Guandu River Research Articles

Water Scarcity Risk Index: A Tool for Strategic Drought Risk Management

Drought events have affected many regions of the world, having negative economic, environmental and social impacts. When accompanied by increasing water demands, these events can lead to water scarcity. Since droughts can significantly vary in each geographic area, several indices have been developed around the world. Hazard indexes are commonly used to predict meteorological, agricultural and hydrological droughts. These indexes intend to predict hazards, but they do not provide information on when and where deficits can have negative consequences. This study presents a new planning and decision-support tool for monitoring water scarcity situations in a given region. This tool, called the Water Scarcity Risk Index (W-ScaRI), is formed by two subindices, which are proposed to describe a hazard and its consequences. Each subindex was constructed using a group of indicators and indices selected from the technical literature or originally proposed in this work. The W-ScaRI was applied to the Rio de Janeiro Metropolitan Region (RJMR), supplied with water by the Guandu/Lajes/Acari system. The RJMR is one of the most densely populated regions in Brazil, located in an area that has no natural water bodies capable of meeting its supply needs. Therefore, the Guandu River, which, in fact, is formed by two discharge transpositions from the Paraíba do Sul River, is the main drinking water supply source for this region. The RJMR suffered the consequences of unexpected, prolonged droughts in the Southeast region in 2003 and 2014–2015, leading the local authorities to implement temporary emergency measures in the management system of Paraíba do Sul and Guandu Basins, avoiding water shortage but showing the urgent need for planning and management support tools to anticipate possible future problems. The results of the study show that the formulation of the W-ScaRI can represent the water scarcity risk in a relatively simple way and, at the same time, with adequate conceptual and methodological consistency.

Dinâmica e manutenção do serviço ecossistêmico de manutenção da purificação da água na Região Hidrográfica do Rio Guandu, Rio de Janeiro, Brasil

ABSTRACT The present study aimed to develop a methodology for analyzing the dynamics and maintenance of the water purification ecosystem service in the water bodies of the Guandu River Hydrographic Region, responsible for water supplying the Rio de Janeiro Metropolitan Region, characterized by the presence of water transfers and low levels of effluent treatment. The dynamics of this service occurs through an ecosystem flow, influenced by the volume of water that moves from one region to another. The methodology consisted of reviewing studies of ecosystem flows, building a database, classifying impacts on water purification in hydrological planning units from a similarity dendrogram, analyzing indicators related to water demands and availability of these units, and developing an ecosystem flow diagram of water purification. The effects of transfers on the maintenance and flow of water purification were also analyzed from the comparison between the real scenario (which considers the presence of the existing hydraulic infrastructure) and the natural scenario (which disregards it). The results showed that the worst situation of maintenance of water purification is in the western part of the region, and the demands for it requires more than double the volume of withdrawn water to supply the local population and industry.

Optimization of water allocation networks in highly engineered basins: The case of Guandu River basin, Rio de Janeiro State, Brazil

During the last decades, metropolitan areas with a large population and economic size have mushroomed, modifying the urban geography and natural environment. Along with the rising of megacities, highly engineered basins have been created, providing resource security regarding water and energy. The coastal Guandu River basin in Brazil represents an artificial basin that has been heavily intervened for decades. The basin receives almost ∼80% of the water by transfers from the Paraiba do Sul River Basin System and has an associated hydroelectric complex that generates power for the national network. It is the primary source of water and energy for the Rio de Janeiro Metropolitan Area, home to ∼13 million people. Recently, water availability for this region has been jeopardized by drought conditions due to changing rainfall patterns and competition for water resources with other users such as Sao Paolo Metropolitan Area. This study focuses on the development of an optimization framework (WANAB model) for water resources management at the macroscopic level in the Guandu Basin to guarantee economic viability and water resources sustainability. The model incorporates parameters and equations for hydrological, and engineered water and hydropower processes to determine the optimal water allocation network. Also, a multi-criteria analysis is proposed to evaluate the water availability considering different scenarios. The results show that through optimization, it is possible to have a water availability of up to ∼24 m3/s in the Guandu River basin by integrating elements such as water storage systems, grey and blackwater treatment plants with capacities up to ∼39 m3/s and ∼9 m3/s, respectively. The results show that it is possible to reach a water availability of 21 m3/s in the scenario, considering the reduction of water transfers from outside the basin due to climate change. However, the major impact is observed in the hydropower generation, decreasing from ∼2270 GWh/y to ∼1950 GWh/y. The WANAB model represents a decision-making and policy tool for optimizing water allocation networks and may be adapted for other highly engineered basins.

