High frequency monitoring needed to protect UK rivers!

29/06/2018
Nigel Grimsley from OTT Hydrometry describes relatively new technologies that have overcome traditional barriers to the continuous monitoring of phosphate and nitrate.

The science behind nutrient pollution in rivers is still poorly understood despite the fact that nitrate and phosphate concentrations in Britain’s rivers are mostly unacceptable, although an element of uncertainty exists about what an acceptable level actually is. Key to improving our understanding of the sources and impacts of nutrient pollution is high-resolution monitoring across a broad spectrum of river types.

Background

Green Box Hydro Cycle

Phosphates and nitrates occur naturally in the environment, and are essential nutrients that support the growth of aquatic organisms. However, water resources are under constant pressure from both point and diffuse sources of nutrients. Under certain conditions, such as warm, sunny weather and slow moving water, elevated nutrient concentrations can promote the growth of nuisance phytoplankton causing algal blooms (eurtrophication). These blooms can dramatically affect aquatic ecology in a number of ways. High densities of algal biomass within the water column, or, in extreme cases, blankets of algae on the water surface, prevent light from reaching submerged plants. Also, some algae, and the bacteria that feed on decaying algae, produce toxins. In combination, these two effects can lower dissolved oxygen levels and potentially kill fish and other organisms. In consequence, aquatic ecology is damaged and the water becomes unsuitable for human recreation and more expensive to treat for drinking purposes.

In its State of the Environment report, February 2018, the British Environment Agency said: “Unacceptable levels of phosphorus in over half of English rivers, usually due to sewage effluent and pollution from farm land, chokes wildlife as algal blooms use up their oxygen. Groundwater quality is currently deteriorating. This vital source of drinking water is often heavily polluted with nitrates, mainly from agriculture.”

Good ecological status
The EU Water Framework Directive (WFD) requires Britain to achieve ‘good status’ of all water bodies (including rivers, streams, lakes, estuaries, coastal waters and groundwater) by 2015. However, only 36% of water bodies were classified as ‘good’ or better in 2012. Nutrient water quality standards are set by the Department for Environment, Food & Rural Affairs (DEFRA), so for example, phosphorus water quality standards have been set, and vary according to the alkalinity and height above mean sea level of the river. Interestingly, the standards were initially set in 2009, but in 75% of rivers with clear ecological impacts of nutrient enrichment, the existing standards produced phosphorus classifications of good or even high status, so the phosphorus standards were lowered.

Highlighting the need for better understanding of the relationships between nutrients and ecological status, Dr Mike Bowes from the Centre for Ecology & Hydrology has published research, with others, in which the effects of varying soluble reactive phosphate (SRP) concentrations on periphyton growth rate (mixture of algae and microbes that typically cover submerged surfaces) where determined in 9 different rivers from around Britain. In all of these experiments, significantly increasing SRP concentrations in the river water for sustained periods (usually c. 9 days) did not increase periphyton growth rate or biomass. This indicates that in most rivers, phosphorus concentrations are in excess, and therefore the process of eutrophication (typified by excessive algal blooms and loss of macrophytes – aquatic plants) is not necessarily caused by intermittent increases in SRP.

Clearly, more research is necessary to more fully understand the effects of nutrient enrichment, and the causes of algal blooms.

Upstream challenge
Headwater streams represent more than 70% of the streams and rivers in Britain, however, because of their number, location and the lack of regulatory requirement for continuous monitoring, headwater streams are rarely monitored for nutrient status. Traditional monitoring of upland streams has relied on either manual sampling or the collection of samples from automatic samplers. Nevertheless, research has shown that upland streams are less impaired by nutrient pollution than lowland rivers, but because of their size and limited dilution capacity they are more susceptible to nutrient impairment.

References
• Bowes, M. J., Gozzard, E., Johnson, A. C., Scarlett, P. M., Roberts, C., Read, D. S., et al. (2012a). Spatial and temporal changes in chlorophyll-a concentrations in the River Thames basin, UK: are phosphorus concentrations beginning to limit phytoplankton biomass? Sci. Total Environ. 426, 45–55. doi: 10.1016/j.scitotenv. 2012.02.056
• Bowes, M. J., Ings, N. L., McCall, S. J., Warwick, A., Barrett, C., Wickham, H. D., et al. (2012b). Nutrient and light limitation of periphyton in the River Thames: implications for catchment management. Sci. Total Environ. 434, 201–212. doi: 10.1016/j.scitotenv.2011.09.082
• Dodds, W. K., Smith, V. H., and Lohman, K. (2002). Nitrogen and phosphorus relationships to benthic algal biomass in temperate streams. Can. J. Fish. Aquat Sci. 59, 865–874. doi: 10.1139/f02-063
• McCall, S. J., Bowes, M. J., Warnaars, T. A., Hale, M. S., Smith, J. T., Warwick, A., et al. (2014). Impacts of phosphorus and nitrogen enrichment on periphyton accrual in the River Rede, Northumberland, UK. Inland Waters 4, 121–132. doi: 10.5268/IW-4.2.692
• McCall, S. J., Hale, M. S., Smith, J. T., Read, D. S., and Bowes, M. J. (2017). Impacts of phosphorus concentration and light intensity on river periphyton biomass and community structure. Hydrobiologia 792, 315–330. doi: 10.1007/s10750-016-3067-1

