Linking multivariate statistical methods and water quality indices to evaluate the natural and anthropogenic geochemical processes controlling the water quality of a tropical watershed.

The improvement of water management requires monitoring techniques that accurately evaluate water quality status and detect the effects of land use changes on water chemistry. This study aimed to evaluate how multivariate statistical methods and water quality indices can be applied together to evaluate the processes controlling water chemical composition and the overall water quality status of a tropical watershed. Thirty-four water samples were collected in the Formoso River basin, located on the border of the Amazon Forest. Water parameters were measured in situ using a multiparameter and in the lab using spectroscopic and volumetric techniques. The water quality dataset was interpreted through principal component analysis, multivariate linear regression, and water quality indices. Statistical methods allowed us to identify the sources and geochemical processes controlling water quality chemistry, which were carbonate dissolution, runoff/erosion, nutrient input due to anthropogenic activities, and redox reactions in flooded zones. They were also used to create linear functions to evaluate the effects of land use changes on the geochemical processes controlling water chemistry. Conversely, the water quality indices provide information about the overall condition of the water. The Weight-Arithmetic Quality Index correctly evaluates water suitability for its multiple uses, according to the Brazilian guidelines. Conversely, the Ontario Water Quality Index is not suitable to evaluate the water quality of tropical rivers, since the usual higher water temperature and the low oxygen contents associated with tropical environments result in biased water quality evaluations by this index.

Guidelines for reducing the environmental impact of general anaesthesia.

OBJECTIVE: To provide guidelines for reducing the environmental impact of general anaesthesia. DESIGN: A committee of ten experts from SFAR and SF2H and SFPC learned societies was set up. A policy of declaration of competing interests was applied and observed throughout the guideline-writing process. Likewise, it did not benefit from any funding from a company marketing a health product (drug or medical device). The committee followed the GRADE® method (Grading of Recommendations Assessment, Development and Evaluation) to assess the quality of the evidence on which the recommendations were based. METHODS: We aimed to formulate recommendations according to the GRADE® methodology for three different fields: anaesthesia vapours and gases; intravenous drugs; medical devices and the working environment. Each question was formulated according to the PICO format (Population, Intervention, Comparator, Outcome). The literature review and recommendations were formulated according to the GRADE® methodology. RESULTS: The experts' work on the synthesis and application of the GRADE® method led to the formulation of 17 recommendations. Since the GRADE® method could not be entirely applied to all of the questions, some of the recommendations were formulated as expert opinions. CONCLUSION: Based on strong agreement between experts, we produced 17 recommendations designed to guide reducing the environmental impact of general anaesthesia.

Copper and lead isotope records from an electroplating activity in sediments and biota from Sepetiba Bay (southeastern Brazil).

An old electroplating plant in Sepetiba Bay discharged metal-enriched wastes into the surrounding mangroves for 30 years (from the 1960s to 1990s), resulting in a hotspot zone of legacy sediments highly concentrated in toxic trace metals. This study applies Cu and Pb isotope systems to investigate the contributions of past punctual sources relative to emerging modern diffuse sources. The electroplating activity imprinted particular isotopic signatures (average δ65CuSRM-976: 0.4 ‰ and 206Pb/207Pb: 1.14) distinct from the natural baseline and urban fluvial sediments. The isotopic compositions of tidal flat sediments show intermediate isotope compositions reflecting the mixing of Cu and Pb from the hotspot zone and terrigenous materials carried by rivers. Oyster isotope fingerprints match legacy sediments, attesting that anthropogenic Cu and Pb are bioavailable to the biota. These findings confirm the interest in combining two or more metal isotope systems to discriminate between modern and past metal source emissions in coastal environments.

Exploring a new approach for assessing the fate and behavior of the tailings released by the Brumadinho dam collapse (Minas Gerais, Brazil).

