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Pesticide Occurrence in Shallow Depths of Groundwater in Central Bangladesh

Nepal C. DEY
Division of Bioenvironment Science, Tottori University, Japan

Lucky GHOSE
Sylhet MAG Osmani Medical College, Sylhet

Muhammed A. BHUIYAN
Department of Water Resources Engineering, BUET, Dhaka, Bangladesh

Asim K. SAJJAN
Roads and Highways Department, Sarak Bhaban, Dhaka, Bangladesh

Abstract/ Executive Summary:

Groundwater samples were collected from three types of tubewells namely, treadle pump, hand tubewell and shallow tubewell which were settled at 3-5m, 8-15m and 20-30m deep respectively. A total of 60 samples were collected from 30 tubwells for laboratory analysis. Physico-chemical parameters of water such as pH, electrical conductivity, total dissolved solid, total alkalinity as well as sodium, potassium, calcium, magnesium, iron, carbonate, chloride, sulfate and nitrate concentrations were measured and integrated in water quality index. Solid phase micro-extraction followed by gas chromatography (GC) with electron capture detector (ECD) was used for the detection of organochlorine (OC) pesticides in water samples, and high performance liquid chromatography (HPLC) also for organophosphorous (OP) and carbamate pesticides. Some trace elements of pesticide residues were found in case of some types of pesticides, which were not detectable. The water quality indexes of the three tubewells were on the acceptable level (80 to 94) as “good” for drinking as well as household uses.

Keywords: Shallow Groundwater, Quality, Pesticide, Tubewells

Location: Shibpur Upazila of Narsingdi District, Bangladesh

Start Date:

End Date:

Program Area: Risk Management in Agriculture

Commodity: Pesticide

Objectives:

The objective of the study is, therefore, to assess the quality of shallow groundwater for drinking purpose and to detect pesticide residues in the groundwater of the study area.

Methodology:

Study Area: The study was carried out at Shibpur Upazila of Narsingdi District, Bangladesh. It is situated between latitudes 24º07´ and 23º56´ (N) and between longitudes 88º10´ and 89º50´ E. The Upazila is comprised of 9 unions with a total area of 20,586 ha. Water sampling: The study was as a part of the Groundwater Quality Assessment (GWQA) project during 2002-2003. A total of 30 tubewells at 10 sampling sites were selected considering characteristics such as depth of groundwater table, water use, cropping pattern, and pesticide application. Water samples were collected from three types of tubewells namely, treadle pump, hand tubewell and shallow tubewell at each site which were screening depths 3-5m, 8-15m and 20-30m, respectively. Coordinates of the tubewells were fixed with a Differential Global Positioning System (Garmin DGPS 12XL). Groundwater samples were collected in May and September which were in the dry and rainy season, respectively. Before water samples were collected, each site was pumped until field measured values of pH, water temperature, specific conductance, and dissolved oxygen concentration stabilized. Samples of water for physicochemical and microbiological analyses were collected in 1-liter glass bottles and kept at 4ºC until analysis conducted. Samples for pesticide analysis were collected in 1-liter amber backed glass bottle and immediately chilled before shipment to the laboratory and kept frozen until analysis conducted. Reagents and standards: Analytical grade chemicals were used throughout the study. Double distilled water was used for preparing all the reagents and calibration standards. The experiments were carried out in triplicate. Physicochemical analyses: Temperature (T), pH, electrical conductivity (EC), turbidity (Turb), and salinity (S) were measured in situ using field kits. The quantities of Na, K, Ca, Mg, and Fe in water were detected using Atomic Absorption Spectrometer (AAS) and Inductively Coupled Plasma Atomic Emission Spectrometer (ICP-AES), and quantification of carbonate (CO₃ 2-) by titration with 0.05 normal H₂SO₄, amount of chloride (Cl1-) based on electrometric titration of H₂O by chloriodometer, nitrate (NO3-) by flow injection analyzer, sulfate (SO₄ 2-) using Inductively Coupled Plasma Atomic Emission Spectrometer (ICP-AES), total dissolved solids (TDS) by oven drying and gravimetric analysis in the Environmental Monitoring and Control laboratory of the Department of Shipping. 2.5 Water Quality Index: The Water Quality Index was calculated from the number of failed variables whose objectives are not met with the standard value divided by the total number of variables based on Canadian Council of Ministers of the Environment (CCME-2001) Water Quality Guidelines. Pesticides analysis: Collected samples were analyzed in the Agrochemical & Environmental Research Division Laboratory, Institute of Food and Radiation Biology of Atomic Energy Research Establishment (AERE), Savar for detecting the pesticide residues. In the laboratory, Gas Chromatography (GC)- Hewlett Packard 5890 II system with and High Performance Liquid Chromatography (Waters 716) were used to analyze the pesticide compounds in groundwater samples. Two samples were prepared from each bottle for duplicate analysis. Each sample container was shaken well and 250 ml sample was transferred to a separating funnel. Double distilled 1000 ml n-hexane was added and well mixed by shaking for 5 minutes. Hexane portion was separated and collected in an evaporating flask. Water portion was mixed with 50 ml hexane and shacked repeatedly for two more times. Hexane extract was combined and 5.0g anhydrous sodium sulfate was added. After 5-10 minutes, the hexane extract was transferred to a round flask. The extraction was concentrated using rotary vacuum evaporator and finally evaporated to dryness under N2. The residue was quantitatively transferred to a 5 ml volumetric flask and made a volume with nhexane. Aliquot was injected at the GC-ECD. A portion of the extracted residue was subjected to clean up using florisil column and 3% diethyl either in hexane was used for elution. GC-ECD model was used for the detection of Organochlorine and HPLC also for Pyrethroid & Carbamate pesticides residues.

Source of Information: International Conference on Water & Flood Management (ICWFM-2007), 12 - 14 March 2007, BUET, Dhaka, Bangladesh

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

The groundwater of the study area is good for drinking and household uses. The concentrations of most of the physico-chemical parameters, were within the standard limit for drinking except pH and iron in some locations. The pH values of some of the treadle pump’s water were less than the safe limit as well as iron concentrations of some tubewells were beyond the standard limit for drinking established by the Ministry of Environment and Forest, Bangladesh as well as the World Health Organization (WHO) limit. The study area was free from pesticide contamination, also some trace elements of pesticide residues were found in the case of some type of pesticides, which were not detectable. The water quality indices of the three tubewells were on the acceptable level. Hence water of the study area was good for drinking as well as household uses. A survey was conducted by BGS/DPHE proved that the groundwater of this areas was free from arsenic, a commonly occupying toxic element of groundwater in Bangladesh. Therefore, groundwater of this area is suitable for drinking, except water from some treadle pumps are still contaminated. Continued monitoring of these wells on a yearly basis would provide a better understanding of pesticide variability and persistence in groundwater. The findings of the study can be used as a guideline for better understanding of the proper usefulness of groundwater utilization in the study areas.

Knowledge Management: Report/Proceedings