Content area
Pesticides control pests and diseases in crops in order to enhance agricultural productivity; however, they are responsible for damaging aquatic resources. This study aimed to assess pesticide residues in aquatic ecosystems in Burkina Faso. Data were collected in two sampling sites: Bama and Banzon. Thus, in each sampling site, 35 producers were randomly chosen and surveys about pesticide use in the area were performed by distributing questionnaires to each chosen producer in Bama and Banzon. Fifteen (15) water samples were also collected from Bama Pond, Banzon, and the river of Deux Balé. The QuEChERS method was used to evaluate pesticide residue levels in water samples. The results indicated the existence of three classes of pesticides at varying rates: herbicides, insecticides, and fungicides were found to be used by 100%, 100%, and 71.42% of respondents, respectively. Water analysis revealed that the most commonly encountered insecticide was monocrotophos at concentrations of 0.188 µg/l, 0.077 µg/l, and 0.048 µg/l at Banzon, Bama, and Parc of Deux Balé sites, respectively. The highest herbicide level detected in water samples was metazachlor at concentrations of 0.099 µg/l, 0.068 µg/l, and 0.060 µg/l in Parc of Deux Balé, Bama, and Banzon, respectively. The fungicide propiconazole had the highest level detected in water at concentrations of 1.011 µg/l, 0.902 µg/l, and 0.622 µg/l in Bama, Parc of Deux Balé, and Banzon, respectively. These results indicate that the pesticide residue content in water exceeded the maximum residue limit defined by the FAO/WHO Codex Alimentarius.
Introduction
In Burkina Faso, fisheries make a significant contribution to food security and the fight against poverty through the creation of income and better nutrition for rural populations (FAO, 2008). However, this has led to various issues due to the pollution of the reservoirs. According to Arain et al. (2008) and Yeo et al. (2015), the pollution of surface water (rivers, lakes, lagoons, estuaries, etc.) in the region is due to natural processes (hydrological characteristics, rainfall, rock alteration, soil erosion, etc.), climate change, and anthropogenic impacts (urban, industrial, agricultural activities, discharge of untreated wastewater, etc.). These anthropogenic activities often discharge various organic and inorganic pollutants that contribute to the pollution of hydrosystems (Ayah, 2015; Briton et al., 2010). Pesticides such as substituted ureas, triazines, organochlorines, pyrethroids, and organophosphates were reported to be found in aquatic environments (Yao et al., 2018).
Although the use of pesticides has significantly increased agricultural production, their use negatively impacts aquatic biodiversity (Monkiedje et al., 2000). Thus, water runoff from watersheds from agricultural fields can be a source of pesticides that pollute water bodies, resulting in the loss of aquatic organisms, including fish (Bouba, 2002). Pesticides are responsible for agitated swimming, loss of balance, and swallowing behaviors in Oreochromis niloticus (Linnaeus, 1758) (Mallum & Sogbesan, 2016). It also has the potential for proliferation of filamentous cells, cellular infiltration, hemorrhage, and epithelial lifting in the gills, vacuolation of hepatocytes, and necrosis in the liver, as well as exfoliation and swelling of the pyknotic nuclei of the kidney for Clarias gariepinus (Burchell, 1822) (Ayoola & Ajani, 2008). In the long term, it can lead to the disappearance of certain fish species, leading to severe losses in the fishery sector (Yarou et al., 2017).
In Burkina Faso, previous studies have focused on the common names and different types of pesticides used by farmers (Bayili, 2014; Congo, 2013; Son et al., 2017). However, most reservoirs, rivers, and ponds suffer pollution due to the use of pesticides (Congo, 2013; Sere, 2022). Thus, Kou Valley and Banzon Plain are facing challenges such as pollution, loss of biodiversity, degradation of water quality, and overfishing. In fact, the Kou Valley has been exploited since 1970 and the Banzon Plain since 1978 for rice production and fishing (Latevi, 2018). Actually, a severe decrease in many fish species was noticed by fishermen. The loss of some fish species in these areas could be due to the pollution of the aquatic environment. Thus, the main aim of this study is to protect the fishery industry in the hydrological zones (Kou Valley and Banzon Plain) by managing pesticides.
