Chemical and C and N stable isotope compositions of three species of epiphytic Tillandsia in a Caribbean coastal zone: air pollution sources and biomonitoring implications.

We characterized the elemental and C and N stable isotope compositions of Tillandsia fasciculata Sw., Tillandsia balbisiana Schult. & Schult.f. and Tillandsia recurvata (L.) L. samples collected in Cienfuegos (Cuba). Results showed high enrichment factors for S, Hg, Cd, Pb, P, Zn, Cu, Mo, Sb and Ca in all Tillandsia species, indicating inputs from local anthropogenic activities (road traffic, industries and cement production). Carbon concentrations and δ13C varied from 38.3-47.7 % and -20.4 to -13.4 ‰ within the three species, respectively. δ13C showed seasonal dependence with the dry and wet periods and more 13C-depleted values in urban/industrial areas, coherent with the input of anthropogenic emissions. Nitrogen concentrations (0.4-1.3 %) and δ15N values (-9.9-4.4 ‰) exhibit larger variations and are positively correlated in the three species. The most positive δ15N in T. recurvata (-0.2-4.4 ‰) are attributed to contributions from industrial activities and road traffic. In fact, both δ15N and total nitrogen (TN) values increase in sites with higher road traffic and show significant correlations with typical road traffic and industrial tracers. Finally, we calculate an average total nitrogen deposition rate of 4.4 ± 2.3 kg ha-1 a-1 from N content in T. recurvata, similar to the existing values determined in the region by field measurements, but higher than the global terrestrial average.

Attributing Atmospheric Phosphorus in the Himalayas: Biomass Burning vs Mineral Dust.

Atmospheric phosphorus is a vital nutrient for ecosystems whose sources and fate are still debated in the fragile Himalayan region, hindering our comprehension of its local ecological impact. This study provides novel insights into atmospheric phosphorus based on the study of total suspended particulate matter at the Qomolangma station. Contrary to the prevailing assumptions, we show that biomass burning (BB), not mineral dust, dominates total dissolved phosphorus (TDP, bioavailable) deposition in this arid region, especially during spring. While total phosphorus is mainly derived from dust (77% annually), TDP is largely affected by the transport of regional biomass-burning plumes from South Asia. During BB pollution episodes, TDP causing springtime TDP fluxes alone accounts for 43% of the annual budget. This suggests that BB outweighs dust in supplying bioavailable phosphorus, a critical nutrient, required to sustain Himalayas' ecological functions. Overall, this first-hand field evidence refines the regional and global phosphorus budget by demonstrating that BB emission, while still unrecognized, is a significant source of P, even in the remote mountains of the Himalayas. It also reveals the heterogeneity of atmospheric phosphorus deposition in that region, which will help predict changes in the impacted ecosystems as the deposition patterns vary.

Characterizing wine terroir using strontium isotope ratios: a review.

This paper presents a detailed review of the use of 87Sr/86Sr isotope systematics for wine provenance studies. The method is based on the principle that the Sr isotope ratio in wine reflects that of the labile fraction of the vineyard soil from which the wine is produced. The review encompasses 87Sr/86Sr data from wine samples published between 1993 and 2021 from terroirs in 22 different countries. The analytical procedures and techniques adopted by the different authors and the range of isotope ratios obtained in the different studies are discussed and evaluated. This study provides a bibliometric analysis of the 87Sr/86Sr isotope approach for wine authentication at different scales. Although limitations are evident when implemented at large (global) scales, we demonstrate that the 87Sr/86Sr isotope tracing technique remains a powerful and reliable tool for determining the geographical origin of wine when combined with detailed knowledge of the geological and soil characteristics of the substrata. For example, this combination of data allows the wines grown in the volcanic soils of Central and Southern Italy to be unambiguously fingerprinted. We present a detailed protocol for the application of the Sr isotope technique to wine authentication.

Wildfire-Derived Nitrogen Aerosols Threaten the Fragile Ecosystem in Himalayas and Tibetan Plateau.

