Fractionation of iron species and iron isotopes in the Baltic Sea euphotic zone

To indentify sources and transport mechanisms of iron in a coastal marine environment, we conducted measurements of the physiochemical speciation of Fe in the euphotic zone at three different locations in the Baltic Sea. In addition to sampling across a salinity gradient, we conducted this study over the spring and summer season. Moving from the riverine input characterized low salinity Bothnian Sea, via the Landsort Deep near Stockholm, towards the Gotland Deep in the Baltic Proper, total Fe concentrations averaged 114, 44, and 15 nM, respectively. At all three locations, a decrease in total Fe of 80–90% from early spring to summer was observed. Particulate Fe (PFe) was the dominating phase at all stations and accounted for 75–85% of the total Fe pool on average. The Fe isotope composition (δ 56Fe) of the PFe showed constant positive values in the Bothnian Sea surface waters (+0.08 to +0.20‰). Enrichment of heavy Fe in the Bothnian Sea PFe is possibly associated to input of aggregated land derived Fe-oxyhydroxides and oxidation of dissolved Fe(II). At the Landsort Deep the isotopic fractionation of PFe changed between −0.08‰ to +0.28‰ over the sampling period. The negative values in early spring indicate transport of PFe from the oxic-anoxic boundary at ∼80 m depth. The average colloidal iron fraction (CFe) showed decreasing concentrations along the salinity gradient; Bothnian Sea 15 nM; Landsort Deep 1 nM, and Gotland Deep 0.5 nM. Field Flow Fractionation data indicate that the main colloidal carrier phase for Fe in the Baltic Sea is a carbon-rich fulvic acid associated compound, likely of riverine origin. A strong positive correlation between PFe and chl-a indicates that cycling of suspended Fe is at least partially controlled by primary production. However, this relationship may not be dominated by active uptake of Fe into phytoplankton, but instead may reflect scavenging and removal of PFe during phytoplankton sedimentation

Fractionation of Iron Species and Iron Isotopes in the Baltic Sea Euphotic Zone

To indentify sources and transport mechanisms of iron in a coastal marine environment, we conducted measurements of the physiochemical speciation of Fe in the euphotic zone at three different locations in the Baltic Sea. In addition to sampling across a salinity gradient, we conducted this study over the spring and summer season. Moving from the riverine input characterized low salinity Bothnian Sea, via the Landsort Deep near Stockholm, towards the Gotland Deep in the Baltic Proper, total Fe concentrations averaged 114, 44, and 15 nM, respectively. At all three locations, a decrease in total Fe of 80–90% from early spring to summer was observed. Particulate Fe (PFe) was the dominating phase at all stations and accounted for 75–85% of the total Fe pool on average. The Fe isotope composition (δ 56Fe) of the PFe showed constant positive values in the Bothnian Sea surface waters (+0.08 to +0.20‰). Enrichment of heavy Fe in the Bothnian Sea PFe is possibly associated to input of aggregated land derived Fe-oxyhydroxides and oxidation of dissolved Fe(II). At the Landsort Deep the isotopic fractionation of PFe changed between −0.08‰ to +0.28‰ over the sampling period. The negative values in early spring indicate transport of PFe from the oxic-anoxic boundary at ∼80 m depth. The average colloidal iron fraction (CFe) showed decreasing concentrations along the salinity gradient; Bothnian Sea 15 nM; Landsort Deep 1 nM, and Gotland Deep 0.5 nM. Field Flow Fractionation data indicate that the main colloidal carrier phase for Fe in the Baltic Sea is a carbon-rich fulvic acid associated compound, likely of riverine origin. A strong positive correlation between PFe and chl-a indicates that cycling of suspended Fe is at least partially controlled by primary production. However, this relationship may not be dominated by active uptake of Fe into phytoplankton, but instead may reflect scavenging and removal of PFe during phytoplankton sedimentation

