Rozane V. Marins

Sediment quality assessment in a tropical estuary: The case of Ceará River, Northeastern Brazil

The present study aimed to assess the sediment quality in a tropical estuary located in the northeast of Brazil under semi-arid conditions and multiple sources of contamination, using both toxicity bioassays and metal distribution. The metal distribution followed a concentration gradient decreasing one order of magnitude from the inner station toward the outer estuary, with amounts in the following order: Fe > Al > Zn > Cr > Pb > Cu. The index of geoaccumulation indicated a metal enrichment in the Ceará river sediment, mainly at inner sites, considered from moderately to strongly contaminated by Al, Cu, Cr and Zn. Sediment samples were considered toxic by means of whole sediment tests with copepods (reproduction) and amphipods (survival), and also elutriate fraction and sediment-water interface with sea urchin embryos (development). Acute and chronic toxicity did not exhibit a significant correlation with metals, emphasizing the influence of other contaminants mainly related to the pollution sources installed in the mid-estuary.

Relative Importance of Non-Point Sources of Mercury to an Industrialized Coastal System, Sepetiba Bay, SE Brazil

Estimation of Hg emissions to air, soil and water is the first step in the regional management and control of areas where Hg contamination is potentially significant and no clear point source of this metal exists, such as in diversified industrial parks. Sepetiba Bay basin, SE Brazil, is an example of such a situation. Over 400 industries, from oil-fired power plants to steel and non-ferrous metal manufacturing to plastics and chemicals, have been installed in the region since the late 196os. Important point sources of metals such as Cd, Zn and Pb have been identified and controlled during the past decade; no significant point source of Hg, however, has been identified in the area. Notwithstanding, Hg is a ubiquitous byproduct of many industries and is also frequently present in urban and domestic wastes (Barcellos and Lacerda 1994; Marins et al. 1996).

Mercury degassing from forested and open field soils in Rondônia, Western Amazon, Brazil

A Teflon dynamic flux chamber was used to characterize Gaseous Elemental Mercury (GEM) flux from forested and open field soils in a highly changing environment in Rondônia State, western Amazon. We simultaneously analyzed meteorological parameters at the soil level relating GEM fluxes to soil temperature, air humidity, soil moisture, solar radiation, and speed and wind direction. We also examined variations of atmospheric GEM concentration. GEM fluxes during the day and night in the open field site were significantly different (17+/-14ngm(-2) h(-1) and 0.9+/-1.9ngm(-2)h(-1), for day and night, respectively), but were similar within the forest site (4.8+/-1.4ngm(-2)h(-1) and 4.4+/-1.8ngm(-2) h(-1) for day and night periods, respectively). A comparison between 24-h periods averages in the two sites showed much larger emission from the open field site. GEM fluxes at the open field site were positively correlated with soil moisture, solar irradiation and soil temperature and inversely correlated with air humidity. At the forest site GEM fluxes showed no correlation with meteorological variables. At the open field site GEM concentrations significantly correlated with GEM flux, at least during the day. At night in the open field site and during the day and night at the forest site no correlation was found between GEM fluxes and GEM concentrations in the ambient air. Higher emissions from the open field site support earlier studies showing larger Hg remobilization following forest conversion to pasture.

Alternativa analítica para especiação físico-química de mercúrio em águas costeiras tropicais

The determination of the physical-chemical mercury speciation in tropical coastal waters using the derivatization technique with CVAFS detection was optimized. This methodology is able to separate the elementary, reactive, organic and total mercury phases with low operational costs. The importance of bromide chloride solution, the diluted aqua regia, used as the oxidative solution, and different compositions of the reductive solution of stannous chloride were tested and the better results for coastal waters are presented. The recuperation of the sum of the different phases ranges from 80 to 94% of the total Hg content in duplicates of different marine samples. The optimized methodology permits important studies on the mercury cycle in the coastal environment.

Mercury distribution and reactivity in waters of a subtropical coastal lagoon, Sepetiba Bay, SE Brazil

A survey of the reactive and total Hg concentrations in surface waters and of the quantity of particulate organic carbon (POC) and dissolved organic carbon (DOC), were performed along a transect from the major rivers mouths and mangrove dominated areas to the open bay waters of Sepetiba Bay, SE Brazil. The objective of the survey was to evaluate changes in Hg reactivity during the transport along the estuarine gradient. Reactive Hg concentrations were lowest in open bay waters, (0.09 ± 0.06 ng L -1 ), followed by river influenced waters (0.19 ± 0.06 ng L -1 ), and mangrove (0.29 ± 0.02 ng L-1). Total Hg concentrations were lowest in open bay (0.38 ± 0.20 ng L -1 ), followed by mangrove waters (0.56 ± 0.01 ng L -1 ), and river influenced waters (0.99 ± 0.29 ng L -1 ). The percentages of reactive Hg relative to the total Hg concentrations were lowest in river influenced waters, (20.7%), followed by open bay waters (31.2%), and mangrove waters (53.2%). The percent of reactive Hg to the total Hg concentrations showed a significant negative correlation with the total Hg concentrations following a potential equation. No relationship between reactive Hg concentrations and POC, salinity or pH were found, however, reactive Hg correlates significantly with DOC, suggesting that organo-complexes, rather than chloro-complexes, are the major controllers of Hg reactivity, and eventually bioavailability in Sepetiba Bay.

