Determination of the total concentration and speciation of metal ions in river, estuarine and seawater samples

Causes and mechanisms on the toxicity of layered double hydroxide (LDH) to green algae Scenedesmus quadricauda

Layered double hydroxides (LDHs) are widely used nanomaterials in industrial catalysis, pharmaceuticals, and environmental remediation, and may pose potential negative effects in the aquatic environment. However, little information is available on their toxicity to aquatic organisms. In this study, toxicity of LDH to a typical freshwater green algae Scenedesmus quadricauda was systematically investigated and the underlying mechanisms were elucidated. The growth of S. quadricauda was significantly inhibited by LDH at 72 h with a half maximal effective concentration (EC₅₀) and lowest observed effect concentration (LOEC) of 10.0 and 1.5 mg L^-1, respectively. Shading effect was observed, and the photosynthetic activity and cellular chlorophyll production were also severely suppressed by LDH. LDH also enhanced the reactive oxygen species production from S. quadricauda and lipid peroxidation in algal cells. Such algal toxicity of LDH might be mainly induced by the shading effect, agglomeration and physical interactions, and oxidative stress. The agglomeration and physical interactions contributed more to the algal toxicity at 72 h-EC₅₀ LDH concentrations. The results from the present study provided new insights and a better understanding of the environmental behavior and adverse effects of LDHs in the surface waters.

Metal complexation capacity of Antarctic lacustrine sediments

The purpose of this study is to implement a work that is a part of a project funded by the Italian National Antarctic Research Program (PNRA, Piano Nazionale di Ricerche in Antartide) within the main thematic focus "Chemical Contamination-Global Change". This research was devoted to detect and characterize micro and nano components with strong complexing capability towards metal ions at trace level in sea water, lakes and lacustrine sediments, sampled during the XXII expedition of PNRA. In particular, in the present work, the sorption complexation capacity of an Antarctic lacustrine sediments toward Cu(II) and Pb(II) is described. The characterization of the sorption was undertaken, studying kinetics and isotherm profiles. The lake here considered is Tarn Flat in the area of Terra Nova Bay. The sorption equilibria of Cu(II) and Pb(II) on the lacustrine sediments were reached in about 10 h, and they were best modelled by the Langmuir equation. Preliminary, to establish if the data here obtained were consistent with those reported for the same area in other expeditions, a common multivariate techniques, namely the principal component analysis (PCA), was applied and finally the consistency of the data has been confirmed.