Research on water quality is a fundamental step in supporting the maintenance of environmental and human health. The elements involved in water quality analysis are multidimensional, because numerous characteristics can be measured simultaneously. This multidimensional character encourages researchers to statistically examine the data generated through multivariate statistical analysis (MSA). The objective of this review was to explore the research on water quality through MSA between the years 2001 and 2020, present in the Web of Science (WoS) database. Annual results, WoS subject categories, conventional journals, most cited publications, keywords, water sample types analyzed, country or territory where the study was conducted and most used multivariate statistical analyses were topics covered. The results demonstrate a considerable increase in research using MSA in water quality studies in the last twenty years, especially in developing countries. River, groundwater and lake were the most studied water sample types. In descending order, principal component analysis (PCA), hierarchical cluster analysis (HCA), factor analysis (FA) and discriminant analysis (DA) were the most used techniques. This review presents relevant information for researchers in choosing the most appropriate methods to analyze water quality data.

Silver nanoparticles (AgNPs) are used intensively in medical and industrial applications. Environmental concerns have arisen from the potential release of this material into aquatic ecosystems. The aims of this research were to evaluate the potential accumulation of silver in the whole body of organisms and analyze the effects of AgNPs on the survival and reproduction of the snail Biomphalaria glabrata. Results show slow acute toxicity with a 10-day LC₅₀ of 18.57 mg/L and an effective decrease in the eggs and egg clutches per organism exposed to tested concentrations. Based on these data, the No Observed Effect Concentration (NOEC) observed was <1 mg/L for snail reproduction. For silver accumulation, we observed that uptake was faster than elimination, which was very slow and still incomplete 35 days after the end of the experiment. However, the observed accumulation was not connected with a concentration/response relationship, since the amount of silver was not equivalent to a higher reproductive effect. The data observed show that AgNPs are toxic to B. glabrata, and suggest that the snail has internal mechanisms to combat the presence of Ag in its body, ensuring survival and reduced reproduction and showing that the species seems to be a potential indicator for Ag presence in contaminated aquatic ecosystems.

This study aimed to analyze the ecotoxicity of nitrogen-, phosphorus-, and potassium-based compounds to organisms of two different trophic levels in order to compare the toxic effect between high-purity substances and these substances as components of fertilizers. Dilutions were made with the fertilizers’ potassium chloride, potassium nitrate, superphosphate, urea, and their equivalent reagents, to conduct assays to establish the acute lethal concentration for half of the population (LC50). Ten individuals of the benthic snail Biomphalaria glabrata and the fish Danio rerio were exposed to each concentration of tested compounds. As a result, the toxicity levels of potassium chloride, potassium nitrate, and urea were obtained for B. glabrata and D. rerio, with the fish being more susceptible to potassium chloride in the fertilizer and the snail to potassium nitrate and urea, in both commercial and reagent forms. Regarding superphosphate, no significant toxicity was found. This study concluded that among the tested substances, KNO₃ and KCl were the most toxic substances and urea the least toxic. It was not possible to establish the most sensitive species since, for KCl, the fish were more susceptible to the fertilizer and the snail to the reagent, while for KNO₃ the opposite was observed.

The use of pesticides in agriculture can leave residues in the treated crops. Pesticides are also potential contaminants of ground and surface water, as reported in many countries. The development of efficient analytical methods to quantify pesticides in water samples is a challenge due to the low levels present. The objective of this work was to develop and validate a method for pesticide analysis in water using sample lyophilization followed by UHPLC–MS/MS and to determine pesticide levels in samples from a Brazilian hydrographic basin. In total, 77 compounds were included, of which 28 were considered only qualitatively. The method was applied to analyze 142 water samples collected during the dry and rainy seasons of 2021–2022, of which 90 were surface and 52 were groundwater samples. In total, 19 compounds were detected in the samples (≥LOD), mainly atrazine (72.5%), atrazine-2-hydroxy (50%), fipronil (18.3%), and pirimiphos-methyl (15.5%). Most compounds (17) were detected during the rainy season regardless of the environmental compartment. Twenty-five samples had quantified levels of the compounds (≥LOQ), of which 80% were collected during the dry season, and 58.3% were groundwater samples (up to 1.045 µg L⁻¹ of 2,4-D in an artesian well). The highest concentrations found in surface water were of atrazine-2-hydroxy (0.171 and 0.179 µg L⁻¹), levels that represent a potential risk to aquatic organisms (risk quotient of 1.1). This work provides an analytical method for determining pesticides in water that can be applied to other environmental pollutants. Although the levels found in the samples complied with Brazilian legislation, constant monitoring should be conducted in the region to guarantee safe levels of the pesticide in water.

The Brazilian savanna (Cerrado Biome) is one of the most important regions in the world in terms of food production, with the use of fertilizers based on nitrogen, phosphorus and potassium (NPK). When not applied properly, fertilizers can alter and affect water quality. The objective of this study was to evaluate the presence of these compounds in surface and groundwater in the Upper Jardim River Hydrographic Unit, Federal District, thus characterizing seasonal variations during the dry and rainy seasons in two periods. A total of 207 groundwater samples and 23 surface water samples were collected in the years 2014, 2015, 2019 and 2020. The parameters analyzed were pH and nitrate, nitrite, ammonium, phosphate and potassium ions. In groundwater samples, pH values were significantly higher and ion levels lower in samples collected during the early years (except for nitrate), and the ammonium concentrations were lower in the dry season than the rainy (in 2014 and 2019). In surface samples, total phosphorus levels were significantly higher in the rainy/2019 compared to the rainy/2020 season, while this tendency was inverted for potassium during the dry season. The use of NPK-based fertilizers has increased considerably in recent years in the region due to the expansion of the agricultural area, and although the results of the study show that concentrations in water are much lower than the maximum values allowed by Brazilian legislation, continuous monitoring is necessary to guarantee water quality.