Shot-to-shot two-dimensional photon intensity diagnostics within megahertz pulse-trains at the European XFEL.

Characterizing the properties of X-ray free-electron laser (XFEL) sources is a critical step for optimization of performance and experiment planning. The recent availability of MHz XFELs has opened up a range of new opportunities for novel experiments but also highlighted the need for systematic measurements of the source properties. Here, MHz-enabled beam imaging diagnostics developed for the SPB/SFX instrument at the European XFEL are exploited to measure the shot-to-shot intensity statistics of X-ray pulses. The ability to record pulse-integrated two-dimensional transverse intensity measurements at multiple planes along an XFEL beamline at MHz rates yields an improved understanding of the shot-to-shot photon beam intensity variations. These variations can play a critical role, for example, in determining the outcome of single-particle imaging experiments and other experiments that are sensitive to the transverse profile of the incident beam. It is observed that shot-to-shot variations in the statistical properties of a recorded ensemble of radiant intensity distributions are sensitive to changes in electron beam current density. These changes typically occur during pulse-distribution to the instrument and are currently not accounted for by the existing suite of imaging diagnostics. Modulations of the electron beam orbit in the accelerator are observed to induce a time-dependence in the statistics of individual pulses - this is demonstrated by applying radio-frequency trajectory tilts to electron bunch-trains delivered to the instrument. We discuss how these modifications of the beam trajectory might be used to modify the statistical properties of the source and potential future applications.

Inadvertently Generated PCBs in Consumer Products: Concentrations, Fate and Transport, and Preliminary Exposure Assessment.

Although commercial polychlorinated biphenyl (PCB) production was banned in 1979 under the Toxics Substance Control Act, inadvertent generation of PCBs through a variety of chemical production processes continues to contaminate products and waste streams. In this research, a total of 39 consumer products purchased from local and online retailer stores were analyzed for 209 PCB congeners. Inadvertent PCBs (iPCBs) were detected from seven products, and PCB-11 was the only congener detected in most of the samples, with a maximum concentration exceeding 800 ng/g. Emission of PCB-11 to air was studied from one craft foam sheet product using dynamic microchambers at 40 °C for about 120 days. PCB-11 migration from the product to house dust was also investigated. The IAQX program was then employed to estimate the emissions of PCB-11 from 10 craft foam sheets to indoor air in a 30 m3 room at 0.5 h-1 air change rate for 30 days. The predicted maximum PCB-11 concentration in the room air (156.8 ng/m3) and the measured concentration in dust (20 ng/g) were applied for the preliminary exposure assessment. The generated data from multipathway investigation in this work should be informative for further risk assessment and management for iPCBs.

Optimal monitoring locations for identification of ambivalent characteristics of groundwater pollution sources.

Increasing pollution in the environment, particularly for groundwater, has been an issue of great concern for decades. Thus, proper management strategies need to be adopted for reclamation of such polluted groundwater aquifers. Success of these reclamation strategy relies on the precision with which the pollution source characteristics (location of sources, release flux histories, and the starting times of pollutant sources) are identified. In clandestine scenarios of groundwater pollution where neither the location nor starting times of pollutant sources are known, it is impossible to decide where to install a monitoring well. Therefore, an optimally designed pollutant data monitoring plan is needed to reduce the time and cost of monitoring and simultaneously achieve greater accuracy in identification of source characteristics. To address this issue, a principal component analysis (PCA)-based methodology is proposed to design an efficient well network for identifying unknown characteristics of pollutant sources (UCPS). PCA is applied to reduce the dimensionality of a dataset comprising a large number of interrelated variables, thus reducing the uncertainty due to ambivalent source characteristics.

Source characterization and health risks of BTEX in indoor/outdoor air during winters at a terai precinct of North India.

