Environmental Science & Technology

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    Assessing Soil Organic Carbon in Soils to Enhance and Track Future Carbon Stocks
    (MDPI, 2020-08-05) Yang, Yun-Ya; Goldsmith, Avi; Herold, Ilana; Lecha, Sebastian; Toor, Gurpal S.
    Soils represent the largest terrestrial sink of carbon (C) on Earth, yet the quantification of the amount of soil organic carbon (SOC) is challenging due to the spatial variability inherent in agricultural soils. Our objective was to use a grid sampling approach to assess the magnitude of SOC variability and determine the current SOC stocks in three typical agricultural fields in Maryland, United States. A selected area in each field (4000 m2) was divided into eight grids (20 m × 25 m) for soil sample collection at three fixed depth intervals (0–20 cm, 20–40 cm, and 40–60 cm). Soil pH in all fields was significantly (p < 0.05) greater in the surface soil layer (6.2–6.4) than lower soil layers (4.7–5.9). The mean SOC stocks in the surface layers (0–20 cm: 1.7–2.5 kg/m2) were 47% to 53% of the total SOC stocks at 0–60 cm depth, and were significantly greater than sub-surface layers (20–40 cm: 0.9–1.3 kg/m2; 40–60 cm: 0.8–0.9 kg/m2). Carbon to nitrogen (C/N) ratio and stable C isotopic composition (δ13C) were used to understand the characteristics of SOC in three fields. The C/N ratio was positively corelated (r > 0.96) with SOC stocks, which were lower in sub-surface than surface layers. Differences in C/N ratios and δ13C signatures were observed among the three fields. The calculated values of SOC stocks at 0–60 cm depth ranged from 37 to 47 Mg/ha and were not significantly different in three fields likely due to the similar parent material, soil types, climate, and a short history of changes in management practices. A small variability (~10% coefficient of variation) in SOC stocks across eight sampling grids in each field suggests that re-sampling these grids in the future can lead to accurately determining and tracking changes in SOC stocks.
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    Carbon Storage and Potential Carbon Sequestration in Depressional Wetlands of the Mid-Atlantic Region
    (2011) Fenstermacher, Daniel E.; Rabenhorst, Martin C; Environmental Science and Technology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    With recent concern over climate change, methods for decreasing atmospheric levels of greenhouse gasses such as CO2 have been of particular interest, including carbon sequestration in soils that have depreciated levels of carbon from cultivated agricultural crop production. The Delmarva Peninsula contains many Delmarva Bay landforms, which commonly contain wetlands. Five pairs of Delmarva Bays were selected to examine change in carbon stocks following conversion to agriculture and to assess the potential for carbon sequestration if these soils were to be restored hydrologically and vegetatively. A loss of approximately 50 % of the stored soil carbon was observed following the conversion to agriculture. If these agricultural soils were to be restored, the wetland soils within the Delmarva Bay basin are predicted to sequester a total of approximately 11 kg C m-2 and the upland soils of the rim would be expected to sequester a total of approximately 4 kg C m-2.