Freshwater shrimps (Macrobrachium depressimanum and Macrobrachium jelskii) as biomonitors of Hg availability in the Madeira River Basin, Western Amazon.

Total mercury (THg) concentrations measured in two freshwater shrimp species (Macrobrachium depressimanum and Macrobrachium jelskii) showed a relationship with the location of artisanal and small-scale gold mining (ASGM) from the Madeira River Basin, Western Amazon. Between August 2009 and May 2010, 212 shrimp samples were collected in the confluence of the Madeira River with three of its tributaries (Western Amazon). THg concentration was quantified in the exoskeleton, hepatopancreas and muscle tissue of the shrimps by cold vapor atomic absorption spectrophotometry. There were no significant differences between the two shrimp species when samples came from the Madeira River, but Hg concentrations were significantly lower in a tributary outside the influence of the gold mining area. Average THg concentrations were higher in the hepatopancreas (up to 160.0 ng g-1) and lower in the exoskeleton and muscle tissue (10.0-35.0 ng g-1 and < 0.9-42.0 ng g-1, respectively). Freshwater shrimps from the Madeira River respond to local environmental levels of Hg and can be considered as biomonitors for environmental Hg at this spatial scale. These organisms are important for moving Hg up food webs including those that harbor economic significant fish species and thus enhancing human exposure.

Mercury Concentrations in Tuna (Thunnus albacares and Thunnus obesus) from the Brazilian Equatorial Atlantic Ocean.

Average total Hg concentrations measured in muscle of two species of tuna (Thunnus obesus and T. albacares) captured in the Brazilian Equatorial Atlantic Ocean varied from 95 to 1748 ng.g-1 wet weight in T. obesus and 48 to 500 ng.g-1 wet weight in T. albacares. Higher concentrations in T. obesus are probably related to foraging on deep water carnivorous fish. Smaller individuals of both species showed the lowest concentrations, but a significant positive relationship between fish weight and length and Hg concentrations was found for T. obesus, but not for T. albacares. Largest individuals (>30 kg) of T. obesus showed Hg concentrations ≥1000 ng.g-1, surpassing the legal limits for human consumption, although the average concentration for this species was much lower (545 ng.g-1). Concentrations in T. albacares from the Brazilian Equatorial were lower than those found in the African and in the North Atlantic. No comparison could be made for T. obesus due to few studies for this species in the Atlantic Ocean.

Long-Term (2002-2015) Changes in Mercury Contamination in NE Brazil Depicted by the Mangrove Oyster Crassostraea rhizophorae (Guilding, 1828).

Mercury concentrations in oysters from four estuaries in northeastern Brazil varied following source changes during the past 13 years. Concentrations were higher in urban estuaries relative to rural areas, but decreased in the 13-years interval following improvements in solid wastes disposal and sewage treatment. In rural estuaries, the one located in an environmental protection area showed no changes in Hg concentrations in the period. However, in the Jaguaribe estuary, remobilization from soils and sediments due to regional environmental changes, increased Hg concentrations in oysters to values similar to the most contaminated metropolitan sites.

Mercury in indigenous, introduced and farmed fish from the semiarid region of the Jaguaribe river Basin, NE Brazil.

Indigenous, introduced and farmed fish species were collected from the Jaguaribe Basin, NE Brazil to assess total and methyl mercury concentrations in muscle tissue and to determine its relationship with fish origin. The results obtained from introduced species were compared to the Hg content of their original area of occurrence, which is located in the Amazon region. Farmed and wild individuals of Oreochromis niloticus (tilapia) were also compared. Introduced species presented lower Hg contents compared to their Amazonian counterparts. Wild individuals of O. niloticus also presented higher Hg contents than farmed individuals with similar sizes. However, methyl Hg concentrations were not significantly different between the two groups. Total Hg and methyl Hg concentrations were higher in carnivorous species, especially those from the Amazon region, and surpassed the Brazilian guidelines for fish consumption. Based on their Hg content, Jaguaribe basin fish do not pose a significant threat to human consumption.

Metals in water, sediments, and biota of an offshore oil exploration area in the Potiguar Basin, Northeastern Brazil.