First report of the invasive Ceratium furcoides (dinoflagellate) in Paracambi Reservoir, Rio de Janeiro: Risks to the world's largest domestic water treatment plant

AbstractCeratium furcoides (Dinophyta) have gained international attention as invasive aquatic species, especially in South America, due to its fast proliferation into various aquatic systems and the subsequent adverse impacts on water quality and native biota. The present study reports the detection of dense populations of C. furcoides in the Paracambi Small Hydropower Plant (SHP) located in the Guandu River basin. Sampling was conducted at five sites during two sampling events in 2019 and 2020 during different seasons (spring and summer), respectively. We used two different standardized sampling methods, including surface collections (SS) (100‐ml) traditionally used for quantitative analysis of inland water phytoplankton, as well as filtration of 20‐L sub‐surface water (FS) through a zooplankton net. The cell densities were higher in SS (599 individuals/ml) than in FS (0.068 individuals/ml), possibly indicating a patchy distribution of Ceratium in the surface water layers. The total cell length exhibited high values (mean length of 249‐μm; mean width of 67‐μm), possibly accounting for water treatment impairment, an inability of zooplankton to consume them and/or fish gill clogging. This new observation within an extensively investigated area, and a source of water for nine million people, in the present study advocates for integrated samplings that also consider a search for cysts accumulated in the bottom sediments, as well as more detailed spatial and temporal investigations considering the salient features of C. furcoides’ populations.

Determination of Fipronil and Fipronil-Sulfone in Surface Waters of the Guandu River Basin by High-Performance Liquid Chromatography with Mass Spectrometry.

Fipronil (FIP) is a broad-spectrum insecticide used in the industrial, residential and agricultural sectors, which presents environmental and human health risks. Studies report its presence in aquatic environments in several countries, but in Brazil reports are scarce. The aim of this work was to evaluate the presence of fipronil and fipronil sulfone in surface waters through a validated analytical method by LC-MS according to INMETRO and USEPA in eight sampling sites in two seasons (summer and autumn, 2020) in Guandu River basin, in the state of Rio de Janeiro. FIP was quantified in the concentration range of 0.132-2.44μg/L, while FIP-S was detected in most samples. This is the first study on the occurrence of FIP and FIP-S in the Guandu River basin, presenting values high enough to justify the need for monitoring studies in a region of great importance for the city of Rio de Janeiro.

Risk of Collapse in Water Quality in the Guandu River (Rio de Janeiro, Brazil).

The Guandu River, one of the main rivers in the state of Rio de Janeiro, provides water for more than nine million people in the metropolitan region. However, the Guandu has suffered from massive domestic and industrial pollution for more than two decades, leading to high levels of dissolved total phosphorus, cyanobacteria, and enteric bacteria observed during the summers of 2020 and 2021. The use of Phoslock, a palliative compound, was not effective in mitigating the levels of phosphorus in the Guandu River. Furthermore, potable water driven from the river had levels of 2-MIB/geosmin and a mud smell/taste. With all these problems, several solutions are proposed for improving the Guandu River water quality, including establishment of (i) sewage treatment plants (STPs), (ii) strict water quality monitoring, (iii) environmental recovery (e.g., reforestation), and (iv) permanent protected areas. The objective of this paper is to verify the poor water quality in the Guandu and the ineffectiveness and undesired effects of Phoslock.

