General Correlation Research Articles

Water quality and cyanobacterial blooms in the Piancó-Piranhas-Açu Watershed, Semi-arid Region of Northeastern Brazil: relationships with education toward sustainability

Greater emphasis has been attached to aquatic ecosystems in recent decades, as these are associated with indicators determinant of sustainability indices. The environmental impacts of these ecosystems with potential risk to human health in the semi-arid region of the state of Rio Grande do Norte have been frequently observed. This study aimed at evaluating the cyanobacteria density, and the indices that indicate the Piancó-Piranhas-Açu Watershed quality. It also targeted to identify the factors that impact most the blooming of these aquatic organisms. The sampling design consisted of 12 collections in different seasonal periods from 2009 to 2016, carried out by the Água Azul Program on 6 points along the basin. Environmental variables were used to analyze the Water Quality Index (WQI), Trophic State Index (TSI), and Cyanobacteria Density (CD). The mean WQI indicated ‘Regular’ water status for points PPA3 and PPA4, while PPA1, PPA2, PPA5 and PPA6 resulted in ‘Good’. As for the TSI, the levels indicate average degree of eutrophication (mesotrophy) on three sampling points, high degree of eutrophication (eutrophy) on two points, and low degree of eutrophication (oligotrophy) on one point. In this sense, human activities - especially diffuse polluting sources - around the spring seemed to worsen these scenarios. The density of potentially toxic cyanobacteria was high, exceeding CONAMA Resolution 357/2005 that recommends a maximum value of 50,000 cells/mL, and the Ministry of Health Ordinance 2914/2011 that recommends a threshold of 20,000 cells/mL. Regarding the general correlation between CD and seasonality we found significant influence (p < 0.05), with greater proliferation of these organisms directly related to periods of drought. We concluded that although the WQI indicated that dams’ waters are suitable for multiple uses, the TSI had limitations, considering the excessive primary productions associated with the presence of cyanobacteria and, thus, the potential occurrence of cyanotoxins ensuing from pollutant loads. The study led us to conclude that the adoption of education practices toward sustainability would help environmental preservation and local social development. It would also enable the establishment of effective priority public policies on mitigation of water pollution.

On the achievable secrecy transmission rates by Alamouti space‐time block coding in time‐selective fading channels

In this letter, the authors study the security performance of Alamouti space-time block coding (STBC) with two different linear detection strategies, linear maximum likelihood (LML) and zero-forcing (ZF), over time-selective Rayleigh fading channels. Specifically, the connection and secrecy outage probabilities for general temporal correlation when the legitimate receiver and eavesdropper adopt the LML and ZF detectors are first derived. Then the secrecy transmission rates for various combinations of LML and ZF detectors at the legitimate receiver and eavesdropper are derived. The authors also found that the optimal control of the codeword rate and secrecy rate can maximize the secrecy transmission rates.

Effect of pressure on structural, elastic and mechanical properties of cubic perovskites XCoO3 (X = Nd, Pr) from first-principles investigations

In this current research article, the structural elasto-mechanical and thermal properties of cubic perovskites XCoO3 (X = Nd, Pr) have been studied theoretically under different pressures. The structure is optimized and calculated optimized data is in well agreement of available literature. All these calculations are performed by considering Perdew Burke Ernzerhof Generalized Gradient Approximation type exchange and correlation functional within Wien2k-code. The second order cubic independent elastic constants C11, C12 and C44 are computed by using this optimized data. The dynamical stability criteria is checked by computed constants and used to find the elastic moduli; shear, Young's and Bulk modulus. The other mechanical properties like Poisson's ratio, anisotropic factor, Pugh's ratio, shear constant, Cauchy pressure, Lame's constants, Kleinmann parameter are quantified and discussed. The results portray the ductility of XCoO3 (X = Nd, Pr) perovskites and utility in high temperature devices.

Vermont-wide assessment of anthropogenic background concentrations of perfluoroalkyl substances in surface soils

