Saharan versus local influence on atmospheric aerosol deposition in the southern Iberian Peninsula: Significance for N and P inputs

Abstract

A novel methodology was used to evaluate the contribution of Saharan dust to the atmospheric deposition of particulate material (PM), total phosphorus (TP), and total nitrogen (TN) in the southeastern Iberian Peninsula. Dry and wet aerosol depositions were measured weekly during two 1 year periods at one site and simultaneously during spring-summer of the same years at two other sites (intersite distance of 40 km). Statistical relationships among depositions at the different sites permitted differentiation of Saharan dust inputs from locally derived dust. PM and TP depositions were synchronous among the three study sites; the synchrony was elevated during periods of Saharan intrusions (evaluated by air mass retrotrajectories analyses), but no temporal correlation was observed during periods without Saharan intrusions. According to analysis of variance results, PM and TP depositions were both significantly affected by Saharan intrusions. During weeks with Saharan intrusions, PM deposition increased around 85% above background levels, with no differences among the three sites, while TP deposition increased by 1.1 μmol TP m À2 d À1 , i.e., 29% to 81% above background levels depending on the site. There were no correlations or differences in TN deposition among sites or as a function of Saharan intrusion periods. The annual contribution of PM and TP from Saharan dust was 75 kg ha À1 and 0.07 kg P ha À1 , respectively, which can be considered a genuine input for the ecosystems in this area. This novel approach is likely to be valid in any area in the world under atmospheric deposition of long-range transported material.

Deposition rates of viruses and bacteria above the atmospheric boundary layer

“…Synchrony in atmospheric deposition among distant sites is used as a signature of meteorological forcing and longrange dispersal [10,24]. Indeed, total deposition rates (i.e., sedimentation in dry collectors plus atmospheric washout in wet collectors) of viruses at OSN and VSN were synchronous (i.e., positively correlated) (r = 0.95, p = 0.000, n = 12) in 2008 ( Fig.…”

“…The collectors were installed in 2008 to determine the synchrony (temporal coherence) between sites. Synchrony verifies long-range transport of material vs. local sources of aerosols [10,24]. Dry and wet-deposition buckets were collected every 14 days during 2007 (only at the OSN site), and every 7 days during 2008 (at both sites).…”

“…Below this boundary layer, in the lower part of the troposphere, vertical mixing processes influence atmospheric deposition and account for most local * Isabel Reche ireche@ugr.es * Curtis A. Suttle suttle@science.ubc.ca deposition. In contrast, above this boundary layer is the free troposphere; material entrained in this layer is typically subject to long-range transport [10]. Viruses and bacteria are usually not air-dispersed as free particles, but are attached to soil-dust or marine organic aggregates [11,12].…”

Alpine bogs of southern Spain show human-induced environmental change superimposed on long-term natural variations

“…According to our simulations, the whole trend of this proxy shows moderate correlations with the NAO index (Supplementary Table S6 ). However, this correlation declines during the last ∼300 years, pointing to a change in aeolian input features likely caused by either recent major variations in Saharan dust composition 23 , 51 , a higher local dust contribution 52 , or some combination.…”

Particulate Matter Fluxes in a Mediterranean Mountain Forest: Interspecific Differences Between Throughfall and Stemflow in Oak and Pine Stands

“…They represented more than half of the total PM reaching the study area, even though they only accounted for 16% of the events. On the Iberian peninsula, African intrusions usually occur in spring-summer (Castillo et al, 2017), but, as observed here, sporadic intrusions may occur throughout the year, leading to disproportionate outbursts of PM on specific days with significant inputs of minerals such as phyllosilicates, quartz, or calcite (Lequy et al, 2018) and nutrients, particularly phosphorous, which in some ecosystems could be a limiting factor (Morales-Baquero & Pérez-Martínez, 2016). Total PM inputs increased with rainfall due to enhanced wet deposition and the redistribution of previously dry-deposited particulate material (Grantz et al, 2003).…”