Deriving nitrogen critical levels and loads based on the responses of acidophytic lichen communities on boreal urban Pinus sylvestris trunks

Abstract

The deposition of reactive nitrogen (N) compounds currently predominates over sulphur (S) deposition in most of the cities in Europe and North America. Acidophytic lichens growing on tree trunks are known to be sensitive to both N and S deposition. Given that tree species and climatic factors affect the composition of epiphytic lichen communities and modify lichen responses to air pollution, this study focused on the impact of urban air pollution on acidophytes growing on boreal conifer trunks. The study was performed in the Helsinki metropolitan area, southern Finland, where annual mean nitrogen dioxide (NO) concentrations range from 4-5μgm to >50μgm. In addition, background forest sites in southern and northern Finland were included. The results demonstrated elevated N contents (≥0.7%) in Hypogymnia physodes and Platismatia glauca at all the sites where the species occurred. In the Helsinki metropolitan area, a higher frequency of green algae+Scoliociosporum chlorococcum and reduced numerical frequencies of other indicator lichen species (e.g. Pseudevernia furfuracea, Bryoria spp., Usnea spp.) were associated with elevated atmospheric concentrations of NO and particulate matter containing N, as well as elevated concentrations of inorganic N in bark. The N isotope values (δN) of lichens supported the uptake of oxidized N mainly originating from road traffic. Sulphur dioxide (SO) also negatively affected the most sensitive species, despite the current low levels (1-4μgmyr). Critical levels of 5μgNOmyr and 0.5μgNHmyr, and a critical load of 2-3kgNhayr are proposed for protecting the diversity of boreal acidophytes. This study calls for measurements of the throughfall of various N fractions in urban forest ecosystems along precipitation and temperature gradients to verify the proposed critical levels and loads.

Mining association rules between lichens and air quality to support urban air quality monitoring in Nigeria

“…The association rules found for the genera Pyxine , Physcia and Lecanora identified them as tolerant to heavy pollution (PM, SO 2 and NO 2 ), thus relevant as bioindicators of poor air quality. This was in agreement with the findings of Conti and Cecchetti [ 9 ], Lewis [ 16 ], Davies, Bates [ 21 ], Yatawara and Dayananda [ 44 ], Wolseley and Aguirre-Hudson [ 47 ], Gadsdon, Dagley [ 48 ], Sujetovienė [ 49 ], Manninen [ 50 ], Asta, Erhardt [ 51 ] which identified them as tolerant to heavy pollution found across heavily disturbed sites e.g., urban centres and roadsides. The genera Candelaria , Diorygma and Parmotrema were also found to be N-tolerant and PM-tolerant, thus indicative of poor air quality.…”

Dog Urine Has Acute Impacts on Soil Chemistry in Urban Greenspaces

“…Based on the average dogownership rate for Finland (∼22%), we estimate that dogs living in Helsinki, the capital of Finland, may produce as much as 15 kg N ha −1 annually. This is comparable to atmospheric deposition, which is estimated to be 2.1-25 kg total dissolved inorganic nitrogen ha −1 yr −1 (Manninen, 2018). However, dog-deposition N is unlikely to be homogeneous across the urban area, and likely represents an even more significant impact within a particular area of greenspace (see Paradeis et al, 2013).…”

Analyses of the brown stain on the Parthenon Centaur head in Denmark

“…The radiofrequency power was 1.30 kW, plasma Ar gas flowrate was 16.5 L min −1 , auxiliary gas flowrate was 1.65 L min −1 , and sheath gas flowrate was 0.18 L min −1 . The following isotopes were measured without skimmer gas: 23 Na, 27 Al, 31 P, 44 Ca, 49 Ti, 52 Cr, 55 Mn, 57 Fe, 65 Cu, 66 Zn, 75 As, 88 Sr, 118 Sn, 121 Sb, 208 Pb, 232 Th, and 238 U. The analysis mode used was peak hopping using 3 points per peak.…”