Characterization of seawater extractable organic matter from bark compost by TMAH-py-GC/MS

The steel slag/compost fertilizer containing soluble form of iron has been evaluated for restoring barren coastal ground. While humic substances in the compost have been believed to be carriers for supplying iron to such coastal land, they become coagulated and/or flocculated in seawater. Thus, the focus of the study was on seawater extractable organic matter (SWEOM) from the compost that could function as a chelator of iron. Structural features of a novel organic fraction from the compost, SWEOM, were characterized by TMAH-py-GC/MS and the result were compared with those for humic (HA) and fulvic (FA) acids from the same origin. The TMAH-py-GC/MS analyses provided information on the structural characteristics for HA, FA and SWEOM. FA contained high amount of nitrogen-containing pyrolysate compounds, which were likely derived from saccharides and RNA. The large amounts of methoxybenzenes and hydroxybenzenes, which were originated from lignin, were also identified in the HA. For SWEOM, the percentages of fatty acid pyrolysate compounds were significantly larger than the corresponding values for HA and FA. An acidic functional group analysis indicated that the levels of carboxylic groups in SWEOM were lower than those in HA and FA, suggesting that the fatty acid pyrolysate compounds were produced as the result of the cleavage of ester-linkages.

► The wood bark compost is utilized for the fertilizer to restore barren coasts.
► The SWEOM fraction in the compost was characterized by TMAH-py-GC/MS.
► The higher levels of fatty acid pyrolysates were detected in the SWEOM fraction.
► They can be attributed to the cleavage of lipid esters in the compost via pyrolysis.