This work was financially supported by the Natural Science Funds for Distinguished Young Scholar of Guangdong Province, China, No. 2020B151502094; National Natural Science Foundation of China, No. 21777045 and 22106064; Foundation of Shenzhen Science, Technology and Innovation Commission, China, JCYJ20200109141625078; 2019 youth innovation project of Guangdong universities and colleges, China, No. 2019KQNCX133 and a special fund for the science and technology innovation strategy of Guangdong Province (PDJH2021C0033). This work was sponsored by the Shenzhen Key Laboratory of Interfacial Science and Engineering of Materials (No. ZDSYS20200421111401738), Guangdong Provincial Key Laboratory of Soil and Groundwater Pollution Control (2017B030301012), and State Environmental Protection Key Laboratory of Integrated Surface Water-Groundwater Pollution Control. In particular, we acknowledge the technical support from the SUSTech Core Research Facilities.

1. Raw material collection and treatment
<ol>
	<li>Red soil collection
	<ol>
		<li>Collect the red soil. Remove the 30 cm top layer of the soil containing plants and residual organic matter. 
		NOTE: In this experiment, the red soil was collected at the campus of Southern University of Science and Technology (SUSTech), Shenzhen, Guangdong, China (113&#176;59&#39; E, 22&#176;36&#39; N).</li>
	</ol>
	</li>
	<li>Red soil treatment
	<ol>
		<li>Air-dry the collected red soil at room temperature and filter it through a 30-mesh sieve. Remove most of the large stones and leaves. Measure the heavy metal(loid) concentration (Table 1) in the red soil with inductively coupled plasma mass spectrometry (ICP-MS)16 to make sure that there is no unwanted pollution introduced. 
		NOTE: A sieve with small holes is recommended since few large non-silicon or aluminum-containing objects will be in the raw material. Here, a 30-mesh sieve is sufficient to treat the raw material in this experiment.</li>
	</ol>
	</li>
</ol>
2. Fe2O3/FAU-type zeolite synthesis
<ol>
	<li>Preparation of alkali mixture powder
	<ol>
		<li>Weigh 5 g of pretreated red soil, 1 g of SiO2, and 7.63 g of NaOH, and add them to a natural agate mortar. Grind them for 2-3 min into a fine powder. Ensure the relative humidity in the laboratory is 65%-72%. 
		NOTE: Be careful of the grinding time since NaOH is very hygroscopic. It can easily absorb water from the air atmosphere. A medium-moist alkali powder is crucial for the next step of the experiment. The grinding time is related to the humidity in the laboratory.</li>
	</ol>
	</li>
	<li>Alkali fusion/activation
	<ol>
		<li>Transfer the alkali mixture into a 100 mL Teflon reactor liner without the stainless steel outer covering. Heat it in a 200 &#176;C oven for 1 h. 
		NOTE: The purpose of this step is to make use of the strong base NaOH to activate the Si-O bond and Al-O bond17 so that the Al, Si, and O atoms reassemble to form the desired aluminosilicate zeolite.</li>
	</ol>
	</li>
	<li>Preparation of zeolite precursor
	<ol>
		<li>Add 60 mL of deionized water into the Teflon reactor liner containing the activated alkali mixture. Add a stir bar of the appropriate size and stir the mixture at 600 rpm on the magnetic stirrer for 3 h at 25 &#176;C. Wait for a homogeneous gel to be formed as the zeolite precursor18.</li>
	</ol>
	</li>
	<li>Crystallization
	<ol>
		<li>Transfer the homogeneous gel into a 100 mL stainless steel autoclave and heat the gel in a 100 &#176;C oven for 12 h. Wait until the oven cools to room temperature following the default cooling program to open the oven&#39;s door and take the autoclave out. 
		NOTE: The autoclave generates high pressure under high temperatures to boost the crystallization process. Always wait for it to reach room temperature to prevent a high pressure-generated explosion.</li>
	</ol>
	</li>
	<li>Wash the obtained zeolite with deionized water several times until the solution pH is close to 7. Use a centrifuge to separate the solid and liquid, and collect the solid at the bottom of the 50 mL centrifuge tube. Finally, dry the obtained product for 8 h in an 80 &#176;C oven and grind it into&#160;fine powder for subsequent characterization.</li>
	<li>Characterization
	<ol>
		<li>Acquire the X-ray fluorescence- (XRF) spectrometer result for the red soil (Figure 2). It is used to accurately measure the soil&#39;s inorganic element concentration19.</li>
		<li>Acquire the crystal information file (CIF) of Fe2O3 from the Inorganic Crystal Structure Database (ICSD). Acquire the CIF file of FAU-type zeolite from the Database of Zeolite Structures. 
		NOTE: Mercury and Materials Studio (MS) can both be used as crystal structure visualization tools. In this work, Mercury was used for the visualization of the Fe2O3 structure, and MS was used for the FAU-type zeolite (Figure 3).</li>
		<li>Acquire a powder X-ray diffraction (PXRD) pattern to confirm the phase of the as-synthesized Fe2O3/FAU-type zeolite composite material (Figure 4)20. Compare it with the simulated PXRD pattern of Fe2O3 and FAU-type zeolite using JADE 6.5 software. 
		NOTE: The Mercury software developed by the Cambridge Crystallographic Data Centre (CCDC) can calculate the PXRD pattern based on the CIF file of the standard materials obtained from the ICSD-the world&#39;s largest database for completely identified inorganic crystal structures.</li>
		<li>Acquire a scanning electron microscopy (SEM) image (Figure 5) to confirm the morphology20.</li>
		<li>Acquire transmission electron microscope (TEM) energy-dispersive X-ray spectroscopy (EDS) mapping (Figure 6) to determine the chemical composition6. 
		&#8203;NOTE: Compared to SEM-EDS mapping, TEM-EDS mapping can detect low amounts of elemental composition.</li>
	</ol>
	</li>
</ol>
3. Batch adsorption experiment
<ol>
	<li>Prepare 50 mL of 1,000 ppm Cu (II), Cr (III), Cr (VI), As (III), Cd (II), Pb (II), Zn (II), and Ni (II) aqueous solutions. Note the pH of each solution.</li>
	<li>Add 50 mg of zeolite to each heavy metal(loid) solution. Finely adjust the pH of the mixture solution with 0.1 M HCl or 0.1 M NaOH. Stir the mixture at 600 rpm for 48 h at 25 &#176;C. 
	NOTE: Each heavy metal(loid) ion has a stable pH range without the metal hydroxide precipitation. Adjust the pH of the final mixed solution to a pH range so that the decrease in heavy metal(loid) concentration can be attributed to the performance of the zeolite.</li>
	<li>Adjust the pH of the final mixed solutions of Cu (II), Cr (III), Cr (VI), As (III), Cd (II), Pb (II), Zn (II), and Ni (II) to 4.2, 3.9, 6.4, 7.8, 5.8, 5.2, 5.7, and 6.4, respectively.</li>
	<li>Filter the mixed solutions through 0.22 &#181;m membranes. Dilute them 1,000x by adding 2% HNO3 solution.Measure the residual heavy metal(loid) concentrations (Figure 6) with inductively coupled plasma mass spectrometry (ICP-MS)16, with a testing range of 0.001 ppm to 1 ppm. See Table 2 for the ICP-MS operating parameters.</li>
</ol>

