Recommendations for isolation of humin fraction from soil material

<p>Methods of isolation of the humin fraction can be divided into two main groups: (1) extraction of humic (HA) and fulvic (FA) acids followed by extraction of humin with different organic solvents, and (2) extraction of HA and FA followed by removal of soil mineral fraction. To isolate the large amounts of humin necessary to study the interactions of this fraction with pesticides, we examined some modifications of the latter method.</p><p>The first step was to separate HA and FA according to a modified IHSS method (Swift 1996). HA and FA were extracted with 0.1 M NaOH with a 5:1 ratio of extractant to soil. 20 hours shaking was found to be more effective, but 4 hours shaking provided the advantage of being able to extract twice a day,  which ultimately shortened the procedure time.</p><p>The HA and FA free residue was then digested to remove mineral components. We used several (up to 8 weeks) digestions with 10% HF/HCl as higher concentrations of HF can result in structural alteration of the organic compounds (Hayes et al. 2017). While HF/HCl treatment can lead to hydrolysis and loss of polysaccharide and protein materials (Stevenson 1994), the advantage of using HF is the removal of paramagnetic compounds (such as Fe), which facilitates the use of spectroscopic techniques to characterize humin. In contrast to the procedures for only increasing the concentration of organic matter (Schmidt et al. 1997), the sample was digested until the mineral fraction not complexed with humin was completely digested. We tested different modes of mineral fraction digestion in 10% HF/HCl using polyethylene centrifuge bottles. Occasional shaking once a day had the same effect as continuous shaking. It takes 6 weeks to digest 200 g of pure sand in a 1000 cm<sup>3</sup> bottle, when the HF/HCL was weekly replaced. After replacing HF/HCl every 2 weeks, the digestion time of the same material increased to 8 weeks.</p><p>After treatment with HF/HCl, the residue was rinsed with 10% HCl to remove secondary minerals. The residue was washed with distilled water until the neutral pH and then dialyzed to a negative Cl<sup>−</sup> test with AgNO<sub>3</sub>. Then the humin fraction was freeze dried. </p><p> </p><p>Literature</p><p>Hayes M.H.B., Mylotte R., Swift R.S. 2017. Humin: Its Composition and Importance in Soil Organic Matter. In: Sparks D.L. (ed) Advances in Agronomy, Vol. 143, Academic Press, Burlington, 47–138.</p><p>Schmidt, M.W.I., Knicker, H., Hatcher, P.G., Kögel-Knabner, I. 1997. Improvement of 13C and 15N CPMAS NMR spectra of bulk soils, particle size fractions and organic material by treatment with 10% hydrofluoric acid. European Journal of Soil Science, 48, 319-328.</p><p>Stevenson F.J. 1994. Humus Chemistry; Genesis, Composition, Reaction. 2nd ed. John Wiley & Sons., New York.</p><p>Swift R.S. 1996. Organic matter characterization. In: Sparks, D.L., et al. (Ed.), Methods of Soil Analysis. Part 3. Chemical Methods - Soil Science Society of America, Book Series no 5,  1011-1069.</p><p> </p><p>Acknowledgements</p><p>This work was supported by the National Science Center (NCN) Poland (project No 2018/31/B/ST10/00677 “Chemical and spectroscopic properties of soil humin fraction in relation to their mutual interaction with pesticides").</p>

Selected properties of the humin fraction isolated from Chernozems and Phaeozems from various regions of Poland

