Preliminary Study on Deltamethrin Residues in Cabbage, Soil and Water from Dalaguete, Cebu, Philippines
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KIMIKA Volume 27, Number 1, pp. 1-11 (2016) © 2016 Kapisanang Kimika ng Pilipinas All rights reserved. Printed in the Philippines. ISSN 0115-2130 (Print); 2508-0911 (Online) https://doi.org/10.26534/kimika.v27i1.1-11 Preliminary Study on Deltamethrin Residues in Cabbage, Soil and Water from Dalaguete, Cebu, Philippines Armstrong Calinawan1, Concepcion S. Mendoza2 and Leonila Adarna1* 1 Chemistry Department, University of San Carlos, Cebu City 2 Department of Mathematics and Sciences, German University of Technology in Oman, Muscat, Oman Pesticides pose a threat to the environment and eventually human health. Extent of contamination of pesticides can be determined and monitored by analysis of pesticide residue in surface water, sediments, soil, and biota. Samples were collected from Manlapay, Barangay Mantalongon in Dalaguete, reportedly the vegetable basket of Cebu, from October to November 2013. Concentration of the pesticide deltamethrin was determined by Gas Chromatography-Electron Capture Detector along with organic matter content (OM), potassium (K) and cation exchange capacity (CEC) using standard methods of analysis. Data showed that deltamethrin was found to be present in soil and cabbage and beyond detection limit in water. Inverse relationship was found between residue in cabbage and in soil confirming pesticide leaching as supported by rainfall data. Organic matter and cation exchange capacity in soil showed significant correlation to detected deltamethrin residue confirming that pyrethroids are strongly bound to organic matter and free exchangeable potassium ions. Deltamethrin residue in water does not show any correlation to any other parameters as it is beyond detection limit, probably due to volatilization and photodegradation of deltamethrin in water. Temperature variation does not show significant difference to deltamethrin residue in all three matrices. The detected deltamethrin residue concentrations in the cabbage (<0.001-0.029 ppm), soil samples (0.007-0.008 ppm) and water samples (<0.0005 ppm) were all below international guideline limits (ASEAN maximum level of 0.5 ppm deltamethrin in cabbage, EC ecologically accepted concentration of 1290 mg deltamethrin/kg soil, and a maximum limit of 0.0025 ppm deltamethrin according to Canadian water quality, respectively). Inspite of the low concentrations detected in cabbage, soil and water samples, an extensive pesticide monitoring on environmental samples within the area is advisable. This will help the adoption of an efficient risk assessment strategy to inform appropriate interventions. Keywords: deltamethrin; cabbage; water; soil; Cebu, Philippines INTRODUCTION Agriculture is still the most common form of employment in the Philippines and the current industrial agricultural system depends much * Author to whom correspondence should be addressed; email: leonila [email protected] 2 Armstrong Calinawan, Concepcion S. Mendoza and Leonila Adarna on agrochemicals like pesticides and synthetic EXTOXNET, 1996; PAN, 2010), but can be fertilizer. Pesticides have been widely used in prevented with necessary precautions. agriculture due to its profit based advantages which includes better crop quality, higher Studies on toxic effects of deltamethrin are farm yield and minimal labor requirement very less (Rehman, et al., 2014). There is the (Chen et al., 2011, Osman et al., 2010). need to investigate the toxic effects of deltamethrin and other pyrethroids and to The commonly used chemical pesticides are reduce pesticide risks to humans and the carbamates, organophosphates, organo- environment. In the Philippines, though chlorines and pyrethroids. Pyrethroids are pesticides are used extensively, but related synthetic pyrethrum derivative which are pesticide studies are also limited (Davis, 1993). widely used to control insect pests due to their Even simple data on pesticide residue level in high insecticidal potency (Zhou et al., 2011). areas where the pesticide is used is not easily Both, market and scientific interests on available due to lack of analytical technology. pyrethroids had also increased due to its In this study, deltamethrin residues in characteristics of being readily decomposed cabbage, in soil and in water were assessed to under ultra-violet rays and as neurotoxicants obtain preliminary information on the status with low mammalian toxicity (Soderlund et al., of deltamethrin residues in one of the Cebu- 2002). cabbage growing areas; from Manlapay, Barangay Mantalongon in Dalaguete, Deltamethrin is one type of active ingredient reportedly the vegetable basket of Cebu. Some belonging to the type II pyrethroid pesticides, factors that may affect the transport and which is approved for use in the Philippines persistence of deltamethrin are also studied. (DA-FPA 2007), as substitute to the highly toxic pesticides. Deltamethrin [IUPAC name: EXPERIMENTAL (S)--cyano-3-phenoxybenzyl (1R,3R)-3-(2,2- dibromovinyl)-2,2-dimethylcyclopropane Description of Sampling Site and Sample carboxylate and molecular