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

Gold and uranium

No abstract available

Gold and uranium

No abstract available

Microbial respiration as an indication of metal toxicity in contaminated organic materials and soil

The effect of heavy metals on microbial respiration in organic materials used as soil amendments was evaluated to assess the stability of the materials. Solutions of Pb (II), Cu (II) and Zn (II) at rates of 5, 10 and 50 mg metal g<sup>−1</sup> were added to green waste compost, peat, coir and wood bark. Metal toxicity led to a significant decrease in carbon dioxide evolved by the contaminated materials, up to 80% less at the highest rate of addition compared to the untreated material. There was a significant negative correlation between the organic carbon content of an amendment and the inhibition of CO<sub>2</sub> evolution by all three heavy metals. There was also a significant negative correlation between an amendment's cation exchange capacity and the inhibition of CO<sub>2</sub> evolution caused by Cu and Zn. The ability of the organic materials to enhance respiration in a soil from the vicinity of a Pb/Zn mine was also evaluated, by applying them to the soil at rates of 1, 10 and 20%. CO<sub>2</sub> evolution from the contaminated soil was enhanced significantly by the addition of all of the amendments, with coir causing up to 90% enhancement at high levels of addition

Investigation of contaminant metal dispersal from a disused mine site at Tyndrum, Scotland, using concentration gradients and stable Pb isotope ratios

Results are presented for a study of Pb and Zn concentrations and stable Pb isotope ratios for mining wastes, river sediments and Pb-210-dated peat cores from the vicinity of a derelict Pb/Zn mine at Tyndrum in central Scotland. Mining was carried out at Tyndrum between 1741 and 1862 and the original waste dumps were reworked between 1916 and 1925. Little remains of the original buildings and workings and the contemporary distribution and dispersion pathways of the residual waste are poorly defined. The mine and ore processing waste dumps were readily identified as highly polluted, barren areas, with concentrations of up to 21 and 3.4% Pb and Zn, respectively. The Pb in the waste was characterised by a Pb-206/Pb-207 atom ratio of 1.146+/-0004 and a Pb-208/Pb-207 ratio of 2.432+/- 0.007. Significant quantities of waste were also found along riverbanks and in river channel sediments in the vicinity of the mine, with concentrations of up to 5.22% Pb and 2.35% Zn. Concentrations of Pb and Zn in river channel sediments decreased markedly with increasing distance downriver from the mining area. However, the decrease in Pb concentrations in the less than 53 mum fraction was less pronounced, with a relatively high concentration of 0.076% being observed at a distance of 6.5 km from the mine, suggesting significant fluvial transport of this size fraction of waste. The stable Pb isotopic characteristics of the river sediments were consistent with the mine waste being the dominant source, along with minor inputs from local bedrock and vehicle exhaust emissions. The peat core data revealed high levels of Pb deposition throughout the period of the mining operation and very high levels of input in the early 20th century, almost certainly as a result of the reworking of the former waste dumps. As with the river sediments, the isotopic characteristics of the Pb in the peat cores were consistent with a dominant input from the mine waste and minor contributions from bedrock and vehicle exhaust emissions. The results suggest that waste from the mining operation has been a significant source of contaminant heavy metals for several hundred years and continues to be so. The apparent fluvial transport of Pb from the mine site is consistent with previous work suggesting that Tyndrum mine waste is the probable origin of anomalously high levels of Pb deposited in the sediments of Loch Tay, some 25 km to the cast. The study highlights the utility of stable Pb isotope analyses in the investigation of sources and environmental dispersion of contaminant Pb

Metal accumulation in lolium perenne and brassica napus as affected by application of chitosans

The effects of chitosan, a fishery waste-based material, and its derivative glutaraldehyde cross-linked chitosan (chitosan-GLA) on metal uptake by Lolium perenne (perennial ryegrass) and Brassica napus (rapeseed) were studied in a greenhouse pot experiment. Metal uptake by perennial ryegrass was highly dependent on the rate of addition of the chitosans. Low application rate (1% w/w) enhanced metal uptake, whereas 10% (w/w) addition decreased metal uptake. It was estimated that chitosan 1% (w/w) treatment could assist perennial ryegrass to remove approximately 3.2 kg Zn/ha and 0.29 kg Pb/ha. For rapeseed, metal uptake was decreased at all rates of application of chitosans. The ammonium acetate extractable metals in soil decreased following application of chitosans and plant growth