Mercury (Hg) pollution seriously threatens food safety and has attracted global attention. Phytoextraction, due to its low cost, applicability, and environmental friendliness, is considered a new technology for clean-up of heavy metal contamination in the environment. However, the low bioavailability of Hg in polluted areas greatly limits the applicability of phytoextraction. Here, we compared the effects of six common chelating ligands on the absorption and transport of Hg in maize ( Zea mays L.), which has a high biomass and short growth cycle. The results showed that the root length and biomass of maize seedlings of the groups treated with the six chelating ligands (EDTA, iodide, ammonium, thiosulfate , thiocyanate, and thiocarbamide) did not change compared with those of the non-treated groups. Co-exposure to Hg and each chelating ligand markedly alleviated the inhibitory effect induced by Hg. Iodide treatment resulted in the lowest root Hg content and highest translocation factor (TF) value, while ammonium treatment gave rise to the highest shoot Hg concentration and lowest TF. Compared with other chelating ligands, thiosulfate exhibited the maximum alleviation of Hg toxicity and achieved the highest concentration of Hg in the roots and aerial parts. Moreover, the TF and Hg accumulation in the thiosulfate and Hg co-exposed group were much higher than those in the group exposed to Hg alone. This finding suggests that, among these common chelating ligands, thiosulfate compounds have great potential for Hg phytoextraction, while the others can immobilize Hg in polluted areas.
Thimerosal (THI) is widely used as an antimicrobial preservative, but can hydrolyze to ethylmercury, causing potentially neurotoxicity. In this work, a THP-1 cell line was used to investigate the biological behavior of THI. An on-line droplet microfluidic chip system combined with time-resolved inductively coupled plasma mass spectrometry was used to quantify Hg in single THP-1 cells. The cellular uptake and elimination behaviors of THI were studied, and the toxicity of THI in terms of redox balance was discussed. The results showed that a small number of cells (<5%) exhibited a high uptake content (>200 fg/cell) for THI, and most of the cells (68.8–85.8% for different exposure groups at 25 h) exhibited a relatively low uptake content (<20 fg/cell). After stopping exposure to THI, the cells showed an elimination process for Hg, which was rapid in the first several hours and gradually slowed down. When the elimination time was 25 h, 7.4–26.3% of the cells in different exposure groups still contained a detectable amount of Hg (>2 fg/cell), indicating Hg could not be eliminated completely, which may cause cumulative toxicity to macrophages. Moreover, it was found that exposure to THI even at 50 ng/mL can cause cellular oxidative stress behavior, leading to an increase in reactive oxygen species level and a decrease in glutathione level. This trend would continue for a period of time after stopping THI exposure. With the elimination of Hg, the redox balance of cells showed a tendency to stabilize and restore, but cannot be restored to normal status, indicating a long-term chronic toxicity of THI to THP-1 cells.
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