This work was funded by SONATA, a joint project between the French Agence Nationale de la Recherche (ANR-13-IS08-0001) and the US National Science Foundation. Christine Baduel is funded by the French National Research Agency (ANR) through the ANR-16-ACHN-0026 project. The authors also warmly thank Marija Margu&#353;, Ana Cvite&#353;i&#263;, Sanja Frka Milosavljevi&#263; and Irena Ciglenecki, from Rudjer Boskovic Institute of Zagreb, Croatia for the help with the aerosol sampling at Marina Frapa, Rogoznica, Croatia.

<ol>
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The authors have nothing to disclose.

In the protocol, all the critical steps have been detailed. They include the collection of the aerosols on filters, the extraction of surfactants from them (using a double extraction: a water extraction followed by a SPE extraction) and the analysis of the extracts (surface tension and concentration measurements).
For the whole method, a quality control has been made 1) by the application of the extraction and analysis method on blank filters (deviation &#60;5 mN m-1 compared with ultrapure water on the surface tension and absorbance under the detection limit for the colorimetric method), 2) by determining the extraction efficiency and their uncertainties including the reproducibility/repeatability, the % of extracted surfactants in a given range of concentration, 3) by checking the potential interferents on the colorimetric method, i.e. by checking that the method detects only the targeted type of surfactant (anionic, cationic and non-ionic) and do not see the others as fully detailed in references4,6) by checking potential interferents from the aerosol extracts (inorganic salts, small acids) on the colorimetric method as fully detailed in reference6.
To our knowledge, the extraction method for surfactants from atmospheric samples presented in this article is currently the most selective one in atmospheric chemistry. In particular it is much more selective than the simple water extractions performed in the past for the investigation of these compounds.11,23,24 The second extraction step is important as it has been shown to remove ionic components, such as inorganic salts and small organic acids, that are in large concentrations in the aerosol samples and interfere with the concentration measurements.6 This extraction method has also been shown to remove all the surfactants present in the samples, at the surface and in the bulk. The resulting extracts are thus concentrated enough to allow for accurate characterizations of these compounds.
However, in addition to surfactants, it is possible that other non-polar or mildly polar compounds are extracted from the atmospheric aerosols. For instance, &#34;Humic-like Substances&#34; (HULIS), that are usually extracted by similar methods25 and, depending on the sampling region, could be present in the extracts. These compounds are only mildly surfactant compared to the surfactants characterized in our samples,26,27,28 thus should not contribute significantly to the surface tension or CMC measured. However, they are polyacids and could interfere with the anionic concentration measurements. In the future, their contribution to the surfactant concentrations (i.e. whether or not they react with ethyl violet, the dye used to titrate anionic surfactants) will need to be determined. If their contribution is significant, extra steps could be added to the extraction method, to eliminate for instance all the compounds that are active in the UV-Vis or by fluorescence, which would include HULIS but not surfactants.
So far, no other method for the measurement of the surface tension of aerosols and of the surface tension curve for aerosol surfactants than the one presented in this manuscript is available. The hanging droplet technique is recommended for these measurements as it is the only one requiring sample volumes consistent with atmospheric samples. Optical techniques, measuring directly the surface tension on micron-size particles without any extraction, are being developed.10,20,29 So far, they are only applicable to laboratory-produced particles but could potentially someday be applied to atmospheric ones.
The colorimetric method presented in this work for the measurement of surfactant concentration has been applied previously to atmospheric aerosol samples11,13,14,30 but only to water extracts and not to double extracts, as in our method. This is an important difference as, as underlined above, the second extraction step removes compounds such as inorganic salts and small organic acids, which interfere with the concentration measurements.6
An electrochemical technique, initially developed for seawater and larger aqueous samples, has also been used to measure the concentration of surfactants in atmospheric aerosols.31,32 This method is relative, i.e. the surfactant concentrations obtained depend on the reference compounds chosen and assume that the detection sensitivity of all surfactants is identical. The detection limit reported for this technique is 0.02 mg L-1 when using tetra-octylphenolethoxylate as reference, thus 0.03 &#956;M, and comparable to the detection limit of about 0.05 &#956;M for anionic and cationic surfactants by the colorimetric method. But because of the uncertainties in the determination of the non-ionic and total surfactant concentrations with the colorimetric method, it would be interesting to compare both methods (inter-calibration).
A few points in the presented methods could be further improved.
Another dye than cobalt thiocyanate that would detect all non-ionic surfactants and wit the same sensitivity would be very useful and reduce the main source of uncertainties in the current concentration measurements.
The extraction efficiency for cationic surfactants, currently estimated to 20%, could also be improved, as these compounds are often at the detection limit in atmospheric samples. This could be done, for instance, by using a specific SPE column.
The extractions and titration conditions could be further improved. For instance, using in parallel three different SPE set-ups, each optimized for a class of surfactants, could improve the extraction efficiency, and improve the quality of the procedure (less contamination risks). The optimum sorbent density of the SPE cartridge for the sample mass to be analyzed could also been determined. The conditions for the titration reactions (pH, additives) could also be further optimized, to further improve the sensitivity of the concentration measurements, i.e. lower the detection limits.
Additional tests or steps could be added to the extraction protocol to exclude the non-surfactant compounds that might have been extracted. For instance, the potential presence of HULIS in the samples could be investigated by optical techniques (UV-Vis or fluorescence).
Further modifications, while not improving the quality of the analysis itself, would bring more information on atmospheric surfactants, such as applying the present method to different size-fractions (i.e. sub-populations) of the aerosol rather than on all the particles collected, as presented here. Other types of analyses could also be applied to the extracts such as, LC/HR MS, tandem MS, or NMR to determine the chemical structure of the surfactants or UV-Vis absorbance, fluorescence, or polarimetry, to indicate the presence of highly-conjugated or chiral compounds in the extracts.

