黄河口无机碳输运过程对pH异常增高现象的响应

为研究黄河无机碳的输运过程及有效入海通量,通过对2004年至2006年黄河口汛期和非汛期淡水-海水混合过程中无机碳参数、溶解氧饱和度、叶绿素和NH⁺₄、 PO^3-₄的分析得出,黄河口低盐度区pH出现相对于淡水端异常增高现象,而恰在此区域DIC出现亏损现象,黄河口淡-咸水混合区域pH异常增高现象可以表征无机碳的沉降作用.淡咸水混合初期生物好氧呼吸作用的降低能够导致p_CO2的迅速降低是造成低盐度区pH出现相对于淡水端异常增高现象的主要原因.根据河口溶解物质的保守混合模型,发现混合过程中ΔDIC与ΔTA是1∶1的关系,表明DIC出现亏损是由于HCO^-₃清除造成的,汛期和非汛期黄河口无机碳的沉降作用能够清除输入到河口DIC总量的10%,即黄河口每年可清除1.21×10⁵ t河流输入的溶解无机碳,DIC的有效入海通量约为10.86×10⁵ t,通过评估,黄河流域风化作用吸收的大气CO₂量将有10%左右被河口无机碳沉降作用重新释放到大气中,而流域风化作用固定的CO₂在河口将有2.24×10⁵ t（以CO₂计）重新释放到大气中.

Phenomena of pH Instant Increasing and Its Effect on Dissolved Inorganic Carbon Flux to Sea in Yellow River Estuary

Dissolved inorganic carbon (DIC), pH, the partial pressure of CO (pCO2), total alkalinity (TA), dissolved oxygen saturation (DO), chlorophyll a (Chl-a), and NH4+, PO4(3-) were studied in mixing zone of Yellow River estuary from September 2004 to April 2006. The results indicate that pH value is higher than that of freshwater in low salinity area where DIC is non-conservative. NH4+, PO4(3-) sharply decreasing indicates that biogenic respiration is possibly inhibited in early mixing of freshwater and seawater, then pCO2, which is derived from biogenic respiration, swiftly decrease and lead to CaCO3 precipitation in low salinity area, and the pH value will simultaneously increase in this area. Instant increasing pH value can be used as index of CaCO3 precipitation in Yellow River estuary. According to dissolved matter mixing model in estuary, the observation of 1:1 removal of TA and DIC provides just evidence that DIC removal we observed in the field is a result of CaCO3 precipitation. The process can clean 10% (1.21 x 10(5) tons) DIC which is transported by freshwater both in dry and wet weathers, and the annually effective DIC flux to sea of Yellow River is 10.86 x 10(5) tons. Ten percent of CO2 (2.24 x 10(5) t) which is absorbed by chemical weathering process in drainage basin will release to atmosphere in Yellow River estuary.