In 2019, the Brumadinho dam rupture released a massive amount of iron ore mining tailings into the Paraopeba River. Up to now, it remains a public health issue for the local and downstream populations. The present study aims to assess the behavior and fate of metal contamination following the disaster. Using new sampling strategies and up-to-date geochemistry tools, we show that the dissolved metal concentrations (< 0.22 µm cutoff filtration) remained low in the Paraopeba River. Although the tailings present high metal concentrations (Fe, Mn, Cd, and As), the high local background contents of metals and other previous anthropogenic contamination hamper tracing the sediment source based only on the geochemical signature. The Pb isotopic composition coupled with the metals enrichment factor of sediments and Suspended Particulate Matter (SPM) constitutes accurate proxies that trace the fate and dispersion of tailing particles downstream of the dam collapse. This approach shows that 1) The influence of the released tailing was restricted to the Paraopeba River and the Retiro Baixo reservoir, located upstream of the São Francisco River; 2) The tailings' contribution to particulate load ranged from 17 % to 88 % in the Paraopeba River; 3) Other regional anthropogenic activities also contribute to water and sediment contamination of the Paraopeba river.

High efficiency of magnetite nanoparticles for the arsenic removal from an aqueous solution and natural water taken from Tambo River in Peru.

Water is an essential compound on earth and necessary for life. The presence of highly toxic contaminants such as arsenic and others, in many cases, represents one of the biggest problems facing the earth´s population. Treatment of contaminated water with magnetite (Fe3O4) nanoparticles (NPs) can play a crucial role in arsenic removal. In this report, we demonstrate arsenic removal from an aqueous solution and natural water taken from the Peruvian river (Tambo River in Arequipa, Peru) using magnetite NPs synthesized by the coprecipitation method. XRD data analysis of Fe3O4 NPs revealed the formation of the cubic-spinel phase of magnetite with an average crystallite size of ~ 13 nm, which is found in good agreement with the physical size assessed from TEM image analysis. Magnetic results evidence that our NPs show a superparamagnetic-like behavior with a thermal relaxation of magnetic moments mediated by strong particle-particle interactions. FTIR absorption band shows the interactions between arsenate anions and Fe-O and Fe-OH groups through a complex mechanism. The experimental results showed that arsenic adsorption is fast during the first 10 min; while the equilibrium is reached within 60 min, providing an arsenic removal efficiency of ~ 97%. Adsorption kinetics is well modeled using the pseudo-second-order kinetic equation, suggesting that the adsorption process is related to the chemisorption model. According to Langmuir's model, the maximum arsenic adsorption capacity of 81.04 mg·g- 1 at pH = 2.5 was estimated, which describes the adsorption process as being monolayer, However, our results suggest that multilayer adsorption can be produced after monolayer saturation in agreement with the Freundlich model. This finding was corroborated by the Sips model, which showed a good correlation to the experimental data. Tests using natural water taken from Tambo River indicate a significant reduction of arsenic concentration from 356 µg L- 1 to 7.38 µg L- 1, the latter is below the limit imposed by World Health Organization (10 µg L- 1), suggesting that magnetite NPs show great potential for the arsenic removal.

Mercury distribution in water masses of the South Atlantic Ocean (24°S to 20°S), Brazilian Exclusive Economic Zone.

Mercury (Hg) is a toxic globally spread pollutant that has been found at increasing concentrations in the South Atlantic Ocean. The present work provides the first insight into the total mercury (HgT, unfiltered waters) content in the water of the Brazilian Exclusive Economic Zone (BEEZ), within a 24°S to 20°S. Water samples were collected from surface to 3400 m depth along transects, and analyzed with atomic fluorescence. The mean HgT concentration for the Tropical Water mass (TW) was 6.3 ± 1.4 pM (n = 16), for the South Atlantic Central Water (SACW), 5.9 ± 0.7 pM (n = 8), for the Antarctic Intermediate Water (AAIW), 5.0 ± 0.6 pM (n = 2), for the Upper Circumpolar Deep Water (UCDW), 6.5 pM (n = 1), and for the North Atlantic Deep Water (NADW), 5.7 ± 0.9 pM (n = 12). HgT concentrations were highest throughout the BEEZ in comparison with other parts of the Atlantic Ocean, farther from the coast.

