**1. Introduction**

218 Environmental Monitoring

McGarigal, K., and Marks, E.J., (1995). FRAGSTATS: Spatial pattern analysis program for

Morgan, J., Gergel, S., and Coops, N., (2010). Aerial Photography: A Rapidly Evolving Tool

NIJOS, (2001). Norwegian 3Q Monitoring Program: Norwegian institute of land inventory. O'Neill, R.V., Krumme, J.R., Gardner, H.R., Sugihara, G., Jackson, B., DeAngelist, D.L.,

Ramezani, H., (2010). Deriving landscape metrics from sample data (PhD thesis): Umeå,

Ramezani, H., and Holm, S., (2011a). A distance dependent contagion functions for vector-

—, (2011b). Estimating a distance dependent contagion function using point sample data (in

—, (2011c). Sample based estimation of landscape metrics: accuracy of line intersect

Ramezani, H., Holm, S., Allard, A., and Ståhl, G., (2010). Monitoring landscape metrics by

Ries, L., Fletcher, R.J., Battin, J., and Sisk, T.D., (2004). Ecological responses to habitat edges:

Riitters, K.H., O'Neill, R.V., Hunsaker, C.T., Wickham, J.D., Yankee, D.H., Timmins, S.P.,

Saura, S., and Martinez-Millan, J., (2001). Sensitivity of landscape pattern metrics to map

Ståhl, G., Allard, A., Esseen, P.-A., Glimskär, A., Ringvall, A., Svensson, J., Sture Sundquist,

Traub, B., and Kleinn, C., (1999). Measuring fragmentation and structural diversity:

Wickham, J.D., Riitters, K.H., ONeill, R.V., Jones, K.B., and Wade, T.G., (1996). Landscape

Wulder, M.A., White, J.C., Hay, G.J., and Castilla, G., (2008). Towards automated

sampling for estimating edge density and Shannon's diversity . Environmental and

point sampling: accuracy in estimating Shannon's diversity and edge density:

Mechanisms, models, and variability explained: Annual Review of Ecology

Jones, K.B., and Jackson, B.L., (1995). A factor-analysis of landscape pattern and

spatial extent: Photogrammetric Engineering and Remote Sensing, v. 67, p. 1027-

S., Christensen, P., Gallegos Torell , Å., Högström, M., Lagerqvist, K., Marklund, L., Nilsson, B., and Inghe, O., (2011). National Inventory of Landscapes in Sweden (NILS) - Scope, design, and experiences from establishing a multi-scale biodiversity monitoring system: Environmental Monitoring and Assessment v. 173, p. 579-595. Takács, G., and Molnár, Z., (2009) National biodiversity monitoring system XI. Habitat

mapping (2nd modified ed., p. 54). Ministry of Environment and Water, Budapest.

'contagion' in raster and vector environments: International Journal of

segmentation of forest inventory polygons on high spatial resolution satellite

based data: Environmental and Ecological Statistics (accepted).

Environmental Monitoring and Assessment v. 164, p. 403-421.

Agriculture, Forest Service, Pacific Northwest Research Station.

for Ecological Management: BioScience, v. 60, p. 47-59.

Raj, D., (1968). *Sampling theory*: New York, McGraw-Hill, 302pp. p.

Ecological Statistics, v. 18, p. 109-130.

Evolution and Systematics, v. 35, p. 491-522.

structure metrics: Landscape Ecology, v. 10, p. 23-39.

Forstwissenschaftliches Centralblatt, v. 118, p. 39-50.

Geographical Information Systems, v. 10, p. 891-899.

imagery: Forestry Chronicle, v. 84, p. 221-230.

review).

1036.

Swedish University of Agricultural Sciences (SLU).

quantifying landscape pattern. General Technical Report 351. U.S. Department of

Milne, B.T., Turner, M., Zygmunt, B., Christensen, S.W., Dale, V.H., and Graham, L.R., (1988). Indices of landscape pattern: Landscape Ecology v. 1, p. 153-162.

> Volatile Organic Compounds (VOCs) are largely used in many industries as solvents or chemical intermediates. Unfortunately, they include some components, present in the atmosphere, that can represent a risk factor for human health. They are also present as a contaminant or a by-product in many processes, i.e. in combustion gas stacks and groundwater clean-up systems.

