Ammonia Measurement Techniques Ji-Qin (Jee-Chin) Ni, Ph.D. Dept. of Agricultural and Biological Engineering Purdue University October 21, 2008 Albuquerque, New Mexico

Why Measuring Ammonia Risk assessment Scientific research Pollution abatement Policy-making

Where Is Ammonia a Concern Animal barns Open feedlots Manure storages Manure treatment plants Manure application fields Farm neighboring area

Why Sampling Ammonia Very difficult to catch all the air for ammonia determination Reduce cost Increase efficiency

What Is Ammonia Sampling The technique or procedure that determines the location where the air sample is taken, controls the time (when, how long, how frequent) of measurement, and regulates the mass (volume) of air sample to be measured.

Sampling Location Animal & worker exposure: breathing zone Emission rate: background & exhausts Dispersion modeling: upwind, source, & downwind Dealing with spatial variations and depending on objective of measurement

Sampling Time Diel (diurnal) variations Seasonal variations Variations caused by ventilation or wind Dealing with temporal variations Example: NH 3 variations in a swine barn

Sampling Volume Important for wet chemistry, gas tubes, and other methods Not for optical open-path sampling Not always needed FTIR for ammonia measurement

Sampling Methods Sampling method ClosedPointOpen path ExposureExtraction LocalizedCentralized Passive, diffusion Active with pump

Closed: Sampling Chamber Other names: Lindvall box Dynamic chamber Convective flux chamber Wind tunnel Measuring chamber …

Single or Multi-Point Sampling Gas sampling probe

Multi-Point Extraction Sampling ` Loc# min A single set of equipment shared by different sampling locations

Open-Path Sampling Sampling at 1-dimensional path Path length: 75 – 500 m

Selection of Sampling Methods (1) Closed sampling Point samplingOpen-path sampling Cost EquipmentLowVery low for exposure method. Medium for localized extraction method. High for centralized extraction method. Medium to very high SetupMediumVery low to high for exposure and localized extraction methods. Very high for centralized extraction method. Low to medium

Selection of Sampling Methods (2) Closed samplingPoint samplingOpen-path sampling Study objective Treatment comparison and surface release. Animal and human exposure, baseline emission, treatment comparison, and dispersion modeling. Human ambient exposure, baseline emission, treatment comparison, and dispersion modeling.

Selection of Sampling Methods (3) Closed sampling Point samplingOpen-path sampling Technical aspect Size of sampling areaSmall release surface FlexibleLarge IntrusivenessIntrusiveLittle intrusiveNon-intrusive ControllabilityControllable for airflow at release surface Controllable for sampling flow Not controllable Source isolationVery goodGoodPoor Instrument sharingYesYes in centralized extraction method Yes for scanning system

Concentration and Emission

Selection of Measurement Devices

Wet Chemistry

pH Test Paper Add distilled water Wave in air Compare color Low cost: $0.05/test Low accuracy: ±5 ppm

Gas Detection Tubes Active tube (need a pump) Passive tube (does not need pump $5-10 per tube

Electrochemical Sensor Drager GasAlert Cost: $495

Chemiluminescence Analyzers Sensitive (1 ppb ±0.5ppb) Cost: ~$20k

Photoacoustic Infrared Monitor Multi-gas (up to 6) Cost: >$30k Innova Multi-gas monitor

Photo-acoustic Infrared Sensitive (1 ppm) Cost: ~$5k Maintenance: low Measurement range: ppm or ppm

Infrared Analyzer Model Rosemount 880A, Cost: ~$25k

Chemcassette Detection System Cost: ~$5000 Cassette: ~$50

Importance of Data Quality Data quality is critical to any research program. Erroneous data are worse than no data because bad data misleads scientific conclusions, regulatory decisions, abatement technique evaluations, and health risk assessments.

Bias and Precision

Quality Assurance Operation Measurement devices: Interferences Sensitivity Data processing Temporal variation Sampling: Devices & procedure Spatial variation Gases Procedure Calibration:

Errors: Calibration Gases Three NH 3 cylinders Two re-certified NH 3 cylinders How much can we trust?

Errors: Measurement Devices Three sensors 1. EC sensors 2. Active gas tubes 3. Passive gas tubes Example: (Wheeler et al. 2000) Performances - Lab: Good. - Chambers: Not good. - Layer houses: poor. Interferences Relative errors Absolute errors?

Methodology and Standards QAQC Methodology - Sampling & measurement devices - Comparison of devices - … Standards - Terminology - Sampling device & procedure - Measurement - Testing procedures - Calibration (gases)

Reference cited: Ni, J.-Q. and A. J. Heber Sampling and measurement of ammonia at animal facilities. Advances in Agronomy, vol. 98, Chapter 4. pp D.L. Sparks, ed. San Diego: Elsevier Academic Press Inc.