This study investigated the relationship between population density and microplastic concentration in
local water sources in Northern Virginia. Water samples were collected from the Potomac River, Lake
Anne, and the Occoquan Reservoir, with distilled water used as a control. A total of 60 water samples
were filtered using membrane filters and analyzed under a microscope at 100× magnification to count
microplastic particles. These counts were used to calculate microplastic concentrations in particles per
cubic meter, allowing comparisons between bodies of water surrounded by different population densities.
The hypothesis predicted that areas with higher population density would show higher concentrations of
microplastics due to increased plastic use and waste.
The results showed that the Potomac River had the highest average microplastic concentration, supporting
the hypothesis. Lake Anne showed the lowest concentration, aligning with its lower population density.
However, the Occoquan Reservoir displayed unexpectedly high microplastic levels despite being surrounded
by a less densely populated area, indicating that factors such as runoff, human activity, and water
management also influence microplastic distribution. Overall, the findings suggest that population
density contributes to microplastic pollution, but it is not the only factor affecting microplastic
concentration in freshwater environments.