The Use of Mosses in Biomonitoring of Air Pollution in the Terrestrial Environment: A Review

The use of plants in the assessment of air pollution has been used for many years. The pioneers were the Scandinavian researchers Rühling and Tyler [1968]. The scientific literature is dominated by the classic definition of terms related to environmental bioindication proposed by Markert et al. [2003]: ‘A bioindicator is an organism (or part of an organism or a community of organisms) that contains information on the quality of the environment (or a part of the environment). A biomonitor, on the other hand, is an organism (or a part of an organism or a community of organisms) that contains information on the quantitative aspects of the quality of the environment’. Wolterbeek et al. [2010] proposed a much shorter definition ‘Biomonitoring, in a general sense, may be defined as the use of bio-organisms/materials to obtain (quantitative) information on certain characteristics of the biosphere’. Bioindication methods are used especially when we are dealing with many contaminants occurring simultaneously. They are also helpful in learning about the history of changes in the degree of pollution over hundreds of years. The final effect of properly used bioindication is a more complete picture of the state of the environment than assessed only by physico-chemical methods [Gorovtsov et al. 2017; Chaudhuri, Roy 2023]. Presentations of the benefits and falsification of bioindication methods are presented in Table 1.

Indicator plants can be divided into two basic groups [Birungi et al. 2007]: −

Passive bioindicators are living organisms that naturally occur in the study area. The disadvantage of their use is often the difficulty of finding them throughout the area, and the advantages of the lack of maintenance and lower research costs. In return, the interpretation of results must take into account an important number of criteria related to the heterogeneity of the living conditions: soil quality, climatic conditions and season, genetic variability and metabolic state, heterogeneity of the spatial distribution of selected species.

Bioindication methods make it possible to supplement physical and chemical tests, which usually show individual data of specific pollutants, not taking into account other pollutants and not taking into account the changing environmental conditions [Wolterbeek 2002]. Mosses, thanks to their properties discussed in further chapters, are very often used in the assessment of air pollution [e.g. Dołęgowska et al. 2021; Godzik 2020; Kapusta et al. 2020; Chaudhuri, Roy 2023].

The disadvantage of bioindication methods is the inability to obtain results with legal norms of pollutants determined by instrumental methods restrictions. In practice, it is often used to combine physicochemical measurements with bioindication observations. Zechmeister et al. [2003] showed that in the moss-bag method, the metal content in the exposed moss was correlated with the concentration in the air, which proves the effectiveness of this method. The effectiveness of moss testing methods in assessing air pollution is evidenced by the large number of international, national and local programs using these methods.

The aim of our publication was to assess the possibility of using mosses in biomonitoring of air pollution in the terrestrial environment. The effectiveness of various methods and their practical applications are discussed. The main international programs using mosses are presented. The analysis partly used the literature review method proposed by Snyder [2019] for environmental analyses. The literature search method PRISMA (Preferred Reporting Items for Systematic Review and Meta-analyses) was also used [Diener, Mudu 2021; Sarkis-Onofre et al. 2021; Chaudhuri, Roy 2023]. As a result of this procedure, 95 publications were selected for our review. Database searches of SCOPUS, Science Direct, Web of Science and Google Scholar were performed using the following search terms: biomonitoring, pollution, moss, moss-bac, metals, nitrogen, PAHs, persistent organic pollutants (POPs), urban, agriculture, country side, industrial, radionuclides, metals smelter.

Critical discussion of all basic bioindication methods based on the latest literature are elements of novelty. Thus, 50% of the publications used were from the last four years, and ‘historical’ publications from the previous century were also cited.

The selection of organisms bioindicators must be particularly careful and must meet many characteristics. The classic publications of Füreder and Reynolds [2003] and Gorovtsov et al. [2017] give a list of traits that must be met good bioindicators, most of which relate to the use of mosses: −

Taxonomic stability, easily recognised in the field by anyone;

Mosses are used in air pollution biomonitoring in three basic methods: (1)

Native mosses; −

Naturally growing mosses;

Rühling and Tyler [1968] pioneered the study of heavy metal accumulation in naturally growing mosses as indicators of air pollution. The earliest studies were conducted in Sweden [Rühling, Tyler 1968], Denmark [Pakarinen, Tolonen 1976], Finland [Makinen 1977], Norway [Steinnes 1977] and Poland [Grodzińska 1978]. Mosses are mainly used in the monitoring of air pollution with metals, but they can also be effective in assessing nitrogen deposition [Díaz-Álvarez et al. 2018].

The properties of mosses have made them dominant for many years in biomonitoring in basic academic and practical research [Markert et al. 2020]. Advantages of using native mosses in bioindication of air pollution: -

Mosses are used as bioindicators of complex contamination: wet and dry deposition, which facilitates the assessment of total contamination [Markert et al. 2003; Aničić et al. 2009];

When using methods with mosses as bioindicators, one must remember that the measurements are not always precise. According to Bargagli [2016], the determination of Hg content in mosses cannot, however, be used to accurately determine atmospheric deposition, but only allows to locate Hg hot spots and changes in spatial distribution. An important issue is the methodological correctness of biomonitoring studies. Fernandez et al. [2015] evaluated 362 scientific publications discussing methodological and application studies of biomonitoring of metal deposition by mosses. The conclusions of these reviews indicated that most studies did not fully meet the criteria for valid scientific research. This fact does not undermine the desirability of conducting biomonitoring studies with mosses, but requires caution when formulating final conclusions.

