Physically-based urban stormwater quality modelling: An efficient approach for calibration and sensitivity analysis.

Physically-based urban stormwater quality modelling is helpful for increasing the understanding of spatial-temporal dynamics of urban pollution, and for designing innovative management technologies. However, because of the high computational cost, calibration and validation of physically-based models is still challenging. In this context, this study aims to develop a new meta-model based framework for efficient calibration and sensitivity analysis of complex and computationally intensive physically-based models. The proposed approach is applied to the FullSWOF-HR model. According to the average rainfall intensity, 21 rainfall events are categorized into three groups, such as 9 light rains, 6 moderate rains and 6 heavy rains. After upscaling the original high-resolution model, 77 parameter nodes are selected by using the adaptive stochastic collocation method with sparse grids algorithm on the lower-resolution surrogate. 77 simulation runs are then performed with the original model for three representative rainfall events, respectively. The interpolating polynomials of the original models are hence generated. Once the meta-model is constructed, we performed the sensitivity analysis with the variance-based Sobol's method, the results of which are consistent with our previous studies. Calibration process of the meta-model is based on the Markov chain Monte Carlo method. The optimized parameters are verified with the original model and then validated for different rainfall events. These promising results show that the proposed meta-model based approach can efficiently perform sensitivity analysis and parameter optimization for complex physical stormwater quality models, and hence will be very helpful for spreading the detailed water quantity and quality modelling for urban water management issues.

WWP2 ubiquitylates RNA polymerase II for DNA-PK-dependent transcription arrest and repair at DNA breaks.

DNA double-strand breaks (DSBs) at RNA polymerase II (RNAPII) transcribed genes lead to inhibition of transcription. The DNA-dependent protein kinase (DNA-PK) complex plays a pivotal role in transcription inhibition at DSBs by stimulating proteasome-dependent eviction of RNAPII at these lesions. How DNA-PK triggers RNAPII eviction to inhibit transcription at DSBs remains unclear. Here we show that the HECT E3 ubiquitin ligase WWP2 associates with components of the DNA-PK and RNAPII complexes and is recruited to DSBs at RNAPII transcribed genes. In response to DSBs, WWP2 targets the RNAPII subunit RPB1 for K48-linked ubiquitylation, thereby driving DNA-PK- and proteasome-dependent eviction of RNAPII. The lack of WWP2 or expression of nonubiquitylatable RPB1 abrogates the binding of nonhomologous end joining (NHEJ) factors, including DNA-PK and XRCC4/DNA ligase IV, and impairs DSB repair. These findings suggest that WWP2 operates in a DNA-PK-dependent shutoff circuitry for RNAPII clearance that promotes DSB repair by protecting the NHEJ machinery from collision with the transcription machinery.

Eyes wide shut: Exploring practices of negotiated ignorance in water resources modelling and management.

Formalised methods to address uncertainty are becoming the norm in hydrological modelling, yet they remain fragmented and highly academic, thus limiting their utility for practitioners. Using a qualitative, empirical study of the PIREN-Seine program in France, this paper explores the proccesses behind this trend in an effort to elucidate its prevalence despite inherent limitations when applied to a decision-making context. We identify: 1/ displacement of 'uncomfortable knowledge', 2/ fragmented responsibility, 3/ confidence, and 4/ relational framing as interconnected factors, which concurrently support the production of scientific knowledge and the social construction of ignorance, whether it be wilful or intentional. We posit that ignorance is implicitly negotiated among researchers and practitioners in order to reconcile cognitive dissonance and maintain confidence, thereby allowing water managers to take action in the face of uncertainty. Finally, we put forth the notion that having our 'eyes wide shut' can be interpreted in two ways: one facilitates the normalisation of ignorance, leaving us vulnerable to unexpected surprises; the other promotes transparent and explicit communication in support of more adaptive and robust decisions.

Contribution of atmospheric dry deposition to stormwater loads for PAHs and trace metals in a small and highly trafficked urban road catchment.

