太湖水土界面氮磷交换通量的时空差异

利用原柱样静态释放实验及间隙水分子扩散模型对太湖典型草型湖区(东太湖)及藻型湖区(梅梁湾)的氮磷释放通量进行了逐月研究.原柱样氮磷静态界面交换通量(F_i)在同一湖泊不同生态类型湖区有差异性,东太湖氨态氮和可溶性磷酸盐的年平均交换通量分别为(44.9±21.9)mg·(m²·d)^-1(平均值±标准偏差)和(2.06±1.71)mg·(m²·d)^-1,梅梁湾为(16.2±12.0)mg·(m^-1·d)^-1和(0.53±0.52)mg·(m²·d)^-1.2湖区的分子扩散通量(F_m)同样表现为这样的差异,但是其绝对值与静态释放通量相比有数量级的差异,该模型不能用于太湖这样风浪显著且底栖生物活性较高的湖泊水土界面氮磷营养盐交换通量的估算.仅从不同生态类型的湖区比较结果看,草型湖区比藻型湖区有更高的氮磷交换通量.F_i/F_m比值作为1种反映底栖生物活性的指标反映出东太湖有更高的底栖活性.在水体溶解氧水平通常保持在较高的水平,即好氧状态下,氮磷界面交换通量与溶解氧水平(DO)无显著相关.同样,在现有浓度水平下,其水土界面交换通量与水体氮磷浓度无显著相关.东太湖较高的释放通量与相对较低的水体营养盐负荷的差异来自于大型水生植被的消浪促沉降及其本身的吸附吸收作用,这是恢复水生植被以重建健康水生生态系统的重要理论依据.

Space-Time Dependent Variances of Ammonia and Phosphorus Flux on Sediment-Water Interface in Lake Taihu

Monthly research of ammonia and phosphorus fluxes in water-sediment interface in East Lake Taihu(ELT,macrophyte dominated) and Meiliang Bay(MB,algae dominated) was processed with intact sediment cores' incubation and pore water diffusive model.The ammonia and phosphorus fluxes calculated with intact sediment cores' incubation(F_i) showed discrepancy in different lake zones with different ecotype.The yearly average fluxes of ammonia and dissolved phosphorus in ELT were(44.9±21.9) mg·(m²·d)^-1(Mean±SD) and (2.06±1.71) mg·(m²·d)^-1;and(16.2±12.0) mg·(m²·d)^-1 and(0.53±0.52) mg·(m²·d)^-1 in MB.The molecular diffusive fluxes(F_m) of the two lake zones showed the same pattern,but the absolute value difference may as high as an order of magnitudes.So this molecular diffusive model cannot be used to evaluate the nutrients fluxes in sediment-water interface in Lake Taihu,a lake vulnerable with wind and wave affection and benthic bio-disturbation.Compared with the two lake zones with different ecotypes,macrophyte dominated one had higher nutrients fluxes than the algae one.ELT had higher bio-disturbation,which was revealed by the F_i/F_m ratio.When the dissolved oxygen(DO) remained in high concentration,known as aerobic condition,the nutrients' fluxes were not correlated with the DO.Similarly, the fluxes were not correlated with the nutrients' concentration of the overlying water at the existing condition.The discrepancy between higher nutrients' fluxes and lower nutrients loading in ELT suggested the higher particulate settlement rate and assimilate rate promoted by the macrophyte.This is the important theoretical basis of rebuilding the healthy ecosystems with restoring the water plants.