Dust collection potential and air pollution tolerance indices in some young plant species in arid regions of Iran

Abstract

Abstract: Dust is one of the main environmental challenges in most arid zone cities of Iran. Tree plantation and forest belts can provide a cost-effective and eco-friendly solution to mitigate dust pollution. Air pollution tolerance index (APTI) based on a combination of total chlorophyll (TChl), relative water content (RWC), ascorbic acid (AsA), and leaf pH is considered as one of the most important means for determining sensitive and tolerant plant species for greening. The present study aimed to evaluate the dust capturing efficiency and APTI of Fraxinus rotundifolia Mill., Morus alba L., Celtis caucasica Willd., and Melia azedarach L., four tree species commonly used in urban green areas of most cities in Iran. As a completely randomized design, 256 saplings were grown in four plastic sheets (64 saplings of four species in each chamber) and the dust was applied at concentrations of 0, 300, 750, and 1500 μg m-3 once a week for 70 days. The results revealed that dust accumulation was greatest in the 750 and 1500 μg m-3 treatment in the following order: M. alba > C. caucasica > F. rotundifolia > M. azedarach. In all species, pH, RWC, AsA, and TChl diminished with increasing dust concentration. A decline in APTI of 0 to 1500 μg m-3 was observed in all species. At 750 μg m-3, only M. alba was tolerant to dust and the other species were intermediate. At 1500 μg m-3, M. alba and M. azedarach showed to be intermediate while two other species were sensitive. The greatest relationship was found between APTI and RWC (R2= 0.85), followed by APTI and AsA (R2 = 0.82). Although C. caucasica showed a high capacity for dust accumulation at 1500 μg m-3, it was found to be sensitive and can, therefore, be used as a dust pollution bioindicator. F. rotundifolia and C. caucasica are not suitable for plantation in urban green spaces where dust concentration is 1500 μg m-3. M. alba appeared to be a tolerant species adaptable to arid urban environments with a potential for reducing dust levels by sinking its particles.