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碳是构成生命的基础,在生物圈物质和能量循环中承担着主要作用[1-2]. 溶解无机碳(DIC)是海洋CO2体系的重要参数,占海水总碳的95%以上,对研究全球气候变化和碳循环具有重要的意义[3]. 沉积物是海水中DIC的重要来源之一[4],沉积物-水界面是有机物质在地球化学循环和生物系统之间进行耦合过程的主要场所[1,5],是DIC转移和储存的重要场所,研究沉积物-水界面DIC的交换通量对研究海水中DIC的循环具有重要作用.
目前,国内对沉积物-水界面DIC交换通量的研究主要集中在水产养殖塘[1,6]、湖泊[2,7]等生态系统,但关于沉积物-海水界面DIC交换通量的研究还鲜见报道. 国外报道,Lehrter等[8]研究了路易斯安那陆架海的沉积物-水界面DIC通量,认为沉积物-海水界面DIC通量对于大陆架碳循环具有重要意义,沉积物可能是初级生产的重要营养源. 另外,沉积物间隙水-上覆水的DIC浓度差、温度、盐度和pH等因素会影响沉积物-水界面的交换通量,改变上述条件会使沉积物-水界面交换通量发生显著变化[1,6,9].
陆架海对大气CO2的碳汇/源作用是导致全球CO2收支不确定性的重要因素之一[10],东海对大气CO2的碳汇/源作用具有季节性,长期以来是海洋碳循环研究的热点海域[11]. 长江口外海域是物理、化学和生物因素相互作用的例证,产生了特定的沉积物-水界面交换的空间格局[12].
本文研究了2021年夏季和秋季长江口外海域沉积物-水界面DIC的交换通量,并探究了DIC交换通量的影响因素,对于研究中国近海大陆架海水中DIC的迁移和转化、为东海陆架海碳循环体系研究提供数据支持,具有重要的实际意义.
夏、秋季长江口外海域沉积物-水界面溶解无机碳的交换通量
Study on the exchange flux of dissolved inorganic carbon at the sediment-water interface off the Yangtze River Estuary in summer and autumn
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摘要: 沉积物-海水界面是海洋中溶解无机碳(DIC)转移和储存的重要场所,长江口外海域拥有特定的沉积物-水界面交换的空间格局,研究其沉积物-水界面DIC的交换过程对于碳的循环和转化具有重要意义. 本研究于2021年8月和2021年10月在长江口外海域采集沉积物样品及原位底层海水,通过实验室模拟培养法计算了该海域沉积物-水界面DIC的交换通量,并研究了沉积物间隙水-上覆水的DIC浓度差、温度、盐度和pH对DIC交换通量的影响. 结果表明,夏季和秋季研究海域沉积物-水界面DIC交换通量平均值分别为(432.45±190.78)μmol·m−2 ·h−1和(223.05±110.39)μmol ·m−2·h−1. 夏季交换通量高于秋季,DIC扩散方向均由沉积物向上覆水释放,表明沉积物表现为DIC的“源”. 此外,交换通量会随着DIC浓度差或温度升高而升高,随着盐度或pH升高而降低.
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关键词:
- 长江口外海域 /
- 溶解无机碳(DIC) /
- 沉积物-水界面 /
- 交换通量.
