Formation of black carbon rich ‘sombric’ horizons in the subsoil: a case study from subtropical Brazil - Chiapini, Mariane; Schellekens, Judith; Calegari, Marcia Regina; Almeida, Jaime Antonio de; Buurman, Peter; Camargo, Plinio Barbosa de; Vidal Torrado, Pablo (Geoderma, 2018)