dataesr/scientific-paragraphs-categorization huggingface dataset:
Data were systematically tested for spatial or temporal trends and for their relationship with external factors such as meteorological parameters. Whenever a parameter had a significant influence on the PAH contents, the flux calculation was improved by integrating this parameter into the calculation. Statistical investigations were made using R (ver3. 4. 4; R Core Team, 2016) software with the RStudio interface (v1. 1. 453). Except for the fluxes estimated from economic data, the calculations were carried out by multiplying the flux of the matrix considered (e. g. runoff) by randomly drawn PAH content values in the appropriate database. The estimation was made such that the number of draws was equal to the number of samples in the database and draws were made with replacements. Thus, each sample had the same probability of occurrence.
Flux Estimation Quality The mathematical uncertainties estimated as previously described failed to reflect the quality of the database used for the flux calculation. To express this quality, grades were attributed according to five parameters including the database size, the number of studies, the sampling date in comparison with 2014, the spatial and temporal representativeness of the samples and the quality of the parameters that were used in the estimations (e. g. runoff). Each parameter was rated from 0 to 4 (low to high quality). The global quality grade was estimated as the lowest rate for individual parameters. The fluxes based on a numeric model or economic data were awarded a quality grade of 0 because no actual measurement could back up the results. 3 Results.
Atmospheric Deposition To quantify the atmospheric fallout over the Paris conurbation, PAH contents were taken from four studies gathering 95 bulk deposition samples collected between 2002 and 2014  [6, [20] [21] [22]. The seasonality in the atmospheric fallout was instigated, and the concentrations of PAHs in the bulk deposition displayed significant monthly changes (Kruskal-Wallis test, p-value < 0. 05). The rise was related to household heating during winter leading to significantly higher PAH emissions. The annual deposition was consequently estimated as the sum over the cold and the warm periods of the rainwater volumes over 4-day periods multiplied by random concentration values drawn in the corresponding database. The 4-day period was chosen to ensure a drawn probability for each sample of approximately one out of the number of samples in the database (n ¼ 95).
Following this method, the atmospheric deposition totalled F12 ¼ 290 AE 70 kg year À1 (Σ15). This fallout flux (160 g km À2 year À1 ) was lower than previously reported values within the range 208-234 g km À2 year À1  [12, 23]  measured over urban areas across the Seine River basin from 1999 to 2002. These results suggest a decrease in the atmospheric deposition over the past few decades, in agreement with the overall reduction of about 44% in PAH emissions reported by the CITEPA between 2000 and 2014. Because the database gathered a large number of samples representative in time and space of the PAH atmospheric deposition in the Seine River basin, the flux estimation was awarded the quality grade of 4.
Runoff The PAH flux related to runoff on roads and roofs (F12e) was quantified considering the volume of runoff collected in the sewer system. To estimate this flux, the PAH concentrations were gathered from four studies depicting 31 samples collected in separate sewer systems of urban areas  [10, [24] [25] [26]. The samples covered an extended area across the Paris conurbation, providing a good spatial representativeness of the database. Moreover, they were in good agreement with previously reported values for similar urban or suburban areas  [27, 28]. However, the temporal representativeness was not as good. Indeed, samples were collected at various times over the year, but the relationship between PAH concentrations and the characteristics of the rain event considered (rainfall intensity or duration of the previous dry periods) could not be investigated.
Consequently, this flux was estimated as the sum over the year of 12-day periods of runoff volumes multiplied by PAH concentrations randomly drawn within the runoff database. The flux totalled F12e ¼ 300 AE 40 kg year À1 (Σ15). This result was in good agreement with fluxes reported for other French urban areas  [29]. However, the quality grade of this flux was reduced to 3 because of the lack of information on the temporal changes in the runoff contamination. In addition, the PAH flux during the street cleaning process (F12f) was quantified. According to the SIAAP, the amount of water used for street cleaning reached 59 Mm 3 year À1. A previous study showed that the PAH concentration in water samples ranged from 0. 1 to 2. 2 μg L À1 (Σ13)  [30]. This study used data from 21 samples collected at various places within the Paris city limits.