A deep understanding of pollutant buildup and wash-off is essential for accurate urban stormwater quality modeling and for the development of stormwater management practices, knowing the potential adverse impacts of runoff pollution on receiving waters. In the context of quantifying the contribution of airborne pollutants to the contamination of stormwater runoff and assessing the need of developing an integrated AIR-WATER modeling chain, loads of polycyclic aromatic hydrocarbons (PAHs) and metal trace elements (MTEs) are calculated in atmospheric dry deposits, stormwater runoff, and surface dust stock within a small yet highly trafficked urban road catchment (~ 30,000 vehicles per day) near Paris. Despite the important traffic load and according to the current definition of "atmospheric" source, atmospheric deposition did not account for more than 10% of the PAHs and trace metal loads in stormwater samples for the majority of the events, based on the ratio of deposition to stormwater. This result shows that atmospheric deposition is not a major source of pollutants in stormwater, and thus, linking the air and water compartment in a modeling chain to have more accurate estimates of pollutant loads in stormwater runoff might not be relevant. Comparison of road dust with water samples demonstrates that only the fine fraction of the available stock is eroded during a rainfall event. Even if the atmosphere mostly generates fine particles, the existence of other sources of fine particles to stormwater runoff is highlighted.

Investigation of the wash-off process using an innovative portable rainfall simulator allowing continuous monitoring of flow and turbidity at the urban surface outlet.

Development of appropriate models, based on an in-depth understanding of the wash-off process, is essential to accurately estimating pollutant loads transported by stormwater, thereby minimizing environmental contamination. To this end, we developed an innovative rainfall simulator, which simulated an intense rainfall (120mm/h) and permitted the acquisition of runoff samples as well as the in situ monitoring of continuous flow and turbidity dynamics. Relationships between deposited sediments and total suspended solids in simulated runoff were thus investigated on two different types of surfaces within the Paris region in terms of loads and particle size distribution. Results demonstrate the occurrence of first flush phenomenon on the sidewalks even under constant flow. Results also show that the highest fraction conveyed by runoff consisted of fine (<16µm) and medium-sized (<100µm) particles, whose detachment was more favorable from smooth surfaces than from rougher ones. In terms of stormwater quality modelling, results suggest that the integration of a wash-off fraction based on both particle size and rainfall intensity could be an entrance for a better prediction of stormwater pollution.

Should we trust build-up/wash-off water quality models at the scale of urban catchments?

Models of runoff water quality at the scale of an urban catchment usually rely on build-up/wash-off formulations obtained through small-scale experiments. Often, the physical interpretation of the model parameters, valid at the small-scale, is transposed to large-scale applications. Testing different levels of spatial variability, the parameter distributions of a water quality model are obtained in this paper through a Monte Carlo Markov Chain algorithm and analyzed. The simulated variable is the total suspended solid concentration at the outlet of a periurban catchment in the Paris region (2.3 km2), for which high-frequency turbidity measurements are available. This application suggests that build-up/wash-off models applied at the catchment-scale do not maintain their physical meaning, but should be considered as "black-box" models.

New insights into the urban washoff process with detailed physical modelling.

Current urban washoff models still rely on empirical catchment-scale functions, that have not been substantially updated during the last 40years. This paper introduce a new approach using the physical model FullSWOF to evaluate urban washoff process. The modelling approach is performed for a Parisian road catchment. Water flow simulation is validated by outlet discharge measurements and local observations of water depth. Water quality modelling of three classes of particles (d50=7µm, 70µm, and 250µm) is applied using the Hairsine-Rose model. Analysis of the washoff process at the catchment scale indicates that most (>90%) of the finest particles are removed at the beginning of a rainfall event, about 10%-20% of medium-sized particles are moved over the latest part of the event, and almost no coarse particles can be transferred into the sewer inlet. Spatial analysis of washoff process reveals that the concentration of suspended solids on road and sidewalk surface is more sensitive to rainfall intensities than that on gutter surface, while coarser particles tend to accumulate in the gutter over the later part of a rainfall event. Investigation of the driving force behind the detachment process indicates that rainfall-driven effects are two orders of magnitude higher than flow-driven effects. Moreover, it is observed that rainfall-driven detachment is considerably decreased with the rising water depth, while flow-driven detachment occurs only in gutter areas. Finally, several controversial arguments on the use of physical models for assessing the washoff process, and perspectives on development of physical urban washoff models are discussed.

A new approach of monitoring and physically-based modelling to investigate urban wash-off process on a road catchment near Paris.

