西南喀斯特流域风化作用季节性变化研究

Weathering Seasonal Variations in Karst Valley in Southwest China

以西南地区典型喀斯特流域,长江上游一级支流嘉陵江温塘峡段为例,连续2 a按月取样,并通过水化学分析、同位素分析等方法,研究得出嘉陵江温塘峡段水化学类型受地层控制,为HCO3--Ca型.在稀释作用的影响下,除HNO3-的浓度因受人类活动的影响雨季偏大外,其余大部分离子浓度雨季较旱季偏小.所有样品的(Ca2++Mg2+)/HCO3-(浓度比)在0.5～1之间,(Ca2++Mg2+)/(HCO3-+SO24-)(浓度比)大部分处于0.5～1之间,由此表明嘉陵江风化作用主要以碳酸的风化和硫酸风化碳酸岩盐为主,硫酸岩盐的风化为辅.根据同位素分析结果表明嘉陵江水中δ13CHCO-3值为-8.74‰～-7.36‰,δ34SSO2-4值旱季为14.43‰,雨季为12.21‰,表明硫酸对碳酸盐岩的风化作用和硫酸盐岩自身的风化作用在雨季均表现更强,其中,硫酸岩盐自身的风化作用在雨季强度更大,而旱季碳酸对碳酸盐岩的风化作用比较强.

Jialing River is a 1st grade tributary of upstream Yangzi River.In two years,Samples were collected monthly in Wentang Gorge section of Jialing River and analyzed multi-parameters including hydrochemistry and isotopes.Thus,a general result was concluded that the hydrochemical characteristic of Jialing River in Wentang gorge is controlled by weathering of stratum and the hydrochemical type is HCO-3-Ca.Most irons were influenced by dilution,which had higher concentrations in dry season than that in rainy season,but nitrate.Nitrate,which was controlled by human activities,has higher concentrations in rainy season.However,some other analyst revealed weathering impacts.The contrast ratio of（Ca2＋＋Mg2＋） and HCO-3 were between 0.5-1,the same as（Ca2＋＋Mg2＋） and（HCO-3＋SO2-4）,Which implied that the weathering impacts in this basin was mainly carbonated and sulfate weathering of carbonated,and sulphate rocks weathering was not so significant.The values of δ13 CHCO-3 in Jialing River were-8.74‰——7.36‰,and δ34 SSO2-4 was 14.43‰ in dry season and 12.21‰ in rainy season.The data of isotopes inferred that,in rainy season sulfate weathering of carbonated and sulphate rocks weathering both had more impacts and sulphate rocks weathering played a more important role than sulfate weathering of carbonated,but,in dry season,carbonated weathering of carbonated was more meaningful.