Evaluation of air pollution tolerance index of urban roadside young leaf and the correlation with its capturing capacity for water-insoluble fine particulate matters

The selection of plant species has been accepted as a crucial factor when developing roadside greenbelts which act as a cost-effective and eco-friendly passive method for the reduction of traffic related particle pollution. Plants growing alongside roads are mostly affected because they are primary recipients to different pollutants and show varied sensitivity and tolerance. Taking this into account, young leaves of eight kinds of common roadside plants (Ligustrum lucidum, Prunus cerasifera, Photinia fraseri, Photinia serratifolia, Nandina domestica, Paeonia suffruticosa Andr., Nerium oleander, and Eriobotrya japonica) in central China were collected and their air pollution tolerance index (APTI) was calculated by assessing four biochemical parameters i.e., relative water content, total chlorophyll content, ascorbic acid, leaf extract pH. The results demonstrated that young leaves of N. oleander and L. lucidum showed higher APTI value (8.90–9.45 and 8.73 to 9.17 respectively) in the three tested springtime month and were the most tolerant species, while young leaves of E. japonica kept to be sensitive (with the APTI value around 5.72 to 8.29) during the whole spring. In addition, inconsistent with previous studies, relative water content other than ascorbic acid was found to be more crucial for young leaves of test plants to be more tolerant to particle pollution in relatively dry condition in spring (r = 0.996 at p < 0.01 level). At last, except significant impact on the capture of PM_2.5, the tolerance of young leaves has limited impacts on their ability to reduce other size fine particle such as TSP and PM₁₀. In summary, N. oleander and L. lucidum are recommended to be used as particle sink when developing urban green belt, and E. japonica is more suitable as a bio-monitor of air quality.