LI-7820 N2O/H2O Trace Gas Analyzer

The LI-7820 N2O/H2O Trace Gas Analyzer offers high-precision nitrous oxide measurements in a low power, portable design—enabling it to easily integrate into survey and long-term soil flux systems. Pair it with the LI-7810 CH4/CO2/H2O Trace Gas Analyzer or LI-870 CO2/H2O Analyzer for CO2 and CH4 measurements at your site.

A combination of several patented technologies with Optical Feedback-Cavity Enhanced Absorption Spectroscopy (OF-CEAS) results in precise and stable N2O measurements, for chamber-based soil flux research.

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Measuring N2O and Other Trace Gases in Soil and Air Using LI-COR Trace Gas Analyzers

From soil flux measurements of N2O and CH4, to point-source detection systems, LI-COR Trace Gas Analyzers are the new standard for portable, precise gas measurements.

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LI-7820 Advantages

  • Connect to the Smart Chamber or the LI-8250 Multiplexer for collecting, processing and viewing N2O fluxes on site or remotely
  • Functions with a low power, weatherized design that operates on hot-swappable, 8-hour batteries
  • Deploys long term with minimum infrastructure requirements (e.g., simple cover or stand) to create a user-friendly solution for lab and field measurements
  • Connects to a smartphone via Wi-Fi-enabled communications to monitor and view live data without a field computer and works with SoilFluxPro™ Software for dataset management

For details on the design and technology used in the LI-7820, visit the Trace Gas Analyzers page.

LI-7820 Trace Gas Analyzer

Measuring N2O fluxes in soil

Designed for soil flux measurements, the LI-7820 N2O/H2O Trace Gas Analyzer brings the precision you need to measure both natural variation in fluxes and large flux events, even in remote areas. With the ability to resolve fluxes quickly, you can take more measurements throughout the day and quickly visualize those fluxes with SoilFluxPro™ Software.

Figure 1. Measurements of N2O flux from soils over a 14-month time period. Measured by the LI-7820 N2O/H2O Trace Gas Analyzer and an LI-8100A Automated Soil CO2 Flux System. Measurements were conducted over an urban lawn in Lincoln, NE, USA, and shows natural variations of N2O fluxes detected by the LI-7820. Results from Xu, et al., 2020.

Figure 2. Soil N2O flux measurements with the LI-7820. The precision of the LI-7820 allows fluxes to be resolved within 2 minutes, for both high fluxes (linear regression coefficients higher than 0.9 when N2O flux was higher than 0.1 nmol m-2 s-1, figures A and B), as well as when fluxes from natural emissions occur that can be extremely low. The LI-7820 is capable of measuring flux rates as low as 0.05 nmol m-2 s-1 in 2 minutes under these conditions (C).

N2O flux measurements from soil are often minimal and close to zero. Natural variation still occurs, however, and is important to quantify. A highly precise analyzer that can quickly resolve small fluxes is essential for detecting minute, natural variations in soil N2O flux. The LI-7820 allows you to take precise measurements of these slight variations and to resolve natural N2O fluxes in addition to measuring large fluxes, such as changes that occur after a fertilizer treatment.

The example given is from a LI-COR long-term soil flux system. The LI-7820 was used to measure larger fluxes emitted during spring thaw events in Lincoln, Nebraska, while also recording smaller natural fluxes. Figure 2 provides an example flux calculated in 2 minutes from a closed-chamber measurement.

LI-7820 Specifications

General

  • Measurement Technique: OF-CEAS (Optical Feedback – Cavity Enhanced Absorption Spectroscopy)
  • Measurement Rate: 1 sample per second (1 Hz)
  • Optical Cavity Volume: 6.41 cm3
  • Flow Rate:
    • 250 sccm nominally in Standard Configuration
    • 150 sccm nominally in High Altitude Configuration
    • 70 sccm nominally in Reduced Flow Rate Configuration with installed kit
  • Total Weight: 10.5 kg (including batteries)
  • Case Dimensions: 51 cm × 33 cm × 18 cm (L × W × H)
  • Operating Temperature Range: -25 °C to 45 °C (without solar load, under normal operating conditions)
  • Operating Humidity Range: 0 to 85% RH (non-condensing, without solar load, under normal operating conditions)
  • Sample Line Humidity Range: 0 to 99.9% non-condensing
  • Operating Pressure Range:
    • 70 to 110 kPa in Standard and Reduced Flow Rate Configurations
    • 50 to 110 kPa in High Altitude Configuration
  • Connectivity: Ethernet and Wi-Fi (not available in some countries)
  • Wi-Fi Compatibility: 2.4 GHz, 802.11 a/b/g/n/ac
  • Power Consumption:
    • Steady State Operation: 22 Watts at 25 °C without batteries charging
    • Warmup: Up to 65 W without batteries charging; up to 100 W with batteries charging
    • Off: Up to 2.3 W when powered from pins 3 and 4 without batteries charging; up to 0.2 W when powered from pins 1 and 5 without batteries charging
  • Power Supply Requirements:
    • Pins 1 and 5 (24 VDC Input): Minimum 6 A at 24 V
    • Pins 3 and 4 (10.5 to 33 VDC Input): Minimum 14 A at 10.5 VDC; 6 A at 24 VDC
  • Power Supply: Universal Power Adapter (Input: 100 to 240 VAC, 50-60 Hz; Output: 24 VDC)
  • Battery Life: 8 hours typical with 2 batteries
  • Pollution Degree: 2
  • Over-voltage Category: II
  • Class 1 Laser Product

N2O Measurements

  • Response Time (T10-T90): all from 0 to 330 ppb
    • ≤ 2 seconds in Standard Configuration
    • ≤ 3 seconds in High Altitude Configuration
  • Range: 0 to 100 ppm
  • Precision (1σ):
    • 0.40 ppb at 330 ppb with 1 second averaging
    • 0.20 ppb at 330 ppb with 5 second averaging
  • Maximum Drift: < 1 ppb per 24-hour period

H2O Measurements

  • Range: 0 to 60,000 ppm
  • Precision (1σ):
    • 45 ppm at 10,000 ppm with 1 second averaging
    • 20 ppm at 10,000 ppm with 5 second averaging

Specifications subject to change without notice.

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