Mercury distributions in sediments of an estuary subject to anthropogenic hydrodynamic alterations (Patos Estuary, Southern Brazil).

The city of Rio Grande, located on the right bank of the Patos Estuary, has been severely contaminated by mercury (Hg) due to anthropogenic activities that chiefly began in the eighteenth century. To investigate the natural mercury distribution along the salinity gradient in the estuary, three sediment cores were collected from a region of the estuary that has experienced less anthropogenic impacts, namely its left bank. Our study demonstrates that accumulation of Hg and formation of metal sulfide minerals take place in fine grain sediment horizons within the sampled sediment cores. Mercury immobilization in these sediments occurs via binding to organic matter coatings on fine grain sediment particles, as well as by incorporation into and/or co-precipitation with iron sulfide minerals. The grain size controls over Hg accumulation and sulfide mineral formation were statistically demonstrated using principal component analysis. Different fine particulate sediment deposition patterns occurred at each sampling location, which is attributed to the consequence of hydrological changes in the estuary resulting from navigation infrastructure reforms performed over the past 200 years in the local port (e.g., dredging) and its surroundings. We suggest that the port building and maintenance activities have influenced Hg distributions in the estuarine sediments.

Selenium Enrichment in Pore Water of Estuarine Sediments Subject to Salt Marsh Vegetation Bioirrigation (Patos Estuary, Southern Brazil).

Selenium (Se), iron (Fe), and free sulfides contents in pore waters were measured to study the liberation of soluble Se in suboxic conditions. The sediment core was collected in a salt marsh in Patos Lagoon estuary (southern Brazil), and it was obtained during a brackish water period, in a low intertidal stand vegetated by Spartina alterniflora. The redox potential (Eh), pH, andacid volatile sulfides (AVS) content were also investigated. Pore water results sustained the idea that S. alterniflora roots promote oxygen penetration to depths of ca. 10 cm below the salt marsh surface, increasing Eh and lowering the pH in this interval. High Se concentrations (e.g., 16.9 µg L-1), that are above US. EPA environmental criteria, were observed in the pore water to depths between 10 and 20 cm and are associated to low AVS contents and high concentrations of free sulfides. In the first 10 cm the lowering of Se contents probably happens due the low pH and biological volatilization of the metalloid.

Distribution of potentially harmful elements in soils around a large coal-fired power plant.

An understanding of the spatial distribution and contribution of a power plant to local soil contamination is important for the planning of soil use and prioritizing remedial actions for public safety. Consequently, the aim of this study was to map the spatial distribution of potentially hazardous elements (PHEs; Cu, Pb, Zn, Ni, Cr, Fe, Mn, Cd, As, and Se) in soils around a large (796 MW) coal-fired power plant in Brazil. For the purpose, 33 soil samples were collected in the area within a radius of approximately 17.5 km from the plant and subsequently analyzed for PHEs. The frequency and direction of winds were also obtained from a meteorological station in the region. The sampling area was divided into four quadrants (northwest: N-NW; northeast: N-NE; southeast: S-SE; southwest: S-SW), and there were significant negative correlations between the distance and the concentrations of Se in the S-SE quadrant and As in the S-SW and S-SE quadrants. There were positive correlations between distance from the plant and the concentration of Mn in the N-NE quadrant and the concentration of Cd in the S-SW quadrant. The dominant direction of the winds was N-NE. The indexes used in this study showed low-to-moderate enrichment factor, but detailed analysis of the dominant quadrant of the winds showed a correlation with higher concentrations in the soils closer to the power plant for at least seven of the PHEs analyzed, especially with regard to As. Therefore, we conclude that the distribution of the metalloid As can be used as a marker of the spatial distribution of contamination from the thermoelectric plant, but the dynamics of the other elements suggests that the presence of other sources of contamination may also compromise the quality of local soils.

Record of Hg pollution around outset of colonization in Southern Brazil.

This study presents results of a sediment core located in Coroa de Boi Bay, a not dredged cove within Patos Estuary, Southern Brazil. The distribution of metals (Hg, Cu, Pb) and U in the sediment profile records several contamination events since pre-colonial times to present days. A joint assessment of the distribution of these parameters and the consultation to historical documents allowed us to establish causal links between concentrations anomalies in the sediments and ancient anthropogenic contamination in the area. During the industrial period, sedimentation rates in the bay ranged from 3.4 to 5.5 mm year-1. Applying a sedimentation rate previously calculated for undisturbed sediments in the Patos Estuary, we trace the beginning of Hg contamination as having started in the colonial period in Southern Brazil, soon after a Hispanic-Lusitanian conflict situation in South America. The most probable source of Hg contamination during this period was carroting technology used in fur processing.

