Environment Pollution and Climate Change
Open Access

Chromatography; Electric Vehicle; Emerging pollutants

Introduction

With advances in agriculture, sustainable means for combating pests that threaten food supply have increasingly been sought [1]. Pesticides are widely used against these food crop pests but their distribution can reach the wider environment in aqueous solution, especially during rainfall. They percolate down through the soil and eventually reach the groundwater [2,3]. Because of the persistence of pesticides in the environment, great mobility, high bioaccumulation and toxicity, they have become a source of pollution at the global level [4,5].

Despite the importance of pesticides for protecting and ensuring good-quality crops, they are of concern regarding human health [6,7]. Their use and the handling practices involved give rise to high levels of exposure and adverse health effects. Exposure of humans to pesticides results in immunosuppression, hormonal interruption, reduced intelligence, reproductive distortion and cancer. The impacts of this exposure can be divided into acute problems, such as the onset of Parkinson’s disease, and chronic problems such as vision reduction, for example [8,9].

As a measure to protect public health, guidance levels for pesticides in drinking water have been implemented by national governments. There are several guidance values, and a few of them are issued by the World Health Organization (WHO) and the United Nations Food and Agriculture Organization (FAO), which establish acceptable levels of pesticide residues.

Currently, in Brazil, there are almost 5,000 pesticides that have been released for use. These contain more than 550 active ingredients that have been authorized by the Ministry of Agriculture for use in formulations on the market, as agricultural pesticides on crops and for plant protection products. Registration of pesticides is regulated through Decree No. 4,074/2002; this is a responsibility shared between the Ministry of Agriculture, Livestock and Supply (MAPA), Ministry of the Environment (MMA) and Ministry of Health.

Because of the risks that these pollutants bring to health and the environment, it is necessary to constantly monitor the presence of pesticides in water, with regard to the toxicity level of each compound. Moreover, to understand the effects of contaminants, it is essential to quantify and monitor concentrations at the emission source, in environmental compartments and in living organisms [10]. In Brazil, the National Water Quality Assessment Program (PNQA, 2022) aims to contribute to sustainable management of water resources and guide the development of policies for the recovery of environmental quality in inland water bodies.

Selection of these compounds for regulation is not easy to evaluate, regarding both identification and quantification. Mass spectrometry (MS), an analytical identification technique for compounds of interest, has been gaining a prominent position for use in organic environmental analyses [11]. An approach consisting of use of gas chromatography with mass spectrometry (GC-MS) combined with solid-phase microextraction (SPME) techniques is mentioned in regulated methods (ISO 27108:2013 and ASTM D 6520:2000). Such an approach is essential in order to undertake sensitive positive structural identification of pesticides and other pollutants in the environment [12].

SPME can be done in two ways: headspace mode (HS-SPME) or through immersion of fibers in liquid samples (direct SPME).When complex arrays are processed, HS-SPME is preferred because interference can clog the extractor that covers the fiber; analytes need to be volatile enough to pass easily into the headspace [13]. In some studies, a limitation of SPME has also been described, relating to the nature of the hydrophobic analytes that are attached to the wall of the sample containers, thereby reducing the accuracy of determinations. In this context, it is believed that on-site SPME sampling is the approach to be used in the future for resolving this problem [14].

According to FAOSTAT (2022), Brazil is considered to be the country with the highest availability of renewable water resources in the world. The São Francisco River, the main river in eastern South America, is classed in Brazil as a water body of great economic, social and ecological importance. With a length of 1,811 miles, it is the fourth largest river system on the continent and the largest river entirely in Brazil. It is an important source of hydroelectric energy, irrigation, water supply, fishing, aquaculture and navigation in the east and northeast of Brazil [15].

However, intensive anthropic use has resulted in impacts on the river. Thus, a need to adopt public policies and means for revitalization of this asset has arisen [16].

The present study was carried out on the lower Sao Francisco River, along the stretch of the river between the downstream side of the Xingó hydroelectric power plant, in the municipality of Piranhas, Alagoas (AL), and the mouth of the river, in the municipalities of Piaçabuçu, AL, and Brejo Grande, Sergipe (SE). For this, a single extraction procedure was established, using SPME combined with use of GCMS, in the selected ion monitoring mode (SIM) and scanning mode (SCAN), with the aim of screening for 31 pesticides in surface waters. The methodology was applied at different sampling stations as part of a wide-ranging water quality monitoring survey, which included sampling downstream from six municipalities in the basin in order to assess the risk caused by pesticides in the Sao Francisco River.