Nowadays, the increasing use of vehicles is causing contaminated stormwater runoff to drain from roads. The detailed understanding of urban wash-off processes is essential for addressing urban management issues. However, existing modelling approaches are rarely applied for these objectives due to the lack of realistic input data, unsuitability of physical descriptions, and inadequate documentation of model testing. In this context, we implement a method of coupling monitoring surveys with the physically-based FullSWOF (Full Shallow Water equations for Overland Flow) model (Delestre et al., 2014) and the process-based H-R (Hairsine-Rose) model (Hairsine and Rose, 1992a, 1992b) to evaluate urban wash-off process on a road catchment near Paris (Le Perreux sur Marne, Val de Marne, France, 2661 m(2)). This work is the first time that such an approach is applied for road wash-off modelling in the context of urban stormwater runoff. On-site experimental measurements have shown that only the finest particles of the road dry stocks could be transferred to the sewer inlet during rainfall events, and most Polycyclic Aromatic Hydrocarbons (PAHs) are found in the particulate phase. Simulations over different rainfall events represent promising results in reproducing the various dynamics of water flows and sediment transports at the road catchment scale. Elementary Effects method is applied for sensitivity analysis. It is confirmed that settling velocity (Vs) and initial dry stocks (S) are the most influential parameters in both overall and higher order effects. Furthermore, flow-driven detachment seems to be insignificant in our case study, while raindrop-driven detachment is shown to be the major force for detaching sediment from the studied urban surface. Finally, a multiple sediment classification regarding the Particle Size Distribution (PSD) can be suggested for improving the model performance for future studies.

Neutral community model explains the bacterial community assembly in freshwater lakes.

Over the past decade, neutral theory has gained attention and recognition for its capacity to explain bacterial community structure (BCS) in addition to deterministic processes. However, no clear consensus has been drawn so far on their relative importance. In a metacommunity analysis, we explored at the regional and local scale the effects of these processes on the bacterial community assembly within the water column of 49 freshwater lakes. The BCS was assessed using terminal restriction fragment length polymorphism (T-RFLP) of the 16S rRNA genes. At the regional scales, results indicated that the neutral community model well predicted the spatial community structure (R(2) mean = 76%) compared with the deterministic factors - which explained only a small fraction of the BCS total variance (less than 14%). This suggests that the bacterial compartment was notably driven by stochastic processes, through loss and gain of taxa. At the local scale, the bacterial community appeared to be spatially structured by stochastic processes (R(2) mean = 65%) and temporally governed by the water temperature, a deterministic factor, even if some bacterial taxa were driven by neutral dynamics. Therefore, at both regional and local scales the neutral community model appeared to be relevant in explaining the bacterial assemblage structure.

Performance assessment of a commonly used "accumulation and wash-off" model from long-term continuous road runoff turbidity measurements.

The suitability of a commonly used accumulation and wash-off model for continuous modelling of urban runoff contamination was evaluated based on 11-month turbidity and flow-rate records from an urban street. Calibration and uncertainty analysis were performed using a Markov Chain Monte-Carlo sampling method for both suspended solids loads (discharge rates) and concentration modelling. Selected models failed at replicating suspended solids concentration over the complete monitoring period. The studied dataset indeed suggests that the accumulation process is rather unpredictable and cannot be satisfactorily represented with usual accumulation models unless short periods are considered. Regarding suspended solid loads modelling, noticeably better performance was achieved, but similar results could as well be obtained with much simpler constant concentration models. Unless providing very accurate estimates of concentrations in runoff, accounting for their temporal variability during rain events may therefore not always be necessary for pollutant loads modelling, as loads are in fact mostly explained by runoff volumes.

Modelling the fate of nonylphenolic compounds in the Seine River--part 2: assessing the impact of global change on daily concentrations.

