Measurements of atmospheric mercury concentrations in Northwestern and Central Europe - comparison of experimental data and model results

Field experiments were carried out at various sites in Europe to compare ambient air and precipitation concentrations of atmospheric mercury with model data. In addition, ozone and aerosol black carbon concentrations in air were measured simultaneously as input data for validation of the EMEP-based European long-range transport model. Data sets for mercury in air and precipitation, ozone and aerosol black carbon show that the selcted sites range from background conditions for Northwestern Europe to regionally influenced air masses from heavily industrialized Central Europe. Measured 12 h average mercury concentrations in air range from 2.1 ng m"-"3 for Mace Head, Ireland to 8.2 ng m"-"3 for the Halle/Leipzig/Bitterfeld area in former German Democratic Republic. Precipitation concentrations of total mercury from 17 to 460 ng l"-"1 were measured from 1991 to 1993 for the same sites. Experimental data and model results for total geaseous mercury and mercury in precipitation are in good agreement. (orig.)Special print from: Atmospheric Environment (1995) v. 29(22) p. 3333-3344Available from TIB Hannover: RA 3251(95/E/67) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Evidence for possible climatic forcing of late-Holocene vegetation changes in Norfolk broadland floodplain mires, UK.

Plant macrofossil analyses of five peat cores from undisturbed fens in the flood-plain of the Ant Valley of the Norfolk Broadland show the sequence of vegetation development during the last two millennia. Macrofossil assemblages have been grouped into five regional phases and are interpreted largely in terms of the response of the vegetation to changes in sea level, climate and management. Phase 1 represents pre-Roman fen woodland communities (>2000 cal. BP); phase 2 represents salt-marsh communities formed during an estuarine phase in Romano-British times (c. 2000–1600 cal. BP); phase 3 represents ‘tussock-fen’ and carr communities suggestive of drier conditions in the post-Roman to early Medieval period (c. 1600–800 cal. BP); phase 4 represents aquatic communities indicative of wetter conditions from the late Medieval period to c. 300 cal. BP; phase 5 represents communities comparable with present-day vegetation. The biostratigraphic development of the Ant Valley floodplain mires has analogues in climatically induced humification changes of some British ombrotrophic mires, suggesting a response to similar climatic controls. Widespread human interference and control of the fen vegetation may be a relatively recent phenomenon (beginning possibly,400 cal. BP). Peat-accumulation rates in the undisturbed mire sites suggest that the original Medieval turbaries which later flooded to form the Norfolk Broads may have been at least 0.5 m shallower when dug than their present depth. The wide range of environmental conditions experienced by the mires during the last two millennia is of relevance to the development of strategies for their conservation