Spatial and temporal variations in Pb concentrations and isotopic composition in road dust, farmland soil and vegetation in proximity to roads since cessation of use of leaded petrol in the UK

Results are presented for a study of spatial distributions and temporal trends in concentrations of lead (Pb) from different sources in soil and vegetation of an arable farm in central Scotland in the decade since the use of leaded petrol was terminated. Isotopic analyses revealed that in all of the samples analysed, the Pb conformed to a binary mixture of petrol Pb and Pb from industrial or indigenous geological sources and that locally enhanced levels of petrol Pb were restricted to within 10 m of a motorway and 3 m of a minor road. Overall, the dominant source of Pb was historical emissions from nearby industrial areas. There was no discernible change in concentration or isotopic composition of Pb in surface soil or vegetation over the decade since the ban on the sale of leaded petrol. There was an order of magnitude decrease in Pb concentrations in road dust over the study period, but petrol Pb persisted at up to 43% of the total Pb concentration in 2010. Similar concentrations and spatial distributions of petrol Pb and non petrol Pb in vegetation in both 2001 and 2010, with enhanced concentrations near roads, suggested that redistribution of previously deposited material has operated continuously over that period, maintaining a transfer pathway of Pb into the biosphere. The results for vegetation and soil transects near minor roads provided evidence of a non petrol Pb source associated with roads/traffic, but surface soil samples from the vicinity of a motorway failed to show evidence of such a source

Superconductivity in SrFe_(2-x)Co_xAs_2: Internal Doping of the Iron Arsenide Layers

In the electron doped compounds SrFe_(2-x)Co_xAs_2 superconductivity with T_c up to 20 K is observed for 0.2 < x < 0.4. Results of structure determination, magnetic susceptibility, electrical resistivity, and specific heat are reported. The observation of bulk superconductivity in all thermodynamic properties -- despite strong disorder in the Fe-As layer -- favors an itinerant picture in contrast to the cuprates and renders a p- or d-wave scenario unlikely. DFT calculations find that the substitution of Fe by Co (x > 0.3) leads to the suppression of the magnetic ordering present in SrFe_2As_2 due to a rigid down-shift of the Fe-3d_(x^2-y^2) related band edge in the density of states.Comment: 5 pages, 3 figure

Early diagenetic vivianite [Fe-3(PO4)(2) center dot 8H(2)O] in a contaminated freshwater sediment and insights into zinc uptake: a mu-EXAFS, mu-XANES and Raman study

The sediments in the Salford Quays, a heavily-modified urban water body, contain high levels of organic matter, Fe, Zn and nutrients as a result of past contaminant inputs. Vivianite [Fe3(PO4)2 · 8H2O] has been observed to have precipitated within these sediments during early diagenesis as a result of the release of Fe and P to porewaters. These mineral grains are small (<100 μm) and micron-scale analysis techniques (SEM, electron microprobe, μ-EXAFS, μ-XANES and Raman) have been applied in this study to obtain information upon the structure of this vivianite and the nature of Zn uptake in the mineral. Petrographic observations, and elemental, X-ray diffraction and Raman spectroscopic analysis confirms the presence of vivianite. EXAFS model fitting of the FeK-edge spectra for individual vivianite grains produces Fe–O and Fe–P co-ordination numbers and bond lengths consistent with previous structural studies of vivianite (4O atoms at 1.99–2.05 Å; 2P atoms at 3.17–3.25 Å). One analysed grain displays evidence of a significant Fe3+ component, which is interpreted to have resulted from oxidation during sample handling and/or analysis. EXAFS modelling of the Zn K-edge data, together with linear combination XANES fitting of model compounds, indicates that Zn may be incorporated into the crystal structure of vivianite (4O atoms at 1.97 Å; 2P atoms at 3.17 Å). Low levels of Zn sulphate or Zn-sorbed goethite are also indicated from linear combination XANES fitting and to a limited extent, the EXAFS fitting, the origin of which may either be an oxidation artifact or the inclusion of Zn sulphate into the vivianite grains during precipitation. This study confirms that early diagenetic vivianite may act as a sink for Zn, and potentially other contaminants (e.g. As) during its formation and, therefore, forms an important component of metal cycling in contaminated sediments and waters. Furthermore, for the case of Zn, the EXAFS fits for Zn phosphate suggest this uptake is structural and not via surface adsorption

CURRICULUM VITAE - JEROME NRIAGU

Updated curriculum vitae (November 2020)http://deepblue.lib.umich.edu/bitstream/2027.42/163513/2/CURRICULUM VITAE - JEROME NRIAGU (OCTOBER 2020).pdfSEL

