AMBIENT AIR MONITORING – ppt video online download

Presentation on theme: “AMBIENT AIR MONITORING”— Presentation transcript:

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AMBIENT AIR MONITORING
Objectives and Monitoring Devices Frank Murray Murdoch University, Perth, Australia

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Content of this presentation
Monitoring objectives Advantages and disadvantages of different types of instrumentation Quality assurance and quality control

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Planning and design considerations
Objectives of the monitoring program Resource availability Spatial and temporal coverage Performance specifications of the monitoring devices (precision, accuracy, and response time)

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Monitoring Objectives
To provide the data required for rational air quality management

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Monitoring Objectives
Activate air pollution alert Assess accuracy of air quality models Assess impacts of air pollution on health and the environment Assess accumulation of persistent pollutants

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Monitoring Objectives
Inform the public through reporting Assess need for pollution control at current emission levels future emission levels Assess effectiveness of pollution control Assess compliance with regulations

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Why measure indoor air pollution
To determine Level of exposures Distribution of exposure Demographics of exposure To evaluate if interventions achieved the objectives To relate indoor air quality to health outcomes

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The importance of objective-setting
Define and Documented Monitoring Objectives Efficient Resource Utilisation Effective Quality Assurance (QAP) Optimal Network Design enable Definition of Appropriate Date Quality Objectives (DQOs)

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Which Air Pollutants? Most commonly: suspended particulate matter, PM10, PM2.5, Pb, SO2, NO2, NO, O3, CO, non-methane hydrocarbons, HF, other heavy metals, benzene, polycyclic aromatic hydrocarbons, and other air toxics.

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Sampling intervals Grab samples Integrated sampling (averaging)
Continuous (provides peak information)

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When to measure? When cooking Morning to evening 24 hr 48 hr 7 day
Different seasons

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Samplers Passive samplers – very cheap, no services needed, used for surveys, remote uses Active samplers – worldwide most widely used, cheap, simple, long averaging times, accuracy ? Biological accumulation (eg accumulation in plants, soil)

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Passive Samplers – Advantages
Simple and inexpensive Can provide large scale simultaneous measurements of concentrations at many locations for long time periods, eg surveys No need for electricity Standardised production and measurement from one well equipped laboratory

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Canisters for sampling indoor air

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Passive Samplers – Disadvantages
ACCURACY – less accurate than other samplers and analysers, but good for an overview of an area

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Active Samplers – Advantages
Relatively cheap Technically simple and sustainable Moderately accurate – more accurate than passive samplers Established technology Shorter averaging times than passive samplers

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Active sampler for particulates

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Active samplers for water soluble gases

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High volume RSP and TSP samplers

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Solar radiation detector
Wind anemometer tapered element oscillating microbalance – continuous RSP Acid rain collector

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Active Samplers – Disadvantages
Require electricity Require careful maintenance and analytical procedures for satisfactory results

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Analysers Automatic analysers – real-time, short averaging times, complex, provide excellent data if well-operated Interactive monitoring/modelling (eg Airtrak)

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TEOM Ambient Particulate Monitor
Schematic diagram of the TEOM Ambient Particulate Monitor

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result is not a gravimetric
Photometer: DustTrak FEATURES Cheaper, simple, Mass size selection: PM1, PM2.5 and PM10 real time results result is not a gravimetric mass, needs calibration

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Gaseous pollutants analyzer
Mobile air sampler

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Continuous methods of air pollutant measurement
TECHNIQUE RESPONSE TIME DETECTION LIMIT SO2 H2O2/conductivity Flame photometric Pulsed fluorescence 3 min 25 sec 2 min 10 ppbv 0.5 ppbv NO Chemiluminescence with O3 1 sec NO2 Reduction / Chemiluminescence O3 KI oxidation / electrolysis Chemiluminescence UV spectroscopy 1 min 3 sec 30 sec 1 ppbv 3 ppbv CO Electrochemical Non-dispersive infrared 5 sec 1 ppmv 0.5 ppmv Hydrocarbons Flame ionisation 0.5 sec

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Analysers – Disadvantages
Expensive to purchase and service Can be technically difficult to maintain – spare parts and service not always available May require sophisticated infrastructure

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Remote Sensing Multiple pollutant automatic analysis, remote sensing (eg Opsis) Automated analysis – real-time instant data, short averaging times, very visible, provide excellent data if well-operated

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Remote sensors

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Remote Sensing – Disadvantages
Extremely expensive to purchase and service Technically difficult to calibrate and maintain – spare parts and service not always available Require sophisticated infrastructure Data may not be fully comparable with other techniques

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Instrumented Air Monitoring Techniques
METHOD ADVANTAGES DISADVANTAGES CAPITAL COST Passive Samplers Very low cost Very simple Useful for screening and baseline studies Unproven for some pollutants Often only provides monthly and weekly averages $2 – 4 per sample Active Samplers Low cost Easy to operate Reliable performance Historical dataset Provide daily averages Labour intensive Laboratory analysis required $2 – 4K per unit Automatic Analysers Proven High performance Hourly data On-line information and low direct costs Complex and expensive High skill required High recurrent costs $ K per analyser Remote Sensors Provide path or range-resolved data Useful near sources and vertical measurements in the atmosphere Multi-component measurements Very complex and expensive Difficult to support, operate, calibrate and validate Not always comparable with conventional analysers > $200K per sensor

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Bio-indicators Bioindication methods include use of:
Surface of plants as receptors of air pollutants Plant capacity for accumulating some air pollutants over a period of time Estimation of the effects of air pollutants on plant metabolism, growth, appearance, or marketable products Surveys of the distribution of effects on plants as indicators of air quality in a region, or resolve compensation claims

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QA/QC for Air Monitoring: A step-by-step approach
International Requirements Local/National Requirements Define Monitoring Objectives Assess Resource Availability Network design, site numbers and location Instrument Selection Site Operation, Support and Calibration Data Review and Usage Periodic System Review

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Conclusions Be clear about the objectives of monitoring, preferably in writing Define data quality objectives Choose monitoring methods and instrumentation suitable to achieve the objectives Ensure quality control and quality assurance These are especially important in monitoring of controversial projects subject to close public scrutiny