Materials and methods

This study was conducted in the region of the lower Sao Francisco River, corresponding to the area between the municipality of Piranhas and the mouth of the river between the states of Alagoas and Sergipe. This stretch of the river is approximately 240 km long. Samples were collected in November 2021, at strategic points in the river (Table 1, Figure 1).

Table1: Water sample collection points downstream from each municipality.

Figure 1: Geographical location of collection points.

Initially, interviews were conducted among producers and local farmers in the lower Sao Francisco River region during 2020, regarding their main crops and use of agrochemicals and fertilizers. Through this, it was possible to select the main products used in the study area. The pesticide standards, totaling 31 chemical compounds, were acquired from Supelco (USA) in 1 mL ampoules. Table 2 presents some data on the monitored compounds, including: CAS (registered name for the chemical compound in the Chemical American Society database),chemical formula and molecular mass.

Table2: Compounds monitored in the lower San Francisco River.

The compounds were identified using mass spectrum data from the NIST 14 library (NIST/EPA/NIH Mass Spectra Library, version 2.2, USA), linear retention indexes, and data from the literature and pattern injection. Linear retention indexes (LRI) were calculated in accordance with the Van den Dool equation in Kratz (1963), using n-alkane (C7 to C30) standards with purity above 99.5% (Sigma-Aldrich).

SPME procedure using headspace mode combined with GCMS (HS-SPME/GC-MS)

To extract contaminants of interest, which had boiling points less than or equal to 270ºC, solid-phase microextraction in headspace mode at 70ºC was applied. 15 mL vials equipped with a ‘mininert’ valve (Supelco, Bellefonte, PA, USA) were accurately filled up with about 5 mL of the water samples collected.

A divinylbenzene/carboxin/polydimethylsiloxane (DVB/CAR/ PDMS) fiber of film thickness 50/30 μm (Supelco, Bellefonte, PA, USA) was used, housed in a manual support (Supelco, Bellefonte, PA, USA).

A gas chromatograph was used together with an ion-trap mass spectrometer (Shimadzu, GC-MS/QP2010 Plus, Kyoto, Japan). The conditions used were the following: injector temperature, 260ºC; injection mode, without division; capillary column, DB-5, 60 m long, 0.25 mm internal diameter, film thickness 0.25 μm (Agilent J&W); oven temperature, 45ºC maintained for 5 min, then increased to 80ºC at a rate of 10ºC min−1 and to 240ºC at 2ºC min−1; helium gas at a constant pressure of 100 kPa; transfer line temperature, 250°C; and acquisition range, 40-500 m/z.

Validation of the HS-SPME/GC-MS method

Preparation of standard solutions

Standard stock solutions were prepared at an approximate concentration of 1 mg.L-1 in dichloromethane or acetone, according to the solubility of the analyte. From these solutions, a working solution was prepared at a concentration of 10 μg.L-1 with all standards. For the analysis by means of HS-SPME/GC-MS in SIM mode, analytical curves were constructed at concentrations between 0.005 and 10 μg.L-1. The curve values were determined and adjusted using the maximum value allowed according to CONAMA Resolution No. 357 [17], shown in the Table 3.

Table3: Limit values from the Brazilian legislation.

Calibration curve and detection and quantification limits

Linearity was determined in terms of the evolution of the regression curves of volume versus standard concentration and was expressed as the linear coefficient (R2). The limits of detection (LD) and quantification (LQ) were determined based on the standard deviation All the analyses were performed in triplicate, using the SIM mode and using the major and secondary ions. The analyses on the samples did not present peak interferents, which thus conferred selectivity to the method developed.

Results and Discussion

With the calibration curve, the linearity range investigated for six analytes (n = 6) can be seen, along with the linear correlation coefficients, LD, LQ and maximum values, as established by the Ministry of Health through Ordinance no. 518 of 2004. The presence of six compounds (Table 4), with R2 ranging from 0.981 to 0.996, was confirmed. The detection limits for the method remained in the range of 0.005 to 1.0 μg.L-1, and the quantification limits were between 0.001 and 0.003 μg.L-1, i.e. in accordance with the values established by the legislation. The pesticides identified did not have values above (LQ), and therefore were below the permitted concentration, as defined by CONAMA Resolution No. 357 [17].

Table4: Analytical parameters obtained through SPME/GC/MS in SIM mode.

All the analytical monitoring was performed using gas chromatography coupled to mass spectrometry. The chromatographic profile in SIM mode is shown in Figure 2.

Figure 2: Chromatographic profile in SIM Mode of monitored compounds.

