太湖北部沉积物中铁硫的地球化学特征研究

Geochemical characteristics of iron and sulfur in sediments of northern Lake Taihu

选择太湖北部柱状沉积物为研究对象,对沉积物及间隙水中铁硫的地球化学特征进行了研究。结果显示,间隙水中Fe2+的平均浓度是S2-平均浓度的82倍,其值为9.6～270.5μmol/L。这说明沉积物中是以Fe3+的还原为主,而非SO24-。沉积物中还原性无机硫以黄铁矿为主,其次为AVS,最后为单质硫。沉积物中的Fe2+的浓度均高于其他形态的铁,约占总铁含量的30%～40%。活性铁的浓度为109.86～208.16μmol/g,仅占总铁的20%左右。沉积物各层中与硫结合的铁仅占总铁的0.12%～2.35%,占活性铁的0.39%～8.36%。通过分析铁硫之间的关系并结合蓝藻爆发的时间推断,铁硫化合物的生成不是PO34-释放的原因。太湖北部沉积物中Fe-S及P-S之间相互关系较弱。

The sediments of northern Taihu Lake were selected to study the geochemical characteristics of iron and sulfur in porewater and sediments. The results showed that the mean concentration of Fe^2＋ was 82 times higher than that of S2 , ranging from 9.6 to 270.5 μmol/L. This indicated that reduction environment in sediment was dominated by Fe^3＋ but not SO4^2- . Elemental sulfur occupied the least percentage of inorganic reduced sulfur in sediments （0.4% -7% ）, then was AVS and pyrite taken up the most proportion of inorganic reduced sulfur （〉 75）. The concentration of Fe2. was higher than those of other iron species, occupying 30% -40% of total iron approximately. The concentration of reactive iron was in the range of 109.9 - 208.2 μmol/g, merely occupying 20% of total iron. The sulfide-bound iron （AVS-Fe plus Pyrite-Fe） of each segments merely occupied 0. 12% 2. 35% of total iron, 0. 39% - 8.36% of the reactive iron. Through an analysis of the relationship between iron and sulfur, and the blooming time of algal, it is inferred that the formation of iron-sulfide minerals is not the reason that causes the release of PO3 . Fe-S and P-S just show weak relationship in sediments of northern Lake Taihu.