Monitoring technology
Sampling for laboratory analysis can be a costly and time-consuming activity, particularly at upland streams in remote locations with difficult access. In addition, spot sampling reveals nutrient levels at a specific moment in time, and therefore risks missing concentration spikes. Continuous monitoring is therefore generally preferred, but in the past this has been difficult to achieve with the technology available because of its requirement for frequent re-calibration and mains power.

High resolution SRP monitoring has been made possible in almost any location with the launch by OTT Hydromet of the the ‘HydroCycle PO4’ which is a battery-powered wet chemistry analyser for the continuous analysis of SRP. Typically, the HydroCycle PO4 is deployed into the river for monitoring purposes, but recent work by the Environment Agency has deployed it in a flow-through chamber for measuring extracted water.

The HydroCycle PO4 methodology is based on US EPA standard methods, employing pre-mixed, colour coded cartridges for simple reagent replacement in the field. Weighing less than 8kg fully loaded with reagents, it is quick and easy to deploy, even in remote locations. The instrument has an internal data logger with 1 GB capacity, and in combination with telemetry, it provides operators with near real-time access to monitoring data for SRP.

The quality of the instrument’s data is underpinned by QA/QC processing in conjunction with an on-board NIST standard, delivering scientifically defensible results. Engineered to take measurements at high oxygen saturation, and with a large surface area filter for enhanced performance during sediment events, the instrument employs advanced fluidics, that are resistant to the bubbles that can plague wet chemistry sensors.

Environment Agency application
The National Laboratory Service Instrumentation team (NLSI) provides support to all high resolution water quality monitoring activities undertaken across the Agency, underpinning the EA’s statutory responsibilities such as the WFD, the Urban Waste Water Directive and Statutory Surface Water Monitoring Programmes. It also makes a significant contribution to partnership projects such as Demonstration Test Catchments and Catchments Sensitive Farming. Technical Lead Matt Loewenthal says: “We provide the Agency and commercial clients with monitoring systems and associated equipment to meet their precise needs. This includes, of course, nutrient monitoring, which is a major interest for everyone involved with water resources.”

Matt’s team has developed water quality monitoring systems that deliver high resolution remote monitoring with equipment that is quick and easy to deploy. There are two main options. The ‘green box’ is a fully instrumented cabinet that can be installed adjacent to a water resource, drawing water and passing it though a flow-through container with sensors for parameters such as Temperature Dissolved Oxygen, Ammonium, Turbidity, Conductivity pH and Chlorophyll a. Each system is fitted with telemetry so that real-time data is made instantly available to users on the cloud.

Conscious of the need to better understand the role of P in rivers, Matt’s team has integrated a HydroCycle PO4 into its monitoring systems as a development project.
Matt says: “It’s currently the only system that can be integrated with all of our remote monitoring systems. Because it’s portable, and runs on 12 volts, it has been relatively easy to integrate into our modular monitoring and telemetry systems.

“The HydroCycle PO4 measures SRP so if we need to monitor other forms of P, we will use an auto sampler or deploy a mains-powered monitor. However, monitoring SRP is important because this is the form of P that is most readily available to algae and plants.”

Explaining the advantages of high resolution P monitoring, Matt refers to a deployment on the River Dore. “The data shows background levels of 300 µg P/l, rising to 600 µg P/l following heavy rain, indicating high levels of P in run-off.”

Nitrate
Similar to phosphates, excessive nitrate levels can have a significant impact on water quality. In addition, nitrates are highly mobile and can contaminate groundwater, with serious consequences for wells and drinking water treatment. Nitrate concentrations are therefore of major interest to the EA, but traditional monitoring technology has proved inadequate for long-term monitoring because of a frequent recalibration requirement. To address this need, which exists globally, OTT Hydromet developed the SUNA V2, which is an optical nitrate sensor, providing high levels of accuracy and precision in both freshwater and seawater.

The NLSI has evaluated the SUNA V2 in well water and Matt says: “It performed well – we took grab samples for laboratory analysis and the SUNA data matched the lab data perfectly. We are therefore excited about the opportunity this presents to measure nitrate continuously, because this will inform our understanding of nitrate pollution and its sources, as well as the relationship between groundwater and surface water.”