Shallow surface soils from 66 suburban sampling locations across Vermont were analyzed for 17 different perfluoroalkyl acids (PFAA). PFAA were detected in all 66 surface soils, with a total concentration of PFAA ranging from 540 to 36,000 ng/kg dry soil weight (dw). Despite the complexity of site-specific factors, some general trends and correlations in PFAA concentrations were observed. For instance, perfluoro-1-octanesulfonate (PFOS) dominated in all soil samples while seven other PFAA, including perfluoro-n-nonanoic acid, perfluoro-n-octanoic acid, perfluoro-n-hexanoic acid, perfluoro-n-heptanoic acid, perfluoro-n-decanoic acid, perfluoro-n-undecanoic acid, perfluoro-1-butanesulfonate, and perfluoro-1-hexanesulfonate (PFNA, PFOA, PFHxA, PFHpA, PFDA, PFUnDA, and PFBS, respectively), were identified at more than 50 % of the locations. Perfluoroalkyl carboxylic acids (PFCA) showed a positive correlation with total organic carbon, whereas no clear correlation was observed for perfluoroalkyl sulfonate acids (PFSA). In addition, variations in geographical distributions of PFAA were observed, with relatively higher total PFAA in northern regions when compared to Southern Vermont. Moreover, PFHxA, PFNA, PFDA, PFUnDA, PFOS, and total PFAA were positively correlated to land-use types in Northern Vermont. These results are useful for understanding unique behaviors of PFCA vs. PFSA in geospatially distributed surface soils and for providing anthropogenic background data for setting PFAS cleanup standards for surface soils.

Out-of-sample validation of a general correlation for steam condensation in the presence of air over a vertical slender tube in turbulent free convection

In a previous work [Dehbi, 2015], a general correlation was proposed for the prediction of steam condensation rates in the presence of air over vertical flat surfaces in turbulent free convection. Because most of the heat transfer data were obtained from tube condenser tests, the Popiel [2008] correction for curvature was employed to transfer results to flat plate surfaces. Popiel’s correlation is valid for laminar flows, and hence, as shown in subsequent investigations [Dehbi, 2021], it predicts mostly lower values for the curvature correction factors if applied to turbulent flows. Hereafter, we first revisit the flat surface correlation presented in [Dehbi, 2015] and update its form based on the more accurate curvature correction given in [Dehbi, 2021]. The updated flat plate correlation, along with the curvature correction, is subsequently used to predict heat transfer rates in five experiments conducted recently on slender vertical tubes, covering tube diameters from 12 mm to 38.1 mm, steam mass fraction from 0.2 to 0.90, wall temperature subcooling from 4 K to 120 K, and pressures from 1 to 16 bars. It is demonstrated that the general correlation provides very good out-of-sample predictions of the data, with a standard deviation of 13.3 %, which is typical of experimental uncertainty.

Methods of Esthetic Assessment after Adjuvant Whole-Breast Radiotherapy in Breast Cancer Patients: Evaluation of the BCCT.core Software and Patients' and Physicians' Assessment from the Randomized IMRT-MC2 Trial.

Simple SummaryTo validate the BCCT.core software, the present analysis compares the esthetics assessment by the software in relation to patients’ and physicians’ rating in breast cancer patients after surgery and adjuvant radiotherapy. Agreement rates of the different assessments and their correlation with breast asymmetry indices were evaluated. The assessments of the software and the physicians were significantly correlated with all asymmetry indices, while for patients’ self-assessment, this general correlation was first seen after 2 years. Only a slight agreement between the BCCT.core software and the physicians’ or patients’ assessment was seen, while a moderate and substantial agreement was detected between the physicians’ and the patients’ assessments. The BCCT.core software is a reliable tool to measure asymmetries, but may not sufficiently evaluate the esthetic outcome as perceived by patients. It may be more appropriate for a long-term follow-up, when symmetry seems to increase in importance.The present analysis compares the esthetics assessment by the BCCT.core software in relation to patients’ and physicians’ ratings, based on the IMRT-MC2 trial. Within this trial, breast cancer patients received breast-conserving surgery (BCS) and adjuvant radiotherapy. At the baseline, 6 weeks, and 2 years after radiotherapy, photos of the breasts were assessed by the software and patients’ and physicians’ assessments were performed. Agreement rates of the assessments and their correlation with breast asymmetry indices were evaluated. The assessments of the software and the physicians were significantly correlated with asymmetry indices. Before and 6 weeks after radiotherapy, the patients’ self-assessment was only correlated with the lower breast contour (LBC) and upward nipple retraction (UNR), while after 2 years, there was also a correlation with other indices. Only a slight agreement between the BCCT.core software and the physicians’ or patients’ assessment was seen, while a moderate and substantial agreement was detected between the physicians’ and the patients’ assessment after 6 weeks and 2 years, respectively. The BCCT.core software is a reliable tool to measure asymmetries, but may not sufficiently evaluate the esthetic outcome as perceived by patients. It may be more appropriate for a long-term follow-up, when symmetry appears to increase in importance.

