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College of Science and Engineering CSE publications Recent publications in Physical Sciences

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Recent publications in Physical Sciences

Winter, Sara, Gordon, Susan, Brice, Sara, Lindsay, Daniel, and Barrs, Sue (2021) Overuse injuries in runners of different abilities — a one-year prospective study. Research in Sports Medicine. (In Press)
The aim of this prospective study was to investigate differences in participant characteristics, previous injury, running dynamics during a long-distance run, and training between injured and uninjured runners in runners of different abilities. Center-of-mass acceleration data were collected during a long-distance overground run. Runners were then divided into four groups (elite, advanced, intermediate and slow) based on their finishing time. Participants completed training diaries and were monitored for 1 year. Seventy-six runners completed the prospective study with 39 (51.3%) sustaining a running injury (44% elite, 42% advanced, 54% intermediate, 59% slow). Differences between injured and uninjured runners within each group related to injury included: (1) elite injured runners ran with longer contact times and (2) more slow injured runners reported an injury in previous year, were heavier, had higher body mass and body mass index, ran with lower step frequencies, and ran a greater weekly distance. Advanced injured runners exhibited fatigue changes in step regularity and peak braking during the run that may be related to injury. These findings suggest that runners of different abilities may have different factors related to injury however due to the small sample sizes in the groups this needs to be explored further.

Zhou, Ming, Li, Tianling, Zu, Meng, Zhang, Shanqing, Liu, Yang, and Zhao, Huijun (2021) Membrane-based colorimetric flow-injection system for online free chlorine monitoring in drinking water. Sensors and Actuators B: Chemical, 327. 128905.
The majority of water utilities currently employ the in-lab tests of the grabbed samples to determine the free chlorine (FC) residual levels. Under certain circumstances, such approaches are inadequate to timely and accurately reflect the dynamically changed FC residual levels, leading to inappropriate dosages. This work reports a uniquely configured membrane-based colorimetric flow-injection system (MCFIS) capable of accurately and reliably online monitoring drinking water FC residual levels in a rapid (1−5 min per measurement) fashion. The embedded gas-permeable membrane makes MCFIS an interference-free FC monitoring system. The developed pre-calibration strategy avoids the need for on-going calibration. The accuracy of the conventional analytical principles is almost exclusively determined by the absolute analytical signal value of one measurement data point, and any errors from such a single-data point measurement will be directly transferred to the result, which induces uncertainties, hence, poor accuracy and reliability. Differing distinctively from such conventional analytical principles, MCFIS quantifies chlorine concentration based on N, N-diethyl-p-phenylenediamine – Cl2 colorimetric reaction-controlled membrane transport process that enables the determination of gaseous chlorine concentration according to multiple measurement data points to greatly enhance the accuracy and reliability. The inherent analytical features of this slope-based signal quantification principle, interference-free and on-going calibration-free empower MCFIS with an enormous superiority over other systems for online FC monitoring applications.

Zhu, Lingling, Bloomfield, Keith J., Asao, Shinichi, Tjoelker, Mark G., Egerton, John J. G., Hayes, Lucy, Weerasinghe, Lasantha K., Creek, Danielle, Griffin, Kevin L., Hurry, Vaughan, Liddell, Michael, Meir, Patrick, Turnbull, Matthew H., and Atkin, Owen K. (2021) Acclimation of leaf respiration temperature responses across thermally contrasting biomes. New Phytologist, 229 (3). pp. 1312-1325.
Short-term temperature response curves of leaf dark respiration (R–T) provide insights into a critical process that influences plant net carbon exchange. This includes how respiratory traits acclimate to sustained changes in the environment. Our study analysed 860 high-resolution R–T (10–70°C range) curves for: (a) 62 evergreen species measured in two contrasting seasons across several field sites/biomes; and (b) 21species (subset of those sampled in the field) grown in glasshouses at 20°C:15°C, 25°C:20°C and 30°C:25°C, day : night. In the field, across all sites/seasons, variations in R25(measured at 25°C) and the leaf T where R reached its maximum (Tmax) were explained by growth T (mean air-T of 30-d before measurement), solar irradiance and vapour pressure deficit, with growth T having the strongest influence. R25decreased and Tmax increased with rising growth T across all sites and seasons with the single exception of winter at the cool-temperate rainforest site where irradiance was low. The glasshouse study confirmed that R25and Tmax thermally acclimated. Collectively, the results suggest: (1) thermal acclimation of leaf R is common in most biomes; and (2) the high T threshold of respiration dynamically adjusts upward when plants are challenged with warmer and hotter climates.