Materials and methods
Description of the study area
The study was conducted at three sampling sites located in the Sudano-Sahelian regions: Kou Valley (Bama), Banzon Plain (Banzon), and the park of Deux Balé (Fig. 1). Kou Valley and Banzon Plain are exposed to agricultural activities, while Deux Balé was used as a control site because there is no agriculture in this site. The climatic zones of the study sites are Sudano-Sahelian and Sudanian (Konaté et al., 2022).
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Fig. 1
Location of the study area
The Kou Valley
Kou Valley is located approximately 30 km northwest of Bobo-Dioulasso on RN 9 (Bobo-Faramana axis). This site is at 1°32′01″ west and 12°21′56″ north. The site covers an area of 1823 km2 and is associated with the Kou River and its tributaries. This occurs in Nasso and Pesso cities. Rice has been the primary crop; however, over time, several crops are produced upstream (bananas, corn, papayas, cabbages, etc.) during the rainy season or as an off-season crop (Wellens et al., 2013). With an initial area of 50 ha, the Bama pond now has currently shrunken to only 3 ha because of technical issues during the establishment of the spillway and the use of its banks for agricultural production (Sanou, 2016; Konaté et al., 2022).
The Banzon Plain
Banzon Plain is located 50 km north of Orodara and 60 km from the western part of Bobo-Dioulasso. It is located at 04°49′ west and 11°19′30″ north. The site covers an area of 585 ha, including 454 ha of exploitable land for irrigated rice cultivation (Latevi, 2018). This area varies depending on the season and ranges from 400 ha during the rainy season to 325 ha during the dry season. It has been in operation since 1978. It was designed mainly for rice production, but other crops, such as corn and bananas, were also introduced (Latevi, 2018). The main water source in Banzon Plain is the Mouhoun River. It flows from south to southeast upstream of Banzon, and a water canal was created to supply the irrigated plain (Latevi, 2018).
The Parc of Deux Balé
The Deux Balé National Park is located in the Boucle du Mouhoun region of Balé province. It is at the meridians 2°45′ and 3°15′ west and parallels 11°25′ and 11°50′ north. It extends over an area of approximately 800 km2 (Birba, 2014). The park contains an important hydrographic network, the main being the perennial Mouhoun River. It is supplied by the Grand Balé and Petit Balé rivers, which have junctions in the forest and a continuous line to Ghana. The site contains at least five ponds and numerous small rivers (Birba, 2014).
Chemicals and reagents
Analytical standard (99% pure) of herbicides, simazine, atrazine, alachlor, pendimethalin, metazachlor, pretilachlor, and PCB n°209 and insecticides carbofuran, methomyl, difluorobenzamide, mevinphos, propoxur, heptenophos, ethoprophos, monocrotophos, dimethoate, lindane, diazinon, heptachlor, aldrin, beta endosulfan, dieldrin, 2,4-DDT, O,p′-DDT, propargite, tetramethrin, bifenthrin, methoxychlor, l-cyhaolothrin, mirex, azinphos-ethyl, permethrin, cyfluthrin, cypermethrin, alpha-cypermethrin, and deltamethrin were obtained from the National Public Health Laboratory at Ouagadougou, Burkina Faso. In addition, the fungicides HCB, beta HCB, quintozene, chlorothalonil, chlorothalonil, triadimefon, penconazole, thiabendazole, imazalil, benalaxyl, propiconazole, azoxystrobin and acaricides chlordimeform, dimethoate with nematicide carbofuran, and ethoprophos were obtained.
Methylene chloride (dichloromethane), n-hexane, acetone, methanol (purity 99.9%, HPLC grade), acetonitril (purity 99.5%), sodium chloride anhydr (purity 99%), magnesium sulfate anhydr (purity 99.5%), and sodium sulfate anhydrous were obtained from Univers Bio-Medical, Burkina Faso.
Identification of the pesticides used in the study area
A simple questionnaire was distributed to rice farmers in the rice farming–based plains in Bama and Banzon to know the types of pesticides used by the farmers. The Deux Balé site was not investigated because no pesticide users reside in the surrounding areas. Fifteen random producers were interviewed at each site. The following information was covered by the questionnaire: age, sex, level of education, field distance to the water body, types and commercial names of agricultural pesticides, and types of cultivated crops. Surveys were performed during periods of high pesticide use between July and August 2022. Both commercial and local names of pesticides claimed the responding producers were asked for. The local names were translated into English commercial names with the help of a native agricultural technician. The common names of these pesticides were identified from the catalog of the Sahelian Pesticides Committee (SPC 2022).