Analytical pricing formulae for variance and volatility swaps with a new stochastic volatility and interest rate model

We introduce an additional factor in the Heston-CIR model to form a new hybrid model in this paper. This new model features a more general correlation structure with the interest rate being correlated with the underlying asset, while still preserving the analytical tractability. We derive a series solution to the forward characteristic function when solving a time-dependent Riccati equation, after the measure transform is performed, so that variance and volatility swap prices can be finally written in an analytical form. The theoretical results are also accompanied with some numerical results demonstrating its potential of complementing the usage of the currently adopted non-correlated Heston-CIR model.

Hybrid quantum-classical algorithm for computing imaginary-time correlation functions

Quantitative descriptions of strongly correlated materials pose a considerable challenge in condensed matter physics and chemistry. A promising approach to address this problem is quantum embedding methods. In particular, the dynamical mean-field theory (DMFT) maps the original system to an effective quantum impurity model comprising correlated orbitals embedded in an electron bath. The biggest bottleneck in DMFT calculations is numerically solving the quantum impurity model, i.e., computing the Green's function. Past studies have proposed theoretical methods to compute the Green's function of a quantum impurity model in polynomial time using a quantum computer. So far, however, efficient methods for computing the imaginary-time Green's functions have not been established despite the advantages of the imaginary-time formulation. We propose a quantum-classical hybrid algorithm for computing imaginary-time Green's functions on quantum devices with limited hardware resources by applying the variational quantum simulation. Using a quantum circuit simulator, we verified this algorithm by computing Green's functions for a dimer model as well as a four-site impurity model obtained by DMFT calculations of the single-band Hubbard model, although our method can be applied to general imaginary-time correlation functions.

Experimental study on heat transfer of dense phase flow through a horizontal tube under constant wall flux conditions

A novel application of particles is utilization as dense phase flow for heat capture, transportation and storage. The use of horizontal dense phase flow as heat transfer fluid in solar systems is discussed with respect to current technologies. The investigation aims to analyze the heat transfer behavior of a horizontal dense phase flow under the condition of uniform surface heat flux. The proposed technologies transport particles as semi-continuous plug flow with a bottom layer, particles at the bottom layer will regularly renew once plugs pass by. Tests were conducted in a self-pilot scale-up platform. The measured wall-to-mixture heat transfer coefficient varies from ∼303 to 813 W/m2K in the particle mass flux range from 125 to 777 kg/m2s. Three heat transfer equations will be provided with the experimental data. A heat transfer equation describes the wall-to-mixture heat transfer coefficient linearly increases with particle mass flux. Then, a general empirical correlation in a dimensionless form predicted results well with experimental data of the present work and other data reported in the literature. Furthermore, a mechanistic heat transfer model is proposed according to a partial penetration mechanism and multi-layer flow model. The predicted results agree with experimental results within 12% of the average error. Considering the findings in this paper, researchers may have ideas to improve the heat transfer of horizontal dense phase flow to utilize this technology to the parabolic concentrator for the solar thermal industry.

Estimate of Temperature Gradients of Thin-Walled Structures Under Thermomechanical Fatigue Loading

Temperature gradients are significant in the fatigue life assessment. Thermal loading conditions were suspected to affect temperature gradients and thermal stresses in structures. In the present work, thin-walled plates and tubes were experimentally investigated to quantify the effects of thermal loads on the through-thickness temperature gradients, and finite element models were developed based on the experiments and used to generate more general correlations. It is confirmed that both transient peak temperature gradient and steady-state values are linear to heating power and cooling conditions, and are insensitive to plate thicknesses. By introducing the nondimensional temperature gradient, the temperature distribution in thin-walled structures can be estimated with reasonable accuracy.

Modern pollen–vegetation relationships along an altitudinal transect in the Western Higher Himalaya, India: Palaeoclimatic and anthropogenic implications