New insights into metal(loid) dynamics in the Doce River estuary (Brazil) after a massive iron ore-processing tailing dam collapse.

The present study investigated metal and metalloid dynamics in the estuarine water of the Doce River (Brazil) after the collapse of an iron ore-processing tailing dam in 2015. Spectroscopic and isotopic techniques were applied to bring new insights into the effects of the dam failure on the dynamics and hazardousness of particulate and dissolved metal(loid) concentrations along the fluvial-estuarine continuum. Spectroscopic analysis showed that the suspended particulate matter (SPM) of the Doce River estuary consisted of a combination of soil-delivered particles and fine tailing mud particles with small amounts of coarse tailing mud Fe oxides (~150-µm width). Enrichment and contamination factors showed that the dam failure increased particulate Fe, Pb, Cd, and As, and dissolved Pb concentrations. Total concentrations of As (15 µg/L), Pb (30 µg/L), Cd (8 µg/L), and Cr (105 µg/L) increased up to values higher than quality and regulatory guidelines. Human health risk assessment showed that local communities are exposed to a potentially chronic Cr noncarcinogenic effects, although Cr high concentrations were not linked with the dam failure by this study. The particulate Pb isotope signatures reported herein (206/207Pb ratios of 1.214 ± 0.006 and 208/206Pb ratios of 2.025 ± 0.011) can be applied to constrain metal(loid) sources in the Doce River sediment plume and continental shelf. The river-ocean mixing zone caused abrupt changes metal(loid) partitioning (Zn, Pb, Cr, Cu, Cd, and As), controlling their fate in the estuary and the Brazilian southeast coastal.

Trace metal dynamics in an industrialized Brazilian river: A combined application of Zn isotopes, geochemical partitioning, and multivariate statistics.

The Paraiba do Sul (PSR) and Guandu Rivers (GR) water diversion system (120 km long) is located in the main industrial pole of Brazil and supplies drinking water for 9.4 million people in the metropolitan region of Rio de Janeiro. This study aims to discern the trace metals dynamics in this complex aquatic system. We used a combined approach of geochemical tools such as geochemical partitioning, Zn isotopes signatures, and multivariate statistics. Zinc and Pb concentrations in Suspended Particulate Matter (SPM) and sediments were considerably higher in some sites. The sediment partition of As, Cr, and Cu revealed the residual fraction (F4) as the main fraction for these elements, indicating low mobility. Zinc and Pb were mostly associated with the exchangeable/carbonate (F1) and the reducible (F2) fractions, respectively, implying a higher susceptibility of these elements to being released from sediments. Zinc isotopic compositions of sediments and SPM fell in a binary mixing source process between lithogenic (δ66/64ZnJMC ≈ + 0.30‰) and anthropogenic (δ66/64ZnJMC ≈ + 0.15‰) end members. The lighter δ66/64ZnJMC values accompanied by high Zn concentrations in exchangeable/carbonate fraction (ZnF1) enable the tracking of Zn anthropogenic sources in the studied rivers. Overall, the results indicated that Hg, Pb, and Zn had a dominant anthropogenic origin linked to the industrial activities, while As, Cr, and Cu were mainly associated with lithogenic sources. This work demonstrates how integrating geochemical tools is valuable for assessing geochemical processes and mixing source effects in anthropized river watersheds.

Behavior of metallurgical zinc contamination in coastal environments: A survey of Zn from electroplating wastes and partitioning in sediments.

