Spatiotemporal evaluation of organochlorine pesticide residues in bottom sediments of the Rio de Ondas hydrographic basin, western Bahia, Brazil

The Rio de Ondas Hydrographic Basin (ROHB), Bahia state, Brazil, is located in a region with abundant water resources and is highly impacted by intense agricultural activity. In such a scenario, the use of organochlorine pesticides can represent a potential risk to the aquatic environments, due to their persistence, high bioaccumulation capacity, and high toxicity. Thus, organochlorine pesticide residues in bottom sediment samples from rivers on eighteen sites distributed along the ROHB in the dry and rainy periods were analyzed by gas chromatography coupled with mass spectrometry. The validated method showed no matrix effect, recoveries ranging from 82% (β-HCB) to 118% (DDD), limits of detection between 0.003 ng g^-1 (α-HCH) and 0.011 ng g^-1 (DDT), limits of quantification of 0.010 ng g^-1 (α-HCH) to 0.036 ng g^-1 (DDT), repeatability with the highest relative standard deviation of 0.97% (α-hexachlorocyclohexane at 2.000 ng g^-1), and inter-day precision ranging from 10% (aldrin at 0.050 ng g^-1 and 0.600 ng g^-1 and α-endosulfan at 0.600 ng g^-1) to 25% (β-endosulfan at 0.050 ng g^-1). Although most compounds were banned since 1985, it was observed that their residues were widely distributed in the ROHB, with the total concentrations varying from 3.242 ng g^-1 (P02) to 12.052 ng g^-1 (P17) and from 0.313 ng g^-1 (P14) to 30.861 ng g^-1 (P13) in the dry and rainy periods, respectively, which may be related to historical contamination and/or prohibited use. Moreover, the spatiotemporal variation showed the highest concentrations of organochlorine pesticide residues in the rainy season, coinciding with the planting period.

Inland expansion of COVID-19 in Western Bahia: epidemiological profile and spatial analysis of deaths and confirmed cases

This article aims to describe the epidemiological profile and the spatial distribution of deaths and confirmed cases of COVID-19 in the health macroregion of Western Bahia. An ecological study on the inland expansion of SARS-CoV-2 was performed from March 21, 2020 to March 31, 2021 considering incidence and mortality rate, case fatality rate, case density and moving average of cases and deaths. 37,036 cases and 536 confirmed deaths were registered. Of all cases, 94.5% recovered and 4.0% remained active. The incidence rate was 3884.1/100,000 inhabitants, the mortality rate 56.2/100,000 inhabitants and the fatality rate was 1.4% A predominance of very high and high intensity of the occurrence of COVID-19 in the macroregion was identified and moving average revealed an increasing trend. Findings show a high risk of infection and death in the macroregion, in addition to a growing trend in accumulated cases, confirming the inland expansion of the disease.

Distribution of organochlorine, organophosphates, carbamate, thiocarbamate, pyrethroids, and strobilurins in surface sediments of the Rio de Ondas watershed by GC-MS

The determination of some pesticides in surface sediments can provide important information about their distribution in the water column. This work aimed to determine the distribution of the classes of pesticides along the Ondas River's hydrographic basin (ORHB), in eighteen different points, during the dry and rainy periods. The pesticides were extracted from the sediment samples by solid-liquid extraction and then analyzed using a gas chromatograph coupled to mass spectrometry. After the development and validation of the method, nineteen pesticides from the group of organochlorine, organophosphates, carbamate and thiocarbamate, pyrethroids, and strobilurins were quantified in at least one point in the two collection periods, with accuracy varying between 86 and 126%. The average concentrations were 0.020 ng g^-1 (carbofuran) to 249.123 ng g^-1 (dimethoate) and 0.029 ng g^-1 (carbofuran and sulfotep) to 533.522 ng g^-1 in the dry and rainy periods, respectively. The results showed a wide distribution of pesticide residues in the ORHB, with higher levels for dimethoate, phenitrothion, and malathion, which may be related to their agricultural use in the region. In Brazil, it does not have specific legislation for maximum permitted values of pesticides in sediment, allowing for inappropriate or prohibited use and, consequently, affecting water quality.