Checking organic carbon content.

Methods for checking water quality are an incredibly important part of the many processes involved in ensuring we have access to safe drinking water. However, as contaminants can come from many different sources, finding a general solution for contaminant identification and removal can be difficult.

Purification processes for water treatment include removal of undesirable chemicals, bacteria, solid waste and gases and can be very costly. Utility companies in England and Wales invested £2.1 billion (€2.44b) between 2013 and 2014 into infrastructure and assorted costs to ensure safe drinking water.¹

One of the most widely used measures for assessing whether water is safe for consumption or not is the analysis of the organic carbon (TOC) content. Dissolved organic carbon content is a measure of how much carbon is found in the water as part of organic compounds, as opposed to inorganic sources such as carbon dioxide and carbonic acid salts.²   It has been a popular approach since the 1970s for both assessment of drinking water and checking wastewater has been sufficiently purified.

The proportion of organic carbon in water is a good proxy for water quality as high organic carbon levels indicate a high level of organisms in the water or, contamination by organic compounds such as herbicides and insecticides. High levels of microorganisms can arise for a variety of reasons but are often a sign of contamination from a wastewater source.

Testing TOC
Water therefore needs to be continually monitored for signs of change in the TOC content to check it is safe for consumption. While many countries do not specifically regulate for TOC levels, the concentrations of specific volatile organic compounds are covered by legislation and recommended levels of TOC are 0.05 ml/l or less.³

There are a variety of approaches for testing water for organic carbon. One approach is to measure the entire carbon content (organic and inorganic) and then subtract any carbon dioxide detected (as it is considered inorganic carbon) and any other carbon from inorganic sources. Another is to use chemical oxidation or even high temperature so that all the organic compounds in the sample will be oxidized to carbon dioxide, and measuring the carbon dioxide levels, therefore, acts as a proxy for the TOC concentration.

For wastewater plants, being able to perform online, real-time analysis of water content is key and measurements must be sensitive and accurate enough to pick up small changes in even low concentrations of chemical species. British legislation also makes it an offense to supply drinking water which does not adhere to legislation⁴, with several water suppliers being fined over a hundred million pounds for recent discharges of contaminated waters.⁵

Vigilant Monitors
One of the advantages of using carbon dioxide levels as a proxy for TOC content is that carbon dioxide absorbs infrared light very strongly. This means using nondispersive infrared (NDIR) detectors provide a very sensitive way of detecting even trace amounts of carbon dioxide.

Edinburgh Sensors are one of the world leaders in NDIR sensor production and offer a range of NDIR-based gas detectors suitable for TOC measurements of water.⁶ Of these, for easy, quick and reliable TOC measurements, the Gascard NG is an excellent device for quantifying carbon dioxide levels.⁷

Gascard NG
The Gascard NG is well-suited to continual carbon dioxide monitoring for several reasons. First, the device is capable of detecting a wide range of carbon dioxide concentrations, from 0 – 5000 ppm, maintaining a ± 2 % accuracy over the full detection range. This is important so that the sensor has the sensitivity required for checking TOC levels are sufficiently low to be safe for drinking water but means it is also capable of operating under conditions where TOC levels may be very high, for example in the wastewater purification process.

As it can come with built-in true RS232 communications for both control and data logging, the Gascard NG can be used to constantly monitor carbon dioxide levels as well as be integrated into feedback systems, such as for water purification, to change treatment approaches if the TOC content gets too high. UK legislation also requires some level of record-keeping for water quality levels, which can also be automated in a straightforward way with the Gascard.4

The Gascard NG is capable of self-correcting measurements over a range of humidity conditions (0 – 95 %) and the readings can be pressure-corrected with on-board electronics between 800 to 1150 mbar. Temperature compensation is also featured between 0 to 45ºC to ensure reliable measurements, over a wide range of environmental conditions.

Designed to be robust, maintenance-free and fail-safe, the Gascard NG also comes with several customizable options. The expansion port can be used for small graphical display modules for in-situ observable readings and TCP/IP communications can also be included if it’s necessary to have communications over standard networks. In conjunction with Edinburgh Sensor’s expertise and pre- and post-sales support, this means that the Gascard NG can easily be integrated into existing TOC measurement systems to ensure fast and accurate monitoring at all times.

NOTES

1. Water and Treated Water (2019),
2. Volk, C., Wood, L., Johnson, B., Robinson, J., Zhu, H. W., & Kaplan, L. (2002). Monitoring dissolved organic carbon in surface and drinking waters. Journal of Environmental Monitoring, 4(1), 43–47.
3. DEFRA (2019)
4. Water Legislation (2019),
5. Water Companies Watchdog (2019)
6. Edinburgh Sensors (2019),
7. Gascard NG, (2019),

#Pauto @Edinst

Gas sensing in the purification process of drinking water.

The processing of clean and safe drinking water is an international issue. Estimates suggest that, if no further improvements are made to the availability of safe water sources, over 135 million people will die from potentially preventable diseases by 2020.¹

Even within Britain, water purification and treatment is big business, with £2.1 billion (€2.37b 28/8/2019) being invested by utilities in England and Wales between 2013 and 2014.² Water purification consists of removing undesirable chemicals, bacteria, solids and gases from water, so that it is safe to drink and use. The standard of purified water varies depending on the intended purpose of the water, for example, water used for fine chemical synthesis may need to be ‘cleaner’ i.e. have fewer chemicals present, than is tolerable for drinking water, the most common use of purified water.

Purification Process
The process of water purification involves many different steps. The first step, once the water has been piped to the purification plant, is filtering to remove any large debris and solids. There also needs to be an assessment of how dirty the water is to design the purification strategy. Some pretreatment may also occur using carbon dioxide to change pH levels and clean up the wastewater to some extent. Here, gas monitors are used to ensure the correct gas levels are being added to the water and unsafe levels of the gas do not build up.

