The impact of surfactants on Norfolk Island pines along Sydney coastal beaches since 1973

The current state of health of Norfolk Island pines, Araucaria heterophylla (Salisb.) Franco, on the coast of metropolitan Sydney was evaluated in 1983/84 by surveying 20 trees, in each of six regions, the trees being selected from larger numbers surveyed during 1973/74. It was found that crown density was inversely related to foliage concentrations of Na⁺ and Cl⁻ which were themselves positively correlated. It is thought that this uptake is mediated by surfactants which enter the sea by discharge from coastal sewage outfalls. Since the previous study, crown density has decreased in three of the six sampling regions, these reflecting increased volumes of sewage discharge. In the other three areas, crown densities had not changed significantly.