Clouds are essential in the Earth&#39;s atmosphere, for the hydrology of most environments and ecosystems, and for the climate system. But some aspects of their formation mechanisms are still not understood, in particular the contributions of the chemical compounds present in the aerosol particles that act as condensation nuclei. Theory1 predicts that surface-active compounds, or surfactants, present in aerosol particles should strongly enhance cloud droplet formation by lowering their surface tension, thus their formation energy. But these effects have remained elusive to observation for decades and the role of surfactants on cloud formation is currently denied by a large part of the atmospheric community and ignored in all cloud investigations and atmospheric and climate models.
One reason for the lack of understanding of the role of aerosol surfactants in cloud formation has been the absence of method to isolate and characterize them. Unlike samples from other environments, the analysis of atmospheric samples faces recurring challenges2 such as very small sample volume and mass (here, typically between 10 and 100 &#956;g) and chemical complexity (mixtures of salts, minerals, and numerous organics). To overcome these challenges and improve the understanding of aerosol surfactants some methods have been recently developed by our group to 1) extract specifically these compounds from atmospheric aerosol samples, 2) determine their absolute concentrations in the aerosol phase and 3) determine their surface tension curves in water, including their Critical Micelle Concentration (CMC), the concentration at which the surfactants are saturated at the surface and start to form micelles in the bulk. The latest versions of these methods are presented in this paper.
Further improvements and other types of characterizations, that could be used in complement to those presented, will be discussed. Recent applications of these methods have already shown how such analyses can improve the understanding of the role of surfactants in cloud formation, by evidencing this role itself,3 determining the surfactant concentrations in atmospheric aerosols3,4,5,6 and mode of action in cloud droplet formation,3,6 evidencing their biogenic origin,3,4,7 and explaining their lack of observation by classical instruments.8,9,10