The following steps include chemical treatment, an filtration to remove dissolved ionic compounds.³ Then, disinfection can occur to kill any remaining bacteria or viruses, with additional chemicals being added to provide longer lasting protection.⁴ At all stages, the water quality must be constantly monitored. This is to ensure that any pollutants have been adequately removed and the water is safe for its intended purpose.

In-line gas monitors are often used as part of the water treatment process as a way of monitoring total organic carbon (TOC) content. Carbon content in water can arise from a variety of sources, including bacteria, plastics or sediments that have not been successfully removed by the filtration process.⁵ TOC is a useful proxy for water cleanliness as it covers contamination from a variety of different sources.

To use non-dispersive infrared (NDIR) gas monitors to analyze the TOC content of water, a few extra chemical reactions and vaporization need to be performed to cause the release of CO2 gas. The resulting concentration of gas can then be used as a proxy of TOC levels.⁶ This then provides a metric than can be used to determine whether additional purification is required or that the water is safe for use.

Need for Gas Monitors
NDIR gas sensors can be used as both a safety device in the water purification process as carbon dioxide, methane, and carbon monoxide are some of the key gases produced during the treatment process. ⁵ The other key use is for analysis of TOC content as a way of checking for water purity.⁷ NDIR sensors are particularly well suited for TOC analysis as carbon dioxide absorbs infrared light very strongly. This means that even very low carbon dioxide concentrations can be detected easily, making it a highly sensitive measurement approach.⁶ Other hydrocarbon gases can also easily be detected in this way, making NDIR sensors a highly flexible, adaptable approach to monitoring TOC and dissolved gas content in water.

Sensor Solutions
The need for constant gas monitoring to guide and refine the purification process during wastewater treatment means water purification plants need permanent, easy to install sensors that are capable of continual online monitoring. One of the most effective ways of doing this is having OEM sensors that can be integrated into existing water testing equipment to also provide information on water purity.

These reasons are why Edinburgh Sensors range of nondispersive infrared (NDIR) gas sensors are the perfect solution for water purification plants. NDIR sensors are highly robust with excellent sensitivity and accuracy across a range of gas concentrations. Two of the sensors they offer, the Gascard NG⁸ and the Guardian NG⁹ are suitable for detecting carbon monoxide, carbon dioxide or other hydrocarbon gases. If just carbon dioxide is of interest, then Edinburgh Sensors offers are more extensive range of monitors, including the Gascheck¹⁰ and the IRgaskiT.¹¹

The advantage of NDIR detection for these gases are the device initial warm-up times are less than 1 minute, in the case of the Guardian NG. It is also capable of 0 – 100 % measurements such gases with a response time of less than 30 seconds from the sample inlet. The readout is ± 2 % accurate and all these sensors maintain this accuracy over even challenging environmental conditions of 0 – 95 % humidity, with self-compensating readout.

The Guardian NG comes with its own readout and menu display for ease of use and simply requires a reference gas and power supply to get running. For water purification purposes, the Gascard is particularly popular as the card-based device is easy to integrate into existing water testing equipment so testing of gases can occur while checking purity. .
Edinburgh Sensors also offers custom gas sensing solutions and their full technical support throughout the sales, installation and maintenance process.

References
1. Gleick, P. H. (2002). Dirty Water: Estimated Deaths from Water-Related Diseases 2000-2020 Pacific. Pacific Institute Researc Report, 1–12.

2. Water and Treated Water (2019), https://www.gov.uk/government/publications/water-and-treated-water/water-and-treated-water

3. Pangarkar, B. L., Deshmukh, S. K., Sapkal, V. S., & Sapkal, R. S. (2016). Review of membrane distillation process for water purification. Desalination and Water Treatment, 57(7), 2959–2981. https://doi.org/10.1080/19443994.2014.985728

4. Hijnen, W. A. M., Beerendonk, E. F., & Medema, G. J. (2006). Inactivation credit of UV radiation for viruses, bacteria and protozoan (oo)cysts in water: A review. Water Research, 40(1), 3–22. https://doi.org/10.1016/j.watres.2005.10.030

5. McCarty, P. L., & Smith, D. P. (1986). Anaerobic wastewater treatment. Environmental Science and Technology, 20(12), 1200–1206. https://doi.org/10.1021/es00154a002

6. Scott, J. P., & Ollis, D. F. (1995). Integration of chemical and biological oxidation processes for water treatment: Review and recommendations. Environmental Progress, 14(2), 88–103. https://doi.org/10.1002/ep.670140212

7. Florescu, D., Iordache, A. M., Costinel, D., Horj, E., Ionete, R. E., & Culea, M. (2013). Validation procedure for assessing the total organic carbon in water samples. Romanian Reports of Physics, 58(1–2), 211–219.

8. Gascard NG, (2019), https://edinburghsensors.com/products/oem/gascard-ng/

9. Guardian NG (2019) https://edinburghsensors.com/products/gas-monitors/guardian-ng/

10. Gascheck (2019), https://edinburghsensors.com/products/oem/gascheck/

11. IRgaskiT (2019), https://edinburghsensors.com/products/oem-co2-sensor/irgaskit/

12. Boxed GasCard (2019) https://edinburghsensors.com/products/oem/boxed-gascard/

 

#Pauto @Edinst

Quality fresh fruit and veg!

Creating Gaseous Micro Environments for Packaged Produce to Maintain the Quality of Fresh Fruits and Vegetables.

