Sources of Dissolved Inorganic Carbon in Two Small Streams with Different Bedrock Geology: Insights from Carbon Isotopes
Sources of Dissolved Inorganic Carbon in Two Small Streams with Different Bedrock Geology: Insights from Carbon Isotopes
复制标题
DOI：
10.2458/azu_rc.57.18348
复制
发表时间：
2015-04
期刊：
影响因子：
8.3
通讯作者：
N. Ishikawa;I. Tayasu;M. Yamane;Y. Yokoyama;S. Sakai;N. Ohkouchi
中科院分区：
文献类型：
--
作者：
N. Ishikawa;I. Tayasu;M. Yamane;Y. Yokoyama;S. Sakai;N. Ohkouchi
放射性碳自然丰度（Δ 14 C）越来越多地用于追踪河流生态系统中的碳循环。为了了解碳的最终来源，我们测定了日本中部两条小溪中溶解无机碳和有机碳（分别为DIC和DOC）以及颗粒有机碳（POC）的稳定碳同位素比值（δ 13 C）和Δ 14 C值，其中一条小溪流经石灰岩基岩（Seri），另一条小溪则没有流经石灰岩基岩（Fudoji）。四个季节的调查显示，DIC的Δ 14 C值（Seri为−238‰至−174‰，Fudoji为−23‰至+10‰）比其他碳组分的Δ 14 C值（DOC：Seri为−400‰至−138‰，Fudoji为−2‰至+103‰; POC：Seri为−164‰至−60‰，Fudoji为−55‰至+37‰）变化小。基于使用δ 13 C和Δ 14 C值的质量平衡计算，DIC中的碳比例源自（1）大气CO2，对于Seri为47%至57%，对于Fudoji为74%至90%，（2）有机物降解，对于Seri为29%至35%，对于Fudoji为4%至21%，（3）碳酸盐岩，Seri为14%~ 22%，Fudoji为4%~ 6%。我们将结果与以前在较大河流中进行的研究进行了比较，结果表明，在小河流中，大气CO2的溶解和碳酸盐岩的风化是碳循环中比有机物生物降解更重要的因素。
Radiocarbon natural abundances (Δ14C) are being increasingly used to trace carbon cycling in stream ecosystems. To understand the ultimate sources of carbon, we determined the stable carbon isotope ratios (δ13C) and Δ14C values of dissolved inorganic and organic carbon (DIC and DOC, respectively) and of particulate organic carbon (POC) in two small streams in central Japan, one of which flows over limestone bedrock (Seri) and the other does not (Fudoji). Investigations over four seasons revealed that the Δ14C values of the DIC (from −238‰ to −174‰ for Seri and −23‰ to +10‰ for Fudoji) were less variable than those of the other carbon fractions (DOC: from −400‰ to −138‰ for Seri and −2‰ to +103‰ for Fudoji; POC: from −164‰ to −60‰ for Seri and −55‰ to +37‰ for Fudoji). Based on mass balance calculations using the δ13C and Δ14C values, the proportions of carbon in the DIC originated from (1) atmospheric CO2 were 47% to 57% for Seri and 74% to 90% for Fudoji, (2) organic matter degradation were 29% to 35% for Seri and 4% to 21% for Fudoji, and (3) carbonate rock were 14% to 22% for Seri and 4% to 6% for Fudoji. We compared the results with previous studies that had been conducted in larger rivers and showed that in small streams, the dissolution of atmospheric CO2 and weathering of carbonate rock are more important factors in the carbon cycling than the biological degradation of organic matter.