<table border="0" cellpadding="0" cellspacing="0" width="1448">
	<tbody>
		<tr height="24">
			<td height="24" style="height:24px;width:828px;">Quartz filters</td>
			<td style="width:219px;">Fioroni</td>
			<td style="width:235px;"></td>
			<td style="width:167px;">for example &#216;47mm or &#216;150mm, Grammage 85g/m2</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:828px;">Aluminium foils or glass Petri dishes</td>
			<td style="width:219px;"></td>
			<td style="width:235px;"></td>
			<td>backed in oven (773 K, 6h)</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:828px;">Tweezers, scissors</td>
			<td style="width:219px;"></td>
			<td style="width:235px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:828px;">Desiccator</td>
			<td style="width:219px;"></td>
			<td style="width:235px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:828px;">SPE (Solid Phase Extraction) set-up</td>
			<td style="width:219px;"></td>
			<td style="width:235px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:828px;">SPE vacuum manifold Ac-Elut</td>
			<td style="width:219px;">Varian&#160;</td>
			<td></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:828px;">Pump Laboxat</td>
			<td style="width:219px;">Knf LAB</td>
			<td></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:828px;">Nitrogen dryer set-up</td>
			<td style="width:219px;">hand-made</td>
			<td></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:828px;">Compressed Nirogen 4.5 in bottle B50, 200 bar at 15&#176;C</td>
			<td style="width:219px;">Linde</td>
			<td></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:828px;">Tensiometer</td>
			<td>Dataphysics&#160;</td>
			<td style="width:235px;">&#160;OCA 15EC</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:828px;">Software</td>
			<td style="width:219px;"></td>
			<td style="width:235px;">SCA software for OCA version 4-4.1</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:828px;">UV-Vis spectrometer</td>
			<td>Agilent</td>
			<td style="width:235px;">8453</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:828px;">Stir-plates</td>
			<td style="width:219px;"></td>
			<td style="width:235px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:828px;">Glassware</td>
			<td style="width:219px;"></td>
			<td style="width:235px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:828px;">Glass Petri dishes</td>
			<td style="width:219px;"></td>
			<td style="width:235px;"></td>
			<td>for the water extraction step</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Beakers</td>
			<td style="width:219px;"></td>
			<td style="width:235px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">15 mL, 30 mL, 60 mL glass bottles with corks</td>
			<td style="width:219px;"></td>
			<td style="width:235px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Tubes for SPE</td>
			<td style="width:219px;"></td>
			<td style="width:235px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Magnetic stirring bars</td>
			<td style="width:219px;"></td>
			<td style="width:235px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:828px;">Ultrasound bath</td>
			<td style="width:219px;"></td>
			<td style="width:235px;"></td>
			<td>for glassware washing</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:828px;">Micropipettes (0.5 - 5 mL, 0.100 - 1mL, 10 - 100 &#956;L)</td>
			<td style="width:219px;">Rainin Pipette-Life XLS</td>
			<td style="width:235px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:828px;">Disposable small&#160; equipment</td>
			<td style="width:219px;"></td>
			<td style="width:235px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:828px;">Syringe filters 0.40&#956;m PVDF</td>
			<td>Fisherbrand</td>
			<td style="width:235px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:828px;">SPE C18 cartridges Strata C18-E cartridges 500 mg / 3 mL&#160;</td>
			<td style="width:219px;">Phenomenex</td>
			<td style="width:235px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Plastic syringes</td>
			<td style="width:219px;"></td>
			<td style="width:235px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Needles</td>
			<td style="width:219px;"></td>
			<td style="width:235px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">4 mL-vials</td>
			<td style="width:219px;"></td>
			<td style="width:235px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Pasteur glass pipettes</td>
			<td style="width:219px;"></td>
			<td style="width:235px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Micropipette tips</td>
			<td style="width:219px;"></td>
			<td style="width:235px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:828px;">Chemicals</td>
			<td style="width:219px;"></td>
			<td style="width:235px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Sodium dodecyl sulfate (SDS) &#8805; 98.5 % Bioreagent</td>
			<td>Sigma- Aldrich</td>
			<td style="width:235px;">L3771</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Dioctyl sulfosuccinate sodium salt (AOT) &#8805; 97%</td>
			<td>Sigma- Aldrich</td>
			<td style="width:235px;">323586</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Benzyltetradecyldimethylammonium (zephiramine)&#160; &#8805; 99.0 % anhydrous Fluka</td>
			<td>Sigma- Aldrich</td>
			<td style="width:235px;">13401</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Cetyltrimethylammonium chloride solution (CTAC) 25 wt % in H2O</td>
			<td>Sigma- Aldrich</td>
			<td style="width:235px;">292737</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">(1,1,3,3-tetramethylbutyl)phenyl-polyethylene glycol (Triton X114) laboratory grade</td>
			<td>Sigma- Aldrich</td>
			<td style="width:235px;">X114</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Polyethylene glycol dodecyl ether (Brij35) Fluka Bio Chemika</td>
			<td>Sigma- Aldrich</td>
			<td style="width:235px;">858366</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">L-&#945;-phosphatidylcholine from egg yolk type XVI-E&#160; lyophilized powder &#8805; 99 %</td>
			<td>Sigma- Aldrich</td>
			<td style="width:235px;">P3556</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Surfactin from Bacillus subtilis &#8805; 98 %</td>
			<td>Sigma- Aldrich</td>
			<td style="width:235px;">S3523</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">R-95Dd rhamnolipid (95 % dirhamnolipid, 5 % monorhamnolipid)&#160;</td>
			<td>Sigma- Aldrich</td>
			<td style="width:235px;">L510025</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Ethyl violet cationic triarylmethane dye</td>
			<td>Sigma- Aldrich</td>
			<td style="width:235px;">228842</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Patent Blue VF dye content 50 %</td>
			<td>Sigma-Aldrich</td>
			<td style="width:235px;">198218</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Ammonium thiocyanate &#8805; 99 % puriss. p.a.,&#160; ACS reagent</td>
			<td>Sigma-Aldrich</td>
			<td style="width:235px;">31120</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Cobalt(II) nitrate hexahydrate &#8805; 98 % ACS reagent</td>
			<td>Sigma-Aldrich</td>
			<td style="width:235px;">239267</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Acetic anhydride &#8805; 99 % ReagentPlus</td>
			<td>Sigma-Aldrich</td>
			<td style="width:235px;">320102</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Sodium acetate &#8805; 99.0 % anhydrous Reagent Plus</td>
			<td>Sigma-Aldrich</td>
			<td style="width:235px;">S8750</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Ethylenediaminetetraacetic acid 99.4&#8722; 100.6 % ACS reagent powder</td>
			<td>Sigma-Aldrich</td>
			<td style="width:235px;">E9884</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Sodium sulfate anhydrous &#8805; 99.0 % granulated puriss. p.a. ACS reagent Fluka</td>
			<td>Sigma-Aldrich</td>
			<td style="width:235px;">71960</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Ethanol puriss. p.a. ACS Reagent&#160; reag. Ph. Eur. 96% (v/v)</td>
			<td>Sigma-Aldrich</td>
			<td style="width:235px;">32294</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;">Acetonitrile&#160; &#8805; 99.9 % HiPerSolv CHROMANORM Reag. Ph. Eur. (European Pharmacopoeia Reagent) grade gradient for HPLC</td>
			<td>VWR BDH Prolabo</td>
			<td>20060.32</td>
			<td style="width:167px;">to be manipulated under hood</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;">Chloroform 99 % stable with 0.8&#8722;1 % ethanol</td>
			<td>Alfa Aesar</td>
			<td style="width:235px;">L13200-0F</td>
			<td style="width:167px;">to be manipulated under hood</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;">Toluene &#62; 99 %</td>
			<td>Chimie Plus</td>
			<td style="width:235px;">24053</td>
			<td style="width:167px;">to be manipulated under hood</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Denatured ethanol for washing</td>
			<td style="width:219px;"></td>
			<td style="width:235px;"></td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:828px;">Ultra-Pure water</td>
			<td style="width:219px;">Ultrapure water system Purelab Classic, Elga</td>
			<td style="width:235px;"></td>
			<td></td>
		</tr>
	</tbody>
</table>