Water sampling
The water samples were collected from the Bama (348,427, 1,260,076; 348,313, 1,260,118 and 348,161, 1,260,135) and Banzon ponds (309,620, 1,257,515; 3,096,630, 1,257,588 and 3,996,647, 1,257,681) and the Deux Balé River (499,503.14, 1,291,541.817; 504,765.446, 1,284,533.472 and 510,271.31, 1,277,200.147). Five samples were taken at each site in the transverse direction. At the two other sites corresponding to running water, samples were collected in the longitudinal direction (upstream to downstream). For the Deux Balé site, water samples were collected at the intersection of the two water bodies in the Deux Balé park. In each sampling zone, 200 ml of water was sampled at a depth of 25 cm, following the methodology of Douny et al. (2021). The samples were collected during the period from September to November 2022. The samples were taken, i.e., by suction pump. Polyvinyl chloride (PVC) containers (750 mL) opened at the top and attached to a 30-cm handle were used for the collection of water samples at the desired depth (Nesser et al., 2016). The collected samples were closed and sealed with plastic and wrapped in aluminum foil to avoid contact with light. Samples bottles were stored in a refrigerator at 4 °C until extracted for pesticide residues at the National Public Health Laboratory at Ouagadougou.
Analysis of pesticide residues
The collected water samples were transported to the laboratory for analysis using the QuEChERS method. This method of pesticide residue extraction is a quick, easy, cheap, effective, rugged, and safe method developed by Anastassiades et al. (2003). This process was followed during the extraction and purification phases. It is a liquid–liquid extraction process. The obtained pesticide residue contents were compared to the threshold values of the maximum residue limit (MRL) defined by the FAO/WHO Codex Alimentarius which was set to 0.1 µg/l for drinking water sample. Thus, water was considered polluted when the residue content was higher than 0.1 µg/l, while it was not polluted when the residue content was less than 0.1 µg/l.
Extraction of pesticides in water samples
The extraction kit was composed of 4 g of magnesium sulfate (MgSO4) or sodium sulfate (NaSO4), 1 g of sodium chloride (NaCl), 1 g of sodium citrate anhydride, and 0.5 g of sodium citrate dibasic sesquihydrate. After weighing, these reagents were placed in 50-ml centrifuge tubes for extraction. The purification kit consisted of 0.9 g of anhydride magnesium sulfate, which was poured into a 50-ml centrifuge tube.
The residues were extracted by adding 10 ml water samples and 10 ml dichloromethane (solvent) to the extraction kit. The mixture was homogenized by vortex mixture for 1 min, then centrifuged at 3000 rpm for 5 min, and allowed to stand to allow the separation of the organic phase from the aqueous phase. The supernatant was collected, and six ml of the supernatants were used for purification. The extracts were added to the purification kits, homogenized by vortex mixture for 1 min, and centrifuged at 3000/rpm for 5 min. The obtained supernatants were collected, conditioned in small bottles, and placed in a nitrogen sulfide evaporator in a water bath for concentrating the extracted pesticide residues at an average temperature of 35 degrees Celsius in 10 min. After complete evaporation, the dry extract was reconstituted in acetonitrile (50 µl of acetonitrile), subject to vortex mixing, and transferred to a vial (1.5 ml) for analysis.
Gas chromatography analysis GC/MS micro-EDC
The extracts were placed in an Agilent GC micro ECD (6890) chromatograph for analysis. The extracts were automatically injected and transported by mobile gas current through the capillary column, according to the method described by Anastassiades et al. (2003). A total of forty-nine (49) common names were identified based on the following categories in Table 1.
