溶解无机碳稳定同位素分析样品的前处理方法及黄渤海夏季数据初步分析  

An optimization of the acid-extraction pretreatment procedure for precisely detecting stable isotopic composition of seawater dissolved inorganic carbon:Its application in the Bohai and Yellow Seas

作　　者：刘朔江 杨庶 刘梦梦 张永[1] 翟惟东 LIU Shuojiang;YANG Shu;LIU Mengmeng;ZHANG Yong;ZHAI Weidong(Institute of Marine Science and Technology,Shandong University,Qingdao,266237,China)

机构地区：[1]山东大学,海洋研究院,青岛266237

出　　处：《环境化学》2021年第7期2115-2124,共10页Environmental Chemistry

基　　金：山东省自然科学基金(ZR2018MD019)资助.

摘　　要：设计并优化了一套海水中溶解无机碳(DIC)稳定同位素(δ13CDIC)的预处理装置,并通过光腔衰荡光谱法对其进行分析测定.在整个预处理及测定过程,通过向海水样品中添加磷酸并在高纯氮气的吹扫下使用气体采样袋收集其产生的CO_(2)气体,随后将气体采样袋连接Picarro G2121-i型仪器进行δ13CDIC的测定.通过对影响因素的研究确定了预处理条件为:海水样品体积30 mL,85%(V/V)浓磷酸使用量1 mL,吹扫流速150 mL·min^(−1),吹扫时间4 min 20 s,仪器测定时间约10 min.在此条件下DIC回收率超过99%,且δ13CDIC的测定标准偏差小于0.1‰,极差小于0.2‰.基于此条件,对2019年夏季黄渤海典型断面不同水层的δ13CDIC进行了测定.表层海水中δ13CDIC数据大部分集中在−0.5‰与0.5‰之间,其中黄海表层平均值为−0.2‰±0.5‰;底层海水中δ13CDIC在−2.0‰至−0.4‰的范围内,平均值为−1.3‰±0.5‰.这种表层高、底层低的整体趋势主要受控于海气交换、光合作用、呼吸/矿化作用等生物地球化学过程,也与这两个海域经常发生夏季底层水耗氧酸化现象一致.本研究为海水中δ13CDIC水样的前处理提供了一种经济、高效的手段.We designed and optimized an acid-extraction pretreatment procedure for precisely detecting stable isotopic composition of seawater dissolved inorganic carbon(δ13CDIC).The CO_(2) was generated by adding phosphoric acid to the seawater samples,and collected in a gas sampling bag under the purge of nitrogen.Then,the gas sample was injected to a cavity ring-down spectroscopy analyzer(model:Picarro G2121-i)forδ13CDIC determination.The pretreatment conditions were optimized as follows:30 mL seawater sample,1 mL phosphoric acid(85%(V/V)),150 mL·min^(−1)carrier gas flow rate,4 min 20 s purge time,10 min isotope determination.Under these conditions,the sample recovery of dissolved inorganic carbon(DIC)was more than 99%,the standard deviation ofδ13CDIC determination was estimated to be less than 0.1‰,and the range was less than 0.2‰.Appling this procedure,we determined summertime distributions ofδ13CDIC in the Bohai and Yellow Seas in 2019.Most surfaceδ13CDIC values ranged between−0.5‰and 0.5‰,with an average of−0.2‰±0.5‰in Yellow Sea surface waters.δ13CDIC in bottom waters ranged from−2.0‰to−0.4‰,with an average of−1.3‰±0.5‰.The generalδ13CDIC pattern could be explained by common biogeochemical processes such as air-sea gas exchange,photosynthesis and respiration/mineralization.It was also consistent with the earlier-reported summertime oxygen-depletion and seasonal acidification in the two coastal oceans.This study provides an efficient and reliable technique for the precision determination ofδ13CDIC in seawater.

关 键 词：黄渤海 溶解无机碳 碳稳定同位素 光腔衰荡光谱技术 

分 类 号：P736.44[天文地球—海洋地质]