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.

Note: Before being applied to atmospheric samples, all the protocols presented in this section have been tested with 9 reference surfactants and the surface tension curves, minimum surface tensions, and CMCs obtained were in excellent agreement with the literature.21,22
1. Concentrations
Fine aerosols (&#60;1 &#956;m in diameter, or &#34;PM1&#34;) samples were collected on Quartz fiber filters at the coastal site of Rogoznica, Croatia in February 2015. These samples were handled and extracted as described in Sections 2 and 3, respectively, of this manuscript. The concentrations for anionic, cationic and non-ionic surfactants and the total surfactant concentration in the aerosol sample volume, Csurf,p (M), were measured according to Section 4. The results are presented in Figure 1, and evidence the dominance of anionic and non-ionic surfactants among the surfactants measured.
2. Surface Tension of Sample and Surface Tension Curve for Extracted Surfactants
Combining surface tension measurements as described in Section 5, and the concentration measurements, resulted in absolute surface tension curves for the same samples, as shown in Figure 2. These curves indicate the surfactant concentration in the aerosol sample and the surface tension of these samples (&#34;&#963;min&#34;) and allow to determine graphically the CMC values (Figure 2).
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/55622/55622fig1.jpg" /> 
Figure 1: Surfactant concentrations in fine aerosols (PM1) collected in Rogoznica, Croatia. Concentrations for anionic (in blue), cationic (in red), non-ionic surfactants (in green) and total surfactant concentration in the aerosol phase (sum of each surfactant concentrations), Csurf,p (M), measured with the colorimetric method in fine (&#60;1 &#956;m) atmospheric aerosols collected at the coastal site of Rogoznica, Croatia in February 2015. The results clearly show the dominance of anionic and non-ionic surfactants. <a href="http://cloudflare.jove.com/files/ftp_upload/55622/55622fig1large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/55622/55622fig2.jpg" /> 
Figure 2: Typical surface tension curve and CMC for the surfactants in aerosols from Rogoznica, Croatia. Absolute surface tension curve for the surfactants in the sample of 03/02/2015 obtained by combining the surface tension and concentration measurements. The black dots represent the measured surface tension of the surfactant extract. The orange dot at the end of the curves represents the calculated concentration in the aerosol sample (step 4.4.6), and &#34;&#963;min&#34; its surface tension. The graphical determination of the CMC is illustrated. <a href="http://cloudflare.jove.com/files/ftp_upload/55622/55622fig2large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>

