The determination of dissolved organic carbon by inductively coupled plasma atomic emission spectroscopy

Dissolved organic carbon (DOC) present in soil solutions was measured by inductively coupled plasma atomic emission spectroscopy (ICPAES) using the two C(I) lines at 197.09 nm and 247.856 nm. Carbon standards, prepared from sucrose, in the range 100 to 1000 mg L-1 produced linear coefficients of determination of r2 ≥ 0.9998 for each of the lines with calculated detection limits of 0.034 and 1.094 mg L-1 for each line, respectively. Inorganic carbon was eliminated from solution by the addition of concentrated nitric acid and sparging with high purity nitrogen for 30 min. A comparison of the DOC values for soil solutions extracted from nine soil samples by ICPAES and dichromate oxidation showed a high degree of correlation ( r2 ≥ 0.9982). Copyrigh

Aluminium reactions with polygalacturonate and related organic ligands

Aluminium (Al), in inorganic monomeric forms, has been recognised as a limiting factor for root growth in many acid soils. Plant tolerance to Al may be achieved by the detoxification (complexation) of Al by organic ligands present in the rhizosphere. The Al-complexing ability of seven organic ligands, citric, oxalic, gluconic, glucuronic, mucic, galacturonic and polygalacturonic (pectin) acids, was investigated. The proportion of organically-complexed Al was determined using colorimetric methods based on differences in reaction rate with pyrocatechol violet or aluminon. The colorimetric methods confirmed that citric acid forms a strong complex with Al at pH 4.2. In contrast, pectin and related organic ligands weakly complexed Al in acidic conditions. In an additional study, the Al-binding ability of pectin and Ca-pectate was compared at a biologically significant concentration of 32 μM Al. Only 29% of free Al remained in solution in the presence of Ca-pectate, while 54% remained when pectin was present. This suggests that Ca-pectate, rather than pectin, is responsible for binding Al in root cell walls and consequently plays an important role in Al toxicity to plants. Root growth of mungbean (Vigna radiata (L.) Wilczek) confirmed differences in the ability of citrate, oxalate and galacturonate to complex Al

Determination of dissolved organic carbon by inductively coupled plasma atomic emission spectrometry

Dissolved organic carbon (DOC) present in soil solutions was measured by inductively coupled plasma atomic emission spectrometry (ICPAES) using the two C(I) lines at 193.09 nm and 247.856 nm. Carbon standards, prepared from sucrose in the range 100 to 1,000 mg/L, produced linear coefficients of determination of r≥ 0.9998 for each of the lines with calculated detection limits of 0.034 and 1.094 mg/L for each line, respectively. Inorganic carbon was eliminated from solution by the addition of concentrated nitric acid and sparging with high purity nitrogen for 30 min. A comparison of the DOC values for soil solutions extracted from nine soil samples by ICPAES and dichromate oxidation showed a high degree of correlation (r≥ 0.9982)

Sterile solution culture techniques for aluminum toxicity studies involving organic acids

Microbial degradation of low molecular weight organic acids can be a serious source of error in solution culture experiments concerned with the protection of plant roots by these compounds against aluminum (Al) toxicity. Under normal glasshouse conditions, the problem was not solved by sterilisation of the various components of the solution culture system and surface sterilisation of the soybean and mungbean seeds. Of four water soluble antibiotics tested, streptomycin, rifampicin, and trimethoprim were phytotoxic at concentrations ≥ 50 mg/L; cefotaxime, while not phytotoxic up to 150 mg/L, gave poor control of microbial growth in 2-day root elongation tests with mungbean. However, addition of 30 mg/L cefotaxime plus 20 mg/L trimethoprim at planting and a further 30 mg/L cefotaxime after one day was effective in controlling microbial numbers and preventing significant loss of added citrate to the solutions. At these concentrations the antibiotics were non-phytotoxic and appeared not to cause any complexation of A1. Use of the method showed that citrate, L-malate, and oxalate were highly effective detoxifiers of A1 in solution

Chromatographic techniques for the separation of Al and associated organic ligands present in soil solution

Organic acids including humic, fulvic, aliphatic and aromatic acids comprise part of the dissolved organic carbon (DOC) present in soil solution. They act as ligands for trace metals and are effective detoxifiers of monomeric aluminium (Al). Solid phase extraction (SPE) techniques permit fractionation of the DOC into organic classes but yield no information on the pre-existing Al/organic acid complexes. Aliphatic and aromatic acids may be separated and determined by High Performance Liquid Chromatography (HPLC); however, the conditions used dissociate the organic acid Al complexes. Humic and fulvic acids are of a variable and ill-defined nature and only limited information exists regarding their binding of Al. This paper reports on fractionation studies of soil solutions, using both SPE and molecular weight cut-off filters, to characterise the DOC components and on the subsequent development of a size exclusion chromatography (SEC) system for the separation of organically complexed Al into different species using a low ionic strength mobile phase at pH 4.2. Model complexes of Al and Cu citrate were used to evaluate chromatographic performance of a Fractogel TSK HW-40(S) column (1×30 cm). For soil solution samples, the column eluate, after passing through a UV detector, was directly coupled to an Inductively Coupled Plasma Atomic Emission Spectrometer (ICPAES) for on-line multi-element detection to characterise DOC and trace metal distribution. Fractionation studies revealed that polysaccharides constituted the major proportion of the DOC which passed the 10000 dalton molecular weight cut-off filter. Analysis of soil solutions from an organically amended soil by the SEC-ICPAES system showed that Al, Fe and Mn eluted as multiple peaks prior to the bed volume, indicating their presence as complexes with organic ligands

