Good Agreement Between Modeled and Measured Sulfur and Nitrogen Deposition in Europe, in Spite of Marked Differences in Some Sites

Atmospheric nitrogen and sulfur deposition is an important effect of atmospheric pollution and may affect forest ecosystems positively, for example enhancing tree growth, or negatively, for example causing acidification, eutrophication, cation depletion in soil or nutritional imbalances in trees. To assess and design measures to reduce the negative impacts of deposition, a good estimate of the deposition amount is needed, either by direct measurement or by modeling. In order to evaluate the precision of both approaches and to identify possible improvements, we compared the deposition estimates obtained using an Eulerian model with the measurements performed by two large independent networks covering most of Europe. The results are in good agreement (bias <25%) for sulfate and nitrate open field deposition, while larger differences are more evident for ammonium deposition, likely due to the greater influence of local ammonia sources. Modeled sulfur total deposition compares well with throughfall deposition measured in forest plots, while the estimate of nitrogen deposition is affected by the tree canopy. The geographical distribution of pollutant deposition and of outlier sites where model and measurements show larger differences are discussed.

Eastern white pine and eastern hemlock growth: possible tradeoffs in response of canopy trees to climate

A warming climate and extended growing season may confer competitive advantages to temperate conifers that can photosynthesize across seasons. Whether this potential translates into increased growth is unclear, as is whether pollution could constrain growth. We examined two temperate conifers - eastern white pine (Pinus strobus L.) and eastern hemlock (Tsuga canadensis (L.) Carrière) - and analyzed associations between growth (476 trees in 23 plots) and numerous factors, including climate and pollutant deposition variables. Both species exhibited increasing growth over time and eastern white pine showed greater maximum growth. Higher spring temperatures were associated with greater growth for both species, as were higher autumnal temperatures for eastern hemlock. Negative correlations were observed with previous year (eastern hemlock) and current year (eastern white pine) summer temperatures. Spring and summer moisture availability were positively correlated with growth for eastern white pine throughout its chronology, whereas for hemlock, correlations with moisture shifted from being significant with current year’s growth to previous year’s growth over time. The growth of these temperate conifers might benefit from higher spring (both species) and fall (eastern hemlock) temperatures, though this could be offset by reductions in growth associated with hotter, drier summers.

Rapid metal pollutant deposition from the volcanic plume of Kīlauea, Hawai’i

Long-lived basaltic volcanic eruptions are a globally important source of environmentally reactive, volatile metal pollutant elements such as selenium, cadmium and lead. The 2018 eruption of Kīlauea, Hawai’i produced exceptionally high discharge of metal pollutants, and was an unprecedented opportunity to track them from vent to deposition. Here we show, through geochemical sampling of the plume that volatile metal pollutants were depleted in the plume up to 100 times faster than refractory species, such as magnesium and iron. We propose that this rapid wet deposition of complexes containing reactive and potentially toxic volatile metal pollutants may disproportionately impact localised areas close to the vent. We infer that the relationship between volatility and solubility is an important control on the atmospheric behaviour of elements. We suggest that assessment of hazards from volcanic emissions should account for heterogeneous plume depletion of metal pollutants.

A Dynamic Analysis Of The Impact Of Air Pollution On The daylight Availability In An Open-plan Office In London

The deposition of air pollutants on glazing can significantly affect the daylight transmittance of building fenestration systems in urban areas. This study presents a simulation analysis of the impact of air pollution and glazing visual transmittance on indoor daylight availability in an open-plan office in London. First, the direct links between glazing visual transmittance and daylighting conditions were developed and assessed. Second, several simple algorithms were established to estimate the loss of daylight availability due to the pollutant deposition at the external surface of vertical glazing. Finally, some conclusions and design strategies to support facade planning at the early design stage of an urban building project were developed.

How alkaline compounds control atmospheric aerosol acidity

The acidity of atmospheric aerosols regulates the particulate mass, composition and toxicity, and has important consequences for public health, ecosystems and climate. Despite these broad impacts, the global distribution and evolution of aerosol acidity are unknown. We used the particular, comprehensive atmospheric multiphase chemistry – climate model EMAC to investigate the main factors that control aerosol acidity, and uncovered remarkable variability and unexpected trends during the past 50 years in different parts of the world. We find that alkaline compounds, notably ammonium, and to a lesser extent crustal cations, buffer the aerosol pH on a global scale. Given the importance of aerosols for the atmospheric energy budget, cloud formation, pollutant deposition and public health, alkaline species hold the key to control strategies for air quality and climate change.