Human health risk assessment of metals in soil samples of a Brazilian city with a historic contamination complex.

Rio Grande is a city located on a narrow industrialized and urbanized Brazilian peninsula, characterized by wetlands. Due to population growth, numerous urban backfilled regions were built to expand the territorial area of the city. Currently, more than 60% of the central area of the city comes from the grounding of wetlands. The material used for the expansion of the territory had a history of contamination from metals from the tannery and textile industries (mainly Hg) and urban solid waste. In addition to past sources, the city has an active industrial complex with fertilizer, petrochemical, and grain industries. This study evaluated the risks to human health caused by metals (Hg, Fe, Ni, Cr, Cu, Pb, and Zn) in original soils and backfills, considering the oral, inhalation, and dermal routes of exposure for children and adults using the tool human health risk assessment (HHRA) proposed methodology by USEPA. A total of 63.81% of the original soil samples and 57.14% of the backfill soil samples showed a non-carcinogenic risk (HInc>1) for at least one evaluated metal. Still, approximately 10% of the samples presented carcinogenic risk when the Cr was considered in the hexavalent form. The dermal (Hg, Ni, and Cr) and oral (Fe, Cu, and Zn) exposure routes had the greatest contribution to the total risk. The non-carcinogenic risk for Hg, Cr(VI), and Pb was heterogeneously distributed between the original soils and backfills and associated with the proximity to some pollution sources. Given the complexity of historical occupation in the municipality and the increasing industrialization, both the original areas and the backfills should be included in the risk management strategy to minimize risks.

Selenium Content in Freshwater and Marine Fish from Southern Brazil Coastal Plain: a Comparative Analysis on Environmental and Dietary Aspects.

The coastal plain of Rio Grande do Sul is considered to be a Se-deficient region in terms of its population dietary habit, making it the focus of this study. Selenium dietary deficiency is a concern when we consider its potential critical health effects on the local population. Therefore, this study contributes new information on the levels of Se in several species of marine and freshwater fish in the region of the Patos-Mirim Lagoon system, coupled with a comparative analysis of the metalloid contents between both fish groups. The Se contents in the fish species ranged from 88 ± 13 to 688 ± 19 µg.kg-1. The average Se concentration in the muscle tissue of the freshwater species (251 ± 96 µg kg-1) was significantly lower than that of the marine species (412 ± 143 µg kg-1). Likewise, no evidence of Se biomagnification was found among the fish from both the marine and freshwater environments, suggesting the absence of trophic transfer of Se. We note that to ensure that the RDA (Recommended Daily Allowance, 55 µg day-1) of Se dietary intake for adults is met, at least 134 g of freshwater or 82 g of marine fish fillet could be incorporated into the diet of the population of Rio Grande do Sul. According to target hazard quotients (THQ) and the permissible safety limits, consumption of the fish species analyzed is safe for human health.

Health effects of ingestion of mercury-polluted urban soil: an animal experiment.

Rio Grande, the southernmost Brazilian port and industrial center, is marked by mercury-polluted ground cover. This pollution varies spatially, with levels exceeding 1,000 µg kg(-1) in 30% of the urban territory. The risk of Hg impact as a result of deliberate and involuntary geophagy is increased by restrained urban conditions in combination with the large proportion of the population living at low-income levels. Laboratory tests have demonstrated that ingestion of Hg-polluted soil by rats results in significant alterations in animal health such as stagnation in body weight increase, and significant mercury accumulation in the liver and kidney. The consumption of Hg-contaminated urban soil also provoked changes in hematological profiles of experimental animals by increasing the number of platelets. The present study indicates the potential for the local population of Rio Grande living in mercury-polluted districts, specifically young children, to experience health disturbances.

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.

Assessment of polycyclic aromatic hydrocarbon influx and sediment contamination in an urbanized estuary.

Sediments from the Patos Lagoon Estuary in Southern Brazil and sludge from incoming effluents were assessed for the distribution of polycyclic aromatic hydrocarbons (PAHs). Shallow sediments adjoining the City of Rio Grande were found to be contaminated by PAHs mainly near urban effluent discharge, as well as in the port area. Effluents clustered into four groups according to their sources (sewage, industrial, runoff, and mixed), with each demonstrating different contributions of PAHs to the estuary. There was a predominance of runoff and mixed sources. Navigation activity was the second most important source of PAHs to sediments. The PAHs ratio identified the origin of these contaminants as essentially pyrolytic. The impact of PAHs as a result of uncontrolled disposal or accidental discharge of PAH-rich residues was suggested for several points. These points were primarily near gas stations and motor workshops. In about 30% of sampled sediments, the concentration of benzo[a]pyrene surpassed the Threshold Effects Level adopted for marine environments.

