Les leçons d'un échec : la culture attelée en pays Mossi (Haute-Volta)

Rémy Gérard. Les leçons d'un échec : la culture attelée en pays Mossi (Haute-Volta).. In: Cahiers d'études africaines, vol. 12, n°47, 1972. Systèmes agraires africains. pp. 512-519

L'enquête démographique à passages répétés

Rémy Gérard. L'enquête démographique à passages répétés.. In: Cahiers d'études africaines, vol. 12, n°47, 1972. Systèmes agraires africains. pp. 520-523

Total mercury concentrations in an industrialized catchment, the Thur River basin (north-eastern France): geochemical background level and contamination factors

River bottom sediments and soils were collected from the industrialized Thur River basin (north-eastern France) to assess mercury contamination. The regional geochemical background level of total mercury was evaluated to calculate mercury contamination factors (Fc) in soils and river bottom sediments. Our estimate of the mean background mercury levels in river sediments and soils, not affected by human activities, was 232 ng g1 (range: 27–406 ng g1). Sediments contaminated by the effluent from a chlor-alkali plant yielded the highest contamination factors (Fc¼1784). Contamination factors of surficial soils within 1 km of the industrial site range from 6.3 to 43.6. This contamination is attributed to diffuse atmospheric deposition from this local plant. However, even upstream from this industrial area elevated contamination factors were recorded for river bottom sediments (Fc¼3.2 to 26.4) and for one alluvial soil profile (Fc¼10). This is possibly due to past pollution resulting from waste water discharges. Mercury contamination in the different horizons of alluvial soils is not correlated with soil organic carbon content, but may be the result of occasional accidental pollution arising from the introduction of contaminated suspended particulate matter by the Thur River during periods of flooding