基于水化学与稳定同位素的岩溶湿地流域地球化学过程研究

发布时间：2018-04-11 12:02

本文选题：水化学 + 稳定同位素　；参考：《贵州大学》2016年博士论文

【摘要】：湿地作为重要表生环境之一,虽然仅覆盖地球表面的6%,却为地球上20%的已知物种提供了生存环境,具有不可替代的生态功能。与其他陆生生态系统相比湿地以水生植物为优势种,而大部分水生植物具有利用HCO3-进行光合作用的能力,岩溶地区地表水和地下水中主要阴离子为HCO3-,可以为这些水生植被的生长提供充足的碳源。此外,水文条件是湿地形成、发育的决定因素,同时控制着湿地生态系统内生物地球化学过程和功能,因而对湿地水体水化学特征及稳定同位素变化规律的研究,可以揭示湿地水体离子、无机碳和水份等的来源,通过与流入湿地的地表水和地下水水化学和稳定同位素组成之间的差异,可探寻湿地内控制流域水化学组成和稳定同位素变化的地球化学过程。基于此,我们拟以西南岩溶地区贵州威宁草海流域为例,分析不同季节流域内水化学和稳定同位素的变化规律,系统研究草海流域离子来源,并揭示控制该湿地水化学变化的地球化学过程,得到了以下主要认识和结论:(1)草海周边地表水和地下水水化学类型主要为Ca-HCO3,水化学组成主要受碳酸盐岩溶蚀和人类活动共同影响。丰水期草海湿地水水化学类型为Mg-HCO3,Mg-SO4,Ca-SO4和Ca-HCO3型,且水体中主要离子Ca2+和HCO3-由东向西逐渐降低,湿地东侧水体p H呈弱酸性,DO含量低,EC高,且Eh为负值,显示该区域水体呈现还原状态,相反西侧水体p H呈碱性,DO含量高,EC低,Eh为正值,显示该侧区域水体呈氧化状态。枯水期湿地水水化学类型为Ca-HCO3,水质易变参数空间变化差异较小。通过对湿地水化学组成的因素分析发现,引起丰水期湿地水化学的变化可能主要与湿地内生物地球化学过程有关,而枯水期则可能主要受水体蒸发作用影响。(2)丰水期流入草海的地下水和河水中溶解无机碳同位素(δ~(13)C_(DIC))变化范围为-13.66‰~-8.64‰,枯水期δ~(13)C_(DIC)变化范围为-12.61‰~-7.80‰。地下水中DIC主要来自于碳酸盐岩的溶蚀和土壤CO2,同时受丰水期大气降水的稀释作用和枯水期较长的水力停留时间,使地下水中DIC浓度及其同位素产生季节性变化。河水中DIC主要来自地下水,而受河水中浮游植物的光合作用和CO2逸散的影响,河水DIC同位素组成较地下水相比相对偏正。丰水期湿地水δ~(13)C_(DIC)变化范围为-15.13‰~-6.68‰,东侧区域p CO2高于大气p CO2分压与植物根系和沉积物的呼吸作用有关,而西侧区域p CO2则低于大气p CO2分压与沉水植物光合作用有关,同位素组成受化学强化分馏和光合作用影响。枯水期δ~(13)C_(DIC)变化范围为-6.23‰~-0.06‰,几乎整个草海水面p CO2均高于大气p CO2分压,CO2逸散进入大气、CO2还原成甲烷和浮游植物的光合作用使得枯水期DIC同位素偏正。(3)草海流域河水、地下水和湿地水氢氧同位素分析显示,地下水和河水主要受大气降水补给。湿地水在垂向混合同位素组成差异较小,但具有明显的空间和季节变化特征,枯水期(δD=-25.89±6.75‰,δ~(18)O=-2.24±1.12‰)湿地水氢氧同位素组成显著高于丰水期(δD=-66.03±13.77‰,δ~(18)O=-8.31±2.23‰),且丰水期东侧氢氧同位素组成低于西侧,枯水期南侧同位素比值则相对较高,这种分布特征与水生植被分布,大气湿度和水热容量有关。根据同位素质量平衡法计算结果,丰水期草海主要接受地下水补给,而枯水期地下水补给量相对较少,主要来自大气降水。(4)丰水期和枯水期草海周边地下水中硫同位素平均值分别为-14.40‰和-15.00‰,河水中硫同位素平均值为-13.91‰和-13.44‰,而湿地水中硫同位素平均值分别为-6.68‰和1.18‰。研究发现湿地水丰水期中硫酸盐主要来自地下水和大气降水,而枯水期湿地水中硫酸盐则主要来自生活污水排放和大气降水,这种硫酸盐来源的变化与湿地补给水源的变化有关。
[Abstract]:As one of the important wetland surface environment, although only covers 6% of the earth's surface, it provides a living environment for the 20% known species on the earth, have irreplaceable ecological functions. Compared with other terrestrial ecosystems to wetland aquatic plants were the dominant species, and most aquatic plants have the ability to carry out photosynthesis by HCO3- karst area, surface water and underground water anions of HCO3-, to provide sufficient carbon source for the growth of aquatic vegetation. In addition, hydrological conditions is the formation of the wetland, determinants of development, but also control the wetland ecosystem in the biogeochemical processes and functions, and changes of water chemical characteristics and stable isotope wetland research can reveal the wetland water source ions, inorganic carbon and water, and through the inflow of wetland surface water and groundwater water chemistry and stable isotope The difference in composition between the exploration geochemical process of basin water chemical composition and stable isotope change control wetland. Based on this, we intend to the southwest karst area of Guizhou Weining Lake Basin as an example, analysis of variation in different seasons water chemistry and stable isotopes, the system research of Caohai watershed ion source, and reveal the earth the chemical process control of the wetland water chemical changes, are as follows: (1) in the surrounding surface water and groundwater water chemistry type is mainly Ca-HCO3, the chemical composition of the water is mainly affected by carbonate dissolution and human activities. The abundant water period Caohai wetland water chemistry type is Mg-HCO3, Mg-SO4. Ca-SO4 and Ca-HCO3, and the concentrations of major ions of Ca2+ and HCO3- decreased gradually from east to west, east of Wetland Water P H weakly acidic, low content