Although the spatial database was spatially representative, all samples were collected from May to June 2002, and neither temporal changes nor the influence of meteorological parameters could be investigated. Consequently, and although the order of magnitude of the contamination was supported by the concentrations reported in runoff samples, the quality rate was downgraded to 2. The flux estimated in this way was F12f ¼ 93 AE 3 kg year À1 (Σ16, naphthalene included), and it amounted to 32% of the atmospheric deposition and 29% of the PAH runoff from roads and roofs. However, the influence of meteorological parameters could not be tested, and a redundancy between F12e (street runoff) and F12f (street cleaning) cannot be excluded because both remobilise pollutants from roads.
Domestic and Industrial Wastewater The flux related to domestic wastewater (F22a) was quantified using 35 measurements either in domestic effluents or in combined sewers during dry weather periods  [30, 31]. Specific attention was paid to using only samples collected close to domestic sources to avoid dilution by infiltration waters. Using data from combined sewers provided a better spatial representativeness, especially within the city of Paris itself, where there were exclusively combined sewers. However, this might have led to a flux overestimation because part of the pollution within the combined sewer is due to the remobilisation of runoff contaminants deposited during wet weather. Consequently, the quality rate was downgraded to 2. The flux was estimated by summing the daily volume of domestic wastewater over the year multiplied by a concentration value randomly drawn within the database; this led to an averaged value of F22a ¼ 450 AE 50 kg year À1 (Σ15).
Discharges from the Sewer System During the past few years, the chemical quality of storm water in the Paris area has been extensively investigated, especially within the OPUR research programme  [10, 26]. The resulting database was described in "Runoff" above, leading to the same quality grade  (3). The volume of runoff water collected in the separate sewer system was 95 Mm 3 for 2014. Based on these data, the flux of PAHs directly discharged into the Seine River by storm water was F22c ¼ 120 AE 12 kg year À1 (Σ15). PAH input into the river system also occurred from combined sewers during storms or during sewer system dysfunction. In 2014, 20. 5 Mm 3 of combined sewer overflows (wet weather), and 18. 2 Mm 3 of untreated wastewater (dry weather) were discharged. To quantify the flux of PAHs related to these overflow events, concentrations of PAHs in samples collected in combined sewers were matched to the corresponding water volumes depending on the weather conditions.
The databases were constituted of 22 samples from three different studies  [24, 34, 35]  for dry weather conditions and 99 samples from five studies  [16, 24, 30, 36, 37]  for wet weather conditions. A total flux of F22d ¼ 50 AE 4 kg year À1 (Σ15) was estimated, nearly 80% being released during wet weather conditions. The database used to quantify this flux summarised data from various sites and was therefore spatially representative. However, the lack of information on intra-event variability in PAH concentrations resulted in a quality grade of 2. The last PAH flux related to the sewer system was the removal of highly contaminated sewer deposits during pipe cleaning. In 2014, 7,170 tons of sediment was removed from the sewer system. The contamination of sewer sediment has been documented in four studies  [31, [38] [39] [40]  and by the Paris Sanitation Department between 2000 and 2014.
The corresponding database gathered PAH measurements from 406 samples, thereby ensuring good spatial and temporal representativeness. Consequently, the flux estimation was awarded a quality grade of 4. The PAH flux related to sediment cleaning in the sewer system was F22i ¼ 160 AE 10 kg year À1 (Σ15). Since sewer sediment is not suitable for amending agricultural land, it was stored as hazardous material.
Wastewater Treatment Plants To quantify the total flux of PAHs entering WWTPs (F22e), the period investigated was divided between dry weather periods (208 days in 2014, average inflow, 2. 2 Mm 3 day À1 ) and wet weather periods (157 days, inflow, 2. 8 Mm 3 day À1 ). The PAH input was estimated as the daily collected water volumes from each sewer type multiplied by corresponding PAH concentrations measured in separate or combined sewers. For this estimation, care was taken to use data from samples collected at downstream parts of the sewer system. It was assumed that these samples were representative of the mix of waters originating from different sources including infiltration water. Consequently, entirely distinct databases were used to compute the F22a, E22h, F12e and F22e fluxes. The data of 121 samples from nine studies, including wastewater from the four main WWTPs, were used.
