Contrasting microcystin-LR sorption and desorption capability of different farmland soils amended with biochar: Effects of biochar dose and aging time. (1st October 2021) - Yuan, Yue
Abstract: This study explored biochar (BC) amendment effects on microcystin-LR (MCLR) concentration-dependent sorption and sequential desorption (SDE) by diverse soils to assess MCLR-trapping by BC-amended soils. Soil properties varied with rising BC dose and aging time. As aging proceeded, BC-amended soils shared a generally similar 'firstly increase and then decrease' trend of MCLR sorption and 'firstly decrease and then increase' trend of desorption at most cases. It appeared that MCLR sorption by BC-amended soils was most positively correlated with mesoporosity and surface basic functionality. BC-amendment increased MCLR-trapping for most soils, especially 4% BC at 3 month-aging maximized trapping ratio of GZ, SY and SX to 86.59%–95.43%, 80.01%–87.20% and 78.73%–90.85%, respectively, at 50–500 μg/L MCLR by largely increasing sorption and decreasing desorption. BC-amendment best matched GZ soil because MCLR-trapping of BC-amended GZ exceeded other amended soils at the same BC dose and aging time, but failed to obviously increase MCLR-trapping of HS soil at most cases, except only case with 2% BC at 3 month-aging. Site energy distribution verified that maximally enhanced MCLR-trapping of most soils was due to greatly enhanced sorption affinity during sorption and 1st desorption cycle, making closer MCLR-binding that more resistant to desorption. Contrarily, BC-amendment did not enhance sorption affinity of HS along sorption-SDE to compromise MCLR-trapping increase at most cases. This study validated 3 months as suitable BC-aging time to maximize MCLR-trapping in diverse soils, and elucidated influencing factors and mechanisms from view of site energy distribution, which shed novel insights on MCLR sorption-desorption by BC-amended soils, and guided to optimize BC-amendment strategy for efficient MCLR-immobilization and eco-risk elimination in diverse soils. Graphical abstract: Image 1 Highlights: The properties of diverse soils changed with rising biochar (BC) dose and aging time. Mesoporosity, surface basic group and pHPZC facilitated microcystin-LR (MCLR) sorption. BC raised MCLR-trapping ratio of most soils, especially at 4% dose with 3-month aging. BC did not raise MCLR-trapping of HS in most cases except at 2% dose with 3-month aging. Sorption affinity was increasingly stronger as sorption and sequential desorption proceeded. Abstract : BC-amendment effects on MCLR sorption and desorption by diverse soils varied with BC dose and aging time.