Table 1. List of common names considered in the analysis
Family | common names |
|---|---|
Herbicides | Simazine, Atrazine, Alachlor, Pendimethalin, Metazachlor, Pretilachlor and PCB n°209 |
Insecticides | Carbofuran, Methomyl, Difluorobenzamide, Mevinphos, Propoxur, Heptenophos, ethoprophos, Monocrotophos, Dimethoate, Lindane, Diazinon, Heptachlor, Aldrin, Beta Endosulfan, Dieldrin, 2,4 DDT, Op 'DDT, Propargite, Tetramethrin, Bifenthrin, Methoxychlor, l-Cyhaolothrin, Mirex, Azinphos-Ethyl, Permethrin, Cyfluthrin, Cypermethrin, Alpha-Cypermethrin, Deltamethrin |
Fungicides | HCB, Beta HCB, Quintozene, Chlorothalonil, Chlorothalonil, Triadimefon, Penconazole, Thiabendazole, Imazalil, Benalaxyl, Propiconazole, Azoxystrobin |
Acaricides | Chlordimeform, Dimethoate |
Nematicides | Carbofuran, ethoprophos |
Gas chromatography Hewlett Packard Model 6890 coupled with mass spectrometry and equipped with a Ni63 electron capture detector (ECD) and an HB-5 MS capillary column 30 m in length × 0.32 mm internal diameter (i.d.) was used to identify the residues of pesticides in the water samples. The stationary phase was composed of an inner coating of 0.25-̫µm film of 5% polymethyl siloxane. The capillary column was equipped with a capillary column (n°TR-820232 at a maximum temperature of 325 °C, length of 30 mm, diameter of 0.25 mm, and film of 0.25 µm. During the analysis, the temperature was set at 70 °C for 5 min and then increased to 310 °C for another 5 min. The temperature reached 120 °C (20 °C/min), then 200 °C (10 °C/min), and finally 310 °C (5 °C/min). The analysis time for each sample was set at 42.5 min. Nitrogen was used as the carrier gas at a flow rate of 4 ml min−1. The pesticide molecules were detected using an electron capture detector (ECD).
Calculation of pesticide content in samples
The pesticide content of the samples was calculated based on the following formula:
With T: Content of pesticides in water samples (µg/ml). Subsequently, content values were converted into µg/l for comparison with international standards.
Rc: Chromatographic result (µg/ml).
Vr: Volume recovered from acetonitrile (ml).
Vs: Volume of solvent (ml).
Data analysis
The relative frequencies of each response were calculated for each parameter included in the questionnaire such as the educational level of the respondents, the distance from fields to water body, the types of pesticides used, the cultivated crops, and the mortality of fish species. In addition, pesticide residues were recorded in tables for comparison with the maximum residue limits set by the FAO/WHO Codex Alimentarius. Analysis of average, range, median, samples tested positive %, and violative samples % exceeding MRLs was carried out using Microsoft Excel (version 2016) (Douny et al., 2021; Nesser et al., 2016).
Results
Survey results
Age and sex of respondents
The age of respondents ranged from 18 to over 65 years in both sites. The age of most of the respondents in both sites ranges from 35 to 65 years with a frequency of 49 and 69%, in Banzon and Bama, respectively (Table 2), followed by age groups 18 to 35 and 65 and over. Most respondents in both sites were men (85%) with women representing 15% of the respondents (Table 2).
Table 2. Classification of respondents based on age (years) and sex
Study sites | ||
|---|---|---|
Banzon | Bama | |
Age (%) | ||
18-35 | 34 | 20 |
35-65 | 49 | 69 |
65 and over | 17 | 11 |
Sex (%) | ||
Male | 85 | 85 |
Female | 15 | 15 |
Educational level of respondents
Figure 2 shows the educational levels of respondents. At both sites, the majority of respondents were not sent to school representing 49% and 51% in Banzon and Bama, respectively. On the other hand, respondents with secondary education, representing the most educated group, stood at 9 and 11% in Bama and Banzon, respectively. The other groups included those who had attended primary and Koranic schools.
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Fig. 2
Educational level of respondents
Distance from fields to water bodies
The distance-separating fields from the water bodies are shown in Fig. 3. The results showed that 34% of the fields in Bama and 26% in Banzon were established less than 100 m from water bodies. The most distant fields were located more than 1000 m away from water bodies, representing 17% of the sites. The remaining fields were found to be at distances ranging from 100 to 1000 m, corresponding to 49% and 57% of the claims reported by the respondents from Bama and Banzon, respectively.
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Fig. 3
Distance separating fields from water bodies
Types of pesticides used by respondents
The types of pesticides used by producers are illustrated in Fig. 4. All surveyed farmers used herbicides and insecticides at both sites. Results showed that fungicides were used by 66% of producers in Bama and 77% in Banzon.
