海螺沟冰川退缩区中铬的分布、累积与来源

以青藏高原海螺沟冰川退缩区为研究对象,借助其长达160a的植被演替序列,探讨Cr的时空分布和累积循环特征,并解析其潜在来源。结果表明,退缩区C层土壤Cr含量为(155.17±32.68)mg/kg,显著高于O层(48.23±10.21)mg/kg(P<0.05)。随着植被的演替,O层土壤Cr含量随淋溶作用的增强而逐渐降低。在植被系统中,各演替阶段优势种对Cr均无显著富集特征(ω<1)。此外,土壤是冰川退缩区生态系统的主要Cr库(2269.90±234.57)mg/m²,而各样地O层土壤Cr储量约为植被的9~20倍。随着演替的进行,土壤有机质含量升高而植被的“归还作用”减弱,导致Oi、Oe层土壤Cr储量逐渐减小而Oa层和植物Cr储量逐渐增大。研究发现,“高循环强度-低吸收利用”为冰川退缩区生态系统中Cr的主要循环策略。根据主成分解析结果,贡嘎山土壤Cr以母质土壤风化来源为主(68.89%),而大气沉降对其影响并不显著。

Distribution,accumulation and sources of chromium in Hailuogou glacier retreated area

Given the complete succession sequence of glacier retreated area providing a novel platform to trace heavy metal cycles in the terrestrial ecosystems, we explored the distribution pattern, transportation and allocation among soil and vegetation components, and potential sources of chromium (Cr) at the Hailuogou, eastern of Tibetan Plateau. Cr concentration in C-horizon was (155.17±32.68) mg/kg, which was significantly higher than that in O-horizon (48.23±10.21) mg/kg (P<0.05). With the increase of retreated time, the concentration of Cr in O-horizon gradually decreased due to the increase of soil leaching induced the Cr lost. The dominant vegetation species in each succession stage had no obvious enrichment effect on Cr (ω<1). Moreover, the soil was the main Cr pool in the ecosystem of glacier retreated area (2269.90±234.57) mg/m², whose Cr storage in the O-horizon of each stage up to 9~20times greater than that in vegetation. In the late period of succession, Cr storage in Oi-horizon and Oe-horizon gradually decreased but Cr storage of Oa-horizon and vegetation increased, because of the weak “return effect” of Cr, and increment of soil organic matter induced the enhanced Cr accumulation in organic soils. Moreover, we highlighted that the high cycling rate and low absorption-utilization efficiency was the main cycling strategy of Cr in Hailuogou glacier retreated area. The principal component analysis (PCA) results finally showed that Cr in soil of Gongga Mountain was mainly derived from weathering process of soil parent material (68.89%), but with the limited influence of atmospheric deposition.