Retention and distribution of copper/chrome/arsenic (CCA) in pressurised sap-displaced UK grown spruce and pine
P D Evans, G M Smith, B King
Increment cores were taken from UK grown Scots pine (Pinus sylvestris L.), Corsican pine (Pinus nigra var. maritima Ait), Sitka Spruce (Picea sitchensis (Bong) Carr), and Norway spruce (Picea abies (L) Karst) distribution poles treated by pressurised sap-displacement using a 1.8% copper, chrome, arsenic (CCA) solution. Each increment core was sectioned radially and the copper, chrome, and arsenic content analysed. All four wood species showed a higher CCA content in the outer sapwood which declined radially towards the centre of the pole. The net preservative retention in the outer sapwood of Scots Pine, Corsican Pine and Norway Spruce was in the range 13-23 kg/m³. The CCA content in the outer sapwood for Sitka spruce was low (in the range 4-7 kg/m³). Little longitudinal variation in CCA content occurred along the length of the poles for the four wood species studied. The concentration of the individual CCA components varied in a radial direction. Chrome and Arsenic concentrations were at a maximum in the outer sapwood in all four wood species whereas Copper tended to be in a maximum concentration in the inner sapwood some 20-40 mm from the pole surface. This effect was particularly noticeable in Scots pine and Corsican pine. It is believed that the preservative gradients reported may be important in determining the performance of treated wood and as such should be taken into account when designing predictive tests of the efficacy of preservative treatments.
Keywords: PINUS SYLVESTRIS; PINUS NIGRA MARITIMA; PICEA SITCHENSIS; CCA; PRESSURE; SAP-DISPLACEMENT; PICEA ABIES; RETENTION; DISTRIBUTION; POLES