Abstract The irregular hydrological regime in Patos Lagoon estuary has been suggested as having a distinctive influence on sulfur speciation in sediments. We performed an investigation for different prolonged hydrological conditions focusing on the distribution of sulfides (acid volatile sulfide (AVS), chromium reducible sulfide (CRS), and Free-S2-) in sediment cores from salt marsh and non-vegetated shallow zone. Significant differences in sulfides content and distribution between the different hydrological periods were found. The predominance of more reducing conditions was observed during the freshwater period. It reflects a higher total reducible inorganic sulfur (TRIS) content in this period, with a great accumulation of AVS in sediments (> 100 mg kg-1). In the maximum salinity period, more oxidizing conditions prevailed, which significantly decreased the concentrations of metastable sulfides. The intense bioirrigation process exerts control over sulfide formation and distribution, which is as important as that exerted by the variations of the hydrological regime.

ResumoObjetivo: O objetivo do presente estudo foi avaliar a concentração de Hg em duas espécies de peixes (Astyanax sp e Corydoras paleatus) e seu uso potencial como biomonitor, a fim de saber se o uso de pesticidas e fertilizantes na lavoura pode levar a contaminação por Hg ao ambiente aquático adjacente.MétodosSolo, material particulado em suspensão e amostras de peixes foram coletadas em um campo de arroz no sul do Brasil. Um sistema de vapor frio acoplado a um espectrofotômetro de absorção atômica (GBC 932) foi usado para as determinações de Hg total nas amostras.ResultadosO solo da lavoura de arroz apresentou concentração de Hg 2 vezes mais elevada (média de 31 ng g–1), em comparação com a área controle (não cultivado). A concentração de Hg no material particulado em suspensão dos canais de irrigação do arroz (média de 232,5 ± 44,2 ng g–1) é 1,5 vezes mais elevada do que na área controle. Os espécimes de peixes Astyanax sp analisados na área de cultivo mostraram concentração de Hg 4 vezes maior e, significativamente diferentes da área controle. A concentração média de Hg em peixes foi: 51,7 ± 19,5 ng g–1 em Astyanax sp e 156,8 ± 44,0 ng g–1 em Corydoras paleatus.ConclusõesConsiderando a regressão linear e o teste de hipótese de de Man Whitney para a concentração de Hg em tecidos de peixes da lavoura de arroz, sugere que Astyanax sp. pode ser uma bom biomonitor de contaminação Hg, enquanto Corydoras paleatus é um biomonitor potencial. No entanto, mais estudos com Corydoras são necessárias, a fim de agregar consistência a este estudo.

Aim: The aim of present study was to evaluate the Hg concentration in two species of fish (Astyanax sp and Corydoras paleatus) and its potential use as a biomonitor, in order to know if the use of pesticides and fertilizers in paddy can enhance the Hg contamination to adjacent aquatic environment.MethodsSoil, suspended particulate matter and fish samples were sampled in a paddy field in South Brazil. A cold vapor system, coupled with a GBC 932 atomic absorption spectrophotometer was used for total Hg determinations in samples.ResultsThe paddy soil shows Hg concentration 2-fold higher (mean 31 ng g-1) in comparison to background areas (not cultivated). Suspended particle matter Hg concentration in paddy channels (mean 232.5 ± 44.2 ng g–1) are 1.5 times higher than the regional background. The analyzed fish specimens Astyanax sp in paddy showed Hg concentration 4-fold higher and significant different to background area. The mean Hg concentration in fish was: 51.7 ± 19.5 ng g–1 in Astyanax sp and 156.8 ± 44.0 ng g–1 in Corydoras paleatus.ConclusionsConsidering the linear regression and Man whitney test hypothesis to Hg concentration in fish tissue from paddy suggests that Astyanax sp. can be a good biomonitor of Hg contamination, whereas Corydoras paleatus is a potential biomonitor. However, more studies with Corydoras are necessary in order to aggregate consistency to this hypothesis.

