摘要
底层水体氧动态直接制约着许多与底栖生物的生物、生态行为息息相关的生物地球化学过程.高分辨率(垂向分辨率为3 mm)的原位采样技术能精确地获取ρ(p043--P)和ρ(NH4+-N)在沉积物-水界面微环境的分布特征,这对准确掌握营养盐在该区域发生的独特的生物地球化学过程至关重要.研究表明,连续曝氮气或空气下,孔隙水中ρ(NH4+-N)显著提高,升温使该效应进一步增强.在常温下,曝空气沉积物孔隙水中ρ(PO43--p)显著下降,曝氮气则无显著影响;但厌氧条件下升温至35℃时ρ(PO43--P)显著增加.在低氧和厌氧时,PO43--P从沉积物向水体的扩散速率(以P计)为10.41～25.85 mg/(m2·d);但底层DO充足或CaO2添加剂量为5 g/m2致ρ(DO)呈过饱和状态时,PO43--P释放速率从0.07 mg/(m2 ·d)进一步降至-17.20 mg/(m2 ·d),说明随着ρ(DO)的升高,PO43--p有进一步削减的潜力.PO43--p在界面处的释放强度显著依赖于氧气和温度的动态.总体来看,DO充足时,NH4+-N和PO43--P的地球化学循环过程表现为从上覆水向沉积物吸附固定;当升温或缺氧时,这一过程可能被抑制甚至发生逆转.
Abstract
Benthic O2 availability in aquatic systems plays an important role in biogeochemical processes crucial to the biology and ecology of benthic communities.In situ methods enable high-resolution measurements of solutes close to the bottom water, and their application to surface sediments has the potential to better define the links between oxygen and the unique biogeochcmical phenomena occurring in these regions.The potential reaction of solute dynamics in the sediment was investigated by recording high resolution microprofiles of PO43--P and NH4 +-N using an in situ sampler micro-peeper.The results suggested that continuous air/nitrogen microbubbles could significantly enhance NH4 +-N levels in the porewaters, and could be further enhanced with increasing temperature.Moreover, porewater PO43--P levels were significantly lower under continuously bubbling air, but were not affected by continuously bubbling nitrogen.An obvious tendency for increasing PO43--P levels was observed with the increasing temperature, similar to the NH4 +-N distribution.Typical input to the overlying water under low oxygen or nitrogen conditions was found to be 10.41-25.85 mg/(m2 · d) , whereas fluxes under aerobic conditions and CaO2 addition (5 g/m2) wcre only-17.20-0.07 mg/(m2· d).PO43--P release was found to be dependent on oxygen level and temperature.Under aerobic conditions, surface sediment might be considered an important sink of NH4 +-N and P043--P pollutants because of adsorption from overlying water.However, sediments could also inversely act as a source of pollutants by releasing dissolved nitrogen and phosphorus nutrients to bottom water in the case of hypoxia or higher temperature environment.
基金项目
国家自然科学基金(41203064)
江苏省自然科学基金(BK20131465)
中国科学院重点部署项目(KZZD-EW-10-05)
NETL
NSTL
维普
万方数据