Litter in French urban areas-part 1: composition, sources, and spatio-temporal variations on urban surfaces.

Urban areas concentrate on human activities that generate large amounts of waste. A small fraction is mismanaged and ends up on urban surfaces and eventually in waterways. The fraction reaching waterways is usually estimated using poorly constrained data, while litter density on urban surfaces and its subsequent transfer dynamics are also poorly documented. This study provides new insights into litter composition, sources, and spatio-temporal variations in the urban catchments of Pin Sec and Jules Verne (Nantes, France), which are dominated by industrial/commercial, collective, and individual housing areas. Regular litter collection on selected street sections was combined with visual counting of street litter (> 1 cm). In total, 50.8 kg (dry weight) of litter were collected and 232,217 items were counted, mainly smoking and food consumption-related items. Litter densities ranged between 40,000 and 452,000 items/km depending on local activities, item mobility, and land use as a driver of road and foot traffic. A median litter accumulation rate of 7 g/inhabitant/day was estimated, suggesting that 0.6% of the total amount of waste generated in public places is mismanaged. Results over space show that litter is strongly correlated with land use and that litter accumulation is promoted in green spaces. Results over time show that litter stock is quickly renewed and that items may have long residence time on urban surfaces.