Biomonitoring cadmium and nickel using native mosses in Leicester, UK

Background and Aim: Mosses provide information about atmospheric contamination by metals and their local spatial distribution. The aim was to conduct a preliminary analysis of cadmium (Cd) and nickel (Ni) in mosses collected from rural and urban environments in Leicester, UK. Methods: Native mosses were sampled from green spaces across Leicester/rural surroundings. Species identification was performed by DNA barcoding using bryophyte-specific primers on DNA extracted from 100 mg of frozen, homogenised, ground moss using Isolate II Plant DNA Kit®. After processing (soil removal, drying and homogenising), forty [31 urban; 9 rural] samples were mineralised with HNO3/H2O2. Cd and Ni were determined by atomic absorption spectroscopy; limits of detection were 0.0008 and 0.0072 µg/g, respectively. Results: Four moss species were identified: Ceratodon purpureus, Brachythecium spp., Hypnum cupressiforme, Kindbergia praelonga; H. cupressiforme is a useful, well recognised biomonitor. Cd was not detected in any of the samples, which agrees with recent work from Poland. Ni was observed in 13 samples, which were processed using maximum likelihood estimation method available in ‘NADA’ for the software R. Concentrations of Ni for the urban and rural areas (median and interquartile limits; µg/g): 0.0057 (0.0039-0.0084), and 0.0024 (0.0009-0.0064), respectively. Although slightly higher concentrations of Ni were found in the native mosses collected in the urban areas, perhaps reflecting different sources of pollution within Leicester city, the means did not show statistical difference (p-value, 0.626). The level of Ni was within the same range but lower than the medians described in larger biomonitoring studies performed in Germany (1.6 µg/g) and Moscow (2.87 µg/g), suggesting lower emission of this metal in Leicester. Conclusions: Undetectable Cd suggests environmental pollution with this toxic metal is minimal in Leicester, whereas Ni pollution may be more prevalent, however in both cases, analysis of more samples are needed to confirm these preliminary observations.