Phenanthrene adsorption by soils treated with humic substances under different pH and temperature conditions.
The mobility of phenanthrene (PHE) in soils depends on its sorption and is influenced by either the existing soil humus or exogenous humic substances. Exogenous humic acids (HAs) were added to soil to enhance the amount of soil organic carbon (SOC) by 2.5, 5.0, and 10.0 g kg(-1). PHE desorption of the treated soils was determined at two pH levels (3.0 and 6.0) and temperatures (15 and 25 degrees C). Soil PHE adsorption was related to pH and the type and quantity of added HAs. Humic acid (HA) and fulvic acid (FA) derived from peat had different effects on adsorption of PHE. Adsorption increased at first and then decreased with increasing quantity of exogenous FA. When the soil solution pH (in 0.005 M CaCl(2)) was 4.5 or 3.0, the turning points were 2.5 g FA kg(-1) at pH 3.0 and 5 g FA kg(-1) at pH 4.5. When soil solution pH was 6, the amount of adsorbed PHE was enhanced with increasing exogenous HAs (HA or FA) and amount of adsorption by soil treated with FA was higher than with HA. Adsorption of PHE in the FA treatment at 10.0 g kg(-1) was lower than the controls (untreated soil or treatment with HAs at 0 g kg(-1)) when the soil solution pH was 3.0. This suggests that FA adsorbed by soil was desorbed at low pH and would then increase PHE solubility, and PHE then combined with FA. PHE adsorption was usually higher under lower pH and/or lower temperature conditions. PHE sorption fitted the Freundlich isotherm, indicating that exogenous humic substances influenced adsorption of phenanthrene, which in turn was affected by environmental conditions such as pH and temperature. Thus, exogenous humic substances can be used to control the mobility of soil PAHs under appropriate conditions to decrease PAH contamination.
Ping
Lifeng
L
Soil and Environmental Bioremediation Research Center, State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, China.
Luo
Yongming
Y
Wu
Longhua
L
Qian
Wei
W
Song
Jing
J
Christie
Peter
P
D000327:Adsorption; D001578:Benzopyrans; D006812:Humic Substances; D006863:Hydrogen-Ion Concentration; D010616:Phenanthrenes / Q000737:chemistry*; D011084:Polycyclic Aromatic Hydrocarbons / Q000302:isolation & purification; D012987:Soil / Q000032:analysis*; D012989:Soil Pollutants / Q000302:isolation & purification*; D012995:Solubility; D013696:Temperature
D001578:Benzopyrans; D006812:Humic Substances; D010616:Phenanthrenes; D011084:Polycyclic Aromatic Hydrocarbons; D012987:Soil; D012989:Soil Pollutants; C005023:fulvic acid