Food has often had a long and arduous journey before it reaches our plates. In the United States, it is estimated that food typically travels between 1500 and 2500 miles¹ between the farms where it is produced and the dinner table where it is ultimately consumed. What we think of as ‘fresh’ fruit and vegetables may also have been in storage or travelling for much longer than we think, potentially up to four weeks in the case of lettuce.²

Even for locally-sourced produced with reduced food miles, it is important for suppliers to ensure the maximum quality and freshness for their produce. This is because without careful storage for transportation, the vitamin content of fresh foods can deteriorate³ as well as the appearance of the produce, making it more difficult to sell to consumers.

One very successful approach to preserving food quality during transportation and storage is the use of gaseous microenvironments in food packaging and storage. This is known as modified atmospheric packaging (MAP), or atmospherically modified package (AMP), where the foods are packed in containers with an environment of carefully-controlled gas concentrations.⁴ A huge number of the foods we buy make use of MAP to enhance their freshness and shelf lives without the need to add preservatives or modify the food itself in any way.

A Fresh Environment
Transportation of fruit and vegetables is usually performed under refrigerated conditions, regardless of the means of transport, typically around 5°C with carefully controlled humidity.⁵The chilled conditions help to slow the growth of any microorganisms and extent the lifetime of the food, in conjunction with the use of MAP.

Despite the undoubted effectiveness of MAP in preserving produce quality⁶, optimal gas mixtures for MAP vary from produce to produce. For example, for most plant-based produce, some O₂ content in the atmosphere helps the plant to respire, but these needs to be balanced with increased CO₂ concentrations to slow the rate of respiration sufficiently to increase the produce lifetime.^{7, 8} However, there can be subtle differences between the optimum conditions for different types of fruit and vegetables, such as citric fruits which can only tolerate a lower limit of a 5 % O₂ concentration, unlike apples and pears that can cope with O₂ concentrations down to 1 %.⁹

Such careful control of the environmental conditions for optimum fruit and vegetable preservation during transportation relies then on highly-sensitive gas sensors capable of distinguishing the smallest of changes in gas concentration. The typical gases used in MAP for fresh fruit and vegetable preservation are CO₂, O₂ and sometimes N₂.

Precision for Freshness
Edinburgh Sensors offers a range of gas monitoring options well-suited to ensuring optimum gas conditions during fresh food transportation. Their range of CO₂ online monitoring sensors includes the Guardian NG¹⁰, Gascard NG¹¹, the IRgaskiT¹² and the Gascheck¹³, will cover most customer needs for food transport applications.

Where low-cost, highly-robust gas monitors are desirable, the Gascheck is an ideal option. Capable of detecting CO₂ concentrations in the 0-3000 ppm range, with a zero-stability of ± 3 % over 12-months and an accuracy of ± 3 % over the full detection range. Depending on the particular version of the Gascheck, the response time can be as low as 30 seconds, with an initial warm-up time of 5 minutes.

Where higher accuracy is desirable, the Guardian NG comes in a range of options with an accuracy of ± 2 %. The Guardian NG also has a convenient interface which displays true volume % readout over a wide range of pressures as well as being capable of displaying historical graphical information over a user-defined period. If necessary, there are built-in alarm systems to warn if gas concentrations deviate too much or the possibly to connect and interfacing with external logging devices.

The Gascard NG comes now in two versions, either as the stand-alone card, or as the Boxed Gascard¹⁴ to minimise installation and set-up time. The Gascard is capable of detecting CO₂ concentrations in the range of 0 – 5000 ppm and, like the other Edinburgh Sensors products, can also operate in humidity conditions spanning 0 – 95 %. By using RS232 communications the Gascard can be integrated with other control or data logging devices, also with the option for on-board LAN support where required.

Better Produce
Edinburgh Sensor’s full range of instruments comes with both pre- and post-sales technical support and these devices build on their nearly 40 years of expertise in a range of gas sensor technologies. Most of these products are based upon infra-red detection, which facilitates their very high sensitivities for gases such as CO₂ or other hydrocarbon species like methane and in systems like the Boxed Gascard, the infrared source is field-replaceable.

Online monitoring of gas concentrations for MAP applications allows maintenance of optimum conditions for fresh fruit and vegetable preservation, which is highly beneficial not just for ensuring better quality produce, but also ensuring less food spoilage and wastage and the cost-savings associated with this.

@edinsensors #Food

References

1. B. Halweil, Home Grown: The Case for Local Food in a Global Market, World Watch Institute, 2002
2. How old are the ‘fresh’ fruit and vegetables we eat, https://www.theguardian.com/lifeandstyle/2003/jul/13/foodanddrink.features18, (accessed February 2019)
3. M. I. Gil, F. Ferreres and F. A. Tomás-Barberán, J. Agric. Food Chem., 1999, 47, 2213–2217.
4. B. Ooraikul, Modified Atmosphere Packaging of Food, Springer, 1991
5. Packing Fresh Fruit and Vegetables, https://www.modifiedatmospherepackaging.com/~/media/Modifiedatmospherepackaging/Pictures/Guide%20%20%20Packaging%20of%20Fresh%20Fruit%20and%20Vegetables%20%20%20PDF%20file.ashx, (accessed February 2019)
6. E. M. Yahia , Modified and Controlled Atmospheres for the Storage, Transportation, and Packaging of Horticultural Commodities, Taylor and Francis Group, USA, 2009
7. Modified Atmospheric Packaging Poster, https://modifiedatmospherepackaging.com/~/media/Modifiedatmospherepackaging/Brochures/MAP-Poster-Guide-2014.ashx, (accessed February 2019)
8. S. Mangaraj and T. K. Goswami, Fresh Prod., 2009, 3, 1–33.
9. A. A. Kader, D. Zagory and E. L. Kerbel, Crit. Rev. Food Sci. Nutr., 1989, 28, 1–28.
10. Guardian NG, https://edinburghsensors.com/products/gas-monitors/guardian-ng/, (accessed February 2019)
11. Gascard NG, https://edinburghsensors.com/products/oem/gascard-ng/, (accessed February 2019)
12. IRgaskiT, https://edinburghsensors.com/products/oem/irgaskit/, (accessed February 2019)
13. Gascheck, https://edinburghsensors.com/products/oem/gascheck/, (accessed February 2019)
14. Boxed Gascard, https://edinburghsensors.com/products/oem/boxed-gascard/, (accessed February 2019)

Soil carbon flux research!

