College of Resources and Environmental Sciences, China Agricultural University, Key Laboratory of Plant-Soil Interactions, Ministry of Education, Key Laboratory of Arable Land Conservation (North China), Ministry of Agriculture, Beijing 100193, China.
College of Resources and Environmental Sciences, China Agricultural University, Key Laboratory of Plant-Soil Interactions, Ministry of Education, Key Laboratory of Arable Land Conservation (North China), Ministry of Agriculture, Beijing 100193, China.
Sci Total Environ. 2019 Mar 25;658:1306-1315. doi: 10.1016/j.scitotenv.2018.12.269. Epub 2018 Dec 19.
An understanding of biochar colloid aggregation and stability in aqueous environments is critical for assessing biochar fate and mobility in the soil. The aggregation kinetics of wheat straw-derived biochar colloids pyrolyzed at two temperatures 300 and 600 °C (WB300 and WB600 colloids, respectively) were investigated in monovalent and divalent electrolyte solutions in absence/presence of humic acid (HA). Results show that the critical coagulation concentrations (CCCs) of WB300 colloids in NaCl and CaCl solutions were 274 and 61.4 mM, which were higher than those (183 mM for NaCl and 38.1 mM for CaCl) of WB600 colloids. WB300 had more oxygen-containing functional groups than WB600, which induced more negative surface charge on WB300. HA of 5 mg L greatly increased the CCCs of WB300 and WB600 colloids to 1288 and 806 mM in NaCl solutions, but decreased the CCCs to 54.6 and 37.0 mM in CaCl solutions because of strong bridging between HA and Ca. In CaCl solutions with high salt concentrations (near to the CCCs), different HA concentrations caused distinct effects on the aggregation of biochar colloids. The aggregation of biochar colloids was accelerated by HA with the concentration higher than 5 mg L through cation-bridging while the aggregation was inhibited in the presence of <2.5 mg L HA. Our findings show that pyrolysis temperature used for biochar production had a large effect on the aggregation of biochar colloids in the aqueous environment and that cation type and dissolved natural organic matter are controlling variables.
了解生物炭胶体在水相环境中的聚集和稳定性对于评估生物炭在土壤中的归宿和迁移性至关重要。本文研究了在单盐和二价盐电解质溶液中（存在/不存在腐殖酸（HA）的情况下），两种温度（300°C 和 600°C）热解的小麦秸秆衍生生物炭胶体（WB300 和 WB600 胶体）的聚集动力学。结果表明，在 NaCl 和 CaCl 溶液中，WB300 胶体的临界聚沉浓度（CCC）分别为 274 和 61.4mM，高于 WB600 胶体的 183mM（NaCl）和 38.1mM（CaCl）。WB300 比 WB600 含有更多的含氧官能团，这导致 WB300 表面带更多的负电荷。浓度为 5mg/L 的 HA 大大增加了 NaCl 溶液中 WB300 和 WB600 胶体的 CCC 至 1288 和 806mM，但在 CaCl 溶液中降低至 54.6 和 37.0mM，这是由于 HA 与 Ca 之间的强烈桥接作用。在高盐浓度（接近 CCC）的 CaCl 溶液中，不同的 HA 浓度对生物炭胶体的聚集产生了不同的影响。当 HA 浓度高于 5mg/L 时，通过阳离子桥接作用加速了生物炭胶体的聚集，而当 HA 浓度低于 2.5mg/L 时，聚集则受到抑制。研究结果表明，生物炭生产中使用的热解温度对水相环境中生物炭胶体的聚集有很大影响，阳离子类型和溶解的天然有机物是控制变量。