BTEX are the consistently found air contaminants in indoor and outdoor environments. In order to investigate the exposure levels of BTEX, the indoor and outdoor air was analyzed during winter season at homes located at four selected sites of Gorakhpur, Uttar Pradesh, India, which comprised residential, roadside, industrial and agricultural areas. BTEX were sampled with a low-flow pump (SKC model 220). Samples were extracted with CS2 and the aromatic fraction was subjected to GC-FID. Mean indoor concentration of BTEX was highest at the agricultural (70.9 µg m-3) followed by industrial (30.0 µg m-3), roadside (17.5 µg m-3) and residential site (11.8 µg m-3). At outdoor locations, the mean BTEX levels were highest at the roadside (22.0 µg m-3) followed by industrial (18.7 µg m-3), agricultural (11.0 µg m-3) and residential site (9.1 µg m-3). The I/O ratios were greater than 1 at all the sites except roadside site, where I/O ratios for toluene, ethylbenzene and xylene were less than unity. Poor correlation between indoor and outdoor levels at each site further indicated the dominance of indoor sources. Factor analysis followed by one-way analysis of variance depicts that the presence of BTEX compounds at all the sites indicate a mixture of vehicular and combustion activities. For benzene, the ILTCR values exceeded the safe levels, whereas ethylbenzene was nearby to the recommended level 1 × 10-6. The HQ values were above unity for agricultural (indoors) and industrial (outdoors) as an exception to all the other sites which indicted the value below unity.

Assessment of Elemental Components in Atmospheric Particulate Matter from a Typical Mining City, Central China: Size Distribution, Source Characterization and Health Risk.

Atmospheric particulate matters in nine size fractions were sampled at Huangshi city, Hubei province. Elemental concentrations occurred unimodal size distribution for Zn, Pb and Ni, dimodal distribution for Ca, S, Fe and Ti, and trimodal distribution for Cl, K, Mn, Cu and Cr. Enrichment factor and principal component analysis identified the main sources from crustal material, biomass burning, waste incineration, vehicular and industrial emission. As for the non-carcinogenic health risk through inhalation, there were certain potential risks for Mn and Sb for children, and Pb for children and adults in PM2.5. It showed certain potential risks for Mn, Sb and Pb for children and adults in PM10. As for the carcinogenic health risk through inhalation, Cr in PM2.5 and Ni, Co and Cr in PM10 indicated unacceptable risk for children and adults. Meanwhile, Co and Ni in PM2.5 represented acceptable risk for children.

Photochemical oxidation of VOCs and their source impact assessment on ozone under de-weather conditions in Western Taiwan.

The application of statistical models has excellent potential to provide crucial information for mitigating the challenging issue of ozone (O3) pollution by capturing its associations with explanatory variables, including reactive precursors (VOCs and NOX) and meteorology. Considering the large contribution of O3 in degrading the air quality of western Taiwan, three-year (2019-2021) hourly concentration data of VOC, NOX and O3 from 4 monitoring stations of western Taiwan: Tucheng (TC), Zhongming (ZM), Taixi (TX) and Xiaogang (XG), was evaluated to identify the effect of anthropogenic emissions on O3 formation. Owing to the high-ambient reactivity of VOCs on the underestimation of sources, photochemical oxidation was assessed to calculate the consumed VOC (VOCcons) which was followed by the source identification of their initial concentrations. VOCcons was observed to be highest in the summer season (16.7 and 22.7 ppbC) at north (TC and ZM) and in the autumn season (17.8 and 11.4 ppbC) in southward-located stations (TX and XG, respectively). Results showed that VOCs from solvents (25-27%) were the major source at northward stations whereas VOCs-industrial emissions (30%) dominated in south. Furthermore, machine learning (ML): eXtreme Gradient Boost (XGBoost) model based de-weather analysis identified that meteorological factors favor to reduce ambient O3 levels at TC, ZM and XG stations (-67%, -47% and -21%, respectively) but they have a major role in accumulating the O3 (+38%) at the TX station which is primarily transported from the upwind region of south-central Taiwan. Crucial insights using ML outputs showed that the finding of the study can be utilized for region-specific data-driven control of emission from VOCs-sources and prioritized to limit the O3-pollution at the study location-ns as well as their accumulation in distant regions.

Calculation of response parameters for a neutron long counter instrument.

The primary goal of this study was to develop a simulation model of a long counter available at Canadian Nuclear Laboratories (CNL). Using the Monte Carlo N-Particle version 6 (MCNP6) code, the model was used to calculate, as a function of incident energy, the number of counts recorded per source neutron, effective centre, and sensitivity. This study also carried out measurements of the neutron emission rate of and direct neutron flux at 2 m from an in-house 252Cf neutron source.

Bidirectional machine learning-assisted sensitivity-based stochastic searching approach for groundwater DNAPL source characterization.