Palynology is one of the most reliable tools for the reconstruction of past vegetation and climate and modern pollen analogues are important for the calibration of fossil pollen assemblages. The present study analyses the pollen–vegetation relationships along a steep altitudinal gradient (2700–3680 m), in the western Higher Himalayan region. On the basis of altitude, three vegetation zones were demarcated: Zone I (2700–3100 m) is composed of mixed-temperate forest vegetation, dominated by Quercus semecarpifolia and Rhododendron arboreum; Zone II (3100–3250 m) is marked by sub-alpine forest vegetation, characterised by R. campanulatum and R. barbatum, along with Abies spectabilis and Q. semecarpifolia; Zone III (3250–3680 m) is above the tree-line (3250 m) and represented by alpine-scrub and meadows. Thirty-five surface soil samples (twenty, seven and eight from each zone, respectively) were analysed along the altitudinal transect to decode the representation of the extant vegetation in the pollen-rain. The pollen–vegetation relationship is non-linear due to the over-representation of extra-local Pinus pollen in each zone. Nonetheless, the modern pollen assemblages show a general correlation with the local broad-leaved taxa and the herbaceous elements; with the exception of Rhododendron pollen, which is under-represented. Among the non-pollen palynomorphs (NPPs), the presence of coprophilous fungal spores is compatible with the grazing activities in the area. Multivariate statistical analyses performed on the surface pollen data indicate that the dataset can efficiently distinguish the different vegetation zones across the altitudinal gradient. This work provides the modern analogues for pollen-based palaeoclimatic reconstructions for the Western-Higher Himalayan region, and would also help to decipher the inception and intensification of anthropogenic activities in the region.

Gaussian Process Subspace Prediction for Model Reduction

Subspace-valued functions arise in a wide range of problems, including parametric reduced order modeling (PROM), parameter reduction, and subspace tracking. In PROM, each parameter point can be associated with a subspace, which is used for Petrov--Galerkin projections of large system matrices. Previous efforts to approximate such functions use interpolations on manifolds, which can be inaccurate and slow. To tackle this, we propose a novel Bayesian nonparametric model for subspace prediction: the Gaussian process subspace (GPS) model. This method is extrinsic and intrinsic at the same time: with multivariate Gaussian distributions on the Euclidean space, it induces a joint probability model on the Grassmann manifold, the set of fixed-dimensional subspaces. The GPS adopts a simple yet general correlation structure, and a principled approach for model selection. Its predictive distribution admits an analytical form, which allows for efficient subspace prediction over the parameter space. For PROM, the GPS provides a probabilistic prediction at a new parameter point that retains the accuracy of local reduced models, at a computational complexity that does not depend on system dimension, and thus is suitable for online computation. We give four numerical examples to compare our method to subspace interpolation, as well as two methods that interpolate local reduced models. Overall, GPS is the most data efficient, more computationally efficient than subspace interpolation, and gives smooth predictions with uncertainty quantification.

Measurement and scaling of turbulent burning velocity of ammonia/methane/air propagating spherical flames at elevated pressure

This study reports the accurate laminar burning velocity, turbulent burning velocity and its correlations of ammonia/methane/air propagating spherical flames. The experiments were carried out on a medium-scale, fan-stirred cylindrical combustion chamber with ammonia molar content varying from 20% to 60% and the initial pressure up to 3 bar. The turbulent burning velocity decreases with the ammonia content due to the weakening effect of the laminar burning velocity under all turbulence intensities and pressures studied. Since the weakening of flame chemistry is dominated by the enhancement of turbulence eddies, the normalized turbulent burning velocity increases with the ammonia content. The turbulent expanding flame of ammonia/methane/air is self-similar under different ammonia content. This self-similar propagation follows the one-half power-law correlation between the normalized turbulent burning velocity, ST/SL, and the turbulent flame Reynolds number, which is quantitatively consistent with that of unity Lewis number methane/air flames (Chaudhuri 2012). The pressure dependence of turbulent burning velocity can be represented roughly as a 0.4 power law of ST/SL and (u′/SL)(P/P0). However, there is a quantitative gap between the pre-exponential factor of the present experimental data and the literature data based on this correlation, which could attribute to the difference in the turbulence eddy scales of different experimental apparatus. The integral length scale characterized the largest turbulence eddies is introduced to consider the turbulent length scale effect. A modified general correlation ST/SL∼(LI/L0)0.5[(u′/SL)(P/P0)]0.41 with the consideration of the integral length scale effect is obtained, which is able to predict a variety of spherical flame data regardless of temperatures, pressures, and fuel types. In addition, it is verified that turbulent burning velocity of ammonia flame could be expressed by the correlation of Karlovitz and Damköhler numbers: ST/SL∼Ka·Da=ReT,flow0.5. It can be seen that ammonia has similar turbulent combustion characteristics as hydrocarbon fuel. These findings indicate that it is feasible to simulate and optimize ammonia combustors utilizing previous turbulent burning velocity correlations based on hydrocarbon fuel.

