Ecosystems are subject to various stress factors, such as temperature rises due to climate changes and metal disposal. Thermal stress can amplify or mask the effects of metals on aquatic organisms. ...This study aims to carry out a systematic review on the effects of temperature rises due to climate changes on the toxicity of metals for freshwater organisms. Searches were made in different electronic databases and article selection was based on the following inclusion criteria: concordance with the question of a systematic review; publication in English, Spanish, and Portuguese between 1960 and 2020; and the use of standard methodology. Forty-three articles were included, which were classified with respect to the year and country of publication, test-organisms and metals studied, temperatures tested, and the effects observed. In 80% of the studies analyzed, a temperature rise was responsible for increasing the toxicity of metals for the aquatic organisms. The temperatures studied contemplated the temperature rise predicted by the Intergovernmental Panel for Climate Change at the end of the 21st century. Brazil stood out among the countries for having the greatest number of research studies in this area, although there is still the need for an increase in studies in tropical climate regions. Based on the literature review, it was shown that the metals most studied were copper and cadmium and the test-organisms most used in the research projects were fish. The information obtained from ecotoxicological studies is essential to predict the effects and prevent the risks associated with the metal contamination of aquatic ecosystems due to climate changes.
Aquatic systems are seldom disturbed by a single stressor agent. Considering that nutrients and metals occur simultaneously in the environment, studies on the combined effects of these elements on ...the biota need to be carried out. The aim of this study was to evaluate the effect of the microalga
Raphidocelis subcapitata
exposed to different combinations of phosphorus (P) and zinc (Zn) on the neotropical cladoceran
Ceriodaphnia silvestrii
. The algae acclimated to P concentrations of 2.3 × 10
−4
and 2.3 × 10
−6
mol L
−1
were exposed to concentrations of 0.10, 0.57, 1.13, and 2.27 × 10
−6
mol Zn
2+
L
−1
. The P acclimated algal cells showed different capacity to deal with external free Zn level, resulting in higher susceptibility to metal as P decreased in the test medium. Elevated cell metal values were observed in
R. subcapitata
acclimated to 2 × 10
−6
mol P L
−1
and exposed to Zn, as compared to the values found in the microalga exposed to 2 × 10
−4
mol P L
−1
. A significant reduction in number of newborn produced by cladoceran was verified when the organism was fed alga containing 47 × 10
−15
g Zn cell
−1
(2 neonates per female) and 60 × 10
−15
g Zn cell
−1
(5 neonates per female). It was observed a decrease of 90% of
C. silvestrii
survival for the treatment with 47 × 10
−15
and 60 × 10
−15
g Zn cell
−1
. Algal cells acclimated to high and low concentrations of P were an important exposure route to Zn for
C. silvestrii.
The aim of this study was to evaluate the effect of phosphorus (P) on the toxicity of zinc (Zn) for the alga Raphidocelis subcapitata. P was provided in three concentrations: 2.3 x 10-4 mol L-1, 2.3 ...x 10-6 mol L-1 and 1.0 x 10-6 mol L-1. Algal cells were acclimated to the specific P concentrations before the start of the experiment. The chemical equilibrium software MINEQL+ 4.61 was employed to calculate the Zn2+ concentration. After acclimated, the algal cells were inoculated into media containing different Zn concentrations (0.09 x 10-6 mol L-1 to 9.08 x 10-6 mol L-1). The study showed that besides the reduction in algal growth rates, phosphorus had an important influence on the toxicity of zinc for microalga. The inhibitory Zn2+ concentration values for R. subcapitata were 2.74 x 10-6 mol L-1, 0.58 x 10-6 mol L-1 and 0.24 x 10-6 mol L-1 for the microalgae acclimated at P concentrations of 2.3 x 10-4 mol L-1, 2.3 x 10-6 mol L-1 and 1.0 x 10-6 mol L-1, respectively. Ecotoxicological studies should consider the interaction between metal concentrations and varying P values to provide realistic data of what occurs in phytoplankton communities in environments.