In this study, we designed a machine learning-based parallel global searching method using the Bayesian inversion framework for efficient identification of dense non-aqueous phase liquid (DNAPL) source characteristics and contaminant transport parameters in groundwater. Swarm intelligence organized hybrid-kernel extreme learning machine (SIO-HKELM) was proposed to approximate the forward and inverse input-output correlation with a high accuracy using the DNAPL transport numerical simulation model. An adaptive inverse-HKELM was established for preliminary estimation of the source characteristics and contaminant transport parameters to correct prior information and generate high-quality initial starting points of parallel searching. A local accurate forward-HKELM surrogate of the numerical model was embedded in the searching system for avoiding repetitive CPU-demanding likelihood evaluations. A sensitivity-based Metropolis criterion (MC), incorporating the dynamic particle swarm optimization (SD-PSO) algorithm, was developed for improving the search ergodicity and realizing precise inversion of all the unknown variables with drastic variations in sensitivity to the likelihood function. Results showed that the generalization capability and robustness of SIO-HKELM were superior to those of the traditional machine learning methods, including KELM and support vector regression (SVR), and it sufficiently approximated the forward and inverse input-output mapping of the numerical model with testing determination coefficients of 0.9944 and 0.6440, respectively. With high-quality prior information and initial starting points generated by the adaptive inverse-HKELM feed approach, the uncertainty in the inversion outputs was reduced, and the searching process rapidly converged to reasonable posterior distributions in around 60 iterations. Compared with the widely used multichain Markov chain Monte Carlo (MCMC) approach, the parallel searching lines generated by SD-PSO-MC adequately covered the searching space, and the "equifinality" effect was more effectively restrained by reducing the relative errors of all the point estimations to less than 8%. Therefore, the real source information reflected by the statistical characteristics of the SD-PSO-MC inversion outputs was more precise than that obtained using the multichain MCMC approach.

Micrometeorological Methods for the Indirect Estimation of Odorous Emissions.

Odors are typically released into the atmosphere as diffuse emissions from area and volume sources, whose detailed quantification in terms of odor emission rate is often hardly achievable by direct source sampling. Indirect methods, involving the use of micrometeorological methods in order to correlate downwind concentrations to the emission rates, are already mentioned in literature, but rarely found in real applications for the quantification of odor emissions. The instrumentation needed for the development of micrometeorological methods has nowadays become accessible in terms of prices and reliability, thus making the implementation of such methods to industrial applications more and more interesting. For this reason, this work aims to provide an overview of micrometeorological methods and investigate their effective applicability to odors, thereby providing a short description of the physics related to such methods and analyzing the relevant scientific literature. The theoretical basis of these methods is presented, and their advantages and disadvantages are discussed. Moreover, their applicability to the estimation of odor emissions is discussed by providing some suggestions about the suitable ways to evaluate the most critical parameters needed for the calculation of the odor emission rate.

Investigation of sources and atmospheric transformation of carbonaceous aerosols from Shyamnagar, eastern Indo-Gangetic Plains: Insights from δ13C and carbon fractions.

This study reports the chemical characterization of the carbonaceous component of PM2.5 (particulate matter with aerodynamic diameter ≤2.5 µm) collected over a year-long campaign from a regional site in Shyamnagar, West Bengal, in the Indo-Gangetic Plains (IGP), India. The carbonaceous fractions (elemental and organic carbon), mass concentrations, and stable carbon isotopic composition (δ13C value) of aerosols were measured and utilized to characterize the sources and understand the atmospheric processing of aerosols. Cluster analysis, Potential Source Contribution Function (PSCF) modeling, and fire count data were analyzed to decipher the pattern of air masses, source contributions, and extent of burning activities. The PM2.5 mass concentrations were significantly higher during winter (168.3 ± 56.3 µg m-3) and post-monsoon (109.8 ± 59.1 µg m-3) compared to the monsoon (29.8 ± 10.7 µg m-3) and pre-monsoon (55.1 ± 23.0 µg m-3). Organic carbon (OC), elemental carbon (EC), and total carbon (TC) concentrations were also several factors higher during winter and post-monsoon compared to monsoon and pre-monsoon. The winter and post-monsoon experienced the impact of air masses from upwind IGP. On the other hand, long-range transported air masses from the South-West direction dominated during monsoon and pre-monsoon, which are also relatively cleaner periods. The average δ13C during post-monsoon and winter was ∼1‰ higher compared to monsoon and pre-monsoon. The vehicular exhaust and biomass/biofuel burning contributed dominantly in winter and post-monsoon. In comparison, lower δ13C in pre-monsoon and monsoon might be attributed to the dominance of biomass/biofuel combustion. Photochemical-induced aging of the anthropogenic aerosols resulted in a higher δ13C of TC in winter and post-monsoon, whereas the mixing of different local sources in pre-monsoon and monsoon resulted in lower δ13C values. These findings benefit policymakers in strategizing proper and effective management of biomass/biofuel burning in the IGP to minimize air pollution.

