Heavy metal and nitrogen concentration in
mosses in Irish Atlantic oak woodland
Kayla Wilkins and Julian Aherne
Trent University, Environmental and Life Sciences, Peterborough, Ontario, Canada K9J 7B8 [[email protected]]
Mosses are widely used as bio-monitors of atmospheric heavy metal and nitrogen deposition [1]. The objective of
this study was to compare the tissue chemistry of two moss species, Isothecium myosuroides and Thuidium
tamariscinum in Irish Atlantic oak woodlands, and to evaluate their relationship with indices of atmospheric
deposition.
Methods. Moss species were collected from thirty-nine Quercus
petraea-Luzula sylvatica woodlands (Irish National Survey of Native
Woodlands [2]) during April 2013; at twenty-two of these sites both
Isothecium myosuroides (Im) and Thuidium tamariscinum (Tt)
pleurocarpus moss species were sampled (Figure 1). Samples were
oven dried at 57C for 70 hrs, and pulverized in a mixing mill. Samples
were analysed for % CNS using an Elementar vario Marco CNS
analyzer, and for trace metal concentrations using Triple-Quad ICP-MS
analysis after microwave digestion (Mars 6 digester; EPA method
3052). The %N and %S tissue content, and heavy metal
concentrations, were compared between species with a Spearman’s
rank correlation test. The %N tissue concentrations were compared
with mapped total nitrogen deposition and atmospheric ammonia
(NH3) concentrations using Pearson’s correlation statistic.
Atmospheric NH3 (μg m–3)
0.09–0.70
0.70–1.32
1.32–1.94
1.94–2.56
2.56–3.17
Isothecium (%N)
0.65–0.91
0.91–1.16
1.16–1.42
1.42–1.68
1.68–1.93
Figure 1. Map of Ireland showing mapped atmospheric ammonia
(NH3) concentrations and nitrogen content (%) of Isothecium
myosuroides at the study sites.
2.5
2
y = 0.88 + 0.47x R2= 0.65
2.0
Figure 2. Tissue nitrogen content (%) in two moss species against
atmospheric ammonia (NH3) concentrations.
1.5
1.0
Isothecium myosuroides
Thuidium tamariscinum
0.5
0.0
0.5
1.0
1.5
Atmospheric ammonia (µg m–3 )
2.0
2.5
Table 1. Summary statistics for moss (Im: Isothecium myosuroides and Tt: Thuidium tamariscinum) tissue content analysis of
nitrogen and sulphur (%), and heavy metals ( mg/kg–1); Note: asterisk indicates significant correlation between species.
%N*
Im Tt
%S
Im
Tt
Al*
V*
Im Tt Im Tt
Cr
Im Tt
Fe
Im
Tt
Ni*
Im Tt
Cu*
Im Tt
Zn*
Im Tt
As*
Im Tt
Cd
Im Tt
Sb*
Im Tt
Pb*
Im Tt
Min.
Max.
0.65 0.83 0.07 0.07 27.9 17.8 0.38 0.36 0.52 0.73 134.0 104.6 0.58 0.51 1.10 1.56 10.27 12.10 0.05 0.03 0.05 0.02 0.02 0.00 0.68 0.34
1.93 2.28 0.20 0.18 189.4 97.6 1.14 1.12 1.66 2.51 523.9 516.5 1.64 1.61 4.60 5.33 71.74 35.43 0.34 0.26 0.41 0.13 0.13 0.07 4.37 2.39
Mean
1.23 1.34 0.10 0.10 68.6 39.3 0.76 0.68 1.04 1.28 262.3 242.1 1.17 0.99 2.51 3.17 26.43 20.64 0.12 0.09 0.16 0.07 0.06 0.03 2.00 1.08
Median 1.06 1.39 0.09 0.10 61.4 34.7 0.77 0.65 1.03 1.19 254.0 208.0 1.13 0.98 2.50 3.05 22.89 19.35 0.09 0.06 0.14 0.07 0.05 0.03 1.59 1.03
References. [1] Harmens, H. (2009). Monitoring of Atmospheric Deposition of Heavy Metals, Nitrogen and POPs in Europe using Bryophytes. ICP
Vegetation Coordination Centre, United Kingdom. [2] Perrin, P., et al. (2008). National Survey of Native Woodlands. Woodland Classification.
unpublished report: National Parks and Wildlife Service. [3] Henry, J. and Aherne, J. (2014) Nitrogen deposition and exceedance of critical loads for
nutrient nitrogen in Irish grasslands. Science of the Total Environment. 470-471: 216–223.
Acknowledgments. Financial support for this research was provided by the
Irish Environmental Protection Agency under the Climate Change Research
Programme (CCRP) 2007-2013.
www.trentu.ca
Nitrogen content (%)
Results. Heavy metal analysis and % CNS (Table 1) indicated that
Al, V, Ni, Cu, Zn, As, Sb, Pb, and %N were significantly correlated
between species, suggesting that they can be used
interchangeably in determining spatial patterns of atmospheric
pollution for these elements. The %N tissue content ranged
from 0.65−1.94% in Im and 0.83−2.28% in Tt. A simple linear
regression suggested that the %N tissue content in both species
was significantly related with mapped ammonia (NH3) air
concentrations (Figure 2). Since NH3 constitutes the majority of
total N deposition in Ireland [3], this suggest that monitoring
%N tissue content may be a valuable tool for assessing regions
or habitats that are potentially threatened by atmospheric N
deposition. The most strongly correlated metals were Al, Fe and
As (r > 0.75), and Pb and Cd (r > 0.75). Several metals were
positively correlated with non-marine sulphate deposition (V,
Ni, Cd and Pb) suggesting anthropogenic sources.
y = 0.80 + 0.43x R = 0.67