<p>Humin fraction of soil organic matter is assigned to play an important role in carbon sequestration and sorption of xenobiotics. This study concerns the properties of humin (elemental composition, FTIR and SEM-EDS of humin ash) isolated from mollic horizons of eight Chernozems and Phaeozems, used as arable soils in various regions of Poland. Isolation procedure was described by Weber et al. (2021) in another abstract presented in this session. Investigated soils differed in the content of TOC, ranging from 13.3 to 41.7 g kg<sup>−1</sup>, as well as texture from loam (Magnice, Pyrzyce) through silt loam (Trzebnik, Ciepłowody, Hrubieszów) and sandy clay loam (Psary) till clay (Ziemnice, Kętrzyn). They also differed in their pH values (from 5.64 to 7.71), and CEC (from 21.6 to  53.2cmol(+)kg<sup>-1</sup>). Ash content of humin varied between 22.89%  - 54.50%, which is typical for humin originated from mineral soils (Stevenson 1994). This parameter was not correlated neither with the content of <0.002 mm fraction nor TOC content. SEM-EDS analyzes revealed that ash contained mainly Mg (3 – 14 weight%), Al (4 – 22 weight %) and Ti (10 – 25 weight%), depending on the area studied. The lowest pH as well as  the highest TOC and CEC showed Trzebnik soil. Humin from this soil indicated the lowest content of carbon (30.84 %) and the highest values of H/C ratio, which point out to the higher aliphacity of their molecules (Rice and MacCarthy 1991). High O/C ratio (0.91) calculated for humin from Trzebnik is common for more oxidized carbohydrate molecules and makes them similar to fulvic acids which are polysaccharidic in nature (Tan 2014). In contrast, the lowest TOC and CEC were determined in Ciepłowody soil. Humin molecules from this soil indicated the highest carbon content (43.12 %) and the lowest H/C ratio, what reflects the highest aromacity among investigated samples. FTIR spectra confirmed results from elemental analysis and indicated that humin from Ciepłowody and Hrubieszów was the most aromatic among all analyzed soils.</p><p> </p><p>References:</p><p>Hayes M.H.B., Mylotte R., Swift R.S. 2017. Humin: Its Composition and Importance in Soil Organic Matter. In: Sparks D.L. (ed) Advances in Agronomy, Vol. 143, Academic Press, Burlington, 47–138.</p><p>Rice J.A., MacCarthy P. 1991. Statistical evaluation of the elemental composition of humic substances. Org. Geochem, 17(5), 635-648.</p><p>Stevenson FJ. 1994. Humus chemistry: Genesis, composition, and reactions. New York: John Wiley and Sons, p 512.</p><p>Swift R.S. 1996. Organic matter characterization. In: Methods of soil analysis. Part 3. Chemical methods – SSSA Book Series no.5. Soil Science Society of America and American Society of Agronomy, pp 1011-1068.</p><p>Tan HK. 2014. Humic matter in soil and the environment, 2<sup>nd</sup> edn. CRC Press, Boca Raton, p 463.</p><p>Weber J., Jamroz E., Kocowicz A., Debicka M., Ukalska-Jaruga A., Mielnik L., Bejger R., Jerzykiewicz M., Bekier J., Ćwieląg-Piasecka I. Recommendations for isolation of humin fraction from soil material. EGU21-8315</p><p> </p><p>Acknowledgements</p><p>This work was supported by the National Science Center (NCN) Poland (project No 2018/31/B/ST10/00677 “Chemical and spectroscopic properties of soil humin fraction in relation to their mutual interaction with pesticides")</p>

Empowering geoscientists to transform workplace climate through behavioral and institutional change, results from a workplace climate survey by the ADVANCEGeo Partnership

