Spatial and seasonal variation of trace elements contamination level of the waters from the hydrosystem Lake Togo-Lagoon
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Spatial and seasonal variation of trace elements contamination level of the waters from the hydrosystem Lake Togo‑Lagoon of Aného (South of Togo) Kamilou Ouro‑Sama1,2 · Hodabalo Dheoulaba Solitoke1 · Gnon Tanouayi1 · Iuliana Mihaela Lazar2 · Petronela Bran2 · Marius Nadejde2 · Housséni Ahoudi1 · Tchaa Esso‑Essinam Badassan1 · Akouètê Yawovi Nyametso1 · Kissao Gnandi1 · Gabriel Octavian Lazar2 Received: 18 November 2019 / Accepted: 24 March 2020 © Springer Nature Switzerland AG 2020
Abstract The hydrosystem Lac Togo-Lagoon of Aného is located in a watershed where phosphate mining of trace element-rich phosphorites takes place. This activity generates various types of wastes that are dumped into the environment without prior treatment. In addition, there are contributions of its tributaries after leaching of agricultural and urban soils. All this contributes to the degradation of the water quality of this ecosystem. The aim of this study is to assess the level of trace elements contamination of the waters from the hydrosystem Lake Togo-Lagoon of Aného and its spatio-seasonal variations. In the dry and rainy season, the physicochemical parameters of waters were measured according to French standards (AFNOR). The trace elements were determined by atomic absorption spectrometer coupled to a hydride and cold vapour generator. The spatial distribution was evaluated using maps which were performed by ordinary kriging interpolation method of ArcGIS 10.2.2 software. The results showed that the average dry season concentrations were significantly higher (p Cu > Ni > C d > Mn > Zn > As > Hg, in the dry season and Cr > Ni > Pb > Cu > Zn > Cd > Mn > As > Hg, in the rainy season. It is found that during both seasons Hg and As are the most weakly represented elements. 6.2.2 Comparison of trace element concentrations with water quality standards During the dry season, 100% of Cd and Pb levels were above the WHO standards, against 96.67% and 93.33%, respectively, in the rainy season (Fig. 6a, b). The pollution factors (PF) of Cd and Pb reached, respectively, 30.77 times Vol.:(0123456789)
Research Article
SN Applied Sciences
(2020) 2:811
| https://doi.org/10.1007/s42452-020-2593-7
Fig. 5 Maps of the spatial distribution of As, Zn and Mn concentrations in the dry season (a–c) and rainy season (d–f)
and 34.84 times the WHO standards during the dry season at the site S30 in lagoon of Aného. On the other hand, these PF reached 20.49 times the standard for Cd and 12.42 times the standard for Pb, respectively, in the sites S1 and S5 of Lake Togo, in the rainy season. The Cr contents recorded in the dry season were 96.67% higher than the WHO standard against 90% in the rainy season (Fig. 6c), with the respective highest PF of 7.94 times the standard in the lagoon of Aného and 2.48 times the standard in the Lake Togo. In the dry season, 63.33% of Ni contents are above the WHO standard with PF reaching 2.65 times the standard against 40% in the rainy season with the highest PF of 2.58 times the standard (Fig. 6d). Table 1 shows
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