Assessment of Commonly Used Pesticides in the Ground Water of the Shallow Aquifer Systems in Jericho and Jeftlik areas/ Lower Jordan Valley, Occupied Palestinian Territories
Abstract
One of the most important pollutants that may reach the groundwater thro ugh agricultural return flow combined with abuse and ignorance is pesticides. This study focuses on the examination of the concentration of three pesticides: Abamectin, Imidacloprid, and ß -Cyfluthrin, all of which have been used in large quantities in the Lower Jordan Valley (LJV) for the last three decades. Twenty five groundwater samples were collected from water boreholes where water is Abstracted from two phreatic aquifer systems which are the Plio -Plistocene aquifer system in Jericho and Lower Al Jeftlik areas and the Eocene carbonate aquifer system in the Middle of Al Jeftlik. The depth of the boreholes in both aquifer system ranges between 80 and 120 m. Water samples were analyzed for Abamectin, Imidacloprid, and ß -Cyfluthrin using the HPLC -UV method. These samples represent two main agricultural locations (Jericho, and the Al Jeftlik). Of the 25 wells sampled, Abamectin was detected in 11 wells in concentrations ranging between 1.24 ppb and 81.71ppb. Imidacloprid was detected in 24 wells in concentrations ranging between 1.60ppb and 325.0ppb. Finally, ß -Cyfluthrin was detected in 7 wells in concentrations ranging between 1.10 and 24.46ppb.
Aquifer lithology, groundwater flow directions, type of agricultural activity are major factors in controlling pesticide concentrations in groundwater. The highest values were measured where the aquifer consists of gravel and sand sediments, combined with intensive agricultural activities, followed by sand -silt aquifer. The lowest concentrations were found in boreholes where carbonate aquifer is the main source of water which indicates that other source of water flow into the system . The results of this study demonstrate that these pesticides are used heavily and in an improper way in the lower Jordan Valley, increasing the risk of adverse environmental and public health effects. Much attention should be given to addressing the potential problem of environmental and groundwater contamination by these pesticides.
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Introduction
Pesticide usage is one of the major fundamental problems that threaten groundwater quality in many areas of the West Bank the degree of risk depends on the amount of pesticides added to the field, the physical properties of the unsaturated zone, and the environmental classification of the chemicals as a function of the duration of time in the environment.
Jericho District locates in the Lower Jordan Valley area and consider as the food basket for the West Bank. The climate of the area is hot and dry during summer and mild in winter. The annual rainfall average is about 300 mm in Jeftlik area in the north and decrease southwards to about 200 mm in Jericho [1]. Due to high evaporation rates, agricultural activities without irrigation practices are impossible. Sources of water in the two locations is limited to groundwater wells taping water from the Shallow aquifer system of Plio-Plistocene ages, that consists of alluvial sediment overlaying carbonate rock of Eocene age.
The aquifer systems have different water shed, in Jericho area groundwater flow from the carbonate Mountain aquifer east wards crossing the fault system into the Plio-Plistocene aquifer system [2], where in Al Jeftlik area groundwater infiltrated from the surface during flooding period as well as from agricultural return flow, and laterally from west to east parallel with the Graben axis. The alluvial, gravel, sand sediments is overlaying the limestone layers of Eocene age where both formation consider as one aquifer system. In both areas direct recharge from rainfall is limited [3-4] and agricultural return flow can influence the quality of groundwater.
Analysis of groundwater samples indicate that agricultural contaminants come from three main agricultural ingredients; these are: 1) bromide, which is injected as a fumigant onto the land in the form of a methyl bromide gas; 2) nitrogen fertilizers, pesticides, and animal manure; 3) and nitrate, chloride, magnesium, and lithium compounds which might appear in surplus amounts due to irrigation back flow and infiltration of the groundwater with soil [5]. The cultivated areas in the Jericho District including two locations is about 2,419.4 hectares and the amount of pesticides used is about 82 tons per year [6].
Pesticide usage raises a number of environmental concerns. Each use of a pesticide carries some associated risks, but proper pesticide usage decreases these risks. The presence of pesticides in groundwater, even in low concentrations, is enough to cause a variety of adverse health effects, such as causing cancer and reproductive success [7] [8] [9][7-8].The acceptable limit for a pesticide in groundwater is 0.1 ppb and 0.5 ppb for multiple pesticides [10] [11]. Pesticide contamination of groundwater is a subject of national importance. This especially concerns people living in the agricultural areas where pesticides are most often used, as about 95 percent of that population relies on groundwater for drinking water. The misuse of pesticides had increased in occurrence in groundwater in the northern part of the West Bank and in the Gaza Strip[12]. Using water contaminated with pesticides for drinking purposes has a potentially high health risk [13] .
Abamectin, Imidacloprid, and ß-Cyfluthrin have been used in large quantities in the Lower Jordan Valley. Imidacloprid acts as a neurotoxin and is considered a potential groundwater contaminant [14-15].The pesticide Abamectin has adverse effects on the aquatic environment (daphnia and fish) [14] [15,16] and has the potential to cause hepatotoxicity [5]. ß-Cyfluthrin is a potent neurotic and can cause significant weight reduction [6-7].Therefore, the heavy use of these pesticides could cause high environmental and health risks. The main objective of this study is to investigate the concentration of these three majorly used pesticides (Abamectin, Imidacloprid, and ß-Cyfluthrin) in the groundwater of the Shallow aquifer system in Jericho and Jeftlik areas. The results of this study will be used in risk characterization of pesticides in drinking and groundwater in the Jericho District.
Conclusion
Groundwater from the shallow aquifer system in the Lower Jordan Valley is mostly contaminated with the three pesticides studied (Imidacloprid, Abamectin, and β -Cyfluthrin) in higher amounts than the accept able limit. At least one of the three pesticides was detected in the 25 groundwater samples. From the 25 samples of groundwater analyzed, detectable levels of Imidacloprid, Abamectin, and β -Cyfluthrin were found in 24, 11, and 7 samples, respectively. The total concentration of these three pesticides in the groundwater ranged from 4.72 ppb to 341.36 ppb. The lowest total concentration of the three pesticides was still higher than the acceptable limit of total pesticides for drinking water. The estimated environmental concentration of Imidacloprid in the groundwater is 2.09 ppb [29], yet it reached up to 325 ppb in the study area. Moreover, it has been estimated that Abamectin's instability as well as its low water solubility and tight binding to soil prevent s it from leaching into groundwater or entering the aquatic environment. The results of this study indicate that Abamectin was found in 44% of the samples tested, with concentrations ranging between 1.24 ppb and 81.72 ppb, indicating the heavy and improper use of these pesticides in the study areas. This could result in the manifestation of several health and environmental problems. As such, immediate attention should be given to the potential problem of environmental and groundwater contamination by these pesticides.
Well depth and lithological characteristics of the sediments play an important role in the transport process of pesticides fr om the surface to the ground water. A time series analysis for pesticides concentration in groundwater is needed. Also, a substantive decrease in the amount of pesticides applied annually on agricultural lands in the study area is strongly recommended.