Watch this Scientific Journal Video about Extraction and Characterization of Surfactants from Atmospheric Aerosols at JoVE.com

Extraction and Characterization of Surfactants from Atmospheric Aerosols

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 ...

extraction-characterization-surfactants-from-atmospheric

Research

JoVE Journal

Environment

16.7K Views.  IRCELYON, F-69626. 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).

Video: Extraction and Characterization of Surfactants from Atmospheric Aerosols

Exploring the Effects of Atmospheric Forcings on Evaporation: Experimental Integration of the Atmospheric Boundary Layer and Shallow Subsurface

Evaporation is directly influenced by the interactions between the atmosphere, land surface and soil subsurface. This work aims to experimentally study evaporation under various surface boundary conditions to improve our current understanding and characterization of this multiphase phenomenon as well as to validate numerical heat and mass transfer theories that couple Navier-Stokes flow in the atmosphere and Darcian flow in the porous media. Experimental data were collected using a unique soil tank apparatus interfaced with a small climate controlled wind tunnel. The experimental apparatus was instrumented with a suite of state of the art sensor technologies for the continuous and autonomous collection of soil moisture, soil thermal properties, soil and air temperature, relative humidity, and wind speed. This experimental apparatus can be used to generate data under well controlled boundary conditions, allowing for better control and gathering of accurate data at scales of interest not feasible in the field. Induced airflow at several distinct wind speeds over the soil surface resulted in unique behavior of heat and mass transfer during the different evaporative stages.

A protocol for the design and construction of a soil tank interfaced to a small climate controlled wind tunnel to study the effects of atmospheric forcings on evaporation is presented. Both the soil tank and wind tunnel are instrumented with sensor technologies for the continuous in situ measurement of environmental conditions.

Evaporation is directly influenced by the interactions between the atmosphere, land surface and soil subsurface. This work aims to experimentally study ...

Simultaneous DNA-RNA Extraction from Coastal Sediments and Quantification of 16S rRNA Genes and Transcripts by Real-time PCR

Real Time Polymerase Chain Reaction also known as quantitative PCR (q-PCR) is a widely used tool in microbial ecology to quantify gene abundances of taxonomic and functional groups in environmental samples. Used in combination with a reverse transcriptase reaction (RT-q-PCR), it can also be employed to quantify gene transcripts. q-PCR makes use of highly sensitive fluorescent detection chemistries that allow quantification of PCR amplicons during the exponential phase of the reaction. Therefore, the biases associated with &#39;end-point&#39; PCR detected in the plateau phase of the PCR reaction are avoided. A protocol to quantify bacterial 16S rRNA genes and transcripts from coastal sediments via real-time PCR is provided. First, a method for the co-extraction of DNA and RNA from coastal sediments, including the additional steps required for the preparation of DNA-free RNA, is outlined. Second, a step-by-step guide for the quantification of 16S rRNA genes and transcripts from the extracted nucleic acids via q-PCR and RT-q-PCR is outlined. This includes details for the construction of DNA and RNA standard curves. Key considerations for the use of RT-q-PCR assays in microbial ecology are included.

A protocol to quantify bacterial 16S rRNA genes and transcripts from coastal sediments via real-time PCR is provided. The methodology includes the co-extraction of DNA and RNA; preparation of DNA-free RNA; and 16S rRNA gene and transcript quantification via RT-q-PCR, including standard curve construction.

Real Time Polymerase Chain Reaction also known as quantitative PCR (q-PCR) is a widely used tool in microbial ecology to quantify gene abundances of ...