Summary
The new capability for high-resolution monitoring of nutrients such as phosphorus will enable improved understanding of its effects on ecological status, and in turn will inform decisions on what acceptable P concentrations will be for individual rivers. This is vitally important because the cost of removing P from wastewater can be high, so the requirements and discharge limits that are placed on industrial and wastewater companies need to be science based and supported by reliable data. Similarly, nitrate pollution from fertilizer runoff, industrial activities and wastewater discharge, has been difficult to monitor effectively in the past because of the technology limitations. So, as improved monitoring equipment is developed, it will be possible to better understand the sources and effects, and thereby implement effective prevention and mitigation strategies.

@OTTHydrometry @EnvAgency @CEHScienceNews #Water #Environment

Researchers investigate ultra-low Mediterranean nutrient levels.

25/04/2018

Researchers at Haifa University’s Marine Biological Station in Israel are exploiting the ultra-low detection limits of advanced laboratory equipment to measure extremely low nutrient concentrations in marine water.

H.Nativ – Morris Kahn Marine Research Station

The University’s Prof. M. D. Krom says: “We work in the Eastern Mediterranean which has the lowest regional concentration of dissolved nutrients anywhere in the global ocean. We therefore utilize an automated segmented flow analyzer from SEAL Analytical, which has been specially adapted to accommodate ultra-low measurements.”

The SEAL AutoAnalyzer 3 (AA3) is a 4 channel system, measuring Phosphate with a long flow cell which has a detection limit of 2 nM. Ammonia is measured using a JASCO fluorometer with a similar ultra-low detection limit, and Silicate, which has a higher concentration, is measured using SEAL’s high resolution colorimetric technology.

The measurement data are being used to determine the season nutrient cycling in the system, which will then be used to help understand the nature of the food web and the effects of global environmental and climate change.

Low nutrient levels in the Mediterranean
The eastern Mediterranean Sea (EMS) has an almost unique water circulation. The surface waters (0-200m) flow into the Mediterranean through the Straits of Gibraltar and from there into the EMS at the Straits of Sicily. As the water flows towards the east it becomes increasingly saline and hence denser. When it reaches the coast of Turkey in winter it also cools and then flows back out of the Mediterranean under the surface waters to Sicily, and then eventually through the Straits of Gibraltar to the North Atlantic. This outflowing layer exists between 200m and 500m depth.

Phytoplankton grow in the surface waters (0-200m) because that is the only layer with sufficient light. This layer receives nutrients from the adjacent land, from rivers and wastewater discharges, and also from aerosols in the atmosphere. These nutrients are utilized by the plankton as they photosynthesize. When the plants die (or are eaten) their remains drop into the lower layer and are jetted out of the EMS. Because the water flows are so fast (it takes just 8 years for the entire surface layers of the EMS to be replaced), these nutrient rich intermediate waters rapidly expel nutrients from the basin. The result is very low nutrient concentrations and very low numbers of phytoplankton – some of the lowest values anywhere in the world. Prof. Krom says: “The maximum levels of nutrients measured in the EMS are 250 nM phosphate, 6 uM nitrate and 6-12 uM silicate. Ammonia is often in the low nanomolar range. By contrast, in the North Atlantic, values are 1000 nM phosphate, 16 uM nitrate and 20 uM silicate, and the levels in the North Pacific are even higher.”

The value of data
The low levels of plankton caused by low nutrient levels, result in a low biomass of fish. Nevertheless, coastal areas generally support more fish than offshore, so the research will seek to quantify and understand the nutrient cycle in the coastal regions, which is poorly understood at present. “We plan to develop understandings which will inform stakeholders such as government. For example, there is a discussion about the potential for fish farms off the Israeli coast, so our work will enable science-based decisions regarding the quantity of fish that the system can support.”

To-date, three data sets have been taken from the EMS, and the first publishable paper is in the process of being prepared.

Choosing the right analyzer
Prof. Krom says that his first ‘real’ job was working for the (then) Water Research Centre at Medmenham in Britain, where he was involved in the development of chemical applications for the Technicon AA-II autoanalyzers, which included going on secondment to Technicon for several months. SEAL Analytical now own and manufacture the AutoAnalyzer brand of Continuous Segmented Flow Analyzers, so his career has been connected with autoanalyzers for decades. For example his is Professor (Emeritus) at the University of Leeds (GB), where, again, he worked with SEAL autanalyzers. An AA3 instrument was employed at Leeds in a project to investigate the nature of atmospheric acid processing of mineral dusts in supplying bioavailable phosphorus to the oceans.