<p>The geosciences are one of the least diverse fields in the U.S., despite their societal relevance. Bias, discrimination, harassment and bullying create hostile climates that present serious hurdles to diversifying the field. These behaviors persist due to severe power imbalances, historical structures of exclusion, persistent marginalization of non-majority groups, and inadequate policies against misconduct. Here we discuss findings from a workplace climate survey of the earth and space sciences distributed via five professional associations: American Geophysical Union, Geological Society of America, Soil Science Society of America, Earth Science Women’s Network and the Association for Women Geoscientists. The survey asked about attitudes and experiences of support, inclusion, exclusion, psychological safety, incivility, and sexual harassment, as well as representation in the workplace. Quantitative results are complemented with qualitative data from the survey and focus groups. This is one of the first such community-wide surveys in the U.S. geosciences and is currently being replicated in the ecological sciences. </p><p>We present the findings of the survey in the context of other work done by the ADVANCEGeo Partnership team and provide recommendations for moving forward. Our approach is informed by critical feminist approaches that seek to disrupt unequal power dynamics in strongly hierarchical workplaces. Expanding the focus from a gender equity program emphasis on sexual harassment to hostile climates, and centering how intersectionality shapes the experiences of those disproportionately impacted by exclusionary behaviors is key for addressing persistent demographic trends in the geosciences. A feminist ethics of care approach informs ADVANCEGeo’s main organizational change intervention, which is a community-based model for bystander intervention and workplace climate education that identifies harassment, bullying and discrimination as scientific misconduct and promotes the adoption of ethical codes of conduct.</p>

Aragonite is calcite’s best friend at the seafloor

<p>Aragonite is about 50% more soluble than calcite in seawater and its pelagic production is dominated by pteropods. Moreover, it could account for a large fraction of marine CaCO<sub>3</sub> export. The <em>aragonite compensation depth</em> (ACD, the depth at which accumulation is balanced by dissolution) is generally very close to the <em>aragonite saturation depth</em>, i.e. within a few hundred metres. Conversely, the <em>calcite compensation depth</em> (CCD) can be 1-2 kilometres deeper than the <em>calcite saturation depth</em>. That aragonite disappears shallower than calcite in marine sediments is coherent with aragonite’s greater solubility, but why is the calcite <em>lysocline</em>, i.e. the distance between its compensation and saturation depths, much thicker than its aragonite equivalent?</p><p>Here, we suggest that at the seafloor, the addition of a soluble CaCO<sub>3</sub> phase (aragonite) results in the preservation of a predeposited stable CaCO<sub>3</sub> phase (calcite), and term this a negative priming action. In soil science, priming action refers to the increase in soil organic matter decomposition rate that follows the addition of fresh organic matter, supposedly resulting from a globally increased microbial activity (Bingeman et al., 1953). Using a new 3D model of CaCO<sub>3</sub> dissolution at the grain scale, we show that a conceptually similar phenomenon could occur at the seafloor, in which the dissolution of an aragonite pteropod at the sediment-water interface buffers the porewaters and causes the preservation of surrounding calcite. Since aragonite-producing organisms are particularly vulnerable to ocean acidification, we expect an increasing calcite to aragonite ratio in the CaCO<sub>3</sub> flux reaching the seafloor as we go further in the Anthropocene. This could, in turn, hinder the proposed aragonite negative priming action, and favour chemical erosion of calcite sediments.</p><p> </p><p>Reference: Bingeman, C.W., Varner, J.E., Martin, W.P., 1953. The Effect of the Addition of Organic Materials on the Decomposition of an Organic Soil. Soil Science Society of America Journal 17, 34-38.</p>