of DO, EC, and Eh is negative, the display area Domain water reduction state, opposite West Water P H was alkaline, high DO content, low EC, Eh positive, showed that the side area water is oxidation state. The dry season water wetland water chemistry type is Ca-HCO3, the water quality difference variable parameter space. Based on small factors of wetland water chemical composition analysis found that due to high water period change of wetland water chemistry may be mainly related to wetland biogeochemical processes, and the dry season is mainly influenced by water evaporation. (2) the dissolved inorganic carbon isotope in high water period into the groundwater and river water in Caohai (8 ~ (13) C_ (DIC)) ranged from -13.66% ~-8.64%, the dry season 8 ~ (13) C_ (DIC) range of -12.61% ~-7.80%. DIC in groundwater mainly from carbonate dissolution and soil CO2, at the same time by the hydraulic wet season precipitation dilution and dry period of longer residence time. The seasonal variation of DIC concentration and isotope production in groundwater. Mainly from the DIC River in groundwater, affected photosynthesis and CO2 from river phytoplankton, the DIC isotopic composition of groundwater is relatively positive. Compared to the wet period of wetland water delta ~ (13) C_ (DIC) range of -15.13% ~-6.68%. The Eastern region P CO2 was higher than that of respiration of atmospheric P partial pressure of CO2 and plant roots and sediments, and the west region of P CO2 was lower than that of atmospheric P partial pressure of CO2 and submerged plant photosynthesis, isotopic composition by chemical fractionation and enhanced photosynthetic effect. The dry season 8 ~ (13) C_ (DIC) range -6.23% ~-0.06%, almost the entire surface of P CO2 was higher than that of Caohai atmospheric P partial pressure of CO2, CO2 from CO2 into the atmosphere, methane reduction and phytoplankton photosynthesis makes the dry season DIC isotope partial. (3) the current domain of Grass River, underground Analysis of water and wetland water oxygen isotope, groundwater and river water is mainly affected by the meteoric water. Wetland water have little difference to mixed isotope in vertical, but with the change of spatial and seasonal characteristics, dry season (D=-25.89 + 6.75 8%, 8 ~ (18) O=-2.24 1.12 +%) water hydrogen and oxygen isotopic composition of the wetland was higher than the wet period (delta D=-66.03 + 13.77 per thousand, 8 ~ (18) O=-8.31 2.23 +%), and lower than the wet period on the eastern side of the hydrogen and oxygen isotope composition on the west side, the dry season on the south side of isotope ratio is relatively high, the distribution characteristics and the distribution of aquatic vegetation, atmospheric humidity and water heat capacity. According to the results of isotope mass balance method, the wet period Caohai mainly accepted groundwater recharge and groundwater recharge in dry season is relatively small, mainly from meteoric water. (4) the high and low water periods in groundwater around the sulfur isotope average values were -14.40 % and -15.00%, the sulfur isotope average was -13.91% and -13.44%, and the average value of wetland water sulfur isotopes were -6.68 and 1.18 per 1000 person years. The study found that the wetland water water mainly from abundant sulfate in groundwater and precipitation, and the sulfate marsh water in dry season are mainly from sewage discharge and precipitation for this, sources of sulfate and the changes of wetland water supply changes.

【学位授予单位】：贵州大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：P59

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