This work was supported financially by the DOD ARO grant #W911NF-15-1-0510 and National Science Foundation Research Initiation Awards under Grant No. 1411209. We express our sincere gratitude to Physics and Computer Science Department and the Division of Education at Xavier University of Louisiana.

1. Photometer Operation
NOTE: These protocols are best done by two people working together. One person holds and aligns the sun photometer while the second person record the measurements.
<ol>
	<li>Measure the longitude and latitude for the site using GPS. At the site, the first step is to activate the GPS by choosing sensor set-up from the sensor menu and select GPS. Once GPS has acquired enough satellites, latitude and longitude values will be displayed. Once values are displayed press collect data and then press save.</li>
	<li>Make sure the sun photometer is working well. A properly calibrated sun photometer should produce a stable voltage of ~0.03 V indoors and up to 5 V when light is directed on the detector. The voltmeter on the Globe sun photometer is in-built on the sun photometer</li>
	<li>Record the air temperature. If using an alcohol in glass thermometer, give the thermometer 3&#8211;5 min to adjust to the outside temperature before recording the stable reading. If using the sun photometer&#8217;s in-built thermometer, turn the rotary switch to T and record the voltage reading on the voltmeter. The voltage reading multiplied by the 100 will give the air temperature in degrees Celsius at that time.</li>
	<li>Set the rotary switch to the green channel of the sun photometer.</li>
	<li>Have one person align the sun photometer so that light passing through the hole on the top bracket produces a sunlight spot centered over the colored dot on the bottom bracket. For best results, use a table and a chair. The person aligning the sun photometer should sit on the chair and rest his/her arms on the table in order to obtain a steady reading.</li>
	<li>Have the second person record the reading on the voltmeter. Make sure the sun spot is stable on the dot before taking a reading. If voltage reading is fluctuating, just record the maximum value shown.</li>
	<li>Record the time at which the reading was taken. Time must be recorded to the nearest 30 s. A digital watch serves this purpose better than an analogue one.</li>
	<li>Obtain the dark voltage. Have the person sitting down keep the sun photometer aligned to the sun with one hand and then cover the hole on the top bracket with a finger from the other hand. The second person will record the voltage reading.</li>
	<li>Set the rotary switch to the red channel and repeat steps 1.4&#8211;1.7.</li>
	<li>Repeat steps 1.4&#8211;1.8 four more times to obtain five voltages readings for the green channel and five voltage readings for the red channel</li>
	<li>Measure the air temperature again as in step 1.2.</li>
</ol>
2. Collection of Metadata
<ol>
	<li>Use the Globe cloud chart to observe and record the clouds near the sun. This is done by looking into the sky and checking off observed features from the GLOBE cloud chart (https://www.globe.gov/documents/348614/24331082/GLOBE+Cloud+Chart.). Visible cirrus clouds are easy to observe because of their characteristic thin wispy strands. Invisible cirrus clouds are inferred if the sunlight voltage reading on an apparently clear day is less than 0.5 V.
	<ol>
		<li>Use a hygrometer to measure and record the relative humidity: Hold the hygrometer with an extended arm away from the body, leave it in the air for about 3 minutes, and then take the dry bulb reading first followed by the wet bulb reading. Find the difference in the two readings and use the relative humidity chart to establish the relative humidity</li>
		<li>Use a barometer to measure and record atmospheric pressure.</li>
	</ol>
	</li>
	<li>Calculate AOT by plugging the measured values and the constants into Equation 1 given above.</li>
</ol>
3. Temperature Regulation
NOTE: The electronics of the sun photometer are sensitive to temperature. For optimal performance, the following steps are recommended.
<ol>
	<li>If outside temperature is more than 5 degrees&#160;below room temperature, keep the sun photometer wrapped in thermal foam when not in use.</li>
	<li>When taking measurements during the hot summer months, keep the sun photometer in the shade when not in use.</li>
</ol>

