Weathering Processes of Asbestos‐rich Serpentinitic Sediments

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Abstract
Asbestos‐rich serpentinitic sediments weather rapidly in acid environments and in the process trace metals are released and smectite clays are formed in the soils. A study was carried out in the Sumas River Basin in northwestern Washington State, where a landslide has exposed asbestos‐rich serpentinitic rocks. Between 1975 and 1985 the river draining the landslide has flooded several agricultural fields and on several occasions sediments that are rich in chrysotile asbestos were deposited. The analysis of soil samples from the inundated sites revealed that Ni, Cr, Co, Mn, and Mg were very high in the sediments and leached into the lower more acidic soil horizons. Laboratory extraction experiments were carried out in water and organic acid media. Under neutral and alkaline conditions little chemical breakdown was observed, but in the presence of citric and oxalic acid more than 50% of Ni and Cr is removed by artificial weathering at room temperature. At the same time Mg is removed from the asbestos fiber structure as shown by the energy dispersive x‐ray spectroscopy (EDX) analysis.