Identifying remedial solutions through optimal bioremediation design under real-world field conditions.

Over more than a century of intense industrial production and associated accidental release, petroleum products (e.g., gasoline, diesel, fuel oil) have contaminated a significant portion of the world's groundwater resources. Groundwater remediation is generally a complex task, especially where aquifers and the associated contaminant distribution are highly heterogeneous. The ability to predict the efficiency of such remediation is of crucial importance, as the costs are strongly linked to the treatment design and duration. In this study, a coupled simulation-optimization (S/O) framework, consisting of a process-based reactive transport simulation model linked with particle swarm optimization (PSO) was developed. It was subsequently applied for the design of a real-world in situ bio-treatment of a BTEX contaminated aquifer in France. In the application, the optimization framework was used to simultaneously determine optimal well locations and their optimal injection rates, both constituting key elements of the enhanced biodegradation design problem. The optimization of the treatment efficiency was examined in terms of three different regulatory objectives, (1) minimization of the residual NAPL mass of the key contaminant, i.e., benzene, in the source zone, (2) reduction of the maximum concentration of benzene in groundwater, and (3) minimization of the time required to reduce the benzene concentration in groundwater to below a threshold value. Our analysis of potential, optimal remediation strategies showed that: (i) the complexity of the biodegradation behavior at real sites may favor very different remediation options as a result of varying remediation targets, (ii) the long term behavior of the contaminants after the end of the active treatment period, which is often neglected, showed to have a significant influence on remediation design that requires increased attention, (iii) PSO has shown to be a very efficient algorithm in the context of the present study. The insights that can be gained from such a framework will provide decision support to select the most suitable remediation strategy while facing different regulatory objectives.

An iterative strategy for contaminant source localisation using GLMA optimization and Data Worth on two synthetic 2D Aquifers.

A contaminant source localisation strategy was developed considering unknown heterogeneous hydraulic conductivity field, unknown dispersivity and unknown location of a continuous contaminant source. The Gauss-Levenberg-Marquardt algorithm is combined with a data worth analysis to estimate the unknown parameters and identify the best locations of additional measurements. The data collection strategy is iterative, based on the ability of the additional dataset to decrease the uncertainties on the contaminant source location. Two 2D synthetic models are considered. The method is first illustrated with a simple model and a more complex model is then considered to evaluate the ability of the approach to locate the contaminant source from hydraulic heads and concentration data. This approach is parsimonious in terms of model runs and applicable to real cases. The results give a good estimate of the source location and the dispersivity, with acceptable NRMSE for each case. New observations introduced at each iteration decrease the standard deviation of the source location and improve the NRMSE. The estimated hydraulic conductivity field presents the same features as the original field.

Elucidating the fate of a mixed toluene, DHM, methanol, and i-propanol plume during in situ bioremediation.

Organic pollutants such as solvents or petroleum products are widespread contaminants in soil and groundwater systems. In-situ bioremediation is a commonly used remediation technology to clean up the subsurface to eliminate the risks of toxic substances to reach potential receptors in surface waters or drinking water wells. This study discusses the development of a subsurface model to analyse the performance of an actively operating field-scale enhanced bioremediation scheme. The study site was affected by a mixed toluene, dihydromyrcenol (DHM), methanol, and i-propanol plume. A high-resolution, time-series of data was used to constrain the model development and calibration. The analysis shows that the observed failure of the treatment system is linked to an inefficient oxygen injection pattern. Moreover, the model simulations also suggest that additional contaminant spillages have occurred in 2012. Those additional spillages and their associated additional oxygen demand resulted in a significant increase in contaminant fluxes that remained untreated. The study emphasises the important role that reactive transport modelling can play in data analyses and for enhancing remediation efficiency.

Erdheim-Chester disease: clinical and radiological findings.

