For decades, the percentage of pesticide usage has steadily increased in order to meet the demands of food production. The aim of this study is to estimate the risk posed towards farmers through exposure to surface water containing imazapic herbicide using dermal exposure assessment (DEA). For this purpose, hazard index (HI) value was calculated to estimate the risk posed towards the farmers. Although calculated HI showed a minimum level of risk, there are concerns toward the danger of long-term exposure to the farmers of an agricultural system that could affect their quality of life.Keywords: Dermal exposure assessment; farmers; imazapic; hazard indexeISSN 2398-4279 © 2018. The Authors. Published for AMER ABRA cE-Bs by e-International Publishing House, Ltd., UK. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer–review under responsibility of AMER (Association of Malaysian Environment-Behaviour Researchers), ABRA (Association of Behavioural Researchers on Asians) and cE-Bs (Centre for Environment-Behaviour Studies), Faculty of Architecture, Planning & Surveying, Universiti Teknologi MARA, Malaysia. https://doi.org/10.21834/ajqol.v3i11.127
Abstract. Groundwater Pollution risk (GPR) map which utilized groundwater quality is important in order to prevent the groundwater contaminant concentration due to the agricultural activities. DRASTIC model and GIS application are two important tools that had been used for accessing and predicting the quality of groundwater. These supplementary tools are calculating, visualizing, and presenting the GPR by using DRASTIC index for each hydrogeologic factor through ArcGIS software. This study was covered approximately Selangor basin area where the GPR has been defined. There are four categories of agricultural activities in the Selangor basin which are animal husbandary areas, horticultural lands, short term crops and tree, palm and other permanent crops. The map showed that the "low" zones of GPR occupied 56% of the east side of the Selangor basin, 34% of the west side of the Selangor basin exposed to "medium" zones of GPR and the "high" zones of GPR covered 10% at the north side and the south to the west side of the Selangor basin. As a particular, for agricultural activities which is 52% of Selangor basin area, the "low", ''medium" and "high" zones of GPR was occupied as 42%, 43% and 15% respectively. Based on four categories of agricultural landuse, GPR map validated by nitrate distribution map, shows that the 99% of the variation in nitrate distribution zones are explained by GPR zones. In conclusion, groundwater pollution risk was affected by agricultural activities.
Water productivity (WP) is a key indicator of agricultural water management, since it affects the quantity of water used for crop yield in various management scenarios. This study evaluated the WP of irrigated rice due to a changing climate in the Northwest Selangor Rice Irrigation Scheme (NSRIS) by using field experimental data and the FAO-AquaCrop Model. Pertinent soil, water, climate, and crop data were acquired by executing a field investigation during the off-season (dry season, January–April) and main season (wet season, July–October) in 2017. The AquaCrop 6.0 model was calibrated and validated using the measured data. A Climate-smart Decision Support System (CSDSS) with an ensemble of 10 Global Climate Models (GCMs) was used to downscale climate variables under RCP4.5, RCP6.0, and RCP8.5 emission scenarios during baseline (1976 to 2005) and future (2020 to 2099) periods. The AquaCrop model fairly predicted rice yields under field conditions with root-mean-square error (RMSE), mean absolute error (MAE), prediction error (PE) and index of agreement (d) between the observed and estimated yields of 0.173, 0.157, −0.31 to 5.4 and 0.78, respectively for the off-season; and 0.167, 0.127, −5.6 to 2.3 and 0.73, respectively for the main season. It predicted a 10% decrease in actual crop evapotranspiration (ETc) in both crop seasons in the future. The WP of rice based on total water input (WPIrr+RF), applied irrigation (WPIrr), and actual crop evapotranspiration (WPETc) will likely increase by 14–24%, 14–19%, and 17–29%, respectively under the three RCP emission scenarios in the off-season. The likely increase in WP for the corresponding base is 13–22%, 15–24%, and 14–25% in the main season. Various agronomic management options linked to WP will most likely become important in making crucial decisions to cope with the risk of impacts on climate change.