Li, Yuye, Liu, Dong, Zhu, Chengxi, Wang, Meng, Liu, Yang, and You, Tianyan (2021) A ratiometry-induced successive reusable electrochemical aptasensing platform: efficient monitoring of aflatoxin B1 in peanut. Sensors and Actuators B: Chemical. 129021. (In Press)
Currently, most reusable aptasensors rely on the reassembly of aptamers to regenerate the sensing interface. However, it remains challenging to achieve successive aptasensor reusability. Herein, for the first time, we demonstrate that a ratiometric strategy endows the electrochemical aptasensor high reusability to realize the successive detection of aflatoxin B1 (AFB1). The model sensing interface used thionine (THI)-graphene nanocomposite and ferrocene (Fc)-labeled aptamer to output current signals (ITHI and IFc). For analysis, the specific recognition of AFB1 by aptamers caused it to strip from the electrode, and the value of ITHI/IFc varied linearly with AFB1 concentration over the 0.01-100 ng mL-1 range. This relationship also worked when using a single sensor for multiple successive testing but completely failed with ITHI or IFc alone. This unique successive reusability was ascribed to the ratiometric strategy capable of eliminating the environmental influence on both signals. The feasibility of the proposed aptasensor was validated by applying it to the successive detection of AFB1, which showed excellent accuracy and reliability compared with the official method, i.e., standard high-performance liquid chromatography-fluorescence (HPLC-FL). This successive reusable electrochemical aptasensing platform can be universal for advanced analysis, and it promotes the practical applications of aptasensors particularly in the field of rapid assays.

Zhou, Ming, Li, Tianling, Xing, Chao, Liu, Yang, and Zhao, Huijun (2021) Membrane-based portable colorimetric gaseous chlorine sensing probe. Analytical Chemistry, 93 (2). pp. 769-776.
Highly toxic chlorine gas imposes serious health risks in the workplace. The ability to on-site, real-time monitoring of instantaneous and time-weighted average (TWA) chlorine gas concentrations in a simple, sensitive, accurate, and reliable manner would be highly beneficial to improve workplace health and safety. Here, we propose and experimentally validate a gaseous chlorine detection principle based on a N,N-diethyl-p-phenylenediamine sulfate salt/Cl2 colorimetric reaction-controlled membrane process to regulate the gaseous chlorine transport across a gas-permeable membrane that enables the establishment of a time-resolved analytical relationship to quantify chlorine concentration by multidata points with dramatically enhanced accuracy and reliability. A gas-permeable membrane-based portable colorimetric gaseous chlorine sensing probe (MCSP) was designed and fabricated. The MCSP embedded the proposed analytical principle that is capable of real-time continuous monitoring of the instantaneous and TWA chlorine gas concentrations within an analytical range of 0.009–2.058 mg L–1 without the need for on-going calibration, which could be a useful analytical tool for managing the toxic chlorine gas-imposed health risks in workplaces.

Gelin, Maxim F., and Kosov, Daniel S. (2021) A model for dynamical solvent control of molecular junction electronic properties. Journal of Chemical Physics, 154 (4). 044107.
Experimental measurements of electron transport properties of molecular junctions are often performed in solvents. Solvent–molecule coupling and physical properties of the solvent can be used as the external stimulus to control the electric current through a molecule. In this paper, we propose a model that includes dynamical effects of solvent–molecule interaction in non-equilibrium Green’s function calculations of the electric current. The solvent is considered as a macroscopic dipole moment that reorients stochastically and interacts with the electrons tunneling through the molecular junction. The Keldysh–Kadanoff–Baym equations for electronic Green’s functions are solved in the time domain with subsequent averaging over random realizations of rotational variables using the Furutsu–Novikov method for the exact closure of infinite hierarchy of stochastic correlation functions. The developed theory requires the use of wideband approximation as well as classical treatment of solvent degrees of freedom. The theory is applied to a model molecular junction. It is demonstrated that not only electrostatic interaction between molecular junction and solvent but also solvent viscosity can be used to control electrical properties of the junction. Alignment of the rotating dipole moment breaks the particle–hole symmetry of the transmission favoring either hole or electron transport channels depending upon the aligning potential.