PURPOSE: The authors retrospectively reviewed six cases of histologically proven Erdheim-Chester disease (ECD) to evaluate organ involvement and clinical and radiological findings. MATERIALS AND METHODS: Through a search of the pathology databases of four Italian hospitals, we identified six men (mean age, 56 years) with a histological diagnosis of ECD. Histology was performed on retroperitoneal or pulmonary biopsy, depending on disease involvement on imaging. Patients underwent plain radiography of the lower limbs and chest, total-body computed tomography (CT) and bone scintigraphy. Magnetic resonance (MR) imaging was performed in two patients to evaluate the lower limbs and in one patient to study the brain, the chest and the abdomen. RESULTS: Clinical manifestations included dyspnoea (n=2), hydronephrosis (n=2) and bone pain (n=1). Bilateral symmetrical osteosclerosis of the metaphyseal and diaphyseal portions of the lower-limb long bones was present in five patients. Imaging studies revealed extraskeletal manifestations in all patients, including involvement of the retroperitoneal space (n=4), the lung (n=4) and the heart (n=2). CONCLUSIONS: ECD is a multiorgan disease that displays constant involvement of the bones and retroperitoneum; in particular, of the perirenal fat. Although the diagnosis of ECD is histological, imaging can raise suspicion and help to establish a presumptive diagnosis.

Advantages of multidetector-row CT with multiplanar reformation in guiding percutaneous lung biopsies.

PURPOSE: This study aimed to assess the usefulness of multiplanar reformations (MPR) during multidetector-row computed tomography (MDCT)-guided percutaneous needle biopsy of lung lesions difficult to access with the guidance of the native axial images alone owing to overlying bony structures, large vessels or pleural fissures. MATERIALS AND METHODS: MDCT-guided transthoracic needle biopsy (TNB) was performed on 84 patients (55 men and 29 women; mean age 65 years) with suspected lung neoplasm by using a spiral MDCT scanner with the simultaneous acquisition of six slices per rotation. We determined the site of entry of the 22-gauge Chiba needle on native axial images and coronal or sagittal MPR images. We took care to ensure the shortest needle path without overlying large vessels, main bronchi, pleural fissures or bony structures; access to the lung parenchyma as perpendicular as possible to the pleural plane; and sampling of highly attenuating areas of noncalcified tissue within the lesion. RESULTS: Diagnostic samples were obtained in 96% of cases. In 73 patients, lesions appeared as a solid noncalcified nodule <2 cm; 11 lesions were mass-like. In 22, the biopsy required MPR guidance owing to overlying ribs (18), fissures (2) or hilar-mediastinal location (2). CONCLUSIONS: MDCT MPR images allowed sampling of pulmonary lesions until now considered unreachable with axial MDCT guidance because of overlying bony structures (ribs, sternum and scapulae) or critical location (hilar-mediastinal, proximity to the heart or large vessels). Compared with the conventional procedure, the use of MPR images does not increase the rate of pneumothorax or the procedure time.

Uncommon causes of tracheobronchial stenosis and wall thickening: MDCT imaging.

Some uncommon diseases may involve the central airways focally or diffusely. These include Wegener's granulomatosis, relapsing polychondritis, tracheobronchopathia osteochondroplastica, amyloidosis, papillomatosis, rhinoscleroma, sarcoidosis and tuberculosis. Related computed tomography (CT) findings essentially include calcifications, luminal stenosis, wall thickening and nodules. The purpose of this paper is to help refine the differential diagnosis among these diseases through the use of multidetector CT (MDCT) imaging.

Negative ion electrospray ionization tandem mass spectrometry in the structural characterization of penicillins.

The mass spectrometry (MS) behaviour of ten commercially available penicillins has been studied by means of electrospray and multiple-stage MS/MS experiments performed using an ion trap instrument. For all the examined compounds negative ions are produced under ESI conditions, with a yield two or three orders of magnitude higher than that observed for positive ions. MSn experiments indicate the occurrence of a fragmentation pathway related to the beta-lactam ring, different from that usually described for positive ions of these compounds, and provide structural information on both the beta-lactam ring and the side chains.