference based on the calculated slopes of the regression lines. However, among them, three equations provided more accurate predictions in comparison with the others.

Prediction of Stress-Strain Response Using Rotational Multiple Yield Surface Framework in Malaysian Residual Soil

Soil settlement is normally quantified using conventional soil volume change models which are solely based on the effective stress and the role of shear strength is ignored due to the difficulties to incorporate in the framework. The Rotational Multiple Yield Surface Framework (RMYSF) is a soil volume change model developed from the standpoint of the interaction between the effective stress and shear strength. RMYSF incorporates the development of mobilised shear strength within the body of the soil whenever the soil is subjected to anisotropic compression. Currently the framework has been applied to predict the soil anisotropic stress-strain behaviour at any effective stress. This paper present the enhancement of this volume change framework using normalisation of axial strain with the understanding that the failure axial strain is not unique, but increases as the effective stress increases. This technique has essentially produced a better accuracy in the prediction of the stress-strain response for Malaysian residual soils. A series of drained tri-axial tests under various effective stresses has been conducted using specimens of 50mm diameter and 100mm height and from the stress-strain curves the inherent mobilised shear strength envelopes at various axial strains have been determined. These mobilised shear strength envelopes were then applied for the prediction of the soil stress-strain response. An excellent agreement between the predicted and the actual stress-strain curves has been achieved.

Determination of the Leaching Potential and Residues Activity of Imidazolinone Herbicide in Clearfield Rice Soil Using High-Performance Liquid Chromatography.

The residual activity of herbicides may be detrimental to the environment, requiring analysis of the persistent residues in the soil and water. A field study was conducted to measure the residues of Imidazolinone (IMI) in three Clearfield® rice field soils at three different locations in Malaysia. The analyses of IMI in the soil samples were carried out using a high-performance liquid chromatography (HPLC). These herbicides are widely used; however, few studies have been conducted on both residues, especially in the context of Malaysian soil. Residues of imazapic and imazapyr were found to fall within 0.03-0.58µg/mL and 0.03-1.96µg/mL, respectively, in three locations. IMI herbicides are persistent in the soil, and their residues remain for up to 85days after application. A pre-harvest study was suggested for these herbicides on water, which will provide a clearer indicator on the use of IMI in Clearfield® rice fields.

Adsorption-desorption and leaching potential of glyphosate and aminomethylphosphonic acid in acidic Malaysian soil amended with cow dung and rice husk ash.

This study investigates adsorption-desorption and the leaching potential of glyphosate and aminomethylphosphonic acid (AMPA) in control and amended-addition of cow dung or rice husk ash-acidic Malaysian soil with high oxide mineral content. The addition of cow dung or rice husk ash increased the adsorptive removal of AMPA. The isotherm data of glyphosate and AMPA best fitted the Freundlich model. The constant Kf for glyphosate was high in the control soil (544.873mgg-1) followed by soil with cow dung (482.451mgg-1) then soil with rice husk ash (418.539mgg-1). However, for AMPA, soil with cow dung was high (166.636mgg-1) followed by soil with rice husk ash (137.570mgg-1) then the control soil (48.446mgg-1). The 1/n values for both glyphosate and AMPA adsorptions were < 1 indicating their strong affinity for adsorbents. Desorption of both glyphosate and AMPA occurred only in the control soil. The compounds were not detected in soils with added cow dung or rice husk ash. The addition of cow dung or rice husk ash increased glyphosate mobility. However, ground water ubiquity scores for both control and amended soils were < 2.8. This indicated glyphosate is a transitional herbicide; therefore, its leaching potential in the soil is low, despite the addition of cow dung or rice husk ash. Addition of these wastes decreased the mobility and leaching potential of AMPA. The addition of cow dung or rice husk ash could be beneficial in increasing adsorption and enhancing degradation of these compounds.