水生植物对岩溶区河水地球化学昼夜变化的影响——以漓江为例
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摘要
为研究河流非岩溶区断面和岩溶区断面生物地球化学昼夜变化过程、特征及影响因素,探讨水生生物对岩溶区河水碳汇作用的影响,于2016年10月30日-2016年11月1日,在广西桂林漓江干流非岩溶区的峡背和岩溶区的省里设置两个监测点同时开展了为期48小时的高分辨率在线监测和高频率取样工作,研究其水文参数(电导率(EC)、水温(T)、pH以及Ca~(2+)、HCO_3~-、NO_3~-等离子和溶解无机碳同位素(δ~(13 )C_(DIC))等水化学参数的昼夜变化规律,并分析其影响因素。发现:(1)峡背和省里两断面水化学类型为HCO_3-Ca型,但水文地球化学昼夜变化过程不同:省里断面的物理化学参数昼夜变化显著,T、pH、DO、SIC白天上升夜间下降,Ca~(2+)、HCO_3~-的质量浓度和EC、p(CO_2)白天降低、夜晚上升;而峡背断面理化指标昼夜变幅小,这与峡背断面处于岩溶区与非岩溶区交界处,非岩溶河流汇入、生物量较小等环境特征有关。(2)省里断面营养元素(NO_3~-、SO_4~(2-)、Cl~-、Na~+)昼夜变化过程主要受水生植物同化作用控制,呈现白天降低、夜间升高的变化规律。(3)峡背断面和省里断面TOC与DOC白天上升、夜间下降,最高日变化幅度可达79%和61%,利用端元混合模型计算得出省里断面和峡背断面内源有机碳占总有机碳的比例分别为91.99%和88.39%,省里断面和峡背断面水生植物光合作用利用HCO_3~-作为无机碳源的比例为67.42%~99.75%和57.76%~69.78%,平均值分别为79.54%和63.13%。(4)省里断面溶解无机碳(DIC)变化范围为67.1~115.9mg·L~(-1),平均值为96.5mg·L~(-1),呈现白天下降夜间上升的变化。δ~(13 )C_(DIC)变化范围-7.8‰~-9.9‰,平均值为-8.9‰,表现为白天偏重、晚上偏轻的动态变化,两者呈显著的负相关关系(相关系数为-0.79)。研究表明省里断面水生植物光合作用和呼吸作用以及钙沉降是控制DIC昼夜变化的主导因素。通过估算监测期间省里断面光合作用DIC转化速率平均值为1.2×10~(-5 )mmol·L~(-1)·S~(-1),Ca~(2+)离子的沉积速率平均值为0.18×10~(-5 )mmol·L~(-1)·S~(-1)。因此,岩溶区河段水生生物光合作用及其固碳能力较非岩溶区河段明显增强。
The purpose of this work was to study the characteristics and influence factors of the biogeochemical diurnal variation process in the river section of non-karst and karst areas and discuss the effect of aquatic organisms on the river carbon sink in karst areas,especially the diel variations and influence factors of hydrochemistry in karst rivers.Taking the Lijiang River in Guilin City of Guangxi Zhuang Autonomous Region,China as an example,two monitoring sites were set up separately at Xiabei(non-karst)and Shengli(karst).Physical and hydrogeochemical parameters including pH,dissolved oxygen(DO),water temperature(T),electrical conductivity(EC),dissolved inorganic carbon(DIC),isotopes and other chemical parameters were examined by high-resolution on-line monitoring and high-frequency sampling conducted from 30November to1October 2016.The results show that(1)Xiabei and Shengli sites are both of HCO_3-Ca type water,however showing different diel variations of the hydrogeochemical process.The diel variations of physical and chemical parameters(EC,DO,pH,T,and major ions HCO_3~-,NO_3~-,Na~+,Cl~-,SO_4~(2-))at Shengli site are notable,showing regular diel variation in the monitoring,while those at Xiabei are relatively smaller,which is probably related to the special environment of the border between karst and the non-karst areas,where exist less aquatic plants.(2)The diurnal changes of nutrient elements(NO_3~-,SO_4~(2-),Cl~-,Na~+)in the Shengli section are mainly controlled by assimilation of aquatic plants with a trend that increases in daylight and decreases at night.(3)The data of TOC and DOC show a daytime increase and nighttime decrease cycle,and their maximum daily changes are 79%and 61%,respectively.TOC is mainly derived from the primary productivity of aquatic organisms.The proportion of HCO_3~-in inorganic carbon sources taken advantage by aquatic plants ranges from 67.42%to 99.75%and 57.76%to 69.78%,with average values 79.54%and63.13%,respectively.