Laboratory Simulation of an Iron(II)-rich Precambrian Marine Upwelling System to Explore the Growth of Photosynthetic Bacteria

A conventional concept for the deposition of some Precambrian Banded Iron Formations (BIF) proceeds on the assumption that ferrous iron [Fe(II)] upwelling from hydrothermal sources in the Precambrian ocean was oxidized by molecular oxygen [O2] produced by cyanobacteria. The oldest BIFs, deposited prior to the Great Oxidation Event (GOE) at about 2.4 billion years (Gy) ago, could have formed by direct oxidation of Fe(II) by anoxygenic photoferrotrophs under anoxic conditions. As a method for testing the geochemical and mineralogical patterns that develop under different biological scenarios, we designed a 40 cm long vertical flow-through column to simulate an anoxic Fe(II)-rich marine upwelling system representative of an ancient ocean on a lab scale. The cylinder was packed with a porous glass bead matrix to stabilize the geochemical gradients, and liquid samples for iron quantification could be taken throughout the water column. Dissolved oxygen was detected non-invasively via optodes from the outside. Results from biotic experiments that involved upwelling fluxes of Fe(II) from the bottom, a distinct light gradient from top, and cyanobacteria present in the water column, show clear evidence for the formation of Fe(III) mineral precipitates and development of a chemocline between Fe(II) and O2. This column allows us to test hypotheses for the formation of the BIFs by culturing cyanobacteria (and in the future photoferrotrophs) under simulated marine Precambrian conditions. Furthermore we hypothesize that our column concept allows for the simulation of various chemical and physical environments &#8212; including shallow marine or lacustrine sediments.

Laboratory Simulation of an IronII-rich Precambrian Marine Upwelling System to Explore the Growth of Photosynthetic Bacteria

We simulated a Precambrian ferruginous marine upwelling system in a lab-scale vertical flow-through column. The goal was to understand how geochemical profiles of O2 and Fe(II) evolve as cyanobacteria produce O2. The results show the establishment of a chemocline due to Fe(II) oxidation by photosynthetically produced O2.

A conventional concept for the deposition of some Precambrian Banded Iron Formations (BIF) proceeds on the assumption that ferrous iron [Fe(II)] upwelling ...

Extraction of Structural Extracellular Polymeric Substances from Aerobic Granular Sludge

To evaluate and develop methodologies for the extraction of gel-forming extracellular polymeric substances (EPS), EPS from aerobic granular sludge (AGS) was extracted using six different methods (centrifugation, sonication, ethylenediaminetetraacetic acid (EDTA), formamide with sodium hydroxide (NaOH), formaldehyde with NaOH and sodium carbonate (Na2CO3) with heat and constant mixing). AGS was collected from a pilot wastewater treatment reactor. The ionic gel-forming property of the extracted EPS of the six different extraction methods was tested with calcium ions (Ca2+). From the six extraction methods used, only the Na2CO3 extraction could solubilize the hydrogel matrix of AGS. The alginate-like extracellular polymers (ALE) recovered with this method formed ionic gel beads with Ca2+. The Ca2+-ALE beads were stable in EDTA, formamide with NaOH and formaldehyde with NaOH, indicating that ALE are one part of the structural polymers in EPS. It is recommended to use an extraction method that combines physical and chemical treatment to solubilize AGS and extract structural EPS.

The protocol provides a methodology to solubilize aerobic granular sludge in order to extract alginate-like extracellular polymers (ALE).

To evaluate and develop methodologies for the extraction of gel-forming extracellular polymeric substances (EPS), EPS from aerobic granular sludge (AGS) ...

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. ...

Extraction of Organochlorine Pesticides from Plastic Pellets and Plastic Type Analysis

Plastic resin pellets, categorized as microplastics (&#8804;5 mm in diameter), are small granules that can be unintentionally released to the environment during manufacturing and transport. Because of their environmental persistence, they are widely distributed in the oceans and on beaches all over the world. They can act as a vector of potentially toxic organic compounds (e.g., polychlorinated biphenyls) and might consequently negatively affect marine organisms. Their possible impacts along the food chain are not yet well understood. In order to assess the hazards associated with the occurrence of plastic pellets in the marine environment, it is necessary to develop methodologies that allow for rapid determination of associated organic contaminant levels. The present protocol describes the different steps required for sampling resin pellets, analyzing adsorbed organochlorine pesticides (OCPs) and identifying the plastic type. The focus is on the extraction of OCPs from plastic pellets by means of a pressurized fluid extractor (PFE) and on the polymer chemical analysis applying Fourier Transform-InfraRed (FT-IR) spectroscopy. The developed methodology focuses on 11 OCPs and related compounds, including dichlorodiphenyltrichloroethane (DDT) and its two main metabolites, lindane and two production isomers, as well as the two biologically active isomers of technical endosulfan. This protocol constitutes a simple and rapid alternative to existing methodology for evaluating the concentration of organic contaminants adsorbed on plastic pieces.

