La manumisión de esclavos por compra y gracia en la Provincia de Antioquia, 1780-1830

This article analyzes the dynamics of the legal manumission of black slaves in the Province of Antioquia during the late colonial and early republican periods. A brief description of the effects that economic development had on the slavery in the Province is presented in the first section. Then, a review of the dynamics of manumission in Antioquia is given with base on the information extracted from primary sources including letters of freedom by purchase and by grace, lawsuits, ordinances, laws and decrees. This study shows that in spite of the influence of the particular conditions of the region on the successfulness of the strategies of freedom, the agency of the slaves must be regarded as an instrumental part of the dynamics of manumission during the period of interest.El artículo analiza las dinámicas de manumisión por gracia y por compra de los negros esclavizados en la Provincia de Antioquia durante los últimos años del periodo colonial y los primeros del republicano. En primera instancia se hace un breve esbozo del desarrollo económico de la Provincia y el impacto que generó en el sistema de explotación esclavista particular de esta región, para luego presentar un análisis de la manumisión por compra y gracia a partir de las cifras arrojadas por las fuentes primarias. Entre la documentación que se consideró en este estudio hay cartas de libertad, testamentos, pleitos judiciales, leyes, decretos, entre otros, emitidos en diferentes poblados de la Provincia durante el periodo estudiado. Este estudio muestra que a pesar de la gran importancia que tuvo el contexto particular de la Provincia en el éxito de las estrategias de libertad, la agencia de los esclavos debe ser considerada como uno de los principales motores que dinamizaron los procesos de manumisión

Occurrence of 1,1 '-dimethyl-4,4 '-bipyridinium (Paraquat) in irrigated soil of the Lake Chad Basin, Niger

Increased use of agrochemical products to improve yields for irrigated crops in sub-Saharan Africa has been accompanied by a significant increase in the risk of environmental contamination. Detailed examples of the fate of pesticides after initial spreading on crop fields are scarce in tropical regions, where safe practices and related health risks are poorly understood by smallholder farmers. In the semi-arid environment of the Lake Chad Basin, SE Niger, both intrinsic properties of pesticides and extrinsic factors such as soil and climate helped to characterize processes leading to an accumulation of pesticides in soils. Analysis by HPLC-UV of a 6 m deep soil profile showed the presence of Paraquat at concentrations from 953 +/- 102 mu g kg(-1) to 3083 +/- 175 mu g kg(-1) at depths between 0.80 and 2.75 m below the land surface. Soil analysis revealed that up to approximately 15 % of the total soil matrix consists of smectites, a clay mineral capable of retaining cationic pesticides such as Paraquat, and a very low content of organic matter (<0.15 wt.% TOC). Paraquat could be stored and not bioavailable in a clayey barrier at approximately 2-m depth and therefore does not represent an immediate risk for populations or environment in this form. However, if the Paraquat application rate remains constant, the clayey barrier could reach a saturation limit within 150-200 years and 180-220 years if we consider a DT50 in soil of similar to 1,000 days (FAO). Consequently, it could lead to a deeper infiltration and so a pollution of groundwater. Such a scenario can represent a health risk for drinking water and for the Lake Chad, which is a major resource for this densely populated region of semi-arid Africa. Further analyses should focus on deeper layers and groundwater Paraquat contents to validate or invalidate the hypothesis of storage in this clay-rich layer