Combining colour parameters and geochemical tracers to improve sediment source discrimination in a mining catchment (New Caledonia, South Pacific Islands)

<p>Tracing the origin of sediment is needed to improve our knowledge of hydro-sedimentary dynamics at the catchment scale. Several fingerprinting approaches have been developed to provide this crucial information. In particular, spectroscopy provides a rapid, inexpensive and non-destructive al...

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Autores principales:	V. Sellier, O. Navratil, J. P. Laceby, C. Legout, A. Foucher, M. Allenbach, I. Lefèvre, O. Evrard
Formato:	article
Lenguaje:	EN
Publicado:	Copernicus Publications 2021
Materias:	Environmental sciences GE1-350 Geology QE1-996.5
Acceso en línea:	https://doaj.org/article/f7b1e7ca4be64cdba815bb4ae24c797c
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id	oai:doaj.org-article:f7b1e7ca4be64cdba815bb4ae24c797c
record_format	dspace
institution	DOAJ
collection	DOAJ
language	EN
topic	Environmental sciences GE1-350 Geology QE1-996.5
spellingShingle	Environmental sciences GE1-350 Geology QE1-996.5 V. Sellier O. Navratil J. P. Laceby C. Legout A. Foucher M. Allenbach I. Lefèvre O. Evrard Combining colour parameters and geochemical tracers to improve sediment source discrimination in a mining catchment (New Caledonia, South Pacific Islands)
description	<p>Tracing the origin of sediment is needed to improve our knowledge of hydro-sedimentary dynamics at the catchment scale. Several fingerprinting approaches have been developed to provide this crucial information. In particular, spectroscopy provides a rapid, inexpensive and non-destructive alternative technique to the conventional analysis of the geochemical properties. Here, we investigated the performance of four multi-proxy approaches based on (1) colour parameters, (2) geochemical properties, (3) colour parameters coupled with geochemical properties and (4) the entire visible spectrum to discriminate sediment source contributions in a mining catchment of New Caledonia. This French archipelago located in the south-west Pacific Ocean is the world's sixth largest producer of nickel. Open-cast nickel mining increases soil degradation and the downstream transfer of sediments in river systems, leading to the river system siltation. The sediment sources considered in the current research were therefore sediment eroded from mining sub-catchments and non-mining sub-catchments. To this end, sediment deposited during two cyclonic events (i.e. 2015 and 2017) was collected following a tributary design approach in one of the first areas exploited for nickel mining on the archipelago, the Thio River catchment (397 km<span class="inline-formula"><sup>2</sup></span>). Source (<span class="inline-formula"><i>n</i>=24</span>) and river sediment (<span class="inline-formula"><i>n</i>=19</span>) samples were analysed by X-ray fluorescence and spectroscopy in the visible spectra (i.e. 365–735 nm). The results demonstrated that the individual sediment tracing methods based on spectroscopy measurements (i.e. (1) and (4)) were not able to discriminate sources. In contrast, the geochemical approach (2) did discriminate sources, with 83.1 % of variance in sources explained. However, it is the inclusion of colour properties in addition to geochemical parameters (3) which provides the strongest discrimination between sources, with 92.6 % of source variance explained. For each of these approaches ((2) and (3)), the associated fingerprinting properties were used in an optimized mixing model. The predictive performance of the models was validated through tests with artificial mixture samples, i.e. where the proportions of the sources were known beforehand. Although with a slightly lower discrimination potential, the “geochemistry” model (2) provided similar predictions of sediment contributions to those obtained with the coupled “colour <span class="inline-formula">+</span> geochemistry” model (3). Indeed, the geochemistry model (2) showed that mining tributary contributions dominated the sediments inputs, with a mean contribution of 68 <span class="inline-formula">±</span> 25 % for the 2015 flood event, whereas the colour <span class="inline-formula">+</span> geochemistry model (3) estimated that the mining tributaries contributed 65 <span class="inline-formula">±</span> 27 %. In a similar way, the contributions of mining tributaries were evaluated to 83 <span class="inline-formula">±</span> 8 % by the geochemistry model (2) versus 88 <span class="inline-formula">±</span> 8 % by the colour <span class="inline-formula">+</span> geochemistry model (3) for the 2017 flood event. Therefore, the use of these<span id="page744"/> approaches based on geochemical properties only (2) or of those coupled to colour parameters (3) was shown to improve source discrimination and to reduce uncertainties associated with sediment source apportionment. These techniques could be extended to other mining catchments of New Caledonia but also to other similar nickel mining areas around the world.</p>
format	article
author	V. Sellier O. Navratil J. P. Laceby C. Legout A. Foucher M. Allenbach I. Lefèvre O. Evrard
author_facet	V. Sellier O. Navratil J. P. Laceby C. Legout A. Foucher M. Allenbach I. Lefèvre O. Evrard
author_sort	V. Sellier
title	Combining colour parameters and geochemical tracers to improve sediment source discrimination in a mining catchment (New Caledonia, South Pacific Islands)
