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首页> 外文期刊>Estuarine Coastal and Shelf Science >Sources and dispersal of land-based runoff from small Hawaiian drainages to a coral reef: Insights from geochemical signatures
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Sources and dispersal of land-based runoff from small Hawaiian drainages to a coral reef: Insights from geochemical signatures

机译：从夏威夷小型排水沟到珊瑚礁的陆上径流的来源和扩散：地球化学特征的见解

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摘要

Land-based sediment and contaminant runoff is a major threat to coral reefs, and runoff reduction efforts would benefit from knowledge of specific runoff sources. Geochemical signatures of small drainage basins were determined in the fine fraction of soil and sediment, then used in the nearshore region of a coral reef-fringed urban embayment on southeast Oahu, Hawaii, to describe sources and dispersal of land-based runoff. The sedimentary rare earth element ratio (La/Yb)(N) showed a clear distinction between the two main rock types in the overall contributing area, tholeiitic and alkalic olivine basalt. Based on this geochemical signature it was apparent that the majority of terrigenous sediment on the reef flat originated from geologically old tholeiitic drainages. Sediment from one of five tholeiitic drainages had a distinct geochemical signature, and sediment with this signature was dispersed on the reef flat 2 km west and 150 m offshore of the contributing basin. Sediment and the anthropogenic metals Cd, Pb, and Zn were entrained in runoff from the most heavily urbanized region of the watershed. Although anthropogenic Cd and Zn had localized distributions close to shore, anthropogenic Pb was found associated with fine sediment on the westernmost part of the reef flat and 400 m offshore, illustrating how trade-wind-driven sediment transport can increase the scale of runoff impacts to nearshore communities. Our findings show that sediment geochemical signatures can provide insights about the source and dispersal of land-based runoff in shallow coastal environments. The application of such knowledge to watershed management and habitat remediation efforts can aid in the protection and restoration of runoff-impacted coastal ecosystems worldwide. (C) Published by Elsevier Ltd.
机译：陆上沉积物和污染物径流是对珊瑚礁的主要威胁，径流减少工作将受益于特定径流来源的知识。在土壤和沉积物的细小部分确定了小流域的地球化学特征，然后在夏威夷东南部瓦胡岛东南部的一片珊瑚礁镶边的城市堤岸的近岸区域中，用来描述陆源径流的来源和扩散。沉积稀土元素比率（La / Yb）（N）在总体贡献区中的两种主要岩石类型中，即硬质玄武岩和碱性橄榄石玄武岩之间有明显的区别。根据这一地球化学特征，很明显，礁滩上的大部分陆源性沉积物都来自具有地质学意义的老套渠。来自五个高渗流域之一的沉积物具有独特的地球化学特征，具有该特征的沉积物分散在礁石滩西2公里和集水盆地近海150 m处。沉积物和人为金属Cd，Pb和Zn被带入了流域中城市化程度最高的地区的径流中。尽管人为的Cd和Zn在海岸附近有局部分布，但人为的Pb被发现与礁滩最西端和近海400 m处的细沉积物有关，这说明了贸易风驱动的沉积物运输如何增加径流影响的范围。近岸社区。我们的发现表明，沉积物地球化学特征可以提供有关浅海沿海环境中陆基径流的来源和扩散的见解。将此类知识应用于流域管理和生境修复工作，可以帮助保护和恢复全球径流受影响的沿海生态系统。 （C）由爱思唯尔有限公司出版。

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