Packed column experiments and numerical simulations were conducted to investigate the co-transport behavior of nanoscale iron supported on biochar (nFe/BC) pyrolyzed at 500℃ and 800℃, respectively, with arsenic (As) in contaminated soil. The results showed that the mobility of nFe/BC (nFe/BC500 and nFe/BC800) in As-contaminated soil was obviously lower than that of pristine biochars (BC500 and BC800), decreasing by about 57.8% and 45.5% in As-contaminated soil, respectively. This is likely because zeta potentials of nFe/BC became less negative due to the adherence of positively charged Fe onto the BC. Therefore, electrostatic repulsion between nFe/BC and soil grain was weakened, resulting in a lower mobility of nFe/BC. Also the mobility of nFe/BC was reduced with an increase in pyrolysis temperature. This is likely because that the surface charge of nFe/BC produced at high temperature was less negative, due to the lower density of O-containing functional groups. Therefore, the total repulsive interaction energies between nFe/BC and soil grain were reduced. A two-site kinetic retention model was successfully employed to simulate the transport of nFe/BC in soils, further illustrating the co-transport characteristics of nFe/BC. Additionally, pristine BCs facilitated the transport of As due to the competition between BCs and As for the available sorption sites on the soil surface. However, nFe/BC first inhibited the transport of As, and then promoted it. The main reason could be because the iron substance or Fe3O4 on the surface of nFe/BC reacted with As, and then fixed it in soil. Once the reaction between nFe/BC and As was completed, nFe/BC lost its original inhibitory effect, and instead acted as a carrier to promote As transport in soil. This could cause potential risks of As to the groundwater environment.
| 科 Family | 属数 Number of genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) | 属 Genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) |
|---|---|---|---|---|---|---|
| 鹅膏菌科Amanitaceae | 2 | 11 | 5.26 | 鹅膏菌属 Amanita | 10 | 4.78 |
| 小菇科 Mycenaceae | 2 | 12 | 5.74 | 丝盖伞属 Inocybe | 5 | 2.39 |
| 多孔菌科 Polyporaceae | 8 | 14 | 6.70 | 蜡蘑属 Laccaria | 5 | 2.39 |
| 红菇科 Russulaceae | 3 | 23 | 11.00 | 小皮伞属 Marasmius | 6 | 2.87 |
| 小菇属 Mycena | 11 | 5.26 | ||||
| 光柄菇属 Pluteus | 5 | 2.39 | ||||
| 红菇属 Russula | 17 | 8.13 | ||||
| 栓菌属 Trametes | 5 | 2.39 |