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The authors have no conflicts of interest to disclose.

Zeolite is typically an aluminosilicate material. In theory, materials that are rich in silicate and aluminate can be chosen as raw materials for zeolite synthesis. The Si/Al ratio of the raw material must be similar to that of the selected type of zeolite to minimize the usage of additional silicon/aluminum sources6,8,16. The Si/Al ratio of FAU-type zeolite is 1.2, and the Si/Al ratio of red soil is 1.3. Therefore, red soil is ...

Heavy metal(loid)s from anthropogenic and natural activities are ubiquitous in the air, water, and soil environment1. They are of high mobility and toxicity, posing a potential health risk to human beings by direct contact or via food chain transportation2. Water is vital for the life of human beings since it is the feedstock of every family. Restoring water health is crucial. Therefore, it is of great importance to decrease the mobility and bioavailability of toxic heavy metal(loid)s in water. To maintain good health in water, water remediation materials, such as biochar, iron-based materials, and zeolite, play an essential role in immobilizing or removing heavy metal(loid)s from aqueous environments3,4,5.
Zeolites are highly crystalline materials with unique pores and channels in their crystal structures. They are composed of TO4 tetrahedra (T is the central atom, usually Si, Al, or P) connected by shared O atoms. The negative surface charge and exchangeable ions in the pores make it a popular adsorbent for ion capture, which has been extensively used in heavy metal-polluted water and soil remediation. Benefiting from their structures, the remediation mechanisms involved in contaminant removal by zeolites mainly include chemical bonding6, surface electrostatic interaction7, and ion exchange8.
Faujasite (FAU)-type zeolite has relatively large pores, with a maximum pore diameter of 11.24 &#197;. It shows high efficiency and broad applications for contaminant removal9,10. In recent years, extensive research has devoted to developing green and low-cost routines for zeolite synthesis, such as using industrial solid wastes11 as raw material to provide silicon and aluminium sources, or adopting directing agent-free recipes12. The reported&#160;alternative industrial solid wastes that can be silicon and aluminum sources include coal gangue13, fly ash11, waste molecular sieves14, mining and metallurgical wastes15, engineering-abandoned soil8, and agricultural soil6, etc.
Herein, red soil, an abundant and easily obtained silicon and aluminum-rich material, was adopted as the raw material, and a facile green chemistry approach was developed for Fe2O3/FAU-type zeolite composite material synthesis (Figure 1). The detailed synthesis parameters have been finely tuned. The as-synthesized material shows high immobilization capacity for heavy metal-contaminated water remediation. The present study should be instructive for related researchers who are interested in this area to use soil as a raw material for eco-material synthesis.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Chemicals</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Cadmium nitrate tetrahydrate</td>
			<td>Shanghai Aladdin Bio-Chem Technology Co., LTD</td>
			<td>C102676</td>
			<td>AR, 99%. Make 1,000 ppm&#160; stock solution for the test of adsorption performance of zeolite.</td>
		</tr>
		<tr>
			<td>Chromium(III) nitrate nonahydrate</td>
			<td>Shanghai Aladdin Bio-Chem Technology Co., LTD</td>
			<td>C116446</td>
			<td>AR, 99%. Make 1,000 ppm&#160; stock solution for the test of adsorption performance of zeolite.</td>
		</tr>
		<tr>
			<td>Copper sulfate pentahydrate</td>
