Phosphorus seasonal sorption-desorption kinetics in suspended sediment in response to land use and management in the Guaporé catchment, Southern Brazil.

Phosphate sorption-desorption parameters like maximum phosphorus (P) adsorption capacity (P max), equilibrium phosphorus concentration (EPC), water desorbable P (α), potentially bioavailable P (ß), and mobility index (α/ß ratio) were determined in order to understand the sediment source-sink nature in Guaporé catchment in southern Brazil during summer and winter 2013 and 2014. The result showed a significant (p = 0.05) variation across sediment site or seasons and revealed the most sorption-desorption parameters (P max, α, ß) with the increments following the order urban sediments > intensive agriculture under CT > intensive agriculture under NT > low agriculture sub-catchments (sub1 and sub2) > native forest. In the main river points, these parameters decreased along the river (P1 to P5). The results were more obvious in winter than the summer season. In contrast, the low values of λ and α/ß ratio in the sediment from native forest and relatively less polluted catchment (sub1) during summer season show the quick P desorption when compared to specific Fe and Al oxides bound to stable P in intensive agriculture sediments. These findings clearly indicated that agricultural practices, sediment characteristics, and hydrological factors have a major impact on seasonal sediment P bioavailability and mobility. The urban untreated discharges may be a single major P source and, if it is not wisely managed, proves a major threat to water quality. These results have serious implications for the river ecosystem and will be of great importance to improve the environmental and economic performance of agricultural practices aiming to reduce soil-based P legacy to surface waters.

Using a two site-reactive model for simulating one century changes of Zn and Pb concentration profiles in soils affected by metallurgical fallout.

Predicting the transfer of contaminants in soils is often hampered by lacking validation of mathematical models. Here, we applied Hydrus-2D software to three agricultural soils for simulating the 1900-2005 changes of zinc and lead concentration profiles derived from industrial atmospheric deposition, to validate the tested models with plausible assumptions on past metal inputs to reach the 2005 situation. The models were set with data from previous studies on the geochemical background, estimated temporal metal deposition, and the 2005 metal distributions. Different hypotheses of chemical reactions of metals with the soil solution were examined: 100% equilibrium or partial equilibrium, parameterized following kinetic chemical extractions. Finally, a two-site model with kinetic constant values adjusted at 1% of EDTA extraction parameters satisfactory predicted changes in metal concentration profiles for two arable soils. For a grassland soil however, this model showed limited applicability by ignoring the role of earthworm activity in metal incorporation.

Soroprevalência de anticorpos contra o virus da hepatite A em região do semi-arido do estado da Bahia / Seroprevalence of anti-HAV antibodies in the semiarid region of the state of Bahia

As hepatites virais apresentam importante problema de saúde pública em todo mundo. Estudos de base populacional que investiguem os portadores do vírus da hepatite A (VHA) são escassos, sobretudo no semi-árido nordestino do Brasil, mas de fundamental importância para melhor dimensionar o problema e planejar medidas de controle. No povoado de Cavunge, localizado na região do semi-árido do estado da Bahia, está em andamento estudo sentinela sobre as hepatites virais. Objetivo: Determinar a soropositividade da hepatite A em comunidade rural do semi-árido do estado da Bahia; avaliar os aspectos socioepidemiológicos asociados à transmissão do VHA. Métodos: Estudo transversal. Após a aplicação de questionário ssociodemográfico foi realizada a colheita de sangue venoso para pesquisa de anticorpos séricos(IgG) anti-VHA (método ELISA) em 1.452 pessoas residentes na área urbana ou rural do povoado de Cavunge. Resultado: 83,3por cento(n=1.210) da amostra foram soropositivos. A proporção de soropoditivos foi semelhante entre os sexos, embora houvesse aumento significativo desses percentuais relativos à idade (p<0,001) e entre os residentes da área urbana (p<0,01). A maior prevalência da infecção ocorreu na segunda e terceira décadas de idade. Conclusão: Foi elevada a prevalência de portadores de anticorpos contra o virus da hepatite A no povoado da Cavunge e aumentou com a idade