Hydrogeochemistry investigation on groundwater in Kuala Langat, Banting, Selangor

This paper emphasized the hydro geochemistry of groundwater in Banting, Kuala Langat, Selangor and the hydrogeological properties which contribute to the potential degrading of the quality of the groundwater. The groundwater characteristics in Banting, Kuala Langat, Selangor are influenced by aquifer types and the geomorphology of the area. Groundwater samples were collected at thirteen monitoring wells from February 2017 to January 2018. The thirteen selected monitoring wells for this study is scattered in agricultural areas. The investigation of groundwater measured the physical parameters which are total dissolved solid, electrical conductivity, salinity and chemical oxygen demands. Major ions such as chloride, calcium, magnesium, potassium, sodium bicarbonate and strontium were also calculated. Iron, manganese and zinc which are heavy metal elements together with phosphate, nitrate and sulfate were considered as inorganic parameters in this analysis. The groundwater samples have influences from the seawater intrusions as significantly high major ions concentration were detected. Non-point pollution from the agricultural practices does not deteriorate the groundwater quality even though the monitoring wells are located in agricultural areas. Groundwater sources in the current study are suitable for domestic use and agricultural irrigation. Keyword: Groundwater, hydro geochemistry, seawater intrusion INTRODUCTION Groundwater is an essential natural resource to the whole living things sustainability. Water scarcity is a highlighted issue that has to be overcome in order to accommodate sufficient clean water sources for drinking and domestic purpose. Hence, sustaining the good quality of groundwater becomes crucial to ensure the groundwater source is safe to human health to avoid any health threat. This current research focused on the groundwater located near coastal areas. The monitoring wells in Banting, Kuala Langat are situated near Morib beach. Potential influence to the quality of groundwater through seawater intrusions therefore exists. This study aims to highlight the potential physicochemical properties which can affect the groundwater sources. Groundwater geological aspects Geological condition of an area has a significant influence on the mineral composition of groundwater as it is affected by the soil characteristics and mineral contents of the soil (Azlan et al., 2012). Pollutants which exist in the soil derived from heavy metals concentrations also has influence on the mineral contents of the groundwater and its quality. Alluvium soils which are soft soils usually exist in agricultural lands. This clayey type of soil with high water holding capacity and low porosity contains high mineral content and organic matter. Soil rich with organic matter and mineral content such as ammonia and sulfate are suitable for agriculture and plantations. However, these substances would also highly exist in the groundwater. The anthropogenic pollutants can potentially affect the aquifer systems and together with precipitation, will increase the hydro chemical composition of groundwater (Shamsuddin et al, 2015). MATERIAL AND METHOD Study area Banting, located in the district of Kuala Langat, Selangor (857.65 km2) and situated at latitude 2°48’34.4”N and longitude 101°30’11.8”E was chosen as the study area. Banting is known as an agricultural hub. The study area consists of oil palm plantations and a variety of crops as well as vegetable gardens. The study area represents a part of the Langat River Basin. The monitoring wells in this study are in alluvial areas. The geology of the area is represented by the quaternary geology, that consists of marine and continental deposits such as silt, sand and peat with minor gravels. ln the area of the monitoring wells, the groundwater recharge is from the hilly areas and mountains upstream. Generally, the aquifers are extensively disseminated in the flat lowlands. The Kuala Langat monitoring wells are divided into two sub-areas, i.e. Northern Kuala Langat and Southern Kuala Langat. Monitoring wells BKLTW12, MW01, MWD4, BKLEW2, MW05, BKLTW19, MWD2 and MWD5 are located in the Northern Kuala Langat area and are shallow in depth, approximately 4 to 35 meters. Monitoring wells BKLTW16, J7-1-4, BKLTW11, BKLTW15 and BKLEH29 are located in the Southern Kuala Langat area where the depth of wells are more than 60 meters. Figure 1 shows the locations of the thirteen monitoring wells. DOI : https://doi.org/10.7186/bgsm67201916 0126-6187; 2637-109X / © 2019 Geological Society of Malaysia. All rights reserved. Bulletin of the Geological Society of Malaysia, Volume 67, June 2019, pp. 127 – 134 Hazimah Haspi Harun, Mohamad Roslan M.K., S. Nurhidayu, Zulfa Hanan Ash’aari, Faradiella Mohd Kusin Bulletin of the Geological Society of Malaysia, Volume 67, June 