非溶解性有机质对沿岸带土壤铜吸附及老化的影响

河流沿岸带土壤是阻滞径流污染进入河流水体的最后屏障。为了探索川渝地区常见残渣中非溶解性有机质(NDOM)对流域土壤铜吸附及老化的影响,以嘉陵江(川渝段)内广元、南部、南充和合川沿岸土壤为研究对象,分别将空心莲子草、柠檬果渣和污泥NDOM以10%的比例添加到各沿岸土壤中,研究不同环境条件下NDOM改良土壤对铜的等温吸附,并分析铜在不同NDOM改良土壤中老化特征。结果显示:相比于柠檬果渣和空心莲子草,污泥NDOM改良土壤对Cu~(2+)吸附效果更好。不同NDOM改良土壤对Cu~(2+)的吸附能力与土壤阳离子交换量和比表面积成正比。Langmuir模型比Freundlich模型更适宜描述NDOM改良土壤对Cu~(2+)的吸附过程。温度的升高可以促进Cu~(2+)的吸附,且Cu~(2+)吸附过程是一个自发、吸热和熵增的过程。各NDOM改良土壤对Cu~(2+)的吸附量随离子强度的增大先升高后降低(0.1 mol·L~(-1)时最大),而随pH值的升高持续增加。随着老化时间的增加,各NDOM改良沿岸土中的离子交换态和碳酸盐结合态铜含量降低,而铁锰氧化物结合态和有机结合态铜含量升高。相比原始土壤,各NDOM改良土壤中的Cu~(2+)迁移能力整体降低。残渣中NDOM可以增强河流沿岸土壤对Cu~(2+)吸附能力,土壤温度和pH越高,Cu~(2+)老化时间越长,改良土壤对Cu~(2+)的吸附阻滞效果越好。

Influence of non-dissolved organic matter on the adsorption and aging of copper in riverbank soil

Riverbank soil is the last barrier blocking runoff pollution into the river water body. To explore the effect of non-dissolved organic matter(NDOM) on copper adsorption and aging in watershed soils, soils along Guangyuan, Nanbu, Nanchong, and Hechuan from the Jialing River(Sichuan-Chongqing section) were chosen as the research object. Alternanthera philoxeroides, lemon pomace, and sludge NDOM were added to the riverbank soils in a 10% ratio to study the isotherm adsorption of copper(Cu²⁺) by NDOM-amended soil under different environmental conditions. The aging characteristics of Cu²⁺ in the different NDOM-amended soil treatments were analyzed. The results showed that:compared with lemon pomace and A. philoxeroides, the sludge NDOM-amended soil exhibited a better adsorption effect on Cu²⁺. The Cu²⁺ adsorption amount on different NDOM-amended soil samples was proportional to the cation exchange capacity and specific surface area of the soil. The Langmuir model was better suited to describing the Cu²⁺ adsorption process on the NDOM-amended soil than the Freundlich model. An increase in temperature promoted Cu²⁺ adsorption, which is a spontaneous, endothermic, and entropyadding process. The amount of Cu²⁺ adsorbed by each NDOM-amended soil sample first increased and then decreased with an increase in ionic strength(maximum at 0.1 mol·L^-1), and continued to increase with an increase in pH. With the increased aging time, the exchangeable and carbonate form Cu²⁺ content in the NDOM-amended soil decreased, whereas the iron-manganese oxide bound form and organic bound form Cu²⁺ content increased. Overall, Cu²⁺ mobility in each NDOM-amended soil sample was lower than that of the original soil. Sludge NDOM enhanced Cu²⁺ adsorption in the riverbank soil. The higher the soil temperature and pH, the longer the Cu²⁺ aging time, and the better the Cu²⁺ adsorption and blocking effect on the NDOM-amended soil.