Herbicide is a well-known artificially synthesized substance used in paddy fields as an effective way to increase the quantity and quality of rice production by controlling the weedy rice in the field. In Tanjung Karang area, a new paddy strain was introduced to avoid weedy rice problem which requires farmers to apply herbicide containing imazapic and imazapyr which kills the weedy rice only but does not affect the new paddy strain. However, imazapic has the possibility to cause several health problems and also disrupting aquatic ecosystem. Hence, this research aims to carry out an extraction procedure and detection for imazapic residues in surface water and groundwater to assess its distribution in the study area. In this study, samples were collected from the surface water and groundwater for two consecutive seasons of paddy cultivation. After several clean-up and extraction procedure using solid-phase extraction (SPE) method, the water samples were analyzed using High Performance Liquid Chromatography-UV (HPLC-UV) for the presence of Imazapic residue. In 52.6% of the surface water samples and 51.8% of the groundwater samples, presence of imazapic residues was detected. This is a concern as it may possibly cause harm to the farmers. Results showed significant difference for the level of imazapic concentration detected in surface water during main season and off season (p-value=0.005, CI = - 0.39, 0.11). Thus, it can be concluded that the concentration of imazapic residue detected during main season (o.71 ug/ml) was higher compared to the samples collected during off season (0.57 ug/ml).
Electrical Resistivity Tomography (ERT) analyses have been conducted in Irrigation Paddy Scheme, Tanjong Karang, Malaysia as part of investigation on groundwater potential aquifer to provide an alternative water resource for paddy irrigation. Based on recent studies on groundwater resistivity in paddy field, irrigation system mentioned as soil moisture content was observed to affect the value of electrical resistivity and subsurface geological profile resulted from ERT analysis. The objective of this study was to proof any correlation between soil moisture content and electrical resistivity values and to determine at what level of soil moisture content which will be the best condition to conduct ERT survey. ERT analysis was conducted by using ABEM Terrameter SAS 4000 of Wenner-Schlumberger array with 5.0 meter and 10.0 meter for minimum and maximum electrode spacing. Visually, based on subsurface geological profile resulted from ERT analysis soil moisture content affected (changed) electrical resistivity values. With all different treatments of soil moisture ranged from 16.96% to 27.50%, electrical resistivity values decreased in certain points and in certain depth along with the increase of soil moisture content. This was proofed by ANOVA and Duncan's multiple range tests showing that Pr > F value was less than 0.0001. Further on Chi-square test showed that at soil moisture level of 22.54%, it was the best condition which gave more correct counts of electrical resistivity values compared to well lithology. This was assumed to be the best condition to conduct ERT survey.
Seawater intrusion is threatening freshwater resources in coastal regions worldwide. Modelling this phenomenon can help in the management and control of such problems. This study presents a numerical model of seawater intrusion in a semi-confined aquifer in the lowland area of the Langat basin, Selangor, Malaysia, where groundwater is the only source of water supply for mega industrial projects. To provide useful measures for protecting groundwater from pollution by seawater intrusion, a three-dimensional numerical model, Seawat-2000, was applied.The numerical model incorporates regional geological, geographical, and hydrogeological features. The input parameters to the model were determined from well logs, well drillers' reports, and pumping tests. After the model was calibrated using data for the year 2010, the model was used to predict the extent of seawater intrusion for the future (2011-2045) assuming that the current condition of the Langat basin remains unchanged. The results show that the aquifer in the study area will be significantly influenced by seawater intrusion for the next 35 years.
Subsurface geological formation is essential in investigating the groundwater occurrence. The formation can be determined from subsurface resistivity value through electrical survey. However, there is ambiguity in interpreting the subsurface resistivity. Therefore the purpose of this study is to delineate the subsurface geological formation through combination of resistivity and induced polarization analysis. The type of geological formation is determined from resistivity analysis and well lithology. Meanwhile the fracture, water in clayey soil and groundwater occurrence is identified through combination of resistivity and induced polarization analysis. It has been identified that the study areas consist of fractured aquifer. Possible groundwater fractured area can be indicated by low resistivity ranged from 700 to 2000 Ωm and overlapped with low chargeability ranged from 1 msec to 2 msec. This study provides useful information on nature of groundwater occurrence especially fractured aquifer.
A 2D surface electrical resistivity is one of non-destructive methods to investigate groundwater. In this study, 2D resistivity method was used to produce subsurface imaging profiles which are known as ERT (Electrical Resistivity Tomography) at Block C, Sawah Sempadan, Tanjung Karang, Selangor. These ERT profiles were then used to create 3D model view of potential aquifer at the study area. Overall, there were 3 ERT profiles of 1600m for major survey lines and 6 ERT profiles of 400m for minor lines. ERT profiles were then compared to lithology log from nearby tube wells of same geological formation in order to locate potential aquifer location in these profiles. Results show that there were 7 locations of identified potential aquifer in this study area. Later, the resistivity data were added with longitude and latitude data before imported into Voxler to achieve the objective of the study. The 3D model view of skeleton shape was productively built in Voxler as it visibly illustrates the whole subsurface profiles of study area. Locations of potential aquifers were identified in this 3D model view to show the exact location and depth of each potential aquifer.
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