Arsenic and mercury contamination of sediments of geothermal springs, mangrove lagoon and the Santispac bight, Bahía Concepción, Baja California peninsula.

In order to find out the environmental impact on the coastal zone, the composition of sediments of the intertidal geothermal hot spring zone and adjacent area of Playa Santispac in the pristine Bahía Concepción (Baja California peninsula) was studied. High concentrations of As (13-111 mg kg⁻¹) and Hg (0.55-25.2 mg kg⁻¹) were found in the sediments of the geothermal sources. Arsenic and Hg concentrations decrease rapidly in the adjacent small mangrove lagoon sediments and reach background levels (0.7-2.6 mg kg⁻¹ and 6-60 µg kg⁻¹ respectively) in the marine sediments collected in front of Playa Santispac.

Urban activity and mercury contamination in estuarine and marine sediments (Southern Brazil).

The distribution of mercury in sediments of the Patos Lagoon estuary and nearby coastal marine deposits has been investigated for the period 1998-2008. Polluted urban soils and coastal reclamation fills are the principal sources of high mercury concentrations for shallow estuarine sediments. The shallow sediments that form near the urban area enter the navigation canal and are transported into the ocean. The mercury concentration in sediments of the navigation canal has considerably increased since 2004, due to intense reconstruction activity in the urban area. Periodic dredging of the canal strengthens the preconditions for coastal marine sediment contamination by mercury. However, this does not occur because the resuspended dredged sediments are significantly diluted by natural suspended particulate matter.

Copper bioavailability and fractionation in copper-contaminated sandy soils in the wet subtropics (southern Brazil).

We studied the distribution, bioavailability and speciation of copper in subtropical sandy soils exposed to long-term applications of copper-based fungicide. In the surface horizon of the contaminated soils, bioavailable copper surpasses the toxic threshold for plants up to several times. Mobile fractions of copper predominate in top layers, contributing to contamination spreading downward to groundwater. Copper accumulates on the underlying iron hydroxide barrier in quantities comparable to total copper concentrations in the surface horizon. Despite the impediment of the geochemical barrier, most applied copper reaches the aquifer, contaminating the groundwater.

Mercury dispersal to arroyo and coastal sediments from abandoned copper mine operations, el Boléo, Baja California.

Evidence for mercury dispersal in an arid coastal region of central Baja California (Mexico) suggests that abandoned copper mining operations are a noticeable source of mercury in the environment. There is a generally elevated level of mercury in alluvium of arroyos throughout the mining district (0.14-0.18 mg kg(-1)). In the first several dozen meters surrounding two of the biggest mines, mercury levels range from 0.26 to 3.16 mg kg(-1), forming a halo of anomalously high concentrations. The coastal marine sediments, particularly those close to the copper smelter in the town of Santa Rosalía, also display some mercury enrichment.

Arsenic enrichment in sediments and beaches of Brazilian coastal waters: A review.

High concentrations of total arsenic (As), even above the Brazilian legislative threshold for marine sediments of 70 mg kg-1, were found in beach sands and near-shore surface sediments. Two mechanisms (anthropogenic activities and sedimentary processes in the coastal waters) are responsible for this contamination. The anthropogenic impact includes releases from metallurgical plants, phosphate fertilizer plants and gold and iron mining. In the coastal area sedimentary processes redistributed the As from the sediment into the porous structure of calcareous marine algae. These enriched calcareous algae are transported over time to the beach by wave action. As in the Brazilian coastal environment, increased As levels were also observed in other coastal environments of South America such as Rio Loa (Chile), Barbacoas Bay (Colombia) and the Southern Pampa region (Argentina). Finally, arsenic levels in fish from Brazilian coastal waters and North Sea, which is also an As-contaminated area, were compared. In both areas, short term health effects from fish consumption are not expected, but a lifetime cancer risk cannot be excluded.

Arsenic speciation in fish and shellfish from the North Sea (Southern bight) and Açu Port area (Brazil) and health risks related to seafood consumption.