Hu, Mao-Lin, Joharian, Monika, Razavi, Sayed Ali Akbar, Morsali, Ali, Wu, Deng Ze, Azhdari Tehrani, Alireza, Wang, Jun, Junk, Peter C., and Guo, Zhi-Fang (2021) Phenolic nitroaromatics detection by fluorinated metal-organic frameworks: barrier elimination for selective sensing of specific group of nitroaromatics. Journal of Hazardous Materials, 406. 124501.
Many pieces of research have been performed to detect nitroaromatic-compounds (NACs) by metal-organic frameworks (MOFs). Despite extensive studies, there are still significant challenges like selective detection of specific NAC group in presence of other NACs. Here, we have integrated two functionalization strategies through decoration of pore-walls of the MOFs with trifluoromethyl groups and extension in π-conjugated system. Based on this idea, trifluoromethyl TMU-44 (with the formula [Zn2(hfipbb)2(L1)]n.DMF, H2hfipbb = 4,4′-(hexafluoroisopropylidene) bis(benzoic acid), L1 = N,N′-bis-pyridin-4-ylmethylene-benzene-1,4-diamine) and TMU-45 (with formula [Zn2(hfipbb)2(L2)]n.DMF, L2 = N,N′-bis-pyridin-4-ylmethylene-naphthalene-1,5-diamine) frameworks have been synthesized. The aromatic skeleton of TMU-44 is based on phenyl rings while TMU-45 aromatic skeleton is extended by replacement of phenyl with naphthyl core. Measurements reveal that these MOFs are highly sensitive to phenolic NACs especially 2,4,6-trinitrophenol (TNP) with high quenching efficiency of 90% for TMU-44 (KSV = 10,652 M−1, LOD = 6.9 ppm) and 99% for TMU-45 (KSV = 34,741 M−1, LOD = 2.07 ppm). The proposed detection mechanism can be associated with hydrogen bonding between OH group of phenolic NACs and trifluoromethyl groups of TMU-MOFs as well as π(rich)∙∙∙π(deficient) interaction between π-conjugated backbone of TMU-frameworks and π-deficient ring of NACs.

Preston, Riley J., Gelin, Maxim F., and Kosov, Daniel S. (2021) First-passage time theory of activated rate chemical processes in electronic molecular junctions. Journal of Chemical Physics, 154. 114108.
Confined nanoscale spaces, electric fields, and tunneling currents make the molecular electronic junction an experimental device for the discovery of new out-of-equilibrium chemical reactions. Reaction-rate theory for current-activated chemical reactions is developed by combining the Keldysh nonequilibrium Green’s function treatment of electrons, Fokker–Planck description of the reaction coordinate, and Kramers first-passage time calculations. The nonequilibrium Green’s functions (NEGF) provide an adiabatic potential as well as a diffusion coefficient and temperature with local dependence on the reaction coordinate. Van Kampen’s Fokker–Planck equation, which describes a Brownian particle moving in an external potential in an inhomogeneous medium with a position-dependent friction and diffusion coefficient, is used to obtain an analytic expression for the first-passage time. The theory is applied to several transport scenarios: a molecular junction with a single reaction coordinate dependent molecular orbital and a model diatomic molecular junction. We demonstrate the natural emergence of Landauer’s blowtorch effect as a result of the interplay between the configuration dependent viscosity and diffusion coefficients. The resultant localized heating in conjunction with the bond-deformation due to current-induced forces is shown to be the determining factors when considering chemical reaction rates, each of which results from highly tunable parameters within the system.

Wau, Jayson S., Robertson, Mark J., and Oelgemöller, Michael (2021) Solar photooxygenations for the manufacturing of fine chemicals—technologies and applications. Molecules, 26. 1685.
Photooxygenation reactions involving singlet oxygen (1O2) are utilized industrially as a mild and sustainable access to oxygenated products. Due to the usage of organic dyes as photosensitizers, these transformations can be successfully conducted using natural sunlight. Modern solar chemical reactors enable outdoor operations on the demonstration (multigram) to technical (multikilogram) scales and have subsequently been employed for the manufacturing of fine chemicals such as fragrances or biologically active compounds. This review will highlight examples of solar photooxygenations for the manufacturing of industrially relevant target compounds and will discuss current challenges and opportunities of this sustainable methodology.

