Effects of a sulphur dioxide episode on trees in the surroundings of a refinery

Abstract

Serious damage symptoms on several trees species around a refinery located in the North of the Basque Country (Spain) were observed in the early May‐93. With the aim to determine the causes of these damages, both the SO₂ and the NO_X concentrations and their relationship with the air masses trajectories, were studied during the period between April 25^th and May 5^th. The results showed that the SO₂ levels reached more than 600 μg m^‐3 on May 2^nd. On that day the wind flows from the Northwest (NW) direction, which coincides with the direction towards the affected area from the refinery. Likewise, the evaluation of the damages symptoms on the trees showed that they could be due to an acute episode of gaseous contamination. Finally, the S0₄ ^2‐’ soluble concentration in the leaves of damaged trees is higher than the one found on trees located in other areas not affected. The SO,²”; soluble concentration decreased from the refinery to distant areas.

Key words:

• SO₃ episode
• refinery
• forest ecosystem
• damage symptoms
• wind direction.