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Acid-base properties of dissolved organic matter from pristine and oil-impacted marshes of Barataria Bay, Louisiana

机译:来自路易斯安那州巴拉塔里亚湾的原始和油污沼泽中溶解的有机物的酸碱性质

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Five samples of dissolved organic matter (DOM) were isolated from Barataria Bay, Louisiana using the coupled reverse osmosis/electrodialysis method. Two of the samples (BU) were isolated from relatively pristine waters and three samples (BC) were isolated from waters that were strongly impacted by the Deepwater Horizon oil spill in April-July, 2010. The acid-base properties of these five samples were investigated by potentiometric titration. Carboxyl contents were estimated using an empirical pH-based method, and carboxyl contents, average pK_a'S, and the range of pK_a in each sample were determined by fitting two numerical models (the Gaussian distribution model and the modified Henderson-Hasselbalch model) to the titration data. The carboxyl contents of the titrated samples range from 6.0 to 6.9 meq gC~(-1) and the average pK_a's for carboxyl groups range from 4.0 to 4.6. The distribution of pK_a values is somewhat broader for the BU samples than for the BC samples, but all other acid-base properties of the five samples were comparable. Phenolic hydroxyl groups could not be detected in any of the samples. These samples of coastal DOM are much less acidic than fulvic acids from soils and fresh waters.
机译:使用反渗透/电渗析方法从路易斯安那州的巴拉塔里亚湾分离了五种可溶性有机物(DOM)样品。其中两个样品(BU)是从相对原始的水中分离出来的,三个样品(BC)是从2010年4月至7月受Deepwater Horizo​​n漏油事件严重影响的水中分离出来的。这五个样品的酸碱特性为通过电位滴定法进行研究。使用基于经验的pH的方法估算羧基含量,并通过拟合两个数值模型(高斯分布模型和改良的Henderson-Hasselbalch模型)确定每个样品中的羧基含量,平均pK_a'S和pK_a范围数据。滴定样品的羧基含量为6.0至6.9 meq gC〜(-1),羧基的平均pK_a为4.0至4.6。 BU样品的pK_a值分布比BC样品的分布宽一些,但五个样品的所有其他酸碱性质均相当。在任何样品中均未检测到酚羟基。这些沿海DOM样品的酸性远低于土壤和淡水中的富勒酸。

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