Effects of clouds on the surface shortwave radiation at a rural inland mid-latitude site

Seven years (2003–2010) of measured shortwave (SW) irradiances were used to obtain estimates of the 10 min averaged effective cloud optical thickness (ECOT) and of the shortwave cloud radiative effect (CRESW) at the surface in a mid-latitude site (Évora — south of Portugal), and its seasonal variability is presented. The ECOT, obtained using transmittance measurements at 415 nm, was compared with the correspondent MODIS cloud optical thickness (MODIS COT) for non-precipitating water clouds and cloud fractions higher than 0.25. This comparison showed that the ECOT represents well the cloud optical thickness over the study area. The CRESW, determined for two SW broadband ranges (300–1100 nm; 285–2800 nm), was normalized (NCRESW) and related with the obtained ECOT. A logarithmic relation between NCRESW and ECOT was found for both SW ranges, presenting lower dispersion for overcast-sky situations than for partially cloudy-sky situations. The NCRESW efficiency (NCRESW per unit of ECOT) was also related with the ECOT for overcast-sky conditions. The relation found is parameterized by a power law function showing that NCRESW efficiency decreases as the ECOT increases, approaching one for ECOT values higher than about 50.

Geochemical analysis of sediments from a polluted waterway in the vicinity of a metallurgical plant, Minas Gerais, Brazil

Mining and metallurgical industries are the most responsible for heavy metal contamination. These contaminants are often associated to poor management strategies and the lack of suitable containment areas. This is the case of one of the largest metal alloy producers in the São Francisco river basin, in Minas Gerais state, Brazil. During operation, the tailings of this activity have been accumulated in the surrounding area, leading to heavy metal contamination (Mn, Cu, Zn, Ni, Pb, Cd, Cr and As), much above the critical levels, which accumulate in the sediments of the nearby waterways, in the soils of the drainage area, and in the water column. In this work we are going to discuss both the contamination level and its extent in the Consciência river, a small tributary of the São Francisco river, the longest river entirely Brazilian, by analyzing the geochemistry and mineralogy of the accumulated sediments. It will be also discuss the reclamation strategies of this site and the impact on the environment.