Abstract
In this study, water of the channels and ponds that conduct residual water in two most important cities of Saudi Arabia were assessed to ascertain the influence of the population on the occurrence and pollution characteristics of microplastics (MPs) (> 20 µm in size). Riyadh has 7.6 million inhabitants and is an urban city even though also have industry while Al-Jubail has only 0.78 and is the biggest industrial city. MPs showed an average of 3.2 items/L in Riyadh and 0.2 items/L in Al-Jubail showing a statistically significant difference between both cities. Sampling with a Turton Tow Net of 20 µm mesh, fibers were dominant in all sites (60%). MPs size was mainly distributed between 80 and 250 µm (60%), and their major colors were white (40%), red (25%) and blue (20%). Infrared spectral analysis revealed that most of the selected particles were identified as MPs of polypropylene and polyethylene (48.3%). The risk assessment was carried out using both the hazard index (HI) and the pollution load index (PLI). The results showed that, in this case, the decisive index is the PLI since the main difference in the MPs characteristics between the two cities is their concentration.
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•MPs concentration was established using a Turton Town net of 20 µm mesh.•Fibers white or transparent with a size < 250 µm were dominant.•Population and socioeconomic characteristics can influence MPs abundance.•The composition of microplastics by FTIR was identified as PE, PP, PS and PET.•Quantities of MPs and toxicity of their components in water showed ecological risk.