Efficacy of an in situ algaecide treatment can be predicted prior to an application by physically modeling exposures and responses with laboratory experiments. A sodium carbonate peroxyhydrate (SCP) algaecide was used in a drinking water reservoir (Hartwell Lake, Anderson, SC) to control a benthic algal assemblage putatively producing 2-methylisoboreol (MIB) and geosmin, compounds with adverse taste and odor attributes. These SCP applications provided an opportunity to test hypotheses regarding potential convergence of laboratory and in situ exposures and responses. Objectives of this study were to (1) measure responses of a benthic algal assemblage from Hartwell Lake to 7-day laboratory exposures of SCP [measured as hydrogen peroxide (H₂O₂) concentrations], (2) to measure the exposure of SCP (as H₂O₂) applied in a cove of Hartwell Lake and consequent responses of the algal assemblage, and (3) compare exposures and responses measured in the laboratory and in situ. Results demonstrated that in laboratory exposures, H₂O₂ released by SCP dissipated within 48 h. Significant responses of the algal assemblage in terms of phycocyanin concentrations and cell densities were measured 4 days after treatment (4-DAT) and 7-DAT following exposures of 453, 615, and 812 mg H₂O₂ m⁻². The H₂O₂ exposure measured in situ was comparable to effective laboratory exposures in terms of initial exposure (619 ± 428 mg H₂O₂ m⁻²) and exposure duration (dissipation within 30 h), but the in situ exposure had a large deviation initially (i.e., ±428 mg H₂O₂ m⁻²) and was an order of magnitude less than the targeted initial exposure. Therefore, comparison of measured responses was critical to infer comparable exposures and confirm accuracy of the laboratory model. Significant in situ responses were measured 4-DAT and 7-DAT in terms of phycocyanin concentrations and cell densities, and were comparable to responses obtained from effective laboratory exposures (i.e., 453, 615, and 812 mg H₂O₂ m⁻²). Decreases in measured concentrations of MIB and geosmin at the intake of the drinking water treatment facility provided additional evidence that algae were sufficiently exposed to H₂O₂ from SCP. Results of this experiment provide evidence for the design and use of physical laboratory models to predict responses of algae in the field.

Sugarcane is one of the world’s most important commodities. In order to control weeds in the plantations and increase productivity, the mixing of different herbicides during spraying operations is commonplace. This practice is unregulated, and the impact on water quality and nontarget tropical species is poorly understood. In the present work, exposure and recovery assays were used to evaluate antioxidant enzyme activity and histopathological alterations in the liver of tilapia (Oreochromis niloticus) following exposure to mixtures of the herbicides widely used in sugarcane crops: ametryn (AMT), tebuthiuron (TBUT), diuron (DIU), and hexazinone (HZN). The greatest biochemical changes were observed for the mixture (DIU+HZN)+AMT+TBUT at the highest concentration tested (1/10 96hLC50). This mixture caused a significant increase (p < 0.01) of approximately 82% in GST activity after 14 days of exposure. For three of the mixtures evaluated, GST and CAT could be considered potential biochemical biomarkers of exposure to the herbicide mixtures due to the frequency, intensity, and statistical significance of alterations in the assimilation phase. Although morphological changes were evident in the hepatic tissue, severe damage was only noted in a few samples, and there were no statistically significant differences, relative to the control. The results of hepatic lesion recovery assays suggested that the most sensitive individuals affected by the xenobiotics were unable to achieve full recovery. It is anticipated that the data obtained may assist in the selection of biomarkers for monitoring purposes, as well as in reinforcing standards of conduct in the use of agrochemical mixtures in agriculture.

Benzalkonium chloride (BAC) loaded to montmorillonites (Mt) or organomontmorillonites (OMt) generates a functional material that can be incorporated to several systems (polymers, paints, etc) as a controlled release bactericide. Understanding the BAC adsorption sites on these adsorbents is of high importance to clarify their adsorption/desorption characteristics in aqueous media or other solvents. In this work, a thorough study about the adsorption/desorption properties of Mt and OMt with regards to BAC is presented, in order to evaluate further BAC release with the consequent aquatic environment contamination. In this work, the BAC adsorption on two different sites is demonstrated: the interlayer space and the external surface. Depending on BAC concentration in water, sorption of BAC at Mt occurred in two steps. At adsorbed amount <0.5 mmol g⁻¹, there was an Mt interlayer expansion of 0.49 nm with no change of the external charge. At adsorbed amount >0.5 mmol g⁻¹, there was a new interlayer expansion attaining 0.75 nm and the external charge shifted to positive value. In the case of OMt, the introduction of BAC produced changes in the interlayer structure and in the external surface charge. BAC desorption was strongly dependent on the type of Mt or OMt and extraction solvent, knowledge of which will allow its safe use in environmental friendly technological applications.