Microplastics act as vector of potentially toxic organic contaminants with unpredictable effects. This protocol describes an alternative methodology for assessing the levels of organochlorine pesticides adsorbed on plastic pellets and identifying the polymer chemical structure. The focus is on pressurized fluid extraction and attenuated total reflectance Fourier transform infrared spectroscopy.

Plastic resin pellets, categorized as microplastics (&#8804;5 mm in diameter), are small granules that can be unintentionally released to the environment ...

Experimental Methods of Dust Charging and Mobilization on Surfaces with Exposure to Ultraviolet Radiation or Plasmas

Electrostatic dust transport has been hypothesized to explain a number of observations of unusual planetary phenomena. Here, it is demonstrated using three recently developed experiments in which dust particles are exposed to thermal plasma with beam electrons, beam electrons only, or ultraviolet (UV) radiation only. The UV light source has a narrow bandwidth in wavelength centered at 172 nm. The beam electrons with the energy of 120 eV are created with a negatively biased hot filament. When the vacuum chamber is filled with the argon gas, a thermal plasma is created in addition to the electron beam. Insulating dust particles of a few tens of microns in diameter are used in the experiments. Dust particles are recorded to be lofted to a height up to a few centimeters with a launch speed up to 1 m/s. These experiments demonstrate that photo and/or secondary electron emission from a dusty surface changes the charging mechanism of dust particles. According to the recently developed &#34;patched charge model&#34;, the emitted electrons can be re-absorbed inside microcavities between neighboring dust particles below the surface, causing the accumulation of enhanced negative charges on the surrounding dust particles. The repulsive forces between these negatively charged particles may be large enough to mobilize and lift them off the surface. These experiments present the advanced understanding of dust charging and transport on dusty surfaces, and laid a foundation for future investigations of its role in the surface evolution of airless planetary bodies.

Dust charging and mobilization is demonstrated in three experiments with exposure to thermal plasma with beam electrons, beam electrons only, or ultraviolet (UV) radiation only. These experiments present the advanced understanding of electrostatic dust transport and its role in shaping the surfaces of airless planetary bodies.

Electrostatic dust transport has been hypothesized to explain a number of observations of unusual planetary phenomena. Here, it is demonstrated using ...

In Situ Hybridization Techniques for Paraffin-Embedded Adult Coral Samples

Corals are important ocean invertebrates that are critical for overall ocean health as well as human health. However, due to human impacts such as rising ocean temperatures and ocean acidification, corals are increasingly under threat. To tackle these challenges, advances in cell and molecular biology have proven to be crucial for diagnosing the health of corals. Modifying some of the techniques commonly used in human medicine could greatly improve researchers&#39; ability to treat and save corals. To address this, a protocol for in situ hybridization used primarily in human medicine and evolutionary developmental biology has been adapted for use in adult corals under stress.
The purpose of this method is to visualize the spatial expression of an RNA probe in adult coral tissue that has been embedded in paraffin and sectioned onto glass slides. This method focuses on removal of the paraffin and rehydration of the sample, pretreatment of the sample to ensure permeability of the sample, pre-hybridization incubation, hybridization of the RNA probe, and visualization of the RNA probe. This is a powerful method when using non-model organisms to discover where specific genes are expressed, and the protocol can be easily adapted for other non-model organisms. However, the method is limited in that it is primarily qualitative, because expression intensity can vary depending on the amount of time used during the visualization step and the concentration of the probe. Furthermore, patience is required, as this protocol can take up to 5 days (and in many cases, longer) depending on the probe being used. Finally, non-specific background staining is common, but this limitation can be overcome.

In Situ Hybridization Techniques for Paraffin-Embedded Adult Coral Samples

The goal of this protocol is to perform in situ hybridization on adult coral samples that have been embedded in paraffin and sectioned onto glass slides. This is a qualitative method used to visualize the spatial expression of an RNA anti-sense probe in paraffin-embedded tissues.

