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In this work for the first time data from two twin stations (Barcelona,urban background, and Montseny, regional background), located in the northeast (NE) ofSpain, were used to study the trends of the concentrations of differentchemical species in PM10 and PM2.5 along with the trends of thePM10 source contributions from the positive matrix factorization (PMF)model. Eleven years of chemical data (2004–2014) were used for this study.Trends of both species concentrations and source contributions were studiedusing the Mann–Kendall test for linear trends and a new approach based onmulti-exponential fit of the data. Despite the fact that different PMfractions (PM2.5, PM10) showed linear decreasing trends at bothstations, the contributions of specific sources of pollutants and of theirchemical tracers showed exponential decreasing trends. The different typesof trends observed reflected the different effectiveness and/or time ofimplementation of the measures taken to reduce the concentrations ofatmospheric pollutants. Moreover, the trends of the contributions ofspecific sources such as those related with industrial activities and withprimary energy consumption mirrored the effect of the financial crisis inSpain from 2008. The sources that showed statistically significant downwardtrends at both Barcelona (BCN) and Montseny (MSY) during 2004–2014 weresecondary sulfate, secondary nitrate, and V–Ni-bearing source. The contributions from these sources decreasedexponentially during the considered period, indicating that the observedreductions were not gradual and consistent over time. Conversely, the trendswere less steep at the end of the period compared to the beginning, thuslikely indicating the attainment of a lower limit. Moreover, statisticallysignificant decreasing trends were observed for the contributions to PM fromthe industrial/traffic source at MSY (mixed metallurgy and roadtraffic) and from the industrial (metallurgy mainly) source at BCN. These sources were clearly linked with anthropogenicactivities, and the observed decreasing trends confirmed the effectiveness ofpollution control measures implemented at European or regional/local levels.Conversely, at regional level, the contributions from sources mostly linkedwith natural processes, such as aged marine and aged organics, did not show statistically significant trends. The trends observedfor the PM10 source contributions reflected the trends observedfor the chemical tracers of these pollutant sources well

Trends analysis of PM source contributions and chemical tracers in NE Spain during 2004–2014: a multi-exponential approach