The contamination of coastal environments by metallurgical wastes involves multiple biogeochemical processes; accordingly, understanding metal behavior and risk evaluation of contaminated areas, such as Sepetiba Bay (Rio de Janeiro, Brazil), remains challenging. This study coupled Zn isotopic analyses with sequential extractions (BCR) to investigate the mechanisms of Zn transfer between legacy electroplating waste and the main environments in Sepetiba Bay. This metallurgical waste showed a light bulk isotopic signature (δ66/64ZnbulkJMC = +0.30 ±â€¯0.01‰, 2 s, n = 3) that was not distinct from the lithogenic geochemical baseline, but was different from signature of mangrove sediment considered as anthropogenic end member (δ66/64ZnJMC = +0.86 ±â€¯0.15‰) in a previous isotopic study in this area. Zn isotopic compositions of sediment samples (ranging from +0.20 to +0.98‰) throughout the bay fit a mixing model involving multiple sources, consistent with previous studies. In the metallurgic zone, the exchangeable/carbonate fraction (ZnF1) exhibited high Zn concentrations (ZnF1 = 9840 µg g-1) and a heavy isotopic composition (δ66/64ZnF1JMC = +1.10 ±â€¯0.01‰). This finding showed that, in some cases, the bulk isotopic signature of waste is not the most relevant criterion for evaluating trace metal dispersion in the environment. Indeed, based on the BCR, it was observed that part of the anthropogenic metallurgical Zn was redistributed from the exchangeable/carbonate fraction in the waste to the surrounding mangrove sediment. Then, this contaminated sediment with heavy δ66/64Zn values was exported to other coastal environments. In Sepetiba Bay, contaminated sediments revealed a large concentration of ZnF1 fraction (up to 400 µg g-1) with a heavy Zn isotopic signature. This signature also matched the Zn isotopic signature of oysters in Sepetiba Bay reported by other studies; hence, measurement of the isotopic exchangeable/carbonate fraction has important implications for tracing the transfer of anthropogenic Zn to biota.

Biological index based on epiphytic diatom assemblages is more restrictive than the physicochemical index in water assessment on an Amazon floodplain, Brazil.

Canadian Water Quality Index (CWQI) provides protection for freshwater life promoting healthy ecosystems and safeguarding human health. Biological Diatom Index (BDI) was developed to indicate the ecological status and water quality of freshwater systems. This paper evaluates the relations between the two different indices. During rising and falling, water samples were taken in the Curuai Floodplain, Brazil. CWQI was calculated using 14 physicochemical parameters and 1 microbiological parameter. The limits were established according to freshwater quality conditions and standards based on water use classes 1 and 2 determined in CONAMA 357 legislation and British Columbia. Canadian Water Quality Index categorization ranged from "marginal" to "excellent," most sampling units were "good" (71%), followed by "fair" (12%) and "excellent" (12%) water quality. Total phosphorus (38 times), chlorophyll a (20), dissolved oxygen (10), and total organic carbon (10) were the parameters that presented the most non-compliance values. Encyonema silesiacum (14%), Gomphonema parvulum (13%), and Navicula cryptotenella (12%) were the main taxa in the rising period, while G. lagenula, E. silesiacum, and Fragilaria capucina were the main taxa during the falling period. BDI ranges from I to V water quality classes. We observed "poor" to "very good" ecological status, with most sampling units "moderate" (52%) and "good" (29%). Water quality for class 2 was better than water quality for class 1, as the limits of the parameters evaluated were more restrictive in class 1 than in class 2 and the predominant uses of water require a higher degree of water purity. The biological index based on diatoms was the most restrictive index whose water classes and categorizations have shown an ecological status that could threaten the protection of aquatic communities on the Curuai floodplain. We suggest the combined use of both indices-physicochemical and biological for water quality assessment in this type of environment.

Evaluation of Total Mercury in Sediments of the Descoberto River Environmental Protection Area-Brazil.