Three new species of Urocleidoides (Monogenoidea: Dactylogyridae) parasitizing characiforms (Actinopterygii: Characiformes) in Tocantins River, states of Tocantins and Maranhão, and new record for U. triangulus in Guandu River, state of Rio de Janeiro, Brazil

Three new species of Urocleidoides Mizelle & Price, 1964 are described from the gills of characiform fishes in the Tocantins River and its tributaries. Urocleidoides boulengerellae sp. nov. is described from Boulengerella cuvieri (Spix & Agassiz, 1829) and differs from all its congeners by the dorsal bar with a long posteromedial projection; male copulatory organ with 2–3 counterclockwise rings and a base with a flange; an accessory piece comprising a robust Y-shaped unit and a sheath-like unit; and a highly sclerotized vaginal canal. Urocleidoides paratriangulus sp. nov., described from Psectrogaster amazonica Eigenmann & Eigenmann, 1889, Cyphocharax gouldingi Vari, 1992, Caenotropus labyrinthicus (Kner, 1858) and Mylesinus paucisquamatus Jégu & Santos, 1988, is most similar to Urocleidoides triangulus (Suriano, 1981) Rossin & Timi, 2016 based on the shape of the anchors and bars but differs from U. triangulus in the morphology of the projection of the dorsal bar, the number of rings of male copulatory organ, and by the smaller size of members of hook pairs 1 and 5 compared with those of the remaining pairs. Urocleidoides tocantinensis sp. nov. is easily distinguished from all other species of the genus by the morphology of the vagina, which present a vaginal vestibule with a membranous cap. Urocleidoides triangulus is reported from its type host in the Guandu River, state of Rio de Janeiro. The present study increases the number of Urocleidoides species to 37 recognized species that fit all the generic characters.

Antimicrobial resistance genes and bacterial diversity in sediments of Guandu River, Brazil

Rivers provide essential water resources for humans. However, appear to be reservoirs of antimicrobial-resistant genes and dispersal routes of resistant pathogens because human activities promptly influence them. Sediments are the most propitious substrates for bacteria survival and can act as an antimicrobial reservoir. Three sediment samples were collected upstream of the water catchment point of the Guandu Water Treatment Plant (ETA Guandu) to evaluate microbial diversity and antimicrobial resistance genes to sulfonamide (sul1, sul2), tetracycline (tetA, tetB) and beta-lactam (blaCTX-M, blaoxa24 and blaoxa58) by PCR. The most abundant phylum in all samples was Proteobacteria, which was also the most dominant in sediments presenting a pattern already reported in the literature for diversity in tropical and temperate climate rivers. Sulfonamide resistance genes were detected in all samples. The blaCTX-M gene was detected only in one sample, and tetA, tetB, blaoxa24 and blaoxa58 genes were not found in any sample. The presence of antimicrobial resistance genes sul1, sul2, and blaCTX-M indicate that sediments can act as a reservoir of resistance. These findings will provide new data about the bacterial community and antimicrobial resistance genes in Brazilians river sediments.

Assessing glyphosate concentrations in six reservoirs of Paraíba do Sul and Guandu River Basins in southeast Brazil

Glyphosate is a popular herbicide used worldwide, and several studies consider it to be an environmental hazard affecting human health. The present study aimed to detect glyphosate in six different reservoirs of Paraíba do Sul and Guandu River Basins in Southeast Brazil, used for multiple purposes, including fishery activities and domestic water supply. Ion chromatography was used to analyze the water samples, as it is a fast and environmentally friendly technique to detect glyphosate. Our results revealed that, despite differences related to trophic state, season of the year or distance to urban areas, glyphosate was detected in all reservoirs and in three of them with concentrations above the limit imposed by Brazilian legislation. Among the environmental variables studied, turbidity presented the highest correlation with glyphosate concentrations. The effect of rainfall increasing turbidity in the rivers reinforces the importance of draining waters from surrounding areas that transport glyphosate into the aquatic ecosystems. The detection of the herbicide in the various systems confirms the wide use of this compound in the drainage basins of the studied reservoirs and highlights the importance of water monitoring. Further, the results reveal how urgent and important it is to explore through laboratory experiments the pathways of degradation of this herbicide in tropical and subtropical aquatic environments together with its effects on flora and fauna.