Measuring soil carbon flux gives an insight into the health of forest ecosystems and provides feedback on the effects of global warming. This article, from Edinburgh Instruments, outlines how soil CO₂ efflux is determined and the applications of soil carbon flux research.

Soil is an important part of the Earth’s carbon cycle.
Pic: pixabay.com/Picography

The Earth’s carbon cycle maintains a steady balance of carbon in the atmosphere that supports plant and animal life. In recent years, concerns about the increasing levels of CO₂ in the atmosphere, indicating a problem in Earth’s carbon cycle, has been a prominent global issue.^1,2

As a part of a stable carbon cycle, carbon is exchanged between carbon pools including the atmosphere, the ocean, the land and living things in a process known as carbon flux. Carbon exchange typically takes place as a result of a variety of natural processes including respiration, photosynthesis, and decomposition.

Since the industrial age, humans have begun to contribute to carbon exchange with activities such as fuel burning, and chemical processes, which are believed to be responsible for increasing atmospheric CO₂ concentrations and increasing global temperatures.^1-3

Soil carbon flux provides feedback on environmental conditions
Soil is a vital aspect of the Earth’s carbon cycle, containing almost three times more carbon than the Earth’s atmosphere. Carbon is present in soil as ‘solid organic carbon’ including decomposing plant and animal matter. Over time, microbial decomposition of the organic components of soil releases carbon into the atmosphere as CO₂.^4,5

The amount of carbon present in soil affects soil fertility, plant growth, microbial activity, and water quality. Studying the carbon flux of soil gives an insight into an ecosystem as a whole and specific information about microbial activity and plant growth.^4-6

Soil carbon flux can also help us to understand and predict the effects of global warming. As global temperatures increase, is it expected that microbial activity will also increase, resulting in faster plant decomposition and increased CO₂ efflux into the atmosphere.^5,6

Measuring soil CO₂ efflux
Determining soil-surface CO₂ efflux can be challenging. Researchers commonly employ a chamber combined with CO₂ concentration measurements to determine CO₂ efflux. A variety of chambers have been designed for such research, some of which are commercially available.^7-10

Closed-chamber systems typically pump air through a gas analyzer, which measures CO₂ concentration, before returning the air to the chamber. Soil CO₂ efflux is then estimated from the rate of increase of CO₂ concentration in the chamber.

Open-chambers pump ambient air into the chamber and measure the change in CO₂concentration between the air entering the chamber and the air leaving the chamber to determine the soil CO₂ efflux.

Of the two chamber types, open chambers are considered more accurate. Closed chambers tend to underestimate CO₂ efflux as increased CO₂ concentrations in the chamber cause less CO₂ to diffuse out of the soil while the chamber is in place.^10,11.

Often, CO₂ concentrations in chambers are measured periodically and then extrapolated to give an estimation of CO₂ efflux. This method can be inaccurate because CO₂ efflux can vary significantly between measurements with changes in environmental conditions.

A further limitation of using chambers for CO₂ efflux measurements is that chambers typically only provide measurements in one location, while CO₂ efflux has been found to vary widely even in relatively homogeneous environments. The overall result is CO₂ efflux data with limited temporal and spatial resolution, that does not reflect the environmental situation as a whole.^10,12,13

Naishen Liang

A group of researchers from the National Institute for Environmental Studies (Japan) led by Naishen Liang has designed an automated, multi-chamber chamber system for measuring soil-surface CO₂ efflux.

As CO₂ concentrations are measured automatically using an infrared gas sensor, CO₂ efflux can be determined accurately throughout the experiment. The improved temporal resolution, combined with increased spatial detail resulting from the use of multiple chambers gives a better overview of how CO₂ efflux varies with time, location, and environmental conditions within an ecosystem.¹⁰

Liang and his team have applied his method to gather information about a range of forest ecosystems. Their automated chambers have been used in a variety of forest locations combined with heat lamps to provide high-resolution, long-term data about the effects of warming on microbial activity and CO₂ efflux.

Liang’s research has shown that soil temperatures have a significant effect on CO₂ efflux in a wide range of forest environments, information that is vital for understanding how global warming will affect forest ecosystems and the Earth’s carbon cycle as a whole.^14-17

All chamber systems for determining CO₂ efflux rely on accurate CO₂ concentration analysis. Infrared gas analyzers are the most widely used method of instrumentation for determining CO₂ concentrations in soil CO₂ efflux measurement chambers.^8,10,18

Infrared gas sensors, such as gascard sensors from Edinburgh Sensors, are well suited to providing CO₂ concentration measurements in soil chambers, and are the sensors of choice used by Liang and his team.