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Fig. 4
Class of pesticides used by producers in Bama and Banzon
Types of pesticides claimed to be used by respondents
Table 3 lists the trade and common names claimed to be used by respondents. The corresponding common names were obtained using the catalog of the Sahelian Pesticides Committee. In total, 21 trade names containing 12 common names were identified (Table 3). These pesticides can be classified into three categories: herbicides, insecticides, and fungicides depending on the target species. Glyphosate and 2,4-D have been identified as herbicides and insecticides. The most commonly used herbicides are Gramoxone and Samory, with frequencies of 89% and 37% in Banzon and 71% and 31% in Bama, respectively. The most commonly used insecticides in Bama were Lambda, Mega super, and Decis at frequencies of 57%, 46%, and 20%, respectively. At Banzon, Lambda, Red caїman, and Decis represent the insecticides mainly used, with frequencies of 71%, 31%, and 17%, respectively. Concerning fungicides, Red caїmans are used by 15% of producers in Bama and 31% in Banzon. Red caїman is a mixture of insecticides and fungicides.
Table 3. List of the commercial and common names claimed to be used by respondents in Bama and Banzon
Class of pesticides | Mixtures | Trade name | common names | Frequency (%) | |
|---|---|---|---|---|---|
Bama | Banzon | ||||
samory | Bensulfuron-methyl (100g/l) | 31 | 37 | ||
gramoxone | Paraquat | 71 | 89 | ||
glyphader | Glyphosate (360g/l) | 20 | 11 | ||
glycel | Glyphosate (410g/l) | 3 | 6 | ||
nicomais | Nicosulfuron (40g/l) | 0 | 6 | ||
ladaba | Glyphosate (360g/l) | 14 | 6 | ||
thera | Bensulfuron-methyl (100g/l) | 0 | 6 | ||
roundup | Glyphosate (360g/l) | 3 | 3 | ||
Herbicides | glypho more | Glyphosate (360g/l) | 6 | 0 | |
ruby | Bispyribac-sodium (100g/l) | 0 | 6 | ||
topstar | Oxadiarargy | 6 | 0 | ||
douma woro | Glyphosate (480g/l) | 3 | 9 | ||
herbetra | 2,4-D (720g/l) | 17 | 11 | ||
Insecticides | lambda | Lambda-cyhalothrin (25g/l) | 57 | 71 | |
profenofos (200g/l) | |||||
mega super | Nicosulfuron (60g/l) | 46 | 11 | ||
bin'fla RMG | Glyphosate (360g/l) or (720g/l) | 6 | 3 | ||
decis | Deltamethrin (25g/l) or (100g/l) | 20 | 17 | ||
tope extra | 2,4-D(720g/l) | 3 | 9 | ||
emapyr | Emamectin benzoate (24g/l) or Pyriproxyphene (60g/l) | 9 | 0 | ||
emacot | Emanectin benzoate (19g/l) | 11 | 3 | ||
Insecticides and Fungicides | red caїman | Endosulfan (25%) or Thiram (25%) | 15 | 31 | |
Types of cultivated crops grown in the study area
All the surveyed producers were engaged in rice farming in the established plains of Bama and Banzon (Fig. 5). It is followed by market gardening of bananas and other crops. In Bama, around 9% and 6% of producers are involved in market gardening and banana growth, respectively. In Banzon, only 3% of respondents practiced market gardening. Other crops, such as sweet potatoes and corn, are grown by 49% and 29% of producers in Bama and Banzon, respectively.
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Fig. 5
Types of cultivated crops in the Bama and Banzon plains
Pesticide residues found in water
Residues of insecticides in water samples
The insecticide residues found in water bodies are shown in Table 4. The most frequent residues were monocrotophos, 2,4-DDT, diazinon, and propargite found at 0.188 µg/l, 0.077 µg/l, and 0.048 µg/l in Banzon, Bama, and Deux Balé, respectively. The concentrations of this monocrotophos and propargite (at the Banzon fishing site) exceeded the maximum residue limit (MRL) at both fishing sites (Bama et Banzon). The concentrations of DDT were 0.048, 0.042, and 0.039 µg/l in Deux Balé, Banzon, and Bama, respectively. For diazinon, the concentrations were 0.044 µg/l, 0.033 µg/l, and 0.020 µg/l in Bama, Banzon, and Deux Balé, respectively. Propargite was found only in Bama at a concentration of 0.358 µg/l which exceeded the MRL. Residues of other compounds were found at low concentrations (≤ 0.1 µg/l). The residues of 3 common names (13% of common names) have their content higher than at maximum residue limit.
