A comprehensive study on a 350-cm long sediment core revealed rich geochemical information in an interesting location of Xiangxi He (river) in TGR. The vertical profiles of trace metals (TMs) and nutrients displayed an irregular pattern, fluctuating around their background values, and no gradual increase was detectable. For TMs, average concentrations were Cd: 0.35 ± 0.21, Co: 21.91 ± 3.30, Cr: 27.06 ± 5.03, Cu: 27.09 ± 4.96, Ni: 34.08 ± 5.23, Pb: 20.58 ± 5.84 and Zn: 80.18 ± 69.16, all in μg/g (n = 61). For most of TMs, their bioavailable forms were only a minor fraction. Therefore, the conventional total metal concentrations will inevitably overestimate their potential risk to ecosystem. For nutrients, average concentrations were total phosphorus (TP): 0.81 ± 0.14, total nitrogen (TN): 1.46 ± 0.28, total sulfur (TS): 0.54 ± 0.19, total carbon (TC): 32.02 ± 8.35, total organic carbon (TOC): 20.90 ± 7.5, all in g·kg⁻¹ (n = 61), and appeared somewhat higher than the “lowest effect level”, which seems to explain the repeated observations of algal blooms in this relatively stagnant section of the river in TGR. The mineralogical composition identified by XRD agreed well with that obtained by chemical analyses. The study revealed that the Xiangxi sediment core (XX06) was remarkably heterogeneous in mineralogical composition, probably caused by natural processes and the dam management. The increased sedimentation rate within TGR should induce a mass dilution effect, thus decreasing the concentrations of pollutants. Large sampling scale and a universally accepted and uniformed analytical sampling and method, together with more vigorous analytical quality control, must be practiced and a solid database be built to facilitate the ecosystem assessment of TGR area.

对 350 厘米长沉积岩心的综合研究揭示了 TGR 中湘西河（河）一个有趣位置的丰富地球化学信息。痕量金属 (TM) 和营养素的垂直分布显示出不规则的模式，围绕它们的背景值波动，并且没有检测到逐渐增加。对于 TM，平均浓度为 Cd: 0.35 ± 0.21, Co: 21.91 ± 3.30, Cr: 27.06 ± 5.03, Cu: 27.09 ± 4.96, Ni: 34.08 ± 5.23, Pb: 20.58 ±8.0 ±8 in 18.微克/克 ( n = 61）。对于大多数 TM，它们的生物可利用形式只是一小部分。因此，常规的总金属浓度不可避免地高估了它们对生态系统的潜在风险。对于养分，平均浓度为总磷（TP）：0.81±0.14，总氮（TN）：1.46±0.28，总硫（TS）：0.54±0.19，总碳（TC）：32.02±8.35，总有机碳（ TOC): 20.90 ± 7.5, 所有单位为 g·kg ^-1 ( n = 61），并且似乎比“最低影响水平”略高，这似乎可以解释在 TGR 中这条相对停滞的河流部分反复观察到藻华的原因。XRD 鉴定的矿物组成与化学分析得到的矿物组成非常吻合。研究表明，湘西沉积岩心（XX06）的矿物组成非常不均匀，可能是由自然过程和大坝管理造成的。TGR 内增加的沉降速率应引起质量稀释效应，从而降低污染物的浓度。必须实行大采样规模、普遍接受、统一的分析采样和方法，并加强分析质量控制，建立坚实的数据库，以促进TGR区的生态系统评估。