The polymers identified for microplastics cannot be traced to a definitive source but can be attributed to a range of land-based and maritime activities. PE and PP were found to be the dominant polymer in both matrices and are ubiquitous in the ocean 51 but also on land . These polymers are also the most commercially produced polymers and are largely used in packaging and other single-use applications and are widely found in wastewater leakage , highlighting the direct relation between plastic use and leak in the environment. Moreover, the population of the metropolitan area, which often encompasses the whole watershed was found to be positively correlated with sediment microplastic concentrations, while the total population agglomeration for coastal areas had a negative correlation with surface water microplastic concentration. Therefore, as rivers are a major input source of microplastics into the ocean , the integrated watershed management practices employed and waste management systems available should be considered for both inland areas along waterways and coastal settlements .