Wibawa, Pierre, Matta, Gabriel, Das, Sourav, Eratne, Dhamidu, Farrand, Sarah, Desmond, Patricia, Velakoulis, Dennis, and Gaillard, Frank (2021) Bringing psychiatrists into the picture: automated measurement of regional MRI brain volume in patients with suspected dementia. Australian and New Zealand Journal of Psychiatry. (In Press)
Objective: The volumes of various brain regions can be rapidly quantified using automated magnetic resonance imaging tools. While these appear to be useful at face value, their formal clinical utility is not yet understood, particularly for non-neuroradiologists and in patients presenting with suspected dementia. This study investigated the utility of an automated normative morphometry tool on determinations of brain atrophy by psychiatrists and radiologists in a tertiary hospital. Methods: Consecutive magnetic resonance scans (n = 110) of patients referred with suspected neurodegenerative disorders were obtained retrospectively and rated by two neuroradiologists, two general radiologists and four psychiatrists over two sessions. First, conventional magnetic resonance sequences were shown. Then, morphometry colour-coded maps, which segmented T1-weighted magnetisation prepared rapid gradient echo images into brain regions and visualised these regions in colour according to their volumetric standard deviation from a normative population, were added to the second reading which occurred ⩾6 weeks later. Presence and laterality of atrophy in frontal, parietal and temporal lobes and hippocampal regions were measured using a digital checklist. The primary outcome of inter-rater agreement on atrophy was measured with Fleiss’ Kappa (κ). We also evaluated the accuracy of the atrophy ratings for differentiating post hoc diagnosis of subjective cognitive impairment, mild cognitive impairment and dementia. Results: Agreement among all raters was fair in frontal lobe and moderate in other regions with conventional method (κ = 0.362–0.555). With morphometry, higher agreement was seen in all regions (κ = 0.551–0.654), reaching significant improvement in the frontal and temporal lobes. No significant improvement was seen within the various disciplines, except in frontal lobes rated by psychiatrists. Accuracy of atrophy ratings on determining post hoc diagnosis was significantly improved for distinguishing subjective cognitive impairment versus dementia. Conclusion: In routine clinical assessment, automated normative morphometry complements the determination of regional atrophy and improves inter-rater agreement regardless of neuroradiology experience.

Das, Sourav, Subba Rao, Suhasini, and Yang, Junho (2021) Spectral methods for small sample time series: a complete periodogram approach. Journal of Time Series Analysis. (In Press)
The periodogram is a widely used tool to analyze second order stationary time series. An attractive feature of the periodogram is that the expectation of the periodogram is approximately equal to the underlying spectral density of the time series. However, this is only an approximation, and it is well known that the periodogram has a finite sample bias, which can be severe in small samples. In this article, we show that the bias arises because of the finite boundary of observation in one of the discrete Fourier transforms which is used in the construction of the periodogram. Moreover, we show that by using the best linear predictors of the time series over the boundary of observation we can obtain a ‘complete periodogram’ that is an unbiased estimator of the spectral density. In practice, the ‘complete periodogram’ cannot be evaluated as the best linear predictors are unknown. We propose a method for estimating the best linear predictors and prove that the resulting ‘estimated complete periodogram’ has a smaller bias than the regular periodogram. The estimated complete periodogram and a tapered version of it are used to estimate parameters, which can be represented in terms of the integrated spectral density. We prove that the resulting estimators have a smaller bias than their regular periodogram counterparts. The proposed method is illustrated with simulations and real data.

Sanderson, Stephen, Vamvounis, George, Mark, Alan E., Burn, Paul L., White, Ronald D., and Philippa, Bronson W. (2021) Unraveling exciton processes in Ir(ppy)3:CBP OLED films upon photoexcitation. Journal of Chemical Physics, 154. 164101.
Emissive layers in phosphorescent organic light-emitting diodes commonly make use of guest–host blends such as Ir(ppy)3:CBP to achieve high external quantum efficiencies. However, while the Ir(ppy)3:CBP blend has been studied experimentally, crucial questions remain regarding how exciton diffusion is dependent on the distribution of the guest in the host, which can currently only be addressed at the atomic level via computational modeling. In this work, kinetic Monte Carlo simulations are utilized to gain insight into exciton diffusion in Ir(ppy)3:CBP blend films. The effects of both guest concentration and exciton density on various system properties are analyzed, including the probability of singlet excitons being converted to triplets, and the probability of those triplets decaying radiatively. Significantly, these simulations suggest that triplet diffusion occurs almost exclusively via guest–guest Dexter transfer and that concentration quenching of triplets induced by guest–guest intermolecular dipole-dipole interactions has a negligible effect at high exciton densities due to the prevalence of triplet–triplet annihilation. Furthermore, results for vacuum deposited morphologies derived from molecular dynamics simulations are compared to the results obtained using a simple cubic lattice approximation with randomly distributed guest molecules. We show that while differences in host-based processes such as singlet diffusion are observed, overall, the results on the fate of the excitons are in good agreement for the two morphology types, particularly for guest-based processes at low guest concentrations where guest clustering is limited.

