沉水植物对沉积物-水界面环境特征的影响

为明确沉水植物对沉积物-水界面环境特征的影响机制,在采自于太湖草、藻型湖区的沉积物柱状样中种植沉水植物后进行破坏性采样,测定沉积物-水界面以上5 cm上覆水的营养盐含量和沉积物的含水量、中值粒径、w(TOC)、w(TON)、w(TP)、金属元素含量等的垂直分布和氧气侵蚀深度. 结果表明,种植沉水植物对沉积物-水界面环境特征的影响主要为:①显著降低了上覆水中ρ(PO₄3--P)〔草型湖区上覆水由(7.98±1.85)μg/L降至(4.65±1.16)μg/L,藻型湖区上覆水由(7.86±0.84)μg/L降至(4.89±0.48)μg/L〕和草型湖区上覆水中的ρ(DOC)〔由(6.64±0.41)mg/L降至(4.73±0.69)mg/L〕,但没有引起上覆水中ρ(NO₃--N)、ρ(NO₂--N)和ρ(NH₄+-N)的显著差异；②明显提高表层沉积物的含水量,减小草型湖区沉积物表层的中值粒径；③降低草型湖区沉积物表层2 cm内w(TOC)和w(TON),增加草型湖区上层沉积物中w(TP)；④明显降低草型湖区沉积物中w(Ca)和w(Mg),但对草、藻型湖区沉积物中的Al,K,Cu,Pb和Zn的含量影响都不明显；⑤藻型湖区沉积物中氧气侵蚀深度由1.6 mm增至3.0 mm,草型湖区沉积物则由3.7 mm增至24.0 mm. 

Effects of Macrophytes on the Environmental Characteristics of Sediment-Water Interface

To understand the influence of macrophytes on the properties of the sediment-water interface in shallow lakes, sediment cores were sampled in both a macrophyte-dominant region and a phytoplankton-dominant region. The vertical profiles of nutrient content, water content, particle size distribution, organic carbon, organic nitrogen, total phosphorus, heavy metals, and dissolved oxygen content in the sediment cores and overlying water were determined. The results are as follows:1) the growth of submerged macrophytes did not change the contents of nitrate, nitrite and ammonium in the overlying water. However, it significantly decreased the contents of phosphate (from(7.98±1.85)μg/L to(4.65±1.16)μg/L in the phytoplankton-dominant region and from(7.86±0.84)μg/L to(4.89±0.48)μg/L in the macrophyte-dominant region) and dissolved organic carbon (from(6.64±0.41)mg/L to(4.73±0.69)mg/L in the macrophyte-dominant region). 2) The growth of macrophytes also significantly decreased the medium diameter of the sediment, the organic carbon and nitrogen contents in the sediment 0-2 cm from the surface. 3) The presence of macrophytes also significantly decreased the contents of calcium and magnesium in the whole sediment cores, while it increased the contents of phosphorus and the oxygen penetration depth (from 1.6 mm to 3.0 mm in the phytoplankton-dominant region and from 3.7 mm to 24.0 mm in the macrophyte-dominant region) in the sediment. 4) There were no significant differences in the contents of aluminum, potassium, copper, lead or zinc in the sediment between the macrophyte-dominant region and the phytoplankton-dominant region.