Inhibition of particle aggregation in fluvial suspended sediment by formaldehyde

Freshwater fluvial suspended sediment particle size characteristics alter t emporally when allowed to stand, undergoing continuous aggregation to form larger composite particles (aggregates or flocs) that can settle from the w ater column and are stable to hand shaking. Treatments to inhibit the spont aneous aggregation of laboratory prepared and fluvial suspended sediments w ere investigated. A novel method using formaldehyde to fix suspended sedime nt was developed, which inhibited aggregation of the suspended particles. T he formaldehyde-treated particle suspensions formed fragile aggregates on s ettling, but they were redispersed by hand shaking. When assessed by partic le size distribution, photography and turbidity measurements following resu spension, treatments with 2% (v/v) formaldehyde showed little alteration of the initial existing particles or aggregate composition and turbidity. The fixation of fluvial water samples with formaldehyde immediately after coll ection allowed the transportation and storage of the samples containing sus pended sediment for laboratory analysis, weeks after collection. (C) 1999 E lsevier Science Ltd. All rights reserved.