The Negro River (Ancash-Peru): A unique case of water pollution, three environmental scenarios and an unresolved issue.

This paper is focused on the hydrogeochemical characterization of the Negro River along its course, as well as in the proposal of a functioning model for the contamination processes in order to establish potential cause-effect relationships between water quality, geology (ARD), mining activities (AMD) and the tectonic framework as transmission vector of acidity, metals and sulphates. The scenario shows a heavily-contaminated river compared to the unaffected regional background. By graphical and statistical treatments of physico-chemical data of Negro River and the unaffected values of regional background and other AMD/ARD representative rivers' it is possible to conclude that Antamina Mine, is not the cause of the Negro River contamination, without the need of isotopic tracers, but just through the inexistent concentrations of Cu, Bi and Mo found in the waters. In the proposed contamination model, climatic factors (glacial retreat) activate geological (ARD) processes. The tectonic scenario (faults) intervenes as a transport medium of the contamination flux from the sulphide oxidation surface in upper altitudes until the spring in lower altitudes. At the end, it is concluded that this contamination comes from the recent glacial retreat in areas near the Cordillera Blanca that has left massive amounts of sulphide materials exposed to weathering conditions, oxidizing naturally (ARD processes) and finally contributing to the contamination of the Negro River through faults. In this case, we would face an ARD process in the strict sense, which is the direct oxidation of sulphides outcropping in the upper part of the mountain with the generation of sulphates, the release of hydrogen ions and the consequent generation of acid and the dissolution of the metals. This ARD process would come from the glacial retreat, which, through the faults, transports contaminated water until the spring.

Association among agro-industrial traits and simultaneous selection in sweet sorghum.

Sweet sorghum has emerged as an alternative crop for ethanol yield. The breeding of this crop is performed to obtain cultivars with high ethanol yield, which necessarily requires associating favorable phenotypes for multiple traits. Therefore, the aims of this study were to investigate the association between agro-industrial traits related to ethanol yield and identify the promising genotypes considering multiple traits in sweet sorghum. For this purpose, we evaluated 45 genotypes using a 9 x 5 alpha-lattice experimental design with three replications. The traits measured were flowering time, plant height, tons of stalk per hectare, total soluble solids, tons of brix per hectare, juice extraction, total recoverable sugars, and ethanol yield. Analyses were performed after the recovery of inter-block information. The interrelation of the traits was described by genotype-by-trait biplot. For simultaneous selection, the Modified Mulamba and Mock index was used. For almost all of the agro-industrial traits, except for juice extraction, selective accuracy was above 70%. There were significant differences among genotypes for all the traits. The genotype-by-trait biplot evidenced a positive association between most of the traits related to ethanol yield, except for juice extraction, indicating the possibility of indirect selection to obtain more productive genotypes. Some genotypes proved to be promising based on the selection index, as they accumulated phenotypes favorable for the traits of interest.

Path analysis of agro-industrial traits in sweet sorghum.

Sweet sorghum has considerable potential for ethanol production due to its succulent stalks that contain directly fermentable sugars. Since many traits need to be considered in the selection process to breed superior cultivars for ethanol production, then correlations between the traits might be of use to help the breeder define optimal improvement strategies. The aim of this study was to investigate the association between the principal agro-industrial traits in sweet sorghum, and to evaluate the direct and indirect effects of primary and secondary traits on ethanol production per hectare. In total, 45 sweet sorghum genotypes (lineage/hybrids) were evaluated in an experiment designed in an alpha lattice 5 x 9. The data were analyzed using a mixed model approach. A detailed study of simple correlations was accomplished using path analysis. The experimental precision was high, with an accuracy above 76%. The various genotypes showed genetic variation for all agronomic and industrial traits, except stalk diameter. Some agro-industrial traits showed significant simple correlations with ethanol production, but according to the path analysis, some of these traits did not show a significant direct or indirect effect on ethanol production. The results highlighted the primary and secondary traits with practical relevance to sweet sorghum breeding, since they showed director indirect effects on ethanol production.