Electrocatalysis of anodic and cathodic oxygen-transfer reactions

The electrocatalysis of oxygen-transfer reactions is discussed in two parts. In Part I, the reduction of iodate (IO[subscript]sp3-) is examined as an example of cathodic oxygen transfer. On oxide-covered Pt electrodes (PtO), a large cathodic current is observed in the presence of IO[subscript]sp3- to coincide with the reduction of PtO. The total cathodic charge exceeds the amount required for reduction of PtO and IO[subscript]sp3- to produce an adsorbed product. An electrocatalytic link between reduction of IO[subscript]sp3- and reduction of PtO is indicated;In addition, on oxide-free Pt electrodes, the reduction of IO[subscript]sp3- is determined to be sensitive to surface treatment. The results are consistent with a mechanism involving the adsorption of IO[subscript]sp3- onto I°-covered Pt sites (Pt(I[subscript]sp ads∘)). Previous researchers have relied on chemical steps in the mechanism of IO[subscript]sp3- reduction to account for their results;The electrocatalytic oxidation of CN[superscript]- is presented as an example of anodic oxygen transfer in Part II. The electrocatalytic oxidation of CN[superscript]- is considered to be an important process for the treatment of industrial and laboratory wastes. Present electrode materials are unsuitable for CN[superscript]- oxidation for reasons of low current efficiency and high attrition rates. The voltammetric response of CN[superscript]- is virtually nonexistent at PbO[subscript]2 electrodes. Whereas the response is not improved by doping PbO[subscript]2 with Bi, the response is significantly improved by doping PbO[subscript]2 with Cu. Cyanide is also oxidized effectively at CuO-film electrodes. Copper is concluded to serve as an adsorption site for CN[superscript]-. It is proposed that an oxygen tunneling mechanism comparable to electron tunneling does not occur at the electrode-solution interface. The adsorption of CN[superscript]- is therefore considered to be a necessary prerequisite for oxygen transfer. ftn*DOE Report IS-T 1450. This work was performed under contract No. W-7405-eng-82 with the U.S. Department of Energy

Electrocatalysis of anodic and cathodic oxygen-transfer reactions

The electrocatalysis of oxygen-transfer reactions is discussed in two parts. In Part I, the reduction of iodate (IO[subscript]sp3-) is examined as an example of cathodic oxygen transfer. On oxide-covered Pt electrodes (PtO), a large cathodic current is observed in the presence of IO[subscript]sp3- to coincide with the reduction of PtO. The total cathodic charge exceeds the amount required for reduction of PtO and IO[subscript]sp3- to produce an adsorbed product. An electrocatalytic link between reduction of IO[subscript]sp3- and reduction of PtO is indicated;In addition, on oxide-free Pt electrodes, the reduction of IO[subscript]sp3- is determined to be sensitive to surface treatment. The results are consistent with a mechanism involving the adsorption of IO[subscript]sp3- onto I°-covered Pt sites (Pt(I[subscript]sp ads∘)). Previous researchers have relied on chemical steps in the mechanism of IO[subscript]sp3- reduction to account for their results;The electrocatalytic oxidation of CN[superscript]- is presented as an example of anodic oxygen transfer in Part II. The electrocatalytic oxidation of CN[superscript]- is considered to be an important process for the treatment of industrial and laboratory wastes. Present electrode materials are unsuitable for CN[superscript]- oxidation for reasons of low current efficiency and high attrition rates. The voltammetric response of CN[superscript]- is virtually nonexistent at PbO[subscript]2 electrodes. Whereas the response is not improved by doping PbO[subscript]2 with Bi, the response is significantly improved by doping PbO[subscript]2 with Cu. Cyanide is also oxidized effectively at CuO-film electrodes. Copper is concluded to serve as an adsorption site for CN[superscript]-. It is proposed that an oxygen tunneling mechanism comparable to electron tunneling does not occur at the electrode-solution interface. The adsorption of CN[superscript]- is therefore considered to be a necessary prerequisite for oxygen transfer. ftn*DOE Report IS-T 1450. This work was performed under contract No. W-7405-eng-82 with the U.S. Department of Energy.</p

High prevalence of elevated blood lead levels in both rural and urban Iowa newborns: Spatial patterns and area-level covariates.

Lead in maternal blood can cross the placenta and result in elevated blood lead levels in newborns, potentially producing negative effects on neurocognitive function, particularly if combined with childhood lead exposure. Little research exists, however, into the burden of elevated blood lead levels in newborns, or the places and populations in which elevated lead levels are observed in newborns, particularly in rural settings. Using ~2300 dried bloods spots collected within 1-3 days of birth among Iowa newborns, linked with the area of mother's residence at the time of birth, we examine the spatial patterns of elevated (>5 μg/dL) blood lead levels and the ecological-level predictors of elevated blood lead levels. We find that one in five newborns exceed the 5 μg/dL action level set by the US Centers for Disease Control & Prevention (CDC). Bayesian spatial zero inflated regression indicates that elevated blood lead in newborns is associated with areas of increased pre-1940s housing and childbearing-age women with low educational status in both rural and urban settings. No differences in blood lead levels or the proportion of children exceeding 5 μg/dL are observed between urban and rural maternal residence, though a spatial cluster of elevated blood lead is observed in rural counties. These characteristics can guide the recommendation for testing of infants at well-baby appointments in places where risk factors are present, potentially leading to earlier initiation of case management. The findings also suggest that rural populations are at as great of risk of elevated blood lead levels as are urban populations. Analysis of newborn dried blood spots is an important tool for lead poisoning surveillance in newborns and can direct public health efforts towards specific places and populations where lead testing and case management will have the greatest impact

Correction: High prevalence of elevated blood lead levels in both rural and urban Iowa newborns: Spatial patterns and area-level covariates.

[This corrects the article DOI: 10.1371/journal.pone.0177930.]

Number of samples per ZCTA included in the study (areas of white represent ZCTAs with no samples).

<p>The location of urban areas in Iowa with populations over 50,000 people are shown for reference.</p

Spatial zero-inflated Poisson regression of hypothesized area covariates for the outcome of counts of blood lead levels >5 μg/dL in ZCTAs.

<p>Spatial zero-inflated Poisson regression of hypothesized area covariates for the outcome of counts of blood lead levels >5 μg/dL in ZCTAs.</p

Distribution of lead values in blank filter paper used for analysis.

<p>Distribution of lead values in blank filter paper used for analysis.</p

Distribution of ZCTAs with samples exhibiting elevated lead levels.

<p>The majority of ZCTAs had zero samples above the 5 μg/dL and 10 μg/dL thresholds.</p