Pesticides in Ground and Surface Water
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Contents:
The most ubiquitous compounds were desethylterbuthylazine DET , pyrimethanil, cyprodinil and diazinon, and the compounds detected in highest concentration were simazine and degradation products derived from triazines. Las Cabras and Tahuilla irrigation canals presented the highest concentrations of pesticides. Significant differences were found in the total concentration of pesticides for sites sampled at the end of the summer and winter season.
However, the intensive use of these compounds can cause severe environmental pollution problems since they are distributed among water, soil, air and biota, affecting ecosystem biodiversity [ 1 — 2 ] and human health [ 3 ]. Pesticides can reach a body of water through drift during application, runoff, leaching toward the water table and washing of receptacles of machines after application [ 4 ].
Once in this medium, they can be partially or totally degraded, remain unchanged, be deposited in the sediment of rivers and lakes, become bioconcentrated in aquatic organisms or return to the atmosphere through volatilization [ 5 ]. Studies carried out in Asia [ 6 ], Europe [ 7 — 8 ] and the USA [ 9 ] show that pesticides and their degradation products are often detected in surface water, in some cases at levels exceeding the maximum individual limit 0.
Therefore, various countries around the world have developed monitoring programs to evaluate the level of pesticide contamination in bodies of water, taking the measures necessary to minimize the impact of these substances on the environment and protect the quality of water resources [ 11 ].
In Latin America, studies on water contamination by pesticides is a little-developed area; however, some studies have been done in Mexico, Nicaragua, Costa Rica, Brazil and Argentina, in which it was shown that bodies of water adjacent to agricultural areas can present elevated levels of pesticide contamination. For example, research done in Brazil shows that drinking water, surface water and groundwater in areas planted with cotton and sugar cane crops contain diuron, atrazine, simazine, ametryn and metribuzin in concentrations that exceed the maximum individual limit established by the EC [ 12 ].
Similarly, in Argentina it has been found that bodies of water adjacent to tobacco, onion, yerba mate, corn or soybean fields or orchards [ 13 ] present atrazine and terbuthylazine concentrations over the maximum limit established by the EC 0. Although there are few studies related to water contamination by pesticides in Chile, the research carried out to date shows the presence of agrochemicals in the surface water of agricultural areas of the central zone of the country.
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More than four hundred and fifty active substances are currently used for pest control in the country; therefore, it is crucial to evaluate the level of water resource contamination in Chile, mainly in regions with the greatest sales and use of agrochemicals. In order to achieve this it is first necessary to implement a robust analysis method for rapid and simultaneous determination of various types of herbicides, fungicides and insecticides in water samples that allow them to be evaluated with greater certainty. In general, the determination of pesticides in water is a laborious process, in which the sample taking and pretreatment stages require up to two thirds of the time necessary for the complete analysis [ 17 ].
Solid-phase extraction SPE as a pretreatment technique is one of the most used for the analysis of organic contaminants in aqueous samples and gas chromatography coupled to a mass spectrometry detector GC-MS is one of the most used techniques for evaluating the presence of these contaminants in the environment [ 18 ]. In the case of aqueous samples, various studies have used GC-MS to simultaneously determine organochlorine, organophosphorus, triazine and pyrethroid pesticides [ 19 ] with detection limits below 0. The objective of this work was to assess the changes in the presence of sixteen pesticides in river water samples in summer and winter periods in a basin in Central Chile with intense agricultural activity that of the Cachapoal River.
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Rainfall is very important in this area because they are intense and short-lived, concentrating between May and August with a monthly average of 68 mm. The compounds determined were four fungicides pyrimethanil, metalaxyl, cyprodinil, kresoxim-methyl , five herbicides simazine, fluometuron, atrazine, terbuthylazine, acetochlor , two insecticides chlorpyrifos, diazinon and five of their main degradation products [deisopropylatrazine DIA , deethylatrazine DEA , desethylterbuthylazine DET , diazoxon, CGA].