The gascard sensors are robust, low-maintenance, and easy to use compared with other sensors. They provide rapid easy-to-interpret results and can be supplied as either complete boxed sensors (the Boxed Gascard) or as individual sensors (the Gascard NG) for easy integration into automated chambers.^19,20

---

Notes, References and further reading
1. ‘The Carbon Cycle’
2. ‘Global Carbon Cycle and Climate Change’ — Kondratyev KY, Krapivin VF, Varotsos CA, Springer Science & Business Media, 2003.
3. ‘Land Use and the Carbon Cycle: Advances in Integrated Science, Management, and Policy’ — Brown DG, Robinson DT, French NHF, Reed BC, Cambridge University Press, 2013.
4. ‘Soil organic matter and soil function – Review of the literature and underlying data’ — Murphy BW, Department of Environment and Energy, 2014
5. ‘The whole-soil carbon flux in response to warming’ — Hicks Pries CE, Castanha C, Porras RC, Torn MS, Science, 2017.
6. ‘Temperature-associated increases in the global soil respiration record’ — Bond-Lamberty B, Thomson A, Nature, 2010.
7. ‘Measuring Emissions from Soil and Water’ — Matson PA, Harriss RC, Blackwell Scientific Publications, 1995.
8. ‘Minimize artifacts and biases in chamber-based measurements of soil respiration’ — Davidson EA, Savage K, Verchot LV, Navarro R, Agricultural and Forest Meteorology, 2002.
9. ‘Methods of Soil Analysis: Part 1. Physical Methods, 3rd Edition’ — Dane JH, Topp GC, Soil Science Society of America, 2002.
10. ‘A multichannel automated chamber system for continuous measurement of forest soil CO2 efflux’ — Liang N, Inoue G, Fujinuma Y, Tree Physiology, 2003.
11. ‘A comparion of six methods for measuring soil-surface carbon dioxide fluxes’ — Norman JM, Kucharik CJ, Gower ST, Baldocchi DD, Grill PM, Rayment M, Savage K, Striegl RG, Journal of Geophysical Research, 1997.
12. ‘An automated chamber system for measuring soil respiration’ — McGinn SM, Akinremi OO, McLean HDJ, Ellert B, Canadian Journal of Soil Science, 1998.
13. ‘Temporal and spatial variation of soil CO2 efflux in a Canadian boreal forest’ — Rayment MB, Jarvis PG, Soil Biology & Biochemistry, 2000.
14. ‘High-resolution data on the impact of warming on soil CO2 efflux from an Asian monsoon forest’ — Liang N, Teramoto M, Takagi M, Zeng J, Scientific Data, 2017.
15. ‘Long‐Term Stimulatory Warming Effect on Soil Heterotrophic Respiration in a Cool‐Temperate Broad‐Leaved Deciduous Forest in Northern Japan’ —Teramoto M, Liang N, Ishida S, Zeng J, Journal of Geophysical Research: Biogeoscience, 2018.
16. ‘Sustained large stimulation of soil heterotrophic respiration rate and its temperature sensitivity by soil warming in a cool-temperate forested peatland’ — Aguilos M, Takagi K, Liang N, Watanabe Y, Teramoto M, Goto S, Takahashi Y, Mukai H, Sasa K, Tellus Series B : Chemical and Physical Meteorology, 2013.
17. ‘Liang Automatic Chamber (LAC) Network’
18. ‘Interpreting, measuring, and modeling soil respiration’ — Ryan MG, Law BE, Biogeochemistry, 2005.
19. ‘Boxed Gascard’
20. ‘Gascard NG’

@edinsensors #Environment #NIESJp

Methane detection in mines.

Mining is big business, with the world’s 50 largest mining companies worth a total of 1 trillion dollars (€0.81 trillion). Worldwide, the mining industry is responsible for the direct employment of 3.7 million people, with over 150 million indirectly supported by small-scale mining operations.  Many other sectors, such as high-tech industry, are also entirely dependent on mined supplies of materials.

Guardian NG detects methane

There is inherent danger in creating and operating within subterranean tunnels which results in a high mining date rate, over 5 deaths per day due to mining accidents recorded in China alone. This is a worldwide problem, with high-profile incidents in the last 10 years occurring in New Zealand, Russia and the US among others.

The most common source of mining accidents, particularly in coals mines, is an explosion of methane gas. Methane is a colourless, odourless gas which is trapped in mines as part of the coal formation process. As coal is formed from compressed plant matter methane is produced as a by-product then, when rocks are excavated, methane is released into the local atmosphere with potential deadly consequences.

Methane Explosions in Mines
Methane explosions in mines are the result of the concentration of a methane leak in a closed environment. If methane reaches a critical concentration in the air, which is between 5 to 15 % it can react with the oxygen to form carbon dioxide, water and heat. This reaction needs a source of ignition to begin. This doesn’t necessarily have to be an open flame, sparks from mining processes, or a high localised temperature (over 600 °C) on hot equipment, can be enough to cause an explosion.

The pressure wave created by a methane explosion is often more dangerous than the initial explosion. The waves can displace large amounts of coal dust, spreading highly flammable particles throughout the air. The dust can ignite as part of a chain reaction, spreading flames along the mining shaft, consuming any available oxygen to further fuel the fire and generating large amounts of toxic gases.

Safety Measures to Avoid Methane Explosions
Methane release is unavoidable in coal mines as it is always present. The problem with methane explosions is not just restricted to active mining sites either. Many abandoned also leak methane gas, potentially into residential areas where it can still reach high enough concentrations to be at risk of explosion.

The risk of methane gas accumulation in mines means that gas sensing is an essential part of any mining safety network. To reduce the risk of methane build up, ventilation equipment is used in mines to keep methane concentrations below the explosion limit.

Sensors can be placed at ventilation exits to mine, measuring the outgassing of methane to determine that the methane concentration in the mine itself is not close to critical methods. External sensors are also important to monitor the release of methane to the environment surrounding the mine.

In order for gas sensing to be an effective safety measure, the gas sensors used must be able to detect low methane concentrations at a high reliability.

The Guardian NG for Methane Detection
One sensor range that is suited to the critical safety issue of detecting methane outgassed from mines is the Guardian NG series from Edinburgh Sensors. Capable of detecting methane concentrations between 0-1%, these infra-red based sensors are sensitive enough to detect even the smallest of leaks.

