Heavy metals in the environment

The uptake of arsenic was studied in bean (Phaseolus vulgaris L.) and cabbage (Brassica oleracea L. var. capitata L.) in an open greenhouse pot culture with sand and silt soil as substrate. The plants were irrigated with water containing sodium arsenate at concentrations 0.05 and 0.2 mg As L-1. The total arsenic concentration of the different plants parts was determined by ICP-MS, following microwave-assisted acid digestion. The As concentration in the bean was in the order: root>shoot>bean pod and in cabbage: root>leaves. Increasing As concentration in the irrigation water resulted in decreased edible biomass production in bean, while in cabbage the edible biomass production increased. At the highest dose (0.2 mg As L-1) if a person consumes about 450g of bean then their As intake will be: 0.9 µg from bean grown in sand and 0.72 µg from bean grown in silt. If 450g of cabbage is consumed then the As intake would be: 22.5 µg from cabbage grown in sand and 12.15 µg from cabbage grown in silt.
Considering the WHO recommended MTDI limit of 2 µg kg-1 body weight, both bean and cabbage can be consumed at the highest As treatment level of 0.2 mg L-1.

Cobalt (Co) has significantly increased its concentration in the environment in the last years due to anthropogenic and industrial activities. The present study was designed to elucidate the effect of chronic cobalt chloride (CoCl2) exposure on transferrin receptor 1 (TfR1) in various organs of immature mice. Pregnant ICR mice were subjected to daily dose of 75 mg/kg body weight CoCl2x6H2O 2–3 days before they gave birth and treatment continued until day 25 after delivery. The compound was dissolved and administrated with drinking tap water. Age-matched mice obtaining regular tap water were used as a control group. On days 18 and 25 pups were sacrificed, blood plasma, livers, kidneys and spleens were obtained and processed for analysis. The results show altered tissue-specific TfR expression in the studied organs of CoCl2-treated immature mice. A significant time-dependent increase in tissue Co levels was observed. Our data on the effects of chronic CoCl2 exposure on TfR expression contribute for the elucidation of the complex regulatory mechanism of iron homeostasis.

Lead (Pb) directly targets testicular spermatogenesis and also the sperms in the epididymis inducing reproductive toxicity. In our study we compare the effects of meso-2,3-dimercaptosuccinic acid (DMSA) and tetraethylammonium salt of salinomycinic acid (Sal) on testis morphology, sperm count, Pb content, endogenous levels of calcium, copper, zinc and iron in testis of mice, subjected to Pb intoxication. Both chelating agents considerably reduced Pb content in the testis compared to the toxic control. The administration of Sal ameliorated Pb-induced alterations in Cu homeostasis and significantly restored endogenous Ca and Zn concentrations levels unlike DMSA. Testicular morphology of Pb-intoxicated mice recovered to control after salinomycin treatment but sperm count remained 21% lower compared to the untreated mice. The results suggest the potential application of salinomycin as antidote for treatment of lead intoxications.

In this study total mercury concentrations in earthworms and in different soil types at the same locations from the surroundings of four boreholes were analyzed by ICP-MS method, as a part of a comprehensive monitoring of the eco-system in the vicinity of the natural gas production and treatment plant Molve in northern Croatia. The aim of this study was to determine the concentration of mercury in the collected samples from 2009 to 2019, monitor its changes over a last ten years period and determine the bioaccumulation of total mercury in earthworms from the soil. During the last ten years total mercury concentrations in earthworms (boreholes Molve 9-12) ranged within 0.118 and 0.675µg gDW-1 depending on the location and time of sampling, while total mercury concentrations in different soil types at the same locations ranged within 0.020 and 0.515 µg Hg g-1 of soil. The calculated mercury bioaccumulation factor ranged between 0.6 and 16.9. Comparing our results with those from the previous research period and also with results published in available literature it can be concluded that investigated area near Molve belongs to low mercury contaminated region.

Two commercial activated carbons (F400 and RWE) were tested for their Hg° retention capacity, in order to elucidate shortcomings that still exist, with respect to the oxygen functional groups. The number and the nature of oxygen containing functional groups were altered by heating under H2 at 1100°C or treatment with HNO3. The activated carbons tested were found suitable for mercury retention and the observed differences are attributed to their diversified characteristics (surface chemistry and pore structure). Acidic activated carbons promptly adsorb Hg°, since it behaves as a Lewis basis. When oxygen groups were almost completely removed, by H2 thermal treatment, the Hg° retention ability became practically zero. Acid treatment increased both the number and the acidic oxygen groups; resulting in increased Hg° retention. The Langmuir isotherm equation was used to describe the adsorption (physisorption and chemisorption) of Hg°, occurring in activated carbons. The fitting curve of the Langmuir equation and the correlation coefficient R2 indicate quite fair linear approximation (R2 = 0.9773). Reflecting the spontaneous nature of the adsorption reaction, the Gibbs free energy change calculated is negative (-23.5 kJ/mol and -30.9 kJ/mol, for the RWE and F400 respectively).

Concerning toxicity, bioaccumulation and persistence in the aquatic environment, six metals such as Zn, Cu, Ni, Cr, Pb and Cd are attributed to priority hazardous substances in many countries throughout the world (Water Framework Directive 2008/105/EC; US EPA 2009). In this study, time-dependent and tissue-specific induction in geno- and cytotoxicity was determined in haemocytes and gills cells of Anodonta cygnea after treatment with six metals (Zn-0.1, Cu-0.01, Cr-0.01, Ni-0.01, Pb-0.005 and Cd-0.005 mg/L, at Maximum Permissible Concentrations (MPC), accepted for the inland waters in EU) mixture at various time points (1, 2, 4, 7, 14 and 28 days). The highest genotoxicity levels in gill cells and haemocytes were determined after 4 days exposure. After 2 days treatment in gill cells of exposed mussels, there was found the highest and statistically significant induction of cytotoxicity level. Neurotoxicity studies have shown, that prepared metals mixture has ability to inhibit AChE activity in mussel’s hemolymph after 4 days and 28 days exposure. Time-depended metals accumulation in A. cygnea gills and statistically significant relations between Cu, Cd, genotoxicity (in gill cells) and cytotoxicity (in gill cells) demonstrates bioavailability of used trace metals for the bioindicator and time-related DNA damage.