Characterisation of fulvic and humic acids from leaves of Eucalyptus camaldulensis and from decomposed hay

Soluble soil organic components including fulvic acid (FA) and humic acid (HA) have the ability to complex cations, such as plant toxic monomeric aluminium (Al). We describe the chemistry of FA and HA extracted from two sources before their use in solution culture experiments aimed at determining their ability to ameliorate Al toxicity. Aqueous extracts containing FA and HA were obtained from aerobically incubated leaves of Eucalyptus camaldulensis (Eucalyptus) and decomposed grass and lucerne hay (Compost). The FA and HA were separated and concentrated by precipitation and ion adsorption using XAD-7 resin, purified and dried. Selected elemental properties, size exclusion chromatograms and solid state 13C-NMR spectra obtained for the FA and HA from both sources showed distinct structural differences. The FA obtained from the extensively decomposed Compost consisted of simpler and smaller components. The younger FA and HA obtained from the freshly prepared extract of Eucalyptus were very similar in their chemical attributes

Developing, validating and applying near infrared (NIR) spectroscopic methods for the nutrient compositional analysis of sugar mill byproducts

THE IMPLEMENTATION OF the Reef Protection Act 2009 has seen the Australian sugar industry adopt measurement driven systems for nutrient application. Recent attention on the application of sugar mill by-products to the cane field has encouraged the development of rapid and cost-effective methods for the determination of nutrient composition of mill mud and mill ash products. Near infrared (NIR) spectroscopic methods for these analyses surpass several facets of traditional wet chemistry methods, dramatically reducing costs, required expertise and chemical exposure, while increasing throughput and access to data. Further, this technology can be applied in various modes including laboratory, at-line and on-line installations, allowing measurements to be taken at different sampling points. Application of NIR methods for the nutrient analysis of mill byproducts has been previously conducted on a small scale, but this paper presents an extended investigation including data covering multiple milling regions across several crushing seasons. Mill mud samples were obtained from four mills over the 2009-12 crushing seasons. Each sample was analysed using traditional wet chemistry methods for the nutrient elements carbon, nitrogen, phosphorus, potassium, calcium, magnesium, and sulphur, and scanned by an NIR instrument. Partial least squares (PLS) regression models were used to build calibrations for each constituent, targeting a combination of high R2 values and low standard errors of calibration and validation. These calibrations were subsequently validated with data collected on a millbased NIR system in the 2012 crushing season. This work has demonstrated the success of NIR technology for the use of rapid, cost effective nutrient analysis in the milling environment.</p

ZHAW StudiPortal

Die Zürcher Hochschule für Angewandte Wissenschaften (ZHAW) ist eine Mehrsparten-Fachhochschule im Kanton Zürich mit rund 11'000 Studierenden. Der bevorstehende Relaunch des ZHAW Intranets war die Motivation, die Bedürfnisse der Studierenden an ein künftiges Intranet zu erheben. Zum Kennenlernen der Domäne wurde eine Konkurrenzanalyse unter Schweizer Fachhochschulen und Universitäten gemacht sowie Best Practice-Beispiele evaluiert. Zudem wurden zwei Experteninterviews mit Verantwortlichen von Studierendenportalen anderer Fachhochschulen durchgeführt. Ergänzend wurde das ZHAW Intranet sowie die Zielgruppe der Studierenden an der ZHAW genauer analysiert. Die neue Plattform sollte mit den Methoden des User Centered Designs zusammen mit Studierenden entwickelt und getestet werden. Für dieses Vorgehen wurde das 5S-Modell von J.J. Garrett (2011) gewählt. Die Bedürfnisse der Studierenden wurden mittels Interviews und einer Online-Umfrage erhoben und daraus wurden Personas erstellt. Auch die Anforderungen der Studiengangsekretariate wurden in mehreren Workshops erhoben. Die Auswertungen all dieser Erhebungen ergaben eine Vielzahl von unterschiedlichen Plattformen und Tools, in welchen sich die Studierenden nur schwer zurechtfinden. Ihr primärer Wunsch an ein neues Intranet ist daher eine zentrale Plattform, auf welcher sie alle Informationen finden und Zugriff auf alle wichtigen Tools haben. Anhand dieser Ergebnisse wurde gemeinsam mit der Auftraggeberin der Scope für den zweiten Projektteil definiert: das iterative Erstellen eines Prototyps für ein künftiges Studierendenportal. In einem Cardsorting-Workshop mit Studierenden wurde zunächst die Informationsarchitektur für das neue Portal erarbeitet. Der Prototyp des ZHAW StudiPortals wurde in mehreren Iterationen zusammen mit den Studierenden entwickelt und getestet. Die anfänglich zwei Varianten von Papierprototypen wurden zu einem Wireframe-Prototyp konsolidiert und im Usability-Labor der ZHAW getestet. Anhand der Ergebnisse wurde der Prototyp verfeinert und mit Marktbesuchern am Toni Märt in einem Usability-Walkthrough getestet. Daraus entstand der finale Prototyp des ZHAW StudiPortals. Das grosse Interesse an diesem Projekt und die rege Beteiligung an der Online-Umfrage zeigen, dass die aktuelle Situation für die Studierenden sehr unbefriedigend ist und dass sie gerne mithelfen, eine bessere Lösung zu gestalten. Das überwiegend positive Feedback zum Prototyp des ZHAW StudiPortals lassen darauf schliessen, dass dieses Vorgehen der richtige Weg ist, um den Bedürfnissen der Studierenden gerecht zu werden