Iodine geodynamics and plant availability

Iodine is an essential micronutrient for human health. However, approximately 1.9 billion people worldwide are at risk of developing an iodine deficiency disorder. The uptake of iodine by crops and subsequent consumption can be a vital component of dietary intake: further understanding of soil and crop iodine dynamics will determine the sustainability of iodine phytofortification. The aim of this thesis was to improve the understanding of soil-plant-iodine dynamics by measuring in-situ soil solution-solid phase interactions and identifying specific plant-iodine mechanisms to better inform iodine phytofortification strategies. Experiments were designed to demonstrate that microdialysis is a suitable means for extracting iodine from soil solution. By using microdialysis it was possible to observe iodine interactions in soils at significantly improved temporal resolution. Online liquid chromatography was coupled with ICP-QQQ-MS to analyse the speciation and molecular weight distribution of iodine in soil solution. Greater instantaneous adsorption rates of iodate (129IO3–) compared to iodide (129I–) were observed in soil with the complete reduction of iodate occurring within 5 hours. Soluble organically bound iodine was identified with a low molecular weight (<5 kDa), with a slower time-dependent formation of larger iodinated compounds (12-18 kDa). Modelling with simultaneous ordinary differential equations revealed that iodine present in soil solution, not instantaneously adsorbed, had an average half-life of <2 hours. Spinach was used to assess iodine uptake, storage and translocation mechanisms. The results confirmed that roots can reduce iodate to iodide in solution. Within root solutions, iodine was present as organically bound iodine or iodide with significantly greater concentrations in the apoplast compared to the symplast, indicating that whilst active pathways exist, passive uptake is the primary absorption mechanism. Iodine applied directly to leaves was successfully adsorbed and stored, however, translocation was severely limited. As such, foliar application is unlikely to significantly increase the iodine content, via phloem translocation, of fruits, grains or tubers. Soil-to-crop transfers are significantly limited by the short window of opportunity in which roots can absorb iodine from soil solution prior to it becoming unavailable. The findings in this thesis contribute to a better understanding of the soil-plant-iodine dynamics and therefore, efficacy of phytofortification strategies

Resolving the unresolved: online microdialysis coupled to ICPQQQ for the simultaneous sampling and analysis of dissolved elements in soil solution

Assessing rapid chemical-elemental reactions in soils is significantly inhibited by the spatial and temporal resolution of current sampling techniques [RhizonTM samplers, diffusive gradients in thin films (DGTs)]1 . Soil chemistry is typically investigated over hours-days-weeks and with poor sampling density; the vast majority of reactions occur within seconds-minutes. Microdialysis (MD) is a new technique in the field of soil science that uses small probes to sample compounds dissolved in soil solution, with minimal disturbance to the external environment2 . Initially developed for use in neuroscience, MD has the potential for translation to environmental geochemistry to define soil chemical/physical parameters, and better inform predictive models for soil-to-plant transfer of potentially harmful elements (PHEs) or essential nutrients. One considerable experimental challenge for MD is balancing the target analyte recovery efficiency with the sample volume required for the analytical chemistry technique, which can significantly affect how often elemental speciation changes and soil fixation events can be measured3 . To overcome this challenge, we have begun development of a novel integrated online MD sampling and analysis technique, through direct coupling of MD probes with triple quadrupole inductively coupled plasma mass spectrometry (ICP-QQQ) using a microflow total consumption nebulizer with no additional modifications. This poster will present the initial setup, optimisation and application of the technique to the sampling and analysis of multiple elements in soil solution, alongside future perspectives on how information gained from this promising technique can contribute to the management of global societal and agricultural issues (e.g. nutrient supply to staple crops, contaminated land remediation)

Nonlinear Optical and Two-Photon Absorption Properties of Octupolar Tris(bipyridyl)metal Complexes

The linear (absorption and emission) and nonlinear optical (NLO) properties of a series of D3 [(Fe(II), Ru(II), Ni(II), Cu(II), Zn(II)] octupolar metal complexes featuring the 4,4'-bis[(dibutylamino)styryl]-2,2'- bipyridine ligand are reported. Zinc(II)

