Assessing soil contamination by hazardous metals and estimating the extent to which metal concentrations in surficial sediments may pose risks to human health are increasingly important environmental issues. An integrated sedimentological and geochemical study of 57 Holocene beach sands from the shallow subsurface (120-130 cm depth) of the heavily urbanized Tyrrhenian Sea coast of Italy (Tuscany and adjacent coastal stretches) allowed a remarkable compositional heterogeneity to be identified as a function of spatial variations in riverine sediment supply and alongshore sediment dispersal patterns. Concentrations of Cr, Ni, and As exceeding maximum permissible limits for recreational/industrial sites (150 mg/kg, 120 mg/kg, and 20 mg/kg, respectively) reveal spatial trends that fit the petrography of modern beach sands and closely reflect the geology of river catchments, thus indicating a geogenic origin. Extremely high concentrations of Cr (and Ni), even 10 times greater than threshold values, are interpreted to reflect sediment supply from river catchments rich in ultramafic rocks (ophiolite sequences of Cecina and Campiglia areas), with subsequent transport via the longshore drift. On the other hand, high As concentrations in the Campiglia region and along the southern stretch of coast reflect leaching of felsic volcanic and plutonic parent rocks and hydrothermal products related to the Tuscan and Roman magmatic provinces cropping out in the Fiora, Albegna, and Cornia river catchments. This study shows that coastal sediment derived from particular source rocks is likely to contain potentially harmful metals in predictable proportions, which may easily exceed maximum allowable concentrations. Assessing spatial distribution of such metals based on catchment geology and sediment transport pathways may help separate natural concentrations from the anthropogenic contribution, providing a valuable source of information for appropriate remediation strategies and management options.

中文翻译：

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潜在危险元素的地球化学异常反映了集水区地质：来自意大利第勒尼安海岸的一个例子。

评估有害金属对土壤的污染并估计表层沉积物中金属的浓度可能对人类健康构成威胁的程度已成为越来越重要的环境问题。对意大利重度城市化的第勒尼安海沿岸的浅表层（深度120-130 cm）（托斯卡纳及邻近海岸带）的57个全新世海滩砂进行了沉积学和地球化学的综合研究，从而确定了显着的组成异质性。河流沉积物供应和沿岸沉积物扩散模式的空间变化。Cr，Ni和As的浓度超过了娱乐场所/工业场所的最大允许限值（150 mg / kg，120 mg / kg和20 mg / kg，分别揭示了适合现代海滩沙滩岩相的空间趋势，并密切反映了河流集水区的地质情况，从而表明了成因。铬（和镍）的极高浓度，甚至比阈值高10倍，被解释为反映了来自富镁铁质岩石（切奇纳和坎皮利亚地区的蛇绿岩层序）的河流集水区的沉积物供应，随后通过长岸漂流进行了运输。另一方面，在坎皮利亚地区和沿海岸南部延伸的高砷浓度反映了与菲奥拉，阿尔贝尼亚和科尼亚河中的托斯卡纳和罗马岩浆省有关的长石质火山岩和深成岩母岩和热液产物的浸出。流域。这项研究表明，源自特定烃源岩的沿海沉积物可能含有可预测比例的潜在有害金属，其含量很容易超过最大允许浓度。根据集水区地质和沉积物运输途径评估此类金属的空间分布，可能有助于将自然浓度与人为贡献区分开，从而为适当的补救策略和管理方案提供了有价值的信息来源。