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Mapping Heavy Metal Deposition across the UK

Mapping Heavy Metal Deposition across the UK. Alan McDonald, Alan Crossley, Eiko Nemitz, Ron Smith and David Fowler Centre for Ecology and Hydrology (Edinburgh). Heavy Metal Deposition Mapping. Aim of project: To generate high resolution maps of metal concentration and deposition in the UK.

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Mapping Heavy Metal Deposition across the UK

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  1. Mapping Heavy Metal Deposition across the UK Alan McDonald, Alan Crossley, Eiko Nemitz, Ron Smith and David Fowler Centre for Ecology and Hydrology (Edinburgh)

  2. Heavy Metal Deposition Mapping Aim of project: To generate high resolution maps of metal concentration and deposition in the UK • Why? • Data used as input to identify critical load exceedances • Quantify atmospheric deposition to agricultural surfaces, and into food chain • Assess level of human exposure in relation to air quality standards • Contribution to validation exercise of European wide measurement and modelling efforts within the UNECE CLRTAP

  3. The Measurement Network • Sites • 10 sites: PM10, rain and mercury • 3 sites: rain only • 2 elevated sites: cloud and rain • Sampling frequencies • PM10: weekly • Rain: weekly (5 sites), 4-weekly (5 sites) and monthly (3 sites) • Cloud: 2-weekly • Analysis • Chemical analysis at CEH Lancaster using ICP-MS (27 metals) • Money limits the number of sites; cost of chemical analysis is high.

  4. Mapping • Calculate annual metal concentration in precipitation and air for each metal at each site (screen for outliers i.e. contamination) and interpolate to obtain concentration maps • Use concentration fields to calculate wet, dry and cloud deposition fields Lead (Pb) Dry Deposition Air Concentration Wet Concentration Wet Deposition Total Deposition

  5. Budgets

  6. Conclusions • Concentration maps show a north-west to south-east gradient • Total deposition of all metals (except Ni and V) exceeds NAEI emissions estimates • Total deposition values do not account for localised sources or urban sites as this is a rural network. We would expect to underestimate the total UK deposition. • Uncertainties: • Screening for outliers – currently we use 2 standard deviations which may screen out good data • Interpolation • Met office rainfall field (to calculate wet deposition) • Seeder-feeder effect (to calculate wet deposition at high altitude)– unknown for metals • Dry deposition to funnel (which will increase rain concentrations)

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