Influence of zinc and manganese enrichments on growth, biosorption and photosynthetic efficiency of Chlorella sp.
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RESEARCH ARTICLE
Influence of zinc and manganese enrichments on growth, biosorption and photosynthetic efficiency of Chlorella sp. Adriana Ciurli 1 & Daniela Di Baccio 2 & Andrea Scartazza 2 & Martina Grifoni 2 & Beatrice Pezzarossa 2 & Carolina Chiellini 1 & Lorenzo Mariotti 1 & Alberto Pardossi 1 Received: 16 April 2020 / Accepted: 28 September 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Treating biosolids from industrial, urban, and agricultural plants produces high amounts of water. After organic pollutants and non-essential heavy metals have been removed, these wastewaters are still rich in trace elements such as zinc (Zn), copper, or manganese (Mn) and have high conductivity and extremely variable pH. In this study, an isolated Chlorella sp. strain was grown for 21 days in nutrient solutions enriched with known amounts of Zn or Mn to obtain concentrations three (4.0 mg Lā1)- and six (1.0 mg Lā1)-fold higher than the basal medium levels, respectively, and over the limits permitted in aquatic environments. The green alga exhibited high tolerance to Zn and Mn, with the maximum abatement of Zn (28ā30%) and Mn (60ā63.5%) after 14 and 7 days of culture, respectively. Mn stimulated the growth rate and biomass production of Chlorella, which showed the highest carbon levels just in the first week. In both treatments, the nitrogen and protein contents remarkably increased. The photosynthetic pigments increased until the 14th day, with a higher extent in the Zn-enriched solution. An increasing photochemical efficiency was observed after 7 days of treatment, when the microalgae grown in Zn- and Mn-enriched solutions showed a slightly higher maximum photochemical efficiency than control. The autotrophic and controlled growth system adopted was designed to monitor the dynamic balance of Zn and Mn contents in the solutions and in the algal biomass. This system has proved to be useful in identifying the optimal nutritional conditions of the microalgae, along with the optimal temporal patterns of both metal biosorption capacity for water remediation and element bioaccumulation in the algal biomass. Keywords Bioaccumulation . Biofertilisation . Chlorophyll fluorescence . Photosynthetic pigments . Trace elements . Zn and Mn balance
Introduction Heavy metals are stable and persistent contaminants of environmental and health concerns, and they are released into the environment through waterways due to several anthropogenic activities such as mining, electroplating, the production of electronics, fertilizers, pesticides, and pharmaceutics (Alloway 2013). Responsible Editor: Gangrong Shi * Daniela Di Baccio [email protected] 1
Department of Agriculture, Food and Environment, University of Pisa, via del Borghetto 80, I-56124 Pisa, Italy
2
Research Institute on Terrestrial Ecosystems, National Research Council, via G. Moruzzi 1, I-56124 Pisa, Italy
Effluents containing heavy metals from industrial, agricultural, or urban processes are mainly wastewaters and biosolids, which have historicall
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