Brice, Sara M., Doma, Kenji, and Spratford, Wayne (2021) Effect of footwear on the biomechanics of loaded back squats to volitional exhaustion in skilled lifters. Journal of Strength and Conditioning Research. (In Press)
This study examined whether footwear influences the movement dynamics of barbell back squats to volitional exhaustion in experienced lifters. Eleven men (1 repetition maximum [1RM] = 138 ± 19 kg; 1RM % body mass = 168 ± 18%) performed 3 sets (5–12 ± 4 repetitions per set) of loaded barbell back squats to volitional exhaustion using raised-heel and flat-heel footwear. Barbell motion as well as moments, angles, angular velocity, and power in the sagittal plane at the ankle, knee, hip, and lumbopelvis were examined during the second repetition of the first set (Tsecond) and the final repetition of the third set (Tfinal). There were significant reductions (p < 0.05) in lower-limb concentric angular velocity and power output for both footwear conditions. For the raised-heel condition at Tfinal, hip and knee concentric angular velocities were significantly slower (p < 0.05), and knee concentric power output was significantly less (p < 0.05) compared with the flat-heel condition. A reduction in barbell velocity was not observed for the raised-heel condition despite there being reduction in hip and knee angular velocities. Furthermore, no differences were identified in lower-limb joint moments or any of the biomechanical characteristics of the lumbopelvis between the footwear conditions. The findings of this study suggest that neither type of footwear reduced joint loading or improved joint range-of-motion.

Bainbridge, Zoe, Lewis, Stephen, Stevens, Thomas, Petus, Caroline, Lazarus, Emily, Gorman, Jessica, and Smithers, Scott (2021) Measuring sediment grain size across the catchment to reef continuum: improved methods and environmental insights. Marine Pollution Bulletin, 168. 112339.
Sediments collected within freshwater, estuarine and marine habitats were used to trial various chemical and physical pre-treatments to develop a systematic protocol for grain-size analysis using laser diffraction. Application of this protocol mitigates the influence of bio-physical processes that may transform grain-size distributions, enabling the characterisation and quantification of 'primary' mineral sediments across the complex freshwater-marine continuum to be more reliably assessed. Application of the protocol to two Great Barrier Reef (Australia) river catchments and their estuaries reveals the ecologically relevant <20 μm fraction comprises a larger component of exported sediment than existing methods indicate. These findings are highly relevant when comparing measured data to grain-size-specific modelled sediment loads and water-quality targets. Finally, adoption of the protocol also improves the environmental interpretation of the influence of 'terrigenous sediment' in marine settings, including quantification of newly-delivered flood plume sediment.

Sturman, Michael, and Oelgemoeller, Michael (2021) Process parameters in the electrochemical reduction of carbon dioxide to ethylene. ChemBioEng Reviews, 8 (3). pp. 149-188.
Ethylene is one of the most widely used chemical compounds. It is readily transformed to a variety of useful products that can replace those derived from fossil sources. Further, the ability to produce ethylene from atmospheric carbon dioxide would significantly assist in the urgent need to stabilize, and ultimately to reduce, the concentration of greenhouse gases in the atmosphere. This review covers the electrochemical reduction of carbon dioxide at copper-based cathodes. The direct production of ethylene is the focus of the review, but it is also relevant to include the important ethylene precursor and intermediate in the carbon dioxide reduction reaction, carbon monoxide. Carbon monoxide can be reduced to ethylene on a copper cathode under similar conditions to carbon dioxide. Ethanol is another potential product of the reduction of carbon dioxide at a copper cathode. It can be readily dehydrated to ethylene, further enhancing the overall yield of ethylene. The aim of the review is to show that there are many interacting parameters that influence the effectiveness and efficiency of the electrochemical reduction of carbon dioxide at copperbased cathodes.

Jiang, Chunbo, Zheng, Lianxi, and Liu, Yang (2021) Aligned carbon nanotube films for immobilization of glucose oxidase and its application in glucose biosensor. Australian Journal of Chemistry. (In Press)
Glucose oxidase (GOx) was immobilized between aligned carbon nanotube films (ACNTFs) using a cross-stackingmethod without any purification and functionalization processes. Direct electron transfer of GOx was achieved on theACNTFs with reversible redox peaks observed at the formal potential of –0.448 V. When applied to the determination ofglucose by cyclic voltammetry, the prepared enzymatic electrode exhibited a linear range from 1 to 5 mM under mediator-free physiological conditions, which makes it a promising candidate for the development of third-generation glucosebiosensors.