The recapture of Leptopanchax opalescens (Aplocheiloidei: Rivulidae), a critically endangered seasonal killifish: habitat and aspects of population structure

Leptopanchax opalescens(Myers, 1942) is a small seasonal killifish endemic to coastal drainages in the state of Rio de Janeiro, Brazil.Leptopanchax opalescenswas recaptured in temporary open vegetation pools (22°42.35’S, 43°41.59’W) in the hydrographic basin of the Guandu River, state of Rio de Janeiro, Brazil, after eight years without records. Information on habitat and population parameters (Capture per unit area (CPUA), size, sex ratio and length-weight relationship (LWR)) are given to provide subsidies for the conservation of this species. Specimens were captured during the rainy season (January-April 2020) in shallow pools (mean depth = 21 ± 12 s.d. cm), with relatively acidic pH (5.2 ± 0.8) and low concentrations of dissolved oxygen (3.5 ± 1 mg/L). The estimated CPUA of the population was 0.89 fish/m2. The total length (TL) of males ranged from 21.1 to 28.8 cm, and females ranged from 17.0 to 31.2 mm. Males were significantly larger (t-test = 2.04, p < 0.05) than females, which were in greater proportion (2.83Female: 1Male, p < 0.001). A positive allometric coefficient (b = 3.19) was found through length-weight relationship curve, indicating that individuals of the species gain proportionally more increment in weight than in length.Leptopanchax opalescensis a critically endangered species, and the results of this study contribute to the knowledge of the distribution, population structure and conservation of the species and its natural habitats.

Development and validation of an analytical method for detection and quantification of benzophenone, bisphenol A, diethyl phthalate and 4-nonylphenol by UPLC-MS/MS in surface water

Guandu River is the main water source for 9 million inhabitants in Rio de Janeiro city and some others included in the metropolitan region of the Rio de Janeiro State, Brazil. Here, the development of a chromatographic method and its application to assess the occurrence of 4-nonylphenol (4NP), benzophenone (BP), bisphenol A (BPA) and diethyl-phthalate (DEP), known as endocrine disruptors (EDs), is reported. Sample were prepared by solid phase extraction (SPE) with C18 cartridge and methanol as elution solvent. Validation of analytical method followed the United States Environmental Protection Agency protocol (USEPA 8000D guide) and selectivity, matrix effect, linearity, precision, accuracy, robustness, limit of detection (LOD) and limit of quantification (LOQ) were evaluated. The recovery was greater than 90%, accuracy was found between 80% and 115% and relative standard deviation (RSD) below 11.03%. LOQ ranged from 10.0 to 50.0 ng L−1, while the LOD ranged from 0.87 to 5.72 ng L−1. The coefficients of determination (R2) were greater than 0.99 for all compounds within a linear ranges of 10.0 to 500 ng L−1 for 4NP and BP and 50.0 to 500 ng L−1 for BPA and DEP. The method was therefore considered selective and robust for all micropollutants. Matrix effect was observed for BP, 4NP and DEP. The developed method was applied to analyze five samples collected monthly during 2018 at a selected sampling point of a river in Rio de Janeiro State. The maximum concentrations found for BPA, BP, DEP and 4NP were 182.04, 286.20, 2.56×103 and 13.48 ng L−1 respectively. These values are high enough to justify an investigation on the presence of these micropollutants in drinking water as well as to extend the monitoring for the search of similar pollutants and their metabolites.