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D., Uchiyama, A., Asano, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Optical+depth+measurements+of+aerosol,+cloud+and+water+vapor+using+sun+photometers+during+theFIRE+Cirrus+II.">Optical depth measurements of aerosol, cloud and water vapor using sun photometers during theFIRE Cirrus II.</a> Journal of Applied Meteorology. 35, 364-366 (1991).</li><li>A&#239;ssani, O., Mokhnache, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Aerosol+size+distribution+retrieved+from+optical+depth+measurements+in+Tamanrasset+and+Blida.">Aerosol size distribution retrieved from optical depth measurements in Tamanrasset and Blida.</a> Revue des Energies Renouvelables. 15 (2), 207-218 (2012).</li><li>Bucholtz, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Rayleigh-scattering+calculations+for+the+terrestrial+atmosphere.">Rayleigh-scattering calculations for the terrestrial atmosphere.</a> Applied Optics. 34, 2765-2773 (1995).</li><li>Brooks, D. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Monitoring+Solar+Radiation+and+Its+Transmission+through+the+Atmosphere.">Monitoring Solar Radiation and Its Transmission through the Atmosphere.</a> The GLOBE Program's Aerosols, Water Vapor, and UVA Monitoring Projects. , (2006).</li><li>Holben, B. N., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=AERONET+-+A+federated+instrument+network+and+data+archive+for+aerosol+characterization.">AERONET - A federated instrument network and data archive for aerosol characterization.</a> Remote Sensing of the Environment. 66, 1-16 (1998).</li><li>Toledo, F., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=AOT+retrieval+procedure+for+distributed+measurements+with+low-cost+Sun+photometers.">AOT retrieval procedure for distributed measurements with low-cost Sun photometers.</a> Journal of Geophysical Research Atmospheres. 123, 1113-1131 (2017).</li><li>Giles, D. M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Advancements+in+the+Aerosol+Robotic+Network+(AERONET)+1+Version+3+Database+-+Automated+Near+Real-Time+Quality+Control+Algorithm+with+Improved+Cloud+Screening+for+Sun+Photometer+Aerosol+Optical+Depth+(AOD)+Measurements.">Advancements in the Aerosol Robotic Network (AERONET) 1 Version 3 Database - Automated Near Real-Time Quality Control Algorithm with Improved Cloud Screening for Sun Photometer Aerosol Optical Depth (AOD) Measurements.</a> Atmospheric Measurement Techniques Discussions. , (2018).</li><li>Zawadzka, I., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Studies+of+aerosol+optical+depth+with+the+use+of+Microtops+II+sun+photometers+and+MODIS+detectors+in+coastal+areas+of+the+Baltic+Sea.">Studies of aerosol optical depth with the use of Microtops II sun photometers and MODIS detectors in coastal areas of the Baltic Sea.</a> Acta Geophysica. 62 (2), 400-422 (2014).</li><li>Bovchaliuk, V., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Aerosol+Microtops+II+sunphotometer+observations+over+Ukraine.">Aerosol Microtops II sunphotometer observations over Ukraine.</a> Advances in Astronomy and Space Physics. 3, 46-52 (2013).</li><li>More, S., Kumar, P. 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The authors declare no conflict of interest.

The first step in this protocol is to define the study site. This is done by using a GPS to find the longitude and latitude of the study site. The longitude and latitude values are critical in the calculation of AOT using equation 1. During measurement, it is crucial that the sun photometer is pointed directly and firmly at the sun. The tiny hole at the top bracket of the handheld sun photometer reduces the amount of scattered light reaching the LED detectors in the sun photometer. Equation 1 is an approximation that ass...