formula of Collection. The study was conducted in an C22H19Br2NO3] is a slightly water soluble agricultural farm in Manlapay, Mantalongon, compound with very low vapor pressure and Dalaguete, Cebu. The farm uses terracing high phostostability, making it one of the less techniques to prevent soil erosion and rapid readily degraded pesticide and allowing the nutrient leaching. The terraces has 3 steps and possibility of accumulation to environmental each is called an andene. Each andene is about sinks. Deltamethrin is considered the most 150 square meters in area. A two-meter buffer powerful and most toxic of the pyrethroids zone was set for each andene. Each step of the (EXTOXNET, 1996). Deltamethrin residues andene was designated as top, middle and are expected to be distributed with different bottom sites for cabbage and soil sampling ratio in vegetation, soil, water, air, living purposes. Table 1 shows the GPS coordinates creatures and crops resulting to several of the sampling site. Sampling was done ecological risks, particularly by causing algal during October to November 2013. blooms, toxicity to aquatic organisms and reducing bee populations and associated Table 1: GPS Coordinates of the Sampling pollination service (EXTOXNET, 1996). Sites. Deltamethrin can remain long time in the soil, Sample Area GPS Elevation and are absorbed by the crops, and eventually Collected Assignment Coordinates Cabbage and N 09°52’16.9” flow out of the arable land to the surrounding Top 595 m Soil E 123°29’01.1” environments. Deltamethrin can also Cabbage and N 09°52’16.4” Mid 592 m bioaccumulate in the food web and pose Soil E 123°29’01.6” Cabbage and N 09°52”16.9” Bottom 578 m adverse effect on humans. Deltamethrin was Soil E 123°29’02.4” N 09°52’28.3” also found to cause a variety of acute health Water Water Effluent 554 m conditions on humans (INCHEM, 1990; E 123°28’30.3” KIMIKA • Volume 27, Number 1, January 2016 Preliminary Study on Deltamethrin Residues in Cabbage, Soil and Water… 3 For each sampling site, at least five six-inch minute. Approximately 6.2 g of anhydrous deep holes were one meter away from each MgSO4 was added and the mixture was other. Composite soil samples were collected vigorously shaken for 1 minute. The mixture from the holes, combined and placed in was centrifuged and about six millilitres of the properly labelled re-sealable plastic bag and clear liquid solution was allowed to pass temporarily stored in a cooler with ice before through a C18 column and eluted with 20 mL transporting it to the laboratory. dichloromethane. The eluent was concentrated to near dryness in a rotary eva- Four cabbage heads, heads and roots, were porator at a water bath temperature of 40 °C. randomly collected per andene. Soil strongly bound to the root system, the rhizosphere, Extraction and GC-ECD Injection. The was mixed with the composite soil samples remaining extracts collected during water before all the cabbages were mixed. Cabbage sample preparation was redissolved with 5 mL samples were placed in properly labelled re- of n-hexane: acetone mixture (70:30) and sealable plastic bags and temporarily stored in sonicated for complete dissolution. A florisil a cooler with ice before transporting it to the solid phase extraction cartridge was laboratory. conditioned and washed with 5mL of of n- hexane followed by 5 mL of n-hexane-acetone Water samples were collected from the water mixture (70:30). Samples were then loaded to catchment located downhill about 20 meters the prepared cartridge and eluted with 10 mL from the farm. One liter of water effluent was n-hexane:acetone mixture (70:30). The eluate collected and placed in acid-washed was collected, evaporated to near dryness, polypropylene bottles and stored in a cooler redissolved with 2 mL and injected into the with ice. GC instrument. Deltamethrin Pesticide Analysis. The The above step was also done for extracts analytical samples were taken and prepared collected during soil sample preparation. accordingly (Thier et al., 1991). Similar step as stated above was performed for the extract collected during cabbage Water. About 1 g NaCl was added to 50 mL sample preparation. However, instead of using water, shaken with 50-mL portions of hexane hexane-acetone mixture, acetonitrile was used on a filtered water sample. The filtered hexane in the washing the florisil solid phase cartridge layer was dried on Na2SO4 and concentrated to and in the GC elution process. near dryness in a rotary evaporator at a water bath temperature of 40 °C. Table 2. GC-ECD working condition Soil. A 15 g of homogenized, screened and air Injector 250˚C dried samples and spiked soil samples were temperature Detector obtained and added with 80 mL acetone. 300˚C Temperature Approximately 10 g of anhydrous Na2SO4 was Oven 120˚C hold for 1 minute, added and the mixture was shaken for 1 hour. Temperature 9˚C/min to 285˚C The mixture was filtered and the residue Program further washed with 20 mL of acetone. The Carrier Gas Nitrogen (GC grade) combined filtrate was concentrated to near Make-up Gas Hydrogen (GC grade) Column Flow dryness in a rotary evaporator at a water bath 3.0 mL/min temperature 40 0C.