Influence of Speciation of Thorium on Toxic Effects to Green Algae Chlorella pyrenoidosa

Abstract

Thorium (Th) is a natural radioactive element present in the environment and has the potential to be used as a nuclear fuel. Relatively little is known about the influence and toxicity of Th in the environment. In the present study, the toxicity of Th to the green algae Chlorella pyrenoidosa (C. pyrenoidosa) was evaluated by algal growth inhibition, biochemical assays and morphologic observations. In the cultural medium (OECD TG 201), Th(NO3)4 was transformed to amorphous precipitation of Th(OH)4 due to hydrolysis. Th was toxic to C. pyrenoidosa, with a 96 h half maximum effective concentration (EC50) of 10.4 μM. Scanning electron microscopy shows that Th-containing aggregates were attached onto the surface of the algal cells, and transmission electron microscopy indicates the internalization of nano-sized Th precipitates and ultrastructural alterations of the algal cells. The heteroagglomeration between Th(OH)4 precipitation and alga cells and enhanced oxidative stress might play important roles in the toxicity of Th. To our knowledge, this is the first report of the toxicity of Th to algae with its chemical species in the exposure medium. This finding provides useful information on understanding the fate and toxicity of Th in the aquatic environment.

Exploring the Biotechnological Value of Marine Invertebrates: A Closer Look at the Biochemical and Antioxidant Properties of Sabella spallanzanii and Microcosmus squamiger

“…Thorium has three alpha-emitting radioisotopes: 228Th (T 1/2 = 1.91 y), 230Th (T 1/2 = 7.54 × 10 4 y), 232 Th (T 1/2 = 1.4 × 10 10 y) [ 99 ], has very low water solubility and strongly adsorb onto organic/inorganic particles, being therefore rather unavailable for biological uptakes [ 100 ]. Adsorbed Th enters the human body through inhalation or ingestion or through skin wounds and excessive exposure can induce cancer of the liver, lungs, pancreas, spleen, bone, and blood [ 101 ]. Th originates from the air and terrestrial sources to the marine environment [ 102 ], and was detected in feedstuffs, such as meat-bone meal and fish meal from aquaculture [ 103 ], and in molluscs and fish collected from the Southern Baltic Sea [ 104 , 105 ].…”

Physical and chemical characterization of natural and modified nanoclays and their ecotoxicity on a freshwater algae species (Chlamydomonas reinhardtii)

“…A test evaluating the toxic effects of each nanoclay type on algal population growth revealed that Cloisite 30B was more toxic than the other 2 nanoclay types (Results ‐ Chlamydomonas reinhardtii ), and results from our elemental analysis (Results ‐ Elemental composition of nanoclays) indicate that Cloisite 30B has higher amounts of fluorine (F) and thorium (Th), both of which are known to be harmful to algae (Smith and Woodson ; Hekman et al ; Peng et al ). We evaluated the degree to which each of the nanoclays we studied leached F and Th into solution.…”

“…Fluorine is a very strong oxidizing agent and can negatively affect the population growth of algae when its concentration exceeds 10 mg/L (Smith and Woodson ; Hekman et al ; LeBlanc ; Joy and Balakrishnan ; Bhatnagar and Bhatnagar ; Camargo ). Thorium has a high affinity for living material in aquatic environments (Gadd and White ) and can inhibit the population growth of the green algae Chlorella pyrenoidosa when the concentration exceeds 7.2 μM (Peng et al ). We found that Cloisite 30B releases very low concentrations of F ( ± 1 SD = 0.02 ± 0.003 mg /L) and Th (nondetectable levels) into water.…”

Determination of Self-absorption Correction Factors of Some Algae Samples: An Experimental study

“…Algaes are an important component of the marine ecosystem. Algaes are ubiquitous in the water system and have colonized almost every part of the globe [2]. Since ancient times, they have been used for food, feed, fertilizer, and medicine all over the world, and they are still used in skin care products today.…”