The extraction of gold in the Amazon, since 1970, has grown fast from a politic that was resulted in the creation of gold extraction reserves in this region. In the Madeira River the gold exploration is noticeable because of the deposition of mercury in the environment. This metal is toxic and it resists to degradation process, transforming itself chemically, till it gets to its organic form, known as very toxic. Its extensive usage in the gold recover has caused impacts to the environment and consequently to the population, according to studies already done. This study has as its goal to value the pollution by Hg in soils and the variation according to soil fractions. The soils were collected by profiles in 10 areas in the Madeira River. The determination of organic matter was done, according (BRASIL, 1999).To Hg determination it was selected the fraction <200 mesh (<74 m), analyzed by atomic absorption spectrophotometer coupled vapor cold generation (Bastos et. al, 1998). Soils of the kind Latosols and hydromorphic were identified. The Latosols presented from 288 to 641 g.Kg -1 of clay and from 266 to 111 g.Kg -1 of thin send, from the horizon A 1 (superficial) to B 2 (sub-superficial). The increase of values of clay makes the function of organic matter in the superficial horizon better (from 20,2 to 19.0 %). The Hg concentration in these horizons varies from 25,5 to 641,4 g.Kg -1 in the superficial horizon. The hydromorphic, especially, the Fluvic Neosols, present thin area, 396 to 57 g.Kg -1 and clay from 254 to 654 g.Kg -1 from A 1 to A 2 . The horizon A 2 presents 467 g.Kg -1 of silt, 13,6 % of OM and 147,31 gHg.Kg -1 .Among the soils groups of the studied area, it is noticed more Hg concentration with the increase of values of silt and clay, that consequently presents more tenor of OM, and that subsidizes the organic mercury forming.
This study aims at analyzing the deforestation evolution correlated to the proposal of a territorial planning implanted by Rondônia Social-Economical and Ecological Zoning -SEEZ -decree number 4.297 signed in July 2002), regulated in 2002. In order to determine the indicators of degradation (deforestation), we opted for the analysis of maps of deforestation
This work evaluates natural soil fertility on plain and flooded terrace areas, at Madeira River-RO fluvial plain, based on physics and chemicals analyses, (pH, OM, Al +2 + H + , exchange bases K + ; Ca +2; Mg +2 e Al +3 ), physic-chemical (CEC, m% and V%), from the city of Porto Velho-RO to the city of Humaitá-AM. This kind of soil analysis is accomplished based on the percentage of base saturation (V%), which consists on physic-chemical phenomenon of ion absorption on clay and organic matter (OM) minerals. The soil samples were collected from temporary flooded plain strips and fluvial terraces with 20 km of intervals and 10 profiles described along the way, totalizing forty one (41) horizons. Using the EMBRAPA (1997) methods, the horizons A and B of each profile were considered. The results indicate four profiles with natural fertility deficiency: the Yellow Latosols at profile 1 and 2, Plintosols at profile 6 and Fluvic Neosols at profile 10, which may be related to the soil acidity, associated with high values of Al +3 , as well on plain soils (Plintosols and Fluvic Neosols), as fluvial terrace (Latosols). Soils under the influence of flooding regime present high V%. The potential CEC values of analyzed horizons, were found low in consequence of the mineral composition of the clay, its values were correlated to the OM activities. However, the highest clay samples activities have been found on the superficial horizon of Plintosols at profile 6 (Cavalcante Community), where the potential CEC has arisen despite of reduction of OM content. The CEC varies from soil to soil, and what determine its values are the organic colloid/clay structures and the quantity of OM.
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