title_short	Combining colour parameters and geochemical tracers to improve sediment source discrimination in a mining catchment (New Caledonia, South Pacific Islands)
title_full	Combining colour parameters and geochemical tracers to improve sediment source discrimination in a mining catchment (New Caledonia, South Pacific Islands)
title_fullStr	Combining colour parameters and geochemical tracers to improve sediment source discrimination in a mining catchment (New Caledonia, South Pacific Islands)
title_full_unstemmed	Combining colour parameters and geochemical tracers to improve sediment source discrimination in a mining catchment (New Caledonia, South Pacific Islands)
title_sort	combining colour parameters and geochemical tracers to improve sediment source discrimination in a mining catchment (new caledonia, south pacific islands)
publisher	Copernicus Publications
publishDate	2021
url	https://doaj.org/article/f7b1e7ca4be64cdba815bb4ae24c797c
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spelling	oai:doaj.org-article:f7b1e7ca4be64cdba815bb4ae24c797c2021-11-22T08:20:14ZCombining colour parameters and geochemical tracers to improve sediment source discrimination in a mining catchment (New Caledonia, South Pacific Islands)10.5194/soil-7-743-20212199-39712199-398Xhttps://doaj.org/article/f7b1e7ca4be64cdba815bb4ae24c797c2021-11-01T00:00:00Zhttps://soil.copernicus.org/articles/7/743/2021/soil-7-743-2021.pdfhttps://doaj.org/toc/2199-3971https://doaj.org/toc/2199-398X<p>Tracing the origin of sediment is needed to improve our knowledge of hydro-sedimentary dynamics at the catchment scale. Several fingerprinting approaches have been developed to provide this crucial information. In particular, spectroscopy provides a rapid, inexpensive and non-destructive alternative technique to the conventional analysis of the geochemical properties. Here, we investigated the performance of four multi-proxy approaches based on (1) colour parameters, (2) geochemical properties, (3) colour parameters coupled with geochemical properties and (4) the entire visible spectrum to discriminate sediment source contributions in a mining catchment of New Caledonia. This French archipelago located in the south-west Pacific Ocean is the world's sixth largest producer of nickel. Open-cast nickel mining increases soil degradation and the downstream transfer of sediments in river systems, leading to the river system siltation. The sediment sources considered in the current research were therefore sediment eroded from mining sub-catchments and non-mining sub-catchments. To this end, sediment deposited during two cyclonic events (i.e. 2015 and 2017) was collected following a tributary design approach in one of the first areas exploited for nickel mining on the archipelago, the Thio River catchment (397 km<span class="inline-formula"><sup>2</sup></span>). Source (<span class="inline-formula"><i>n</i>=24</span>) and river sediment (<span class="inline-formula"><i>n</i>=19</span>) samples were analysed by X-ray fluorescence and spectroscopy in the visible spectra (i.e. 365–735 nm). The results demonstrated that the individual sediment tracing methods based on spectroscopy measurements (i.e. (1) and (4)) were not able to discriminate sources. In contrast, the geochemical approach (2) did discriminate sources, with 83.1 % of variance in sources explained. However, it is the inclusion of colour properties in addition to geochemical parameters (3) which provides the strongest discrimination between sources, with 92.6 % of source variance explained. For each of these approaches ((2) and (3)), the associated fingerprinting properties were used in an optimized mixing model. The predictive performance of the models was validated through tests with artificial mixture samples, i.e. where the proportions of the sources were known beforehand. Although with a slightly lower discrimination potential, the “geochemistry” model (2) provided similar predictions of sediment contributions to those obtained with the coupled “colour <span class="inline-formula">+</span> geochemistry” model (3). Indeed, the geochemistry model (2) showed that mining tributary contributions dominated the sediments inputs, with a mean contribution of 68 <span class="inline-formula">±</span> 25 % for the 2015 flood event, whereas the colour <span class="inline-formula">+</span> geochemistry model (3) estimated that the mining tributaries contributed 65 <span class="inline-formula">±</span> 27 %. In a similar way, the contributions of mining tributaries were evaluated to 83 <span class="inline-formula">±</span> 8 % by the geochemistry model (2) versus 88 <span class="inline-formula">±</span> 8 % by the colour <span class="inline-formula">+</span> geochemistry model (3) for the 2017 flood event. Therefore, the use of these<span id="page744"/> approaches based on geochemical properties only (2) or of those coupled to colour parameters (3) was shown to improve source discrimination and to reduce uncertainties associated with sediment source apportionment. These techniques could be extended to other mining catchments of New Caledonia but also to other similar nickel mining areas around the world.</p>V. SellierO. NavratilJ. P. LacebyC. LegoutA. FoucherM. AllenbachI. LefèvreO. EvrardCopernicus PublicationsarticleEnvironmental sciencesGE1-350GeologyQE1-996.5ENSOIL, Vol 7, Pp 743-766 (2021)

Combining colour parameters and geochemical tracers to improve sediment source discrimination in a mining catchment (New Caledonia, South Pacific Islands)

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