Explaining the reasoning behind the purchase of a new AA3 at Haifa University, Prof. Krom says: “During a research cruise, it is necessary to analyse samples within a day to avoid changes in concentration due to preservation procedures.

“Typically we analyse 50-80 samples per day, so it is useful to useful to be able to analyze large numbers of samples automatically. However, the main reasons for choosing the SEAL AA3 were the precision, accuracy and low limits of detection that it provides.”

Commenting on this application for SEAL’s analyzers, company President Stuart Smith says: “Many of our customers analyze nutrient levels in freshwater and marine water samples, where high levels of nutrients are a concern because of increasing levels of algal blooms and eutrophication. However, Prof. Krom’s work is very interesting because, in contrast, he is looking at extremely low levels, so it is very gratifying that our instruments are able to operate at both ends of the nutrient concentration spectrum.

Bibliography
• Powley, H.R., Krom, M.D., and Van Cappellen, P. (2017) Understanding the unique biogeochemistry of the Mediterranean Sea: Insights from a coupled phosphorus and nitrogen model. Global Biogeochemical Cycles, 11; 1010-1031. DOI 10.1002/2017GB005648.

• Stockdale, A. Krom, M. D., Mortimer, R.J.G., Benning, L.G., Carslaw, K.S., Herbert, R.J., Shi, Z., Myriokefalitakis, S., Kanakidou, M., and Nenes, A., (2016) Understanding the nature of atmospheric acid processing of mineral dusts in supplying bioavailable phosphorus to the oceans. PNAS vol. 113 no. 51

#SealAnal #Marine @_Enviro_News

Train derailment prompts contaminated land investigation.

11/01/2018

A train derailment in Mississippi resulted in ground contamination by large quantities of hazardous chemicals, and environmental investigators have deployed sophisticated on-site analytical technology to determine the extent of the problem and to help formulate an effective remediation strategy. Here Jim Cornish from Gasmet Technologies discusses this investigation.

Jim Cornish

On March 30th 2015 a long freight train, transporting a variety of goods including lumber and chemicals, wound its way through the state of Mississippi (USA). At around 5pm, part of the train failed to negotiate a curved portion of the track in a rural area near Minter City, resulting in the derailment of nine railcars, one of which leaked chemicals onto agricultural farmland and woodlands. Emergency response and initial remediation activities were undertaken, but the remainder of this article will describe an environmental investigation that was subsequently conducted by Hazclean Environmental Consultants using a portable multiparameter FTIR gas analyzer from Gasmet Technologies.

Background
Over 17,000 gallons of Resin Oil Heavies were released from the railcar, and the main constituent of this material is dicyclopentadiene (DCPD). However, in addition to DCPD, Resin Oil Heavies also contains a cocktail of other hydrocarbons including ethylbenzene, indene, naphthalene, alpha-methyl styrene, styrene, vinyl toluene, 1, 2, 3-trimenthylbenzene, 1, 2, 4-trimethylbenzene, 1, 3, 5-trimethylbenzene and xylenes.

DCPD is highly flammable and harmful if swallowed and by inhalation. Its camphor-like odor may induce headaches and symptoms of nausea, and as a liquid or vapor, DCPD can be irritating to the eyes, skin, nose, throat or respiratory system. DCPD is not listed as a carcinogen, however DCPD products may contain benzene, which is listed as a human carcinogen. DCPD is not inherently biodegradable, and is toxic to aquatic organisms with the potential to bioaccumulate.

It is a colorless, waxy, flammable solid or liquid, used in many products, ranging from high quality optical lenses through to flame retardants for plastics and hot melt adhesives. As a chemical intermediate it is used in insecticides, as a hardener and dryer in linseed and soybean oil, and in the production of elastomers, metallocenes, resins, varnishes, and paints. DCPD-containing products are also used in the production of hydrocarbon resins and unsaturated polyester resins.

Emergency Response
Emergency response phase activities were performed from March 31 through May 2, 2015. Response objectives and goals were formally documented by utilizing Incident Action Plans for each operational period. Activities between April 11 and April 28, 2015 were summarized in weekly reports and submitted to the Mississippi Department of Environmental Quality (MDEQ) and the Environmental Protection Agency (EPA).

Approximately 10,189 gallons of the leaked product was recovered, leaving 5,458 gallons to contaminate the farmland surface and subsurface soil, surface waters, groundwater and ambient air. The site contamination problem was exacerbated due to heavy rainfall and associated stormwater runoff which caused the unrecovered product to migrate from the spill site.

