河流植物群落下底泥中碳氮磷和重金属富集效应分析

【目的】探明河流植物群落下的底泥中碳氮磷和重金属的积累机制。【方法】在淮河上游地区索河流域不同生境类型(浅滩区和浅水区)下分别选取3处当地优势植物扁秆藨草(Scirpus planiculmis)和黑三棱(Sparganium stoloniferum)单优势群落,采集植物群落下和对照(植物盖度<5%)0～10 cm(表层)、≥10～20 cm(中层)和≥20～30 cm(下层)处的底泥,用独立样本t检验分析植物群落下3个层次的底泥中OC(有机碳)、TN(全氮)、TP(全磷)、As、Cd、Co、Cr、Cu、Hg、Ni、Pb和Zn是否有显著富集效应,计算底泥中各元素的相对富集指数E(relative enrichment index, E),并用偏最小二乘回归(PLSR)法分析相对富集指数的影响因素。【结果】扁秆藨草和黑三棱群落下的底泥中OC、TN、As、Cd、Cr、Hg、Ni、Pb和Zn有显著富集作用,且富集作用主要发生在表层底泥。整体上,植物群落下0～30 cm深的底泥中OC、TN和各重金属的E值主要受到各元素在底泥中本底值的影响,其次为植物种类,再次为生境类型,而底泥质地对其影响相对较小。【结论】在污染河流中种植当地优势挺水植物种可以使河流中的营养元素和重金属定向转移到植物群落下的底泥中,尤其是表层底泥中。这其中的主要驱动力表现为植物对水体中颗粒物和营养物质的拦截,以及植物枯落物和死亡根系的分解及矿化。扁秆藨草可能对Cd、Cr、Hg、Pb和Zn有吸收富集作用。

Accumulation of carbon,nitrogen, phosphorus and heavy metals in sediment under plant communities in river

【Objective】Investigate the mechanism of organic carbon(OC), total nitrogen(TN), total phosphorus(TP)and heavy metal(As, Cd, Co, Cr, Cu, Hg, Ni, Pb, and Zn)accumulation in sediment of plant communities in river. 【Method】We selected three sites dominated by Scirpus planiculmis and Sparganium stoloniferum each in shoal and shallow water habitats of the Suo River, a tributary of the Huai River. We collected sediment from the surface layer(0-10 cm), middle layer(≥10-20 cm)and sublayer(≥20-30 cm)of the plant communities and CK(blank control). We analyzed the accumulation of OC, TN, TP and heavy metals in the sediment of three layers using t-tests for independent samples; calculated relative enrichment index (E)of OC, TN, TP and heavy metals in the sediment of three layers; and then used partial least squares regression to analyze the influence of various factors on each element’s E.【Result】OC, TN, As, Cd, Cr, Hg, Ni, Pb and Zn were significantly enriched in sediment of the S. planiculmis and S. stoloniferum communities. The enrichment effect mainly occurred in the surface sediment. Overall, the main factors influencing the elements’ E values were the elements’ background values in the sediment, followed by plant species, habitat type, and sediment texture. 【Conclusion】The results of the present study provide a reference for the ecological restoration of polluted rivers. Planting local dominant species in polluted rivers helps transfer carbon, nutrient elements and some heavy metals from the river ecosystem into the sediment of the plant communities, especially into the surface sediment. The main driving forces may be plants’ interception of particulate matter and nutrients in the water, as well as the decomposition and mineralization of plant litter and dead roots. It is also possible that S. planiculmis can absorb Cd, Cr, Hg, Pb and Zn and that S. stoloniferum can absorb As, Cd, Cr, Hg, Ni, Pb and Zn, although this requires validation.