Graduate School of Agricultural Science, Kobe University, 1-1 Rokkodai, Nada, Kobe, Hyogo, 657-8501, Japan.
Graduate School of Agricultural Science, Kobe University, 1-1 Rokkodai, Nada, Kobe, Hyogo, 657-8501, Japan.
Water Res. 2019 Oct 15;163:114901. doi: 10.1016/j.watres.2019.114901. Epub 2019 Jul 22.
This study characterized dissolved organic matter (DOM) obtained from 47 lakes and 2 streams on ice-free areas at Lützow-Holm Bay and Amundsen Bay in East Antarctica (n = 74), where few biogeochemical studies have been historically conducted. Samples were analyzed for basic water chemistry and by resin fractionation, UV-vis spectroscopy, and excitation emission matrix spectroscopy combined with parallel factor analysis (EEM-PARAFAC). Salinity of the samples ranged very broadly from fresh to hypersaline as a result of evaporative concentration. There was a clear positive correlation between log-salinity and the spectral slopes of DOM (S), an indicator of photodegradation. Thus, we interpreted the correlation as a progression of photodegradation by prolonged water retention time. Of the identified seven PARAFAC components, three ubiquitous humic-like components decreased as photodegradation progressed, while a photorefractory UVC humic-like component increased its relative abundance. A non-humic component, traditionally defined as Peak N, did not show a trend depending on photodegradation, and its level was high in nutrient-rich lakes, presumably due to high in-situ production. We found robust correlations between the relative abundance of the ubiquitous humic-like components and that of the Peak N component in the bulk DOM irrespective of water types or ice-free areas. We proposed there were common processes that generated the ubiquitous humic-like components from the Peak N component in the Lützow-Holm Bay and Amundsen Bay lakes and streams, such as bacterial processing of primary production-derived DOM and photochemical transformation of microbial DOM.
本研究对来自东南极勒托霍尔姆湾和阿蒙森湾无冰区的 47 个湖泊和 2 条溪流中的溶解有机物（DOM）进行了特征描述（n=74），这些地区历史上很少进行生物地球化学研究。对样品进行了基本水质分析以及树脂分级、紫外可见光谱、激发发射矩阵光谱结合平行因子分析（EEM-PARAFAC）分析。由于蒸发浓缩，样品的盐度范围非常广泛，从淡水到高盐度。DOM 的光谱斜率（S）与盐度呈明显正相关，这是光降解的一个指标。因此，我们将这种相关性解释为由于水滞留时间延长而导致的光降解过程。在所鉴定的七个 PARAFAC 组分中，三个普遍存在的类腐殖质组分随着光降解的进行而减少，而一个光稳定的 UVC 类腐殖质组分则增加了其相对丰度。一个非类腐殖质组分，传统上定义为峰 N，没有表现出依赖于光降解的趋势，而且在富营养化湖泊中其含量较高，可能是由于原位产量较高。我们发现，无论水类型或无冰区如何，普遍存在的类腐殖质组分的相对丰度与 DOM 中峰 N 组分的相对丰度之间存在很强的相关性。我们提出，在勒托霍尔姆湾和阿蒙森湾的湖泊和溪流中，存在从峰 N 组分生成普遍存在的类腐殖质组分的共同过程，例如细菌对初级生产衍生 DOM 的处理和微生物 DOM 的光化学转化。