Himalayas and Tibetan Plateau (HTP) is important for global biodiversity and regional sustainable development. While numerous studies have revealed that the ecosystem in this unique and pristine region is changing, their exact causes are still poorly understood. Here, we present a year-round (23 March 2017 to 19 March 2018) ground- and satellite-based atmospheric observation at the Qomolangma monitoring station (QOMS, 4276 m a.s.l.). Based on a comprehensive chemical and stable isotope (15N) analysis of nitrogen compounds and satellite observations, we provide unequivocal evidence that wildfire emissions in South Asia can come across the Himalayas and threaten the HTP's ecosystem. Such wildfire episodes, mostly occurring in spring (March-April), not only substantially enhanced the aerosol nitrogen concentration but also altered its composition (i.e., rendering it more bioavailable). We estimated a nitrogen deposition flux at QOMS of ∼10 kg N ha-1 yr-1, which is approximately twice the lower value of the critical load range reported for the Alpine ecosystem. Such adverse impact is particularly concerning, given the anticipated increase of wildfire activities in the future under climate change.

The multi-isotope biogeochemistry (S, C, N and Pb) of Hypogymnia physodes lichens: air quality approach in the Swietokrzyski National Park, Poland.

The isotope biogeochemistry of bioindicators has widely demonstrated its added value in environmental issues by allowing to precisely identify sources of contamination. Most of the studies are based on studying one or two isotope systematics. Here, we are presenting an innovative multi-proxy approach that combines chemistry with both stable (C, S, N) and radiogenic (Pb) isotope systematics. Using Hypogymnia physodes bioindicators, we evaluated air quality in the complex environment of the Swietokrzyski National Park (SNP, Poland) with the ultimate objective of isotopically identifying the sources responsible for the observed contamination. Combining the isotope systematics showed that home heating is a major source of contamination in winter, whereas the contribution of road traffic increases during the summer. Pb isotope ratios identified industrial activities as the major source of this metal in the atmosphere.

The carbon stable isotope compositions of glyphosate and aminomethylphosphonic acid (AMPA): Improved analytical sensitivity and first application to environmental water matrices.

RATIONALE: The presence of glyphosate and its degradation product aminomethylphosphonic acid (AMPA) in the environment has adverse effects on environmental quality, raising the need to better constrain their fates, in particular the processes that control their production and degradation. Our aim was to improve the sensitivity of their δ13 C analysis and demonstrate the feasibility of measuring them in natural surface water. METHODS: The δ13 C values of dissolved glyphosate and AMPA were determined using isotope ratio mass spectrometry (IRMS) (Delta V Plus instrument) coupled to a high-performance liquid chromatography (HPLC) unit, where glyphosate and AMPA were separated on a Hypercarb column. RESULTS: We demonstrated an improved sensitivity of the δ13 C analysis for glyphosate and AMPA by LC/IRMS compared with previous studies. For waters from the carbonate and silicate hydrofacies, while no pretreatment was required for the isotope analysis of glyphosate, removal by H3 PO4 acidification of dissolved inorganic carbon, that co-elutes with AMPA, was required prior to its analysis. We successfully tested a freeze-drying pre-concentration method showing no associated isotope fractionation up to concentration factors of 500 and 50 for glyphosate and AMPA, respectively. CONCLUSIONS: We demonstrated, for the first time, the feasibility of measuring the δ13 C values of glyphosate and AMPA in natural surface waters with contrasted hydrofacies (calcium carbonate and silicate types). This opens new fields in pesticide research, especially on the characterization of processes that control their degradation and the production of their secondary byproducts.

Respective contribution of urban wastewater and mangroves on nutrient dynamics in a tropical estuary during the monsoon season.