Taking account of the high rainfalls levels that followed the event, it was calculated that contaminated stormwater runoff from the immediate project site (10 acres with 8.7 inches of rainfall) was 2,362,485 gallons less that retained by emergency retention berms. Approximately 207,000 gallons of contaminated stormwater were collected during the emergency response, in addition to approximately 7,870 tons of impacted material which were excavated for disposal. Following removal of the gross impacted material, the site was transferred into Operation and Maintenance status, conducted in accordance with a plan approved by MDEQ.

Ongoing site contamination
Groundwater and soil samples were collected and analyzed in 2015 and 2016, producing analytical data which confirmed that widespread soil and groundwater contamination still existed at the site. Further remediation was undertaken, but the landowners were extremely concerned about the fate of residual chemicals and contracted Hazclean Environmental Consultants to conduct a further investigation.

“The affected land is used for agricultural purposes, producing crops such as soybeans and corn,” says Hazclean President, E. Corbin McGriff, Ph.D., P.E. “Consequently, there were fears that agricultural productivity would be adversely affected and that chemicals of concern might enter the food chain.
“This situation was exacerbated by the fact that the landowners could still smell the contamination and initial investigation with PID gas detectors indicated the presence of volatile organic compounds (VOCs).”

Hazclean’s Joseph Drapala, CIH, managed and conducted much of the site investigation work. He says: “While PID gas detectors are useful indicators of organic gases, they do not offer the opportunity to quantify or speciate different compounds, so we spoke with Jeremy Sheppard, the local representative of Gasmet Technologies, a manufacturer of portable FTIR (Fourier Transform Infrared) gas analyzers.

Soil Vapor Analysis with FTIR

“Jeremy explained the capabilities of a portable, battery-powered version of the Gasmet FTIR gas analyzer, the DX4040, which is able to analyze up to 25 gases simultaneously, producing both qualitative and quantitative measurements. Gasmet was therefore contacted to determine whether this instrument would be suitable for the Mississippi train spill application.

“In response, Gasmet confirmed that the DX4040 would be capable of measuring the target species and offered to create a specific calibration so that these compounds could be analyzed simultaneously on-site.”

Site investigation with FTIR analysis
A sampling zone was defined to capture potential contamination, and measurements were taken for surface and subsurface soil, groundwater, and surface and subsurface air for a range of VOCs.

Vapor Well

The area-wide plan resulted in the installation of four permanent monitoring wells for groundwater sampling, twenty vapor monitoring wells, and twenty test borings for field screening. The test borings indicated the presence of VOCs which were further characterized by sampling specific soil sections extracted from the parent core.

In addition to the almost instantaneous, simultaneous measurement of the target compounds, the Gasmet DX4040 stores sample spectra, so that post-measurement analyses can be undertaken on a PC running Gasmet’s Calcmet™ Pro software, providing analytical capability from a library of 250 compounds. “The Gasmet DX4040 was manufacturer-calibrated for dicyclopentadiene, benzene, ethylbenzene, naphthalene, styrene, toluene, 1,2,3-trimenthylbenzene, 1,2,4-trimethylbenzene, 1,3,5-trimethylbenzene and m, o, and p and total xylenes at a detection range of 0.01 ppm to 100 ppm in air,” Joseph reports, adding: “The ability to compare recorded spectra with the Calcmet Pro library is a major advantage because it enables the measurement of unknown compounds.”

The operating procedures for the DX4040 indicate a simple, convenient requirement for daily calibration with zero gas prior to each monitoring activity. However, in addition to the use of nitrogen as the zero gas, Joseph also employed specialty gas (DCPD) certified for 1 ppm and 5 ppm as a calibration check and a response (akin to bump testing) gas.

Site screening
The test borings provided soil samples that were vapor-tested on-site as part of the screening process. Vapor from the extracted soil samples was analyzed by placing the soil samples in vessels at ambient temperature and connecting the DX4040 in a closed loop from the vessel, so that air samples could be continually pumped from the vessel to the analyzer and returned to the vessel. This screening activity helped to determine the location for vapor wells.

All soil samples were screened with the DX4040 and those with the highest reading from each boring were sent for laboratory analysis.

Vapor wells were fitted with slotted PVC liners and capped. Before monitoring, the cap was replaced with a cap containing two ports to enable the DX4040 to be connected in a similar closed-loop monitoring system to that which was employed for the soil samples.

Conclusions
As a result of this investigation it was possible for Hazclean to determine that the release of DCPD in the vapor state, as measured in the vapor monitor wells, is a result of surface and subsurface contamination in the soil and groundwater, and that this contamination will remain in the future.

Vapor analysis data provided by the DX4040 identified DCPD, benzene, styrene and xylene previously adsorbed on soil and/or wetted surfaces undergoing diffusion and evaporation. The adsorption, diffusion and evaporation of DCPD et al. released and spread across the farmland is a mechanism to explain the vapor concentrations found in vapor monitor wells as well as the ambient malodor problem.