Abstract: The sediment-seawater interface is an important zone for the transfer and storage of dissolved inorganic carbon (DIC) in the ocean. The sea area off the Yangtze Estuary has a specific spatial pattern of sediment-water interface exchange, which makes great significance to study the process of DIC exchange at the sediment-water interface for carbon cycle and transformation. The sediments and bottom seawater in situ were collected from the sea area off the Yangtze River Estuary in August 2021 and October 2021. The exchange flux of DIC at the sediment-water interface in the sea area was calculated by laboratory incubation method. Furthermore, the effects of the DIC concentration difference between the sediment interstitial water and the overlying water, temperature, salinity, and pH on the exchange flux of DIC were also studied. The results showed that the average value of DIC exchange fluxes at the sediment-water interface in the sea area in summer and autumn were (432.45±190.78) μmol·m−2· h−1 and (223.05±110.39) μmol· m−2 ·h−1, respectively. The exchange flux of DIC in summer was higher than that in autumn. The direction of DIC diffusion was released from the sediment to the overlying water, which indicated that the sediment appeared as the DIC “source”. In addition, the exchange flux of DIC would correspondingly increases with the increase of DIC concentration difference or temperature, and decreases with the increase of salinity or pH. -
表 1 采样站位表
Table 1. Sampling stations table
航次Cruise 站位Station 夏季 N0、N1、N2、N3、N4、N5、N6、N7、S1、S2、S3、S4、S5、S6、S7、M0、M1、M4、P1、P2 秋季 N0、N1、N2、N3、N4、N5、S1、S2、S3、S4、S5、M0、M1、M2、M3、P1、P2 表 2 夏季和秋季研究海域水体主要理化性质的比较
Table 2. Comparison of main physical and chemical properties of water column in the study sea area in summer and autumn and grain-size characteristics of sediments
长江口外海域
Yangtze River Estuary水体理化性质
Physicochemical properties of waters温度/℃
Temperature盐度
SalinitypH 溶解氧/
(mmol·L−1)
DO夏季 范围 19.96—27.78 13.62—34.32 6.31—7.44 0.09—0.20 均值 23.31±2.30 31.66±5.63 7.03±0.28 0.14±0.03 秋季 范围 20.02—23.64 12.15—34.28 7.86—8.02 0.10—0.27 均值 22.31±1.10 30.58±6.13 7.94±0.05 0.20±0.05 表 3 沉积物理化性质
Table 3. Sediment physicochemical properties
长江口外海域
Yangtze River Estuary沉积物粒度
Sediment grain size砂粒/%
Sand粉粒/%
Silt黏粒/%
Clay近岸 M0 3.9 93.1 3.1 M1 53.9 41.5 4.6 P2 21.2 74.6 4.2 S1 13.4 82.1 4.5 S2 10.0 85.5 4.2 S3 15.6 81.2 3.1 N0 3.5 87.0 9.5 N1 5.6 83.2 11.2 N2 4.5 83.8 11.6 N3 15.6 81.2 3.1 平均 14.7±15.03 79.4±14.10 5.9±3.44 远海 P1 54.3 40.0 5.7 S4 21.7 75.3 3.0 S5 21.3 75.5 3.2 N4 88.7 11.3 0 N5 62.1 35.8 2.1 平均 49.6±28.66 47.6±27.66 2.8±2.06 注:选取夏秋季共同采样站位,以123.5°E为近岸和远海的分界线.
Note:Select the common sampling stations in summer and autumn, and take 123.5°E as the boundary between nearshore and open sea.表 4 各站位沉积物-水界面DIC交换通量
Table 4. DIC exchange fluxes at sediment-water interface at different stations
站位
Station交换通量/(μmol· m−2·h−1)
Exchange flux站位
Station交换通量/(μmol· m−2·h−1)
Exchange flux夏季 Summer 秋季 Autumn 夏季 Summer 秋季 Autumn M0 606.13 286.63 S5 417.50 202.31 M1 537.81 389.19 S6 347.81 — M2 — 197.98 S7 393.56 — M3 — 89.29 N0 877.94 520.56 M4 234.63 — N1 901.31 144.38 P1 351.13 232.50 N2 280.56 126.13 P2 425.00 159.50 N3 584.06 261.31 S1 383.44 305.50 N4 196.88 113.00 S2 338.94 165.75 N5 438.56 114.69 S3 432.13 236.31 N6 378.94 — S4 300.63 246.88 N7 222.00 — 表 5 其他区域沉积物-水界面DIC交换通量的比较(μmol·m−2·h−1)
Table 5. Comparison of DIC exchange fluxes at sediment-water interface in other regions(μmol·m−2·h−1)
表 6 DIC交换通量与不同环境变量之间的Pearson相关系数
Table 6. Pearson correlation coefficient between DIC exchange flux and different environmental variables
相关分析项目
Analysis item相关系数
Correlation coefficient上覆水DIC浓度 −0.494** 间隙水DIC浓度 0.718** 温度 0.398* 盐度 −0.500** pH −0.494** 注:**P<0.01极显著相关,*P<0.05显著相关.
Note: **P<0.01 extremely significant correlation, *P<0.05 significant correlation.表 7 DIC交换通量和沉积物粒度的Pearson相关矩阵
Table 7. Pearson correlation matrix for DIC exchange flux and sediment grain size
砂粒/%
Sand粉粒/%
Silt黏粒/%
ClayDIC交换通量
DIC exchange fluxes砂粒/% 1 粉粒/% −0.993** 1 黏粒/% −0.544** 0.443* 1 DIC交换通量 −0.451* 0.413* 0.510** 1 注:**P<0.01极显著相关,*P<0.05显著相关.
Note:**P<0.01 extremely significant correlation,*P<0.05 significant correlation. -
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