无机水化学离子在实验流域降雨径流过程中的响应及其示踪意义

Responses of hydrochemical inorganic ions in the rainfall-runoff processes of the experimental catchments and its significance for tracing

为研究无机水化学离子在降雨径流示踪中的可能性,在实验流域实测降雨、地面径流、壤中流、地下水径流过程和流域内17个测孔的地下水过程中,施测了Na+,K+,Ca2+,Mg2+,Cl-,SO42-,HCO3-+CO32-,NO3-,F-,NH4-,PO42-,SiO2和pH,EC,18O的同步过程,还施测了少数土壤水水样。结果是:①在Ca2+与Cl-/SO42-和EC与Na+/(Na++Ca2+)的关系中以及除NO3-,NH4-,PO42-外的所有离子,都可识别出上述各种径流组分;②径流离子过程均与降雨离子过程相仿,随径流组分从地面到地下而渐趋坦化;③除个例外,离子浓度过程均以降雨为最小并从地面径流到地下水径流渐次增大;④降雨和地下水离子过程表现为径流离子过程的两端元;⑤在降雨和各径流组分中,18O过程与大部分离子过程有一定的同步性。从以上结果认为,降雨并不是流域径流离子输出的主要来源,然而却是形成它的主要控制因素。此外,有关试验结果还对应用Cl-进行地下水补给的估算方法提出了问题。

Aimed at the rainfall-runoff tracing using inorganic ions, the experimental study is conducted in the Chuzhou Hydrology Laboratory with special designed experimental catchments, lysimeters, etc. The various runoff components including the surface runoff, interflow from the unsaturated zone and the groundwater flow from saturated zone were monitored hydromet- rically. Hydrochemical inorganic ions including Na^＋,K^＋,Ca^2＋,Mg^2＋,Cl^-,SO4^2-,HCO3^-,＋CO3^2-,NO3^-,F^-,NH4^-,PO4^2-,SiO2 were measured within a one month period for all processes of rainfall, various runoff components and groundwater within the catchment from 17 boreholes distributed in the Hydrohill Catchment, few soil water samples were also included. The results show that： （a） all the runoff components are distinctly identifiable from both the relationships of Ca^2＋ versus Cl^-/SO4^2- , EC versus Na^＋/（Na^＋ Ca^2＋ ） and, from most inorganic ions individually; （b） the variation of inorganic ions in surface runoff is the biggest than that in other flow components; （c） most ions has its lowermost concentration in rainfall process but it increases as the generation depths of runoff components increased; （d） quantitatively, ion processes of rainfall and groundwater flow display as two end members of that of other runoff components; and （e） the 180 processes of rainfall and runoff components show some correlation with that of inorganic ions. The results also show that the rainfall input is not always the main source of inorganic ions of various runoff outputs due to the process of infiltration and dissolution resulted from the pre-event processes. The amount and sources of Cl^- of runoff components with various generation mechanisms challenge the current method of groundwater recharge estimation using Cl^-.