In Brazil, the process of surface water potabilization for public supply generates sludge, but information on this waste is scarce, and its disposal in landfills and waterways, without prior ...treatment, generates pollution. This experimental study evaluated the incorporation of aluminum and ferric sludge, commonly generated in Brazil, into different soils for road pavement infrastructure. Sludge generated in two water treatment plants in the state of São Paulo was characterized regarding risks to human health and the environment and individually incorporated into clayey sand soil and sandy soil in proportions of 25 and 50%. Evaluation of the mechanical tests of the soil sludge mixtures and their suitability for road construction found that i) all percentages of aluminum and ferric sludge incorporated into clayey sand soils and sandy soil met the mechanical standards for use in embankment; ii) aluminum sludge incorporated into sandy soils proved to be suitable for use in pavement subbase; iii) the percentual incorporation is higher than previous research; iv) the use of sludge as a partial replacement for virgin soil makes road construction cleaner. Analyses of variance on the mechanical properties of the soil-sludge mixtures showed that soil type is the only factor influencing this variable. Only the interaction of water treatment sludge (WTS) type with the other factors is significant for the CBR and Swell data.
•In Brazil, WTS can be used in road pavement as embankment and subbase.•The factors influencing the mechanical properties were evaluated using ANOVA.•WTP produces different sludge according to the coagulant and quality of the treated water.•The sludge contains high concentrations of iron, aluminum, and manganese.•Sludge can substitute for natural material in road construction until 50%.
Introduction:
Water treatment deficit and poor health, hygiene and sanitation infrastructure can contribute to disease transmission by dissemination of contaminants and microorganisms. As an ...alternative, carbon-based materials coated with antimicrobial molecules have been proposed for water treatment, but few supporting data are available so far. Hence, this study investigates the potential use of PAN-based activated carbon fibers (ACF) decorated with silver nanoparticles in water treatment.
Methods:
Silver nanoparticles were incorporated into the material using a cheap and electroless method. Field emission scanning electron microscopy (FEGSEM), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) characterized the whole material. The textile was mounted on a water filter prototype and had its capacity to remove bacterial (Escherichia coli) and fungal (
Candida albicans
,
Aspergillus niger
and
Penicillium funiculosum
) cells evaluated. Composition and toxicity of the filtered water were determined.
Results:
Water filtered by Ag@ACF for 2 and 24 h contained 0.254 mg/L and 0.964 mg/L Ag, respectively. Ag@ACF filtering successfully removed
E. coli
,
C. albicans
, and
A. niger
from the suspensions, but not
P. funiculosum
. Treated water was non-toxic for Vero cells and Drosophila melanogaster, but toxic for Raphidocelis subcapitata. Ag@ACF showed efficient microbial elimination when applied in water treatment. Silver nanoparticles released in aqueous medium may be responsible for
R. subcapitata
toxicity. Future studies should be conducted to reduce silver nanoparticles release from the carbon fiber.
Among the waste produced daily by communities are those resulting from the treatment of water for public supply, with local specificities that reflect the characteristics and uses of the land. ...Despite the continuous generation and inadequate disposal still current in Brazil, there is little information on these residues. The data related to the composition of these sludges are essential for the study of alternatives for beneficial uses and for determining the risks to the environment and human health from inadequate disposal. It is in this context that the present study was developed, with the objective of identifying the physical-chemical characteristics of sludge produced in water treatment plants (WTPs) and of verifying the presence of these elements in the waters of the source used for supply. Such research was carried out through a case study in two WTPs in the state of São Paulo that perform surface abstraction. Therefore, in each of the WTPs, samples of densified sludge, representative of the dry and rainy periods, were characterized. The chemical findings of the sludge have been compared to the historical series of a decade of monitoring of the water quality of the sources of these WTPs. Among the main results, concentrations above the reference limits for the inert residues of aluminum, iron, manganese and barium in sludge are highlighted, as well as the existence of iron and manganese in the raw water collected and the variations in the concentrations of iron, sodium and manganese in the sludge due to the climatic conditions.