Pesticides in the atmosphere and seawater in a transect study from the Western Pacific to the Southern Ocean: The importance of continental discharges and air-seawater exchange.

The global oceans are known as terminal sink or secondary source for diffusive emission of organochlorine pesticides (OCPs) and selected current used pesticides (CUPs) into the overlaying atmosphere. Many pesticides have been widely produced worldwide, subsequently applied, and released into the environment. However, information on the occurrence patterns, spatial variability, and air-seawater exchange of pesticides is limited to easily accessible regions and, hence, only few studies are reported from the remote Southern Ocean. To fill this information gap, a large-scale ship-based sampling campaign was conducted. In the samples from this campaign, we measured concentrations of 221 pesticides. Both gaseous and aqueous samples were collected along a sampling transect from the western Pacific to the Southern Ocean (19.75° N-76.16° S) from November 2018 to March 2019. Twenty-seven individual pesticides were frequently (≥ 50%) detected in gaseous and aqueous samples. Tebuconazole, diphenylamine, myclobutanil, and hexachlorobenzene (HCB) dominated the composition profile in both phases. Spatial trends analysis in atmospheric and seawater concentrations showed a substantial level reduction from the western Pacific towards the Southern Ocean. Back-trajectory analysis showed that atmospheric pesticide concentrations were strongly influenced by air masses origins. Continental and riverine inputs are important sources of pesticides in the western Pacific and Indian Oceans. Atmospheric and seawater concentrations for the target pesticide residues in the Southern Ocean are low and evenly distributed due to the large distance from potential pollution sources as well as the effective isolation by the Antarctic Convergence (AC). Air-seawater fugacity ratios and fluxes indicated that the western Pacific and Indian Oceans were secondary sources for most pesticides emitted to the atmosphere, while the Southern Ocean was still considered to be a sink.

Resolving mass fractions and congener group patterns of C8-C17 chlorinated paraffins in commercial products: Associations with source characterization.

Commercial chlorinated paraffins (CPs) are a source of CPs in the environment, and clarification of the different CP groups present in commercial products is important for source characterization. Resolving CP congener groups is hindered by the complex CP compositions of commercial products. We used comprehensive two-dimensional gas chromatography coupled with electron capture negative ionization high-resolution time-of-flight mass spectrometry to profile 57 C8 - C17 CP congener groups in 18 CP-42, CP-52, and CP-70 commercial products. Very short-chain CPs (vSCCPs), including C8Cl5-8 and C9Cl5-9 CPs, and other chlorinated aromatic compounds were identified in the commercial products. The mass fractions of total vSCCPs, short-chain CPs (SCCPs) and medium-chain CPs (MCCPs) in the commercial products ranged from 0.02% to 3.61%, 0.75% to 51.4%, and 0.39% to 69.1%, respectively. Two-dimensional hierarchical cluster analysis with a heat map plot highlighted variations in the C8 - C17 CP congener group patterns among different commercial CP formulations. The principal component analysis results indicated that commercial CPs products might be important contributors to vSCCPs, SCCPs, and MCCPs in various environmental matrices. This study provides comprehensive and well-resolved compositional data for CPs in commercial products, which will be helpful for CP source characterization.

Influence of photolysis on source characterization and health risk of polycyclic aromatic hydrocarbons (PAHs), and carbonyl-, nitro-, hydroxy- PAHs in urban road dust.

