广西官村岩溶溪流中生物地球化学控制的DIC和NO3^-昼夜变化研究  

Biogeochemical Controls on Daily Cycling of DIC and NO_3^- of Guancun Karst Stream in Guangxi

作　　者：张陶[1,2] 蒲俊兵[1] 袁道先[1,2] 李建鸿[1,2] 

机构地区：[1]中国地质科学院岩溶地质研究所,国土资源部广西岩溶动力学重点实验室,联合国教科文组织国际岩溶研究中心,广西桂林541004 [2]西南大学地理科学学院,重庆400715

出　　处：《地质学报》2016年第8期1965-1977,共13页Acta Geologica Sinica

基　　金：国家自然科学基金项目(编号:41572234,41202185);中国地质科学院基本科研业务费项目(编号:YYWF201636);国家重点研发计划项目(编号:2016YFC0502501);中国地质调查局地质调查项目(编号:DD20160305-03);国土资源部公益性行业科研专项(201311148)联合资助的成果

摘　　要：为了解岩溶区控制溪流中溶解无机碳(DIC)和NO_3^-昼夜变化的生物地球化学过程以及DIC和NO_3^-日变化量,于2014-07-22~2014-07-24期间,在广西壮族自治区融安县官村溪流中包括地下河出口(CK)和下游雷崖村(LY)设置两个监测点同时对水体物理化学参数以及C、N同位素(δ^(13) CDIC、δ^(15) N-NO_3^-和δ^(18) O-NO_3^-)展开了为期2d的高分辨率昼夜监测采样工作。结果发现CK点各物理化学参数没有表现出昼夜变化,但是LY点Ca2+、DIC以及PCO2表现出明显的昼夜变化规律,即白天下降夜间上升且与DO和pH表现出明显的负相关关系。相对于CK点,在白天水生光合生物光合作用导致LY点DIC下降的同时δ^(13) CDIC上升,而在夜间呼吸作用导致LY点DIC上升的同时δ^(13) CDIC下降且部分时间段要低于CK点δ^(13) CDIC值。溪流中的NH4+在监测期间基本上都在下降而NO_3^-离子在夜间和上午时间段都在上升,δ^(15) N-NO_3^-却表现出下降的趋势,且比较接近δ^(15) N-NO_3^-初始值,而NO_3^-离子在下午时间段出现下降的趋势。结果表明溪流中DIC昼夜变化主要受到水生植物的光合作用和呼吸作用控制,且通过质量平衡方程计算得知溪流中由于光合作用吸收无机碳而转为有机碳的量为0.94kgC/d,这部分有机碳可以形成相对长期稳定的自然C汇。溪流在夜间和上午时间段发生了N的硝化作用,增长量为2.08kgN/d,但在下午时间段(12:00~18:00)发生了N的同化作用,损失量为0.42kgN/d。溪流输出的NO_3^--N的量为1.66kgN/d,表明在富碳、富钙的岩溶溪流中,有利于水生光合生物的生长,促进N的同化作用的发生,从而减少溪流输出NO_3^--N的量,说明岩溶区溪流N的生物地球化学过程可能在昼夜尺度上改变水质。In order to understand the biogeochemical process of controlling daily cycling of DIC and NO3^- , and their daily variation in a karst stream, this paper installed two monitoring sites including subterranean river outlet （CK） and surface creek mouth （LY） in Guancun stream, which are located at Guancun Village and Leiya Village, Daliang Township, Rong＇an County of Guangxi Zhuang Autonomous Region, China, to carried out a diurnal monitoring and sampling work by high time-resolution for two days for physical and chemical parameters, N and C isotopes （δ^13CDIC,δ^15N-NO3^- and δ^18O-NO3^-） in water. Research results revealed physical and chemical parameters in CK site were stable basically, while Ca^2＋ , DIC and PCO2 in LY site showed apparent diurnal variations, i.e. increased during the daytime and decreased at night, and showed a significant negative correlation with DO and pH. Compared to CK site, photosynthesis led to the decline of DIC and the increased of δ^13CDIC during the day, while respiration caused the increased of DIC and the decline of δ^13CDIC in LY site which was even lower than δ^13CDIC in CK site. NH4^ ＋ of stream decreased basically and NO3^- increased at night and morning during monitoring, while δ^15N-NO3^- showed a downward trend and relatively close to the initial value of δ^15N-NO3^- , and NO3^- appeared decline trend at afternoon. Results indicate that photosynthesis and respiration of aquatic plants control daily cycling of DIC in stream, and it was calculated through the mass balance equation knowing that the amount of inorganic carbon converted to organic carbon by photosynthesis was 0.94kgC/d, which could form a relative long-term stable carbon sink. Stream water was influenced mainly by nitrification at night and morning, which the amount of growth was 2.08 kgN/d, however stream water was influenced by assimilation at afternoon, which the amount of losing was 0.42 kgN/d. The output amount of stream＇s NO3^--N was 1.66 kgN/d, showing that it was conducive to the

关 键 词：DIC NO3^- 昼夜变化 生物地球化学过程 有机碳 NO3^--N 官村溪流 

分 类 号：P593[天文地球—地球化学]