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首页> 外文期刊>Estuarine Coastal and Shelf Science >The oxygen isotopic composition of phosphate in Elkhorn Slough, California: A tracer for phosphate sources
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The oxygen isotopic composition of phosphate in Elkhorn Slough, California: A tracer for phosphate sources

机译：加利福尼亚州埃尔克霍恩斯劳（Elkhorn Slough）磷酸盐的氧同位素组成：磷酸盐来源的示踪剂

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Elkhorn Slough, a small seasonal estuary in central California, has been subjected to increased nutrient loading from agricultural and other non-point sources. However, because nutrients do not behave conservatively, tracing nutrient sources and cycling in ecosystems like Elkhorn Slough has been difficult to assess. This is particularly true of phosphorus (P), which has only one stable isotope and cannot be used as an isotopic tracer. However, isotopic fractionation of oxygen in phosphate at surface water temperatures only occurs as a result of enzyme-mediated, biochemical reactions. Thus, if phosphate demand is low relative to input and is not heavily cycled within the ecosystem, the δ~(18)O of phosphate will reflect the isotopic composition of phosphate sources to the system. We utilized the δ~(18)O of dissolved inorganic phosphate (DIP) within the main channel of the slough and nearby Moss Landing Harbor and the δ~(18)O of reactive phosphate from sediment and soil samples collected within the watershed to understand phosphate sources and cycling within Elkhorn Slough. Trends in the δ~(18)O of DIP were seasonally consistent with high values near the mouth reflecting oceanic phosphate (19.1 per thousand - 20.3 per thousand), dropping to a minimum value near Hummingbird Island in the central slough (point source, 14.1 per thousand - 14.4 per thousand), and increasing again near the head of the slough, reflecting fertilizer input (18.9 per thousand - 19.3 per thousand). Reactive phosphate δ~(18)O values extracted from sediments and soils in the watershed range from 10.6 per thousand in a drainage ditch to 22.3 per thousand in creek sediments near agriculture fields. The wide range in phosphate δ~(18)O values reflects the variations in land use and application of different fertilizers in this agriculturally dominated landscape. These data suggest that phosphate δ~(18)O can be an effective tool for identifying P sources and understanding phosphate dynamics in estuarine ecosystems.
机译：Elkhorn Slough是加利福尼亚州中部的一个小型季节性河口，其农业和其他非重点源地的营养负荷增加。但是，由于养分的行为并不保守，因此难以评估养分来源和诸如Elkhorn Slough之类的生态系统中的循环。磷（P）尤其如此，磷只有一个稳定的同位素，不能用作同位素示踪剂。然而，在地表水温度下，磷酸盐中氧的同位素分馏仅是由于酶介导的生化反应而发生的。因此，如果磷酸盐需求相对于投入而言较低，并且在生态系统内没有大量循环，则磷酸盐的δ〜（18）O将向系统反映磷酸盐源的同位素组成。我们利用泥沼和附近的莫斯登陆港主要通道内的溶解性无机磷酸盐（DIP）的δ〜（18）O和流域内收集的沉积物和土壤样品中的活性磷酸盐的δ〜（18）O磷酸盐源和Elkhorn泥沼中的循环。 DIP的δ〜（18）O趋势与季节性变化相吻合，反映出海口磷酸盐的高值（19.1 /千-20.3 /千），在中央泥沼的蜂鸟岛附近降至最小值（点源14.1）每千分之一-14.4每千分之一），并在泥沼顶部附近再次增加，反映出肥料的投入（每千分之一18.9-每千分之一19.3）。从流域沉积物和土壤中提取的反应性磷酸盐δ〜（18）O值范围从排水沟的每千分之10.6到农田附近小河沉积物中的每千分之22.3。磷酸盐δ〜（18）O值的变化幅度很大，反映了该农业主导景观中土地利用和不同肥料的施用变化。这些数据表明，磷酸盐δ〜（18）O可以作为一种有效的工具来识别磷源并了解河口生态系统中的磷酸盐动力学。

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