Table 5 shows the compounds identified through the SIM mode in the six municipalities studied along the lower São Francisco River.

Table5: Compounds identified using HS-SPME/GC-MS, SIM mode.

Table 6 shows the compounds identified in SCAN mode in the six municipalities along the lower São Francisco River.

Table6: Compounds identified using HS-SPME/GC-MS, SCAN mode.

Using the HS-SPME/GC-MS method, in SIM mode, for the municipality of Piranhas, none of the contaminants studied were detected. However, in SCAN mode, through the calculation referring to the LRI, four compounds with great toxicological potential could be identified: carbendazim, fluoroacetamide, naphthalene and toluene. The fungicide carbendazim is widely used on fruit and vegetable crops in Brazil. The chromatographic profile is shown in Figure 3.

Figure 3: Chromatographic profile of the sample from the municipality of Piranhas.

Table 7 presents the classification applied, along with the toxicological class as defined through the Collegiate Board Resolution, RDC 294 (2019), correlated with the occurrence downstream of the municipalities.

Table7: Occurrence and classification of the pesticides and chemicals identified.

Among the 14 compounds identified, three are classified as of the intersection of the analytical curve(s) and the slope of the line(s). These are presented in Equations 1 and 2, respectively.

extremely toxic (I), six are classified as highly toxic (II) and five are classified as moderately toxic (III).

In the municipality of Pão de Açúcar, the presence of three compounds was identified: lindane, fluoroacetamide and toluene; two of these were highly toxic. In Traipu, four compounds were found: heptachlor epoxide isomer B, lindane, 2,6,10,15-tetramethyl heptadecane and fluoroacetamide; one of these was extremely toxic and two were highly toxic. In São Brás, four compounds were found: heptachlor epoxide isomer B, lindane, 3-trifluoroacetoxy pentadecane and fluoroacetamide; three of these were identical to those found in Traipu. Propriá and Penedo presented the highest diversity of pesticide contaminants: DDT, aldrin, beta-BHC, lindane, y-chlordane, 1,4-dichlorobenzene, fluoroacetamide, oxime methoxy phenyl and toluene. In addition to these, the pollutant 2-ethyl hexanol was also detected in Penedo. Therefore, in Propriá and Penedo, nine and ten pollutants out of the 31 studied were identified, respectively.

It was observed that the compound fluoroacetamide, which is an acute and highly toxic rat poison, was present in all samples collected in the six municipalities. This is a matter of great concern.

This survey aimed to identify the pesticides present in water in municipalities along the lower São Francisco River. The results demonstrated the extent to which this water body is contaminated by agrochemicals. A study by Ferreira et al. (2022) portrayed how pesticide contamination in water not only directly impacts the quality of drinking water in local areas, but also gives rise to indirect damage through transfer between species such as in the food chain and in the soil [18].

Studies have proven that combined or separate exposure to agrotoxins carries risks to human health due to the action of agents such as carcinogens, neurotoxins, toxins and endocrine disruptors [19]. In addition, pesticides may give rise to transient or permanent changes to the immune and hematological systems [20, 21]. Kim et al. (2017) also found in their experiments that exposure to agrochemicals is associated with the incidence of some diseases in the population, such as asthma, Parkinson’s disease and cancer [22].

It is of great importance to detect and identify the pesticides present in rivers and other water bodies so that ways to reduce the adverse effects that these contaminants have on human health and the environment can be found.

Conclusion

The HS-SPME/GC-MS method developed in this study proved to be fundamental for determining the existence of pesticides in the lower San Francisco River, with extreme sensitivity and selectivity. It met the requirements in the range of μg.L-1, even in the presence of organic matter, and at different concentrations. The SIM and SCAN modes applied in pesticide determinations showed good results, even in the presence of organic matter. The detection and quantification limits found were low, but sufficient to detect these substances, at a level lower than that established by the Brazilian legislation. This study has proven to be very important from the point of view of alerting the population and officials responsible for public policy and the environment, and for raising their awareness. In addition, the occurrence of new “unregulated” contaminants requires more constant monitoring. Therefore, this study will provide support for implementation of new policies and specific regulations, which are fundamental for achieving and maintaining the healthy balance of the environment.

Acknowledgements

The following laboratories were involved in developing this study: Separation System and Process Optimization Laboratory (LASSOP), of the Technology Center; Natural Resources Research Laboratory (LPqRN), of the Center for Agrarian Sciences; and Aquaculture and Water Analysis Laboratory (LAQUA), of the Center for Agrarian Sciences.

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