Oxygen isotope ratio (δ18O) and concentrations of Al, Na+, methanesulfonic acid (MSA), SO42-, and selenium (Se) in a continuous series of 70 snow samples from a 3.2-m snow pit at a site in northwestern Greenland were determined using ultraclean procedures.Well-defined depth profiles of δ18O, Al, and sea-salt-Na+ allowed the determination of chronology of the snow pit that spanned approximately 6years from spring 2003 to summer 2009. Se concentrations were at a low pg/g level, ranging from 7.2 to 45pg/g, and exhibited high variability with generally higher values during winter and spring and lower values during summer and fall. Very high crustal enrichment factors (EFc) of Se averaging approximately 26,600 for the entire time period indicate a small contribution from crust dust. High Se/MSA ratios are generally observed in the winter and spring snow layers, in which the Se concentrations were relatively high (>20pg/g). This suggests that a significant component of the Se present in the snow layers is of anthropogenic origin. During the summer season, however, high EFc values are accompanied with low Se/MSA, indicating an increased contribution of marine biogenic sources. Significant correlations between Se, Al, and non-sea-salt SO42- highlight that significant inputs of Se to the snow are likely controlled by the seasonality in the transport efficiency of anthropogenic Se from the source regions to the site. Based on the seasonal changes in Se concentrations, Se/MSA, and Se/S ratios observed in the samples, the input of anthropogenic Se to the site appears to be governed by the long-range transportation of Se emitted from coal combustion in East Asian countries, especially in China.
Bibliographical noteFunding Information:
We thank all personnel in the field for the sampling work carried out during the 2009 NEEM deep ice core drilling campaign. The NEEM project was directed and organized by the Center for Ice and Climate at the Niels Bohr Institute and the Polar Programs office of the US National Science Foundation. The project was supported by funding agencies and institutions in Belgium ( FNRS-CFB and FWO ), Canada ( NRCan/GSC ), China ( CAS ), Denmark ( FIST ), France ( IPEV , CNRS/INSU , CEA and ANR ), Germany ( AWI ), Iceland ( Rannls ), Japan ( NIPR ), Korea ( KOPRI ), Netherlands ( NOW/ALW ), Sweden ( VR ), Switzerland ( SNF ), the UK ( NERC ), and the USA ( US NSF OPP ). This study was supported in Korea by a research grant ( PE15010 ) from the Korean Research Council of Public Science and Technology , and by the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology ( 2012R1A1A2001832 ). The authors wish to thank the anonymous reviewers for providing helpful comments which improved the manuscript.
© 2015 Elsevier B.V.
- Anthropogenic contribution
- Coal combustion
- Short-term variation
- Snow pit