The annual load of PAHs was F22e ¼ 1,030 AE 50 kg year À1 (Σ15). The order of magnitude was also consistent with a previous study that reported an annual flux of about 476 kg year À1 for six compounds (FLH, BaP, BbF, BkF, BghiP and IcdP)  [36]. Consequently, this flux estimation was awarded a quality grade of 4. Once they have entered WWTPs, PAHs may be degraded during the treatment process, removed from the effluent through sorption onto sludge or discharged into the Seine River at the outlet of the WWTP. To quantify the amount of PAHs removed by the sludge removal process, the daily mass of sludge was multiplied by the random PAH contents measured in this matrix. The database comprised data from a previous study  [36]  or was provided by the SIAAP. It gathered data for 16 samples collected at three WWTPs treating 74% of the Paris conurbation population.
Atmospheric Deposition To quantify the PAH atmospheric deposition on rural areas, the investigated area was divided by discriminating between agricultural and forested land. Indeed, specific deposition processes over vegetated areas have been previously reported due to the forest filter effect  [19, 45, 46] , thereby justifying different approaches. To quantify the fallout flux over agricultural areas, a large database gathering 92 samples from two studies was available  [11, 47]. A significant difference was measured between the warm and cold periods (Wilcoxon-Mann-Whitney test, p < 0. 0001). This temporal variation was included in the flux estimation, as for F12. Thus, the atmospheric deposit over agricultural land reached F10 ¼ 5,680 AE 860 kg year À1 (Σ15). Because of the representative database, this estimation was awarded a grade of 3.
Road Runoff Outside of Urban Areas An additional runoff flux specific to the road network outside of urban areas was estimated. The surface concerned was estimated from the IGN database based on the road length and number of lanes provided. The road surface totalled 236 km 2 in the investigated area, and a runoff coefficient of 0. 9 was assumed. Since no data were available for rural road runoff, this volume was matched to the database of PAH concentrations in urban runoff water (n ¼ 31), and the flux totalled E14 ¼ 220 AE 30 kg year À1. This flux reached E14 # ¼ 310 AE 50 kg year À1 when considering runoff flux in urban areas ending up in permeable soils. However, this database was representative of a rural environment, and this quantification was awarded a grade of 0.
Indeed, previous studies reported specific traffic-related contamination within this range  [7, 56]. The stocks on both sides were quantified independently. Thus, 22% of agricultural land and 13% of forest area were situated within the critical distance to the road network. The PAH stocks in agricultural lands reached S10 ¼ 24 AE 17 Â 10 6 kg (n ¼ 61, Σ15), equally disseminated between the road vicinity and the more remote areas. High relative uncertainty due to the heterogeneity of the PAH content database for agricultural lands was observed. In forested areas, the PAH stock amounted to S11 ¼ 1. 0 AE 0. 3 Â 10 6 kg (n ¼ 26) with a smaller portion (12%) located close to roads. For urban and industrial areas, the PAH amount reached S12 ¼ 1. 8 AE 0. 6 Â 10 6 kg (n ¼ 45). Because further investigation on the relationship between the road traffic and the additional PAH stocks in the vicinity would be necessary to correctly quantify the pollutant amounts in the areas concerned, the stock estimation was awarded a grade of 2.
Soil Erosion The flux of PAH transferred from topsoils to the river was estimated by matching the land use map, the average PAH contents and erosion rates estimated across the area  [18]. Thus, the PAH erosion fluxes reached F15 ¼ 1,330 AE 1,010 kg year À1 (Σ15) for agricultural lands, F16 ¼ 34 AE 10 kg year À1 (Σ15) for forests and F17 + F18 ¼ 30 AE 9 kg year À1 (Σ15) for urban and industrial areas. Consequently, the overall erosion flux from soils was about 1,400 AE 1,030 kg year À1 (Σ15). As for the soil stock estimation, a high mathematical uncertainty due to the heterogeneity of the PAH content database for agricultural lands was observed. Moreover, this erosion flux was estimated from PAH content in soils instead of eroded particles because no other data were available. This method did not consider a potential enrichment process during erosion due to particle sorting.