The toxicity of cadmium and chromium to Pseudokirchneriella subcapitata and Microcystis aeruginosa was evaluated through algal growth rate during 96h exposure bioassays. Free metal ion concentrations ...were obtained using MINEQL super(+) 4.61 and used for IC50 determination. Metal accumulations by the microorganisms were determined and they were found to be dependent on the concentration of Cd super(2+) and Cr super(6+). IC50 for P. subcapitata were 0.60 mu mol L super(-1) free Cd super(2+) and 20 mu mol L super(-1) free Cr super(6+), while the IC50 values for M. aeruginosa were 0.01 mu mol L super(-1) Cd super(2+) and 11.07 mu mol L super(-1) Cr super(6+) times P. subcapitata accumulated higher metal concentrations (0.001 -0.05 mu mol Cd mg super(-1) dry wt. and 0.001 -0.04 mu mol Cr mg super(-1) dry wt) than the cyanobacteria (0.001 -0.01 mu mol Cd mg super(-1) dry wt and 0.001 -0.02 mu mol Cr mg super(-1) dry wt). Cadmium was more toxic than chromium to both the microorganisms.
The toxic potential of four disinfectant agents (chlorine, ozone, peracetic acid and UV radiation), used in the disinfection of urban wastewater, was evaluated with respect to four aquatic organisms. ...Disinfection assays were carried out with wastewater from the city of Araraquara (São Paulo State, Brazil), and subsequently, toxicity bioassays were applied in order to verify possible adverse effects to the cladocerans (Ceriodaphnia silvestrii and Daphnia similis), midge larvae Chironomus xanthus and fish (Danio rerio). Under the experimental conditions tested, all the disinfectants were capable of producing harmful effects on the test organisms, except for C. xanthus. The toxicity of the effluent to C. silvestrii was observed to increase significantly as a result of disinfection using 2.5 mg L⁻¹ chlorine and 29.9 mg L⁻¹ ozone. Ozonation and chlorination significantly affected the survival of D. similis and D. rerio, causing mortality of 60 to 100 % in comparison to the non-disinfected effluent. In experiments with effluent treated with peracetic acid (PAA) and UV radiation, a statistically significant decrease in survival was only detected for D. rerio. This investigation suggested that the study of the ideal concentrations of disinfectants is a research need for ecologically safe options for the treatment of wastewater.
Sludge from water treatment plants (WTP) is a waste of continuous and increasing generation, with a polluting potential associated with the composition of water source and the inputs used in the ...potabilization process. Currently, most of these residues are released in natura into aquatic systems, which motivates research related to the beneficial use of the material, especially incorporations with soils in geotechnical works. This study evaluated the toxicity of WTP sludge leachate and its combinations with soils from the State of São Paulo (Brazil) using cladoceran
Daphnia similis
, a standardized test species in tropical aquatic environments. For that, acute toxicity tests were carried out with
D. similis
testing leachate from twelve different compositions of aluminum and iron sludge and sandy soils and clayey sand. The concentrations of Fe and Al (dissolved) and Ba, Mn and Cl (total) present in the leachate from these samples were determined. Among the main results, it is highlighted that all the raw leachates samples caused 100% immobility for
D. similis
, and the toxicity of the samples varied according to the chemical elements detected and the type of soil used.
Metal pollution of aquatic ecosystems continues to be a worldwide concern, and many studies have previously been conducted evaluating metal toxicity to aquatic organisms. However, these studies have ...mainly been focused on temperate species and only evaluated aqueous exposure, whereas aquatic organisms under real-world conditions are also exposed to metals through their diet. Toxicity tests were conducted evaluating the effects of Cr on cell density and biochemical composition of the microalga
Chlorella vulgaris
. Additionally, the toxic effects of Cr on the temperate
Ceriodaphnia dubia
and the tropical
Ceriodaphnia silvestrii
cladocerans were investigated through three contamination routes: contaminated medium (CM), contaminated food (CF;
C. vulgaris
), and the combination of both situations (CMF; contaminated medium and food). The toxicity tests with the cladocerans evaluated the metal effects on survival, number of newborns, and feeding activity. Exposure to 48 µg L
−1
total dissolved Cr reduced cell density and increased protein, carbohydrate, and lipid content in
C. vulgaris
. The increase in the biochemical composition and hence food quality of the microalgae after Cr exposure have contributed to the absence of toxic effects to the cladocerans in the CF treatment. No toxic effects were observed to the temperate cladoceran at any treatment. The tropical cladoceran
C. silvestrii
showed reduced filtration, ingestion and reproduction rates in the CM and CMF treatments at a Cr concentration below national and international standards. Implications for considering different exposure pathways in ecotoxicological studies, (tropical) risk assessments and indications for future research are discussed.
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