Table 4. Concentration of insecticides (µg/l) of detected in the three sites
Common names | Sample analyzed | Bama | Banzon | Deux Balé | Mean | Median | Range | Detected frenquency % |
|---|---|---|---|---|---|---|---|---|
Mevinphos | 15 | 0.006 | 0.003 | 0.001 | 0.003 | 0.0031 | 0.001-0.006 | 67 |
Heptenophos | 0.001 | 0.005 | 0.001 | 0.002 | 0.0012 | 0.001-0.008 | 100 | |
Monocrotophos | 0.077 | 0.188* | 0.048 | 0.104 | 0.045 | 0.077-0.2 | 100 | |
Lindane | 0.004 | 0.009 | 0.001 | 0.005 | 0.006 | 0.001-0.009 | 100 | |
Diazinon | 0.044 | 0.033 | 0.02 | 0.032 | 0.033 | 0.004-0.05 | 100 | |
Heptachlor | 0.001 | 0.002 | 0.002 | 0.002 | 0.002 | 0.001-0.003 | 80 | |
Aldrin | 0.004 | 0.002 | 0.002 | 0.003 | 0.003 | 0.001-0045 | 60 | |
Dieldrin | 0.017 | 0.014 | ND | 0.010 | 0.012 | ND-0.021 | 53 | |
Propargite | 0.359* | ND | ND | 0.120 | 0.02 | ND-0.56 | 33 | |
Tetramethrin | 0.003 | 0.004 | 0.001 | 0.003 | 0.001 | 0.001-0.004 | 60 | |
l-Cyhaolothrin | 0.008 | 0.007 | 0.016 | 0.010 | 0.009 | 0.003-0.009 | 80 | |
Azinphos-Ethyl | 0.003 | 0.003 | 0.001 | 0.002 | 0.002 | 0.001-004 | 100 | |
Cyfluthrin | 0.008 | ND | ND | 0.003 | 0.002 | ND-0.012 | 33 | |
Op 'DDT | 0.009 | 0.018 | 0.002 | 0.010 | 0.01 | 0.003-0.2 | 100 | |
2.4 DDT | 0.039 | 0.042 | 0.048 | 0.043 | 0.045 | 0.01-0.05 | 100 |
* Maximum Residue Limit
Residues of herbicide in water bodies
Table 5 shows the herbicide residue at the three study sites. The common names with the highest concentrations were metazachlor which was detected at 0.099 µg/l, 0.068 µg/l, and 0.060 µg/l in Deux Balé, Bama, and Banzon, respectively, followed by pendimethalin at 0.062 µg/l, 0.059 µg/l, and 0.013 µg/l in Deux Balé, Bama, and Banzon, respectively. Pretilachlor and alachlor were found only in Bama at concentrations of 0.040 µg/l and 0.034 µg/l. The residue concentration of each detected common name is below the maximum residue limit.
Table 5. Concentration (µg/l) of herbicides in the three sites
Common names | Sample analyzed | Bama | Banzon | Deux Balé | Mean | Median | Range | Detected frenquency % |
|---|---|---|---|---|---|---|---|---|
Simazine | 15 | 0.0127 | 0.02 | 0.017 | 0.0166 | 0.0166 | 0.0010-0.018 | 100 |
Atrazine | 0.0121 | 0.016 | 0.013 | 0.0137 | 0.0130 | 0.0121-0.017 | 100 | |
Alachlor | 0.0341 | 0.01 | 0.011 | 0.0184 | 0.012 | 0.01-0.035 | 100 | |
Pendimethalin | 0.0595 | 0.014 | 0.063 | 0.0455 | 0.031 | 0.014-0.595 | 100 | |
Metazachlor | 0.0681 | 0.06 | 0.099 | 0.0757 | 0.067 | 0.04-0.08 | 100 | |
Pretilachlor | 0.0407 | 0.007 | 0.008 | 0.0186 | 0.008 | 0.007-0510 | 100 |
Residues of fungicide in water bodies
Residues of fungicides at the three sites are presented in Table 6. The most important common names detected are propiconazole, penconazole, thiabendazole, imazalil, and triadimefon. Propiconazole was found at concentrations of 1.011 µg/l, 0.902 µg/l, and 0.622 µg/l in Bama, Deux Balé, and Banzon, respectively. The penconazole concentrations were 0.272, 0.146, and 0.111 µg/l in Deux Balé, Bama, and Banzon, respectively. The concentrations of thiabendazole were 0.190, 0.157, and 0.124 µg/l in Banzon, Bama, and Deux Balé, respectively. The concentrations of imazalil were 0.146 µg/l, 0.113 µg/l, and 0.081 µg/l in Bama, Banzon, and Deux Balé, respectively. The results showed that the concentrations of all fungicides exceeded the MRL. Triadimefon values were 0.055 µg/l, 0.024 µg/l, and 0.016 µg/l in Bama, Deux Balé, and Banzon, respectively. The residues of four common names (40% of common names) have their content higher than at maximum residue limit.