In this study, PAHs and their transformed PAH products (TPPs) in road dust were subjected to UV driven photolysis, and then extracted using simultaneous pressurized fluid extraction, and analysed using Shimadzu Triple Quadrupole GC/MS. The results of the analysis were used to investigate the robustness and reliability of 14 existing diagnostic ratios (DRs) and two newly proposed molecular DRs that are relevant for characterizing the sources of PAHs and TPPs. The influence of photolysis on the carcinogenic health risk posed to humans by these hazardous pollutants was then assessed. The findings indicated that the DRs segregated into stable, moderately stable and non-stable classes of source characteristics under the influence of photolysis. Only two of the existing DRs, namely, benzo(a)pyrene/benzo(ghi)perylene (BaP/BghiP) and total index exhibited consistent stability to photolysis, whilst fluoranthene/(fluoranthene + pyrene) (FRT/(FRT+PYR)) showed moderate stability. The two newly proposed DRs, naphthalene/1-nitronaphthalene (NAP/NNAP) and pyrene/(1-nitropyrene + 1-hydroxypyrene) (PYR/(1NPY+HPY)) were found to be highly reliable in post-emission source characterization. The cross-plots of the most stable DRs showed that traffic emissions is the primary source of PAHs, whilst post-emission photolysis is the secondary source of nitro-PAH (NPAH) TPPs. The percent resonance energy thermodynamic stability of the PAH pollutants does not exert any direct influence on the source characteristics of the DRs. Adults are more vulnerable to potential carcinogenic risks as a result of PAH and TPPs photolysis whereas negligible risk exist for children. This study contributes to a more reliable diagnosis of PAH and TPP sources and thus, to the regulatory mitigation of these hazardous pollutants thereby, promoting enhanced protection of human health and the environment.

Source Characterization of Multiple Reactive Species at an Abandoned Mine Site Using a Groundwater Numerical Simulation Model and Optimization Models.

The most important first step in the management and remediation of contaminated groundwater aquifers is unknown contaminant source characterization. Often, the hydrogeological field data available for accurate source characterization are very sparse. In addition, hydrogeological and geochemical parameter estimates and field measurements are uncertain. Particularly in complex contaminated sites such as abandoned mine sites, the geochemical processes are very complex and identifying the sources of contamination in terms of location, magnitude, and duration, and determination of the pathways of pollution become very difficult. The reactive nature of the contaminant species makes the geochemical transport process very difficult to model and predict. Additionally, the source identification inverse problem is often non-unique and ill posed. This study is about developing and demonstrating a source characterization methodology for a complex contaminated aquifer with multiple reactive species. This study presents linked simulation optimization-based methodologies for characterization of unknown groundwater pollution source characteristics, i.e., location, magnitude and duration or timing. Optimization models are solved using an adaptive simulated annealing (ASA) optimization algorithm. The performance of the developed methodology is evaluated for different complex scenarios of groundwater pollution such as distributed mine waste dumps with reactive chemical species. The method is also applied to a real-life contaminated aquifer to demonstrate the potential applicability and optimal characterization results. The illustrative example site is a mine site in Northern Australia that is no longer active.

Occurrence of N-Nitrosamines in the Pearl River delta of China: Characterization and evaluation of different sources.

N-nitrosamines in water have drawn significant concerns for the health of water consumers due to their carcinogenic properties. N-nitrosamines are formed during disinfection of wastewater as well as different industrial and agricultural processes. This study characterized the N-nitrosamines compositions in eleven different wastewaters in the Pearl River Delta (PRD) in Southeast China, and the spatial distributions and the abundances of N-nitrosamines in the Pearl River water were detected. The results indicated that five N-nitrosamines species, including N-nitrosodimethylamine (NDMA), N-nitrosodiethylamine (NDEA), N-nitrosopyrrolidine (NPYR), N-nitrosomorpholine (NMOR) and N-nitrosodibutylamine (NDBA) were found in the industrial wastewater samples in the PRD. Remarkably high concentrations of NDMA (up to 4000 ng/L) were found in the wastewaters from the textile printing and dyeing as well as the electroplating, whereas NDMA, NDEA and NMOR were detected in the domestic wastewaters at concentrations lower than 15 ng/L. Moreover, we found that certain treatment processes for the electroplating wastewater could form a significant amount of NDMA, NPYR and NMOR. Analyses of the Pearl River water samples showed occurrences of different N-nitrosamines species, including NDMA (5.7 ng/L), NDEA (1.7 ng/L), NPYR (2.2 ng/L), NMOR (2.2 ng/L) and NDBA (4.9 ng/L). The abundances of N-nitrosamines species varied spatially due to the inputs from the different sources. Thus, our study provides unique and valuable information for occurrences, abundances and source characteristics of N-nitrosamines in the PRD.

Radiological evaluation of the transuranic remaining contamination in Palomares (Spain): A historical review.