			<td>Shanghai Aladdin Bio-Chem Technology Co., LTD</td>
			<td>C112396</td>
			<td>AR, 99%. Make 1,000 ppm&#160; stock solution for the test of adsorption performance of zeolite.</td>
		</tr>
		<tr>
			<td>Lead nitrate</td>
			<td>Shanghai Aladdin Bio-Chem Technology Co., LTD</td>
			<td>L112118</td>
			<td>AR, 99%. Make 1,000 ppm stock solution for the test of adsorption performance of zeolite.</td>
		</tr>
		<tr>
			<td>Nickel nitrate hexahydrate</td>
			<td>Shanghai Aladdin Bio-Chem Technology Co., LTD</td>
			<td>N108891</td>
			<td>AR, 98%. Make 1,000 ppm&#160; stock solution for the test of adsorption performance of zeolite.</td>
		</tr>
		<tr>
			<td>Nitric acid</td>
			<td>Shanghai Aladdin Bio-Chem Technology Co., LTD</td>
			<td>N116238</td>
			<td>AR, 69.2%. Used as solvent in ICP-MS test.</td>
		</tr>
		<tr>
			<td>Potassium dichromate</td>
			<td>Shanghai Aladdin Bio-Chem Technology Co., LTD</td>
			<td>P112163</td>
			<td>AR, 99.8%. Make 1,000 ppm&#160; stock solution for the test of adsorption performance of zeolite.</td>
		</tr>
		<tr>
			<td>Silicon dioxide</td>
			<td>Shanghai Aladdin Bio-Chem Technology Co., LTD</td>
			<td>S116482</td>
			<td>AR, 99%. For synthesis of zeolite.</td>
		</tr>
		<tr>
			<td>Sodium (meta)arsenite</td>
			<td>Sigma-aldrich</td>
			<td>S7400-100G</td>
			<td>AR, 90%. Make 1,000 ppm stock solution for the test of adsorption performance of zeolite.</td>
		</tr>
		<tr>
			<td>Sodium hydroxide</td>
			<td>Shanghai Aladdin Bio-Chem Technology Co., LTD</td>
			<td>S111502</td>
			<td>Pellets. For the synthesis of zeolite.</td>
		</tr>
		<tr>
			<td>Zinc nitrate hexahydrate</td>
			<td>Shanghai Aladdin Bio-Chem Technology Co., LTD</td>
			<td>Z111703</td>
			<td>AR, 99%. Make 1,000 ppm&#160; stock solution for the test of adsorption performance of zeolite.</td>
		</tr>
		<tr>
			<td>Equipment</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Air-dry oven</td>
			<td>Shanghai Yiheng Technology Instrument Co.,LTD.</td>
			<td>DHG-9075A</td>
			<td>Used for hydrothermal crystallization and drying of sample</td>
		</tr>
		<tr>
			<td>Analytical balance</td>
			<td>Sartorius Scientific Instruments Co.LTD</td>
			<td>BSA224S-CW</td>
			<td>Used for weighing samples</td>
		</tr>
		<tr>
			<td>Centrifuge tubes</td>
			<td>Nantong Supin Experimental Equipment Co., LTD</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>High speed centrifuge</td>
			<td>Hunan Xiang Yi Laboratory Instrument Development Co.,LTD</td>
			<td>H1850</td>
			<td>Used for separation of solid and liquid samples</td>
		</tr>
		<tr>
			<td>Multipoint magnetic stirrer</td>
			<td>IKA Equipment Co.,LTD.</td>
			<td>RT15</td>
			<td>Used for stirring samples</td>
		</tr>
		<tr>
			<td>Oscillator</td>
			<td>Changzhou Guohua Electric Appliances Co.,LTD.</td>
			<td>SHA-B</td>
			<td>For uniform mixing of samples</td>
		</tr>
		<tr>
			<td>Syringe-driven filter</td>
			<td>Tianjin Jinteng Experimental Equipment Co.,LTD.</td>
			<td></td>
			<td>0.22 &#956;m. For filtration.</td>
		</tr>
		<tr>
			<td>Softwares</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>JADE 6.5</td>
			<td>Materials Data&#38; (MDI)</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Mercury</td>
			<td>Cambridge Crystallographic Data Centre (CCDC)</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Materials Studio</td>
			<td>Accelrys Software Inc.</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Websites</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Database of Zeolite Structures: http://www.iza-structure.org/databases/</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>ICSD: https://icsd.products.fiz-karlsruhe.de/en</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
	</tbody>
</table>