The objective of this study was to determine the influence of marine shallow-water hydrothermal systems in Mapachitos, bahia Concepcion, on the composition of surficial sediments in the surrounding area of this bay. The following elements Al, As, Ba, Ca, Cd, Co, Cs, Cu, Fe, Hg, Li, Mn, Mo, Ni, Rb, S, Ti, U, V, Zn, Corg, and Cinorg were determined in sediment samples. The calculated CaCO3 values in the sediments within some spots of the study area were as high as 90% (with an average of 61 %). The concentration of organic carbon in the sediments was approximately 1%. The total element contents in the sediments were compared with Earth's crustal average, and enrichment factors (EF) were calculated using Al as normalizing element. The results showed that the most of the elements (Ba, Co, Cs, Cu, Fe, Li, Mn, Ni, Rb, Ti, U, V, and Zn) are conservative, with average EF close to unity. Lithium, mollybdenum and uranium were enriched in the sediments with average values of EF between 2 and 10. The highest average EF determined in the study were for the following elements: As, Ca, Cd, and Hg. The average concentrations of potentially toxic elements in the sediments from the Mapachitos vents were 60 mg kg-1 for As, and 21849 µg kg-1 for Hg. The surface sediments of the adjacent area, however, have low average concentrations for As and Hg: 3.7 mg kg-1 and 52 µg kg-1, respectively. Other elements such as Cd (0.9 mg kg-1) and Ca (28.3%) are highly enriched in the sediments of the study area, comparing to their average crustal abundances. The results of Principal Component Analysis allowed to determine three factors which explain 91% of data variance, as well as to differentiate four associations including terrigenous elements, calcareous components, elements of the hydrothermal origin and redox-sensitive elements in the surface sediments off the Mapachitos in the north-western portion of bahia Concepcion. Furthermore, the results confirmed the influence of the hydrothermal inputs of some trace elements on the sediments of the area surrounding the vents, in particular As and Hg, and to a lesser extent Al, Fe, and Mn at the venting site.

El objetivo de este estudio fue determinar la influencia de las ventilas hidrotermales someras en Mapachitos, Bahía Concepción, en la composición de los sedimentos superficiales del área circundante de esta bahía. Los siguientes elementos Al, As, Ba, Ca, Cd, Co, Cs, Cu, Fe, Hg, Li, Mn, Mo, Ni, Rb, S, Ti, U, V, Zn, Corg y Cinorg fueron determinados en muestras de sedimentos. Los valores de CaCO3 calculado en los sedimentos dentro de algunospuntos del área de estudio son tan altos como 90% (con un promedio de 61%). La concentración de carbono orgánico en los sedimentosfue aproximadamente 1%. Los contenidos totales de los elementos fueron comparados con las abundanciaspromediospara la corteza continental, y los factores de enriquecimiento (EF) fueron calculados usando Al como elemento normalizador. Los resultados demostraron que la mayoría de los elementos (Ba, Co, Cs, Cu, Fe, Li, Mn, Ni, Rb, Ti, U, V, y Zn) son conservativos, con promedios de EF cercanos a la unidad. El litio, el molibdeno y el uranio fueron enriquecidos en los sedimentos con valorespromedios EF entre 2y 10. Los mayorespromedios de EF en el estudio fueron para los siguientes elementos: As, Ca, Cd y Hg. Las concentraciones promedio de elementos potencialmente toxicos en los sedimentos de las ventilas en Mapachitos, fueron 60 mg kg-1 para As y 21849 µg kg-1 para Hg. Los sedimentos superficiales del área adyacente, sin embargo, tienen bajas concentraciones promedios para As y Hg: 3.7 mg kg-1 y 52 µg kg-1, respectivamente. Otros elementos tales como Cd (0.1 mg kg-1) y Ca (64%) son altamente enriquecidos en los sedimentos del área de estudio, comparando sus abundancias promedios con los de la corteza. Los resultados del análisis de Componentes Principales permitieron identificar tres factores los cuales explican el 91% de la varianza de los datos, asi como también diferenciar algunas asociaciones incluyendo elementos terrígenos, componentes calcáreos, elementos de origen hidrotermal y elementos de reducción -oxidación sensibles en los sedimentos superficiales frente a Mapachitos en la porción noroeste de la bahía Concepción. Además, los resultados confirman la influencia de las agregaciones hidrotermales de algunos elementos traza en el área circundante a las ventilas, en particular, As y Hg, y en grado menor Al, Fe y Mn en el sitio de las ventilas.

