Transformation of beech forest litter as a factor that triggers arsenic solubility in soils developed on historical mine dumps

• Published in: Journal of soils and sediments Vol. 18; no. 8; pp. 2749 - 2758
• Main Authors: Karczewska, Anna, Lewińska, Karolina, Siepak, Marcin, Gałka, Bernard, Dradrach, Agnieszka, Szopka, Katarzyna
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01-08-2018; Springer Nature B.V
• Subjects: Aromaticity; Arsenic; Beech; Capacity; Carbonates; Dissolved organic carbon; Dissolved organic matter; Earth and Environmental Science; Ecological risk assessment; Environment; Environmental Physics; Environmental risk; Flooded soils; Forests; Historic sites; Humic Substances in the Environment; Humification; Incubation period; Iron; Litter; Litters (births); Manganese; Mining; Organic matter; Oxides; Parameters; Pore water; Samplers; Soil; Soil moisture; Soil properties; Soil Science & Conservation; Soil suction; Soil water; Solubility; Sorption; Speciation; Spectroscopy; Ultraviolet radiation; Dissolved organic carbon; Organic matter; Arsenic; Dump; Incubation; MacroRhizon; Pore water
• ISSN: 1439-0108; 1614-7480
• DOI: 10.1007/s11368-018-2031-2

Purpose
Soils that develop on the dumps in historical arsenic mining sites contain high concentrations of As thus constituting a serious environmental risk. This study was aimed to examine the changes in arsenic solubility in mine soils as induced by organic matter introduced with forest litter.
Materials and methods
Four large samples of initially developed soils were collected from the dumps remaining in former mining sites and were incubated for 90 days at various moistures: 80% of maximum water holding capacity and 100% (flooded conditions), with and without addition of beech forest litter (BL), 50 g/kg. Soils contained up to 5.0% As. Soil pore water was collected periodically with MacroRhizon suction samplers and examined on As, Mn, and Fe concentrations, pH, Eh, and dissolved organic carbon (DOC). The properties of dissolved organic matter were characterized by UV-VIS spectroscopic parameters A4/A6 and SUVA
254
.
Results and discussion
Application of BL resulted in an intensive release of As from soils, particularly at 100% moisture. As concentrations in soil pore water increased strongly during the first 2 or 4 weeks of incubation and then started to decrease in all cases, except for one flooded soil. As was released particularly intensively from carbonate-containing soils. The mechanisms of As mobilization, including reductive dissolution of Mn and Fe oxides and the competition with DOC for sorption sites on the oxides, were discussed as related to soil properties. Pore water concentrations of DOC were increasing at the beginning of incubation and started to decrease after two or four weeks. Spectroscopic parameters of dissolved organic matter in ZS soils indicated increasing aromaticity and progress of humification.
Conclusions
Forest litter introduced to mine dump soils causes a mobilization of As into soil pore water. This effect, particularly strong in carbonate-rich soils, is apparently related to high concentrations of DOC and usually declines with time, which may be explained by the progress in humification. The relationships between DOC properties and As speciation in soil pore water should be dissected for better interpretation of experimental results.