Effects of native vegetation recovery on soil loss

Considering the economic and environmental damages caused by soil loss, it is clear the necessity of information about the effect that vegetation has on soil loss rate. The present paper uses the Revised Universal Soil Loss Equation with the objective of investigating soil loss under a native vegetation recovery (Atlantic Forest) and present conditions in the Guandu river basin, located in the Southwest portion of Brazil. It was identified that reforesting 8.11% of the basin, it would promote 28.73% reduction in the mean annual soil loss compared to the actual land use. Although the paper uses a particular vegetation recovery situation (areas protected by the Brazilian Forest Code), the intention here was to clarify the role that any native vegetation protection exercises on soil loss.

Evaluation of the cytotoxic and genotoxic potential of waters of the Paraíba do Sul River Basin - RJ through the Allium cepa test system

The public water supply of the Rio de Janeiro metropolitan region is highly dependent on transposition from the Paraíba do Sul River: 70% of the water is diverted to the Piraí River and then passes through a series of other rivers and reservoirs, finally discharging in the Guandu River. During this path, the water is exposed to many sources of pollution. This makes the quality of the raw water that reaches the Guandu Treatment Station (WTS) highly vulnerable. This article reports the analysis of the cytogenotoxic potential of water samples collected at four different points along the Piraí River downstream from the transposition point, utilizing the Allium cepa test system. The samples were collected in two periods, the dry and wet seasons. The water at all four collection points presented some level of cytogenotoxicity, with the presence in the test cells of large nucleoli, multiple nucleoli, nuclear buds, lagging chromosomes, sticky chromosomes, karyorrhexis, cytoplasmic shrinkage and changes of the mitotic index. The samples collected during the dry season had a larger number of cells with alterations, indicating that the cytogenotoxic potential varies in function of the time of year, depending on the volume of contaminated effluents. The results obtained along with data from the Rio de Janeiro State Environmental Institute (INEA) for the same period reveal the importance of monitoring along with proper sanitation and sewage treatment, and that the presence of pollutants not only hampers water treatment, but also poses risks to organisms at different trophic levels, including humans.

Sustainable provision of raw water based on the management of ecosystem services in small watersheds

The differentiated effects of the provision of environmental services in a watershed are due to the capacity of regularization of outflows in its mouth. In impacted areas, this environmental function is affected, and in some situations, it ceases to exist completely. This study characterized the soil and the production of sediments in anthropic watersheds, with the purpose of describing and evaluating the environmental services offered by a watershed undergoing anthropic transformation. The analyses show that the water flow in the remaining watersheds was preferably horizontal in the transmission zone, and these areas represent almost all areas. The values of hydraulic conductivity suggest that the infiltration decreases with soil depth; this fact is corroborated by the values of bulk density. The natural regions of water accumulation, the floodplains or outcrops zones, are small and do not have direct contact with the main floodplain present in the Guandu River Basin, making it impossible to recharge through other areas. Even so, water balance shows that the set of measures implemented ensured that the deficit water demand was supplied during the years of operation, even in times of water deficit. Likewise, the retention of solids in the settling tanks and in the drainage system prevented some 29,000 t of sediment from being carried between the years of 2012 and 2015.

Influence of the Holocene relative sea level on the coastal plain of Sepetiba Bay (Southeast Brazil)

