The United Kingdom national materials exposure programme

In 1986, the National Materials Exposure Programme was set up within the United Kingdom to investigate the effects of acid deposition on buildings and building materials. Thirty sites were chosen, which represented a range of geographical and pollution climates. Each site met a minimum meteorological and pollution monitoring regime (including SO sub(2), NO sub(2)). After four years, other sites were included (with less frequent data collection) and some sites removed. At each site, samples of 3 types of stone, mild steel, painted steel, Cu, Al and galvanised steel were exposed, with some of the stone sheltered from direct precipitation. Samples were removed periodically for analysis and dose-response relations derived for different materials. The empirical relationships derived are in the form of: decay rate = a [SO sub(2)] + b [H super(+)] + c [rainfall] + d. These dose response relations have been used to develop critical load maps for materials for the United Kingdom. Eight years of data have been collected, some for the UNECE task force programme. Laboratory tests using an Atmospheric Flow Chamber were also undertaken. Since the beginning of the programme addition materials have been exposed on some sites including mortars. A further set of eight sites has been used to assess the effects of ozone on a range of organic materials (for example polyvinyl chloride, polycarbonate, sealants). The paper presents up-to-date findings for the programme and confirms the dominance of dry deposition of sulphur dioxide as the main decay process for sensitive materials in areas of significant pollution.