Atmospheric aerosols are minute solid and liquid particles (ranging from submicron to millimeter size) suspended in the air. Some aerosols are produced through human activity and others are produced by natural processes1,2,3,4. Aerosols in the atmosphere reduce the amount of solar energy reaching the earth&#8217;s surface by scattering or absorbing light and thermal radiation from the sun. The amount of aerosol in the atmosphere varies significantly with location and time. There are seasonal and annual changes as well as episodic changes due to events such as large dust storms, wild fires or volcanic eruptions5,6,7,8.
The impact of aerosols on the climate and on public health are among the dominant topics in current environmental research. Aerosols affect the weather by scattering or absorbing light and thermal radiation from the sun and by acting as condensation nuclei in the formation of clouds. Aerosols also play a role in the dispersal of pathogens in the air and they can cause or enhance respiratory and cardiovascular diseases. Aerosol optical thickness (AOT) is a measure of the amount of sunlight that is absorbed or scattered by these aerosols. There are several ground-based methods for monitoring AOT9,10,11. The biggest of the ground-based AOT monitoring system is the Aerosol Robotic Network (AERONET) project. AERONET is a network of over 400 monitoring stations spread all over the world12,13. Despite this large number of monitoring stations, there are still large gaps world-wide that are not monitored for AOT. As an example, the nearest AERONET station from our study site is about 90 km away. This paper describes the use of a portable handheld sun photometer that can be used to bridge the gaps between AERONET monitoring stations. The portable handheld sun photometer is an ideal instrument for use by students around the world in a global aerosol monitoring network14,15. The Global Learning and Observations to Benefit the Environment (GLOBE) program provides a platform for such a network, through thousands of schools in all the 50 states of the United States and in nearly 120 other countries16,17. The primary idea of the GLOBE program is to use students all over the world to provide scientifically valuable measurements of environmental parameters using inexpensive equipment. With proper guidance, students and other non-specialist can form networks of handheld sun photometers to fill the gaps between the AERONET monitoring stations. The biggest advantage of the handheld sun photometer is that it can be taken to even the remotest parts of the world. AOT measurements with other small and transportable instruments have been successfully used in the past to carry out research studies in remote and hard to access areas17,18
The main goal of this study is to use the GLOBE handheld sun photometers to track the annual, daily and hourly variation of AOT at our XULA study site and compare with measurements from a nearby AERONET station. This paper presents data for a 12 months period from September 2017 to August 2018. This is the first ever AOT recorded for the XULA site. The GLOBE sun photometer measures AOT at two wavelengths, 505 nm and 625 nm. The AERONET site at Wave CIS Site 6 measures AOT at 15 different wavelengths. For our comparison we focused on these 4 wavelengths, 667 nm, 551 nm, 532 nm and 490 nm. We chose these because they are the 4 AERONET wavelengths nearest to the GLOBE sun photometer wavelengths. To make the comparison, we extrapolated AOT values at these wavelengths for XULA site.
Measurements of AOT are done every day when the weather conditions permit. Measurements that are done when there are cirrus clouds within the vicinity of the sun are excluded in the analysis. Table 1 shows the number of days in each month that we had completely clear skies. Altogether, about 47% of the data taken was excluded.
<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Month</td>
			<td>Sept</td>
			<td>Oct</td>
			<td>Nov</td>
			<td>Dec</td>
			<td>Jan</td>
			<td>Feb</td>
			<td>Mar</td>
			<td>Apr</td>
			<td>May</td>
			<td>Jun</td>
			<td>Jul</td>
			<td>Aug</td>
		</tr>
		<tr>
			<td>Number of Days</td>
			<td>18</td>
			<td>20</td>
			<td>16</td>
			<td>15</td>
			<td>15</td>
			<td>15</td>
			<td>16</td>
			<td>15</td>
			<td>18</td>
			<td>15</td>
			<td>15</td>
			<td>16</td>
		</tr>
	</tbody>
</table>
Table 1:&#160;AOT measurements were done 6 times a day (7:00 AM, 9 AM, 11 AM, solar noon, 3 AM, and 5 AM). The data shown on the plots are the monthly average AOT values taken at solar noon. During each measurement time; at least five values of the sunlight voltage V and the dark voltage Vdark are taken for each channel. The mean for these five measurements is taken as the average for that measurement time. The error in these measurements is calculated as the standard deviations of these five measurements. AOT values are obtained using the equation shown below16:
<img alt="Equation 1" src="/files/ftp_upload/59257/59257eq1.jpg" />
V0 is the calibration constant of the sun photometer, R is the earth-sun distance in astronomical units, Vdark is the dark voltage recorded when light is blocked from passing through the hole on the top bracket of the sun photometer, V is the sunlight voltage recorded from the sun photometer when light passes through the hole on the top bracket, aR represents the attenuation of light due to Rayleigh scattering, P and P0 are the measured and standard atmospheric pressure, respectively, and m is the relative air mass. The relative air mass is calculated from data provided by the National Oceanic and Atmospheric Administration&#160;(NOAA). Other meteorological data such as temperature, rainfall and relative humidity are also measured at the same time. Equation 1 as given above includes the contributions of optical thickness from ozone. The effect of ozone on AOT values is calculated based on tabulated values of the ozone absorption coefficient and assumptions about the ozone amount in the atmosphere19. Bucholtz20,21 has produced tabulated values of aR based on standard atmospheres. For the 505 nm channel aR &#8776; 0.13813 and for the 625 nm channel it is ~0.05793.
The data presented here represents an example of how teams of students can be organized to take long and sustained AOT measurements. In this study, two student teams used two independently calibrated GLOBE handheld sun photometers to track the annual, daily and hourly variation of the aerosol optical thickness of the atmosphere at our XULA study site. The two Globe sun photometers used in this investigation were purchased from the IESRE (Institute for Earth Science Research and Education; one had serial number RG8-989 and the other had serial number RG8-990). Before the data from the two instruments could be combined, a regression analysis was carried out to ascertain the agreement