A multi-residue method through SPE and subsequent separation and quantification by GC-MS was proposed for determining pesticides [ 21 — 22 ] and the levels established by European Commission for drinking water were considered as a reference to determine contamination in the natural water samples from Central Chile. Ehrenstorfer Augsburg, Germany. Selected characteristics of compounds are included in Table 1. All data were taken from 1 EpiSuite Program V.
Compounds with letters in brackets correspond to the degradation products of the parent compound with the same letter in the superscript. During surface water samples were collected at various points in the Cachapoal River basin in Central Chile located in the region with the greatest pesticide sales in the country , comprising two rivers Claro and Cachapoal , two creeks La Cadena and Zamorano and two irrigation canals Las Cabras and Tahuilla.
Pesticides in ground, surface and drinking water are a hot topic under continuing discussion. This complete and authoritative volume draws together information. Commercial pesticide applicators, farmers, and homeowners apply about 1 billion pounds of pesticides annually to agricultural land, non-crop land, and urban.
This region has an area of km 2 and the main crops are grapes, apples, peaches, plums, cherries, nectarines, pears, oranges, walnuts, avocados and lemons Figure 1. Two samplings were carried out, one at the end of the summer April and the other in winter season July , with a total of thirty water samples collected eighteen in April and twelve in July. The samples were taken in 2-L amber glass bottles and transported to the laboratory in coolers with ice.
In less than 48 hours, they were passed through nitrocellulose filters with a pore size of 0. Self-elaboration based on data Fruit Catastro year [ 24 ]. The effects of sorbent type, the solvent used in the elution and pre-concentrated sample volume were previously evaluated to optimize the pre-concentration process by SPE. The residue was redissolved in 1. The effects of five organic solvents acetone, acetonitrile, methanol, hexane, ethyl acetate and a combination of acetone and acetonitrile as eluents and five spiked UHQ water volumes 50, , , and mL were also assessed.
The total analysis time was thirty minutes. To identify each pesticide and degradation product, the three most abundant ions were selected by separately injecting each compound and, for quantification, the ion found in the greatest proportion was selected. The different analytic parameters were assessed using samples of UHQ water or uncontaminated natural water spiked with known concentrations of the different compounds.
The matrix effect was evaluated in duplicate by comparing the analyte signal obtained when pre-concentrating mL of UHQ water with that obtained when pre-concentrating mL of river water, both spiked with a concentration of 0. The linearity of the calibration curves was evaluated at a concentration range between 0. Calculations were made using peak areas. The accuracy average recovery was determined by evaluating the recovery percentage for five replicates and precision of the method repeatability and reproducibility was assessed by determining the concentration, on the same day, of five samples of river water mL spiked with 0.
The limits of detection LODs and quantification LOQs were estimated as the analyte concentration with a signal-to-noise-ratio of 3 and 10, respectively.
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Intra-group comparisons were carried out to verify differences in the total concentration of pesticides between the collected samples at the end of summer and during the winter season. The statistical t student was used for this purpose and the p values less than 0. The statistical analyses were performed using R software. It is important to mention that for logistical problems, Las Cabras Canal and Cachapoal River were not sampled at both seasons; therefore the statistical analysis was performed for Tahuilla Canal, Cadena Creek, Zamorano Creek and Claro River.
Each compound was analyzed in scan mode to identify the most abundant ions and retention times. However, it was necessary to modify the temperature ramp in order to achieve good peak resolution and separation. The three most abundant ions of each compound were selected one to quantify and two to confirm by comparing the spectra from the mass library NIST 08 with those obtained when injecting the standards in scan mode.
Finally, three different windows were created as a function of retention times in which the selected ions for the compounds included in each window were determined Table 2. To optimize the SPE method, the recovery percentage of each of the compounds was evaluated by modifying the sorbent type, the solvent used for elution and the sample volume. Results obtained for five different types of sorbent tested are shown in Figure 2 a and 2 b. In all cases, mL of UHQ water are preconcentrated with all compounds at 1. According to these results the Oasis HLB sorbent was selected to evaluate the efficacy of different organic solvents tested and the preconcentrated sample volume.
