Andrea Bravo - Academia.edu (original) (raw)

Papers by Andrea Bravo

Water Research, 2015

Iron-reducing bacteria Sulfate-reducing bacteria Sediments Iron Sewage treatment plant a b s t r ... more Iron-reducing bacteria Sulfate-reducing bacteria Sediments Iron Sewage treatment plant a b s t r a c t Sewage treatment plants (STPs) are important point sources of mercury (Hg) to the environment. STPs are also significant sources of iron when hydrated ferric oxide (HFO) is used as a dephosphatation agent during water purification. In this study, we combined geochemical and microbiological characterization with Hg speciation and sediment amendments to evaluate the impact of STP's effluents on monomethylmercury (MMHg)

Environment International, 2015

Mercury (Hg) in soils has increased by a factor of 3 to 10 in recent times mainly due to combusti... more Mercury (Hg) in soils has increased by a factor of 3 to 10 in recent times mainly due to combustion of fossil fuels combined with long-range atmospheric transport processes. Other sources as chlor-alkali plants, gold mining and cement production can also be significant, at least locally. This paper summarizes the natural and anthropogenic sources that have contributed to the increase of Hg concentration in soil and reviews major remediation techniques and their applications to control soil Hg contamination. The focus is on soil washing, stabilisation/solidification, thermal treatment and biological techniques; but also the factors that influence Hg mobilisation in soil and therefore are crucial for evaluating and optimizing remediation techniques are discussed. Further research on bioremediation is encouraged and future study should focus on the implementation of different remediation techniques under field conditions.

Marine Pollution Bulletin, 2014

Sediments and biota samples were collected in a restricted area of the Lagoon of Venice and analy... more Sediments and biota samples were collected in a restricted area of the Lagoon of Venice and analysed for total mercury, monomethyl mercury (MMHg), and nitrogen and carbon isotopes. Results were used to examine mercury biomagnification in a complex food chain. Sedimentary organic matter (SOM) proved to be a major source of nutrients and mercury to primary consumers. Contrary to inorganic mercury, MMHg was strongly biomagnified along the food chain, although the lognormal relationship between MMHg and δ(15)N was less constrained than generally reported from lakes or coastal marine ecosystems. The relationship improved when logMMHg concentrations were plotted against trophic positions derived from baseline δ(15)N estimate for primary consumers. From the regression slope a mean MMHg trophic magnification factor of 10 was obtained. Filter-feeding benthic bivalves accumulated more MMHg than other primary consumers and were probably important in MMHg transfer from sediments to higher levels of the food chain.

Environmental Science and Pollution Research, 2009

Background, aim and scope Mercury (Hg) is a ubiquitous and hazardous contaminant in the aquatic e... more Background, aim and scope Mercury (Hg) is a ubiquitous and hazardous contaminant in the aquatic environment showing a strong biomagnification effect along the food chain. The most common transfer path of Hg to humans is contaminated fish consumption. In severely exposed humans, Hg poisoning may lead to damage in the central nervous system. Thus, it is important to examine current and past contamination levels of Hg in aquatic milieu. The Olt River is the largest Romanian tributary of the Danube River. The use of Hg as an electrode in a chlor-alkali plant contributed to the contamination of the aquatic environment in the Rm Valcea region. The purpose of this study was to compare the current state of Hg contamination with the past contamination using a historical record obtained from a dated sediment core from one of the Olt River reservoirs (Babeni) located downstream from the chlor-alkali plant. To our knowledge, no published data on Hg contamination in this region are available. The Babeni Reservoir was selected for this study because it is situated downstream from the chlor-alkali plant, whilst the other reservoirs only retain the pollutants coming from the upstream part of the watershed. Preliminary analyses (unpublished) showed high Hg concentrations in the surface sediment of the Babeni Reservoir. One core was taken in the upstream Valcea Reservoir to provide a local background level of Hg concentrations in sediments. Results and discussion Sediment texture was uniform in the cores from both reservoirs. Laminated sediment structure, without any obvious discontinuities, was observed. Hg concentrations in the sediment core from the Valcea Reservoir were low and constant (0.01-0.08 mg/kg). In Babeni Reservoir sediments, Hg concentrations were very high in the deeper core section (up to 45 mg/kg in the longest core) and decreased to lower concentrations toward the top of the cores (1.3-2.4 mg/kg). This decrease probably reflects technological progress in control of emissions from the Hg-cell-based chlor-alkali industry. Two strong peaks could be distinguished in older sediments. The mean rate of sedimentation (5.9 cm/year) was calculated from the depth of the 137 Cs Chernobyl peak. This was in good agreement with the sedimentation rate estimated at this site from a bathymetric study. Assuming a constant sedimentation rate, the two Hg peaks would reflect two contamination events in 1987 and 1991, respectively. However, it is also possible that the two peaks belong to the same contamination event in 1987 but were separated by a sediment layer richer in sand and silt. This layer had a low Hg concentration, which can be interpreted as a mass deposition event related to a major flood bringing Hg-free sediments.