(4)The concentration dissolved inorganic carbon(DIC)in Shengli section varies from67.1to 115.9mg·L~(-1 )with an average value of 96.5mg·L~(-1).The variation ofδ~(13 )C_(DIC)ranges from-7.8‰to-9.9‰with an average value of-8.9‰.The dissolved inorganic carbon(DIC)andδ~(13)C_(DIC)at the Shengli site shows a reverse characteristic in diurnal fluctuations,where the dissolved inorganic carbon decreases in daylight and increases at night whileδ~(13)C_(DIC)increases in daylight and decreases at night.The dissolved inorganic carbon has a negative correlation with theδ~(13)C_(DIC)(with correlation coefficient-0.79).It was found that the circadian variation of dissolved inorganic carbon is controlled by photosynthesis and respiration of aquatic plants and calcium deposition.According to the diurnal amplitude of the dissolved inorganic carbon(DIC)and calcium concentrations,the mean conversion rate of the dissolved inorganic carbon(DIC)by aquatic vegetation photosynthesis at Shengli site was calculated to be 1.2×10~(-5 )mmol·L~(-1)·S~(-1 )and the average Ca precipitation rate was estimated to be 0.18×10~(-5 )mmol·L~(-1)·S~(-1).In conclusion,the photosynthesis and carbon sink capacity of aquatic organisms in the river segment of karst areas are significantly enhanced compared with that in non-karst areas.
The purpose of this work was to study the characteristics and influence factors of the biogeochemical diurnal variation process in the river section of non-karst and karst areas and discuss the effect of aquatic organisms on the river carbon sink in karst areas,especially the diel variations and influence factors of hydrochemistry in karst rivers.Taking the Lijiang River in Guilin City of Guangxi Zhuang Autonomous Region,China as an example,two monitoring sites were set up separately at Xiabei(non-karst)and Shengli(karst).Physical and hydrogeochemical parameters including pH,dissolved oxygen(DO),water temperature(T),electrical conductivity(EC),dissolved inorganic carbon(DIC),isotopes and other chemical parameters were examined by high-resolution on-line monitoring and high-frequency sampling conducted from 30November to1October 2016.The results show that(1)Xiabei and Shengli sites are both of HCO_3-Ca type water,however showing different diel variations of the hydrogeochemical process.The diel variations of physical and chemical parameters(EC,DO,pH,T,and major ions HCO_3~-,NO_3~-,Na~+,Cl~-,SO_4~(2-))at Shengli site are notable,showing regular diel variation in the monitoring,while those at Xiabei are relatively smaller,which is probably related to the special environment of the border between karst and the non-karst areas,where exist less aquatic plants.(2)The diurnal changes of nutrient elements(NO_3~-,SO_4~(2-),Cl~-,Na~+)in the Shengli section are mainly controlled by assimilation of aquatic plants with a trend that increases in daylight and decreases at night.