This work analyzes the results of the SP2 core (50.30 m length) collected in the coastal plain of Sepetiba Bay (SB; SE Brazil), 2 km away from the Guandu River mouth (latitude 22° 55′S, longitude 43° 46′W). It aims to study the influence of the Holocene relative sea level (RSL) on the coastal plain of SB. After description, the SP2 core was sampled at every 5 cm for grain size, geochemical, mineralogical and foraminiferal analyses. Four radiocarbon dates obtained in the first 18 m were modulated with Bayesian statistics. The SP2 core is composed of basement rocks, gneisses (50.30–43.80 m); river sediments (43.80–21.00 m) up to about ≈ 5.0 kyr BP; a sediment package marked by sudden textural and compositional changes, accumulated between ≈ 5.0 and 4.7 kyr BP; muddy sediments deposited between 4.7 and 0.8 kyr BP (18.80–3.35 m) with intercalations of sandy levels; an upper part of disturbed embankment sediments used for the implantation of Santa Cruz Thermoelectric Power Plant. The fluvial sands accumulated before ≈ 5.0 kyr BP were deposited before the maximum Mid-Holocene relative sea level. They were probably eroded and transported by the drainage network of the N region of SB, namely by the Guandu River. Between ≈ 4.5 and 3.5 kyr BP, the foraminiferal abundance and assemblage composition indicate that the study site was a shallow marine environment, due to the Mid-Holocene relative sea-level highstands (MHSLH). Between ≈ 3.5 and 3.0 kyr BP, the sediment accumulation rate (SAR) was the lowest of the last ≈ 5 kyr BP and the study site was exposed to subaerial weathering processes, in a scenario of the relative sea-level drop. A new phase of marine influence was recorded between ≈ 3.0 and 1.9 kyr BP, associated with the highest SAR of this record, up to ≈ 27.4 m/kyr BP. Between ≈ 1.9 and 1.8 kyr BP, the study site was under subaerial weathering processes. Since then the SAR reduced significantly to a mean value of ≈ 4.5 m/kyr and, between ≈ 1.8 and 0.8 kyr BP, the study site was again under the marine influence. Foraminifera were not found, after ≈ 0.8 kyr BP, in the SP2 core. However, the occurrence of a shallow marine environment was identified in another core, between ≈ 1.4 and 0.35 kyr BP, in the Guaratiba Mangrove, NE of SB. The results of the SP2 core suggest that MHSLH left a striking record in the study area, although some of the identified environmental changes are probably related to adjustments of the lower course of Guandu River and tidal channels and variations in the configuration of sandy littoral strands. The growth of a barrier–island system, the Marambaia barrier island, since the last ≈ 8–7.5 kyr BP may also have induced changes in the study area.

Urban sustainability: Analyzing the water-energy nexus in the Guandu river basin, Rio de Janeiro, Brazil

Urban sustainability has been one of the most important issues in the last decades. The modification of watercourses and their integration to power production facilities have resulted in severe environmental impacts around the globe. This study presents a sustainability analysis to examine the current state of the Guandu river basin Brazil. The approach includes the development of a hydrological model to simulate the stream flow, and an evaluation of the impacts of potential scenarios projected for 2035. Future scenarios included climate and land use change, and water transfers from surrounding basins. The results show that future scenarios might distress the total volume of water naturally captured in the basin mainly because of significant changes in precipitation patterns. Such changes could reduce the amount of water and electricity supply in the region, as well as the sustainability of water resources. The proposed model can be used as a decision making support tool to search for sustainable strategies for water and electricity distribution in highly urbanized systems.

The fish fauna of the upper Piraí drainage, a transposed mountain river system in southeastern, Brazil

An annotated checklist of the ichthyofauna from the upper Piraí river drainage is provided. The Piraí river was a major right-bank tributary of the Paraíba do Sul river, but it has been artificially diverted to the coastal Guandu river system in southeastern Brazil to generate electric power and water for the metropolitan area of Rio de Janeiro. Based on our field sampling of 23 sites, 32 species belonging to 24 genera and 12 families were collected in 6 headwater tributaries of the Piraí river between 2009 and 2016. Phalloceros harpagos (Lucinda, 2008), Astyanax intermedius (Eigenmann, 1908), and Neoplecostomus microps (Steindachner, 1877b) were the most abundant and most widely distributed species in the samples. The sampled ichthyofauna is mostly composed by species from the Paraíba do Sul basin. Eight species are reported for the first time in the upper Piraí drainage, showing the importance of continuous ichthyofaunal surveys of fish in remaining areas of Atlantic Forest.