The long term release of DCPD and other VOCs will continue to occur in the impact area unless a larger remediation project is conducted to remove soil and groundwater contamination. Furthermore, Hazclean recommends that, as a result of the effectiveness of the Gasmet DX4040 in this investigation, the same technology should be employed in any subsequent screening activities, using the same Gasmet calibration configuration.

Summarizing, Joseph Drapala says: “The Gasmet DX4040 was an essential tool in this investigation. Screening activities should have the ability to detect and identify the target compounds, as well as any secondary compounds that may have already been present on-site or could have been produced as a result of chemical interactions.
“As an FTIR gas analyzer, the DX4040 meets these requirements, providing enormous analytical capability through Gasmet’s Calcmet software. However, the instrument is also small, lightweight and battery powered which makes it ideal for field investigations.”


Measuring CO2 to optimise bulk storage of food.

24/07/2017

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


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.

 


The ‘ins and outs’ of air quality monitoring!

20/02/2017
The British National Institute for Health and Care Excellence (NICE) recently issued draft guidance on ‘Air pollution – outdoor air quality and health.’ 

Here, Jim Mills, Managing Director of Air Monitors Ltd, explains why there will need to be more funding for monitoring if the mitigation measures mentioned in the guidance are to be implemented effectively. Jim also highlights the close relationship between outdoor air quality and the (often ignored) problems with indoor air quality.

The NICE guidelines are being developed for Local Authority staff working in: transport, planning, air quality management and public health. The guidance is also relevant for staff in healthcare, employers, education professionals and the general public.

Covering road-traffic-related air pollution and its links to ill health, the guidelines aim to improve air quality and so prevent a range of health conditions and deaths. Unfortunately, on the day that the draft guideline was published, most of the national media focused on one relatively minor recommendation relating to speed bumps. ‘Where physical measures are needed to reduce speed, such as humps and bumps, ensure they are designed to minimise sharp decelerations and consequent accelerations.’ Measures to encourage ‘smooth driving’ are outlined; however, the guidelines also address a wide range of other issues, which, in combination, would help tackle urban air pollution.

Public sector transport services should implement measures to reduce emissions, but this is an area that could involve the greatest financial cost.

Many local authorities would doubtless comment that they are already implementing many of the guideline recommendations, but refer to budgetary constraints on issues that involve upfront costs. This issue was raised on BBC Radio 4 when the issue was discussed on 1st December.

AQMesh Pod

AQMesh Pod

The NICE guidelines recommend the inclusion of air quality issues in new developments to ensure that facilities such as schools, nurseries and retirement homes are located in areas where pollution levels will be low. LAs are also urged to consider ways to mitigate road-traffic-related air pollution and consider using the Community Infrastructure Levy for air quality monitoring. There are also calls for information on air quality to be made more readily available.

LAs are also being urged to consider introducing clean air zones including progressive targets to reduce pollutant levels below the EU limits, and where traffic congestion contributes to poor air quality, consideration should be given to a congestion charging zone. The guidelines also highlight the importance of monitoring to measure the effects of these initiatives.

As part of the consultation process, NICE is looking for evidence of successful measures and specifically rules out “studies which rely exclusively on modelling.”

In summary, all of the initiatives referred to in the NICE report necessitate monitoring in order to be able to measure their effectiveness. However, most LAs do not currently possess the monitoring capability to do so. This is because localised monitoring would be necessary before and after the implementation of any initiative. Such monitoring would need to be continuous, accurate and web-enabled so that air pollution can be monitored in real-time. AQMesh is therefore the ideal solution; small, lightweight, quick and easy to install, these air quality monitors are able to monitor all the main pollutants, including particulates, simultaneously, delivering accurate data wirelessly via the internet.

Whilst AQMesh ‘pods’ are very significantly lower in cost both to buy and to run than traditional reference stations, they still represent a ‘new’ cost. However any additional costs are trivial in comparison with the costs associated with the adverse health effects caused by poor air quality, as evidenced in the recent report from the Royal College of Physicians.

Inside Out or Outside In?

Fidas® Frog

Fidas® Frog

The effects of air pollution are finally becoming better known, but almost all of the publicity focuses on outdoor air pollution. In contrast, indoor air quality is rarely in the media, except following occasional cases of Carbon Monoxide poisoning or when ‘worker lethargy’ or ‘sick building syndrome’ are addressed. However, it is important to understand the relationship between outdoor air quality and indoor air quality. Air Monitors is currently involved in a number of projects in which air quality monitoring is being undertaken both outside and inside large buildings, and the results have been extremely interesting.