This study aims at modelling the daily concentrations of nonylphenolic compounds such as 4-nonylphenol (4-NP), nonylphenol monoethoxylate (NP1EO) and nonylphenoxy acetic acid (NP1EC) within the Seine River downstream of Paris City for over a year, firstly in the present state (year 2010) and for years 2050 and 2100 in order to assess the consequences of global change on the fate of nonylphenolic compounds in the Seine river. Concentrations were first simulated for the year 2010 and compared to monthly measured values downstream of Paris. To achieve this goal, the hydrodynamic and biogeochemical model, ProSe, was updated to simulate the fate of 4-NP, NP1EO and NP1EC. The Seine upstream and Oise River (tributaries of the Seine River) concentrations are estimated according to concentrations-flow relationships. For Seine Aval wastewater treatment plant (SA-WWTP), the concentrations are considered constant and the median values of 11 campaigns are used. The biodegradation kinetics of 4-NP, NP1EO and NP1EC in the Seine River were deduced from the results of the companion paper. The Nash-Sutcliffe coefficient indicates a good efficiency to simulate the concentrations of 4-NP, NP1EC and NP1EO over an entire year. Eight scenarios were built to forecast the impacts of global warming (flow decrease), population growth (SA-WWTP flow increase) and optimisation of wastewater treatment (improvement of the quality of effluents) on annual concentrations of 4-NP, NP1EO and NP1EC at Meulan by 2050 and 2100. As a result, global warming and population growth may increase the concentrations of 4-NP, NP1EC and NP1EO, especially during low-flow conditions, while the optimisation of wastewater treatment is an efficient solution to balance the global change by reducing WWTP outflows.

Modelling the fate of nonylphenolic compounds in the Seine River--part 1: determination of in-situ attenuation rate constants.

Assessing the fate of endocrine disrupting compounds (EDCs) in the environment is currently a key issue for determining their impacts on aquatic ecosystems. The 4-nonylphenol (4-NP) is a well known EDC and results from the biodegradation of surfactant nonylphenol ethoxylates (NPnEOs). Fate mechanisms of NPnEO are well documented but their rate constants have been mainly determined through laboratory experiments. This study aims at evaluating the in-situ fate of 4-NP, nonylphenol monoethoxylate (NP1EO) and nonylphenolic acetic acid (NP1EC). Two sampling campaigns were carried out on the Seine River in July and September 2011, along a 28km-transect downstream Paris City. The field measurements are used for the calibration of a sub-model of NPnEO fate, included into a hydro-ecological model of the Seine River (ProSe). The timing of the sampling is based on the Seine River velocity in order to follow a volume of water. Based on our results, in-situ attenuation rate constants of 4-NP, NP1EO and NP1EC for both campaigns are evaluated. These rate constants vary greatly. Although the attenuation rate constants in July are especially high (higher than 1d(-1)), those obtained in September are lower and consistent with the literature. This is probably due to the biogeochemical conditions in the Seine River. Indeed, the July sampling campaign took place at the end of an algal bloom leading to an unusual bacterial biomass while the September campaign was carried out during common biogeochemical status. Finally, the uncertainties on measurements and on the calibration parameters are estimated through a sensitivity analysis. This study provides relevant information regarding the fate of biodegradable pollutants in an aquatic environment by coupling field measurements and a biogeochemical model. Such data may be very helpful in the future to better understand the fate of nonylphenolic compounds or any other pollutants at the basin scale.

Road traffic impact on urban water quality: a step towards integrated traffic, air and stormwater modelling.

Methods for simulating air pollution due to road traffic and the associated effects on stormwater runoff quality in an urban environment are examined with particular emphasis on the integration of the various simulation models into a consistent modelling chain. To that end, the models for traffic, pollutant emissions, atmospheric dispersion and deposition, and stormwater contamination are reviewed. The present study focuses on the implementation of a modelling chain for an actual urban case study, which is the contamination of water runoff by cadmium (Cd), lead (Pb), and zinc (Zn) in the Grigny urban catchment near Paris, France. First, traffic emissions are calculated with traffic inputs using the COPERT4 methodology. Next, the atmospheric dispersion of pollutants is simulated with the Polyphemus line source model and pollutant deposition fluxes in different subcatchment areas are calculated. Finally, the SWMM water quantity and quality model is used to estimate the concentrations of pollutants in stormwater runoff. The simulation results are compared to mass flow rates and concentrations of Cd, Pb and Zn measured at the catchment outlet. The contribution of local traffic to stormwater contamination is estimated to be significant for Pb and, to a lesser extent, for Zn and Cd; however, Pb is most likely overestimated due to outdated emissions factors. The results demonstrate the importance of treating distributed traffic emissions from major roadways explicitly since the impact of these sources on concentrations in the catchment outlet is underestimated when those traffic emissions are spatially averaged over the catchment area.