resource recycling of red soil to synthesize fe2o3/fau-type zeolite composite material for heavy metal removal

Heavy metal-polluted water is of great concern to human health and the eco-environment. In situ water remediation techniques enabled by highly efficient adsorption materials are of great importance in these circumstances. Among all the materials used in water remediation, iron-based nanomaterials and porous materials are of great interest, benefiting from their rich redox reactivity and adsorption function. Here, we developed a facile protocol to directly convert the widely spread red soil in south China to fabricate the Fe2O3/faujasite (FAU)-type zeolite composite material. 
The detailed synthesis procedure and synthesis parameters, such as reaction temperature, reaction time, and the Si/Al ratio in the raw materials, have been carefully tuned. The as-synthesized composite materials show good adsorption capacity for typical heavy metal(loid) ions. With 0.001 g/mL Fe2O3/FAU-type zeolite composite material added to different heavy metal(loid)-polluted aqueous solutions (single type of heavy metal(loid) concentration: 1,000 mg/L [ppm]), the adsorption capacity was shown to be 172, 45, 170, 40, 429, 693, 94, and 133 mg/g for Cu (II), Cr (III), Cr (VI), As (III), Cd (II), Pb (II), Zn (II), and Ni (II) removal, respectively, which can be further expanded for heavy metal-polluted water and soil remediation.

Figure 1 illustrates the overall synthesis route of zeolite based on the &#34;soil for soil remediation&#34; strategy6. With a simple organic-free route, red soil can be converted to Fe2O3/FAU-type zeolite composite material without adding any Fe or Al source. The as-synthesized zeolite composite material exhibits excellent removal capacity for heavy metal-polluted water remediation and can be used for soil remediation.
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Watch this Scientific Journal Video about Resource Recycling of Red Soil to Synthesize Fe2O3/FAU-type Zeolite Composite Material for Heavy Metal Removal at JoVE.com

Resource Recycling of Red Soil to Synthesize Fe2O3/FAU-type Zeolite Composite Material for Heavy Metal Removal

This article presents a novel and convenient route to synthesize Fe2O3/faujasite (FAU)-type zeolite composite material from red soil. The detailed synthesis parameters have been finely tuned. The obtained composite material can be used for efficient heavy metal-contaminated water remediation, indicating its potential applications in environmental engineering.

Resource Recycling of Red Soil to Synthesize Fe2O3/FAU-type Zeolite Composite Material for Heavy Metal Removal

Heavy metal-polluted water is of great concern to human health and the eco-environment. In situ water remediation techniques enabled by highly efficient ...

resource-recycling-red-soil-to-synthesize-fe2o3fau-type-zeolite

Research

JoVE Journal

Environment

2.7K Views.  Southern University of Science and Technology. This article presents a novel and convenient route to synthesize Fe2O3/faujasite (FAU)-type zeolite composite material from red soil. The detailed synthesis parameters have been finely tuned. The obtained composite material can be used for efficient heavy metal-contaminated water remediation, indicating its potential applications in environmental engineering. 