Estuaries of Southeast Asia are increasingly impacted by land-cover changes and pollution. Here, our research objectives were to (1) determine the origins of nutrient loads along the Can Gio estuary (Vietnam) and (2) identify the processes that affect the nutrient pools during the monsoon. We constructed four 24-h time-series along the salinity gradient measuring nutrient concentrations and stable isotopes values. In the upper estuary, urban effluents from Ho Chi Minh City were the main input of nutrients, leading to dissolved oxygen saturation <20%. In the lower estuary, ammonium and nitrite concentration peaks were explained by mangrove export. No contribution from aquaculture was detected, as it represents <0.01% of the total river discharge. Along the salinity gradient, nutrient inputs were rapidly consumed, potentially by phytoplankton while nitrate dual-stable isotopes indicated that nitrification occurred. Thus, even in a large and productive estuary, urban wastewater can affect nutrient dynamics with potentially important ecological risks.

Historical smelting activities in Eastern Canada revealed by Pb concentrations and isotope ratios in tree rings of long-lived white cedars (Thuja occidentalis L.).

Mining activities at Duparquet in Western Quebec (Canada) have significantly affected the local environment and left behind significant amounts of metals. Monitoring this contamination is essential to infer its past and present impacts on environmental quality and to evaluate the resulting human exposure. In that context, we measured long time series of Pb concentrations and their corresponding stable isotope ratios in long-lived white cedars (Thuja occidentalis L.) growing at Duparquet Lake in order to evaluate potential time variations of the Pb environmental contamination as well as to identify the responsible source(s). Results show that before 1950, Pb at Duparquet is mostly terrigenous. Lead concentrations rapidly increase afterwards. A simultaneous shift to lower 206Pb/207Pb ratios identifies the smelting of Abitibi ores as the source of contamination. An isotope mass balance model evaluates at roughly 7.5-20%, 5-40%, 5-9% and <3% the Pb contributions from local smelters at distances of 3.6, 3.9, 7 and 9 km, respectively. The dispersion of the Pb contamination plume is possibly driven by the distance from the Beattie smelter. We finally estimated a delay of at least 13 years between atmospheric emissions from the Beattie smelting activities and the time they are recorded by tree rings. Ultimately, this study demonstrates that white cedar tree rings series provide reliable archives of past and present Pb atmospheric contamination.

Levels, spatial distribution, risk assessment, and sources of environmental contamination vectored by road dust in Cienfuegos (Cuba) revealed by chemical and C and N stable isotope compositions.

Road dust is an indicator widely used when monitoring contamination and evaluating environmental and health risks in urban ecosystems. We conducted an exhaustive characterization of road dust samples coupling their chemical characteristics and stable isotope compositions (C and N) with the aim of evaluating the levels and spatial distribution of local contamination as well as to identify its main source(s) in the coastal city of Cienfuegos (Cuba). Results indicate that the concentrations of several elements (total nitrogen, S, Ca, V, Cu, Zn, Mo, Sn, Hg, and Pb) exceed the background values reported for both Cuban soils and the upper continental crust (UCC) and showed a high variability among the sampling sites. We show that road dust contamination in Cienfuegos induces high associated ecological risks. Among the studied elements, Cd and Hg are the major contributors to the environmental contamination in the city, mainly along busy roads and downtown. δ13C and δ15N, coupled to a multivariate statistical analysis, help associate the studied elements to several local sources of contamination: mineral matter derived from local soils, cement plant and related activities, road pavement alteration, power plant, road traffic, and resuspension of particulate organic matter (POM). Our results suggest that incorporating the chemical and isotope monitoring of road dust may help implement more effective environmental management measures in order to reduce their adverse impact on ecosystems and human health.

Nitrogen Speciation and Isotopic Composition of Aerosols Collected at Himalayan Forest (3326 m a.s.l.): Seasonality, Sources, and Implications.