Corals are important ocean invertebrates that are critical for overall ocean health as well as human health. However, due to human impacts such as rising ...

Sampling, Sorting, and Characterizing Microplastics in Aquatic Environments with High Suspended Sediment Loads and Large Floating Debris

The ubiquitous presence of plastic debris in the ocean is widely recognized by the public, scientific communities, and government agencies. However, only recently have microplastics in freshwater systems, such as rivers and lakes, been quantified. Microplastic sampling at the surface usually consists of deploying drift nets behind either a stationary or moving boat, which limits the sampling to environments with low levels of suspended sediments and floating or submerged debris. Previous studies that employed drift nets to collect microplastic debris typically used nets with &#8805;300 &#181;m mesh size, allowing plastic debris (particles and fibers) below this size to pass through the net and elude quantification. The protocol detailed here enables: 1) sample collection in environments with high suspended loads and floating or submerged debris and 2) the capture and quantification of microplastic particles and fibers &lt;300 &#181;m. Water samples were collected using a peristaltic pump in low-density polyethylene (PE) containers to be stored before filtering and analysis in the lab. Filtration was done with a custom-made microplastic filtration device containing detachable union joints that housed nylon mesh sieves and mixed cellulose ester membrane filters. Mesh sieves and membrane filters were examined with a stereomicroscope to quantify and separate microplastic particulates and fibers. These materials were then examined using a micro-attenuated total reflectance Fourier transform infrared spectrometer (micro ATR-FTIR) to determine microplastic polymer type. Recovery was measured by spiking samples using blue PE particulates and green nylon fibers; percent recovery was determined to be 100% for particulates and 92% for fibers. This protocol will guide similar studies on microplastics in high velocity rivers with high concentrations of sediment. With simple modifications to the peristaltic pump and filtration device, users can collect and analyze various sample volumes and particulate sizes.

Most microplastic research to date has occurred in marine systems where suspended solid levels are relatively low. Focus is now shifting to freshwater systems, which may feature high sediment loads and floating debris. This protocol addresses collecting and analyzing microplastic samples from aquatic environments that contain high suspended solid loads.

The ubiquitous presence of plastic debris in the ocean is widely recognized by the public, scientific communities, and government agencies. However, only ...

Design and Use of an Apparatus for Quantifying Bivalve Suspension Feeding at Sea

As shellfish aquaculture moves from coastal embayments and estuaries to offshore locations, the need to quantify ecosystem interactions of farmed bivalves (i.e., mussels, oysters, and clams) presents new challenges. Quantitative data on the feeding behavior of suspension-feeding mollusks is necessary to determine important ecosystem interactions of offshore shellfish farms, including their carrying capacity, the competition with the zooplankton community, the availability of trophic resources at different depths, and the deposition to the benthos. The biodeposition method is used to quantify feeding variables in suspension-feeding bivalves in a natural setting and represents a more realistic proxy than laboratory experiments. This method, however, relies upon a stable platform to satisfy the requirements that water flow rates supplied to the shellfish remain constant and the bivalves are undisturbed. A flow-through device and process for using the biodeposition method to quantify the feeding of bivalve mollusks were modified from a land-based format for shipboard use by building a two-dimensional gimbal table around the device. Planimeter data reveal a minimal pitch and yaw of the chambers containing the test shellfish despite boat motion, the flow rates within the chambers remain constant, and operators are able to collect the biodeposits (feces and pseudofeces) with sufficient consistency to obtain accurate measurements of the bivalve clearance, filtration, selection, ingestion, rejection, and absorption at offshore shellfish aquaculture sites.

A flow-through device for using the biodeposition method to quantify filtration and feeding behavior of bivalve mollusks was modified for shipboard use. A two-dimensional gimbal table built around the device isolates the apparatus from boat motion, thereby allowing the accurate quantification of bivalve filtration variables at offshore shellfish aquaculture sites.

As shellfish aquaculture moves from coastal embayments and estuaries to offshore locations, the need to quantify ecosystem interactions of farmed bivalves ...

Extraction and Characterization of Surfactants from Atmospheric Aerosols

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Sampling, Sorting, and Characterizing Microplastics in Aquatic Environments with High Suspended Sediment Loads and Large Floating Debris

Design and Use of an Apparatus for Quantifying Bivalve Suspension Feeding at Sea