Particulate Retention, Transfer and Release by Cut and Potted Christmas Trees

Coniferous species are known for their ability to purify air from particulate matter (PM), yet particulates accumulated during cultivation, transport, and outdoor storage may be transferred indoors. This study assesses the particulate load, subsequent retention, and further accumulation/release of PM by commercially available Christmas trees—Norway spruce (Picea abies (L.) H. Karst.) and Caucasian fir (Abies nordmanniana (Steven) Spach). Trees were examined in two commercial forms and maintained in six typical households (three with cut and potted P. abies, three with cut and potted A. nordmanianna) for 30 days. Measurements at four intervals included concentration dynamics of total PM, PM size fractions, as well as surface vs. in-wax PM ratios and epicuticular waxes on needles. Results showed that potted trees carried substantially higher initial PM loads than cut trees, with P. abies exceeding 200 µg·cm−2, likely due to differences in production and handling. Potted P. abies and cut A. nordmanniana retained large PM fractions more effectively than cut P. abies. In contrast, the fine PM fraction, the most health-relevant, was best accumulated by cut P. abies. Wax-bound PM shares increased time in potted trees and decreased in the cut. Overall, the findings suggest that choosing a Christmas tree is not only an aesthetic preference but a decision with measurable implications for winter indoor air quality.