<table>
	<tbody>
		<tr>
			<td>A Calibrated GLOBE handheld sun photometer</td>
			<td>IESRE, USA (GLOBE sun photometer) and TERNUM, UK (Calitoo sun photometer</td>
			<td></td>
			<td>The GLOBE sun photometer measures AOT at 505nm and 625nm.</td>
		</tr>
		<tr>
			<td>Barometer</td>
			<td>Forestry suppliers, USA, Cat# 43316</td>
			<td>43316</td>
			<td>The aneroid barometer must have a clear scale with a pressure range between 940 and 1060 millibars.</td>
		</tr>
		<tr>
			<td>GLOBE cloud chart</td>
			<td>Forestry Suppliers, USA Cat#33485</td>
			<td>33485</td>
			<td>A free cloud identification chart is obtained from www.globe.gov.</td>
		</tr>
		<tr>
			<td>Hygrometer</td>
			<td>Forestry suppliers, USA, Cat# 76254</td>
			<td>76245</td>
			<td>Any digital hygrometer which measures relative humidity in the range of 20-95% with an accuracy of 5% is acceptable.</td>
		</tr>
		<tr>
			<td>Labquest2 GPS</td>
			<td>Vernier, USA, Cat LABQ2</td>
			<td>LABQ2</td>
			<td>Vernier LabQuest 2 is a standalone interface used to collect sensor data with its built-in graphing and analysis application. GPS is one of its built-in sensors</td>
		</tr>
		<tr>
			<td>Taylor Orchid Thermometer</td>
			<td>Forestry Suppliers, USA Cat# 89129</td>
			<td>89129</td>
			<td></td>
		</tr>
		<tr>
			<td>Watch</td>
			<td>Forestry suppliers, USA, Cat# 39137</td>
			<td>39137</td>
			<td>The watch must be digital and capable of measuring time up to seconds.</td>
		</tr>
	</tbody>
</table>

measurement of aerosols optical thickness of the atmosphere using the globe handheld sun photometer

Here, we describe the measurement of aerosol optical thickness using the GLOBE handheld sun photometer. Aerosol optical thickness (AOT) was measured at Xavier University of Louisiana (XULA, 29.96&#176; N, 90.11&#176; W and 3 m above sea level). The measurements were done at two different wavelengths, 505 nm and 625 nm. AOT measurements were done 6 times a day (7 AM, 9 AM, 11 AM, solar noon, 3 PM and 5 PM). The data shown in this paper are the monthly average AOT values taken at solar noon. During each measurement time; at least five values of the sunlight voltage V and the dark voltage Vdark are taken for each channel. The mean for these five measurements is taken as the average for that measurement time. Other meteorological data such as temperature, surface pressure, rainfall and relative humidity are also measured at the same time. The whole protocol is completed within a time span of 10&#8211;15 min. The measured AOT values at 505 nm and 625 nm are then used to extrapolate the AOT values for wavelengths 667 nm, 551 nm, 532 nm and 490 nm. The measured and extrapolated AOT values were then compared with values from the nearest AERONET station at Wave CIS site 6 (AERONET, 28.87&#176; N, 90.48&#176; W and 33 m above sea level), which is about 96 km south of XULA. In this study we tracked the annual and daily variations of AOT for a 12 month period from September 2017 to August 2018. We also compared AOT data from two independently calibrated GLOBE handheld sun photometers at the XULA site. The data show that the two instruments are in excellent agreement.

The GLOBE sun photometer measures AOT at &#955;= 505 nm and &#955;= 625 nm. The AERONET site at Wave CIS Site 6 measures AOT at 15 different wavelengths. For our comparison we focused on these 4 wavelengths of the AERONET site: 667 nm, 551 nm, 532 nm and 490 nm. To make a comparison between the two stations, we extrapolated AOT at 667 nm, 551 nm, 532 nm and 490 nm for the XULA site. This is done using the XULA site&#8217;s Angstrom coefficients. For any given site and instrument, the opti...

