Comparative Study of Conocarpus erectus and Phoenix dactylifera as Plant Biomonitors of Particulate Matter Pollution in Kuwait over Three Land Use Classes

Abstract

Magnetic plant biomonitoring has been proven to be an effective tool in the assessment of air quality. Kuwait presents a unique environment due to its dry desert climatic conditions and prevailing dry deposition patterns that may affect accumulation rates of magnetic mineral particles. This study evaluated two widely distributed ornamental species, buttonwood (Conocarpus erectus) and palm (Phoenix dactylifera) for their effectiveness as biomagnetic monitors over three different land use classes (urban, suburban and industrial land classes). The differences between land use classes were classified by their proximity to major pollution sources as well as population density. Leaf sampling was conducted over various heights and distances from the nearest road. Total leaf saturated isothermal magnetization (SIRM), hard isothermal magnetization (HIRM), hard isothermal magnetization percentage (HIRM%) and s-ratio have been measured. Scanning electron microscopy (SEM) was used to analyze leaf surface micromorphology. It was determined that NRM values are similar for all land use classes and species, ranging from 0.3 to 0.5 μA. Palm leaf overall magnetic concentration was identified to be higher at the industrial land use class than at the urban land use class, indicating high coercivity minerals to magnetically dominate the land use classes. Additionally, total leaf SIRM was determined to be higher at short distances of 0 - 5 meters from the vicinity of the road. The surface rugosity of palm has deep ridges and furrows with ununiform wax projections across the leaf surface, while buttonwood has a smooth wax film with low relief. Differences in leaf micromorphology in addition to plant physiology, justify species magnetic parametric variances. Palm leaf had an average SIRM value that is 120% higher than buttonwood. It has been highlighted that through the application of the magnetic parameter results to spatial distribution maps that there is an association between particulate matter (PM) and the locality of main roads and local services that may experience higher intensities of traffic.