Wetland influences on mercury transport and bioaccumulation in South Carolina.

There are three distinct geological provinces in South Carolina (SC), with the blue ridge/piedmont regions in the west/central portion of the state and the coastal plain region in the central/eastern region of the state. Samples were collected along this gradient to identify potential factors contributing to the concentrations of total Hg and total organic carbon (TOC) throughout the state. Overall, there is a gradient across the state, with water column concentrations of total Hg (9-53 pM) and TOC (80-2721 microM) increasing as one moves from the blue ridge/piedmont region to the coastal floodplain region. Total Hg at all sites in SC is significantly (R2=0.78; P<0.001) correlated with TOC in the water samples. This correlation explains 78% of the variance in the data and suggests that mercury is associated with organic matter in water bodies throughout the state. A study of mercury speciation within the coastal plain Waccamaw River indicates that concentrations of total Hg range from 10-68 pM and methyl Hg concentrations range from 1-7 pM. Watershed transport efficiencies for coastal floodplain rivers sampled in this study range from 32-72% for total Hg and 78-477% for methyl Hg. The coastal plain sites are located in watersheds that contain a significantly (P<0.001) higher percentage of wetlands (16.3+/-5%) than the blue ridge/piedmont region (1.14+/-1.6%), suggesting that drainage through wetlands contributes to the increased concentrations of TOC and total Hg found in SC coastal plain rivers. There is a significant correlation between mean fish Hg concentrations in largemouth bass from each watershed and percent wetland area in each watershed (R2=0.66; P=0.003). This correlation explains 66% of the variance in the data and suggests that increasing percentages of wetland area contribute to fish Hg concentrations in SC coastal plain rivers.

Mercury transport and bioaccumulation in riverbank communities of the Alvarado Lagoon System, Veracruz State, Mexico.

The Alvarado Lagoon System (ALS) is located within the Papaloapan River Basin in southern Veracruz, Mexico. The ALS is a shallow system (2 m) connected to the Gulf of Mexico through a narrow sea channel. There are a large number of riverbank communities within the ALS that are dependent upon its biological productivity for comestible and economic subsistence. The purpose of this project was to determine the levels of mercury in water, sediment, fish, and hair samples from within the Papaloapan River Basin and to characterize the risk of Hg exposure to the individuals that reside in these communities. Water and fish samples were collected during the wet (September 2005) and dry (March 2003 and 2005) seasons. Hair samples, dietary surveys, and sediment samples were obtained during the wet and dry seasons of 2005. Total Hg in the water column ranged from 1.0 to 12.7 ng/L. A strong correlation (R(2)=0.82; p<0.001) between total Hg and total suspended solids in the water column suggests that particulate matter is a transport mechanism for Hg within the lagoon system. Total Hg in the sediments ranged from 27.5 to 90.5 ng Hg/g dry weight with no significant difference between the 2005 wet and dry seasons. There was a mild, but significant, correlation between total Hg and % carbon for the March 2005 sediment samples (R(2)=0.435; p=0.020), suggesting that Hg is associated with organic matter on the solid phase. Concentrations of total Hg in fish and shellfish harvested from the ALS ranged from 0.01 to 0.35 microg Hg/g wet. The levels of total Hg in hair ranged from 0.10 to 3.36 microg Hg/g (n=47) and 58% of the samples were above 1.00 microg Hg/g. The findings from this study suggest that individuals who frequently consume fish and shell fish containing low levels of Hg (<0.3 microg/g) can accumulate low to moderate body burdens of Hg, as indicated by hair Hg concentrations>1.0 microg/g, and may be at risk for experiencing low dose mercury toxicity.

Mercury concentrations and omega-3 fatty acids in fish and shrimp: Preferential consumption for maximum health benefits.

