不同植物配植人工湿地对废水中镉的去除和富集效应

重金属对水体的污染程度日益加重。人工湿地是一种人工建造的安全高效的生态处理技术，植物和基质都是其重要组成部分，其中的植物可以吸收污水中的营养物质、重金属及其他有毒、有害物质。为了研究植物对含Cd废水的处理效果，检验植物丰富度对人工湿地Cd去除能力的影响，探讨湿地植物对Cd的富集特性，本研究选用3种湿地植物灯心草（Juncaceae）、水葫芦（Eichhornia crassipes）和水芹菜（Oenanthe javanica），按2种或3种混合方式，构建小型模拟人工湿地，测定分析其对低浓度（5 mg/L）含Cd废水中Cd的去除率、溶解氧（DO）浓度的影响及3种植物富集Cd含量、Cd在植物体内的亚细胞分布和化学形态。结果表明：水芹菜、灯芯草、水葫芦共同配植的湿地系统中，植物间发生协同作用，废水中DO浓度、Cd的去除率及3种植物对Cd的总富集量均最高；水芹菜的地下部分（根）富集量显著高于另外2种植物，灯芯草对Cd的抗性最强且转运系数最高，这2种植物属于优势湿地植物；Cd主要富集在3种植物细胞壁部分，以减轻对其它细胞器的毒害作用；植物体内的Cd以游离态为主，与有机配体结合较少，以减轻植物受害程度。在低浓度Cd污染下，水芹菜+灯芯草+水葫芦的组合对废水的净化效果最好，Cd去除率达到68.14%。

Removal and Enrichment of Cadmium in Wastewater by Different Plant Combinations in Constructed Wetlands

Heavy metal pollution of water bodies is becoming more serious and constructed wetlands are a safe and efficient ecological treatment technology. The plants and their arrangement on the substrate are crucial components of the wetland systems that absorb nutrients, heavy metals and other harmful substances in wastewater. In this study, Juncaceae (rush), Eichhornia crassipes (water hyacinth) and Oenanthe javanica (water celery) were planted in four combinations to simulate small constructed wetlands. The effectiveness of different arrangements were tested for Cd removal and plant enrichment characteristics to provide theoretical support for artificial wetland construction. The four plant combinations were set as follows: (A) O. javanica + E. crassipes; (B) O. javanica + Juncaceae; (C) E. crassipes + Juncaceae; (D) O. javanica + E. crassipes + Juncaceae. Each treatment was run in triplicate in water with an initial Cd concentration 5 mg/ L. On days 1, 3, 5 and 7 of the test, the Cd content, Cd removal rate, dissolved oxygen (DO) concentration, subcellular distribution and chemical morphology of plants in each treatment were measured and analyzed. Results show that there were synergistic effects among plants when water celery, rush and water hyacinth were planted together (treatment D). The removal rate, total Cd enrichment of the three plants and DO were also the highest in this treatment, significantly higher than with the other three treatments (p<0.05). Cd enrichment in the roots of water celery was significantly higher than in the other two plants, and the resistance and transport coefficient of rush to Cd were highest. Thus, the combination of water celery and rush dominated removal activity. Cd was mainly concentrated in the cell walls of the three plants, protecting other organelles from Cd toxicity. Cd existed primarily in the free state in all three plants, rather than bound by organic ligands, also reducing Cd damage to plant organelles. The combination of water celery, rush and water hyacinth removed Cd most effectively with removal rates up to 68.14%.