The use of quantified structural descriptors to physically characterise stockpiled milled peat of different genetic origins

Recent research examining water movement in milled peat stockpiles has focu sed on macroscale physical data. Structure is important with respect to wat er movement and storage; the number, shape and size of macropores is though t to be particularly important in influencing by-pass flow. A study of pore structures quantified by image analysis techniques was conducted starting with a field impregnation to produce undisturbed polished blocks from stock piled milled peat of fen and raised bog origins. Samples were prepared in t wo orientations and characterised in two dimensions, parallel and orthogona l to the stockpile surfaces. Milled peat stockpile structure was found to b e layered, with the surface layers typically twice as porous, but with half the number poroids of, the main body of the stockpile. This structure crea ted a discontinuity between surface and sub-surface structures which was th ought to be the result of rain, wind and gravity removing finer particles f rom the surface. Quantified evidence suggested that the milling processes d iffered in detail (smaller pores and finer particles from the fen peat). Th e quantified pore structures were consistent with the current hypothesis re garding milled peat stockpile rewetting mechanisms such as by-pass flow and finger storage. This suggested that structural properties are a more usefu l indication of rewetting mechanisms than a classification based only on pe at density. (C) 2000 Elsevier Science B.V. All rights reserved.