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Spectrophotometric Measurement of Calcium Carbonate Saturation States in Seawater

机译：分光光度法测定海水中碳酸钙的饱和状态

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摘要

Measurements of ocean pH and carbonate ion concentrations in the North Pacific and Arctic Oceans were used to determine calcium carbonate saturation states (Ω_(caco_3),) from spectrophotometric methods alone. Total carbonate ion concentrations, [CO_3~(2-)]_T, were for the first time at sea directly measured using Pb(II) UV absorbance spectra. The basis of the method is given by the following: -log[CO_3~2),_(fspoc)=log{(co3β_1)/(e_2)} + log{(R-e_1)/(I-/fe_3/e_2)} where co3β_1 is the PbCO_3° formation constant, e_i are molar absorptivity ratios, and R = _(250)A/_(234)A (ratio of absorbances measured at 250 and 234 nm). On the basis of shipboard and laboratory Pb(Ⅱ) data and complementary carbon-system measurements, the experimental parameters were determined to be (25 ℃) the following: log{(co3β_1)/(e_2)} =5.513-5.358×10~(-2)+ 5.166×10~(-4)S~2 e_1 = 0,2293-5.554 × 10~(-1)S +8.440 × 10~(-5).S~2 (e_3/e_2) ≈ 3.091 -8.730 × 10~2 S + 9.363 × 10~4S~2 The resulting mean difference between the shipboard spectrophotometric and conventional determinations of [CO_3~(2-)]_T was ±2.03 μmol kg~(-1). The shipboard analytical precision of the Pb(Ⅱ) method was ～1.71 μmol kg~(-1) (2.28%). Spectrophotometric [CO_3~(2-)]_T and pH_T were then combined to calculate Ω_(caco_3)· For the case of aragonite, 95% of the spectrophotometric aragonite saturation states (Ω_(Aspec)) were within ±0.06 of the conventionally calculated values (Ω_(Acalc)) when 0.5 ≤ Ω_A ≤ 2.0. When Ω_A > 2.0, 95% of the Ω_(Aspec) values were within ±0.18 of Ω_(caco_3)· Our shipboard experience indicates that spectrophotometric determinations of [CO_3~(2-)]_T and Ω_(caco_3) are straightforward, fast, and precise. The method yields high-quality measurements of two important, rapidly changing aspects of ocean chemistry and offers capabilities suitable for long-term automated in situ monitoring.
机译：仅通过分光光度法就可以测量北太平洋和北冰洋的海洋pH和碳酸根离子浓度，从而确定碳酸钙的饱和状态（Ω_（caco_3））。使用Pb（II）UV吸收光谱法直接在海上首次测量了总碳酸盐离子浓度[CO_3〜（2-）] _ T。该方法的基础如下：-log [CO_3〜2），_（fspoc）= log {（co3β_1）/（e_2）} + log {（R-e_1）/（I- / fe_3 / e_2） ）}其中co3β_1是PbCO_3°的形成常数，e_i是摩尔吸收率，R = _（250）A / _（234）A（在250和234 nm处测得的吸光度比）。根据船上和实验室的Pb（Ⅱ）数据和互补碳系统测量，确定实验参数为（25℃）以下：log {（co3β_1）/（e_2）} = 5.513-5.358×10〜 （-2）+ 5.166×10〜（-4）S〜2 e_1 = 0,2293-5.554×10〜（-1）S +8.440×10〜（-5）.S〜2（e_3 / e_2）≈翻译3.091 -8.730×10〜2 S + 9.363×10〜4S〜2船上分光光度法与常规测定[CO_3〜（2-）] _ T的平均差为±2.03μmolkg〜（-1）。 Pb（Ⅱ）法的船上分析精度为〜1.71μmolkg〜（-1）（2.28％）。然后将分光光度法[CO_3〜（2-）] _ T和pH_T合并计算Ω_（caco_3）·对于文石，分光光度法文石饱和状态（Ω_（Aspec））的95％处于常规计算值的±0.06以内0.5≤Ω_A≤2.0时的值（Ω_（Acalc））。当Ω_A> 2.0时，95％的Ω_（Aspec）值在Ω_（caco_3）的±0.18内。我们的船上经验表明，分光光度法测定[CO_3〜（2-）] _ T和Ω_（caco_3）简便，快速。 ，且精确。该方法可对海洋化学的两个重要且快速变化的方面进行高质量的测量，并提供适用于长期自动原位监测的功能。

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  • 来源
    《Environmental Science & Technology》 |2013年第3期|1468-1477|共10页
  • 作者

    Regina A. Easley; Mark C. Patsavas; Robert H. Byrne; Xuewu Liu; Richard A. Feely; Jeremy T. Mathis;

  • 作者单位

    College of Marine Science, University of South Florida, St. Petersburg, Florida 33701, United States;

    College of Marine Science, University of South Florida, St. Petersburg, Florida 33701, United States;

    College of Marine Science, University of South Florida, St. Petersburg, Florida 33701, United States;

    College of Marine Science, University of South Florida, St. Petersburg, Florida 33701, United States;

    NOAA Pacific Marine Environmental Laboratory, Seattle, Washington 98115, United States;

    School of Fisheries and Ocean Sciences, University of Alaska Fairbanks, Fairbanks, Alaska 99775, United States;

  • 收录信息 美国《科学引文索引》(SCI);美国《工程索引》(EI);美国《生物学医学文摘》(MEDLINE);美国《化学文摘》(CA);
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