Analyses of dissolved organic carbon in seawater: the JGOFS EqPac methods comparison
Analyses of dissolved organic carbon in seawater: the JGOFS EqPac methods comparison
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DOI：
10.1016/0304-4203(94)00040-k
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发表时间：
1995
期刊：
影响因子：
3
通讯作者：
J. Sharp;R. Benner;L. Bennett;C. Carlson;S. Fitzwater;E. Peltzer;L. Tupas
中科院分区：
文献类型：
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作者：
J. Sharp;R. Benner;L. Bennett;C. Carlson;S. Fitzwater;E. Peltzer;L. Tupas
溶解有机碳（DOC）的方法比较的结果在这里，其中五个高温燃烧（HTC）的仪器和湿化学氧化（WCO）的方法被用于一系列的海洋样品。这些样品是在美国JGOFS赤道太平洋巡航（EqPac）期间收集的，大多数作者参与了EqPac计划的DOC分析。采用“清洁”方案采集样品，并立即在重复样品瓶中快速冷冻。第一提交人将这些样本分发给其他提交人，供他们稍后在陆地上对储存的样本进行“盲”分析。三种HTC仪器和WCO方法的结果相当（±7.5%）。有困难的其他两个HTC方法的解释和改进提供。可比较DOC值的单个最关键要素似乎是评估和减去总仪器空白（或WCO方法的试剂和处理空白）。“零”碳（极低C）水样有助于所有分析员对单个仪器或方法空白进行统一评估。燃烧管中催化剂床的“调节”对于实现一致的低仪表空白至关重要。未能彻底调节催化剂床可能是一个重大错误，可能会错误地为海洋样品提供高DOC值。所有分析员均可使用的参比标准品也可用于比较仪器和方法性能。证明了污染问题，并表明仔细的制备和处理可以减少污染样品产生错误的可能性。结果表明，赤道太平洋近表面沃茨海水DOC值为60-70 μM C，深水DOC值为35-40 μM C。由于“零”碳水含有少量但可测量的DOC，因此此处报告的样本值可能略低。由于最低仪器空白相当于约10 μM C，因此建议即使完全没有仪器空白并且所有这些“空白”都在“零”碳水中，海洋样品浓度也不能低估超过10 μM C。
Results of a dissolved organic carbon (DOC) methods comparison are presented here in which five high temperature combustion (HTC) instruments and a wet chemical oxidation (WCO) method were used on a series of oceanic samples. The samples were collected during US JGOFS Equatorial Pacific Ocean cruises (EqPac) and most of the authors were involved with DOC analyses for the EqPac Program. Samples were collected with a “clean” protocol and were immediately quick frozen in replicate sample bottles. They were distributed by the first author to the other authors for “blind” analyses later on land on the stored samples. Comparable results (±7.5%) were found by three HTC instruments and the WCO method. There were difficulties with the other two HTC methods for which explanations and improvements are offered. The single most critical element for comparable DOC values appears to be assessment and subtraction of the total instrument blank (or reagent and handling blank for WCO methods). A “zero” carbon (very low C) water sample assisted in having all analysts achieve a uniform assessment of individual instrument or methods blanks. “Conditioning” of the catalyst bed in the combustion tube is critical to achieve consistent low instrument blanks. Failure to thoroughly condition the catalyst bed may be a significant error that can give erroneously high DOC values for oceanic samples. Reference standards available to all analysts also allowed comparison of instrument and methods performance. Contamination problems were demonstrated and it was shown that careful preparation and handling can reduce the potential for errors from contaminated samples. Results indicate that Equatorial Pacific oceanic DOC values in near surface waters are on the order of 60–70 μM C and deep water values on the order of 35–40 μM C. Since the “zero” carbon water contained a small, but measurable, amount of DOC, the sample values reported here may be slightly low. Because the lowest instrument blanks were equivalent to about 10 μM C, it is suggested that even if there were no instrument blank at all and all this “blank” were in the “zero” carbon water, the oceanic sample concentrations could not be underestimated by more than 10 μM C.