Variational methods for contracting projected entangled-pair states

The norms or expectation values of infinite projected entangled-pair states (PEPS) cannot be computed exactly, and approximation algorithms have to be applied. In the last years, many efficient algorithms have been devised -- the corner transfer matrix renormalization group (CTMRG) and variational uniform matrix product state (VUMPS) algorithm are the most common -- but it remains unclear whether they always lead to the same results. In this paper, we identify a subclass of PEPS for which we can reformulate the contraction as a variational problem that is algorithm independent. We use this variational feature to assess and compare the accuracy of CTMRG and VUMPS contractions. Moreover, we devise a new variational contraction scheme, which we can extend to compute general N-point correlation functions.

General heat transfer correlations for supercritical carbon dioxide heated in vertical tubes for upward and downward flows

Supercritical CO2 is a promising working fluid for many industrial applications. To improve the performances of relevant components and systems, the prediction of the heat transfer of supercritical CO2 is an important research topic. General explicit heat transfer correlations of supercritical CO2 for upward and downward flows heated in circular tubes were established using the genetic programming (GP) method. A total of 12720 experimental data points from 22 publications were collected to develop the models. The data included hydraulic diameter from 0.0992 to 22 mm, bulk temperature from -6.0 to 134.5°C, pressure from 7.44 to 10.50 MPa, mass flux from 50 to 4834 kg•(m2•s)−1, heat flux from 2.9 to 748 kW•m−2 and wall temperature from 6.4 to 368.2°C. The database was divided into four parts according to the flow direction and the relationship between the bulk temperature and the pseudo-critical temperature. The developed correlations considered various non-dimensional parameters as the independent variables to reflect the effects of supercritical properties, flow acceleration and buoyancy on the heat transfer. The results showed that the proposed correlations had excellent accuracy with a mean absolute relative error (MARE) of 20.10% based on prediction with the iterated wall temperature. The developed correlations outperformed the existing correlations in the literature. Compared to other correlations, the trend analysis indicated that these newly developed correlations could appropriately present the physics sense when the condition parameters varied.

Specificity of Nuclear Size Scaling in Frog Erythrocytes.

In eukaryotes, the cell has the ability to modulate the size of the nucleus depending on the surrounding environment, to enable nuclear functions such as DNA replication and transcription. From previous analyses of nuclear size scaling in various cell types and species, it has been found that eukaryotic cells have a conserved scaling rule, in which the nuclear size correlates with both cell size and genomic content. However, there are few studies that have focused on a certain cell type and systematically analyzed the size scaling properties in individual species (intra-species) and among species (inter-species), and thus, the difference in the scaling rules among cell types and species is not well understood. In the present study, we analyzed the size scaling relationship among three parameters, nuclear size, cell size, and genomic content, in our measured datasets of terminally differentiated erythrocytes of five Anura frogs and collected datasets of different species classes from published papers. In the datasets of isolated erythrocytes from individual frogs, we found a very weak correlation between the measured nuclear and cell cross-sectional areas. Within the erythrocytes of individual species, the correlation of the nuclear area with the cell area showed a very low hypoallometric relationship, in which the relative nuclear size decreased when the cell size increased. These scaling trends in intra-species erythrocytes are not comparable to the known general correlation in other cell types. When comparing parameters across species, the nuclear areas correlated with both cell areas and genomic contents among the five frogs and the collected datasets in each species class. However, the contribution of genomic content to nuclear size determination was smaller than that of the cell area in all species classes. In particular, the estimated degree of the contribution of genomic content was greater in the amphibian class than in other classes. Together with our imaging analysis of structural components in nuclear membranes, we hypothesized that the observed specific features in nuclear size scaling are achieved by the weak interaction of the chromatin with the nuclear membrane seen in frog erythrocytes.

Human Foot Traffic and the Associated Spread of Invasive Species


 
 
 
 The spread of invasive species has become an important topic in ecological literature in recent years as it threatens the natural biodiversity essential for ecosystems to function and thrive. Invasive species are damaging to ecosystems because they outcompete native species for invaluable resources. Human activities have long been suspected of being the main vector for the transportation of invasive species due to the attachment of seeds to objects such as clothing, shoes, livestock, and vehicles. Gaining an understanding of the interactions between human activity and invasive species spread is crucial to diminish the negative impact of invasive species on local ecosystems. In our research endeavor, we investigated human foot traffic in urban parks and conservation areas and surveyed the surrounding area for invasive plant species. In several different parks, we set up plots with varying levels of human foot traffic and designated each as low, medium, and high foot traffic. We measured each of the plants within the plots, denoting each as invasive or non-invasive. We also measured observed foot traffic to confirm the accuracy of the designated foot traffic levels and to create a traffic gradient. We found a general correlation between high foot traffic and abundant invasive species, which supports our hypothesis. It is important to note that there remains many other factors that influence invasive species' spread that should be investigated. Further research should be conducted on the mechanisms behind this spread and how it can be reduced.
 
