Impact of point source pollution on nitrogen isotope signatures (δN) of vegetation in SE Brazil.

This study presents novel evidence that N natural abundance can be used as a robust indicator to detect pollutant nitrogen in natural plant communities. Vegetation from the heavily polluted industrial area of Cubatão in São Paulo State, SE Brazil, was strongly N depleted compared to plants at remote sites. Historic herbarium samples from Cubatão were significantly less N depleted than extant plants, indicating that N depletion of vegetation is associated with present-day nitrogen pollution in Cubatão. The heavy load of nitrogenous atmospheric pollutants in Cubatão provides a nitrogen source for plants, and strongly N depleted air NH is likely to contribute to plant and soil N depletion. Epiphytic plants from Cubatão were extremely N depleted (average -10.9‰) contrasting with epiphytes at remote sites (averages -1.0‰ and -3.0‰). Nitrogen isotope composition of vegetation provides a tool to determine input of pollutant nitrogen into plant communities. The strong isotopic change of epiphytes suggests that epiphytes are particularly sensitive biomonitors for atmospheric pollutant nitrogen.