三江平原多级沟渠系统沉积物中铁的分布特征

Distribution of Sediment Iron of the Ditch System in Sanjiang Plain,Northeast China

以三江平原典型多级沟渠系统（毛渠-农渠-斗渠-支渠-干渠）为对象,研究了其0～60 cm沉积物全铁含量的空间分布特征.结果表明,多级沟渠系统中沉积物的平均铁含量为（3.02±0.10）×104mg.kg-1,各类型、各等级的沉积物铁含量具有极显著差异（F=6.261,p 0.001）,最高值出现在农田斗渠（3.71×104mg.kg-1）中,而最低值出现在湿地斗渠（2.43×10^4mg.kg-1）中.整个多级沟渠系统沉积物各层的铁含量没有显著性差异（F=0.093,p=0.693）,但与沟渠相邻湿地同深度土层的铁含量相比,沟渠沉积物0～10 cm层、10～20 cm层分别增加了51.96%、62.22%.铁虽然具有一定的可迁移性,其最大累积处仅能延伸到第三等级的斗渠中,而非逐级递增.由于湿地保护和气候干热化,现阶段本区含铁径流量有逐渐减少的趋势.沉积物各层铁含量沿沟渠类型和等级的递变揭示了铁输移的历史变迁.

The iron distribution of the multi-level ditch system （hair canal-field canal-lateral canal-branch canal-main canal） was studied through total iron determination of the sediments （0-60 cm）. The results showed that the mean concentration was （3.02 ± 0.10） ×10^4mg.kg-1）. Extremely significant difference was obseved between different ditch level （F = 6. 261, p≤0.001 ）, and the highest and the lowest concentration were present in the farmland lateral canal （3.71×10^4mg.kg-1）） and wetland canal （2.43 ×10^4mg.kg-1））, respectively. The difference of different sediment layers was not significant （ F = 0.093, p = 0. 693 ）, while the iron concentrations of 0-10 cm and 10-20 cm sediments were 51.96% and 62.22% higher than that of the natural wetland soil nearby, respectively. Iron can transfer with the runoff in a certain extent, but it was not cumulated along the ditch system with the largest cumulation location at the third level. The runoff containing iron decreased gradully because of the wetland protection and climate change nowadays. The horizontal transfer of iron along the ditch system indicated the timing and intensity of iron loss in the past since the canals were dredged.