Metal concentrations were evaluated in water, bottom sediments, and biota in four field campaigns from 2002 to 2004 in the Potiguar Basin, northeastern Brazil, where offshore oil exploration occurs. Analyses were performed by inductively coupled plasma mass spectrometry and inductively coupled plasma optical emission spectrometry. Total metal concentrations in water (dissolved + particulate) and sediments were in the range expected for coastal and oceanic areas. Abnormally high concentrations in waters were only found for Ba (80 µg l(-1)) and Mn (12 µg l(-1)) at the releasing point of one of the outfalls, and for the other metals, concentrations in water were found in stations closer to shore, suggesting continental inputs. In bottom sediments, only Fe and Mn showed abnormal concentrations closer to the effluent releasing point. Metal spatial distribution in shelf sediments showed the influence of the silt-clay fraction distribution, with deeper stations at the edge of the continental shelf, which are much richer in silt-clay fraction showing higher concentrations than shallower sediments typically dominated by carbonates. Metal concentrations in estuarine (mollusks and crustaceans) and marine (fish) organisms showed highest concentrations in oysters (Crassostrea rhizophorae). Fish tissues metal concentrations were similar between the continental shelf influenced by the oil exploration area and a control site. The results were within the range of concentrations reported for pristine environments without metals contamination. The global results suggest small, if any, alteration in metal concentrations due to the oil exploration activity in the Potiguar Basin. For monitoring purposes, the continental inputs and the distribution of the clay-silt fraction need to be taken into consideration for interpreting environmental monitoring results.

Mercury distribution in a mangrove tidal creek affected by intensive shrimp farming.

In this study, the Hg distributions in water and sediments from a mangrove creek that receives intensive shrimp farming effluents were determined. The average dissolved and particulate Hg concentrations in the water varied from 3.1 to 9.2 ng L(-1) and from 4.4 to 9.4 ng L(-1), respectively. However, the Hg concentrations in the suspended particulate matter and the bottom sediments varied from 95.4 to 115.7 ng g(-1) and from 1.6 to 10.3 ng g(-1), respectively. A Ward quadratic distance cluster analysis based on the Hg concentrations and hydro- and geochemical parameters (oxygen, salinity, temperature, pH, and organic matter and aluminum content) showed the effects of shrimp farming effluents on the Hg distribution pattern. Furthermore, these results were supported by the Hg distribution in the sediment cores. This study emphasizes the necessity of including Hg as a potential pollutant when monitoring the environmental impacts of intensive shrimp farming.

Mercury emission factors from intensive shrimp aquaculture and their relative importance to the Jaguaribe River Estuary, NE Brazil.

This study estimated Hg emission factors (EFs) and total Hg loading to the Jaguaribe Estuary, NE Brazil, from intensive shrimp farming, and compares this with other local anthropogenic activities. The EF reached 83.5 mg ha(-1) cycle(-1) (about 175 mg ha(-1) year(-1)), resulting in an annual Hg load to the estuary of 0.35 kg. The calculated EF is comparable to Hg EFs from urban wastewaters (200 mg ha(-1)) and solid waste disposal (400 mg ha(-1) year(-1)) from cities located in the estuary's basin. However, due to the smaller area of aquaculture (2,010 ha), total annual loads are much lower than from these other sources (75 and 150 kg year(-1), respectively). Since shrimp farming effluents are released directly into the estuary, the estimated high EF raises environmental concerns with this expanding industry, suggesting the inclusion of this element in ongoing environmental monitoring programs.

Tracing of dissolved organic matter from the Sepetiba Bay (Brazil) by PARAFAC analysis of total luminescence matrices.

Fluorescent excitation-emission matrices (FEEM) of the fluorescent dissolved organic matter (FDOM) are widely used for DOM characterization and tracing. In this work, a set of FEEM from sampling campaigns in the Sepetiba Bay (Brazil) was decomposed into independent components using the parallel factor analysis (PARAFAC) algorithm. Four independent components were extracted describing the total fluorescence of the FDOM. The well described peaks A, C, M, B and T were found, and a new peak, A', linked to the C peak, was detected. Relative contribution of each of four components to the total fluorescence confirms that the coastal water has DOM of terrestrial origin, except for the 275Ex/400-500Em range (nm), which primarily occurs in marine waters.