This study investigated the use of ceramic membranes to remove total suspended solids (TSS), organics (expressed by chemical oxygen demand, COD), and bisphenol A (BPA) via microfiltration (MF, pore size 0.45 μm) and ultrafiltration (UF, cutoff 150 kDa) in post-treatment of effluents from aerobic granular sludge reactors (GSBRs). The efficiency of removal of COD, BPA, and TSS in MF was similar to that in UF; however, it was achieved at a lower pressure, which reduces energy consumption during the filtration process. Despite the similar quality of the permeates in MF and UF, the permeate flux averaged almost 20% higher in UF than in MF. The rejection coefficients were 77–82% for COD and 48–100% for BPA. In both MF and UF, TSS were totally removed. In the integrated system of aerobic granular sludge reactor and membrane installation, total removal of COD was 92–95% and that of BPA was above 98%, independently of the membrane technique. The high efficiency of BPA removal in MF and UF, despite pore sizes in the MF and UF membranes larger than the BPA molecules, suggests that some part of the BPA was first bound by particulate organic matter in the biologically treated wastewater before this sorbed form was removed by the membranes. Furthermore, the high removal of COD and BPA, even in MF, was attributed to adsorption on the membranes, in addition to sieve retention.

Biochar presents great promise as a technology that makes a substantial contribution in various fields of environmental research. However, existing knowledge is still uneven and limited in terms of its effective utilization and field application. In this review, a comprehensive discussionof biochar technology is presentedwith respect to three main aspects:(1) biochar stability; (2) application in soil for conditioning, remediation, and GHG reduction; and (3) biochar sustainability and its environmental impacts. Biochar is a highly stable and slow-mineralizing product; therefore, its application promotes agricultural productivity by providingan efficient nutrient balance and soil fertility, and by restricting the loss of nutrients due to its surface sorption capacity. Moreover, it contributes significantly to the reduction of greenhouse gas emissions from the soil through carbon sequestration. The high adsorption capacity of biochar aids in removing contaminants from soil, thus assisting in the restoration of contaminated sites.Nevertheless, biochar poses certain negative impacts to the environment as well. A few studies have reported that biochar could release organic and inorganic contaminants such as phenol, PAHs, POPs, dioxins, furans, and heavy metals into the soil, altering the soil productivity and soil biota. In certain circumstances, biochar is also responsible for emission of CO₂ from soil due to the priming effect. However, the effect of biochar in soil varies widely depending upon ecological conditions, the pyrolysis process, and the feedstock materials. Overall, this review aims to help in evaluating and addressing the mechanistic understanding of biochar functions in the environment and encouraging awareness of the need forfuture research to counteract its negative environmental consequences.

Biochar amendment can alter soil properties, for instance, the ability to adsorb and degrade different chemicals. However, ageing of the biochar, due to processes occurring in the soil over time, can influence such biochar-mediated effects. This study examined how biochar affected adsorption and degradation of two herbicides, glyphosate (N-(phosphonomethyl)-glycine) and diuron (3-(3,4-dichlorophenyl)-1,1-dimethylurea) in soil and how these effects were modulated by ageing of the biochar. One sandy and one clayey soil that had been freshly amended with a wood-based biochar (0, 1, 10, 20 and 30% w/w) were studied. An ageing experiment, in which the soil-biochar mixtures were aged for 3.5 months in the laboratory, was also performed. Adsorption and degradation were studied in these soil and soil-biochar mixtures, and compared to results from a soil historically enriched with charcoal. Biochar amendment increased the pH in both soils and increased the water-holding capacity of the sandy soil. Adsorption of diuron was enhanced by biochar amendment in both soils, while glyphosate adsorption was decreased in the sandy soil. Ageing of soil-biochar mixtures decreased adsorption of both herbicides in comparison with freshly biochar-amended soil. Herbicide degradation rates were not consistently affected by biochar amendment or ageing in any of the soils. However, glyphosate half-lives correlated with the Freundlich Kf values in the clayey soil, indicating that degradation was limited by availability there.

The purpose of the study was to determine the role of land use, seasonality, and hydrometeorological conditions on the relationship between stream water potassium (K⁺) concentration and discharge during different types of floods—short- and long-duration rainfall floods as well as snowmelt floods on frozen and thawed soils. The research was conducted in small catchments (agricultural, woodland, mixed-use) in the Carpathian Foothills (Poland). In the woodland catchment, lower K⁺ concentrations were noted for each given specific runoff value for summer rainfall floods versus snowmelt floods (seasonal effect). In the agricultural and mixed-use catchments, the opposite was true due to their greater ability to flush K⁺ out of the soil in the summer. In the stream draining woodland catchment, higher K⁺ concentrations occurred during the rising limb than during the falling limb of the hydrograph (clockwise hysteresis) for all flood types, except for snowmelt floods with the ground not frozen. In the agricultural catchment, clockwise hystereses were produced for short- and long-duration rainfall floods caused by high-intensity, high-volume rainfall, while anticlockwise hystereses were produced for short- and long-duration rainfall floods caused by low-intensity, low-volume rainfall as well as during snowmelt floods with the soil frozen and not frozen. In the mixed-use catchment, the hysteresis direction was also affected by different lag times for water reaching stream channels from areas with different land use. K⁺ hystereses for the woodland catchment were more narrow than those for the agricultural and mixed-use catchments due to a smaller pool of K⁺ in the woodland catchment. In all streams, the widest hystereses were produced for rainfall floods preceded by a long period without rainfall.