The Guardian NG series is designed as an easy-to-use, standalone gas sensor that can continually monitor and log methane concentrations in conditions where the gas is present between 0 – 100 % volume, with the most sensitive sensor being able to detect between 0-1%. The sensor has an impressively rapid 1.5 minute warm-up time and is capable of operating in a range of conditions varying from 0 – 95 % relative humidity and 0 – 45 °C.

What makes the Guardian NG series particularly well-suited to mining applications is they can be easily integrated in to existing ventilation equipment. As the sensor itself is electronic and could generate sparks, it should be situated on the surface of the mine measuring gas concentrations released from the mine vents. This provides a guarantee that ventilation systems are working and can also be used to monitoring the off-gassing of old mining sites.

Infra-red sensors offer some advantages over the traditional heat of combustion sensors that are typically used for mining applications and are commonly used in other areas where methane detection is required as methane absorbs infra-red light very strongly at characteristic wavelengths. They also offer faster response times and potentially have longer service lives than heat of combustion sensor alternatives.

One huge advantage of IR sensors in safety applications is the fail-safe nature of the technology. If the IR lamp, and therefore the sensor, fails then no signal is received by the detector, which is an equivalent effect to the sensor detecting a high methane concentration. As a result, a full alarm would sound, notifying staff that the sensor has failed and there is a potentially dangerous situation.

With its sensitivity and accuracy for methane detection and short response time of less than 30 seconds from sample injection, the Guardian NG series offers one answer to the critical safety issue of explosion prevention in mining.

 

@Edinst #PAuto

Simulating the Effect of Climate Change on Agriculture.

Increased atmospheric CO₂ levels and climate change are believed to contribute to extreme weather conditions, which is a major concern for many. And beyond extreme events, global warming is also predicted to affect agriculture.^1,2

While climate change is expected to affect agriculture and reduce crop yields, the complete effects of climate change on agriculture and the resultant human food supplies are yet to be fully understood.^2,3,4

Simulating a Changing Climate
In order to understand how changes in CO₂, temperature and water availability caused by climate change have an impact on crop growth and food availability, Researchers often use controlled growth chambers to grow plants in conditions that mimic the predicted atmospheric conditions at the end of the century. These controlled growth chambers enable precise control of temperature, CO₂ levels, humidity, water availability, light quality and soil quality, allowing Scientists to study how plant growth changes in response to elevated temperatures, elevated CO₂ levels and altered water availability.

However, plant growth / behaviour in the field considerably varies from in growth chambers. Owing to differences in light intensity, light quality, evaporative demand, temperature fluctuations and other abiotic and biotic stress factors, the growth of plants in tiny, controlled growth chambers does not always sufficiently reflect plant growth in the field. Moreover, the less realistic the experimental conditions used during simulation experiments of climate change, the less likely the resultant predictions will reflect reality.⁴

Several attempts have been made over the past 30 years to more closely stimulate climate change growing scenarios including free air CO₂ enrichment, open top chambers, free air temperature increases and temperature gradient tunnels, although all these methods are known to have major disadvantages. For instance, chamber-less CO₂ exposure systems do not enable stringent control of gas concentrations, while other systems suffer from “chamber effects” such as changes in humidity, wind velocity, temperature, soil quality and light quality.^4,5

Spanish Researchers have recently reported temperature gradient greenhouses and growth chamber greenhouses, which are specifically designed to remove some of the disadvantages of simulating the effects of climate change on crop growth in growth chambers. An article reporting their methodology was featured in Plant Science in 2014, describing how the Researchers used temperature gradient greenhouses and growth chamber greenhouses to simulate climate change conditions and study plant responses.⁴

Choosing the Right Growth Chamber
Compared to traditional growth chambers, temperature gradient greenhouses and controlled growth chambers offer increased working area, allowing them to work as greenhouses without the necessity for isolation panels while still allowing precise control of various environmental factors such as temperature, CO₂ concentration and water availability.

Researchers have used these greenhouses to investigate the potential effects of climate change on the growth of grapevine, alfalfa and lettuce.

CO₂ Sensors for Climate Change Research
Researchers investigating the effects of climate change on plant growth using greenhouses or growth chambers will require highly accurate CO₂ measurements.

The Spanish Researchers used Edinburgh Sensors Guardian sensor in their greenhouses to provide accurate and reliable CO₂measurements. As a customer-focused provider of high-quality gas sensing solutions, Edinburgh Sensors has been delivering gas sensors to the research community since the 1980s.^4,6

The Guardian NG from Edinburgh Sensors
The Edinburgh Sensors Guardian NG provides precise CO₂ measurements in research greenhouses simulating climate change scenarios. The sensor provides near-analyser quality continuous measurement of CO₂ concentrations, operates in temperatures of 0-45 °C and relative humidity of 0-95%, and has a CO₂ detection range of 0 to 3000 ppm. These features make Guardian NG suitable for use in greenhouses with conditions meant to simulate climate change scenarios.

In addition, the Guardian NG can be easily installed as a stand-alone product in greenhouses to measure CO₂, or in tandem with CO₂ controllers as done by the Spanish Researchers in their temperature gradient and growth control greenhouses.^4,6

Conclusions
In order to understand the potential effects of climate change on plant growth and crop yields, it is important to simulate climate change scenarios in elevated CO₂ concentrations. For such studies, accurate CO₂ concentration measurements are very important.