Total-Hg and organic-Hg in Cephalopholis fulva (Linnaeus, 1758) from inshore and offshore waters of NE Brazil.

To investigate whether source proximity or bioavailability is the major factor controlling both Hg concentration and Hg speciation in marine fishes, total- and organic-Hg content in muscle and liver tissues from different populations of Cephalopholis fulva (piraúna) from inshore and offshore waters of the Brazilian northeastern coast were analyzed. Average total-Hg in muscle (104 ng x g(-1) w.w.) and liver (2,865 ng x g(-1) w.w.) tissues, as well as organic-Hg concentrations in muscle (169 ng x g(-1) w.w.) and liver (1,038 ng x g(-1) w.w.), were much higher in the offshore population of C. fulva than in the inshore ones. In the inshore population total-Hg and organic-Hg average concentrations in muscle tissue were similar and reached only 49 ng x g(-1) w.w., while in liver they reached 412 ng x g(-1) w.w. for total-Hg and 180 ng x g(-1) w.w., for organic-Hg. Concentrations of both Hg species in the two populations were higher in liver than in muscle. The average percentage contribution of organic-Hg to the total Hg content was higher in muscle (98-100%) than in liver (42-53%), but similar between the two populations. Total-Hg and organic-Hg concentrations in muscle and liver from the offshore population showed significant (P < 0.05) positive correlation with fish length. However, in the inshore population only the total-Hg and organic-Hg in muscle tissues correlate significantly with fish size. Although the coastal environments are enriched in total Hg relative to open waters, the significant higher Hg concentrations in the offshore population of C. fulva and the significant correlation found between organic-Hg in liver with fish size suggest higher bioavailability of Hg in offshore waters relative to inshore ones.

Dial organic carbon fluctuations in a mangrove tidal creek in Sepetiba bay, Southeast Brazil.

The carbon (C) concentration and flux, as dissolved organic carbon (DOC), particulate organic carbon (POC) and macrodetritus (MD), were quantified through 4 tidal cycles in a mangrove tidal creek in Southeastern Brazil. DOC was the major fraction of the total C concentration, accounting for 68 and 61% of the total C concentration during ebb and flood periods respectively. Concentrations of DOC (Ebb = 3.41 +/- 0.57 mgC.L-1 and Flood = 3.55 +/- 0.76 mgC.L-1) and POC (Ebb = 1.73 +/- 0.99 mgC.L-1 and Flood = 1.28 +/- 0.45 mgC.L-1) were relatively similar during the four tidal cycles. Macrodetritus presented a wide variation with concentration peaks probably related to external forces, such as winds, which enrich the ebb flow with leaf litter. DOC and POC fluxes depended primarily on tidal and net water fluxes, whereas MD fluxes were not. The magnitude of the DOC and POC fluxes varied with the area flooded at high tide, but not the MD fluxes. DOC was the major form of carbon export to Sepetiba Bay. During the four tidal cycles, the forest exported a total of 1.2 kg of organic carbon per ha, mostly as DOC (60%), followed by POC (22%) and MD (18%).

Mercury contents in aquatic macrophytes from two reservoirs in the Paraíba do Sul: Guandú river system, SE Brazil.

This paper reports on a study to determine the Hg content in the five most abundant aquatic macrophyte species (Elodea densa, Sagittaria montevidensis, Salvinia auriculata, Pistia stratiotes and Eichhornia crassipes) in two artificial reservoirs flooded by water diverted from the Paraíba do Sul river, SE Brazil. The potential of these species for Hg accumulation and their role in Hg transport along the river system due to macrophyte management were evaluated. Mercury concentrations were higher in free-floating than in rooted species. Roots were also richer in Hg than were leaves. Dry weight Hg concentrations in leaves and roots from all species varied from 46-246 ng.g(-1) to 37-314 ng.g(-1), respectively. These values are higher than those reported for uncontaminated lakes in Brazil and in other tropical areas and similar to those reported for moderately contaminated sites. Mercury concentrations can be attributed to fluvial transport from the heavily industrialized Paraíba do Sul river basin. Intensive sampling of Pistia stratiotes from two sites in the Vigário reservoir was performed to evaluate the capacity of Hg incorporation in short periods of time. The results showed a significant negative correlation between Hg content and size class of individual plants, demonstrating the importance of juveniles, fast growing plants in absorbing Hg. The foremost impact related to Hg contents in the studied area concerns the periodic removal of macrophytes for reservoir management, followed by disposal in nearby areas. This results in the mobilization of 0.52 to 1.3 Kg of Hg per year, a significant fraction of the Hg burden present in reservoir waters. Disposal of such material may result in Hg leaching to river systems, affecting the Hg transfer throughout the basin.

