Purpose

This study aims to evaluate temporal trends of Tantalum (Ta) and Niobium (Nb) concentrations in northern Baltic Sea sediments with focus on the potential impact from the Rönnskär sulfide ore smelter, located 15 km east of Skellefteå in northern Sweden. The potential of Ta or Nb to serve as tracers for environmental pollution caused by the electronic waste is compared. Lastly, correlations between Ta and Nb concentrations and those of major redox elements are investigated.

Methods

A 35-cm-deep core was collected in the harbor bay (Kallholmsfjärden) outside of the smelter. A secondary 6-m-deep sediment core was collected in the deep Bothnian Bay for comparative purposes. Element screening analysis was conducted the using ICP-SFMS for the Kallhomsfjärden core and a combination of ICP-SFMS and ICP-OES for the Bothnian Bay core. In the final analysis, a 5-step sequential extraction technique was preformed to allow for better prediction of the fate and mobility of Ta and Nb.

Results and discussion

In the vicinity of the smelter, Ta concentration increases from 0.42 to 3.8 ppm from the time coinciding with the beginning of electronic waste processing. Conversely, Nb concentration remained stable at background levels throughout the core at 6.33 ± 0.78 ppm. The Nb/Ta ratio thus changed from 14.5 to 1.7, reflecting an increase of anthropogenic input of Ta into the bay sediments. In the pre-industrial part of the sediment, concentrations of both elements follow concentration of aluminosilicates in the core. In recent sediments, however, the anthropogenic Ta exhibits an association with hydrous ferric oxides (HFOs) and organic matter.

Conclusions

Notable increases in Ta concentrations began following the beginning of scrap metal and electronic waste processing at the Rönnskär smelter. Anthropogenic Ta introduced in the upper portion of the sediment and are more associated with HFOs and organic material than natural Ta seen in the deeper parts of the core where detrital Ta is most common. Niobium was not affected by the Rönnskär smelter and displayed no notable change to the preindustrial background.

中文翻译：

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追踪瑞典博尼安湾沉积物中钽和铌的人为来源

目的

这项研究旨在评估波罗的海北部沉积物中钽（Ta）和铌（Nb）浓度的时间趋势，重点是位于瑞典北部Skellefteå以东15公里的Rönnskär硫化矿石冶炼厂的潜在影响。比较了Ta或Nb用作电子废物造成的环境污染示踪剂的潜力。最后，研究了Ta和Nb浓度与主要氧化还原元素之间的相关性。

方法

在冶炼厂外的港湾（Kallholmsfjärden）中收集了一个35厘米深的岩心。为了进行比较，在深的博特尼亚湾中收集了一个深达6米的次要沉积物岩心。使用ICP-SFMS（用于Kallhomsfjärden岩心）和ICP-SFMS和ICP-OES的组合（用于Bothnian Bay岩心）进行元素筛选分析。在最终分析中，执行了5步顺序提取技术，以便更好地预测Ta和Nb的命运和迁移率。

结果和讨论

在冶炼厂附近，从开始电子废物处理开始，Ta的浓度从0.42 ppm增加到3.8 ppm。相反，整个核心的Nb浓度在背景水平保持稳定，为6.33±0.78 ppm。因此，Nb / Ta比率从14.5变为1.7，反映了人为因素向海湾沉积物中输入的Ta有所增加。在沉积物的工业化前部分，两种元素的浓度均随核心中硅铝酸盐的浓度而变化。然而，在最近的沉积物中，人为的Ta表现出与含水三氧化二铁（HFOs）和有机物的联系。

结论

在Rönnskär冶炼厂开始进行废金属和电子废物处理之后，Ta浓度开始显着增加。在沉积物上部最常见的人为深部，人为的Ta引入沉积物的上部，与HFO和有机物质的关系要比天然Ta的多。铌不受Rönnskär冶炼厂的影响，并且对工业化前的背景无明显变化。