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"Guzzella, L"
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Intensive monitoring of conventional and surrogate quality parameters in a highly urbanized river affected by multiple combined sewer overflows
The paper reports results of four intensive campaigns carried out on the Seveso River (Milan metropolitan area, Italy) between 2014 and 2016, during intense precipitation events. Laboratory analyses were coupled with on-site, continuous measurements to assess the impact of pollutants on water quality based on both conventional and surrogate parameters. Laboratory data included total suspended solids, caffeine, total phosphorus and nitrogen, and their dissolved forms. Screening of trace metals (Cr, Cu, Pb, Ni, Cd) and PBDEs (polybromodiphenylethers) was carried out. Continuous measurements included water level, physico-chemical variables and turbidity. Nutrient concentrations were generally high (e.g. average total phosphorus > 1,000 μg/L) indicating strong sewage contributions. Among monitored pollutants Cr, Cu, Pb, and Cd concentrations were well correlated to TSS, turbidity and discharge, being bound mostly to suspended particulate matter. A different behavior was found for Ni, that showed an early peak occurring before the flow peak, as a result of first flush events. PBDEs correlated well to nutrient concentrations, showing the highest peaks soon after activation of the combined sewer overflows, likely because of its accumulation in sewers. In addition to showing the existing correlations between quality parameters, the paper highlights the importance of surrogate parameters as indicators of anthropic pollution inputs.
Journal Article
Endogenous origin of foams in lakes: a long-term analysis for Lake Maggiore (northern Italy)
The formation of foams on lakes is a complex phenomenon whose origin is often hardly identifiable. Recently (2007, 2008, and 2010) foam episodes started to occur in Lake Maggiore, northern Italy. The present work aimed to verify the hypothesis of an endogenous-natural origin of these foams, driven by trophic or climatic changes. To this purpose, a long-term (2000–2013) analysis of phytoplankton biovolumes, meteorological, and hydrological data has been performed together with the chemical characterization of foams. Foams resulted of endogenous origin and likely related to phytoplankton biomass degradation. Data analysis highlighted atypical warm temperature and residual lake stratification in winter in two of the three years of foam events, coupled with exceptional Bacyllariophyceae blooms in spring. Tabellaria flocculosa mostly contributed in terms of biomass in 2007 and 2008, but not in 2010; thus overall algal biomass seemed a better predictor of the risk of foam formation. Foam events occurred from July to December, driven by atypically windy conditions, and congruently with the time needed to degrade biomass into surface-active compounds. A co-occurrence of different factors resulted essential to generate foams, and climate changes likely contribute to enhance their occurrence in Lake Maggiore.
Journal Article
Modelling and optimizing two- and four-stroke hybrid pneumatic engines
Abstract
Hybrid pneumatic engines, which are designed to follow the downsizing and supercharging paradigm, offer a fuel-saving potential that is almost equal to that of hybrid electric powertrains while inducing much lower additional mass and cost penalties. This paper presents a systematic optimization of the operation of such an engine system. Both two-stroke and four-stroke modes are analysed. The optimized valve and throttle actuation laws for all modes and operating areas lead to generic maps that are independent of the engine size. So far, the pneumatic hybridization of internal combustion engines was thought to require two-stroke operation. This paper presents a novel hybrid pneumatic engine configuration that entails fixed camshafts for both intake and exhaust valves while utilizing variable valve actuation for one charge valve per cylinder only. This configuration is operated entirely in four-stroke modes. Such a configuration requires a careful optimization of its operating strategy to achieve its fuel economy potential. Compared with a full two-stroke operation, only small efficiency losses result from using four-stroke modes with these new operating strategies. Initial measurement results with such an engine system are presented in this paper to confirm the validity of the principles of operation.
Journal Article
Model-based detection and isolation of faults due to ageing in the air and fuel paths of common-rail direct injection diesel engines equipped with a λ and a nitrogen oxides sensor
The air and fuel management of modern diesel engines is based on a feedforward control approach. As a consequence, faults of the air or the fuel path have a direct impact on the emissions that cannot be observed nor compensated. Faults due to the ageing of engine parts are very common; thus engines are designed with tolerances large enough to fulfil the emission standards for their entire lifetime.
This paper presents a method to locate and quantify engine faults due to the ageing of parts of modern diesel engines in order to help to reduce design tolerances. A relative air-to-fuel ratio and a nitrogen oxides emission sensor have been applied to a test-bench engine, and control-oriented emission models have been developed. Based thereon, a model-based fault detection and isolation system has been implemented. The sensor signals are compared with the models in order to detect a possible fault, and fault location and size are estimated by means of a bank of extended Kalman filters, one for each fault considered. Results from the New European Driving Cycle show that the developed control-oriented models are accurate, and the faults can be correctly detected and isolated.
Journal Article
Synthesis and characterization of a propazine imprinted polymer for the extraction of triazines herbicides
A MIP (molecularly imprinted polymer) was synthesized and evaluated for its use as sorbent for solid phase extraction (MISPE) of common used triazines (atrazine and terbuthylazine) and their widespread metabolites (desethyl-atrazine and desethyl-terbuthylazine) in water samples. MIP was produced by bulk polymerisation using methacrylic acid as functional monomer, ethylene glycol dimethacrylate as cross-linker, propazine as template and toluene as porogen solvent. Different washing methods of the synthesized polymer were evaluated. Soxhlet extraction provided the best results with a residual concentration of propazine, ranging from 0.78 to 2.86 μg for 1 g of polymer. Capacity factor was calculated using a 5 cm HPLC column filled with MIP and NIP (Not Imprinted Polymer): data extrapolation indicated a log Kw of 4.3 for MIP and a log Kw of 3.5 for NIP. Also frontal analyses confirmed a different behaviour of the two polymers. By comparing the recovery efficiency of MIP with that of traditional LiChrolut EN cartridge in the extraction of a River Po water sample, the results confirmed the reliability of this new technique for the analysis of herbicide compounds.