Storage in Reservoirs and Floodplains To quantify the amount of PAHs (Fig. 4 ) annually stored in reservoirs (F23a), on river beds (F23b) and over floodplains (F24), the sedimentation rates were multiplied by the PAH content in suspended sediment (SS) randomly drawn in the database. As the floodplain and the reservoirs were located upstream of the Paris conurbation, the database was limited to SS samples collected in the uppermost parts of the Seine River basin. Finally, 104 samples from four studies were available  [9, 11, 59, 60]. The annual flux of PAHs from the rivers towards the reservoirs and the floodplains totalled F23a ¼ 120 AE 10 kg year À1 and F24 ¼ 140 AE 11 kg year À1 (Σ15), respectively. The entire database of PAH contents in sediment (n ¼ 183) was used to quantify the storage on river beds, although a greater weight was given to samples collected upstream of the Paris conurbation because 92% of the waterbody area was located upstream of the urban areas.
The estimated amount of PAHs stored on the river bed was F23b ¼ 640 AE 50 kg year À1 (Σ15). The flux estimations were marred by uncertainty due to the difficulty properly quantifying the amount of sediment being deposited every year. However, the deposition rates were consistent with the amount of material delivered to the Seine River through erosion and the SS flux at the study area outlet. Moreover, the database was complete enough to ensure the good spatial and temporal representativeness of the PAH contents in upstream SS. Therefore, the flux estimations were awarded a grade of 2. Quality grade in superscript from 0 (worst, in red) to 4 (best, deep blue). E5 and E6 domestic and industrial emissions, F10, F11a and F12 atmospheric deposit over agricultural, forested and urban lands, E11b forest filter effect, S stocks (kg) in soils, F13 spreading of urban sludge, E14 road runoff outside of urban areas, F15, F16, F17 and F18 erosion from agricultural, forested, urban and industrial lands, F22 releases from the sewer system and the WWTP to the Seine River, F23a and F23b storage in reservoirs and on the river bed, F24 flood deposits, F25 river dredging.
Flux Transported by the Seine River To investigate the PAH flux within the Seine River, calculations were based on concentrations measured independently in the particulate and the aqueous phases. The databases for the particulate and the dissolved fluxes of PAHs contained 15 samples from two studies  [9, 60]  and 11 samples from two studies  [8, 60]. The annual PAH flux was estimated by attributing random values of the PAHs drawn from the databases to the monthly aqueous and solid fluxes. Finally, the total PAH flux reached F21 ¼ 2,700 AE 550 kg year À1 (Σ15), the largest part (77%) of it being in the particulate phase. This result was consistent with a previous publication that reported an estimation of the PAH inputs to the Seine River mouth ranging from 2000 to 2,535 kg year À1 over the 2009-2013 period  [61].
Estimation of Urban Fluxes at the Basin Scale PAH atmospheric emissions (Fig. 4 ) were quantified based on source spatial inventory established by INERIS, as previously described. The emissions from domestic and industrial sources were estimated at approximately E5 # ¼ 122 tons year À1 and E6 # ¼ 220 kg year À1 , respectively. The atmospheric deposition over urban areas was estimated considering the whole urban surface (4,020 km 2 ) and by integrating complementary data collected at other urban areas  [11]  into the bulk deposition database (n ¼ 115). No significant change was measured in the concentrations between the four sampling sites (Kruskal-Wallis test, p ¼ 0. 27). The total fallout over urban areas totalled F12 # ¼ 680 AE 153 kg year À1 (Σ15). Scarce data were available to quantify other urban fluxes at the basin scale.
It was assumed that the wet weather supply of PAHs was directly related to sewer sediment remobilisation rather than runoff  [67]. When estimated at the WWTP scale, the fluxes related to sludge and effluents, respectively, amounted to 55% (Σ13) and 2% (Σ15) of the incoming flux, suggesting that approximately 43% of PAHs were degraded or volatilised during the treatment process. This proportion of PAHs in sludge was in agreement with previously published results  [68] , but the amount of PAHs released through effluent discharge was about 15 times lower. This result could be explained because the database was in part collected at the Seine-Centre WWTP characterised by high suspended matter removal efficiency, which may not be fully representative of the other WWTPs. The overall discharge of PAHs into the Seine River system, including both WWTP effluents and overflows from the sewer system (F22c + F22d + F22f + E22g) within the Paris conurbation, reached 410 AE 110 kg year À1.
