Pollution biomonitoring in the Delamere Forest, N. Cheshire by XRF analysis of Scots Pine (P. sylvestris L.)

• Main Author: Inman, Malcolm S.
• Published: University of Wolverhampton 2002
• Subjects: 577; Acid rain
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.271283

Chlorosis and premature loss of pine needles was observed in the Delamere Forest, N. Cheshire in late 1992. Fears that the local environment had suffered, and was continuing to suffer, from acid rain or mist 'episodes' as a result of airborne pollutants, led to an analysis of pine needles for total foliar element concentrations in early 1994. Analysis by X-ray Fluorescence Analysis (XRF) revealed levels of foliar sulphur (0.35%) and chloride (0.32%) that suggested deposition of these chemicals as a result of emissions from nearby sources, including a local power station , Ince 'B', a scenario later confirmed by the local environment agency. A monthly programme designed to monitor tree health in Delamere Forest in relation to local levels of atmospheric S02 took place between June 1994 and April 1996, using fixed populations of Scots Pine (P. sylvestris L.) and Corsican Pine (P. nigra var. maritima (Ait.) Melville) to differentiate between short-term acute pollution events and long-term chronic ambient deposition, and to attempt to pinpoint pollution sources. The results revealed complex seasonally affected inter-relationships between atmospheric (dry deposited) sulphur dioxide, rainfall, wind direction and fluctuations in concentrations of foliar elements such as sulphur and magnesium. Average monthly atmospheric S02 levels during this programme were 20 ug/m-3 and foliar S 0.096% total dry weight. The average foliar magnesium level was low at 0.02%. Peaks of atmospheric SO2 were recorded of over 100 ug/m-3, with a maximum of 127 ug/m-3. The initial findings were used as part of a local governmental enquiry that contributed to the decision process which eventually led to the eventual closure of Ince 'B' in 1997. In order to monitor any subsequent changes in tree health as a result, further sampling took place from June 1998 to February 1999. Atmospheric sulphur dioxide levels fell significantly after the closure of of the power station (average 9l ug/m-3) and this change in air quality was reflected in a similarly significant fall in overall concentrations of foliar sulphur (average 0.064% total dry weight). Foliar Mg levels had risen during this period to 0.032%. Recent observations of continued damage to pine foliage in Delamere suggested that although the fall in atmospheric S02 in this area and the subsequent improvement in air quality had followed national trends, Delamere Forest has an ongoing health problem derived from other locally emitted atmospheric pollutants including sporadic emissions of chlorine. It is likely, due to the nature and close proximity of petro-chemical industries, that other pollutants in the immediate local atmosphere such as ozone and ammonia also influence tree health in Delamere Forest and the surrounding environment. Analysis by XRF clearly demonstrated a quick and accurate method of determining foliar element concentrations that could be used to monitor tree health affected by atmospheric pollution. This technique could successfully be used to identify local pollution sources which could prove important in the light of the reduction in local atmospheric pollution monitoring sites since 1999.