Journal Article
Studies on Mobility and Degradation Pathways of Terbuthylazine Using Lysimeters on a Field Scale
Terbuthylazine [N2‐tert‐butyl‐6‐chloro‐N4‐ethyl‐1,3,5‐triazine‐2,4‐diamine] degradation pathways in agricultural soils were evaluated by following the appearance and mobility of its main transformation products: dealkylated and hydroxylated derivatives. Three experimental degradation studies in open field were performed in different hydraulic conditions: constant hydraulic head on topsoil, achieved to simulate the highest‐risk situation for the aquifer; intermittent artificial precipitation to simulate a medium‐risk situation; and natural precipitation to reproduce the lowest‐risk condition. Concentrations of terbuthylazine transformation products derived from dealkylation and hydroxylation reactions were measured in leachates and soil samples collected during the three experiments. Desethylterbuthylazine (DET) and deethylterbuthylazine‐2‐hydroxide [DETH; 4‐amino‐6‐terbutylamino‐(1,3,5)‐triazine‐2‐OH] were found to be the highest‐leaching compounds and therefore can be considered as potential pollutants for aquifer contamination.
Journal Article
Fate of diuron and linuron in a field lysimeter experiment
The environmental fate of herbicides can be studied at different levels: in the lab with disturbed or undisturbed soil columns or in the field with suction cup lysimeters or soil enclosure lysimeters. A field lysimeter experiment with 10 soil enclosures was performed to evaluate the mass balance in different environmental compartments of the phenylurea herbicides diuron [3-(3,4-diclorophenyl)-1,1-dimethylurea] and linuron [3-(3,4-dichlorophenyl)-1-methoxy-1-methylurea]. After application on the agricultural soil, the herbicides were searched for in soil, pore water, and air samples. Soil and water samples were collected at different depths of the soil profile and analyzed to determine residual concentrations of both the parent compounds and of their main transformation products, to verify their persistence and their leaching capacity. Air volatilization was calculated using the theoretical profile shape method. The herbicides were detected only in the surface layer (0-10 cm) of soil. In this layer, diuron was reduced to 50% of its initial concentration at the end of the experiment, while linuron was still 70% present after 245 d. The main metabolites detected were DCPMU [3-(3,4-dichlorophenyl)-1-methylurea] and DCA (3,4-dichloroaniline). In soil pore water, diuron and linuron were detected at depths of 20 and 40 cm, although in very low concentrations. Therefore the leaching of these herbicides was quite low in this experiment. Moreover, volatilization losses were inconsequential. The calculated total mass balance showed a high persistence of linuron and diuron in the soil, a low mobility in soil pore water (less than 0.5% in leachate water), and a negligible volatilization effect. The application of the Pesticide Leaching Model (PELMO) showed similar low mobility of the chemicals in soil and water, but overestimated their volatilization and their degradation to the metabolite DCPMU. In conclusion, the use of soil enclosure lysimeters proved to be a good experimental design for studying mobility and transport processes of herbicides in field conditions.
Journal Article
A Framework For The Iterative Dynamic Optimisation Of Diesel Engines: Numerical Methods, Experimental Setup, And First Results
Owing to the many degrees of freedom provided by current engine systems and to the need to consider transient operation, deriving an engine calibration has become a tedious task. Control trajectories resulting fromthe solution of an optimal-control problem provide a guideline to the calibration engineer, serve as a benchmark, and might be used for a partial automation of the calibration procedure. The common approach to dynamic optimisation consists of solving a single optimal-control problem. However, this approach requires the availability of models that are valid throughout the whole engine operating range and actuator ranges. In addition, the result of the optimisation is meaningful only if the model is very accurate. We propose a methodology to circumvent those demanding requirements: an iteration between transient measurements to refine a purpose-built model and a dynamic optimisation which is constrained to the model-validity region. This paper presents all numerical methods required to implement this procedure. The crucial steps are analysed in detail, and the most important caveats are indicated. Finally, an experimental validation demonstrates the applicability of the method and reveals the components that require further development.
Journal Article
Modelling engine and exhaust temperatures of a mono-fuelled turbocharged compressed-natural-gas engine during warm-up
Abstract
A promising way to reduce the carbon dioxide emissions of vehicles is the use of engines fuelled only by compressed natural gas (CNG). However, even with CNG, restrictions on pollutants such as methane and non-methane hydrocarbons must be complied with. In a modern spark ignition (SI) engine, most of the pollutants are produced during the cold start before the catalytic converter reaches its light-off temperature. To avoid costly problems late in the development phase, it is reasonable to assess the functionality of the exhaust system as a whole, and the light-off behaviour of the catalytic converter in particular, as early as possible using simulation. Today's state-of-the-art catalytic converter simulation tools require the temperature signal upstream of the catalytic converter as input. This necessitates an easily applicable simulation tool of the exhaust temperature that takes the engine warm-up into account.
This paper presents a new physics-based model for the estimation of the engine and exhaust temperatures for a CNG-fuelled SI engine during warm-up. A new mean value model for the combustion wall heat transfer and also a lumped-parameter consideration of the cooling fluid are presented. In addition, existing methods for engine modelling are adapted to account for engine warm-up. Based on measurements performed on a special test bench assembly, the most important physical effects occurring in this phase are identified. Various experiments for parameterization and validation of the model are carried out. Tests for all relevant engine operating variations confirm a good correlation between the model and measurement results.
Journal Article