Table 6. Concentration (µg/l) of common names from fungicide in the three sites
common names | Sample analyzed | Bama | Banzon | Deux Balé | Mean | Median | Range | Detected frenquency % |
|---|---|---|---|---|---|---|---|---|
HCB | 15 | 0.004 | 0.005 | ND | 0.003 | 0.003 | ND-0.006 | 60 |
Beta HCB | 0.013 | 0.006 | 0.008 | 0.009 | 0.007 | 0.005-0.014 | 100 | |
Quintozene | 0.003 | 0.002 | 0.004 | 0.003 | 0.0025 | 0.001-0.006 | 100 | |
Chlorothalonil | 0.003 | 0.001 | 0.003 | 0.002 | 0.002 | 0.001-0.005 | 100 | |
Triadimefon | 0.056 | 0.016 | 0.025 | 0.032 | 0.032 | 0.0160-0.057 | 100 | |
Propiconazole | 1.011* | 0.622* | 0.902* | 0.508 | 0.6723 | 0.900-1.2 | 100 | |
Penconazole | 0.146* | 0.111* | 0.272* | 0.128 | 0.13 | 0.1O1-0.229 | 100 | |
Thiabendazole | 0.158* | 0.191* | 0.124* | 0.105 | 0.125 | 0.104-0.201 | 100 | |
Imazalil | 0.146* | 0.114* | 0.081* | 0.065 | 0.065 | 0.050-0.156 | 100 | |
Benalaxyl | ND | 0.002 | ND | 0.001 | 0.002 | ND-0.003 | 33 |
HCB Hexachlorobenzene
*Maximum residue limit
Discussion
During the survey, male producers were found to be more represented than female producers. This could be explained by the fact that men are more involved than women in agricultural production in irrigated areas. Additionally, men may be responsible for pesticide spraying. The ages of most respondents ranged between 35 and 65 years because this group represents the heads of households. Respondents who did not attend school accounted for > 50% of the population. This result reflects the low number of operators in irrigated areas. Regarding this low educational level, the risk of environmental contamination is very high. The results from this study correlate with those obtained by Congo (2013) in the vegetable production zone of Loumbila. In addition, this study identified different types of insecticides, herbicides, and fungicides used by producers Bama and Banzon. These results corroborate those of Congo (2013) in the production zone of the Loumbila dam. All surveyed producers used insecticides and herbicides, whereas fungicides were used only by 33% of the stakeholders. This study showed seven trade names of herbicides, eight insecticides, and one fungicide which were claimed to be used by the responding farmers. The list claimed to be used by the respondents includes insecticides: Lambda, Mega super, Bin’fla RMG, Decis, Red caїman, Tope extra, Émapyr, and Emacot; herbicides: Amory, Gramoxone, Glyphader, Glycel, Nicomaïs, Ladaba, Thera, Roundup, Glypho plus, Rubis, Topstar, Doumaworo, and Herbetra; and fungicide: Red caїman. Most of these pesticides were also reported to be used around the Loumbila Dam (Congo, 2013) and were listed by the Sahelian Pesticides Committee (SPC, 2022).