Watch this Scientific Journal Video about Measurement of Aerosols Optical Thickness of the Atmosphere using the GLOBE Handheld Sun Photometer at JoVE.com

Measurement of Aerosols Optical Thickness of the Atmosphere using the GLOBE Handheld Sun Photometer

The goal of the methods presented here is to measure aerosol optical thickness of the atmosphere. The sun photometer is pointed at the sun and the largest voltage reading obtained on an in-built digital voltmeter is recorded. Atmospheric measurements such as barometric pressure and relative humidity are also performed.

Here, we describe the measurement of aerosol optical thickness using the GLOBE handheld sun photometer. Aerosol optical thickness (AOT) was measured at ...

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7.8K Views.  Xavier University of Louisiana. The goal of the methods presented here is to measure aerosol optical thickness of the atmosphere. The sun photometer is pointed at the sun and the largest voltage reading obtained on an in-built digital voltmeter is recorded. Atmospheric measurements such as barometric pressure and relative humidity are also performed.

Video: Measurement of Aerosols Optical Thickness of the Atmosphere using the GLOBE Handheld Sun Photometer

Determination of Microbial Extracellular Enzyme Activity in Waters, Soils, and Sediments using High Throughput Microplate Assays

Much of the nutrient cycling and carbon processing in natural environments occurs through the activity of extracellular enzymes released by microorganisms. Thus, measurement of the activity of these extracellular enzymes can give insights into the rates of ecosystem level processes, such as organic matter decomposition or nitrogen and phosphorus mineralization. Assays of extracellular enzyme activity in environmental samples typically involve exposing the samples to artificial colorimetric or fluorometric substrates and tracking the rate of substrate hydrolysis. Here we describe microplate based methods for these procedures that allow the analysis of large numbers of samples within a short time frame. Samples are allowed to react with artificial substrates within 96-well microplates or deep well microplate blocks, and enzyme activity is subsequently determined by absorption or fluorescence of the resulting end product using a typical microplate reader or fluorometer. Such high throughput procedures not only facilitate comparisons between spatially separate sites or ecosystems, but also substantially reduce the cost of such assays by reducing overall reagent volumes needed per sample.

Microplate based procedures are described for the colorimetric or fluorometric analysis of extracellular enzyme activity. These procedures allow for the rapid assay of such activity in large numbers of environmental samples within a manageable time frame.

Much of the nutrient cycling and carbon  processing in natural environments occurs through the activity of extracellular  enzymes released by ...

VacuSIP, an Improved InEx Method for In Situ Measurement of Particulate and Dissolved Compounds Processed by Active Suspension Feeders

Benthic suspension feeders play essential roles in the functioning of marine ecosystems. By filtering large volumes of water, removing plankton and detritus, and excreting particulate and dissolved compounds, they serve as important agents for benthic-pelagic coupling. Accurately measuring the compounds removed and excreted by suspension feeders (such as sponges, ascidians, polychaetes, bivalves) is crucial for the study of their physiology, metabolism, and feeding ecology, and is fundamental to determine the ecological relevance of the nutrient fluxes mediated by these organisms. However, the assessment of the rate by which suspension feeders process particulate and dissolved compounds in nature is restricted by the limitations of the currently available methodologies. Our goal was to develop a simple, reliable, and non-intrusive method that would allow clean and controlled water sampling from a specific point, such as the excurrent aperture of benthic suspension feeders, in situ. Our method allows simultaneous sampling of inhaled and exhaled water of the studied organism by using minute tubes installed on a custom-built manipulator device and carefully positioned inside the exhalant orifice of the sampled organism. Piercing a septum on the collecting vessel with a syringe needle attached to the distal end of each tube allows the external pressure to slowly force the sampled water into the vessel through the sampling tube. The slow and controlled sampling rate allows integrating the inherent patchiness in the water while ensuring contamination free sampling. We provide recommendations for the most suitable filtering devices, collection vessel, and storing procedures for the analyses of different particulate and dissolved compounds. The VacuSIP system offers a reliable method for the quantification of undisturbed suspension feeder metabolism in natural conditions that is cheap and easy to learn and apply to assess the physiology and functional role of filter feeders in different ecosystems.

VacuSIP, an Improved InEx Method for In Situ Measurement of Particulate and Dissolved Compounds Processed by Active Suspension Feeders

We introduce the VacuSIP, a simple, non-intrusive, and reliable method for clean and accurate point sampling of water. The system was developed and evaluated for the simultaneous collection of the water inhaled and exhaled by benthic suspension feeders in situ, to cleanly measure removal and excretion of particulate and dissolved compounds.