International Gender Equity in Soil Science: A Social Equity Issue

<p>Gender equity is a concern in many scientific fields, including soil science. Lower percentages of women work as soil scientists than we have in the general population; fewer opportunities to serve on committees or as invited speakers at scientific meetings; lower selection rates for scientific awards; unconscious bias; tension with work-life balance; poor funding and pay; lack of career progression and a lack of networking opportunities. Advances have been made in many countries, although major discrepancies still exist and women are overall still a minority in soil science and related fields.</p><p>A review of international gender equity issues in soil science was undertaken by requesting gender data from 70 national soil science societies around the world; forty-three societies responded. Female members ranged from 0% to 69%. Thirty-six of the 43 societies had more male than female members; the global average was 68% male and 32% female. Some societies noted that women make up a majority of the younger soil science generation or women make up a larger percentage of the younger membership than of the total membership in their society. These findings indicate there is some progress in gender equity in these countries. However, higher numbers of women do not always mean the reasons for those higher numbers are positive. For example, the Bulgarian Soil Science Society mentioned that women were a majority of their soil scientists because soil science did not pay well and men would not take such a low-paying job. Twenty percent of the national soil science societies belonging to the International Union of Soil Sciences (IUSS) have a woman as their president. However, this is lower than the average female membership (32%) in these societies. This is an indication that women are underrepresented in leadership roles.</p><p>A rethinking of gender equity is needed to create a new paradigm that allows us:</p><p>1. To create an inclusive perspective that encourages respect, collaboration and solidarity between the genders. An education based on the full understanding that “equality does not mean that women and men will become the same but that women’s and men’s rights, responsibilities and opportunities will not depend on whether they are born male or female.”</p><p>2. An education that recognizes that soil is not only a natural resource, but also provides social, economic, cultural, political and <em>patrimonial</em> good. The soil not only allows humans to live on it, it supplies food, water and a legitimate sustenance to overcome poverty and to construct an identity, cultural and economic independence.</p><p>Therefore, <em>legitimate land ownership is a key element in achieving gender equality for the construction of a just and equitable life</em>, but also the only real way <em>to end all forms of discrimination against women and girls</em>. To improve equity in the sciences, including soil science, we need to educate in a way that changes the gender stereotypes that link science to stereotypes about masculinity. <em>There is no equality without economic independence</em>, and <em>there is no economic independence without equal access to land ownership and land care</em>.</p>

The Heat Pulse Method for Soil Physical Measurements: A Bibliometric Analysis

Heat pulse method is a transient method that estimates soil thermal properties by characterizing the radial transport of short-duration line-source heat applied to soils. It has been widely used to measure a wide range of soil physical properties including soil thermal conductivity, thermal diffusivity, heat capacity, water content, ice content, bulk density, water flux and evaporation in laboratory and field environments. Previous studies generally focus on the scientific aspects of heat pulse method based on selected publications, and there is a lack of study investigating the heat pulse publication as a whole. The objective of this study was to give an overall view of the use of heat pulse method for soil physical measurements from the bibliometric perspectives. The analyses were based on the Web of Science Core Collection data between 1992 and 2019 using HistCite Pro and VOSviewer. The results showed an increasing trend in the volume of publications on this field and Dr. Robert Horton was the most productive researcher coauthoring papers on the heat pulse method. The co-authorship analysis revealed that researchers from soil science are closely collaborated, but this is not true for researchers in other fields. There is a lack of new young scientists committing to this field while the older generation of researchers are retiring. The United States Department of Agriculture Agricultural Research Servics (USDA-ARS), the China Agriculture University and the Chinese Academy of Science were the top three organizations applying the heat pulse method, while the USA, China and Canada were the top three countries. The Soil Science Society of America Journal, Water Resources Research and Agricultural and Forestry Meteorology were the most widely used journals. The con-occurrence and citation analysis could be used to map the development of the field and identify the most influential publications. The study showed that the bibliometric analysis is a useful tool to visualize research status as well as to provide the general information of novices and experts alike on the heat pulse method for soil physical measurements.

