Abstract. Amount, stability, and distribution of black carbon (BC) were studied at four sites of a large peatland ("Witzwil") formerly used as a disposal for combustion residues from households to derive BC displacement rates in the profile. Possible artefacts from thermal oxidation with Differential Scanning Calorimetry (DSC) on BC quantification of C-rich deposits were inferred by choosing three sites from a second peatland with no historical record of waste disposal as a reference ("Seebodenalp"). All sites were under grassland at time of sampling, but were partially cropped in the past at Witzwil. Mean BC contents in topsoils of Witzwil ranged from 10.7 to 91.5 (0-30 cm) and from 0.44 to 51.3 (30-140 cm) mg BC g −1 soil, corresponding to BC/OC ratios of 0.04 to 0.3 (topsoil) and 0.02 to 0.18 (deeper soil). At three sites of Seebodenalp, BC was below the detection limit of 0.4 mg g −1 organic soil, indicating negligible formation of BC during thermal oxidation of peat. 13 C NMR spectra corroborated the high BC contents at Witzwil. The data support a considerable vertical transport of BC given that soils were ploughed not deeper than 30 cm since abandonment of waste application about 50 years ago. The total amount of BC in the Witzwil profiles ranged from 3.2 to 7.5 kg BC m −2 , with 21 to 69 percent of it stemming from below the former ploughing depth. Under the premise of negligible rates of BC consumption since abandonment of waste application, minimum BC transport rates in these peats are 0.6 to 1.2 cm a −1 . The high mobility of BC might be explained by high macropore volumes in combination with occasional water saturation. By means of DSC peak temperatures, different types of BC could be distinguished, with deeper horizons containing BC of higher thermal stability. Application of combustion residues likely involved a mixture of various BC types, of which thermally more stable ones, most likely soots, were preferentially transported downwards.

No abstract

Abstract. Amount, stability, and distribution of black carbon BC were studied at four sites of a large peatland ("Witzwil") formerly used as a disposal for combustion residues from households to derive BC displacement rates in the profile. Possible artefacts from thermal oxidation with Differential Scanning Calorimetry (DSC) on BC quantification of C-rich deposits were inferred by choosing three sites from a second peatland with no historical record of waste disposal as a reference ("Seebodenalp"). All sites were under grassland at time of sampling, but were partially cropped in the past at Witzwil. Mean BC contents in topsoils of Witzwil ranged from 10.7 to 91.5 (0–30 cm) and from 0.44 to 51.3 (30–140 cm) mg BC g−1 soil, corresponding to BC/OC ratios of 0.04 to 0.3 (topsoil) and 0.02 to 0.18 (deeper soil). At three sites of Seebodenalp, BC was below the detection limit of 0.4 mg g−1 organic soil, indicating negligible formation of BC during thermal oxidation of peat. 13C NMR spectra corroborated the high BC contents at Witzwil. The data refer to a considerable vertical transport of BC given that soils were ploughed not deeper than 30 cm since abandonment of waste application about 50 years ago. The total amount of BC in the Witzwil profiles ranged from 3.2 to 7.5 kg BC m−2, with 21 to 69 percent of it stemming from below the former ploughing depth. Under the premise of negligible rates of BC consumption since abandonment of waste application, minimum BC transport rates in these peats are 0.6 to 1.2 cm a−1. The high mobility of BC might be explained by high macro-pore volumes in combination with occasional water saturation. By means of DSC peak temperatures, different types of BC could be distinguished, with deeper horizons containing BC of higher thermal stability. Application of combustion residues likely involved a mixture of various BC types, of which thermally more stable ones, most likely soots, were preferentially transported downwards.

Bewirtschaftungsbedingter Fahrverkehr kann Ackerböden bis in den Unterboden verdichten und ihre Eigenschaften als Pflanzenstandort verschlechtern. In einer Fallstudie wurde der Verdichtungsgrad von zwei Lößflächen benachbarter Betriebe (Schlag A und Schlag B) untersucht, die seit etwa 20 Jahren mit unterschiedlichen Achslasten befahren wurden (maximale Achslasten 4 t bzw. 8,9 t). Als Referenzfläche diente ein nicht befahrener, mit Gras bewachsener Ackerrain. Ziel der Untersuchung war, den Zusammenhang zwischen bewirtschaftungsbedingtem Fahrverkehr und dem Ausmaß der Bodenverdichtung aufzuzeigen. Im Bereich einer Krumenbasisverdichtung in 40 cm Tiefe lag der Bodeneindringwiderstand auf Ackerschlag A höher als unter Gras, aber doch deutlich niedriger als auf Schlag B. Gleichsinnige Unterschiede zeigten Lagerungsdichte und Luftkapazität. Für die auf beiden Flächen maximal auftretenden Achslasten wurde die vertikale Normalspannung als Funktion der Bodentiefe berechnet. Für den verdichtungsempfindlichen Bodenfeuchtebereich ergaben sich in 40 cm Tiefe Werte um 60 kPa auf Fläche A. auf Fläche Bum 130 kPa. Die Summe der während des Anbaus von Blattfrüchten auftretenden Belastungsimpulse – berechnet aus allen zurückgelegten Fahrstrecken und den jeweiligen Gerätegewichten – war für Schlag B um 17% höher als für Schlag A. Auf Schlag A war eine Verdichtungswirkung bis in ca. 40 cm Tiefe nachzuweisen. Auf Schlag B, der vor allem während der Zuckerrübenernte mit hohen Lasten befahren wird, reichte die Wirkung bis in ca. 70 cm. Diese Studie verdeutlicht, daß der Verdichtungszustand von Ackerböden in starkem Maße von der Intensität der Befahrung abhängig ist, welche nicht nur die Höhe der Achslasten, sondern auch Zeitpunkt und Häufigkeit der Überfahrung einschließt.