Injury Symptoms and Releasing Rates of Inorganic Ions from Pine Needles as Indicators of Atmospheric Pollution in the Canary Islands Forests

Pinus canariensis Chr, Sm. ex DC. samples showing severe damage produced by atmospheric pollution were taken from three locations under the possible influence of the emissions of a fuel-fired power plant in Tenerife. Other samples were taken at four control locations in Tenerife, La Palma and El Hierro (Canary Islands, Spain), distant from local sources of pollution. Injury symptoms were evaluated by visual examination of the needles, and the data were correlated with the releasing rates of inorganic anions and cations from the needles when sonicated under water. For this purpose, the samples were sonicated 4-times during 10 min successive periods while renewing the water layer in between, and the leachates were analyzed by capillary zone electrophoresis. Measurable amounts of K⁺, Na⁺, Ca²⁺, Mg²⁺, Cl^- and SO₄ ^2- were detected. Potassium ions were released in approximately constant or increasing amounts along the sonication series in the control samples, whereas the samples damaged by pollution released larger amounts during the first sonication treatment, and much lower amounts afterwards. Indices which estimated the initial releasing rate of the cations were examinated as possible indicators to evaluate atmospheric pollution. Only the K⁺ index showed a large positive correlation with the brown-reddish decoloration and tip necrosis of the needles. The correlation of the K⁺ index with flecking and steepling of the needles was much lower. After principal component analysis of the autoscaled data, the sampling sites and the variables were projected on the plane of the first and second eigenvectors. Using the visual examination parameters as variables, both without and with addition of the cation indices, the sampling sites appeared in the order of increasing damage along the first eigenvector. Evidence of the effects of long-range transported pollutants was obtained, and no relationship was demonstrated between damage of pine needles and emissions from the power plant.