The process for extracting sugarcane juice (Saccharum officinarum) represents the point of greatest contamination in sugarcane mills. Sodium dithiocarbamate also known as metam-sodium or MS is added to inhibit the growth of microorganisms especially Leuconostoc mesenteroides which is responsible for forming polysaccharides. Metam-sodium, upon decomposition, produces highly toxic byproducts. According to literature, under acidic conditions, MS is hydrolyzed resulting in methylamine (MA), CH₃NH₂, and carbon disulfide (CS₂), and in dilute alkaline solutions, MS produces an oxidation reaction characterized by the formation of elemental sulfur (S) and methyl isothiocyanate (MITC). In this paper, it was studied how MS decomposes to MITC and/or MA considering the effects of the matrix (methanol and water); of temperature (4 and 25 °C); of processing time (0, 1, 2, 3, 4 days); and of pH (4.0, 4.5, 7.0). A second experimental design considering the effects of the matrix (water and sugarcane juice); of temperature (4, 25, 35, 45 °C); of processing time (30, 300 min); and of pH (4.0, 4.5, 7.0) was derived from the results obtained considering MITC and/or MA formation. According to the statistical analysis of these results (p < 0.05), the order of the influential factors was as follows: time > matrix > pH > temperature. Results also indicated that the water matrix at pH = 4.5 and 45 °C had the lowest degradation rate (k), with a value of 8.82 day⁻¹, while for the sugarcane juice matrix at the same pH and temperature conditions was larger, with a k value of 30.07 day⁻¹. These results show that the matrix is also important for the degradation of dithiocarbamate to MITC and to MA.

Chemical inputs from agricultural activities represent a threat to aquatic biota and its biochemical systems. Among these systems, acid phosphatases are involved in autophagic digestive processes, decomposing organic phosphates, signaling pathways, and other metabolic routes. In vitro tests are helpful to generate hypotheses about pollutant mechanisms of action through comparison of the toxicity effects of these compounds. In this work, we investigated the inhibitory effects of four organic pesticides and three metals on the acid phosphatases extracted from the freshwater microcrustacean Daphnia similis and the fish Metynnis argenteus. Our results demonstrated that only the metals have considerable inhibitory effects (50% or higher) on the enzyme activities. The calculated median effect concentrations (IC50) for the enzyme inhibition were 0.139 mM Hg²⁺ (fish enzyme), 0.652 mM Cu²⁺ (fish enzyme), and 1.974 mM Al³⁺ (Daphnia enzyme). Due to the relatively low value of the inhibition parameter for Hg²⁺, its inhibitory property could be used as a tool for Hg²⁺ detection in environmental samples. The enzyme activities obtained in the presence of the inhibitors are potential data as in vivo biomarkers for metals in both aquatic species.

Distribution of ten taste and odor (T&O) compounds were investigated in 135 finished water samples from 43 drinking water treatment plants (DWTPs). 2-Methylisoborneol (MIB), geosmin, and 2,4,6-trichloroanisole (2,4,6-TCA) were detected in 53.4, 41.5, and 14.1% of the samples, respectively. The corresponding concentrations were in the range of 18.0–53.1 ng L⁻¹ for MIB, 4.2–6.4 ng L⁻¹ for geosmin, and 0.5–6.6 ng L⁻¹ for 2,4,6-TCA. The other seven T&O compounds, β-ionone, 2,3,6-trichloroanisole (2,3,6-TCA), 2,3,4-trichloroanisole (2,3,4-TCA), 2,4,6-tribromoanisole (2,4,6-TBA), 2-isobutyl-3-methoxypyrazine (IBMP), 2-isopropyl-3-methoxypyrazine (IPMP), and trans-2,cis-6-nonadienal (NDE) were never found in all samples. The results from finished water of DWTPs compared with associated reservoirs indicated that 2,4,6-TCA was formed in the water treatment processes. To determine the chemical formation of 2,4,6-TCA by chlorination, the concentrations of different chloroanisoles in anisole-containing water at pH 5.5–9.0 and 25 °C were measured. The results from chlorination showed that only 2-chloroanisole (2-CA), 4-chloroanisole (4-CA), and 2,4-dichloroanisole (2,4-DCA) could be detected. Their formation rates were all below 3.3% at each pH value, but the reaction was more active at pH 5.5 because of acid catalyzed effect. Accordingly, the chemical formation of 2,4,6-TCA by chlorination was not confirmed in this study, which suggested that the formation of 2,4,6-TCA was related to the methylation of 2,4,6-trichlorophenol with fungi. These findings increase our understanding on the formation of 2,4,6-TCA and provide insights into managing and controlling T&O problems in drinking water.