Metals in superficial sediments of a cascade multisystem reservoir: contamination and potential ecological risk

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Processo FAPESP: 2014/22581-8Cascade multisystem reservoirs are extremely complex ecosystems that require studies to improve understanding of their dynamics and functioning, including the effects of contamination with metals. In this work, superficial sediments were collected during two sampling campaigns (in the dry and rainy seasons) at 19 sites along a cascade multisystem reservoir in São Paulo, Brazil, formed by five reservoirs. The sediments were evaluated considering the following parameters: pseudo-total metals (Cu, Cd, Cr, Ni, Pb, Zn, Mn, Fe, and Al); bioavailable metal (Cu); organic matter; total phosphorus; total nitrogen; and grain size. In the last reservoir of this system, the enrichment factors indicated enrichment of Cu, Pb, Zn, and Mn. Despite this increased metals content, the pollution load index indicated an absence of pollution (PLI < 1), and the ecological risk was low (RI < 150). According to sediment quality guideline criteria, toxicity was unlikely to occur. Principal component analysis (PCA) and one-way ANOVA indicated heterogeneity among the reservoirs (P < 0.01) and between the sampling periods. The PCA results confirmed higher levels of nutrients in the upstream reservoirs, suggesting that nutrients were precipitated in the first reservoirs of the system. On the other hand, metal levels were higher in the downstream reservoirs. The main source of metal contamination in the region was the use of copper sulfate as an algicide. This included contamination by Pb and Zn, due to impurities in the copper sulfate employed. High Mn levels were associated with wastewater discharges and erosion. In addition to helping to improve understanding of the dynamics of metals in cascade multisystem reservoirs, this work could serve as a useful tool for the management of reservoirs with contaminated sediments

Reversed-phase separation methods for glycan analysis

Reversed-phase chromatography is a method that is often used for glycan separation. For this, glycans are often derivatized with a hydrophobic tag to achieve retention on hydrophobic stationary phases. The separation and elution order of glycans in reversed-phase chromatography is highly dependent on the hydrophobicity of the tag and the contribution of the glycan itself to the retention. The contribution of the different monosaccharides to the retention strongly depends on the position and linkage, and isomer separation may be achieved. The influence of sialic acids and fucoses on the retention of glycans is still incompletely understood and deserves further study. Analysis of complex samples may come with incomplete separation of glycan species, thereby complicating reversed-phase chromatography with fluorescence or UV detection, whereas coupling with mass spectrometry detection allows the resolution of complex mixtures. Depending on the column properties, eluents, and run time, separation of isomeric and isobaric structures can be accomplished with reversed-phase chromatography. Alternatively, porous graphitized carbon chromatography and hydrophilic interaction liquid chromatography are also able to separate isomeric and isobaric structures, generally without the necessity of glycan labeling. Hydrophilic interaction liquid chromatography, porous graphitized carbon chromatography, and reversed-phase chromatography all serve different research purposes and thus can be used for different research questions. A great advantage of reversed-phase chromatography is its broad distribution as it is used in virtually every bioanalytical research laboratory, making it an attracting platform for glycan analysis. [Figure not available: see fulltext.