Poorly ventilated offices tend to suffer from increased Carbon Dioxide as the working day progresses, leading to worker lethargy. In many cases HVAC systems bring in ‘fresh’ air to address this issue, but if that fresh air is in a town or city, it is likely to be polluted – possibly from particulates if it is not sufficiently filtered and most likely from Nitrogen Dioxide. Ventilating with outdoor air from street level is most likely to bring air pollution into the office, so many inlets are located at roof level. However, data from recent studies indicate that the height of the best air quality can vary according to the weather conditions, so it is necessary to utilise a ‘smart’ system that monitors air quality at different levels outside the building, whilst also monitoring at a variety of locations inside the building. Real-time data from a smart monitoring network then informs the HVAC control system, which should have the ability to draw air from different inlets if available and to decide on ventilation rates depending on the prevailing air quality at the inlets. This allows the optimisation of the internal CO2, temperature and humidity whilst minimising the amount of external pollutants brought into the indoor space. In circumstances where the outside air may be too polluted to be used to ventilate, it can be pre-cleaned by scrubbing the pollutant gases in the air handling system before being introduced inside the building.

Fidas200The implementation of smart monitoring and control systems for buildings is now possible thanks to advances in communications and monitoring technology. AQMesh pods can be quickly and easily installed at various heights outside buildings and further units can be deployed internally; all feeding near-live data to a central control system.

Another example of indoor air quality monitoring instrumentation developing from outdoor technology is the ‘Fidas Frog,’ a new fine dust aerosol spectrometer developed by the German company Palas. The Frog is an indoor, wireless, battery-powered version of the hugely popular, TÜV and MCERTS certified Fidas 200. Both instruments provide simultaneous determination of PM fractions, particle number and particle size distribution, including the particle size ranges PM1, PM2.5, PM4, PM10 and TSP.

Evidence of outdoor air pollution contaminating indoor air can be obtained with the latest Black Carbon monitors that can distinguish between the different optical signatures of combustion sources such as diesel, biomass, and tobacco. The new microAeth® MA200 for example, is a compact, real-time, wearable (400g) Black Carbon monitor with built-in pump, flow control, data storage, and battery with onboard GPS and satellite time synchronisation. Samples are collected on an internal filter tape and wireless communications are provided for network or smartphone app integration and connection to other wireless sensors. The MA200 is able to monitor continuously for 2-3 weeks. Alternatively, with a greater battery capacity, the MA300 is able to provide 3-12 months of continuous measurements.

In summary, a complete picture of indoor air quality can be delivered by a combination of AQMesh for gases, the Palas Frog for particulates and the microAeth instruments for Black Carbon. All of these instruments are compact, battery-powered, and operate wirelessly, but most importantly, they provide both air quality data AND information on the likely source of any contamination, so that the indoor effects of outdoor pollution can be attributed correctly.

@airmonitors #Environment #PAuto @_Enviro_News


Analyzer underpins growth of container inspection company.

10/02/2017

After a career as a customs officer in the Netherlands, Wim van Tienen was well aware of the toxic gas hazards presented by some freight containers, so in 2009 he started a company, Van Tienen Milieuadvies B.V., offering gas analysis and safety advice. The company grew quickly and now employs 23 staff. Wim attributes a large part of this success to the advanced FTIR gas detection and analysis technology upon which the company’s services depend.

Background

Wim van Tienen

Wim van Tienen

It has been estimated that there are more than 17 million shipping containers in the world, and at any time about one third of them are on ships, trucks, and trains. Over a single year, the total number of container trips has been estimated to be around 200 million.

The air quality inside containers varies enormously, depending on the goods, the packing materials, transit time, temperature, humidity and the possible presence of fumigants. Consequently, many containers contain dangerous levels of toxic gases and represent a major threat to port and transport workers, customs officials, warehousemen, store employees and consumers. It is therefore essential that risks are assessed effectively before entry is permitted.

Solvent vapours and most fumigants, whilst harmful, can be detected by the human nose, but Wim says: “Some gases are odourless and some have a high odour detection threshold, which means that you can only smell the substance in high concentrations; ethylene oxide for example, is commonly used as a sterilant in relation to medical devices. It is extremely toxic and has a low TLV limit of 0,5 ppm. However the odour threshold limit of ethylene oxide is 500 ppm, so detection with instrumentation is essential.”

The wide variety of potential contaminants represents a technological challenge to those responsible for testing, because if testers seek to detect specific gases, they risk failing to detect other compounds. It is also not practical to test every single container, so logical procedures must be established in order to minimise risks.

Gas Detection and Measurement
In 2009, when Wim first established the company, container gas detection was carried out with traditional field measurement techniques (gas detection sensors and tubes). “This approach was complicated, costly and time-consuming, and it was impossible to cover all risks,” he says. “With sensors and tubes, only a limited number of compounds can be measured specifically. Furthermore, the accuracy of detection tubes is poor and they can suffer from cross-sensitive reactions by interfering substances.

