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Spatial Availability of Nitrogen and Pesticides in the Surface Layers of Agricultural Soils of Tropical Hydrosystems in the Wet Season: Case of the BéréWatershed in Côte d’Ivoire (West Africa)
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作者 Mian Germain Eba Kouakou Sylvain Akpo +2 位作者 Pétémanangnan Jean-Marie Ouattara Tiangoua Koné Lacina Coulibaly 《Journal of Agricultural Chemistry and Environment》 2021年第2期143-168,共26页
The objective of this study was to assess the contribution of the spatial organization of cropping systems and the physicochemical properties of surface layers of the agricultural zones soils in tropical hydrosystems ... The objective of this study was to assess the contribution of the spatial organization of cropping systems and the physicochemical properties of surface layers of the agricultural zones soils in tropical hydrosystems to the spatial availability of nitrogen and pesticides during the wet season, such as the Béré watershed (BW) in C<span style="white-space:nowrap;">?</span>te d’Ivoire. For this purpose, after mapping the spatial distribution of the BW cropping systems based on the likelihood classification methodology of satellite images of the study area, 27 samples from the 0 - 20 cm horizon of the soil surface layers of the agricultural areas were taken during the wet and agricultural season of the year 2016. The Kjeldahl method has been used to evaluate the total nitrogen concentration and high-performance liquid chromatography (HPLC) chain made it possible for the analysis of pesticide residues in the soil solutions. Geostatistical analysis and processing of spatial data and physicochemical and agrochemical soil parameters revealed that two major agricultural areas stand out in the BW, namely the Béré upstream watershed (BUW) dominated at 32.65% by annual croppings (maize, cotton, rainfed or lowland rice, market gardening, etc.) and the Béré downstream watershed (BDW) by large areas of perennial croppings (cashew nuts, cocoa, etc.), <em>i.e.</em> 21.47%. Agricultural soils in BW are usually of the moderately desaturated ferralitic type with a low acid pH and a quite strong temperature, such as those of tropical soils’ characteristics. However, agricultural soils in the BUW are characterized by higher proportions of sand and coarse sand. The parameters such as total porosity, cation exchange capacity, clay, organic matter, silt, fine silt, coarse silt, and potassium ions, are higher in the soils of the agricultural area of the BDW. Moreover, soils in the agricultural areas of the BUW are less rich in total nitrogen (0.84 g<span style="white-space:nowrap;">·</span>kg<sup>-1</sup>) in contrast to those of the BDW (1.2 g<span style="white-space:nowrap;">·</span>kg<sup>-1</sup>). On the other hand, the median concentrations of total pesticides remain very high in the BUW (193.80 μg<span style="white-space:nowrap;">·</span>kg<sup>-1</sup>) in front of those of the BDW (94.81 μg<span style="white-space:nowrap;">·</span>kg<sup>-1</sup>). In addition, the biological family of herbicides was the most notable in BW. The chemical families of triazines (100% detection;79.37 μg<span style="white-space:nowrap;">·</span>kg<sup>-1</sup>) are the most important in the agricultural area of the BUW with the very significant presence of active molecules of pesticides such as simazine (92.86% detection;13.17 μg<span style="white-space:nowrap;">·</span>kg<sup>-1</sup>). However, in the BDW, urea substitute (100% detection;44.02 μg<span style="white-space:nowrap;">·</span>kg<sup>-1</sup>) dominate, including the active substance chlortoluron (84.62% detection;10.12 μg<span style="white-space:nowrap;">·</span>kg<sup>-1</sup>). The presence and abundance of nitrogen and pesticides in the soils of the agricultural areas of BW are strongly linked to the intensive use of these agrochemicals in cropping systems in recent decades in West African countries, even though most of the active molecules found are forbidden in several countries, especially in European countries. These are applied to tropical agricultural soils with physicochemical characteristics favorable to their retention in wet weather, as confirmed by the case of BW’s agricultural soils. Therefore, the BW’s water resources present worrying risks of contamination during rainy events that deserve to be assessed and monitored. Hence the need to take mitigating measures to this effect in order to preserve the quality of the environment. 展开更多
关键词 agrochimical Products Soils Contamination Water Resources Pollution West Africa Tropical Hydrosystems Béré Watershed Côte d’Ivoire
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