ANNEX VSupplementary provisions
ANNEX V OPTIONAL INDICATORS FOR MONITORING AIR POLLUTION IMPACTS REFERRED TO IN ARTICLE 9 (a) for freshwater ecosystems: establishing the extent of biological damage, including sensitive receptors (microphytes, macrophytes and diatoms), and loss of fish stock or invertebrates: the key indicator acid neutralising capacity (ANC) and the supporting indicators acidity (pH), dissolved sulphate (SO 4 ), nitrate (NO 3 ) and dissolved organic carbon: frequency of sampling: from yearly (in lake autumn turnover) to monthly (streams). (b) for terrestrial ecosystems: assessing the soil acidity, soil nutrients loss, nitrogen status and balance as well as biodiversity loss: (i) the key indicator soil acidity: exchangeable fractions of base cations (base saturation) and exchangeable aluminium in soils: frequency of sampling: every 10 years; supporting indicators: pH, sulphate, nitrate, base cations, aluminium concentrations in soil solution: frequency of sampling: every year (where relevant); (ii) the key indicator soil nitrate leaching (NO 3,leach ): frequency of sampling: every year; (iii) the key indicator carbon-nitrogen ratio (C/N) and the supporting indicator of total nitrogen in soil (N tot ): frequency of sampling: every 10 years; (iv) the key indicator nutrient balance in foliage (N/P,N/K, N/Mg): frequency of sampling: every four years. (c) for terrestrial ecosystems: assessing ozone damage to vegetation growth and biodiversity: (i) the key indicator vegetation growth and foliar damage and the supporting indicator carbon flux (C flux ): frequency of sampling: every year; (ii) the key indicator exceedance of flux-based critical levels: frequency of sampling: every year during the growing season.