2019 128 Groundwater sampling The physicochemical characteristics of the groundwater samples were assessed to evaluate the effect on groundwater sources. The in-situ parameters were analyzed at each monitoring wells; the temperature and total dissolved solids using calibrated Myron L Ultrameter 6P. A Thermo Scientific Orion 3-star Portable pH meter was used to measure pH, while the YSI 30 Salinity and Conductivity meter was used to measure salinity and conductivity. Turbidity was measured using Thermo Orion AQ4500 Turbidity Meter. The groundwater sampling procedure and analysis were carried out following the guidelines by APHA and the Department of Mineral and Geoscience Malaysia (APHA, 2012). Groundwater samples were collected from thirteen monitoring wells with shallow aquifer (less than 22.0 m), intermediate (22.0 m to 40.0 m) and deep aquifer (more than 40.0 m in depth) (Sefie et al., 2015). The sampling was conducted from February 2017 to January 2018. This field verification sampling was necessary to determine the selected groundwater quality parameters. The groundwater samples were pumped using the submersible groundwater pumps and the groundwater level meter was used to measure the groundwater depths before and after the sampling process. The purging pump was used to remove the stagnant groundwater for approximately 15 to 30 minutes to ensure the groundwater samples did not consist unnecessary elements during the sampling procedure (Appelo & Postma, 2005). RESULTS AND DISCUSSION Groundwater hydro geochemistry analysis Physical characteristic and inorganic parameters The collected groundwater samples were analyzed for physical characteristics, major ions, heavy metals and Figure 1: Monitoring wells in Banting, Kuala Langat. inorganic parameters. Sample from MDW5 monitoring well was most vulnerable to pollutants. This monitoring well is situated in Sungai Lang, Banting and is within an oil palm plantation. Results from the analysis indicate high pollutant content in this monitoring well for the parameters analyzed. Besides that, the electrical conductivity, salinity, chemical oxygen demands, nitrate and phosphate levels were also highest in MWD5 monitoring well. The electrical conductivity revealed high concentration in the groundwater among all the monitoring wells. The ion of dissolved salt from total dissolved solid concentration in the groundwater influencing the flow of electrical current was directly proportional to the increasing electrical conductivity in groundwater bodies. However, for the high electrical conductivity recorded in the groundwater bodies, there are several factors which need to be taken into considerations such as the land uses and geology around the monitoring wells. Electrical conductivity was high during dry season in a majority of the monitoring wells, similar to Awoyemi et al. (2014) in Lagos State, Nigeria. However, this finding contradicted the results of Reddy et al. (2011) where the increasing electrical conductivity was proportionate to the increasing water table whereas this study revealed that the electrical conductivity was high in low water table during the dry season. The monitoring wells in the current study are scattered in agricultural areas. Nitrates and phosphates apparently derived from fertilizers and manure applications at the oil palm plantations were the general substances in the groundwater samples from agricultural areas. The high chemical oxygen demand in groundwater samples from the monitoring wells significantly showed the degradation process occuring due to the decomposing of inorganic pollutants. The presence of nitrate, phosphate, and potassium from fertilizers and manures application such as NPK fertilizer from agricultural practices and oil palm plantations have a great discharge into surface water through leaching, runoff and sedimentation. These substances are accumulated in surface water and then infiltrates into the groundwater. These substances then contribute to the increasing electrical conductivity and deteriorate the quality of groundwater. The finding is similar to Reddy et al. (2011) where nitrate showed a positive correlation with electrical conductivity in agricultural monitoring wells. The concentration of the physical properties in groundwater samples are graphically explained in Figure 2 to Figure 7. Major ions Hydrogeochemistry in groundwater which is influenced by seawater intrusion and apparently from the geological formation presents a high concentration of major ions such as magnesium, calcium and sodium (Sajil et al., 2014). The hydrogeochemistry analysis of groundwater consists of analysis of the basic parameters i.e. chloride, calcium, magnesium, potassium, sodium and bicarbonate, and sulfate. These seven parameters represent 95% of the major ions in water solutes from a chemical aspect of groundwater • Morib • Banting • Tk. Datok • Tanjong Sepat • Kg. Dengkil BKLTW12