Geochemistry and health data to inform public health outcomes in western Kenya

Environmental geochemistry data can reveal spatial differences in dietary intake with implications for health status. For example, soil and subsequently crop chemistry data is influenced by changes in soil type, pH, geology and geographical features (amongst other factors). Specific soil and food composition data can support estimates of dietary mineral supplies (Watts et al. 2019, 2021a). However, additional metrics can supplement the understanding of links between geochemistry and health in Western Kenya. Here we present a summary of data from a survey of soil and crops, but will focus in particular on the private drinking water and urines as an estimate of nutritional status or exposure to potentially harmful elements collected across 20 Counties in Western Kenya. We discuss the potential for interpreting health metrics, including: food dietary estimates, drinking water and biomonitoring data (urine – Watts et al. 2020; 2021b). Comparisons between these metrics will be discussed, along with the limitations in interpreting these data. These datasets were presented to stakeholders from each of the 20 Counties in June 2022 to provide feedback on data outcomes and to co-design the data delivery to assist in dissemination. Stakeholders included the leaders of agriculture and public health offices in each County government office and from academia. This second point of discussion will raise the importance of information flow back and the challenges in doing so e.g. mis-/over-interpretation of data, opportunities to incorporate into decision making and the stimulation of new research. In particular, the value of undertaking a multi-disciplinary research project to encourage stakeholders to plan intervention strategies with a multi-disciplinary consideration

Iodine status in western Kenya: a community-based cross-sectional survey of urinary and drinking water iodine concentrations

Spot urinary iodine concentrations (UIC) are presented for 248 individuals from western Kenya with paired drinking water collected between 2016 and 2018. The median UIC was 271 µg L−1, ranging from 9 to 3146 µg L−1, unadjusted for hydration status/dilution. From these data, 12% were potentially iodine deficient ( 300 µg L−1). The application of hydration status/urinary dilution correction methods was evaluated for UICs, using creatinine, osmolality and specific gravity. The use of specific gravity correction for spot urine samples to account for hydration status/urinary dilution presents a practical approach for studies with limited budgets, rather than relying on unadjusted UICs, 24 h sampling, use of significantly large sample size in a cross-sectional study and other reported measures to smooth out the urinary dilution effect. Urinary corrections did influence boundary assessment for deficiency–sufficiency–excess for this group of participants, ranging from 31 to 44% having excess iodine intake, albeit for a study of this size. However, comparison of the correction methods did highlight that 22% of the variation in UICs was due to urinary dilution, highlighting the need for such correction, although creatinine performed poorly, yet specific gravity as a low-cost method was comparable to osmolality corrections as the often stated ‘gold standard’ metric for urinary concentration. Paired drinking water samples contained a median iodine concentration of 3.2 µg L−1 (0.2–304.1 µg L−1). A weak correlation was observed between UIC and water-I concentrations (R = 0.11)

Hierarchies of trade in Yiwu and Dushanbe: the case of an Uzbek merchant family from Tajikistan

This article focuses on the trading trajectory of an Uzbek family of merchants from Tajikistan. This family runs businesses in both Tajikistan’s capital, Dushanbe, and China’s famous international trading city: Yiwu. The analysis is centred on the accounts placed by Tajikistan’s Uzbek merchants about their historically sustained experience, often across several generations, in trading activities. These merchants’ claims of belonging to a ‘historical’ trading community rather than being ‘newcomers’ to long-distance commerce are articulated in relation to notions of ‘hierarchies of trade’ as they evolve in a twofold relational model linking Yiwu’s Changchun neighbourhood and Dushanbe. I suggest that the forms of conviviality enacted in Yiwu’s Changchun neighbourhood need to be understood in terms of the historical, multinational and transregional contacts that have occurred within the spaces of the former Soviet Union, as well as along the China-Russia and China-Central Asian borders. Equally, the hierarchies of trade of Uzbek merchants from Tajikistan in Yiwu’s Changchun neighbourhood cut-across markers of identity that juxtapose the roles of Tajik and Uzbek communities in Tajikistan’s contemporary politics and economics

Public health assessment of Kenyan ASGM communities using multi-element biomonitoring, dietary and environmental evaluation

The Kakamega gold belt's natural geological enrichment and artisanal and small-scale gold mining (ASGM) have resulted in food and environmental pollution, human exposure, and subsequent risks to health. This study aimed to characterise exposure pathways and risks among ASGM communities. Human hair, nails, urine, water, and staple food crops were collected and analysed from 144 ASGM miners and 25 people from the ASGM associated communities. Exposure to PHEs was predominantly via drinking water from mine shafts, springs and shallow-wells (for As>Pb>Cr>Al), with up to 366 µg L−1 arsenic measured in shaft waters consumed by miners. Additional exposure was via consumption of locally grown crops (for As>Ni>Pb>Cr>Cd>Hg>Al) besides inhalation of Hg vapour and dust, and direct dermal contact with Hg. Urinary elemental concentrations for both ASGM workers and wider ASGM communities were in nearly all cases above bioequivalents and reference upper thresholds for As, Cr, Hg, Ni, Pb and Sb, with median concentrations of 12.3, 0.4, 1.6, 5.1, 0.7 and 0.15 µg L−1, respectively. Urinary As concentrations showed a strong positive correlation (0.958) with As in drinking water. This study highlighted the importance of a multidisciplinary approach in integrating environmental, dietary, and public health investigations to better characterise the hazards and risks associated with ASGM and better understand the trade-offs associated with ASGM activities relating to public health and environmental sustainability. Further research is crucial, and study results have been shared with Public Health and Environmental authorities to inform mitigation efforts