(3)The data of TOC and DOC show a daytime increase and nighttime decrease cycle,and their maximum daily changes are 79%and 61%,respectively.TOC is mainly derived from the primary productivity of aquatic organisms.The proportion of HCO_3~-in inorganic carbon sources taken advantage by aquatic plants ranges from 67.42%to 99.75%and 57.76%to 69.78%,with average values 79.54%and63.13%,respectively.(4)The concentration dissolved inorganic carbon(DIC)in Shengli section varies from67.1to 115.9mg·L~(-1 )with an average value of 96.5mg·L~(-1).The variation ofδ~(13 )C_(DIC)ranges from-7.8‰to-9.9‰with an average value of-8.9‰.The dissolved inorganic carbon(DIC)andδ~(13)C_(DIC)at the Shengli site shows a reverse characteristic in diurnal fluctuations,where the dissolved inorganic carbon decreases in daylight and increases at night whileδ~(13)C_(DIC)increases in daylight and decreases at night.The dissolved inorganic carbon has a negative correlation with theδ~(13)C_(DIC)(with correlation coefficient-0.79).It was found that the circadian variation of dissolved inorganic carbon is controlled by photosynthesis and respiration of aquatic plants and calcium deposition.According to the diurnal amplitude of the dissolved inorganic carbon(DIC)and calcium concentrations,the mean conversion rate of the dissolved inorganic carbon(DIC)by aquatic vegetation photosynthesis at Shengli site was calculated to be 1.2×10~(-5 )mmol·L~(-1)·S~(-1 )and the average Ca precipitation rate was estimated to be 0.18×10~(-5 )mmol·L~(-1)·S~(-1).In conclusion,the photosynthesis and carbon sink capacity of aquatic organisms in the river segment of karst areas are significantly enhanced compared with that in non-karst areas.
引文
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[30]张陶,蒲俊兵,袁道先,等.亚热带典型岩溶区地表溪流水文地球化学昼夜变化及其影响因素研究[J].环境科学,2014,35(8):2944-2951.
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[33]莫雪,蒲俊兵,袁道先,等.亚热带典型岩溶区地表溪流溶解无机碳昼夜变化特征及其影响因素[J].第四纪研究,2014,34(4):873-880.
[34]吕保樱,刘再华,廖长君,等.水生植物对岩溶水化学日变化的影响:以桂林岩溶水文地质试验场为例[J].中国岩溶,2006,25(4):335-340.
[35] Hayashi M,Vogt T,Mchler L,et al.Diurnal fluctuations of electrical conductivity in a pre-alpine river:Effects of photosynthesis and groundwater exchange[J].Journal of Hydrology,2012,(s450-451):93-104.
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[2]袁道先.地质作用与碳循环研究的回顾和展望[J].科学通报,2011,56(26):2157-2157.
[3]章程,汪进良,蒲俊兵.地下河出口河流水化学昼夜动态变化:生物地球化学过程的控制[J].地球学报,2015,36(2):197-203.
[4]苏睿丽,李伟.沉水植物光合作用的特点与研究进展[J].植物学通报,2005(S1):128-138.
[5]蒲俊兵.重庆地区岩溶地下河水溶解无机碳及其稳定同位素特征[J].中国岩溶,2013,32(2):123-132.
[6]张强.岩溶地质碳汇的稳定性:以贵州草海地质碳汇为例[J].地球学报,2012,33(6):947-952.
[7]章程.岩溶区河流水化学昼夜变化与生物地球化学过程[J].中国岩溶,2015,34(1):1-8.
[8]刘再华,李强,孙海龙,等.云南白水台钙华水池中水化学日变化及其生物控制的发现[J].水文地质工程地质,2005,32(6):10-15.
[9]章程,汪进良,谢运球,等.桂林会仙岩溶湿地水化学昼夜动态变化及其影响因素[J].地质论评,2013,59(6):1235-1241.
[10]张红波,何师意,于奭,等.夏季岩溶区河流的水化学及碳汇动态变化:以桂林漓江为例[J].西南师范大学学报(自然科学版),2013,38(3):55-61.
[11]蒲俊兵.重庆岩溶地下水氢氧稳定同位素地球化学特征[J].地球学报,2013,34(6):713-722.
[12]陈崇瑛,刘再华.喀斯特地表水生生态系统生物碳泵的碳汇和水环境改善效应[J].科学通报,2017,62(30):3440-3450.