The consumption of fish and shrimp containing omega-3 fatty acids can result in protective health effects including a reduced risk of cardiovascular disease, stroke, and diabetes. These protective effects may be decreased by the presence of mercury in the muscle tissue of fish and shellfish. Mercury can increase the risk of cardiovascular problems and impede neurological development. The objective of this project was to determine appropriate consumption amounts of selected fish species and shrimp based on mercury levels and recommended intake levels of omega-3 fatty acids. Species that are high in omega-3s and low in mercury include salmon, trout, and shrimp. Species with both high levels of mercury and omega-3 fatty acids include tuna, shark, and halibut, swordfish, and sea bass.

Postharvest management of gray mold and brown rot on surfaces of peaches and grapes using electrolyzed oxidizing water.

This study evaluated the potential use of near-neutral (pH=6.3-6.5) electrolyzed oxidizing water (EO water) to inactivate pure cultures of Botrytis cinerea and Monilinia fructicola and to mitigate fungal infection of these organisms on fruit surfaces. Treatment of these organisms, in pure culture, with EO water at concentrations of 25, 50, 75, and 100ppm total residual chlorine (TRC) and 10 min of contact time resulted in a 6 log(10) spores/mL reduction of both organisms. A dip treatment or a dip and daily spray treatment of EO water were used to evaluate its ability to prevent or delay the onset of surface infection on fruit during postharvest packaging and in retail shelf environments. A 10 minute dip treatment of surface inoculated peaches (M. fructicola) in EO water prevented infection for 3 days and resulted in a 12.5% incidence of infection and a disease severity rating of 6% after 5 days of storage at 25 degrees C. Dipping of green table grapes inoculated with B. cinerea into EO water prevented infection for 7 days and resulted in a 1% incidence of infection and a disease severity rating of 2% after 10 days of storage at 25 degrees C. A dip and daily spray of peaches with EO water prevented infection for 12 days and resulted in a 10% incidence of infection and a 6% disease severity after 14 days of storage at 25 degrees C. A dip and daily spray of grapes with EO water prevented infection for 24 days and resulted in a 2% incidence of infection and a disease severity rating of 2% after 26 days of storage at 25 degrees C. The results from this study suggest that these solutions may prove to be effective for postharvest sanitation of fruit surfaces prior to packaging and may increase the shelf life of the fruit in commercial settings.

Reduction of bacteria on spinach, lettuce, and surfaces in food service areas using neutral electrolyzed oxidizing water.

Food safety issues and increases in food borne illnesses have promulgated the development of new sanitation methods to eliminate pathogenic organisms on foods and surfaces in food service areas. Electrolyzed oxidizing water (EO water) shows promise as an environmentally friendly broad spectrum microbial decontamination agent. EO water is generated by the passage of a dilute salt solution ( approximately 1% NaCl) through an electrochemical cell. This electrolytic process converts chloride ions and water molecules into chlorine oxidants (Cl(2), HOCl/ClO(-)). At a near-neutral pH (pH 6.3-6.5), the predominant chemical species is the highly biocidal hypochlorous acid species (HOCl) with the oxidation reduction potential (ORP) of the solution ranging from 800 to 900mV. The biocidal activity of near-neutral EO water was evaluated at 25 degrees C using pure cultures of Escherichia coli, Salmonella typhimurium, Staphylococcus aureus, Listeria monocytogenes, and Enterococcus faecalis. Treatment of these organisms, in pure culture, with EO water at concentrations of 20, 50, 100, and 120ppm total residual chlorine (TRC) and 10min of contact time resulted in 100% inactivation of all five organisms (reduction of 6.1-6.7log(10)CFU/mL). Spray treatment of surfaces in food service areas with EO water containing 278-310ppm TRC (pH 6.38) resulted in a 79-100% reduction of microbial growth. Dip (10min) treatment of spinach at 100 and 120ppm TRC resulted in a 4.0-5.0log(10)CFU/mL reduction of bacterial counts for all organisms tested. Dipping (10min) of lettuce at 100 and 120ppm TRC reduced bacterial counts of E. coli by 0.24-0.25log(10)CFU/mL and reduced all other organisms by 2.43-3.81log(10)CFU/mL.