 
 

Numerical analysis of performance uncertainty of heat exchangers operated with nanofluids

In this paper, we analyse the performance of two types of heat exchangers with nanofluid as the working fluid in turbulent flow regime ( R e ≈ 4, 000–180, 000). Based on the experimental uncertainty of the thermophysical properties of the nanofluids, we use the Stochastic Collocation Method in combination with a deterministic simulation programme to estimate the expected value and variance of the targeted engineering results. We find that the uncertainty in the thermal conductivity of the nanofluid has the largest impact on the uncertainty in the heat exchanger performance, while the uncertainty in the density can be neglected. The uncertainties in the Nusselt number, friction factor and several figures of merit are smaller than the change in these performance estimators due to a change in nanoparticle concentration. Predictions for heat exchanger performance agree much better with experimental data when used with empirical heat transfer correlations developed specifically for nanofluids than with the general Gnielinski correlation developed for pure fluids. We also perform a correlation analysis of the relationships between heat exchanger performance enhancement and pressure drop to show that they are strongly correlated. We find that the relationship between the concentration of nanoparticles and the Nusselt number is statistically insignificant. The R e − N u relationship is significant, indicating the importance of flow conditions. The correlation between nanoparticle concentration and friction factor is significant and strong. This result suggests that the optimisation of the thermal-hydrodynamic behaviour should be sought in a parameter other than the nanoparticle volume fraction.

Spatiotemporal heterogeneous effects of socio-demographic and built environment on private car usage: An empirical study of Kunming, China

The increasing car usage has caused a series of social and environmental problems. Most previous studies examined the general correlations between the determinants and the usage pattern of private car by establishing global regression models. These models ignore the variation of travel behavior across temporal and spatial dimensions, which possibly leads to wrong bias and overlooks certain momentous details. Considering this research gap, this paper explores the influence of determinants on the time-of-day car usage pattern, using the multi-source data collected from the city of Kunming, China. It applies a geographically and temporally weighted regression (GTWR) model to investigate the heterogeneous relationship between on the hourly mode share of private car and the factors of individual attributes and built environment. The empirical results show that the GTWR model produces better goodness-of-fit compared with global regression model, as well as geographically weighted regression (GWR) model. It suggests that most explanatory variables are spatiotemporal non-stationary associated with hourly car share. A visualization method is applied to analyze the temporal variation of the coefficients of socio-demographic attributes and built environment variables, and to reveal the spatial distribution of the effects of determinants during peak periods. The empirical results show that both of selected the socio-demographic and built environment attributes have heterogeneous effect on the car share in time and space dimensions. For example, the proportion of college or college above presents stronger negative effect on the share of private car in the afternoon peak than in the morning peak, the negative impact of the densities of built environment (i.e., road, population, and bus stop) is more significant in underdeveloped area. Finally, insightful policy recommendations for different urban areas are presented to encourage the reduction of car usage and alleviate urban traffic problems.

Binding characteristics of copper onto biochar-derived DOM using general, heterospectral and moving-window two-dimensional correlation analyses

Dissolved organic matter released from biochar (biochar-derived DOM, BDOM) could dominate the environmental behavior and fate of trace metals by forming BDOM-metal complexes. Here general, heterospectral as well as moving-window (MW) two-dimensional correlation spectroscopy (2DCOS) analyses of synchronous fluorescence and Fourier transform infrared spectra were employed to explore the heterogeneous binding characteristics between sludge BDOM and Cu(II). The results revealed that Cu-BDOM binding first occurred in the fulvic-like (368–380 nm), then humic-like (428 nm) fluorescent fractions, followed by infrared groups of phenolic hydroxyl groups, carboxylate, COH of polysaccharide groups, CC of aromatic carbon, CH of aliphatics and COC of aliphatic ethers. The binding affinity of the hydrophilic groups was stronger than that of hydrophobic groups in BDOM towards Cu(II). Fluorescence components in BDOM played a decisive role in the binding of Cu(II) with trace concentration (1 μM), while infrared functional groups made a substantial contribution in the complexation of Cu(II) with higher concentration (10–100 μM). The concentration of final configuration transformation point (11.7 μmol/mg in this study) by MW2DCOS analysis was suggested as an actual binding threshold that was helpful for evaluating their environmental behaviors.