LICHENS (Punctilia rudecta) AS BIOINDICATORS FOR AIR POLLUTION IN OHIO, USA
BRUCE W. BERDANIER
MUFEED I. BATARSEH
Prince Faisal Center for Dead Sea, Environmental and Energy Research, Mutah University,
ANWAR G. JIRIES, ANF H. ZIADAT
Abstract. Lichens were used as bioindicators for the assessment of atmospheric pollution with trace metals in Ohio, USA. The concentration of Iron, Copper, Cadmium, Manganese, Nickel, Lead, Zinc, and Cobalt were determined in lichen samples collected from the vicinity of Shelby town, Ohio. The hierarchical cluster analysis showed that the investigated sites are classified into three main groups. The first group included eight sites that might be affected by similar anthropo-genic activities due to similar heavy metals distribution profiles, while the other groups that consisted of only two sites are separated from the first group. That means that other types of anthropogenic activities might have affected them. These findings were confirmed using two-principle components analysis.
Keywords: lichens, heavy metals, atmospheric pollution, cluster analysis, Ohio.
1. Introduction
Lichens are considered the results of a symbiotic association of fungus and algae. Lichens do not have roots or well developed cuticle, therefore, they depend strongly on the mineral nutrients on wet and dry deposition making them a good bioindicators
TJ Smull College of Engineering, Ohio Northern University, Ada, OH 45810, USA
Many investigations were done worldwide using lichens as environmental bio-indicators [2, 7]. Lichens are effective biomonitors of metal deposition, as they possess many similar characteristics as air particulates. The metal concentrations in lichen (Rhizocarpon geographicum (L.) DC) have been shown to correlate with atmospheric dry deposition in Amman city, Jordan [11].
Lichens were first used as bioaccumulative indicators in relation to point emis-sion sources, where decreasing metal concentrations in species correlated with the increasing distance from the source [4]. Various physical-chemical processes can take place either in the atmosphere or/and in the plant that can lead to metals accumulation in the lichens: trapping insoluble particles, extra cellular, ion exchange
be good accumulators of many elements, particularly heavy metals and radio-nuclides [10]. Some heavy metals such as Pb, Zn, and Cu can be considered toxic for many other living organisms, that may be accumulated simultaneously in one lichen specimen, and appear to be unharmed [9]. Sampling period plays an impor-tant role in the levels of Cu, Zn, and Pb in lichens as higher levels are found usually in summer than in winter [3]. Since anthropogenic emission of trace metals such as Cd, Cu, Zn, and Pb to the atmosphere may give an environmental impact to flora and fauna, their survey is of key importance for the entire living environ-ment. The main objective of this study is to use Lichens as bioindicators for the assessment of atmospheric pollution with trace metals in Ohio, USA. The data were used to classify the investigated area into different clusters or zones, based on distribution of heavy metals and dominating anthropogenic activities.
2. Materials and methods
2.1. Study area
Shelby is a small city in Ohio/USA with a population of around 10,000 people. The investigated site is located in a humid region as it gets around 970 mm of rain per year falling over 137 days. The temperature ranges from 29°C during July to –8°C during January. Geologically, the main outcrops of the area are limestone and shale exposed at 330–405 m ASL altitudes with no hills or deep valleys.
Lichens sampling was performed during summer 2008 from different parts of Shelby city, Ohio/USA. The sampling sites were chosen randomly from different parts of the city as the main source of pollution is mainly originated from traffic activity and a small coal burning power plant, as there is no major industry in the city (Fig. 2.1.1).
B.W. BERDANIER ET AL.
processes, adsorption and active uptake [1, 8]. Additionally, lichens have proved to
LICHENS (Punctilia rudecta) AS BIOINDICATORS FOR AIR POLLUTION IN OHIO 151
Fig. 2.1.1. Location map of investigated sites L1–L10.
2.2. Sample collection
Healthy lichens from rock surfaces were collected from 10 locations in Shelby town, Ohio, USA during summer 2008, representing different sites within the town (Fig. 2.1.1). Three replicates were collected from each site to get a represen-tative sample and accurate results. The heavy metals are selected in the investiga-tion area based on their toxicity and possible sources of metal pollution. The following elements were investigated: Cd, Cu, Pb, Zn, and Co in the lichen thallus species Punctilia rudecta from a well-defined family of lichens that usually grows on rocks in Ohio [5].
2.3. Sample analysis
Directly after collecting hydrated lichens from previous rain, the samples were transferred to the laboratory and washed with distilled water for about 25 s to remove any collected dust on the lichens surface that might interfere with the analysis; elemental composition of unwashed samples is affected by soil dust con-tamination, thereby leading to incorrect interpretations of baseline concentrations and relationships between elements [7]. Washing the samples should not have any
Demonstrated that the younger, more external part of the thallus (corresponding to biomass produced the previous year) contained lower concentrations than the older, more internal part. In a study all part of lichens were used to eliminate lichens age on the results.