Dissolved mercury concentrations and reactivity in mangrove waters from the Itacurussa Experimental Forest, Sepetiba Bay, SE Brazil

Mangrove waters from the Itacurussa Experimental Forest (IEF), SE Brazilare enriched in reactive-Hg (15 ± 2.0 pM) and total-Hg (28 ±2.5 pM) relative to open bay waters (4.5 ± 3.0 pM and 19 ±8.5 pM, for reactive-Hg and total-Hg respectively). Mercury concentrationsand reactivity varied according to tidal flux in mangrove creek waters.Reactive-Hg concentrations were higher in ebb tide waters ranging from 4.5to 8.5 pM, than in flood water (< 1.0 to 3.5 pM), whereas total-Hgconcentrations were higher in flood waters, from 40 to 360 pM, than inebb water (30 to 250 pM). Low-Hg, open bay waters are enriched in Hgwhen flowing over mud flats prior to entering the IEF, where it mixes withpore waters containing extremely high Hg concentrations (up to 2,500pM). Similar distributions of Hg and DOC in pore waters, suggests thatDOC may facilitate Hg migration through the sedimentary column, asshown for other estuarine areas. Mud flat pore waters are the more likelysource of total Hg to mangrove waters, but not for reactive Hg. Theseresults suggest that mangroves act as a sink to total Hg, as has been shownfor other trace metals at the IEF and other mangrove forests. On the otherhand mangroves act as a source of reactive Hg to adjacent coastal waters.The mechanisms involved in this processes have not been studied in thispaper. However, the similar distribution of DOC and Hg among thedifferent water masses of the IEF, suggest that the dynamics of Hg-DOCcomplexes may play a dominant role.

Pluriannual watershed discharges of hg into a tropical semi-arid estuary of the Jaguaribe river, NE Brazil

Mercury fluxes were measured during the dry and rainy seasons (2005 to 2009) at the Jaguaribe River estuary, which discharges into the Equatorial Atlantic Ocean in NE Brazil. During rainy periods, the water masses exhibited a short residence time within the estuary (0.8 days). During dry periods, seawater choked the fluvial discharge, resulting in longer residence times (3.1 days). Dissolved (< 0.7 µm) and particulate Hg concentrations and fluxes were greater from the river to the estuary than from the estuary to the sea, producing accumulated particulate Hg in the estuary. Particulate Hg export (1.8 to 12.6 mg s-1) to the ocean occurred during extremely rainy periods, while dissolved Hg export was practically nonexistent during rainy periods and increased up to 0.45 mg s-1 during dry periods. Because continental runoff in semi-arid regions is affected by land use and global climate changes, the increasing accumulation of particulate Hg in the estuaries and increasing export of dissolved Hg to the ocean are expected.

Mercury speciation changes in waters of the sepetiba Bay, SE Brazil during tidal events and different seasons

This work describes changes in Hg speciation in water along the transport from Sepetiba Bay, SE Brazil, to the adjacent continental platform during tide events and in different seasons. The chemical evaluation of Sepetiba Bay waters showed that the bay exports suspended particulate material (SPM) impoverish in organic carbon to adjacent continental platform areas, mainly during the wet season and imports SPM enriched in organic carbon from the ocean, probably of phytoplanktonic origin, during the dry season. The chemical speciation of Hg during the study period showed that Hg0 production can be controlled by primary productivity and that the bay acts as a producer and exporter of organic species of Hg to adjacent areas, since the highest non-reactive Hg concentrations were observed during the ebb tide. No significant correlations were found between non-reactive Hg and dissolved or particulate organic matter concentrations. In general the particulate Hg, non-reactive Hg and reactive Hg fractions represents 55%, 35.5% and 9.5% of the total Hg content in Sepetiba Bay waters, respectively.

Emissões naturais e antrópicas de metais e nutrientes para a bacia inferior do rio de contas, Bahia

Emission factors of anthropogenic activities and natural processes were used to estimate nutrients and metals loads to the Contas River lower basin, Southern Bahia, Brazil. Among natural sources, emission from soil leaching is larger for N, Cu and Pb. Atmospheric deposition is the major natural source of P, Zn, Cd and Hg. Among anthropogenic sources, agriculture is the major source of N, Cu and P. Urban sources are the major contributors to the other elements. Present anthropogenic land uses are already responsible for 78 and 99% of total N and P loads and about 50% of total Cu and Hg.

Methodology optimization and application for measurement of gaseous elemental mercury in the amazon atmosphere

The aim of this study was to optimize a semi-automatic methodology using commercial pure gold cartridges (Tekran Inc.) to quantify gaseous elemental mercury (GEM) in the Amazon atmosphere. The detection limit was 0.020 ± 0.006 ng Hg. This corresponds to detection limits varying from 0.2 to 0.4 ng Hg m-3, for field sample volumes ranging between 0.1 and 0.05 m3. The similarity between the 9 tested cartridges was evaluated. Under sampling flow rates varying between 0.4 and 2.0 L min-1 no difference among cartridges was observed. The maximum retention capacity of the cartridge (breakthrough) was not reached in experiments with flow rates of 1 or 2 L min-1, and with Hg concentration of 25 ng m-3 and maximum air volume of 150 L. Water condensation on the gold surface showed to be a problem, but that was solved by heating the sample cartridge at 60 oC during sampling.