9-year trends of PM 10 sources and oxidative potential in a rural background site in France

Abstract. Long-term monitoring at sites with relatively low particulate pollution could provide an opportunity to identify changes in pollutant concentration and potential effects of current air quality policies. In this study, a 9-year sampling of PM10 (particles with an aerodynamic diameter below 10 µm) was performed in a rural background site in France from February 28, 2012 to December 22, 2020. The Positive Matrix Factorization (PMF) method was used to apportion sources of PM10 based on quantified chemical constituents and specific chemical tracers from collected filters. Oxidative potential (OP), an emerging health-metric that measures PM capability to potentially cause anti-oxidant imbalance in the lung, was also measured using two acellular assays: dithiothreitol (DTT) and ascorbic acid (AA). The contribution of PMF-resolved sources to OP were also estimated using multiple linear regression (MLR) analysis. In terms of mass contribution, the dominant sources are secondary aerosols (nitrate- and sulphate-rich), associated with long-range transport (LRT). However, in terms of OP contributions, the main drivers are traffic, mineral dust, and biomass burning factors. There is also some OP contribution apportioned to the sulphate- and nitrate-rich sources influenced by processes and aging during LRT that could have encouraged mixing with other anthropogenic sources. The study indicates much lower OP values than in urban areas. A substantial decrease (58 % reduction from year 2012 to 2020) in the mass contributions from the traffic factor was found, however, this is not clearly reflected in its OP contribution. Nevertheless, the findings in this long-term study in the OPE site could signal effectiveness of implemented emission control policies, as also seen in other long-term studies conducted in Europe, mainly for urban areas.