“Technologies such as PID-detectors respond to a wide variety of organic compounds, but they are not selective and unable to detect commonly found substances with high ionisation potentials such as 1,2-dichloroethane and formaldehyde.” Wim does not, therefore, believe that traditional measurement techniques are the best approach for covering all risks. “In order to test for the most common gases, it would be necessary to utilise a large number of tubes for every container, but this would still risk failing to detect other compounds and would be very expensive.

“It is possible to speciate organic compounds when using a Gas Chromatograph, but the number of compounds that can be tested is limited, and the use of a GC necessitates frequent calibration with expensive standard gases.”

Simultaneous multigas analysis
As a result of the problems associated with traditional gas detection techniques, Wim was keen to find an alternative technology and in 2013 he became aware of portable FTIR multigas analyzers from the Finnish company Gasmet Technologies. “The Gasmet DX4040 appeared to be the answer to our prayers,” Wim says. “The instrument is able to both detect and measure hundreds of compounds simultaneously; with this technique all inventoried high risk substances, such as ethylene oxide and formaldehyde, are always measured in real-time.

“With the help of Peter Broersma from Gasmet’s distributor Reaktie, a special library of over 300 gases was developed for our container monitoring application, and 8 Gasmet DX4040 FTIR instruments are now employed by our team of gas testing specialists.”

The major advantage of the Gasmet FTIR analyzers is the simultaneous multigas analysis capability. However Wim says: “Our testing work is now much faster, efficient and cost-effective, not least because the analyzers are small, lightweight, relatively simple to run, and no calibration is required other than a quick daily zero check with Nitrogen.”

Van Tienen Milieuadvies also employs a fully trained and highly qualified chemist, Tim Gielen, who is able to conduct in-depth analysis of recorded FTIR spectra when necessary. This may involve comparing results with Nist reference spectra for over 5000 compounds.

Most of the gases that are detected and measured by FTIR analyzers are cargo related. Wim says: “Off-gassing during shipment is the greatest problem, producing VOCs such as Toluene, Xylenes, MEK, 1,2 dichloroethane, blowing agents such as isopentane, and butanes from the packing materials and products.

“Formaldehyde, which evaporates from glued pallets, is most commonly found. On the other hand, less frequently found fumigants, such as sulfuryl difluoride and hydrogen cyanide are also always monitored with our FTIR analyzers.”

Container management
The need for container gas testing is driven by employers’ duty of care for employees, which is embedded in international health and safety regulations. Companies receiving containers must investigate whether employees that open or enter containers, may be exposed to the dangers of suffocation, intoxication, poisoning, fire or explosion. In order for employers to protect staff from these hazards, a risk assessment is necessary, coupled with an effective plan to categorise and monitor container flows. “This is how we develop an effective testing strategy,” Wim explains. “If a flow of containers from the same source containing the same goods and packing materials is found to be safe, the number of containers being tested within that flow can be reduced. Similarly, if toxic gases are identified regularly in a container flow, the frequency of testing will be increased.”

Once a container has been found to contain toxic levels of a gas or gases, it is necessary for that container to be ‘de-gassed’ which is a service that Van Tienen Milieuadvies provides. The process involves fitting a powerful ventilator to the door and capturing the gases with activated carbon. Once degassing is complete, it is important that the container is unloaded promptly, because the gases involved will re-accumulate quickly in a closed container, resulting in the need for repeat testing.

With the benefit of many years of experience, Wim estimates that around 10% of containers contain toxic gases. “This means that hundreds of thousands of containers are travelling the world, representing a major risk to anyone that might enter or open them, so it is vital that effective testing strategies are in place wherever that risk exists.”

“FTIR gas analysis has benefited this work enormously. For us, the main advantages are speed and peace of mind – we are now able to test more containers per day, and by testing for such a large number of target compounds, we are able to dramatically lower the risks to staff. The speed with which we are now able to test containers, coupled with the negligible requirement for service, calibration and consumables, means that the ongoing cost of monitoring is minimal.

“Van Tienen combines the Gasmet DX4040 measurements with risk analysis, which provides the best protection for staff responsible for opening containers. We have LRQA certification for the procedures that we have developed to demonstrate compliance with occupational health and safety legislation.

“Risk analysis provides cost reduction for our clients, due to the fact that measurement frequencies in safe flows can be reduced significantly. Root cause analysis is also part of our risk analysis.”

Looking forward Wim believes that the use of Gasmet FTIR will expand rapidly around the world as the risks associated with containers become better understood, and as employers become more aware of the advantages of the technology.