Odds and ends of atmospheric mercury in Europe and over northern Atlantic Ocean: Temporal trends of 25 years of measurements

The Global Monitoring Plan of the Minamata Convention on Mercury was established to generate long-term data necessary for evaluating the effectiveness of regulatory measures at a global scale. After 25 years monitoring (since 1995), Mace Head is one of the atmospheric monitoring stations with the longest mercury record, and has produced sufficient data for the analysis of temporal trends of Total Gaseous Mercury (TGM) in Europe and the Northern Atlantic. Using concentration-weighted trajectories for atmospheric mercury measured at Mace Head as well as other five locations in Europe, Amderma, Andøya, Villum, Waldhof and Zeppelin we identify the regional probabilistic source contribution factor and its changes for the period of 1996 to 2019. Temporal trends indicate that concentrations of mercury in the atmosphere in Europe and the Northern Atlantic have declined significantly over the past 25 years, at a non-monotonic rate averaging of 0.03 ng m-3 year-1. Concentrations of TGM at remote marine sites were shown to be affected by continental long-range transport, and evaluation of reanalysis back-trajectories display a significant decrease of TGM in continental air masses from Europe in the last two decades. In addition, using the relationship between mercury and other atmospheric trace gases that could serve as a source signature, we perform factorization regression analysis, based on positive rotatable factorization of non-singular matrix to solve probabilistic mass function. We reconstructed atmospheric mercury concentration and accessed the contribution of the major natural and anthropogenic sources. The positive matrix factorization (PMF) reveals that the downward trend is mainly associated with a factor with a high load of long-lived anthropogenic species.

Temporal Variation and Concentration Weighted Trajectory Analysis of Lead in PM10 Aerosols at a Site in Central Delhi, India

Ambient levels of lead (Pb) in PM10 were studied at a site in Central Delhi for the period of one year during day and night. The annual mean concentration of lead has been observed as 625 and 1051 ng/m3 during day and night time, respectively. The seasonal averaged concentrations of Pb have followed the order winter > postmonsoon > summer > monsoon. Highest levels of lead have been observed in winter with 31% samples exceeding the CPCB-NAAQS value as 1000 ng/m3. Lead levels during winter have been found to be 5.7 times higher than in monsoon, which might be attributed to prevailing meteorological conditions and more biomass burning. The low levels of Pb during summer might be attributed to its higher dispersion in the atmosphere. A sharp rise of Pb during postmonsoon might be linked to the local nonpoint sources, more biomass burning, and shifting of boundary layer. However, the higher concentrations of lead were observed during night time in all the seasons of the year as compared to those of the day time. To identify the potential source regions of Pb, Concentration Weighted Trajectories (CWT) have been plotted which showed higher influence of local sources during winter and postmonsoon while showing distant sources during summer.

The Use of Trajectory Cluster Analysis to Evaluate the Long-Range Transport of Black Carbon Aerosol in the South-Eastern Baltic Region

Trajectory cluster analysis and source-receptor models (the potential source contribution function (PSCF), concentration weighted trajectories (CWT), and trajectory source apportionment (TSA)) were applied to investigate the source-receptor relationship for the aerosol black carbon (BC) measured at the coastal site (Preila, 55.55°N, 21.04°E) during 2013. The main sources and paths of advection to the south-eastern Baltic region and its relation to black carbon concentration were identified. The 72 h backward trajectories of air masses arriving at Preila from January to December 2013 were determined and were categorized by clustering them into six clusters. Subsequently, BC levels at Preila associated with each air mass cluster during this period were analyzed. The PSCF and CWT analysis shows that, on high BC concentration days, the air masses commonly originated and passed over southern regions of Europe before arriving at Preila in winter, while a strong impact of wildfires was observed in spring.