Environmental Science and Pollution Research, 2010

Purpose Chlor-alkali plants are one of the most important point sources of mercury to aquatic env... more Purpose Chlor-alkali plants are one of the most important point sources of mercury to aquatic environment. The problem of Hg contamination has been studied in a region, Rm Valcea (Romania), impacted by the wastewater discharge of a chlor-alkali plant. The purpose of the present study is to evaluate the current status of mercury pollution in the Babeni reservoir (Olt River) and the exposure of local population via fish consumption to mercury originating from the chlor-alkali plant. Methods Sediments were collected from Valcea, Govora and Babeni reservoirs. Grain size distribution, organic content and total mercury (THg) concentrations were analysed in sediments. Fish were purchased from local anglers, and the scalp hair was collected from volunteers. THg in sediment, fish and hair samples was determined using an atomic absorption spectrophotometer for Hg determination. Monomethylmercury (MMHg) was analysed in the muscle and liver tissues by species-specific isotope dilution and capillary gas chromatography hyphenated to inductively coupled plasma mass spectrometer. Results High mercury concentrations were found in the sediments and in fish from Babeni reservoir, with a median of 2.1 mg/kg (IQR=3.2) in sediments and a mean value of 1.8±0.8 mg/kg_ww in fish muscle. MMHg concentrations in fish were well above the WHO guidelines for fish consumption. Local population consuming fish from the Babeni reservoir had THg concentrations in hair significantly higher than those consuming fish from upstream reservoirs and/or from the shops and reached a median value of 2.5 mg/kg (IQR=3.6). Conclusions The remnant pollution in the fish of this reservoir, and probably many other lakes and reservoirs receiving Hg polluted wastewater, represents a considerable health risk for the local fish consumers.

Ecotoxicology and Environmental Safety, 2010

In situ microcosm study investigated both the kinetics of plant material mass loss and qualitativ... more In situ microcosm study investigated both the kinetics of plant material mass loss and qualitative and quantitative aspects of DNA content by researching leaf degradation of two specific varieties of tomato (Admiro and Palmiro) in freshwater column incubated for 40 days. A two-compartment first order model fitted both tomato dry matter and DNA content mass loss well. The composite half-decrease times were, respectively, 1.13 ± 0.51 and 1.16 ± 0.47 days for Palmiro and Admiro. The composite half-disappearance times of total DNA in Palmiro and Admiro tomato leaves were, respectively, 0.92 ± 0.31 and 0.88 ± 0.26 days. Genomic analysis indicates that before having been released, a significant amount of DNA may be degraded in plant tissues decomposing in water column. The results of this study confirm the hypothesis that release of plant DNA in aquatic environments can be caused by intracellular nuclease activities in the plants cells and by enzymatic degradation of cell structures by residual microbial activities in leaves.

Ecological Indicators, 2010

Bioresource Technology, 2008

In 2001, the municipality of Lausanne extended the outlet pipe of the sewage treatment plant into... more In 2001, the municipality of Lausanne extended the outlet pipe of the sewage treatment plant into the Bay of Vidy (Lake Geneva, Switzerland) as a measure to reduce bacterial water pollution and sediment contamination close to the lake beaches. The aim of the present study was to assess the impact of this measure. Lake bottom sediments were collected and analyzed for grain size, organic matter, organic carbon, nitrogen, phosphorus, heavy metals and hydrophobic organic compounds to evaluate their concentration and spatial distribution. Our results demonstrate that, compared to results obtained before the outlet pipe prolongation, the surface area of highly contaminated sediments was reduced by one third after the pipe extension. However, contaminant concentrations are still high and the accumulation of pollutants may represent a significant source of toxicity for benthic organisms. One concludes that contaminant reduction at the source will be necessary for a further improvement.

Water Research, 2014

Keywords: Mercury Methylation Biomagnification Chlor-alkali Fish Reservoir a b s t r a c t We exa... more Keywords: Mercury Methylation Biomagnification Chlor-alkali Fish Reservoir a b s t r a c t We examined mercury (Hg) biogeochemistry and biomagnification in the Babeni Reservoir, a system strongly affected by the release of Hg from a chlor-alkali plant. Total mercury (THg) concentrations in river water reached 88 ng L À1 but decreased rapidly in the reservoir (to 9 ng L À1 ). In contrast, monomethylmercury (MMHg) concentrations increased from the upstream part of the reservoir to the central part (0.7 ng L À1 ), suggesting high methylation within the reservoir. Moreover, vertical water column profiles of THg and MMHg indicated that Hg methylation mainly occurred deep in the water column and at the sedimentewater interface. The discharge of Hg from a chlor-alkali plant in Valcea region caused the highest MMHg concentrations ever found in non-piscivorous fish worldwide. MMHg concentrations and bioconcentration factors (BCF) of plankton and macrophytes revealed that the highest biomagnification of MMHg takes place in primary producers. ª