> Benzene, in particular, shows a high toxicity resulting in a Time-Weighted Average (TWA) limit of 0.5 ppm, as compared, for instance, with TWA for gasoline, in the range of 300 ppm.

> Detection of VOCs at sub-ppm levels is, thus, of paramount importance for human safety and industrial hygiene in hazardous environments.

> The commonly used field-portable instruments for VOC detection are the hand-held Photo-Ionisation Detectors (PIDs), sometime using pre-filter tubes for specific gas detection. PIDs are accurate to sub-ppm, measurements are fast, in the range of one or two minutes and, thus, compatible with on-field operation. However, they require skilled personnel and cannot provide continuous monitoring.

> Wireless connected hand-held PID Detectors start being available on the market, thus overcoming some of the previously described limitations, but suffering for the limited battery life and relatively high cost.

> The paper describes the implementation and on-field results of an end-to-end distributed monitoring system integrating VOC detectors, capable of performing real-time analysis of gas concentration in hazardous sites at unprecedented time/space scale.

> The system consists of a Wireless Sensor Network (WSN) infrastructure, whose nodes are equipped with distributed meteo-climatic sensors and gas detectors, of TCP/IP over GPRS Gateways forwarding data via Internet to a remote server and of a user interface which provides data rendering in various formats and access to data.

> The paper provides a survey of the VOC detector technologies of interest, of the state-of-theart of the fixed and area wireless technologies available for Gas detection in hazardous areas and a detailed description of the WSN based monitoring system.

Real-Time Monitoring of Volatile Organic Compounds in Hazardous Sites 221

 It's very important to prevent and reduce pollutant emissions at source, implementing the best effective reduction measures, both technological and on management. Emissions of air pollutant should be reduced by each member state according to World

 The directive establishes the need of a strong monitoring system and the reciprocal exchange of information and data from networks and individual stations measuring ambient air pollution in order to incorporate the latest health and scientific

 Each Member State should ensure consistency and representativeness of the information collected on air pollution; standardised measurement techniques and

Alternative measurement methods may provide indicative results that could be less accurate than those made with the reference method. Indicative measurement techniques based on the use of automatic sensors, mobile laboratories, portable analysers and manual methods of measurement, such as diffusive sampling techniques, are very interesting due to the relatively low cost and simplicity of operation compared with instrumental and

Volatile Organic Compounds are defined as all compounds containing organic carbon characterized by low vapour pressure at ambient temperature. They are present in the

The number of volatile organic compounds observed in the atmosphere, both in urban and remote areas, is extremely high and includes, in addition to hydrocarbons (compounds containing only carbon and hydrogen), also oxygen species such as ketones, aldehydes, alcohols, acids and esters. Natural emissions of VOCs include the direct emissions from vegetation and the degradation of organic matter; anthropogenic emissions are mainly caused by the incomplete combustion of hydrocarbons, the evaporation of solvents and fuels, and processing industries. On a global scale, natural and anthropogenic emissions of

A lot of volatile organic compounds are highly toxic; this makes them extremely dangerous to human health. In addition, many compounds react with nitrogen oxides and other substances, contributing to the formation of ozone in the lower atmosphere, with impact on climate change and pollution issues (i.e. photochemical smog). Finally, some substances are characterized by a very low odour threshold, resulting in complaints from population and

There are many classification systems, based on chemical characteristics, or based on the impact on the environment and human health. The term VOC covers several groups of

common criteria for the number and location of measuring stations are defined. For assessing air quality, information and data collected from fixed measurement stations may be integrated with data from alternative techniques, such as modelling or indicative measurements. The use of measurement methods other than standardised methods allows improving data monitoring and interpretation in some critical areas

(such as, for instance, industrial sites) in an economical and feasible way.

Health Organisation guidelines.

operative costs of fixed measuring stations.

**3. Volatile Organic Compounds** 

atmosphere mainly in the gas phase.

VOCs are of the same order of magnitude.

community living around industrial sites.

**4. VOC classification** 

developments and the experience of the Community.