To evaluate the total mercury accumulation (THg) in the Descoberto river basin environmental protection area (DREPA), nine sediment and water samples were collected from the Descoberto reservoir (lentic environment), and 23 in its tributaries (lotic environment), which are located in a densely urbanized area within the Descoberto river watershed, Brazil. The following physicochemical parameters of water were determined: dissolved oxygen (DO); hydrogen potential (pH); total dissolved solids (TDS); nitrate (NO3-); chloride (Cl-); temperature (T); sulfate (SO42-), and in sediment, the concentration of total mercury (THg) and volatile material (VM) was determined. THg concentrations in sediments showed a significant difference (p = 0.002) between tributaries (0.03 µg g-1 ± 0.02) and reservoir (0.08 µg g-1 ± 0.04), indicating accumulation in the lentic environment. Most of the results evaluated for ecotoxicological risks presented values below the concentration, at which adverse effects would rarely be observed, ERL (effects range low). However, in relation to the enrichment factor (EF), applied to identify the anthropogenic contribution, the results indicate that most of the samples are moderately polluted through atmospheric deposition due to vehicular traffic and agriculture. These results show that the likelihood of methylation in the lentic environment is higher than in the lotic environment.

Influence of hydrodynamic conditions on the degradation of 1-butyl-3-methylimidazolium chloride solutions on boron-doped diamond anodes.

This study assessed the influence of hydrodynamic conditions on the degradation process of 1-butyl-3-methylimidazolium chloride (BMImCl) solution on a boron-doped diamond anode in a filter-type electrochemical reactor configuration. The results show that this parameter did not significantly affect this process when operating in the laminar regime. However, in the transition regime (Re ≥ 2000), higher flow rates resulted in a faster removal of BMImCl and total organic carbon, making the process more efficient. Following BMImCl degradation, nitrates were generated at the cathode, then reduced at the cathode to ammonium; combination with free chloride produced at the anode led to the transformation of chloride into combined chlorine forms instead of more toxic oxianions such as chlorate and perchlorate. Thus, the flow rate can be a key parameter for defining operating conditions in which the target BMImCl is more effectively degraded with reduced generation of undesirable secondary products.

Oral bioaccessibility of inorganic contaminants in waste dusts generated by laterite Ni ore smelting.

The laterite Ni ore smelting operations in Niquelândia and Barro Alto (Goiás State, Brazil) have produced large amounts of fine-grained smelting wastes, which have been stockpiled on dumps and in settling ponds. We investigated granulated slag dusts (n = 5) and fly ash samples (n = 4) with a special focus on their leaching behaviour in deionised water and on the in vitro bioaccessibility in a simulated gastric fluid, to assess the potential exposure risk for humans. Bulk chemical analyses indicated that both wastes contained significant amounts of contaminants: up to 2.6 wt% Ni, 7580 mg/kg Cr, and 508 mg/kg Co. In only one fly ash sample, after 24 h of leaching in deionised water, the concentrations of leached Ni exceeded the limit for hazardous waste according to EU legislation, whereas the other dusts were classified as inert wastes. Bioaccessible fractions (BAF) of the major contaminants (Ni, Co, and Cr) were quite low for the slag dusts and accounted for less than 2 % of total concentrations. In contrast, BAF values were significantly higher for fly ash materials, which reached 13 % for Ni and 19 % for Co. Daily intakes via oral exposure, calculated for an adult (70 kg, dust ingestion rate of 50 mg/day), exceeded neither the tolerable daily intake (TDI) nor the background exposure limits for all of the studied contaminants. Only if a higher ingestion rate is assumed (e.g. 100 mg dust per day for workers in the smelter), the TDI limit for Ni recently defined by European Food Safety Authority (196 µg/day) was exceeded (324 µg/day) for one fly ash sample. Our data indicate that there is only a limited risk to human health related to the ingestion of dust materials generated by laterite Ni ore smelting operations if appropriate safety measures are adopted at the waste disposal sites and within the smelter facility.

A critical examination of the possible application of zinc stable isotope ratios in bivalve mollusks and suspended particulate matter to trace zinc pollution in a tropical estuary.

The application of zinc (Zn) isotopes in bivalve tissues to identify zinc sources in estuaries was critically assessed. We determined the zinc isotope composition of mollusks (Crassostrea brasiliana and Perna perna) and suspended particulate matter (SPM) in a tropical estuary (Sepetiba Bay, Brazil) historically impacted by metallurgical activities. The zinc isotope systematics of the SPM was in line with mixing of zinc derived from fluvial material and from metallurgical activities. In contrast, source mixing alone cannot account for the isotope ratios observed in the bivalves, which are significantly lighter in the contaminated metallurgical zone (δ66ZnJMC = +0.49 ± 0.06‰, 2σ, n = 3) compared to sampling locations outside (δ66ZnJMC = +0.83 ± 0.10‰, 2σ, n = 22). This observation suggests that additional factors such as speciation, bioavailability and bioaccumulation pathways (via solution or particulate matter) influence the zinc isotope composition of bivalves.