Video: Resource Recycling of Red Soil to Synthesize Fe2O3/FAU-type Zeolite Composite Material for Heavy Metal Removal

High-throughput Fluorometric Measurement of Potential Soil Extracellular Enzyme Activities

Microbes in soils and other environments produce extracellular enzymes to depolymerize and hydrolyze organic macromolecules so that they can be assimilated for energy and nutrients. Measuring soil microbial enzyme activity is crucial in understanding soil ecosystem functional dynamics. The general concept of the fluorescence enzyme assay is that synthetic C-, N-, or P-rich substrates bound with a fluorescent dye are added to soil samples. When intact, the labeled substrates do not fluoresce. Enzyme activity is measured as the increase in fluorescence as the fluorescent dyes are cleaved from their substrates, which allows them to fluoresce. Enzyme measurements can be expressed in units of molarity or activity. To perform this assay, soil slurries are prepared by combining soil with a pH buffer. The pH buffer (typically a 50 mM sodium acetate or 50 mM Tris buffer), is chosen for the buffer&#39;s particular acid dissociation constant (pKa) to best match the soil sample pH. The soil slurries are inoculated with a nonlimiting amount of fluorescently labeled (i.e. C-, N-, or P-rich) substrate. Using soil slurries in the assay serves to minimize limitations on enzyme and substrate diffusion. Therefore, this assay controls for differences in substrate limitation, diffusion rates, and soil pH conditions; thus detecting potential enzyme activity rates as a function of the difference in enzyme concentrations (per sample).
Fluorescence enzyme assays are typically more sensitive than spectrophotometric (i.e. colorimetric) assays,&#160;but can suffer from interference caused by impurities and the instability of many fluorescent compounds when exposed to light; so caution is required when handling fluorescent substrates. Likewise, this method only assesses potential enzyme activities under laboratory conditions when substrates are not limiting. Caution should be used when interpreting the data representing cross-site comparisons with differing temperatures or soil types, as in situ soil type and temperature can influence enzyme kinetics.

To measure potential rates of soil extracellular enzyme activities, synthetic substrates that are bound to a fluorescent dye are added to soil samples. Enzyme activity is measured as the fluorescent dye is released from the substrate by an enzyme-catalyzed reaction, where higher fluorescence indicates more substrate degradation.

Microbes in soils and other environments produce extracellular enzymes to depolymerize and hydrolyze organic macromolecules so that they can be ...

Design and Operation of a Continuous 13C and 15N Labeling Chamber for Uniform or Differential, Metabolic and Structural, Plant Isotope Labeling

Tracing rare stable isotopes from plant material through the ecosystem provides the most sensitive information about ecosystem processes; from CO2 fluxes and soil organic matter formation to small-scale stable-isotope biomarker probing. Coupling multiple stable isotopes such as 13C with 15N, 18O or&#160;2H has the potential to reveal even more information about complex stoichiometric relationships during biogeochemical transformations. Isotope labeled plant material has been used in various studies of litter decomposition and soil organic matter formation1-4. From these and other studies, however, it has become apparent that structural components of plant material behave differently than metabolic components (i.e. leachable low molecular weight compounds) in terms of microbial utilization and long-term carbon storage5-7. The ability to study structural and metabolic components separately provides a powerful new tool for advancing the forefront of ecosystem biogeochemical studies. Here we describe a method for producing 13C and 15N labeled plant material that is either uniformly labeled throughout the plant or differentially labeled in structural and metabolic plant components.
Here, we present the construction and operation of a continuous 13C and 15N labeling chamber that can be modified to meet various research needs. Uniformly labeled plant material is produced by continuous labeling from seedling to harvest, while differential labeling is achieved by removing the growing plants from the chamber weeks prior to harvest. Representative results from growing Andropogon gerardii Kaw demonstrate the system&#39;s ability to efficiently label plant material at the targeted levels. Through this method we have produced plant material with a 4.4 atom%13C and 6.7 atom%15N uniform plant label, or material that is differentially labeled by up to 1.29 atom%13C and 0.56 atom%15N in its metabolic and structural components (hot water extractable and hot water residual components, respectively). Challenges lie in maintaining proper temperature, humidity, CO2 concentration,&#160;and light levels in an airtight 13C-CO2 atmosphere for successful plant production. This chamber description represents a useful research tool to effectively produce uniformly or differentially multi-isotope labeled plant material for use in experiments on ecosystem biogeochemical cycling.