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effect on the trace metal content as the metals are more tightly bound or seques-tered within lichens and, therefore, more slowly released [6, 9]. Washed samples were dried at room temperature and then oven-dried to a constant weight at 80°C. The dried lichens samples were then prepared for metal analysis after being ground, using an agate mortar to avoid metal contamination. A 0.5 g amount of dried lichens samples was digested in a mixture of concentrated HNO3 and HClO4 (2:1) at 80°C using heating blocks overnight. The samples were filtered through Whatman filter paper no. 42 and diluted to 25 ml with deionized water (18.3 mOhm cm−1). The total concentrations of Cd, Cu, Pb, Zn, and Co in the samples were determined using Shimadzu atomic absorption spectrophotometer (Japan).
3. Results and discussion
The concentrations of heavy metals in the samples taken from different parts of Shelby city Ohio are summarized in Table 3.1. Heavy metal ranges were measured on dry weight basis as follows: Cu 13.9–63.3 μg·g–1; Fe 1644.2–9823.6 µg·g–1; Ni: 4.2–60.2 µg·g–1; Pb: 9.6–538.6 µg·g–1; Cd: ND-3.5 µg·g–1; Zn: 52.0–669.0 µg·g–1; Co: 1.8–7.4 µg·g–1; Mn: 150–458.4 µg·g–1, Table 3.1.
The concentrations of trace metals were measured using external calibration of a multi-element standard solution (r2 > 0.9995). The analyses were carried out in triplicate, and the average values were reported. Instrument precisions were determined by introducing the same quantity of one sample 20 times, and then the relative standard deviation was calculated (RSD < 5%).
Table 3.1. Concentrations of trace metals (mg/kg) in Lichens.
LICHENS (Punctilia rudecta) AS BIOINDICATORS FOR AIR POLLUTION IN OHIO 153
The maximum concentrations were found at the sampling sites surrounding the city center. High values of Cu, Fe, Cd, Mn, Ni, Pb, Zn and Co were measured in different parts of Shelby city, however, city center showed higher concentration levels. The main source of pollution was mainly from traffic and not from coal burned power station which was negligible as the results did not show any trend indicating that there is no point source pollution in the investigated area although a small coal burning plant exists in the area. Thus, Pb levels were found to be rela-tively high in Punctilia rudecta. The highest concentrations among analyzed metals were found for Mn, which ranged from 150 to 458 mg kg–1 with an average value of 290 mg kg–1. These high concentrations are due to the use of unleaded fuel, which is known to contain high levels of Mn. The distribution of analyzed trace metals are shown in Fig. 3.1.
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Fig. 3.1. Concentrations (mg/kg) of trace metals at investigated sites (L1–L10).
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The correlation coefficients (r) between common metals in lichens were calcu-lated in order to evaluate the possibility of a potential common source. Significant correlation coefficients (r < 0.05) of 0.93, 0.80, and 0.79 for Pb-Cd, Co-Cd and Pb-Co, respectively, indicating that the vehicular emission is the main source of heavy metals in lichens[2].
Hierarchical cluster and principle component statistical analyses were done, using NTSYSY-pc software version 4.0, for more data manipulation and interpre-tation. The hierarchical cluster analysis was carried out in order to classify the sampling locations into different groups. Therefore, Euclidean distance coefficient was calculated for all investigated locations (L1–L10) based on heavy metals con-centration. The result is presented by hierarchical analysis (dendrogram), Fig. 3.2.
Fig. 3.2. Dendrogram representing the hierarchical analysis of sample locations (L1–L10) according to analyzed metal concentrations.
The results allowed to classify the investigated sites into three main groups: A1, A2, and A3. The first group included those sites (L1, L2, L3, L5, L6, L7, L8 and L9) that might be affected by similar anthropogenic activities. While the dendro-gram showed that groups A2 and A3 are separated from group A1, that means that the locations (L4 and L10) might be affected by other anthropogenic activities which leads to the occurrence of different heavy metal levels. Furthermore, group A1 can be divided into two subgroups, A1-a includes locations (L2, L3 and L6) and A1-b (L1, L5, L8 and L9), sharing similar heavy metal concentration trends.
Moreover, two principle components analysis used in Fig. 3.3 accounted for the ten sample locations and were based on analyzed metal concentrations. The prin-ciple component 1 (PC1) and principle components 2 (PC2) separated clearly three groups (A1, A2 and A3). These results confirm the findings of the hierarchical clus-ter analysis. Group A1 is consisting of sampling locations (L1, L2, L3, L5, L6, L7,
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L1
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Euclidean Distance Coefficient
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D.18 D.TT 1.16 1.55 1.95
L8
LICHENS (Punctilia rudecta) AS BIOINDICATORS FOR AIR POLLUTION IN OHIO 155
L8, and L9) that are characterized by similar heavy metal concentration profiles. Whereas, location L4 within group A2 was characterized by low concentrations of Cu, Cd, Zn, Pb, Fe, and Mn, and high concentrations of Ni and Co. (Fig. 3.2). Location (L10) was classified as a separate group A3 because it is characterized by high concentrations of Fe, Cd, Mn, Pb, and Co, and low concentrations of Cu, Ni, and Zn.
Fig. 3.3. Principle components analysis of sample locations (L1–L10) based on analyzed metal concentrations.
4. Conclusion
The amounts of heavy metals accumulated by lichens in Ohio metropolitan is mostly dependent on traffic density. Eight sampling locations showed similar accu-mulation trends, while two locations were found far away regarding the heavy metal concentration levels. This trend is pinpointing of traffic source. Coal burning power plant in the area did not have any influence on the heavy metals distribution.
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