Benthic suspension feeders play essential roles in the functioning of marine ecosystems. By filtering large volumes of water, removing plankton and ...

Biofilm Removal Using Carbon Dioxide Aerosols without Nitrogen Purge

Biofilms can cause serious concerns in many applications. Not only can they cause economic losses, but they can also present a public health hazard. Therefore, it is highly desirable to remove biofilms from surfaces. Many studies on CO2 aerosol cleaning have employed nitrogen purges to increase biofilm removal efficiency by reducing the moisture condensation generated during the cleaning. However, in this study, periodic jets of CO2 aerosols without nitrogen purges were used to remove Pseudomonas putida biofilms from polished stainless steel surfaces. CO2 aerosols are mixtures of solid and gaseous CO2 and are generated when high-pressure CO2 gas is adiabatically expanded through a nozzle. These high-speed aerosols were applied to a biofilm that had been grown for 24 hr. The removal efficiency ranged from 90.36% to 98.29% and was evaluated by measuring the fluorescence intensity of the biofilm as the treatment time was varied from 16 sec to 88 sec. We also performed experiments to compare the removal efficiencies with and without nitrogen purges; the measured biofilm removal efficiencies were not significantly different from each other (t-test, p &gt; 0.55). Therefore, this technique can be used to clean various bio-contaminated surfaces within one minute.

Biofilms on surfaces can be effectively and rapidly removed by using a periodic jet of carbon dioxide aerosols without a nitrogen purge.

Biofilms can cause serious concerns in many applications. Not only can they cause economic losses, but they can also present a public health hazard. ...

Controlled-release of Chlorine Dioxide in a Perforated Packaging System to Extend the Storage Life and Improve the Safety of Grape Tomatoes

A controlled-release chlorine dioxide (ClO2) pouch was developed by sealing a slurry form of ClO2 into semipermeable polymer film; the release properties of the pouch were monitored in containers with or without fruit. The pouch was affixed to the inside of a perforated clamshell containing grape tomatoes, and the effect on microbial population, firmness, and weight loss was evaluated during a 14 day storage period at 20 &#176;C. Within 3 days, the ClO2 concentration in the clamshells reached 3.5 ppm and remained constant until day 10. Thereafter, it decreased to 2 ppm by day 14. The ClO2 pouch exhibited strong antimicrobial activity, reducing Escherichia coli populations by 3.08 log CFU/g and Alternaria alternata populations by 2.85 log CFU/g after 14 days of storage. The ClO2 treatment also reduced softening and weight loss and extended the overall shelf life of the tomatoes. Our results suggest that ClO2 treatment is useful for extending the shelf life and improving the microbial safety of tomatoes during storage without impairing their quality.

Here, we describe a protocol for the application of a novel, slow-release ClO2 product that reduces spoilage and extends the shelf life of fresh fruit. The slow-release ClO2 product was added to standard commercial grape tomato packaging and tested against Escherichia coli and Alternaria alternata.

A controlled-release chlorine dioxide (ClO2) pouch was developed by sealing a slurry form of ClO2 into semipermeable polymer film; the release properties ...

Extraction and Characterization of Surfactants from Atmospheric Aerosols

Surface-active compounds, or surfactants, present in atmospheric aerosols are expected to play important roles in the formation of liquid water clouds in the Earth&#39;s atmosphere, a central process in meteorology, hydrology, and for the climate system. But because specific extraction and characterization of these compounds have been lacking for decades, very little is known on their identity, properties, mode of action and origins, thus preventing the full understanding of cloud formation and its potential links with the Earth&#39;s ecosystems.
In this paper we present recently developed methods for 1) the targeted extraction of all the surfactants from atmospheric aerosol samples and for the determination of 2) their absolute concentrations in the aerosol phase and 3) their static surface tension curves in water, including their Critical Micelle Concentration (CMC). These methods have been validated with 9 references surfactants, including anionic, cationic and non-ionic ones. Examples of results are presented for surfactants found in fine aerosol particles (diameter &#60;1 &#956;m) collected at a coastal site in Croatia and suggestions for future improvements and other characterizations than those presented are discussed.

Methods are presented for the targeted extraction of surfactants present in atmospheric aerosols and the determination of their absolute concentrations and surface tension curves in water, including their Critical Micelle Concentration (CMC).