Design and Operation of a Continuous 13C and 15N Labeling Chamber for Uniform or Differential, Metabolic and Structural, Plant Isotope Labeling

This method explains how to build and operate a continuous 13C and 15N isotope labeling chamber for uniform or differential plant tissue labeling. Representative results from metabolic and structural labeling of Andropogon gerardii are discussed.

Tracing rare stable isotopes from plant material through the ecosystem provides the most sensitive information about ecosystem processes; from CO2 fluxes ...

A Protocol for Conducting Rainfall Simulation to Study Soil Runoff

Rainfall is a driving force for the transport of environmental contaminants from agricultural soils to surficial water bodies via surface runoff. The objective of this study was to characterize the effects of antecedent soil moisture content on the fate and transport of surface applied commercial urea, a common form of nitrogen (N) fertilizer, following a rainfall event that occurs within 24&#160;hr&#160;after fertilizer application. Although urea is assumed to be readily hydrolyzed to ammonium and therefore not often available for transport, recent studies suggest that urea can be transported from agricultural soils to coastal waters where it is implicated in harmful algal blooms. A rainfall simulator was used to apply a consistent rate of uniform rainfall across packed soil boxes that had been prewetted to different soil moisture contents. By controlling rainfall and soil physical characteristics, the effects of antecedent soil moisture on urea loss were isolated. Wetter soils exhibited shorter time from rainfall initiation to runoff initiation, greater total volume of runoff, higher urea concentrations in runoff, and greater mass loadings of urea in runoff. These results also demonstrate the importance of controlling for antecedent soil moisture content in studies designed to isolate other variables, such as soil physical or chemical characteristics, slope, soil cover, management, or rainfall characteristics. Because rainfall simulators are designed to deliver raindrops of similar size and velocity as natural rainfall, studies conducted under a standardized protocol can yield valuable data that, in turn, can be used to develop models for predicting the fate and transport of pollutants in runoff.

A rainfall simulator was used to apply a consistent rate of uniform rainfall to packed soil boxes in a study of the fate and transport of urea, a nonpoint source environmental contaminant. Under uniform soil and rainfall conditions, antecedent soil moisture content exerted strong control over urea loss in surface runoff.

Rainfall is a driving force for the transport of environmental contaminants from agricultural soils to surficial water bodies via surface runoff. The ...

A Gusseted Thermogradient Table to Control Soil Temperatures for Evaluating Plant Growth and Monitoring Soil Processes

Thermogradient tables were first developed in the 1950s primarily to test seed germination over a range of temperatures simultaneously without using a series of incubators. A temperature gradient is passively established across the surface of the table between the heated and cooled ends and is lost quickly at distances above the surface. Since temperature is only controlled on the table surface, experiments are restricted to shallow containers, such as Petri dishes, placed on the table. Welding continuous aluminum vertical strips or gussets perpendicular to the surface of a table enables temperature control in depth via convective heat flow. Soil in the channels between gussets was maintained across a gradient of temperatures allowing a greater diversity of experimentation. The gusseted design was evaluated by germinating oat, lettuce, tomato, and melon seeds. Soil temperatures were monitored using individual, battery-powered dataloggers positioned across the table. LED lights installed in the lids or along the sides of the gradient table create a controlled temperature chamber where seedlings can be grown over a range of temperatures. The gusseted design enabled accurate determination of optimum temperatures for fastest germination rate and the highest percentage germination for each species. Germination information from gradient table experiments can help predict seed germination and seedling growth under the adverse soil conditions often encountered during field crop production. Temperature effects on seed germination, seedling growth, and soil ecology can be tested under controlled conditions in a laboratory using a gusseted thermogradient table.

Traditional thermogradient tables create a range of temperatures across the surface. Welding gussets perpendicular to the surface of a thermogradient table will control temperature in depth increasing possible research applications.

Thermogradient tables were first developed in the 1950s primarily to test seed germination over a range of temperatures simultaneously without using a ...

Protocols for Quantifying Transferable Pesticide Residues in Turfgrass Systems

Plant canopies in established turfgrass systems can intercept an appreciable amount of sprayed pesticides, which can be transferred through various routes onto humans. For this reason, transferable pesticide residue experiments are required for registration and re-registration by the United States Environmental Protection Agency (USEPA). Although such experiments are required, limited specificity is required pertaining to experimental approach. Experimental approaches used to assess pesticide transfer to humans including hand wiping with cotton gloves, modified California roller (moving a roller of known mass over cotton cloth) and soccer ball roll (ball wrapped with sorbent strip) over three treated turfgrass species (creeping bentgrass, hybrid bermudagrass and tall fescue maintained at 0.4, 5 and 9 cm, respectively) are presented. The modified California roller is the most extensively utilized approach to date, and is best suited for use at low mowing heights due to its reproducibility and large sampling area. The soccer ball roll is a less aggressive transfer approach; however, it mimics a very common occurrence in the most popular international sport, and has many implications for nondietary pesticide exposure from hand-to-mouth contact. Additionally, this approach may be adjusted for other athletic activities with limited modification. Hand wiping is the best approach to transfer pesticides at higher mowing heights, as roller-based approaches can lay blades over; however, it is more subjective due to more variable sampling pressure. Utility of these methods across turfgrass species is presented, and additional considerations to conduct transferable pesticide residue research in turfgrass systems are discussed.