Organic Matter Preservation in Ancient Soils of Earth and Mars

The emerging field of astropedology is the study of ancient soils on Earth and other planetary bodies. Examination of the complex factors that control the preservation of organic matter and other biosignatures in ancient soils is a high priority for current and future missions to Mars. Though previously defined by biological activity, an updated definition of soil as planetary surfaces altered in place by biological, chemical or physical processes was adopted in 2017 by the Soil Science Society of America in response to mounting evidence of pedogenic-like features on Mars. Ancient (4.1–3.7 billion year old [Byr]) phyllosilicate-rich surface environments on Mars show evidence of sustained subaerial weathering of sediments with liquid water at circumneutral pH, which is a soil-forming process. The accumulation of buried, fossilized soils, or paleosols, has been widely observed on Earth, and recent investigations suggest paleosol-like features may be widespread across the surface of Mars. However, the complex array of preservation and degradation factors controlling the fate of biosignatures in paleosols remains unexplored. This paper identifies the dominant factors contributing to the preservation and degradation of organic carbon in paleosols through the geological record on Earth, and offers suggestions for prioritizing locations for in situ biosignature detection and Mars Sample Return across a diverse array of potential paleosols and paleoenvironments of early Mars. A compilation of previously published data and original research spanning a diverse suite of paleosols from the Pleistocene (1 Myr) to the Archean (3.7 Byr) show that redox state is the predominant control for the organic matter content of paleosols. Most notably, the chemically reduced surface horizons (layers) of Archean (2.3 Byr) paleosols have organic matter concentrations ranging from 0.014–0.25%. However, clay mineralogy, amorphous phase abundance, diagenetic alteration and sulfur content are all significant factors that influence the preservation of organic carbon. The surface layers of paleosols that formed under chemically reducing conditions with high amounts of iron/magnesium smectites and amorphous colloids should be considered high priority locations for biosignature investigation within subaerial paleoenvironments on Mars.

Optimizing the potential of iron oxide-based tracers

<p>So far, it does not exist a set of tracers which fulfill all the characteristics for being an ideal sediment tracer such as, environmentally friendly, inexpensive or easily analysed (Zhang et al., 2001). For this reason, and in order to address some of the unsolved issues of water erosion processes, more research enquiring into the development of these soil and sediment tracers is needed.</p><p>Iron oxide-based tracers has been already tested in several water erosion trials with satisfactory results (e.g. Guzmán et al., 2010, 2013, 2015). In 2015, three cascade plots with a different iron oxide (magnetite, hematite and goethite) each were set up in order to evaluate soil redistribution after the rainy season (Obereder et al., 2016). While these authors presented the total iron content of sediments after clorhydric acid extraction, the present study will show only the free iron content of soil and sediments using a different extraction method (CBC, citrate-bicarbonate-ditionite), as this method is more adequate in high iron content soils, as is our case.</p><p>The results depict the suitability of the CBD method extracting the three tracers with an average recovery rate of 0.7. The analysis of the iron content of soil and sediment samples indicates a relatively low movement of soil although showing significant statistical differences with background and mixture values. These results are in line with the ones detected by the magnetic susceptibility measurements. Further textural and visible spectrum analysis of the samples will allow to determine the possible selectivity factor and to discriminate qualitative and quantitatively hematite and goethite tracers, respectively.</p><p>References:</p><p>Guzmán et al. 2010. Catena, 82(2), 126-133.</p><p>Guzmán et al. 2013. Soil Science Society of America Journal, 77(2), 350-361.</p><p>Guzmán et al. 2015. Journal of hydrology, 524, 227-242.</p><p>Obereder et al. 2016. Geophysical Research Abstracts Vol. 18, EGU2016-2455-1. EGU General Assembly 2016.</p><p>Zhang et al. 2001. Soil Science Society of America Journal, 65(5), 1508-1515.</p>

Un receptor abierto comprometido con la conservación del suelo: Semblanza sobre el Dr. Mario Roberto Martínez Menez

Through this semblance, the Mexican Soil Science Society (MSSS), CA, offers a sincere post mortem tribute to Dr. Mario Roberto Martínez-Menez, one of its most distinguished members. Dr. Martínez-Menez was born on July 22, 1945 in Teloloapan, Guerrero, Mexico, and died on May 31, 2019 in Mexico City. Their scientific contributions are circumscribed basically within three Soil Science areas: Soil Conservation, Erosion Dynamics and Watershed Management. Besides being an excellent soil scientist, he was an outstanding football player. Dr. Martínez-Menez was one of the best open receivers of the Toros Salvajes de Chapingo team, who in 2017 entered the National Football Hall of Fame. As a testimony, his scientific legacy has been recorded in the annals of the MSSS, C.A.