Firstly, the PAH fluxes related to industrial discharge to the sewers and rivers were poorly known. Since neither the wastewater volume nor the PAH concentrations were quantified, considerable work would be required to overcome this issue despite the current deindustrialisation of the basin. Because various industries are reported be responsible for different effluent contaminations, a specific inventory would be necessary. Secondly, more data on the PAH concentrations in the WWTP effluents would be necessary to validate or improve the quantification of the flux discharged to the Seine River. This investigation would even be crucial at the Seine River basin scale because small-capacity WWTPs vary greatly in efficiency. A similar consideration can be made for most of the urban fluxes because various inconsistencies appeared in the mass balance at the Seine River basin scale due to the lack of representative databases for such an extended area.
Consequently, research is still required to precisely quantify the PAH flux in the urban parts of the basin other than the Paris conurbation. In particular, fluxes related to the sewer system and the WWTP are poorly known in less densely populated areas. This difficulty was highlighted by the road runoff estimation. To properly quantify this flux, one should investigate the relationship between the PAH concentrations in the runoff water, the runoff volume and the daily vehicle traffic. In addition, certain fluxes could not be estimated based on the compiled databases, especially the environmental degradation fluxes. However, according to our PAH budgets, only degradation within the atmosphere would be significant. Indeed, the long-term contaminations of the soils which constituted the main PAH reservoir suggest that no significant degradation occurs in this compartment.
e. their stream order  [8]. This structure of the Seine River's drainage network was obtained from the IGN database (CarTHAgE ® ) and from an elevation model (50 m, http:// professionnels. ign. fr/bdalti). According to the required resolution of the application, the Riverstrahler model runs on an ensemble of connected objects, either basins, grouping EBs according to an idealised scheme of confluence of tributaries with average characteristics by stream order, or branches, with a detailed and exhaustive representation of the morphology at 1 km spatial resolution. Reservoirs and ponds are also taken into account with a description of their morphology (depth and surface area) and hydrology (water inflow and outflow). Hydrological inputs are provided by the HYDRO database (http://www. hydro. eaufrance.
fr), averaged at a daily time step and separated into surface runoff and baseflow, using Eckhardt's recursive filter  [45]. Surface runoff and baseflow are generated using observed discharge time series at, e. g. 50-100 gauging stations for simulation periods ranging from 1 year  [23, 46]  to yearly contrasted hydrological conditions  [47, 48]  or plurennial time-windows  [22, 49, 50]. The Seine basin comprises about 1900 wastewater treatment plants, each being georeferenced and characterised by the connected population and the type of treatment applied  [51]. These data are provided by the Seine-Normandy database and are transformed into variables compatible with the model (nutrients and carbon under their specific forms  [37, 52, 53] ). Diffuse sources enter the river through surface runoff and the baseflow.
Mean annual nutrients and carbon concentrations are associated with each component of the water: N (nitrate, ammonium), P (total inorganic phosphorus, TIP), Si (dissolved and biogenic), suspended solids and organic and inorganic carbon. These concentrations differ according to major land use classes (cropland, permanent grassland, forests, urbanised areas) and lithological features, which are spatially determined using the Corine Land Cover database  [54]  and lithological information  [51]. For nitrate, two approaches are available. The GRAFS approach  [55, 56]  calculates leaching fluxes and concentrations  [57] , for both surface runoff and baseflow, for each land use class, on the basis of regional agricultural statistics at the département level. The other approach mobilises complex physically based models: the STICS agronomic model and the MODCOU hydrogeological model  [18, 58].
A maximum supersaturation of 10,000-12,000 ppm was reached downstream of Paris during the period of maximum organic pollution  (1985) (1986) (1987) (1988) (1989) (1990) (1991) (1992) (1993) (1994) (1995) (1996) (1997) (1998) (1999) (2000). BOD emitted from WWTPs indeed followed the exact same pattern as pCO 2  [34]  and therefore directly contributed to the CO 2 budget through direct outflows in the river system. Improvements of wastewater treatments in WWTPs therefore had a positive effect not only on water quality in terms of oxygenation, nutrients and eutrophication (see Fig. 5 ) but also on pCO 2 and hence on CO 2 emissions by the river network. To determine diffuse sources, values from the ADES database (www. ades. eaufrance. fr, last accessed on 2018/11/05) and our own pCO 2 measurements in piezometers were used.