Nickel and vanadium were tested as tracers of oil refinery emission distribution in populated area of Rio Grande-RS. The anomalies of these elements in surface soil are considered a long-term reflection of the emissions in low atmosphere. The spatial distribution of Ni and V in the soil corresponded to the pattern of local winds. The threshold of 1.5 backgrounds of these metals markedly outlined the area of petrochemical emissions. Anomalies of Ni and V in surface soil have a rather different configuration in comparison with other metal tracers of urban impact: Cd, Cu, Pb and Zn.

Land reclamation fills in the city of Rio Grande (RS) are polluted by mercury with concentrations ranging from 0.3 to 18.7 mg kg-1. The level of Hg pollution decreases from the oldest landfills of 18th century to recent ones. Mercury distribution along vertical profiles resembles the same for copper, lead, and zinc, what allow supposing that mercury distribution has an autochthonous character. It is suggested that the principal source of mercury pollution was the activities related to animal skin and fair hair treatment, using ancient technology known as "carroting". Similar scenario of environmental risk could be met in other Brazilian cities with similar colonization history.

The employment of local soils for extraction of metallic elements was evaluated through batch tests to treat wastewaters generated in a petroleum refinery plant in southern Brazil. Clay and organic carbon content and clay mineralogy provide these soils, in principle, with moderate metal retention capacity. The following retention order was established: Cr3+ > Pb2+ > Cu2+ > Hg2+ > Cd2+, with total amount of metals retained varying from 36 to 65 meq kg-1. The results show the high efficiency of local soils for extracting metals from liquid effluents through sorption and precipitation processes under acid pH conditions.

The alteration in the quality of groundwater in the industrial zone of Brazil's southernmost state was assessed by a hydrogeochemical study. In 70-85% of the studied area, fluoride, nitrate and phosphate in groundwater surpass the maximum limits for human consumption according to Brazilian environmental legislation. The chemical spectrum of contaminants and their spatial distribution show that fertilizer production processes are responsible for groundwater pollution. The natural conditions of the region are not favorable for minimal protection against infiltration of pollutants into the aquifer.

High lead concentrations up to 5478 mg kg-1 were detected in dry atmospheric precipitations in Rio Grande city and adjacent area. Lead anomalies cover up to 30% of the study area. Lead concentration measurement in dry atmospheric precipitation and suspended particulate matter provides a possibility to detect concentrations above lead threshold in the air. The most impacted areas are fishermen's villages. The most possible source of lead in the air is uncontrolled sub industrial activity of local population

Fluoride concentration was determined in rainwater, ground water and soil in the zone of fertilizer industry in the city of Rio Grande. In contaminated rainwater fluorine concentration was registered up to the value of 4,4 mg.L-1. Fluorine concentration in the shallow ground water in general reflects its distribution in the atmosphere, but cannot be used as marker of atmosphere contamination in the urban area due to dissolving influence of residential effluents. The 0,01% HCl extracts from the set of surface soil samples demonstrates fluoride distribution in the zone of influence of industrial emissions, which coincides to the numerical simulation of fluorides dispersion in the air.

The current article presents the first data on physical-chemical parameters of wet precipitation collected at single collection point in the city of Rio Grande, during the period of 12 months in 1997-1998. The employed technique of rainwater separation into several portions made clear the process of the atmosphere self-purification during a precipitation event. The pH of rainwater depends on the extent of industrial emissions and increases during a precipitation event. The first portion of rainwater shows an obvious neutralizing effect of soil and ocean-derived components, whose intensity depends on the duration of the preceding dry period.