Transferable pesticide residue experiments in turfgrass systems are integral components of human risk exposure assessments. Experimental approaches to measure transferable residues should be adjusted to the human interaction of interest and turfgrass system dynamics. Three transferable pesticide residue protocols are presented and the suitability across three turfgrass systems is discussed.

Plant canopies in established turfgrass systems can intercept an appreciable amount of sprayed pesticides, which can be transferred through various routes ...

Determination of Inorganic Arsenic in a Wide Range of Food Matrices using Hydride Generation - Atomic Absorption Spectrometry.

The European Food Safety Authority (EFSA) underlined in its Scientific Opinion on Arsenic in Food that in order to support a sound exposure assessment to inorganic arsenic through diet, information about distribution of arsenic species in various food types must be generated. A method, previously validated in a collaborative trial, has been applied to determine inorganic arsenic in a wide variety of food matrices, covering grains, mushrooms and food of marine origin (31 samples in total). The method is based on detection by flow injection-hydride generation-atomic absorption spectrometry of the iAs selectively extracted into chloroform after digestion of the proteins with concentrated HCl. The method is characterized by a limit of quantification of 10 &#181;g/kg dry weight, which allowed quantification of inorganic arsenic in a large amount of food matrices. Information is provided about performance scores given to results obtained with this method and which were reported by different laboratories in several proficiency tests. The percentage of satisfactory results obtained with the discussed method is higher than that of the results obtained with other analytical approaches.

The usefulness of an analytical method to determine inorganic arsenic in a wide range of food matrices is demonstrated. The method consists of selective extraction of inorganic arsenic into chloroform with a final determination by hydride generation-atomic absorption spectrometry.

The European Food Safety Authority (EFSA) underlined in its Scientific Opinion on Arsenic in Food that in order to support a sound exposure assessment to ...

Nanopore DNA Sequencing for Metagenomic Soil Analysis

This article describes the steps for construction of a DNA library from soil, preparation and use of the nanopore flow cell, and analysis of the DNA sequences identified using computer software. Nanopore DNA sequencing is a flexible technique that allows for rapid microbial genome sequencing to identify bacterial and viral species, to characterize bacterial strains, and to detect genetic mutations that confer resistance to antibiotics. The advantages of nanopore sequencing (NS) for life sciences include its low complexity, reduced cost, and rapid real-time sequencing of purified genomic DNA, PCR amplicons, cDNA samples, or RNA. NS is an example of "strand sequencing" which involves sequencing DNA by guiding a single stranded DNA molecule through a nanopore that is inserted into a synthetic polymer membrane. The membrane has an electrical current applied across it, so as the individual bases pass through the nanopore the electrical current is disrupted to varying degrees by the four nucleotide bases. The identification of each nucleotide occurs by detecting the characteristic modulation of the electrical current by the different bases as they pass through the nanopore. The NS system consists of a handheld, USB powered portable device and a disposable flow cell that contains a nanopore array. The portable device plugs into a standard laptop computer that reads and records the DNA sequence using computer software.

Nanopore technology for sequencing biomolecules has wide applications in the life sciences, including identification of pathogens, food safety monitoring, genomic analysis, metagenomic environmental monitoring, and characterization of bacterial antibiotic resistance. In this article, the procedure for metagenomic soil DNA sequencing for species identification using the nanopore sequencing technology is demonstrated.

This article describes the steps for construction of a DNA library from soil, preparation and use of the nanopore flow cell, and analysis of the DNA ...