Surface-active compounds, or surfactants, present in atmospheric aerosols are expected to play important roles in the formation of liquid water clouds in ...

Production and Measurement of Organic Particulate Matter in the Harvard Environmental Chamber

The production and the evolution of atmospheric organic particulate matter (PM) are insufficiently understood for accurate simulations of atmospheric chemistry and climate. The complex production mechanisms and reaction pathways make this a challenging research topic. To address these issues, an environmental chamber, providing enough residence time and close-to-ambient concentrations of precursors for secondary organic materials, is needed. The Harvard Environmental Chamber (HEC) was built to serve this need, simulating the production of gas and particle phase species from volatile organic compounds (VOCs). The HEC has a volume of 4.7 m3 and a mean residence time of 3.4 h under typical operating conditions. It is operated as a completely mixed flow reactor (CMFR), providing the possibility of indefinite steady-state operation across days for sample collection and data analysis. The operation procedures are described in detail in this article. Several types of instrumentation are used to characterize the produced gas and particles. A High-Resolution Time-of-Fight Aerosol Mass Spectrometer (HR-ToF-AMS) is used to characterize particles. A Proton-Transfer-Reaction Mass Spectrometer (PTR-MS) is used for gaseous analysis. Example results are presented to show the use of the environmental chamber in a wide variety of applications related to the physicochemical properties and reaction mechanisms of organic atmospheric particulate matter.

This paper describes operation procedures for the Harvard Environmental Chamber (HEC) and related instrumentation for measuring gaseous and particle species. The environmental chamber is used to produce and study secondary organic species produced from the organic precursors, especially related to atmospheric organic particulate matter.

The production and the evolution of atmospheric organic particulate matter (PM) are insufficiently understood for accurate simulations of atmospheric ...

Measurement of the Rheology of Crude Oil in Equilibrium with CO2 at Reservoir Conditions

A rheometer system to measure the rheology of crude oil in equilibrium with carbon dioxide (CO2) at high temperatures and pressures is described. The system comprises a high-pressure rheometer which is connected to a circulation loop. The rheometer has a rotational flow-through measurement cell with two alternative geometries: coaxial cylinder and double gap. The circulation loop contains a mixer, to bring the crude oil sample into equilibrium with CO2, and a gear pump that transports the mixture from the mixer to the rheometer and recycles it back to the mixer. The CO2 and crude oil are brought to equilibrium by stirring and circulation and the rheology of the saturated mixture is measured by the rheometer. The system is used to measure the rheological properties of Zuata crude oil (and its toluene dilution) in equilibrium with CO2 at elevated pressures up to 220 bar and a temperature of 50 &#176;C. The results show that CO2 addition changes the oil rheology significantly, initially reducing the viscosity as the CO2 pressure is increased and then increasing the viscosity above a threshold pressure. The non-Newtonian response of the crude is also seen to change with the addition of CO2.

Measurement of the Rheology of Crude Oil in Equilibrium with CO2 at Reservoir Conditions

A method for measuring the rheology of crude oil in equilibrium with carbon dioxide at reservoir conditions is presented.

A rheometer system to measure the rheology of crude oil in equilibrium with carbon dioxide (CO2) at high temperatures and pressures is described. The ...

Preparation of Authigenic Pyrite from Methane-bearing Sediments for In Situ Sulfur Isotope Analysis Using SIMS

Different sulfur isotope compositions of authigenic pyrite typically result from the sulfate-driven anaerobic oxidation of methane (SO4-AOM) and organiclastic sulfate reduction (OSR) in marine sediments. However, unravelling the complex pyritization sequence is a challenge because of the coexistence of different sequentially formed pyrite phases. This manuscript describes a sample preparation procedure that enables the use of secondary ion mass spectroscopy (SIMS) to obtain in situ &#948;34S values of various pyrite generations. This allows researchers to constrain how SO4-AOM affects pyritization in methane-bearing sediments. SIMS analysis revealed an extreme range in &#948;34S values, spanning from -41.6 to +114.8&#8240;, which is much wider than the range of &#948;34S values obtained by the traditional bulk sulfur isotope analysis of the same samples. Pyrite in the shallow sediment mainly consists of 34S-depleted framboids, suggesting early diagenetic formation by OSR. Deeper in the sediment, more pyrite occurs as overgrowths and euhedral crystals, which display much higher SIMS &#948;34S values than the framboids. Such 34S-enriched pyrite is related to enhanced SO4-AOM at the sulfate-methane transition zone, postdating OSR. High-resolution in situ SIMS sulfur isotope analyses allow for the reconstruction of the pyritization processes, which cannot be resolved by bulk sulfur isotope analysis.