[13]章程,肖琼,苗迎,郭永丽,汤庆佳,郝玉培.广西桂林漓江典型河段水化学昼夜动态变化及其对岩溶碳循环的影响[J/OL].地球学报:1-9[2018-08-31].http://kns.cnki.net/kcms/detail/11.3474.p.20180815.1253.003.html.
[14]邓自强,林玉石,张美良,等.桂林地质构造与岩溶地貌发育的时序关系[J].中国岩溶,1986,5(4):289-296.
[15]韩耀全,周解,吴祥庆.漓江的自然地理与水质调查[J].广西水产科技,2007(2):8-16.
[16]黄家城.桂林漓江志[M].南宁:广西人民出版社,2004:112-125.
[17]刘再华.碳酸盐岩岩溶作用对大气CO2沉降的贡献[J].中国岩溶,2000,19(4):293-300.
[18]王瑞久.三线图解及其水文地质解释[J].工程勘察,1983(6):6-11.
[19]黄芬,唐伟,汪进良,等.外源水对岩溶碳汇的影响:以桂林毛村地下河为例[J].中国岩溶,2011,30(4):417-421.
[20]袁元,钟鸿雁.水生植物对水体pH值影响的原因探究[J].江西化工,2008(02):62-64.
[21] Wetzel R G.Death,detritus,and energy flow in aquatic ecosystems[J].Freshwater Biology,1995,33(1):83-89.
[22] Kuserk F T,Kaplan L A,Bott T L.In situ measures of dissolved organic carbon flux in a rural stream[J].Canadian Journal of Fisheries&Aquatic Sciences,1984,41(6):964-973.
[23] Nimick D A,Gammons C H,Parker S R.Diel biogeochemical processes and their effect on the aqueous chemistry of streams:A review[J].Chemical Geology,2011,283(1):3-17.
[24] Spencer R G M,Pellerin B A,Bergamaschi B A,et al.Diurnal variability in riverine dissolved organic matter composition determined by in situ optical measurement in the San Joaquin River(California,USA)[J].Hydrological Processes,2007,21(23):3181-3189.
[25] Parker S R,Poulson S R,Smith M G,et al.Temporal variability in the concentration and stable carbon isotope composition of dissolved inorganic and organic carbon in two montana,USA Rivers[J].Aquatic Geochemistry,2010,16(1):61-84.
[26]原雅琼.水生光合生物对漓江流域水化学和岩溶碳汇的影响[D].重庆:西南大学,2016.
[27]唐文魁,陶贞,高全洲,等.桂江主要离子及溶解无机碳的生物地球化学过程[J].环境科学,2014,35(6):2099-2107.
[28] Tamooh F,Borges A V,Meysman F J R,et al.Dynamics of dissolved inorganic carbon and aquatic metabolism in the Tana River Basin,Kenya[J].Biogeosciences,2013,10(11):6911-6928.
[29]李丽,蒲俊兵,李建鸿,等.岩溶地下河补给的地表溪流溶解无机碳及其稳定同位素组成的时空变化[J].环境科学,2017,38(2):527-534.
[30]张陶,蒲俊兵,袁道先,等.亚热带典型岩溶区地表溪流水文地球化学昼夜变化及其影响因素研究[J].环境科学,2014,35(8):2944-2951.
[31] Stumm W,Morgan J J.Aquatic chemistry:chemical equilibria and rates in naturalwaters[J].Cram101Textbook Outlines to Accompany,1995,179(11):A277.
[32]于正良,杨平恒,赵瑞一,等.春季生物作用对山地岩溶池水地球化学特征的影响[J].环境科学,2015,36(4):1263-1269.
[33]莫雪,蒲俊兵,袁道先,等.亚热带典型岩溶区地表溪流溶解无机碳昼夜变化特征及其影响因素[J].第四纪研究,2014,34(4):873-880.
[34]吕保樱,刘再华,廖长君,等.水生植物对岩溶水化学日变化的影响:以桂林岩溶水文地质试验场为例[J].中国岩溶,2006,25(4):335-340.
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