Stroke volume changes induced by a recruitment maneuver predict fluid responsiveness in patients with protective ventilation in the operating theater.

During abdominal surgery, the use of protective ventilation with a low tidal volume, positive expiratory pressure (PEEP) and recruitment maneuvers (RMs) may limit the applicability of dynamic preload indices. The objective of the present study was to establish whether or not the variation in stroke volume (SV) during an RM could predict fluid responsiveness.We prospectively included patients receiving protective ventilation (tidal volume: 6 mL kg, PEEP: 5-7 cmH2O; RMs). Hemodynamic variables, such as heart rate, arterial pressure, SV, cardiac output (CO), respiratory variation in SV (ΔrespSV) and pulse pressure (ΔrespPP), and the variation in SV (ΔrecSV) as well as pulse pressure (ΔrecPP) during an RM were measured at baseline, at the end of the RM, and after fluid expansion. Responders were defined as patients with an SV increase of at least 15% after infusion of 500 mL of crystalloid solution.Thirty-seven (62%) of the 60 included patients were responders. Responders and nonresponders differed significantly in terms of the median ΔrecSV (26% [19-37] vs 10% [4-12], respectively; P < 0.0001). A ΔrecSV value more than 16% predicted fluid responsiveness with an area under the receiver-operating characteristic curve (AU) of 0.95 (95% confidence interval [CI]: 0.91-0.99; P < 0.0001) and a narrow gray zone between 15% and 17%. The area under the curve values for ΔrecPP and ΔrespSV were, respectively, 0.81 (95%CI: 0.7-0.91; P = 0.0001) and 0.80 (95%CI: 0.70-0.94; P < 0.0001). ΔrespPP did not predict fluid responsiveness.During abdominal surgery with protective ventilation, a ΔrecSV value more than 16% accurately predicted fluid responsiveness and had a narrow gray zone (between 15% and 17%). ΔrecPP and ΔrespSV (but not ΔrespPP) were also predictive.

Using DET and DGT probes (ferrihydrite and titanium dioxide) to investigate arsenic concentrations in soil porewater of an arsenic-contaminated paddy field in Bangladesh.

Arsenic concentration in the pore water of paddy fields (Csoln) irrigated with arsenic-rich groundwater is a key parameter in arsenic uptake by rice. Pore water extracts from cores and in situ deployment of DET and DGT probes were used to measure the arsenic concentration in the pore water. Ferrihydrite (Fe) and titanium dioxide (Ti) were used as DGT binding agents. Six sampling events during different growing stages of the rice, inducing different biogeochemical conditions, were performed in one rice field. A time series of DGT experiments allow the determination of an in situ arsenic diffusion coefficient in the diffusive gel (3.34×10(-6) cm(2) s(-1)) needed to calculate the so-called CDGT(Fe) and CDGT(Ti) concentrations. Over 3 days of a given sampling event and for cores sampled at intervals smaller than 50 cm, great variability in arsenic Csoln concentrations between vertical profiles was observed, with maxima of concentrations varying from 690 to 2800 µg L(-1). Comparisons between arsenic measured Csol and CDET and calculated CDGT(Fe) and CDGT(Ti) concentrations show either, in a few cases, roughly similar vertical profiles, or in other cases, significantly different profiles. An established iron oxyhydroxide precipitation in the DET gel may explain why measured arsenic CDET concentrations occasionally exceeded Csoln. The large spread in results suggests limitations to the use of DET and type of DGT probes used here for similarly representing the spatio-temporal variations of arsenic content in soil pore water in specific environmental such as paddy soils.