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Abstract. Newly-formed nanometer-sized particles have been observed at coastal and marine environments world wide. Organic species have so far not been detected in those newly-formed nucleation mode particles. In this study, we applied the ultrafine organic tandem differential mobility analyzer method to study the possible existence of an organic fraction in recently formed coastal nucleation mode particles (d<20 nm) at the Mace Head research station. Furthermore, effects of those nucleation events on potential cloud condensation nuclei were studied. The coastal events were

The charcoal and pollen stratigraphy of an annually laminated sediment of a small lake in eastern Finland (63°109N, 30°589E) was examined, and found to cover a period of 1300 years. The region around the lake is remote and nowadays almost unpopulated. The fire interval around the study lake was 85 years, with a range of 60–134 years during the 900-year period before any major human influence, and the corresponding fire rotation time estimate was c. 130 years. About half of the fires were probably mild surficial fires, leaving most Scots pine alive. Only one extensive, catastrophic fire during the 900-year period was evident. The fires maintained the forest succession cycles before human influence. The abundance of smallest charcoal particles and trends in estimated palaeotemperatures showed congruence, suggesting increased burning in large regions during warmer climatic periods. The charcoal influx values increased markedly from c. ad 1600 onwards due to the commencement of slash-and-burn cultivation in the area. The pollen and charcoal evidence suggests a period of extensive slash-and-burn agriculture from c. ad 1720 to the beginning of the twentieth century. The short fire interval during the slash-and-burning period caused major changes in forest structure: spruce decreased considerably, and pine became the dominant tree in the area. The charcoal influx into the lake has increased since the beginning of the present century despite fire suppression and the charcoal particle-size distribution suggests long distance origin for these particles.

Local fire history covering the entire Holocene period at a dry forest site in North Karelia, eastern Finland (ca. 63°07' N, 30°44' E), was reconstructed on the basis of visible charcoal layers from peat deposits of a small mire basin. Seven points studied along a transect a few metres long provided a record of ancient local forest fires that had scarred the margin of the peat deposit. The charcoal layer records indicate a drastic increase in forest fires about 500 years ago compared with the earlier part of the Holocene period. During the past 500 years, human influence has been extensive in the area, and there have been 9 local fires during that period, while during the previous 9500 years there had been only 34 fires. Between the establishment of spruce (Picea abies (L.) Karst.) 6300 calendar years B.P. and the beginning of significant human influence, the site had burned over at a mean interval of 220–260 years. The data indicate a decrease in fire frequency associated with a warm climate between 9000 and 6300 calendar years BP. This suggests that climatic warming does not necessarily result in increased frequency of forest fires.