Mercury pollution from the past mining of gold and silver in the Americas

The development of the patio amalgamation process into an industrial scale operation in 1554 stimulated the massive production of silver in the New World but left behind an unprecedented quantity of mercury pollution. The annual loss of mercury in the silver mines of Spanish America averaged 612 tonnes/year (range 292-1085 tonnes/year) between 1580 and 1900. The production and importation of mercury into the United States ranged from 268 to 2820 tonnes/year and averaged ~1360 tonnes/year between 1850 and 1900. Approximately 90% of the mercury consumed in the United States during this period was employed in gold and silver extraction. The cumulative losses of mercury to the environment due to the production of precious metals in the Americas totalled ~257 400 tonnes, with 196 000 tonnes dispersed in South and Central America and 61 380 tonnes in the United States. Approximately 60-65% of the mercury lost is believed to have been released to the atmosphere, suggesting that gold and silver mines were a dominant source of atmospheric mercury pollution. Because of its high volatility, any deposited mercury can readily be re-emitted to the atmosphere. The continuing recycling of this large mass of mercury may partly be responsible for the high fluxes of mercury in many parts of North and South America and the high background levels of mercury in the global environment.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/31497/1/0000419.pd

Mechanistic steps in the photoreduction of mercury in natural waters

Elemental mercury accounts for 10-50% of the dissolved mercury in lakes but plays a vital role in the cycling of this element in lacustrine environments. The view is advanced that a large fraction of the Hg(0) is generated by photochemical reactions in the surface waters. Possible mechanisms for the Hg(0) production are discussed including homogeneous photolysis of dissolved Hg species and photoreduction processes involving organic molecules and inorganic particulates in water.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/31336/1/0000246.pd

Atmospheric transport of trace elements and nutrients to the oceans

This paper reviews atmospheric inputs of trace elements and nutrients to the oceans in the context of the GEOTRACES programme and provides new data from two Atlantic GEOTRACES cruises. We consider the deposition of nitrogen to the oceans, which is now dominated by anthropogenic emissions, the deposition of mineral dust and related trace elements, and the deposition of other trace elements which have a mixture of anthropogenic and dust sources. We then consider the solubility (as a surrogate for bioavailability) of the various elements. We consider briefly the sources, atmospheric transport and transformations of these elements and how this results in strong spatial deposition gradients. Solubility of the trace elements also varies systematically between elements, reflecting their sources and cycling, and for some trace elements there are also systematic gradients in solubility related to dust loading. Together these effects create strong spatial gradients in inputs of bioavailable trace elements to the oceans, and we are only just beginning to understand how these affect ocean biogeochemistry

Environmental injustice and childhood lead exposure in peri-urban (ger) areas of Darkhan and Erdenet, Mongolia

Abstract Background The ger (“tent city”) areas in Mongolia are a product of rapid urbanization and transitional economic development combine with lack of institutional, administrative and financial capacity of governments to cope with the pace. These areas have become traps for inequities in social and environmental services and the associated effects on human health. Disparities in childhood lead exposure in such communities are largely unexplored. Methods We measured the concentrations of lead in blood of children, aged 4–7 years, in Erdenet (Orkhon Province) and Darkhan (Darkhan-Uul Province), the second and third largest cities in Mongolia. A survey instrument was used to gather information on influencing factors on lead exposure and the Strengths and Difficulties Questionnaire (SDQ) was used to assess a spectrum of behavioral problems among the children. Results The mean blood lead level (BLL) of children in the two cities was found to be 3.8 ± 2.6 μg/dL (range: < 1.5–17.2 μg/dL) and 27.8% of the children had BLLs ≥5 μg/dL. Average BLL of children in Erdenet (a mining center) was significantly higher than that for children in Darkhan, and there was statistically significant difference between average BLL of children who live in ger district (4.2 ± 2.8 μg/dL) compared to those of children in housing units within the city (3.2 ± 2.4 μg/dL). In spite of the low values, BLLs was significantly associated with a number of effects on the spectrum of behavioral disorders, specifically with the scores for hyperactivity, conduct disorder and pro-social behavior. Conclusions This study shows that childhood lead poisoning is common especially in ger communities of the urban areas of Mongolia. It contributes evidence showing that BLL low as 3.8 μg/dL can selectively activate some effects from a spectrum of likely behavioral disorders in children.https://deepblue.lib.umich.edu/bitstream/2027.42/147734/1/12889_2019_Article_6486.pd