Alkylphenolic compounds and bisphenol A contamination within a heavily urbanized area: case study of Paris.

This study evaluates the influence of a heavily urbanized area (Paris Metropolitan area), on receiving water contamination by both bisphenol A (BPA) and alkylphenol ethoxylate (APE) biodegradation product. The study began by investigating concentrations within urban sources. In addition to the more commonly studied wastewater treatment plant effluent, wet weather urban sources (including combined sewer overflows, urban runoff, and total atmospheric fallout) were considered. The initial results highlight a significant contamination of all urban sources (from a few nanograms per liter in atmospheric fallout to several micrograms per liter in the other sources) with clearly distinguishable distribution patterns. Secondly, concentration changes along the Seine River from upstream of the Paris Metropolitan area to downstream were investigated. While the concentrations of BPA and nonylphenoxy acetic acid (NP1EC) increase substantially due to urban sources, the 4-nonylphenol concentrations remain homogeneous along the Seine. These results suggest a broad dissemination of 4-nonylphenol at the scale of the Seine River basin. Moreover, the relationship between pollutant concentrations and Seine River flow was assessed both upstream and downstream of the Paris conurbation. Consequently, a sharp decrease in dissolved NP1EC concentrations relative to Seine River flow underscores the influence of single-point urban pollution on Seine River contamination. Conversely, dissolved 4-nonylphenol concentrations serve to reinforce the hypothesis of its widespread presence at the Seine River basin scale.

DNAPKcs-dependent arrest of RNA polymerase II transcription in the presence of DNA breaks.

DNA double-strand break (DSB) repair interferes with ongoing cellular processes, including replication and transcription. Although the process of replication stalling upon collision of replication forks with damaged DNA has been extensively studied, the fate of elongating RNA polymerase II (RNAPII) that encounters a DSB is not well understood. We show that the occurrence of a single DSB at a human RNAPII-transcribed gene leads to inhibition of transcription elongation and reinitiation. Upon inhibition of DNA protein kinase (DNAPK), RNAPII bypasses the break and continues transcription elongation, suggesting that it is not the break per se that inhibits the processivity of RNAPII, but the activity of DNAPK. We also show that the mechanism of DNAPK-mediated transcription inhibition involves the proteasome-dependent pathway. The results point to the pivotal role of DNAPK activity in the eviction of RNAPII from DNA upon encountering a DNA lesion.

Repeated administration of piribedil induces less dyskinesia than L-dopa in MPTP-treated common marmosets: a behavioural and biochemical investigation.

Piribedil ([1-(3,4-methylenedioxybenzyl)-4-(2-pyrimidinyl)piperazine]; S 4200) is a dopamine agonist with equal affinity for D(2)/D(3) dopamine receptors effective in treating Parkinson's disease as monotherapy or as an adjunct to levodopa (L-dopa). However, its ability to prime basal ganglia for the appearance of dyskinesia is unknown. We now report on the ability of repeated administration of piribedil to induce dyskinesia in drug naïve 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) -lesioned common marmosets compared with L-dopa and its actions on the direct and indirect striatal outflow pathways. Administration of piribedil (4.0-5.0 mg/kg orally) or L-dopa (12.5 mg/kg orally plus carbidopa 12.5 mg/kg orally twice daily) produced equivalent increases in locomotor activity and reversal of motor deficits over a 28-day study period. Administration of L-dopa resulted in the progressive development of marked dyskinesia over the period of study. In contrast, administration of piribedil produced a significantly lower degree and intensity of dyskinesia. Surprisingly, piribedil caused an increase in vigilance and alertness compared to L-dopa, which may relate to the recently discovered alpha(2)-noradrenergic antagonist properties of piribedil. The behavioural differences between piribedil and L-dopa are reflected in the biochemical changes associated with the direct striatal output pathway. Administration of L-dopa or piribedil did not reverse the MPTP-induced up-regulation of preproenkephalin A mRNA in rostral or caudal areas of the putamen or caudate nucleus. In contrast, administration of either piribedil or L-dopa reversed the downregulation of preprotachykinin mRNA induced by MPTP in rostral and caudal striatum. L-dopa, but not Piribedil, reversed the decrease in preproenkephalin B mRNA produced by MPTP treatment.