Organic Carbon Speciation in Urban Anthrosols—The Legacy of Historical Waste Management

Abstract

The impacts of waste management on various soils of agricultural and urban lands may last centuries or even millennia; however, generally, most studies tend to focus only on decadal or shorter timescales. This study investigates the characteristic properties of anthrosols in and around the urban settlement of St Andrews (Scotland), in the context of soil management and organic carbon content and speciation. Formed by the repeated application of fresh organic and pyrogenic wastes since the medieval period, these soils provide a 1000-year urban research context based on historical accounts of town waste management. We employed complementary methods of high-field solid-state 13C-CPMAS NMR, in situ magnetic susceptibility measurement, elemental micro-analysis and portable optically stimulated luminescence (OSL). A significant proportion of the soil organic carbon was present as refractory aromatic C structures, including aryl-C moieties. Portable OSL assessment revealed differences in the intensity and rate of sediment accumulation. The medieval urban areas had higher soil phosphorus concentrations, organic carbon content and magnetic susceptibility relative to the extra-urban site located outside of the medieval burgh. The study confirms that specific signatures, including carbon group functionalities, do reveal evidence of such induced long-lasting past anthropogenic soil modifications.