Food preferences and Hg distribution in Chelonia mydas assessed by stable isotopes.

Mercury (Hg) is a highly toxic pollutant that poses in risk several marine animals, including green turtles (Chelonia mydas). Green turtles are globally endangered sea turtle species that occurs in Brazilian coastal waters as a number of life stage classes (i.e., foraging juveniles and nesting adults). We assessed total Hg concentrations and isotopic signatures ((13)C and (15)N) in muscle, kidney, liver and scute of juvenile green turtles and their food items from two foraging grounds with different urban and industrial development. We found similar food preferences in specimens from both areas but variable Hg levels in tissues reflecting the influence of local Hg backgrounds in food items. Some juvenile green turtles from the highly industrialized foraging ground presented liver Hg levels among the highest ever reported for this species. Our results suggest that juvenile foraging green turtles are exposed to Hg burdens from locally anthropogenic activities in coastal areas.

Mercury, zinc, and copper accumulation in mangrove sediments surrounding a large landfill in southeast Brazil.

The accumulation of Hg, Zn, and Cu was evaluated in mangrove sediments located between a large, 20-years-old landfill and waters of Guanabara Bay (southeast Brazil). The contamination history of the area provides substantial evidence that metal accumulation in the study site is influenced by past metal emissions from multiple sources (e.g. contaminated rivers and the landfill surrounding the site). At the southern part of the site, metal levels are up to 890 ng g(-1) Hg, 850 microg g(-1) Zn, and 58 microg g(-1) Cu. Enrichment factors and excess (background-deducted) concentration inventories show a high spatial variability of metal contamination and storage in the site, with differences often by a factor higher than two within a sampling station and higher than five between sampling stations. These contrasts are attributable to a coupling between spatial variability of anthropogenic metal input and metal behavior and retention within the sediments. Results indicate that during the last few decades mangrove sediments retained a substantial part of metal emissions to the site, probably reducing the metal transport to Guanabara Bay waters, and suggest the suitability of mangrove ecosystems as physical and biogeochemical barriers to metal contaminant transport.

Mercury concentrations in inland waters of gold-mining areas in Rondônia, Brazil.

Total mercury concentrations in water, sediments and fish from the gold-mining areas of Brazil, especially the Amazon region, are presented. Mercury concentrations were variable among rivers, with the highest values found in samples from tributary forest rivers. Concentrations in water samples varied between 0.1 and 8.6 micrograms l-1, while in bottom sediments they reached 19,800 micrograms kg-1. Concentrations in edible parts of locally consumed fish reached up to 2700 micrograms kg-1 wet wt, surpassing by almost five times the Brazilian advisory level for human consumption.

Elevated mercury concentrations in soils, sediments, water, and fish of the Madeira River basin, Brazilian Amazon: a function of natural enrichments?

Previous site-specific investigations have found that mercury concentrations in water, sediments, and biota of the Brazilian Amazon are elevated above global averages, and that these concentrations are a direct result of widespread mercury amalgamation mining operations conducted by non-organized prospectors. In order to assess the regional impacts of Hg contamination from these non-organized gold mining activities, water, sediments, and fish were systematically collected in 1997 along a 900-km reach of the Madeira River. The sampling program extended from the Amazon River upstream to Porto Velho, the site of historic and ongoing mercury amalgamation mining. Mercury concentrations were found to be elevated above global averages in all sampled media. However, the geochemical data suggest that the high mercury levels are due largely to natural sources and natural biogeochemical processes, and that the impacts of anthropogenically released mercury from mine sites is relatively localized.

Forest fire indicators and mercury deposition in an intense land use change region in the Brazilian Amazon (Alta Floresta, MT).

