Reciprocal Effects of Metal Mixtures on Phytoplankton

Several types of contaminants are anthropogenically introduced into natural aquatic ecosystems and interact with other chemicals and/or with living organisms. Although metal toxicity alone has been relatively well studied, the toxic metal ion effects in the mixture have been thoroughly studied only during the last decades. This review focuses on the published reciprocal effects of different metals on different species of algae, together with describing their toxic effects on studied parameters. Phytoplankton as a bioindicator can help to estimate the reciprocal metal risk factor. Many methodologies have been developed and explored, such as the biotic ligand model (BLM), concentration addition (CA), independent action (IA), sensitivity distribution of EC50 species sensitivity distribution (SSD curves), and others, to study reciprocal metal toxicity and provide promising results, which are briefly mentioned too. From our review, we can commonly conclude the following: Zn acted antagonistically with most heavy metals (Al, Cu, Cd, and Ni). The Cu interaction with Cd, Fe, and Pb was mostly antagonistic. Cd showed synergistic behaviour with Hg, Cu, Zn, and Pb and antagonistic behaviour with Co and Fe in many cases. Methods and techniques need to be developed and optimised to determine reciprocal metal toxicity so that the ecotoxicological predictions made by using phytoplankton can be more accurate and related to real-time toxic metals risks to the aquatic ecosystem. This is the main objective of ecotoxicological tests for risk assessment. Understanding how metals enter algal cells and organelles can help to solve this challenge and was one of the main parts of the review

Solubilization of toxic metal mineral by the Aspergillus niger strain and oxalic acid

The objective of this study is solubilization of lead and arsenic from toxic metal mineral lead arsenate hydroxide - hydroxymimetite with oxalic acid and distilled water. Furthermore, the Aspergillus niger (A. niger) strain was applied for solubilization of lead and arsenic from hydroxy-mimetite. Oxalic acid was confirmed as the best leaching agent and was able to mobilize 96% of As and 1.49% of Pb. Also, the oxalic acid was capable of solubilizing inorganic Pb from crystalline compound and transforming it into the different organic Pb phase, which partially precipitated as lead oxalate Pb(C2O4). Our experimental studies bring insight into the biogeochemical cycles of the studied elements and have potential application in the bio-hydro-metallurgical processes for recovery of arsenic and lead from different materials (e. g. toxic metal minerals, mining ores, contaminated soil and sediment and other environmental area).Web of Science2182297228