Premium
Cation exchange properties of soils derived from lignite ashes
Author(s) -
Zikeli Sabine,
Kastler Michael,
Jahn Reinhold
Publication year - 2004
Publication title -
journal of plant nutrition and soil science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.644
H-Index - 87
eISSN - 1522-2624
pISSN - 1436-8730
DOI - 10.1002/jpln.200421361
Subject(s) - cation exchange capacity , chemistry , silt , oxalate , environmental chemistry , weathering , organic matter , soil water , ammonium oxalate , mineralogy , geology , soil science , geochemistry , inorganic chemistry , organic chemistry , paleontology
In Saxony‐Anhalt, Germany, an area of about 6000 ha is covered by lignite‐ash‐derived substrates. In some cases, pollutants like heavy metals or toxic organic compounds had been disposed of together with the lignite ashes. For this reason, we assessed factors influencing the cation exchange capacity (CEC) of lignite‐ash substrates exposed to natural weathering. We chose four research sites reflecting the different methods of disposal: two dumped landfills and two lagooned ashes of different ages. After determining the CEC at pH 8.1 (CEC pot ), we evaluated the influence of the content of silt and clay and the content of total organic C. As lignite‐ash‐derived substrates are rich in oxalate‐extractable Si, Al, and Fe, we performed an oxalate extraction and determined afterwards the CEC pot to assess the contribution of oxalate‐soluble compounds to the CEC pot . Moreover, we determined the variable charge of selected samples at pH values ranging from 4 to 7. The lignite‐ash‐derived soils had a high CEC pot with means ranging from 25.1 cmol c kg –1 to 88.8 cmol c kg –1 . The influence of the parent material was more important than the degree of weathering. The content of total organic C consisting of pedogenic organic matter and coked lignite particles together with the content of silt and clay played a statistically significant role in determining the CEC. Another property that influenced the amount of CEC in medium textured lignite ashes was the content of oxalate‐soluble silica and aluminum. After oxalate extraction, they lost about 30% of their CEC due to the dissolution of oxalate‐soluble compounds. In coarse textured lignite ashes, oxalate extraction led to higher amounts of CEC, probably due to an increase of surface area resulting either from the disintegration of particles or from etching caused by insufficient dissolution of magnetite and maghemite. Moreover, lignite‐ash‐derived substrates exhibit a high amount of pH‐dependent charge. The CEC decreased by 40% in a topsoil sample and by 51% in a subsoil sample as the pH declined from 7 to 4.