Variations in the isotopic composition of molybdenum in freshwater lake systems

Variations in molybdenum isotopic composition, spanning the range of similar to 2.3 parts per thousand in the terms of Mo-97/Mo-95 ratio, have been measured in sediment cores from three lakes in northern Sweden and north-western Russia. These variations have been produced by both isotopically variable input of Mo into the lakes due to Mo isotopic heterogeneity of bedrock in the drainage basins and fractionation in the lake systems due to temporal variations in limnological conditions. Mo isotope abundances of bedrock in the lake drainage basins have been documented by analysis of Mo isotope ratios of a suite of molybdenite occurrences collected in the studied area and of detrital fractions of the lake sediment cores. The median delta Mo-97 value of the investigated molybdenites is 0.26 parts per thousand with standard deviation of 0.43 parts per thousand (n=19), whereas the median delta Mo-97 value of detrital sediment fractions from two lakes is -0.40 parts per thousand with standard deviation of 0.36 parts per thousand (n=15). The isotopic compositiori of Mo in the sediment cores has been found to be dependent on redox conditions of the water columns and the dominant type of scavenging phases. Hydrous Fe oxides have been shown to be an efficient scavenger of Mo from porewater under oxic conditions. Oxidative precipitation of Fe(II) in the sediments resulted in co-precipitation of Mo and significant authigenic enrichment at the redox boundary. In spite of a pronounced increase in Mo concentration associated with Fe oxides at the redox boundary the isotopic composition of Mo in this zone varies insignificantly, suggesting little or no isotope fractionation during scavenging of Mo by hydrous Fe oxides. In a lake with anoxic bottom water a chironomid-inferred reconstruction of O-2 conditions in the bottom water through the Holocene indicates that increased O-2 concentrations are generally associated with low delta Mo-97/Mo-95 values of the sediments, whereas lowered O-2 contents of the bottom water are accompanied by relatively high delta Mo-97/Mo-95 values, thus confirming the potential of Mo isotope data to be a proxy for redox conditions of overlying waters. However, it is pointed out that other processes including input of isotopically heterogeneous Mo and Mn cycling in the redox-stratified water column can be a primary cause of variations in Mo isotopic compositions of lake sediments

Development of indicators for measuring outcomes of water safety plans.

Water safety plans (WSPs) are endorsed by the World Health Organization as the most effective method of protecting a water supply. With the increase in WSPs worldwide, several valuable resources have been developed to assist practitioners in the implementation of WSPs, yet there is still a need for a practical and standardized method of evaluating WSP effectiveness. In 2012, the Centers for Disease Control and Prevention (CDC) published a conceptual framework for the evaluation of WSPs, presenting four key outcomes of the WSP process: institutional, operational, financial and policy change. In this paper, we seek to operationalize this conceptual framework by providing a set of simple and practical indicators for assessing WSP outcomes. Using CDC's WSP framework as a foundation and incorporating various existing performance monitoring indicators for water utilities, we developed a set of approximately 25 indicators of institutional, operational, financial and policy change within the WSP context. These outcome indicators hold great potential for the continued implementation and expansion of WSPs worldwide. Having a defined framework for evaluating a WSP's effectiveness, along with a set of measurable indicators by which to carry out that evaluation, will help implementers assess key WSP outcomes internally, as well as benchmark their progress against other WSPs in their region and globally

Irrigation water issues potentially related to the 2006 multistate E. coli O157:H7 outbreak associated with spinach

A multistate Escherichia coli O157:H7 outbreak in August and September 2006 was found to be associated with consumption of fresh bagged spinach traced to California. The California Food Emergency Response Team (CALFERT), consisting of personnel from the California Department of Public Health Food and Drug Branch (FDB) and the U.S. Food and Drug Administration (FDA) undertook an environmental investigation to determine how and why the spinach became contaminated. At the invitation of FDA and FDB, the Centers for Disease Control and Prevention (CDC) also participated in the environmental investigation. This paper presents findings from the portion of the environmental investigation focusing on environmental factors related to irrigation water that may have contributed to contamination of the spinach and hence to the outbreak. Analysis of the available data suggests that depths to groundwater and groundwater-surface water interactions may pose risks to ready-to-eat crops. These risks should be further evaluated and quantified to understand and identify the factors that contributed to this and similar outbreaks. One implication of this analysis is the need to continue to conceptually broaden the scope of produce-related outbreak investigations. Where feasible, investigation strategies should integrate possible contamination sources beyond those actually found on the farms that are identified as sources of produce involved in outbreaks.California Agriculture Food safety Outbreak investigation Fresh produce Groundwater-surface water interactions

“Back to the Future”: Time for a Renaissance of Public Health Engineering

Public health has always been, and remains, an interdisciplinary field, and engineering was closely aligned with public health for many years. Indeed, the branch of engineering that has been known at various times as sanitary engineering, public health engineering, or environmental engineering was integral to the emergence of public health as a distinct discipline. However, in the United States (U.S.) during the 20th century, the academic preparation and practice of this branch of engineering became largely separated from public health. Various factors contributed to this separation, including an evolution in leadership roles within public health; increasing specialization within public health; and the emerging environmental movement, which led to the creation of the U.S. Environmental Protection Agency (EPA), with its emphasis on the natural environment. In this paper, we consider these factors in turn. We also present a case study example of public health engineering in current practice in the U.S. that has had large-scale positive health impacts through improving water and sanitation services in Native American and Alaska Native communities. We also consider briefly how to educate engineers to work in public health in the modern world, and the benefits and challenges associated with that process. We close by discussing the global implications of public health engineering and the need to re-integrate engineering into public health practice and strengthen the connection between the two fields