Nonlinear optical properties of meso-Tetra(fluorenyl)porphyrins peripherally functionalized with one to four ruthenium alkynyl substituents

The synthesis of a series of four porphyrin derivatives based on a meso-tetrafluorenylporphyrin core functionalized with one to four trans-chlorobis(dppe)ruthenium alkynyl units (dppe = 1,2-bis(diphenylphosphino)ethane) at the periphery, together with cyclic voltammetry (CV) and UV–Vis absorption and emission spectroscopy studies, are reported. In these multipolar assemblies, the organoruthenium endgroups are potential electron-donors and the central porphyrin core is a potential electron-acceptor. The third-order nonlinear optical (NLO) responses have been assessed by Z-scan, revealing that these extended π-networks incorporating polarizable organometallic units behave as nonlinear absorbers in the near-IR range. The role of the peripheral transition metal centers on the third-order NLO properties is discussed

X-ray Variability and Hardness of ESO 243-49 HLX-1: Clear Evidence for Spectral State Transitions

The ultra-luminous X-ray (ULX) source ESO 243-49 HLX-1 currently provides the strongest evidence for the existence of intermediate mass black holes. We conduct an ongoing monitoring campaign with the Swift X-ray Telescope and found that HLX-1 showed two fast rise and exponential decay with increases in the count rate of a factor ~40 separated by 375+/-13 days. We obtained new XMM-Newton and Chandra dedicated pointings that were triggered at the lowest and highest luminosities, respectively. The unabsorbed luminosities ranged from 1.9x10^40 to 1.25x10^42 erg/s. We confirm here the detection of spectral state transitions from HLX-1 reminiscent of Galactic black hole binaries: at high luminosities, the X-ray spectrum showed a thermal state dominated by a disk component with temperatures of 0.26 keV at most, and at low luminosities the spectrum is dominated by a hard power law with a photon index in the range 1.4-2.1, consistent with a hard state. The source was also observed in a steep power law state. In the thermal state, the luminosity of the disk component appears to scale with the fourth power of the inner disk temperature which supports the presence of an optically thick, geometrically thin accretion disk. The low fractional variability (rms of 9+/-9%) in this state also suggests the presence of a dominant disk. The spectral changes and long-term variability of the source cannot be explained by variations of the beaming angle and are not consistent with the source being in a super-Eddington accretion state. HLX-1 is thus an unusual ULX as it is similar to Galactic black hole binaries, which have non-beamed and sub-Eddington emission, but with luminosities 3 orders of magnitude higher. In this picture, a lower limit on the mass of the black hole of >9000 M_sun can be derived, and the disk temperature in the thermal state also suggests the presence of a black hole of a few 10^3 M_sun.Comment: accepted for publication in ApJ (October 10, 2011, v740-1); 11 figures, 13 pages with emulateapj styl

Spatial distribution and loss of micronutrients in soils from two different land use management

Land use – land cover changes affect the ecosystems' status and integrity to support and supply the services. Agricultural activities and attendant soil erosion, leaching or depletion of nutrients may result in increased soil degradation. The study investigated micronutrient spatial distribution and concentration in soils within two different agricultural land use management. The study employed RUSLE equations to determine the erosion rate within the selected plots. Topsoils (5-10cm) from different points within the plots were collected and analyzed for micronutrients using ICPMS(QQQ). The plots are located in high potential soil erosion places with soil erodibility (K) factor OF 0.031-ton ha-1MJ-1mm-1 within the Ombeyi river catchment. The soil erosion was estimated to be > 50t ha-1 year-1 , implying the high loss of nutrients; hence, over 52 elements were analyzed. The two plots compared micronutrients iodine (I), calcium (Ca), copper (Cu), iron (Fe), magnesium (Mg), selenium (Se), zinc (Zn), and molybdenum (Mo). In Plot 1(no terraces), micronutrients were concentrated at the base of the plot, while in plot 2 ( terraces), some elements were evenly distributed. There is a significant difference in the concentration of elements between the plots; I, Se, Cu, Ca and Mg, depicting a p-Value of 0.05. Elements in plot one were mapped with high concentration at the lower part of the plot as related to plot two which most of the elements were evenly distributed hence reduced micronutrients in plot 2. This encourages educating farmers on the importance of good terrain soil management