In North Sea and Port Açu (Brazil) coastal areas, high arsenic (As) concentrations were observed in water, soil and sediments. Therefore, the impact of this contamination on fish and shellfish species bought from local fishermen was studied. Total As was assessed with ICP-OES (Brazil) and ICP-MS (North Sea) after microwave digestion. Toxic As was assessed with liquid chromatography-ICP-MS (Brazil) and hydride generation-atomic fluorescence spectrometry (North Sea). All analytical methods comply with Quality Assurance/Quality Control procedures. Several fish species have average Total As concentrations above 1 µg g-1 wet weight (ww), but the highest concentrations are found in less spotted dogfish, lemon sole and whelks from the North Sea, with respectively 50, 49 and 50 µg g-1 ww. High Total As concentrations correspond to high Toxic As concentrations, except for scallops having increased Toxic As concentrations. Toxic As fractions are highest in scallops (almost 10%) but rarely exceeds 2% in all other species. Liver samples were only analyzed in ray, dogfish and catfish and their Toxic As fractions are between 2 and 4 times higher than in muscle. For a consumption of 150 g of seafood, only 3 samples exceed the provisional total daily intake of 2 µg kg-1 bw, however, cancer risks are non-negligible. Using mean Toxic As concentrations for each of the different fish and shellfish species studied, Lifetime Cancer Risk values at the actual global seafood consumption rate of 54 g day-1 are above 10-4 for whelks, scallops, dogfish, ray and lemon sole.

Intertidal geothermal hot springs as a source of trace elements to the coastal zone: A case study from Bahía Concepción, Gulf of California.

We investigated the influence of the intertidal geothermal hot spring (GHS) on the biogeochemistry of trace elements in Santispac Bight, Bahía Concepción (Gulf of California). The geothermal fluids were enriched in As and Hg mainly in ionic form. The suspended particulate matter of the GHS had elevated enrichment factor (EF) >1 of As, Bi, Cd, Co, Cu, Mn, Mo, Sb, Sn, Sr, Ti, U and Zn. The sediment core from GHS1 had high concentration of As, Hg, Corg, S, V, Mo, and U and the extremely high EF of these elements at 8cm of the core. The maximum bioaccumulation of As and Hg was in seaweeds Sargassum sinicola collected near the GHS2. The results confirm the input of trace elements to the coastal zone in Bahía Concepción from geothermal fluids and the evident modification of the chemical composition of the adjacent marine environment.

Metal contamination of vineyard soils in wet subtropics (southern Brazil).

The vine-growing areas in Brazil are the dampest in the world. Copper maximum value registered in this study was as much as 3200 mg kg(-1), which is several times higher than reported for vineyard soils in temperate climates. Other pesticide-derived metals accumulate in the topsoil layer, surpassing in the old vineyards the background value several times for Zn, Pb, Cr and Cd. Copper is transported to deeper soils' horizons and can potentially contaminate groundwater. The soils from basaltic volcanic rocks reveal the highest values of Cu extracted with CaCl(2), demonstrating a high capacity of copper transference into plants. When evaluating the risks of copper's toxic effects in subtropics, the soils from rhyolitic volcanic rocks are more worrisome, as the Cu extracted with ammonium acetate 1M surpasses the toxic threshold as much as 4-6 times.

The effect of emissions of fertilizer production on the environment contamination by cadmium and arsenic in southern Brazil.

The distribution of cadmium and arsenic in rainwater, surface soil and groundwater in a zone of influence of emissions of a phosphate fertilizer factory has been investigated. The analysis of rainwater along a wind line shows that cadmium in the soluble form precipitates close to emission source, whereas arsenic migrates further and also in the soluble form precipitates at a greater distance. The pH controls the distribution of cadmium and arsenic in rain and groundwater. Concentration of soluble cadmium along the impact line increases with reduction of pH and arsenic, contrary to the increase of pH. Concentrations of cadmium and arsenic in surface soil correlate well among themselves near to emission point. In a zone of confluence of emissions with sea air at a distance from the factory there is sedimentation of arsenic on a geochemical barrier and formation of a separate anomaly in soil.

Mercury pollution sources in sediments of Patos Lagoon Estuary, Southern Brazil.

Present study has continued the investigation on distribution of mercury in estuarine sediments of Patos Lagoon which began whilst assessing the after-effect of enormous accidental discharge of sulfuric acid into the estuary. An attempt to evaluate the contribution of anthropogenic effluents on mercury pollution in sediments was undertaken. The effluents from Rio Grande City sewages were categorized into four groups based on their sources. Comparison of mercury concentrations from those, indicated that domestic effluent was prevalent. Apparent geographic controls of effluent locations enriched in mercury on zones of polluted estuarine sediments were also revealed. Insufficient control on waste collecting and absence of sewage treatment are considered the principal causes of mercury pollution in estuarine sediments.