Elemental content of lichens of the Point Reyes Peninsula, northern California

The Point Reyes peninsula in northern California is about 45 km northwest of San Francisco and occasionally receives air masses from the city contributing to haze and lowered visibility. Although gaseous pollutants are not a problem, fine particulates containing carbon and other elements are measurable at the park. In this study, five lichen species were sampled along a 40-km linear transect from southeast to northwest from the town of Bolinas at the southern end of the peninsula. Elevated levels of Na and S and the Na/S ratio at localities nearer the ocean confirmed there is a definite marine aerosol influence on lichen elemental content. Elevated potassium and mercury concentrations were also found at high elevation sites that intercept fog. However, arsenic and lead were found to decrease with distance from Bolinas along the transect, suggesting these two elements originate in the fine particulate haze that enters the park from San Francisco. Concentrations of elements were not at enriched levels for other lichen species. A possible local influence of roads on element content needs further study.