Soil Organic Carbon Signature under Impervious Surfaces

While impervious surface expands with global urbanization, understanding the quality and quantity changes of soil organic carbon (SOC) under impervious surfaces is essential to assess the impacts of urbanization on the SOC pool and cycling. By comparing soils under impervious surfaces with surface and subsurface soils from adjoining open areas, we present a systematic study on the SOC signature under impervious surfaces. SOC concentration barely changed when comparing soils under impervious surfaces with subsurface soil from the nearby open area; however, the depletion on SOC was 35–62% when it was compared with surface soils. Regardless of comparison with surface or subsurface soils, bulk-level 13C NMR spectra and specific molecular biomarkers showed a depletion in carbohydrates and an increase in aromatics in SOC composition. Such an alteration was greater with coverage by concrete slabs than simulated home structures built on crawl spaces and was greater as the coverage duration of residential home structures increased. Long-term coverage of residential home structures suppressed microbial degradation and selectively increased the sequestration of plant suberin- and lignin-derived carbon, which would likely increase the residence time of SOC. This study highlights a possible impact of urbanization on the SOC signature and emphasizes that biogeochemical impacts on SOC vary with the type of impervious surface and coverage time.