Peat refers to the remains of plants which utilised atmospheric carbon and were deposited after death in lake or swamp deposits. Often peaty deposits are acidic therefore pretreatments involving acid washing is unnecessary. In neutral conditions however, a potential contaminating problem may occur due to mobile humic remains percolating down through the profile. Also, the penetration of roots downwards may be a causal factor in dates of peat being too young. One method to reduce this problem is to wet seive the peat and divide it into coarse and fine fractions; the coarse fraction being more likely to incorporate non-contemporaneous intrusive rootlets. Physical and chemical pretreatment methods, then, may need to be used to provide accurate radiocarbon dates. In general peat is a very useful material for radiocarbon work.