RESUMO
Brazilian coastal areas have been exposed to various anthropic influences including physical alteration such as marina construction. To assess the impact of the pier marina construction in the Saco da Ribeira cove (Flamengo Bay, SE Brazil), sedimentological (grain size), geochemical (organic and trace elements) parameters and benthic foraminifera were analyzed on a 50-cm-long dated sediment core covering the last century. The multiproxy approach applied to a numerical hydrodynamic model shows that the circulation in the study area underwent an overall reduction (ca. 30 %) after the pier marina construction in the 1970s, promoting an increase of mud accumulation and higher concentrations of total organic carbon and trace elements (i.e., Enrichment Factor Cu from 0.80 to 1.4) as well as a shift in the benthic foraminiferal assemblages (i.e., foraminiferal density from 63 to 23.20 specimens per 10 cm3 and dominance from 0.13 to 0.73). On the basis of these integrated data, better environmental conditions occurred before the 1970s, then an overall increase in environmental stress took place after the pier's marina construction. Our results provide a baseline for future biomonitoring projects in a stressed region and exemplify the strong capability and reliability of benthic foraminifera as bioindicators of paleoenvironmental changes in coastal environments and for understanding how human pressure might induce such changes.
Assuntos
Foraminíferos , Oligoelementos , Humanos , Monitoramento Ambiental/métodos , Sedimentos Geológicos , Brasil , Oligoelementos/análise , Baías , Reprodutibilidade dos TestesRESUMO
This study assessed the influence of hydrodynamic conditions on the degradation process of 1-butyl-3-methylimidazolium chloride (BMImCl) solution on a boron-doped diamond anode in a filter-type electrochemical reactor configuration. The results show that this parameter did not significantly affect this process when operating in the laminar regime. However, in the transition regime (Reâ¯≥â¯2000), higher flow rates resulted in a faster removal of BMImCl and total organic carbon, making the process more efficient. Following BMImCl degradation, nitrates were generated at the cathode, then reduced at the cathode to ammonium; combination with free chloride produced at the anode led to the transformation of chloride into combined chlorine forms instead of more toxic oxianions such as chlorate and perchlorate. Thus, the flow rate can be a key parameter for defining operating conditions in which the target BMImCl is more effectively degraded with reduced generation of undesirable secondary products.
Assuntos
Boro , Diamante , Técnicas Eletroquímicas/métodos , Hidrodinâmica , Imidazóis/análise , Poluentes Químicos da Água/análise , Eletrodos , Modelos Teóricos , OxirreduçãoRESUMO
The fluid dynamics of a liquid|liquid system inside a four-electrode electrochemical cell were studied by velocimetry magnetic resonance imaging (MRI) and flow propagator measurements. To characterize this system fully, three different cell configurations operating at two rotational frequencies were analyzed. Quantitative information about the stability of the liquid|liquid interface and the dynamics of the organic phase were determined. The NMR spectroscopy results were in agreement with the electrochemical measurements performed by using the same experimental setup.
RESUMO
The impacts of any activity on marine ecosystems will depend on the characteristics of the receptor medium and its resilience to external pressures. Salmon farming industry develops along a constant gradient of hydrodynamic conditions in the south of Chile. However, the influence of the hydrodynamic characteristics (weak or strong) on the impacts of intensive salmon farming is still poorly understood. This one year study evaluates the impacts of salmon farming on the marine sediments of both protected and exposed marine zones differing in their hydrodynamic characteristics. Six physico-chemical, five biological variables and seven indexes of marine sediments status were evaluated under the salmon farming cages and control sites. Our results identified a few key variables and indexes necessary to accurately evaluate the salmon farming impacts on both protected and exposed zones. Interestingly, the ranking of importance of the variables and the temporality of the observed changes, varied depending on the hydrodynamic characteristics. Biological variables (nematodes abundance) and environmental indexes (Simpson's dominance, Shannon's diversity and Pielou evenness) are the first to reflect detrimental impacts under the salmon farming cages. Then the physico-chemical variables such as redox, sulphurs and phosphorus in both zones also show detrimental impacts. Based on the present results we propose that the hydrodynamic regime is an important driver of the magnitude and temporality of the effects of salmon farming on marine sediments. The variables and indexes that best reflect the effects of salmon farming, in both protected and exposed zones, are also described.