Characterisation of the organic components of peat and implications for the binding of toxic trace elements

Abstract

We aimed to determine the distribution of toxic elements amongst the organic components of peat collected from raised bogs located in the Arkhangelsk region of Russia, and thus to gain new insights about the ability of peat to accumulate these elements. We separated peat samples into four fractions (bitumen, humin, humic acids (HA) and fulvic acids (FA)) using phased liquid-liquid extraction. We found that humin was the main component of the peat and its proportion varied from 87.5 % to 90.0 % of total mass. HA, FA and bitumen accounted for 1.7–5.7 %, 2.1–3.8 % and 3.8–5.2 % of the total mass of peat, respectively. Using spectroscopic techniques we found that the humin, HA and FA contained significant concentrations of carboxylic and amino groups capable of forming chemical bonds with elemental ions. Elemental concentrations in the peat fractions were analysed using inductively coupled plasma mass spectrometry (ICP-MS), focusing on the toxic elements arsenic (As), cadmium (Cd), chromium (Cr), mercury (Hg), lead (Pb) and uranium (U). FA was the most active component in terms of binding trace elements in the peat, while the bituminous fraction had the lowest sorption capacity for all of the elements observed. The accumulation of toxic ions was dependent on the presence and concentration of active chemical centres and proceeded according to the chemisorption mechanism.

Keywords

• bitumen
• fulvic acids
• humic acids
• humin
• icp-ms
• ilas
• nmr
• raised bog
• spectroscopy