3.2.

Moss-bag method

The moss-bag method is based on the following properties of moss: -

Dry moss can absorb metals without significant limitations [Tavares, Vasconcelos 1996].

-

The metal content in the moss exposed in the bag is proportional to its concentration in the air [Zechmeister et al. 2003; Aničić et al. 2009; Sang et al. 2021].

Sphagnum are characterised by the ability to efficiently absorb metals in tissues and therefore have found widespread use in moss-bag methods [Ares 2012; Shvetsova et al. 2019]. Figure 1 shows a moss bag prepared for exposure. The method of moss exposure in the form of moss bags is by far the most commonly used. However, other forms of exposure were used, such as moss mats [Ares 2012].

Figure 1.

Sang et al. [2021] compared two methods of using mosses Barbula indica in the assessment of air pollution with elements: moss bag and native moss. The results obtained by both methods gave a similar view of contamination. Native mosses accumulated more pollutants, but the moss-bag method enabled measurements in urban environments where native mosses did not occur or died during the summer drought. Świsłowski et al. [2022] assessed urban air pollution with seven metals (Cu, Zn, Cd, Pb, Mn, Fe, Hg), comparing three moss species: Dicranum polysetum, Pleurozium schreberi and Sphagnum fallax, as a moss bag and native moss transplants in boxes. Pleurozium schreberi was recommended as the best bioindicator accumulating the most and tested metals, and the moss-bag method was recommended for biomonitoring due to the much higher content of metals than native moss.

Figure 2 shows an exemplary application of the moss-bag method in the assessment of air pollution with chromium in the area of heavy pollution from the steel mill source. The use of this method made it possible to show changes in air pollution over a long period (15 years) based on a large number of measurement points and the same research material [Dmuchowski et al. 2011b]. Table 4 presents examples of the use of moss-bag methods in pollution biomonitoring in different regions of the world.

Figure 2.

Table 4.

Examples of application of the moss-bag method in biomonitoring of air pollution

Air pollutant/deposition	Moss	Environment	Country	References
Pb	Hypnum cupressiforme	industrial	England	Goodman ans Roberts 1971
Cd, Pb, Zn	Sphagnum fallax	urban	Poland	Dmuchowski and Bytnerowicz 2009
18 elements	Hypnum cupressiforme	industrial	Italy	Tretiach et al. 2011
Cd, Pb	Sphagnum fallax	industrial	Poland	Dmuchowski et al. 2001a
Cd, Cr, Pb	Sphagnum fallax	still mill	Poland	Dmuchowski et al. 2011b
19 elements	Hypnum cupressiforme	urban	Italy	Giordano et al. 2013
Particulate matter	Sphagnum papillosum	industrial	Finland	Salo and Mäkinen 2014
PAHs*, 39 elements	Hypnum cupressiforme	urban	Italy	Capozzi et al. 2016a
10 elements	Pseudoscleropodium purum	agricultural, urban, industrial	Austria, Italy, Spain	Capozzi et al. 2016b
Sb, Cu, Cr	Sphagnum girgensohnii, Hypnum cupressiforme	urban	Serbia	Vuković et al. 2016
7 elements	Pleurozium ssp, Polytrichum ssp, Rhytidiadelphus ssp.	mining	Slovakia	Demková et al. 2017
Particulate matter, 23 elements	Pseudoscleropodium purum	agricultural, urban, industrial	Austria, Italy, Spain	Di Palma et al. 2017
9 elements	Sphagnum fallax, Dicranum polysetum	urban	Poland	Świsłowski et al. 2022
134Cs, 137Cs	Hypnum cupressiforme, Hypnum plumaeforme	Fukushima breakdown	Japan	Di Palma et al. 2022
12 elements	Taxiphyllum taxirameum	agricultural, urban, traffic, industrial	China	Mao et el. 2022
Microplastic	Pleurozium schreberi	urban, traffic. rural	Canada	Bertrim and Aherne 2023
PAHs*	Hypnum plumaeforme	urban	Malysia	Hanifah and Sani 2023
35 elements	Hypnum cupressiforme, Sphagnum girgensohnii	urban, rural	Southeastern Europe, 10 countries	Urošević et al. 2023

*

PAHs - Polycyclic aromatic hydrocarbons

Bioindication methods can be an important element in environmental monitoring. The relatively low cost and the possibility of using a large number of measurement points make them a perfect complement to the instrumental methods. Methods using mosses as effective bioindicators are particularly recommended. It can be said that in recent years, moss research has dominated biomonitoring around the world. The advantage of mosses over other bioindicators is that they collect pollutants only from the air. These methods have been used in international research programmes. Other methods that have also found wide application is the method with prepared moss – ‘moss bag’. The moss exposed in the bags can be displayed in places where moss does not occur naturally, such as urban and industrial environments. Features of biomonitoring, such as the relative simplicity of all elements: collecting moss samples, simple and cheap technical equipment, no need to employ super specialists, easy interpretation of the results obtained. All these properties cause that the biomonitoring of elements will develop and increase the scale and geographical scope of research The significant value of information from biomonitoring can only be discussed when it is linked to databases on the environment, pollutant emissions, changes in ecosystems, living standards and health of the population. The development of analytical physicochemical methods and computer science will not eliminate bioindication methods, which will remain as a supplement to more advanced methods. A threat to the use of bioindication with mosses is not following strict methodologies. Over interpretation of results and drawing unauthorised conclusions may discourage the use of mosses in biomonitoring.