However, laboratory analysis of the water samples detected the presence of 16 common names of insecticides, six herbicides, and nine fungicides. The existence of these molecules in water bodies was not in line with the results of the surveys. This difference could be explained by the fact that the laboratory needed to have all the standards for detecting all chemical molecules used in the area. as is the case with paraquat. Therefore, this may indicate the underestimation of chemicals during analysis. The use of these pesticides in market gardening is linked to the availability and lower cost of these products (Congo, 2013). In fact, the majority of farmers did not abide by recommended disposal procedures or the recommended dose according to Abdelbagi et al. (2022). In addition, Mohamed et al. (2018) claim that growers misuse pesticides in the fields endangering the environment. So, the irrational use of pesticides and poor storage management may result in contamination of the surrounding environment including soil, water sources, and crops (Abdelbagi et al., 2022). At the Bama and Banzon sites, these values could be explained by the use of pesticides by producers around these water bodies. In Deux Balé, these values seem abnormal because no activities related to vegetable production were practiced at this site. Therefore, the presence of pesticide residues at this control site could be explained by the effect of runoff from upstream water polluted by agricultural chemicals. This indicates that the persistence time of these pesticides is very long, to the extent that their concentrations are similar at the contaminated sites. According to Nesser et al. (2016), pesticides are well-known as universal contaminants of aquatic environments and are characterized by their long environmental persistence and bioaccumulation along the food chain. Generally, the levels of insecticides varied from 0.001 to 1.011 µg/l, herbicides from 0.007 to 0.099 µg/l, and fungicides from 0.002 to 0.272 µg/l. These results can be explained by the proximity of the fields, non-compliance with recommended dosages (Toé et al., 2013), and insufficient educational level of farmers. Most fields were established at a distance of less than 500 m from the fishing site, and 30% were located less than 100 m. These results are close to those of Adechian et al. (2015), who found that 46% of producers’ fields were located at a distance of less than 500 m from the water source. This closeness to water bodies could be explained by the search for fertile soil, insufficient financing for elevating the water, and, above all, negligence by the agricultural and environmental supervision and control services responsible for bank protection and regulations.
In terms of pollution, the results revealed that the level of eight herbicides was lower than the maximum residue limit (MRL) defined by the European Union (EU), which was set to 0.1 µg/l for these compounds (UE, 1998; Zabeirou et al., 2020). Only three of the 16 common names of insecticides (monocrotophos, propiconazole, and propargite) were above the MRL depending on the site. Among the eight fungicides, penconazole, thiabendazole, and imazalil had higher contents than the FAO/WHO Codex Alimentarius MRL at all three sites. For compounds whose contents were lower than the MRL, it could be said that water bodies were less exposed and, therefore, were less risky for aquatic organisms, particularly fish. In contrast, six compounds, including monocrotophos, propiconazole, propargite, penconazole, thiabendazole, and imazalil, were detected at levels exceeding MRL. Therefore, they can pose a risk to aquatic organisms, including fish. Vroumsia et al. (2014) reported that pesticides can lead to slow opercular movements, loss of balance, increased surface activity, loss of pigmentation, increased aggressiveness, and erratic swimming in fish. This is the case for pendimethalin, which, according to Abd-algadir et al. (2011), may cause long-term risks to animal and human health (reproduction and growth) because it has a very high persistence in tissues. The compounds of certain fungicides can inhibit fish reproduction, according to Şişman and Türkez (2010). In addition, this can lead to health issues related to the heart, liver, and neuroendocrine disruptions (Boileau et al., 2015).
Conclusion
The pesticides used by farmers around water bodies were classified into three categories. These include insecticides such as propiconazole, monocrotophos, 2,4-DDT, diazinon, and propargite; herbicides such as metazachlor, pretilachlor, and alachlor; and fungicides such as penconazole, imazalil, and triadimefon. The concentrations of some insecticides and fungicides exceeded the MRL established by FAO/WHO Codex Alimentarius. Therefore, the results revealed strong contamination of water bodies by certain common names of pesticide. Heavy pollution can lead to fish mortality and, consequently, a reduction in fish stocks at fishing sites. Better pesticide management is necessary for the better management of aquatic resources. Therefore, more advanced research on pesticide residue concentrations in aquatic resources, such as fish, is essential for the sustainable management of fishery resources.
Author contribution
SF, CI, and S. Salam are the initiators of the study. They elaborated the study project, collected the data, and wrote the article. KS and S. Saydou analyzed the samples in the laboratory with SF, CI, and S. Salam. All authors reviewed the manuscript.
Funding
No funding was received for conducting this study.
Data availability
Datasets generated and/or analyzed during the current study are available from the corresponding author on reasonable request.
Declarations
Ethical approval
All authors have critically reviewed and approved the manuscript.
Consent to participate
Fieldwork consisted of water sampling and farmer surveys. No biological material was used in this study.
Conflict of interest
The authors declare no competing interests.
Publisher's note
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
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