Spatial and seasonal variation of trace elements contamination level of the waters from the hydrosystem Lake Togo-Lagoon of Aného (South of Togo)

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 < 0.0001) than those of the rainy season except that of Zn. The average concentrations (in μg/l) observed for Cd: (39.28; 24.63), Pb: (216.82; 66.44), Cr: (197.00; 69.05) and Ni: (100.06; 66.50), respectively, in dry and rainy season were significantly higher than the WHO standards. However, overall trace elements contamination has been noted with polymetallic contamination indices which reached 4.14 in the dry season and 2.41 in the rainy season. This contamination is mainly of anthropogenic origin and comes from the intrusion of seawater loaded with phosphate effluents in the dry season and the leaching of mining and agricultural soils in the rainy season. The results proved that this lagoon ecosystem is polluted by trace elements mainly caused by phosphate mining. Thus, it deserves special attention for its better management for a sustainable development.

Spatio-temporal monitoring of potentially toxic elements in Lagos harbour water and its health risk implications

“…These results were also in agreement with the range of temperature recorded by Oyeleke and his coworkers (27-30 °C) that worked on Lagos lagoon. However, the measured temperature was slightly higher than what was recorded by Adedayo and his co-researchers that worked on Lagos lagoon [52], but lower than the temperature recorded on Bonny island water in River State, Nigeria (32.2 °C ± 0.03) [16].…”

Trace Element Concentrations in Soft Tissue and Shell of the Mangrove Oyster (&lt;i&gt;Crassostrea Gasar&lt;/i&gt; Dautzenberg, 1891) from the Lake Zowla-An&#233;ho Lagoon Hydro System (Southern Togo)

“…Anthropogenic activities have been known to be the primary causes of trace metal contamination in waters. Recently, Ouro-Sama et al [20] assess the levels of trace element contaminations of the waters from the western part of the hydrosystem (Lake Togo-Lagoon of Aného) and its spatio-seasonal variations. Their results proved that this aquatic ecosystem is contaminated by Cd, Pb, Cr and Ni with average concentrations that are significantly above WHO standards.…”

Trace Elements in Mollusks, Crustaceans and Fish Commonly Consumed by the Catfish &lt;i&gt;Chrysichthys nigrodigitatus&lt;/i&gt; Lac&#233;p&#232;de, 1803 from the Lake Togo-Lagoon of An&#233;ho Hydrosystem (Southern Togo)

“…These BCF are expressed according to the following equation [3] [10] [33] [34]. Trace element concentrations in waters and sediments (Table 1) used for the calculations were from simultaneous studies in the same hydrosystem [4] [5].…”