References

• http://www.charlotteobserver.com/news/nation-world/article171632462.html (Accessed September 7^th, 2017.)
• Walthall CL, Hatfield J, Backlund P, et al. ‘Climate Change and Agriculture in the United States: Effects and Adaptation.’ USDA Technical Bulletin 1935, 2012. Available from: http://lib.dr.iastate.edu/cgi/viewcontent.cgi?article=1000&context=ge_at_reports  
• https://www.co2.earth/2100-projections  (Accessed September 7^th, 2017.)
• Morales F, Pascual I, Sánchez-Díaz M, Aguirreolea J, Irigoyen JJ, Goicoechea N Antolín MC, Oyarzun M, Urdiain A, ‘Methodological advances: Using greenhouses to simulate climate change scenarios’ Plant Science 226:30-40, 2014.
• Aguirreolea J, Irigoyen JJ, Perez P, Martinez-Carrasco R, Sánchez-Díaz M, ‘The use of temperature gradient tunnels for studying the combined effect of CO₂, temperature and water availability in N2 fixing alfalfa plants’ Annals of Applied Biology, 146:51-60, 2005.

@Edinst #agriculture

Simulating agricultural climate change scenarios.

Extreme weather, believed to result from climate change and increased atmospheric CO₂ levels, is a concern for many. And beyond extreme events, global warming is also expected to impact agriculture.(Charlotte Observer, 7 Sept 2017)

Although it is expected that climate change will significantly affect agriculture and cause decreases in crop yields, the full effects of climate change on agriculture and human food supplies are not yet understood. (1, 2 & 3 below)

Simulating a Changing Climate
To fully understand the effects that changes in temperature, CO₂, and water availability caused by climate change may have on crop growth and food availability, scientists often employ controlled growth chambers to grow plants in conditions that simulate the expected atmospheric conditions at the end of the century. Growth chambers enable precise control of CO₂ levels, temperature, water availability, humidity, soil quality and light quality, enabling researchers to study how plant growth changes in elevated CO₂ levels, elevated temperatures, and altered water availability.

However, plant behavior in the field often differs significantly from in growth chambers. Due to differences in light quality, light intensity, temperature fluctuations, evaporative demand, and other biotic and abiotic stress factors, the growth of plants in small, controlled growth chambers doesn’t always adequately reflect plant growth in the field and the less realistic the experimental conditions used during climate change simulation experiments, the less likely the resultant predictions will reflect reality.³

Over the past 30 years, there have been several attempts to more closely simulate climate change growing scenarios including open top chambers, free air CO₂ enrichment, temperature gradient tunnels and free air temperature increases, though each of these methods has significant drawbacks.

For example, chamber-less CO₂ exposure systems do not allow rigorous control of gas concentrations, while other systems suffer from “chamber effects” included changes in wind velocity, humidity, temperature, light quality and soil quality.^3,4

Recently, researchers in Spain have reported growth chamber greenhouses and temperature gradient greenhouses, designed to remove some of the disadvantages of simulating the effects of climate change on crop growth in growth chambers. A paper reporting their methodology was published in Plant Science in 2014 and describes how they used growth chamber greenhouses and temperature gradient greenhouses to simulate climate change scenarios and investigate plant responses.³

Choosing the Right Growth Chamber
Growth chamber and temperature gradient greenhouses offer increased working area compared with traditional growth chambers, enabling them to work as greenhouses without the need for isolation panels, while still enabling precise control of CO₂ concentration, temperature, water availability, and other environmental factors.

Such greenhouses have been used to study the potential effects of climate change on the growth of lettuce, alfalfa, and grapevine.

CO2 Sensors for Climate Change Research
For researchers to study the effects of climate change on plant growth using growth chambers or greenhouses, highly accurate CO2 measurements are required.

The Spanish team used the Edinburgh Sensors Guardian sensor in their greenhouses to provide precise, reliable CO2 measurements. Edinburg Sensors is a customer-focused provider of high-quality gas sensing solutions that have been providing gas sensors to the research community since the 1980s.^3,5

The Guardian NG from Edinburgh Sensors provides accurate CO₂ measurements in research greenhouses mimicking climate change scenarios. The Edinburgh Sensors Guardian NG provides near-analyzer quality continuous measurement of CO₂ concentrations. The CO₂ detection range is 0-3000 ppm, and the sensor can operate in 0-95% relative humidity and temperatures of 0-45 °C, making it ideal for use in greenhouses with conditions intended to mimic climate change scenarios.

Furthermore, the Guardian NG is easy to install as a stand-alone product in greenhouses to measure CO₂, or in combination with CO₂ controllers as done by the Spanish team in their growth control and temperature gradient greenhouses.^4,6 Conclusions Simulating climate change scenarios in with elevated CO₂ concentrations is essential for understanding the potential effects of climate change on plant growth and crop yields. Accurate CO₂ concentration measurements are essential for such studies, and the Edinburgh Sensors Guardian NG is an excellent option for researchers building research greenhouses for climate change simulation.

References

1. Walthall CL, Hatfield J, Backlund P, et al. ‘Climate Change and Agriculture in the United States: Effects and Adaptation.’ USDA Technical Bulletin 1935, 2012. Available from: http://lib.dr.iastate.edu/cgi/viewcontent.cgi?article=1000&context=ge_at_reports
2. https://www.co2.earth/2100-projections Accessed September 7th, 2017.
3. Morales F, Pascual I, Sánchez-Díaz M, Aguirreolea J, Irigoyen JJ, Goicoechea N Antolín MC, Oyarzun M, Urdiain A, ‘Methodological advances: Using greenhouses to simulate climate change scenarios’ Plant Science 226:30-40, 2014.
4. Aguirreolea J, Irigoyen JJ, Perez P, Martinez-Carrasco R, Sánchez-Díaz M, ‘The use of temperature gradient tunnels for studying the combined effect of CO2, temperature and water availability in N2 fixing alfalfa plants’ Annals of Applied Biology, 146:51-60, 2005.
5. https://edinburghsensors.com/products/gas-monitors/guardian-ng/ Accessed September 7th, 2017.