Black carbon, charcoal and mercury fluxes were measured from sediment cores taken in an artificial water dam in an intense land use change area in the Alta Floresta district in the Brazilian Amazon, in order to characterize the differences in the evolution of human occupation patterns in the region during the last 18 years. A positive correlation between the black carbon and charcoal particle fluxes and the evolution of the Brazilian gross domestic production (GDP) was observed. Mercury fluxes showed a positive correlation with gold production and exhibited a distinct evolution pattern when compared to in relation to the forest fires indicators and Brazilian GDP. The fluxes of forest fires markers showed an increase in deforestation activities in the region after 1993. Mercury deposition showed a substantial decrease after 1994. The patterns of distribution in both forest fires tracers and gold mining tracers indicate substitution of the regional economic model. It also marked different antropogenic impact type in the ecosystem.

Contribution of a medium-sized tropical river to the particulate heavy-metal load for the South Atlantic Ocean.

The Paraíba do Sul River is a medium-sized river, 1145 km in length with a drainage basin of 55,400 km2. The riverine fluxes of particulate metals (Cu, Cr, Zn, Mn and Fe) were investigated over 24 months. Particulate matter samples were monthly collected from April 1994 to March 1996. The first 12-month period presented lower rainfall than the second, although both periods presented average precipitation lower than the regional average. The particulate matter flux in the second period (2,042,080 t) was 250% higher than the first period (821,489 t). The same trend was observed for the associated metals, which presented higher fluxes in the second period. This study highlights the strong dependence of the transported mass on the rainfall, and consequently with the river water discharge. The Paraiba do Sul River presents a low contribution to the world oceans, although the local contribution could be considered relevant.

Trace metal retention in mangrove ecosystems in Guanabara Bay, SE Brazil.

Along contrasting environmental conditions (e.g., degree of trace metal contamination and mangrove forest structural development), sediments of Laguncularia racemosa-dominated mangrove stands in Guanabara Bay (SE Brazil) presented a trend of trace metal accumulation in forms with low potential of remobilization and biotic uptake. Concurrently, a relatively low transfer of sediment-bound metals to L. racemosa leaves was observed, which may moderate the metal export from the forests via leaf litter transport and the metal availability to enter in food chains based on leaf consumption.

The effect of an oil drilling operation on the trace metal concentrations in offshore bottom sediments of the Campos Basin oil field, SE Brazil.

The concentrations of Al, Fe, Mn, Zn, Cu, Pb, Ni, Cr, Ba, V, Sn and As in offshore bottom sediments from the Bacia de Campos oil field, SE Brazil, were measured at the beginning and at 7 months after completion of the drilling operation. Concentrations of Al, Fe, Ba, Cr, Ni and Zn were significantly higher closer to the drilling site compared to stations far from the site. Average concentrations of Al, Cu, and in particular of Ni, were significantly higher at the end of the drilling operation than at the beginning. Comparison between drilling area sediments with control sediments of the continental platform, however, showed no significant difference in trace metal concentrations. Under the operation conditions of this drilling event, the results show that while changes in some trace metal concentrations do occur during drilling operations, they are not significantly large to be distinguished from natural variability of the local background concentrations.

Mercury content in shark species from the South-Eastern Brazilian coast.

We present here the first results of Hg concentrations in three small shark species (Rhizoprionodon lalandei, R. porosus and Mustelus higmani) from the SE Brazilian coast. Mercury concentrations in R. lalandei ranged from 21.5 to 280.0 ng.g-1 dry weight (d.w.) (average 74.6 ng.g-1 d.w.; 17.9 ng.g-1 wet weight). In R. porosus, concentrations ranged from 7.6 to 90.5 ng.g-1 d.w. (average 42.2 ng.g-1 d.w., 9.4 ng.g-1 wet weight), whereas in M. higmani, concentrations ranged from 13.0 to 162.8 ng.g-1 d.w. (average 54.9 ng.g-1 d.w., 13.4 ng.g-1 wet weight). These concentration ranges are very low compared with values reported for other large shark species of the Southwestern Atlantic Ocean. There was a significant positive correlation between Hg concentrations and individual size, suggesting that biomagnification is occurring in these animals.