Nutrient inputs to estuaries from nine scottish east coast rivers; influence of estuarine processes on inputs to the North Sea
Nutrient inputs to estuaries from nine scottish east coast rivers; influence of estuarine processes on inputs to the North Sea
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苏格兰东海岸九条河流对河口的养分输入；
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发表时间：
1994
期刊：
影响因子：
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通讯作者：
P. Balls
中科院分区：
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作者：
P. Balls
摘要 已测定了北海九个河口表层水中的营养盐分布（硝酸盐、氨、磷酸盐和硅酸盐）：特威德河口、福斯河口、泰伊河口、迪伊河口、顿河河口、伊森河口、比尤利/因弗内斯河口、克罗马蒂河口和多诺赫河口。通过1991年4月、7月和9月以及1992年2月进行的调查，对季节变化进行了检查。每次，所有九个河口的调查通常在大潮高水位前后在3-5天内完成。这种密集且严格控制的采样制度确保了各个河口营养物浓度之间的真实比较。个别河流和河口的养分浓度被证明与土地利用有关。农业集约化和淡水输入量低的河流流域，例如顿河和伊桑河，其河口的硝酸盐（高达 600 μM）和磷酸盐（高达 5 μM）浓度较高。相比之下，高地河流流域（因弗内斯、克罗马蒂和多诺赫峡湾）土壤矿物质贫乏、人口稀少和农业强度低，通常会导致河水中的养分浓度低于沿海海水。溶解营养物的保守混合被证明是河口冲刷时间的函数，它控制内部过程（生物和非生物）可以改变营养物输入的程度。在特威德河、顿河和伊桑河等短暂且快速冲刷的河口，营养物质的表现往往比较保守。相比之下，在估计从福斯湾、泰伊湾和多诺赫湾等大型缓慢冲刷河口流向沿海地区的河流养分通量时，内部过程显得很重要。对于这些系统，对河口河流输入的估计并不能很好地估计进入沿海地区的负荷。这主要是由于营养元素在溶解相和颗粒（包括沉积物）相之间的循环。从区域来看，养分投入总量主要由淡水流量模式决定，而不是由个别河流的高浓度决定。因此，泰河在数量上是苏格兰北海沿岸水域最重要的营养河流来源。对于大多数河口而言，高盐度下的氮磷比接近于沿海水域观察到的值。然而，对于唐河和伊桑河（以及较小程度上的特威德河），该比率较高，可能反映了农业氮投入的影响；讨论了对沿海水域浮游植物生长的可能影响。在北部河口（比尤利/因弗内斯、克罗马蒂和多诺赫峡湾），低盐度下存在明显的硅酸盐来源，这是由于硅酸盐从河口沉积物解吸到营养贫乏的河水中。
Abstract Nutrient distributions (nitrate, ammonia, phosphate and silicate) have been determined in the surface waters of nine North Sea estuaries: Tweed, Forth, Tay, Dee, Don, Ythan, Beauly/Inverness Firth, Cromarty Firth and Dornoch Firth. Seasonal variability has been examined by conducting surveys in April, July and September 1991 and February 1992. On each occasion, surveys of all nine estuaries were normally completed in 3-5 days of each other, around high water on spring tides. This intensive and strictly controlled sampling regime ensures a realistic comparison between nutrient concentrations in individual estuaries. Nutrient concentrations in individual rivers and estuaries are demonstrated to be related to land use. River catchments with intensive agriculture and low freshwater input, such as the Don and Ythan, have enhanced nitrate (up to 600 μM) and phosphate (up to 5 μM) concentrations in their estuaries. By contrast, Highland river catchments with mineral-poor soils, low populations and low agricultural intensity (Inverness, Cromarty and Dornoch Firths) generally lead to nutrient concentrations being lower in river water than in coastal seawater. Conservative mixing of dissolved nutrients is demonstrated to be a function of estuarine flushing time which controls the extent to which internal processes (biological and abiological) can modify nutrient inputs. Nutrients tend to behave conservatively in short rapidly flushed estuaries such as the Tweed, Don and Ythan. In contrast, internal processes are shown to be important when estimating riverine nutrient fluxes to the coastal zone from large slowly flushed estuaries such as the Forth, Tay and Dornoch Firth. For these systems, estimates of riverine inputs to the estuary do not provide a good estimate of the load entering the coastal zone. This is primarily due to the cycling of nutrient elements between dissolved and particulate (including sediment) phases. On a regional basis, gross nutrient inputs are dominated by the pattern of freshwater flow rather than by high concentrations in individual rivers. In consequence the Tay is quantitatively the most important riverine source of nutrients to Scottish North Sea coastal waters. For most of the estuaries examined the N:P ratio at high salinity is close to that observed in coastal waters. For the Don and Ythan, however, (and to a lesser extent the Tweed) the ratio is higher, probably reflecting the influence of agricultural nitrogen inputs; possible implications to phytoplankton growth in coastal waters are discussed. In the northern estuaries (Beauly/Inverness, Cromarty and Dornoch Firths), a source of silicate is evident at low salinity, this is attributed to desorption of silicate from estuarine sediments to nutrient-poor river water.