@Edinst #PAuto #Food

Measuring CO2 to optimise bulk storage of food.

Meeting the food requirements of a growing global population is becoming increasingly difficult. Despite the need for additional food, it is estimated that 50-60% of grain is lost after harvesting, at a cost of about $1 trillion per year. (See note 1 below)

One of the major reasons for lost grain is spoilage due to mould or insect infestation during storage.² To provide a constant supply of grain year-round, after grains are harvested they are often kept in long term storage. Maintaining the quality of stored grain is crucial, both to ensure the quality of the final food products, and to prevent economic losses for farmers.

Edinburgh Sensors GascardNG Sensor

Insects and moulds can grow in stored grain, and their ability to flourish depends on the temperature and moisture of the stored grain. Moulds are the most common cause of grain spoilage and can cause changes in the appearance and quality of stored grains. Some moulds can release toxic chemicals called mycotoxins which can suppress the immune system, reduce nutrient absorption, cause cancer, and even be lethal in high doses. It is therefore crucially important to prevent the presence of mycotoxins in food products.²

Monitoring Stored Grain
Farmers are advised to check their stored grain weekly for signs of spoilage.³ Traditionally, grains are checked visually and by odour. Grain sampling can allow earlier detection of insects and moulds, but these methods can be tedious and time-consuming. Rapid, simple methods are needed for early detection of spoilage and to prevent grain losses.²

When moulds and insects grow, and respire, they produce CO₂, moisture and heat. Temperature sensors detect increases in temperature caused by mould growth or insect infestation, therefore indicating the presence of grain spoilage. However, they are not able to detect temperature increases caused by infestation unless the infestation is within a few meters of the sensors. CO₂ sensors can detect the CO₂ produced by moulds and insects during respiration. As the CO₂ gas moves with air currents, CO₂ sensors can detect infestations that are located further away from the sensor than temperature sensors. CO₂ measurements are therefore an important part of the toolkit needed to monitor stored grain quality.²

Using CO₂ Measurements to Detect Spoilage
CO₂ monitoring can be used for early detection of spoilage in stored grains, and to monitor the quality of stored grains. Safe grain storage usually results in CO₂ concentrations below 600 ppm, while concentrations of 600-1500 ppm indicate the onset of mould growth. CO₂ concentrations above 1500 ppm indicate severe infestations and could represent the presence of mycotoxins.⁴

CO₂ measurements can be taken easily, quickly and can detect infestations 3-5 weeks earlier than temperature monitoring. Once spoilage is detected, the manager of the storage facility can address the problem by aerating, turning, or selling the grain. Furthermore, CO₂ measurements can aid in deciding which storage structure should be unloaded first.²

Research published by Purdue University and Kansas State University have confirmed that high CO₂ levels detected by stationary and portable devices are associated with high levels of spoilage and the presence of mycotoxins.^4,5 Furthermore, they compared the ability of temperature sensors and CO2 sensors in a storage unit filled with grain to detect the presence of a simulated ‘hot spot’ created using a water drip to encourage mould growth.

The CO₂ concentration in the headspace of the storage unit showed a strong correlation with the temperature at the core of the hot spot, and the CO₂ sensors were, therefore, able to detect biological activity. The temperature sensors were not able to detect the mould growth, despite being placed within 0.3-1 m of the hotspot.⁶

To enable efficient monitoring of grain spoilage accurate, reliable and simple to use CO₂ detectors are required. Gascard NG Gas Detector from Edinburgh Sensors provide accurate CO₂ measurements along with atmospheric data, enabling grain storage managers to make decisions with confidence.

The Gascard NG Gas Detector uses a proprietary dual wavelength infrared sensor to enable the long term, reliable measurement of CO₂ over a wide range of concentrations and in temperatures ranging from 0-45 °C. Measurements are unaffected by humidity (0-95% relative humidity) and the onboard pressure and temperature sensors provide real-time environmental compensation, resulting in the most accurate CO2 concentration readings.

Conclusion
Easy, fast, and accurate CO₂ concentration monitoring during grain storage can provide early detection of grain spoilage, resulting in reduced grain losses, higher quality stored grain, and lower mycotoxin levels. CO₂ monitoring could save millions of dollars annually in the grain production industry.⁴

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References

1. Kumar D, Kalita P, Reducing Postharvest Losses during Storage of Grain Crops to Strengthen Food Security in Developing Countries. Foods 6(1):8, 2017.
2. http://www.world-grain.com/Departments/Grain-Operations/2016/7/Monitoring-CO2-in-stored-grain.aspx?cck=1 Accessed May 25th, 2017.
3. HGCA Grain storage guide for cereals and oilseeds, third edition, available from: https://cereals.ahdb.org.uk/media/490264/g52-grain-storage-guide-3rd-edition.pdf Accessed May 25th, 2017.
4. Maier DE, Channaiah LH, Martinez-Kawas, A, Lawrence JS, Chaves EV, Coradi PC, Fromme GA, Monitoring carbon dioxide concentration for early detection of spoilage in stored grain. Proceedings of the 10th International Working Conference on Stored Product Protection, 425, 2010.
5. Maier DE, Hulasare R, Qian B, Armstrong P, Monitoring carbon dioxide levels for early detection of spoilage and pests in stored grain. Proceedings of the 9th International Working Conference on Stored Product Protection PS10-6160, 2006.
6. Ileleji KE, Maier DE, Bhat C, Woloshuk CP, Detection of a Developing Hot Spot in Stored Corn with a CO2 Sensor. Applied Engineering in Agriculture 22(2):275-289, 2006.