Relative levels of sodium and chloride in white pine needles 30 m from the pavement at the end of the winter in different years.
| Year | Cl | Na | ||
|---|---|---|---|---|
| Site 1 | Site 2 | Site 1 | Site 2 | |
| 1970 | 1.30 | 1.25 | ||
| 1971 | 0.80 | 0.82 | ||
| 1972 | 1.25 | 0.97 | ||
| 1973 | 1.00 | 0.58 | ||
Adapted from Hall et al. (1972) and Lumis et al. (1976).