Articles | Volume 16, issue 18
Research article
22 Sep 2016
Research article |  | 22 Sep 2016

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

Marco Pandolfi, Andrés Alastuey, Noemi Pérez, Cristina Reche, Iria Castro, Victor Shatalov, and Xavier Querol

Abstract. In this work for the first time data from two twin stations (Barcelona, urban background, and Montseny, regional background), located in the northeast (NE) of Spain, were used to study the trends of the concentrations of different chemical species in PM10 and PM2.5 along with the trends of the PM10 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 studied using the Mann–Kendall test for linear trends and a new approach based on multi-exponential fit of the data. Despite the fact that different PM fractions (PM2.5, PM10) showed linear decreasing trends at both stations, the contributions of specific sources of pollutants and of their chemical tracers showed exponential decreasing trends. The different types of trends observed reflected the different effectiveness and/or time of implementation of the measures taken to reduce the concentrations of atmospheric pollutants. Moreover, the trends of the contributions of specific sources such as those related with industrial activities and with primary energy consumption mirrored the effect of the financial crisis in Spain from 2008. The sources that showed statistically significant downward trends at both Barcelona (BCN) and Montseny (MSY) during 2004–2014 were secondary sulfate, secondary nitrate, and V–Ni-bearing source. The contributions from these sources decreased exponentially during the considered period, indicating that the observed reductions were not gradual and consistent over time. Conversely, the trends were less steep at the end of the period compared to the beginning, thus likely indicating the attainment of a lower limit. Moreover, statistically significant decreasing trends were observed for the contributions to PM from the industrial/traffic source at MSY (mixed metallurgy and road traffic) and from the industrial (metallurgy mainly) source at BCN. These sources were clearly linked with anthropogenic activities, and the observed decreasing trends confirmed the effectiveness of pollution control measures implemented at European or regional/local levels. Conversely, at regional level, the contributions from sources mostly linked with natural processes, such as aged marine and aged organics, did not show statistically significant trends. The trends observed for the PM10 source contributions reflected the trends observed for the chemical tracers of these pollutant sources well.

Short summary
The ambient concentration of many air pollutants in Europe has decreased in these last decades thanks to the effectiveness of the pollution control measures implemented at European or regional/local levels. In this work we studied the trends of the concentrations of many different pollutants during the period 2004–2014, reporting on the type of trend, magnitude of the trend, and its statistical significance. Data from two twin sites in NE Spain (regional and urban background) were used.
Final-revised paper