Occurrence of phoresy between Ancistrus multispinis (Actinopterygii: Siluriformes) and Ichthyocladius sp. (Diptera: Chironomidae) in Atlantic forest streams, Southeastern Brazil

. Phoretic relationships often bring large advantages to epibionts. By attaching themselves to mobile hosts, epibionts are able to: expand their ranges without spending energy, reduce their risk of being predated, and increase their probability of finding food. We assessed the phoretic relationship between the siluriform fishAncistrusmultispinis(Regan, 1912) and the chironomid larvaIchthyocladiussp. in three streams of the Atlantic forest in southeastern Brazil. We evaluated changes in epibiont distribution throughout the body regions of the host and among three different aquatic systems. We had predicted that certain body regions are more prone to support epibiont attachment, and that epibiont prevalence increases with increased host size and quality of the aquatic system. Three streams (Santana, São Pedro and D’Ouro), tributaries of the Guandu River, were sampled during 2010 and 2011. A total of 102 specimens ofA.multispiniswere collected and analyzed. Epibionts were found in fourteen of fifteen body regions of the host. Observation from scanning electron microscopy revealed that Chironomidae larvae fix themselves to the spicules through the anal prolegs, not at the skin, as previously reported. The amount of epibionts (degree of infestation) was significantly correlated with fish size in the Santana Stream (r = 0.6, p < 0.01), and São Pedro Stream (r = 0.56, p < 0.01), but not in the D’Ouro Stream, the most altered of the three. The presence of epibionts on the body of the fish is directly correlated with the availability of spicules on the fish’s body, the largest numbers of infestations being found in structures associated with swimming (caudal and pectoral fins), since the swimming movement can create favorable conditions (e.g., suspension of organic particles, increasing oxygenation) for the epibiont.

Determination of 4-Nonylphenol in Surface Waters of the Guandu River Basin by High Performance Liquid Chromatography with Ultraviolet Detection

4-Nonylphenol, a degradation product of ethoxylated alkylphenols, due to its harmful effects on the environment, has been banned in European Union countries, alongside their precursors. The guide on quality of drinking water from the United States Environmental Protection Agency (US EPA) recommends a maximum concentration of 28 µg L-1 for fresh water. In Brazil, there is no clear legislation containing values of maximum concentration of 4-nonylphenol. Due to this lack of regulation, a continuous monitoring is necessary for this pollutant in environmental samples. The occurrence of 4-nonylphenol (4-NP) in the surface waters of Guandu River in the state of Rio de Janeiro, Brazil, was studied by using solid-phase extraction and reversed phase liquid chromatography separation with UV detection. The analytical method satisfies these requirements, being able to detect and quantify 4-NP in a desired concentration range. Of the 19 samples analyzed, 4-nonylphenol was detected in 12, quantified in 2, showing concentration levels of 1.73 and 2.32 µg L-1 in Santa Cruz and Paracambi, respectively. This is the main hydrographic basin in the state of Rio de Janeiro, where water is collected for treatment and later distributed to most cities in the metropolitan region, including Rio de Janeiro City, and these results are therefore alarming.

Freshwater mollusks and environmental assessment of Guandu River, Rio de Janeiro, Brazil

Abstract The Guandu River Basin is extremely important to state of Rio de Janeiro, as a water supplier of several municipalities. However, the malacological knowledge and environmental status is not well known to this basin. The aim of this paper is to present an inventory of freshwater mollusks, as well as an environmental assessment through a Rapid Assessment Protocol, of ten sampling sites at Guandu River basin in six municipalities (Piraí, Paracambi, Japeri, Seropédica, Queimados and Nova Iguaçu). Thirteen species of molusks were found, eight native (Pomacea maculata, Biomphalaria tenagophila, Gundlachia ticaga, Gundlachia radiata, Omalonyx matheroni, Diplodon ellipticus, Anodontites trapesialis and Eupera bahiensis) and five exotics (Melanoides tuberculata, Ferrissia fragilis, Physa acuta, Corbicula fluminea and Corbicula largillierti). The environmental analysis ranked most sites as “modified”. The expansion of exotic species with their associated negative effects, as well the gap in knowledge of native species calls attention to the need of future studies of biology and ecology of the species found.