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References

1 Introduction

Monitoring trace metal deposition using lichen bags is inexpensive, independent of power supply, and can provide information on the bioavailability of persistent atmospheric pollutants and their biological effects (Bargagli 1998; Brown 1984; Carreras and Pignata 2002; Castello 1996; Figueira et al. 2002). In the last 30 years, plant leaves, lichens, and mosses have been increasingly used for assessing the atmospheric deposition of trace elements and/or biological effects of airborne pollutants (Bargagli 1998; Figueira et al. 2002; Aksoy and Ozturk 1996; Aksoy and Ozturk 1997; Aksoy et al. 1999).

Knowledge of the uptake and accumulation processes of airborne pollutants, their persistence in moss and lichen bags, and possible synergistic and/or antagonistic effects of climatic and environmental factors is scant. The relationship between concentrations in atmospheric deposition and those in lichen and moss bags is also poorly investigated.

In fact, a purely instrumental approach to pollution monitoring has several weak points: despite the precision of measurement, recording gauges do not give information either on the bioavailability of pollutants or on their biological effects, and pollutants occurring at very low concentrations, such as trace elements, are often neglected. This can lead to gross underestimation of possible health effects, as some metals have synergistic toxicity and a hazard may exist even under low-dose exposure conditions. In urban areas, where lichens are often scarce or even absent, the "bags technique" has been set up and developed in order to monitor city air pollution. Bags consist of a mesh or grid, generally made of nylon, containing water-washed lichens. This technique has the following advantages: uniformity of entrapment surface and exposure period, flexibility both in site selection and in the number of stations that can be chosen, known original concentrations of contaminants in the biomonitors and greater collection efficiency for most elements. In addition, bags eliminate the possibility of contamination via root uptake and, in comparison with dust fall jars or bulk samplers, offer lower cost and higher efficiency. The major limitation of the method is in the unknown collection efficiency for different contaminants. Thus, the measured metal concentrations might reflect relative rates of deposition and not the total atmospheric load of contaminants. The duration of exposure is another critical aspect of biomonitoring by bags. Biomonitors may reach a saturation point for the uptake of an element and biomonitoring performance may also be altered by climatic and environmental conditions (Bargagli 1998). Compared with instrumental monitoring, concentrations of trace elements in the thallus are easily quantifiable with common analytical procedures and are related to those in wet and dry atmospheric depositions. The use of biomonitors is found to provide a high density of sampling points, which is indispensable for drawing reliable maps of pollutant depositions, and for giving information on long-term pollution effects (Bargagli et al. 2002).

Plasma Optical Emission Spectrometer (Inductively Coupled Plasma Optical Emmision Spectrometry = ICP-OES) is suitable for heavy metal determination and it is preferred by many research centres (Lara et al. 2001; D'angelo 2001).

In 2005, a bioaccumulation study of trace elements was carried out in the Kayseri urban area in Turkey using the lichen Pseudevernia furfuracea (L.) Zopf., transplanted in 29 city sites. The sites were selected near automatic air pollution and where meteorological monitoring devices were already fixed. In this study; Pb, Cd, Cu, Zn, Cr, and Co contents in exposed bags of P. furfuracea were measured.

2 Material and Methods 2.1 Study Area

Kayseri is a densely populated city (1,560,432 people in 2000). In the city, there is a definite boundary which distinguishes between urban and suburban sites. Urban sites were chosen at least 10 m away from a main road, and urban roadside sites were selected mainly near the city center along main roads. All urban roadside samples were chosen between 0 and 5 m, usually not more than 2 m away from the main road. Urban park sites were chosen from five large parks in Kayseri, mainly near the roads where the traffic density is not so high. Industry sites were chosen from the industrial area of the city. Shanty sites were chosen from five shanty zones around the city and control sites were chosen south of the Kayseri and more than 10 km away from any source of pollution. The city is crossed every day by an average of 162,000 vehicles driving through the city (Anonymous 2003). According to measurements from these stations, the study area has a Mediterranean climate characterised by dry summers and warm temperatures. In Kayseri, the annual rainfall is 368.4 mm and a mean annual temperature 10.6°C (Fig. 3.1). The urban area of Kayseri is affected by contamination from SO2 and particle matter (PM) in the atmosphere (Fig. 3.2).

2.2 Lichen Sampling and Bag Preparation

Pseudevernia furfuracea was collected from Qat forests on the bark of pine trees in the rural area of Sizir in the Sivas Province (39° 24.665' N, 35° 51.369' E, Turkey), at nearly 1582 m above sea level, far from large urban and industrial settlements. Homogeneous specimens were made by carefully mixing the collected materials. In the laboratory, lichen samples were cleaned from soil particles and submitted to seven consecutive washings with distilled water. Spherical bags 3-4 cm in diameter were assembled using nylon mesh (10 x 10 cm wide with 1 mm 2 meshes) and closed by nylon wire. Lichen thalli (400-450 mg) were placed in each bag. This amount exceeded 100-200 mg suggested as optimal by Gailey and Lloyd (1986) in order to assure enough material for chemical analysis.

Fig. 3.1 Ombrothermic diagrams for Kayseri (Halici et al. 2005). a meteorological station, b altitude, c observation (years), d average annual temperature (°C), e average annual precipitation (mm), f temperature, g precipitation, h dry season, i precipitation season, k frost months, m average minimum temperature (°C), n minimum temperature (°C), o maximum temperature (°C),p average maximum temperature (° C), r probable frost months

Fig. 3.1 Ombrothermic diagrams for Kayseri (Halici et al. 2005). a meteorological station, b altitude, c observation (years), d average annual temperature (°C), e average annual precipitation (mm), f temperature, g precipitation, h dry season, i precipitation season, k frost months, m average minimum temperature (°C), n minimum temperature (°C), o maximum temperature (°C),p average maximum temperature (° C), r probable frost months

120 n

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