Measuring and Mapping Patterns of Soil Erosion and Deposition Related to Soil Carbonate Concentrations Under Agricultural Management

Spatial patterns of soil erosion and deposition can be inferred from differences in ground elevation mapped at appropriate time increments. Such changes in elevation are related to changes in near-surface soil carbonate (CaCO3) profiles. The objective is to describe a simple conceptual model and detailed protocol for repeatable field and laboratory measurements of these quantities. Here, accurate elevation is measured using a ground-based differential global positioning system (GPS); other data acquisition methods could be applied to the same basic method. Soil samples are collected from prescribed depth intervals and analyzed in the lab using an efficient and precise modified pressure-calcimeter method for quantitative analysis of inorganic carbon concentration. Standard statistical methods are applied to point data, and representative results show significant correlations between changes in soil surface layer CaCO3 and changes in elevation consistent with the conceptual model; CaCO3 generally decreased in depositional areas and increased in erosional areas. Maps are derived from point measurements of elevation and soil CaCO3 to aid analyses. A map of erosional and depositional patterns at the study site, a rain-fed winter wheat field cropped in alternating wheat-fallow strips, shows the interacting effects of water and wind erosion affected by management and topography. Alternative sampling methods and depth intervals are discussed and recommended for future work relating soil erosion and deposition to soil CaCO3.

Spatial patterns of soil erosion and deposition can be inferred from differences in ground elevation mapped at appropriate time increments. Such changes in elevation are related to changes in near-surface soil carbonates. Repeatable methods for field and laboratory measurements of these quantities and data analysis methods are described here.

Spatial patterns of soil erosion and deposition can be inferred from differences in ground elevation mapped at appropriate time increments. Such changes ...

Use of Principal Components for Scaling Up Topographic Models to Map Soil Redistribution and Soil Organic Carbon

Landscape topography is a critical factor affecting soil formation and plays an important role in determining soil properties on the earth surface, as it regulates the gravity-driven soil movement induced by runoff and tillage activities. The recent application of Light Detection and Ranging (LiDAR) data holds promise for generating high spatial resolution topographic metrics that can be used to investigate soil property variability. In this study, fifteen topographic metrics derived from LiDAR data were used to investigate topographic impacts on redistribution of soil and spatial distribution of soil organic carbon (SOC). Specifically, we explored the use of topographic principal components (TPCs) for characterizing topography metrics and stepwise principal component regression (SPCR) to develop topography-based soil erosion and SOC models at site and watershed scales. Performance of SPCR models was evaluated against stepwise ordinary least square regression (SOLSR) models. Results showed that SPCR models outperformed SOLSR models in predicting soil redistribution rates and SOC density at different spatial scales. Use of TPCs removes potential collinearity between individual input variables, and dimensionality reduction by principal component analysis (PCA) diminishes the risk of overfitting the prediction models. This study proposes a new approach for modeling soil redistribution across various spatial scales. For one application, access to private lands is often limited, and the need to extrapolate findings from representative study sites to larger settings that include private lands can be important.

Landscape processes are critical components of soil formation and play important roles in determining soil properties and spatial structure in landscapes. We propose a new approach using stepwise principal component regression to predict soil redistribution and soil organic carbon across various spatial scales.

Landscape topography is a critical factor affecting soil formation and plays an important role in determining soil properties on the earth surface, as it ...

Electrostatic Method to Remove Particulate Organic Matter from Soil

Estimations of soil organic carbon are dependent on soil processing methods including removal of undecomposed plant material. Inadequate separation of roots and plant material from soil can result in highly variable carbon measurements. Methods to remove the plant material are often limited to the largest, most visible plant materials. In this manuscript we describe how electrostatic attraction can be used to remove plant material from a soil sample. An electrostatically charged surface passed close to dry soil naturally attracts both undecomposed and partially decomposed plant particles, along with a small quantity of mineral and aggregated soil. The soil sample is spread in a thin layer on a flat surface or a soil sieve. A plastic or glass Petri dish is electrostatically charged by rubbing with polystyrene foam or nylon or cotton cloth. The charged dish is passed repeatedly over the soil. The dish is then brushed clean and recharged. Re-spreading the soil and repeating the procedure eventually results in a diminishing yield of particulates. The process removes about 1 to 5% of the soil sample, and about 2 to 3 times that proportion in organic carbon. Like other particulate removal methods, the endpoint is arbitrary and not all free particulates are removed. The process takes approximately 5 min and does not require a chemical process as do density flotation methods. Electrostatic attraction consistently removes material with higher than average C concentration and C:N ratio, and much of the material can be visually identified as plant or faunal material under a microscope.

Removing recently deposited and incompletely decomposed plant material from soil samples reduces the influence of temporary seasonal inputs on soil organic carbon measurements. Attraction to an electrostatically charged surface can be used to quickly remove a substantial amount of particulate organic matter.

Estimations of soil organic carbon are dependent on soil processing methods including removal of undecomposed plant material. Inadequate separation of ...