Griesbeck, Axel G., and Oelgemoeller, Michael (2021) IUPAC-project SYNPHO - a collection of experimental standard procedures in synthetic photochemistry. EPA Newsletters, 100. pp. 11-15.
The IUPAC project intends to collect topical experimental procedures in the field of preparative photochemistry with emphases on essential experimental and mechanistic details. This collection may become a standard for every new report on synthetic photochemistry, thus guaranteeing a maximum of reproducibility and mechanistic understanding. To achieve this, SynPho will gather a large assortment of photochemical reactions and useful synthetic methods that utilize light-initiated and/or light-driven (i.e. photon catalytic or stoichiometric) processes. These will include descriptions of reactor setups (geometries, optics, materials, lamps, filters, wavelengths) and photon-specific information (quantum yields, quantum efficiencies, absorption and emission properties of substrates, intermediates and products).

Cross, Jamie L., Huo, Chenghan, and Trinh, Kelly (2021) Returns, volatility and the cryptocurrency bubble of 2017–18. Economic Modelling, 104. 105643.
Research on cryptocurrencies has focused on price and volatility formation in isolation, however knowledge about their interdependence is important for risk management and asset allocation. We investigate the existence and nature of such a relationship in four commonly traded cryptocurrencies: Bitcoin, Ethereum, Litecoin and Ripple, during the cryptocurrency bubble of 2017–18. Using a generalized asset pricing model, we find evidence of a risk premium effect in Litecoin and Ripple during the boom of 2017, and that adverse news effects were an important driver of the cryptocurrency crash of 2018 in all four cryptocurrencies. In an out-of-sample forecasting exercise, we find that allowing for stochastic volatility and a heavy tailed distribution provides more accurate return and volatility forecasts compared to a random walk benchmark. This suggests that cryptocurrency markets were not weak-form efficient during this period.

Garcia, J.A., Waszek, L., Tauzin, B., and Schmerr, N. (2021) Automatic identification of mantle seismic phases using a Convolutional Neural Network. Geophysical Research Letters, 48 (18). e2020GL091658.
Typical seismic waveform data sets comprise hundreds of thousands to millions of records. Compilation is performed by time-consuming handpicking of phase arrival times, or signal processing algorithms such as cross-correlation. The latter generally underperform compared to handpicking. However, differences in picking methods creates variations in models and interpretation of Earth's structure. Here, we exploit the pattern recognition capabilities of Convolutional Neural Networks (CNN). Using a large handpicked data set, we train a CNN model to identify the seismic shear phase SS. This accelerates, automates, and makes consistent data compilation, a task usually completed by visual inspection and influenced by scientists' choices. The CNN model is employed to identify precursors to SS generated by mantle discontinuities. It identifies precursors in stacked and individual seismograms, producing new measurements of the mantle transition zone with quality comparable to handpicked data. This rapid acquisition of high-quality observations has implications for automation of future seismic tomography studies.

Biggs, J.S., Everingham, Y., Skocaj, D.M., Schroeder, B.L., Sexton, J., and Thorburn, P.J. (2021) The potential for refining nitrogen fertiliser management through accounting for climate impacts: an exploratory study for the Tully region. Marine Pollution Bulletin, 170. 112664.
Increasing the precision of nitrogen (N) fertiliser management in cropping systems is integral to increasing the environmental and economic sustainability of cropping. In a simulation study, we found that natural variability in year-to-year climate had a major effect on optimum N fertiliser rates for sugarcane in the Tully region of northeastern Australia, where N discharges pose high risks to Great Barrier Reef ecosystems. There were interactions between climate and other factors affecting crop growth that made optimum N rates field-specific. The regional average optimum N fertiliser rate was substantially lower than current industry guidelines. Likewise, simulated N losses to the environment at optimum N fertiliser rates were substantially lower than the simulated losses at current industry fertiliser uidelines. Dissolved N discharged from rivers is related to fertiliser applications. If the reductions in N applications identified in the study occurred in the Tully region, the reduction in dissolved N discharges from rivers in the region would almost meet current water quality improvement targets. Whilst there were many assumptions made in this exploratory study, and there are many steps between the study and a practically implemented dynamic N fertiliser recommendation system, the potential environmental benefits justify field validation and further development of the concepts identified in the study.

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