This paper shows the studies carried out in Palomares (Almería, Spain) following the ground dispersion of nuclear material as a result of the air crash accident that took place in 1966, in which four nuclear bombs were involved. As a consequence of the Palomares accident, plutonium (Pu) and uranium (U) were dispersed over an area of approximately 2.3 km2 due to the chemical explosion of two of them. The most relevant activities carried out by CIEMAT, along with other national and international institutions in the Palomares scenario are detailed. These activities, performed for over 50 years, focus mainly in the characterization of the contamination source, in the continuous environmental and personal radiological monitoring programs, in the construction of a detailed superficial and 3-D mapping distribution of the remaining contamination and in the evaluation of the bioavailability of the transuranics still remaining in the area.

Spatially explicit pollutant load-integrated in-stream E. coli concentration modeling in a mixed land-use catchment.

Pathogen contamination is a major cause of surface water impairment in the United States, and fecal bacteria levels are typically used to evaluate microbial loading in bodies of water. Environmental models are considered a useful tool for evaluating watershed management practices. In this study, we assessed E. coli contamination of the Upper Stroubles Creek, Virginia, USA using the Soil and Water Assessment Tool (SWAT) model. The study area has been declared an impaired body of water due to recent bacterial contamination. Bacterial source characterizations play a critical role in such modeling exercises and especially in the case of non-point sources. As the SWAT model involves bacteria load estimation at a Hydrological Response Unit (HRU) level, we use the Spatially Explicit Load Enrichment Calculation Tool (SELECT) for our E. coli load estimations. We also evaluate current approaches to the measurement of bacterial interactions of the sediment-water interface using SWAT and the frequent measurements of streambed E. coli concentrations. For the simulation of in-stream E. coli concentrations using estimates drawn from SELECT without (with) sediment bacteria resuspension-deposition, Nash-Sutcliffe Efficiency (NSE) values of -0.41 to 0.34 (-0.19 to 0.36) are found. Moreover, in-stream E. coli concentrations measured at flow duration intervals show that the model frequently overestimates mid-range flows while underestimating low-range flows even with model improvements. The use of high-resolution E. coli loads and the consideration of sediment bacteria resuspension-deposition processes, generated higher E. coli concentrations for forested areas compared to those of urban and pasture lands, suggesting the importance of using detailed bacteria load estimations and land use information when assessing E. coli distribution in the environment.

Reconciling discrepancies in the source characterization of VOCs between emission inventories and receptor modeling.

Emission inventory (EI) and receptor model (RM) are two of the three source apportionment (SA) methods recommended by Ministry of Environment of China and used widely to provide independent views on emission source identifications. How to interpret the mixed results they provide, however, were less studied. In this study, a cross-validation study was conducted in one of China's fast-developing and highly populated city cluster- the Pearl River Delta (PRD) region. By utilizing a highly resolved speciated regional EI and a region-wide gridded volatile organic compounds (VOCs) speciation measurement campaign, we elucidated underlying factors for discrepancies between EI and RM and proposed ways for their interpretations with the aim to achieve a scientifically plausible source identification. Results showed that numbers of species, temporal and spatial resolutions used for comparison, photochemical loss of reactive species, potential missing sources in EI and tracers used in RM were important factors contributed to the discrepancies. Ensuring the consensus of species used in EIs and RMs, utilizing a larger spatial coverage and longer time span, addressing the impacts of photochemical losses, and supplementing emissions from missing sources could help reconcile the discrepancies in VOC source characterizations acquired using both approaches. By leveraging the advantages and circumventing the disadvantages in both methods, the EI and RM could play synergistic roles to obtain robust SAs to improve air quality management practices.

One sensor acoustic emission localization in plates.

Acoustic emissions are elastic waves accompanying damage processes and are therefore used for monitoring the health state of structures. Most of the traditional acoustic emission techniques use a trilateration approach requiring at least three sensors on a 2D domain in order to localize sources of acoustic emission events. In this paper, we present a new approach which requires only a single sensor to identify and localize the source of acoustic emissions in a finite plate. The method proposed makes use of the time reversal principle and the dispersive nature of the flexural wave mode in a suitable frequency band. The signal shape of the transverse velocity response contains information about the propagated paths of the incoming elastic waves. This information is made accessible by a numerical time reversal simulation. The effect of dispersion is reversed and the original shape of the flexural wave is restored at the origin of the acoustic emission. The time reversal process is analyzed first for an infinite Mindlin plate, then by a 3D FEM simulation which in combination results in a novel acoustic emission localization process. The process is experimentally verified for different aluminum plates for artificially generated acoustic emissions (Hsu-Nielsen source). Good and reliable localization was achieved for a homogeneous quadratic aluminum plate with only one measurement.