Preparation of Authigenic Pyrite from Methane-bearing Sediments for In Situ Sulfur Isotope Analysis Using SIMS

Analyses of the sulfur isotopic composition (&#948;34S) of pyrite from methane-bearing sediments have typically focused on bulk samples. Here, we applied secondary ion mass spectroscopy to analyze the &#948;34S values of various pyrite generations to understand the diagenetic history of pyritization.

Different sulfur isotope compositions of authigenic pyrite typically result from the sulfate-driven anaerobic oxidation of methane (SO4-AOM) and ...

Development of New Methods for Quantifying Fish Density Using Underwater Stereo-video Tools

The use of video camera systems in ecological studies of fish continues to gain traction as a viable, non-extractive method of measuring fish lengths and estimating fish abundance. We developed and implemented a rotating stereo-video camera tool that covers a full 360 degrees of sampling, which maximizes sampling effort compared to stationary camera tools. A variety of studies have detailed the ability of static, stereo-camera systems to obtain highly accurate and precise measurements of fish; the focus here was on the development of methodological approaches to quantify fish density using rotating camera systems. The first approach was to develop a modification of the metric MaxN, which typically is a conservative count of the minimum number of fish observed on a given camera survey. We redefine MaxN to be the maximum number of fish observed in any given rotation of the camera system. When precautions are taken to avoid double counting, this method for MaxN may more accurately reflect true abundance than that obtained from a fixed camera. Secondly, because stereo-video allows fish to be mapped in three-dimensional space, precise estimates of the distance-from-camera can be obtained for each fish. By using the 95% percentile of the observed distance from camera to establish species-specific areas surveyed, we account for differences in detectability among species while avoiding diluting density estimates by using the maximum distance a species was observed. Accounting for this range of detectability is critical to accurately estimate fish abundances. This methodology will facilitate the integration of rotating stereo-video tools in both applied science and management contexts.

We describe a new method for counting fishes, and estimating relative abundance (MaxN) and fish density using rotating stereo-video camera systems. We also demonstrate how to use distance from camera (Z distance) to estimate species-specific detectability.

The use of video camera systems in ecological studies of fish continues to gain traction as a viable, non-extractive method of measuring fish lengths and ...

The Plant Infection Test: Spray and Wound-Mediated Inoculation with the Plant Pathogen Magnaporthe Grisea

Plants possess a powerful system to defend themselves against potential threats by pathogenic fungi. For agriculturally important plants, however, current measures to combat such pathogens have proved too conservative and, thus, not sufficiently effective, and they can potentially pose environmental risks. Therefore, it is extremely necessary to identify host-resistance factors to assist in controlling plant diseases naturally through the identification of resistant germplasm, the isolation and characterization of resistance genes, and the molecular breeding of resistant cultivars. In this regard, there is need to establish an accurate, rapid, and large-scale inoculation method to breed and develop plant resistance genes. The rice blast fungal pathogen Magnaporthe grisea causes severe disease symptoms and yield losses. Recently, M. grisea has emerged as a model organism for studying the mechanisms of plant-fungal pathogen interactions. Hence, we report the development of a plant virulence test method that is specific for M. grisea. This method provides for both spray inoculation with a conidial suspension and wounding inoculation with mycelium cubes or droplets of conidial suspension. The key step of the wounding inoculation method for detached rice leaves is to make wounds on plant leaves, which avoids any interference caused by host penetration resistance. This spray/wounding protocol contributes to the rapid, accurate, and large-scale screening of the pathotypes of M. grisea isolates. This integrated and systematic plant infection method will serve as an excellent starting point for gaining a broad perspective of issues in plant pathology.

The Plant Infection Test: Spray and Wound-Mediated Inoculation with the Plant Pathogen Magnaporthe Grisea

Here, we present a protocol to test plant virulence with the plant pathogen Magnaporthe grisea. This report will contribute to the large-scale screening of the pathotypes of fungi isolates and serve as an excellent starting point for understanding the resistant mechanisms of plants during molecular breeding.

Plants possess a powerful system to defend themselves against potential threats by pathogenic fungi. For agriculturally important plants, however, current ...