Another of the studied parameters was pre-concentrated sample volume, for which 50, , , and mL of UHQ water spiked with 0. The results showed that the recovery percentage remains constant when pre-concentrating between 50 and mL of water, and decreases considerably when pre-concentrating a greater sample volume. Considering this variation and the time required to pre-concentrate the various volumes of water, it was decided to work with a volume of water of mL since it allows a greater recovery percentage to be obtained.
To evaluate the matrix effect, the analyte signals were compared in duplicate at a concentration of 0. Therefore, to minimize the matrix effect and avoid a decrease in or overestimation of the pesticide concentration, matrix-matched standards were used.
The LOD fluctuated between 0. The precision of the method repeatability and reproducibility was evaluated by determining the relative standard deviation of the peak area in five water samples fortified with 0. The accuracy of the method was determined by evaluating the recovery percentage by modifying the type of sorbent and elution solvent and the sample volume that passed through the cartridge.
The method was applied to the determination of the studied compounds in different samples of surface water from the Cachapoal River in Central Chile. Of the sixteen studied analytes, atrazine, DET, pyrimethanil, cyprodinil and diazinon were detected in most surface water samples, while fluometuron, acetochlor and CGA were not detected in any of the analyzed samples. At the end of the summer, pyrimethanil and cyprodinil were the analytes detected in the greatest concentrations, while in winter season, simazine and DET presented the highest concentrations Table 4.
Of all of the sampled sites at the end of the summer, Las Cabras Canal presented the greatest level of pesticide contamination and of the samples collected in winter season, Tahuilla Canal presented the greatest total pesticide concentration.
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Finally, statistical analysis using the t student showed significant differences in the total concentration of pesticides for the sampled sites at the end of the summer and winter season Table 5. All samples were analyzed in triplicate. For the statistical analysis, the concentrations lower than limit of quantification were considered as zero. It is important to stress that in this work the monitored irrigation canals are located in the lower part of the basin Figure 1 , draining a large part of the fields located in the Puemo and Las Cabras area.
Water Research , 84 , A new concept for reduction of diffuse contamination by simultaneous application of pesticide and pesticide-degrading microorganisms. Spromberg, David H. Mulholland, Barbara Thuerig, Moses K. Pair your accounts. Oxadiazon and metolachlor were found at a relatively high frequency in the analysed samples but at trace levels. Pesticide levels in groundwater: value and limitations of monitoring.
In addition, the study area presents marked spatio-temporal variations in precipitation levels, with the most intense in the central valley of the basin. Finally, the tributaries of the Cachapoal River present mixed La Cadena Creek and Claro River and pluvial Zamorano Creek hydrological regimes, with highly variable daily streamflows and monthly averages for example, 6.
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Occurrence of herbicides and degradation products derived from triazines in surface water of Cachapoal river basin. However, the concentrations did not surpass the limits of quantification of the method. The degradation products DEA and DET were detected in all of the samples analyzed at the end of summer, although also in concentrations that did not surpass the limits of quantification. Adsorption is the binding of chemicals to soil particles. Soils high in organic matter or clay tend to be most adsorptive and sandy soils low in organic matter tend to be least adsorptive.
Highly volatile chemicals are more likely lost to the atmosphere than to water supplies. However, highly volatile compounds may contaminate water if they are also highly soluble. The proportions of sand, silt and clay in the soil affect the movement of dissolved pesticides through soil. Soils with more clay and organic matter tend to hold water and dissolved chemicals longer. Pesticides have a greater chance of reaching ground water through coarse textured, sandy soil.
Clay soils are more prone to rapid runoff — leading to surface water contamination. Soil Permeability — The measure of how fast water can move downward through a particular soil is called soil permeability.