Nitrogenous aerosols are ubiquitous in the environment and thus play a vital role in the nutrient balance as well as the Earth's climate system. However, their abundance, sources, and deposition are poorly understood, particularly in the fragile and ecosensitive Himalayan and Tibetan Plateau (HTP) region. Here, we report concentrations of nitrogen species and isotopic composition (δ15N) in aerosol samples collected from a forest site in the HTP (i.e., Southeast Tibet). Our results revealed that both organic and inorganic nitrogen contribute almost equally with high abundance of ammonium nitrogen (NH4+-N) and water-insoluble organic nitrogen (WION), contributing ∼40% each to aerosol total nitrogen (TN). The concentrations and δ15N exhibit a significant seasonality with ∼2 times higher in winter than in summer with no significant diurnal variations for any species. Moreover, winter aerosols mainly originated from biomass burning emissions from North India and East Pakistan and reached the HTP through a long-range atmospheric transport. The TN dry deposition and total deposition fluxes were 2.04 kg ha-1 yr-1 and 6.12 kg ha-1 yr-1 respectively. Our results demonstrate that the air contamination from South Asia reach the HTP and is most likely impacting the high altitude ecosystems in an accepted scenario of increasing emissions over South Asia.

Habitat use strategy influences the tissue signature of trace elements including rare earth elements in an urban-adapted omnivorous bird.

Concentrations of trace elements vary naturally between geological environments and as a result of emissions from anthropogenic activities. Habitat use strategy is an important determinant of trace element concentrations in tissues and eggs of wild birds. However, a scarcity of studies have documented the relationships between individual bird movements related to foraging activities and exposure to contaminants including trace elements. The objective of the present study was to investigate the influence of habitat use strategy, determined using GPS-based telemetry, on the liver concentrations of selected trace elements including rare earth elements (REEs) as well as lead (Pb) isotope ratios in an urban-adapted omnivorous bird, the ring-billed gull (Larus delawarensis). Male (n = 20) and female (n = 18) ring-billed gulls breeding near Montreal (QC, Canada) in one of the largest colony in North America were tracked using miniature GPS devices to characterize their movements over a 10-days period. The time spent foraging by both male and female gulls in landfills and wastewater basins positively correlated with liver Pb concentrations. A positive correlation was also found between the time spent foraging in agricultural fields and liver concentrations of yttrium (Y) in male and female ring-billed gulls. Heavy REE concentrations were significantly greater in female gull liver relative to those of males, although this was not associated with the time spent in any foraging habitats. Pb isotope ratios (208Pb/206Pb and 206Pb/207Pb) in the liver of male ring-billed gulls tended to be lower in individuals that foraged in landfills, thus indicating that they may have been exposed to different Pb sources relative to birds that visited other sites. This study provided valuable information on the potential sources of trace elements at the landscape level in free-ranging birds spanning urbanized environments.

Carbon and nitrogen isotopes unravels sources of aerosol contamination at Caribbean rural and urban coastal sites.

The constant increase of anthropogenic emissions of aerosols, usually resulting from a complex mixture from various sources, leads to a deterioration of the ambient air quality. The stable isotope compositions (δ13C and δ15N) of total carbon (TC) and nitrogen (TN) in both PM10 and emissions from potential sources were investigated for first time in a rural and an urban Caribbean costal sites in Cuba to better constrain the origin of the contamination. Emissions from road traffic, power plant and shipping emissions were discriminated by coupling their C and N contents and corresponding isotope signatures. Other sources (soil, road dust and cement plant), in contrast, presented large overlapping ranges for both C and N isotope compositions. δ13CPM10 isotope compositions in the rural (average of -25.4 ±â€¯1.2‰) and urban (average of -24.8 ±â€¯1.2‰) sites were interpreted as a mixture of contributions from two main contributors: i) fossil fuel combustion and ii) cement plant and quarries. Results also showed that this last source is impacting more air quality at the urban site. A strong influence from local wood burning was also identified at the rural site. These conclusions were comforted by a statistical analysis using a conditional bivariate probability function. TN and δ15N values from the urban site demonstrated that nitrogen in PM10 was generated by secondary processes through the formation of (NH4)2SO4. The exchange in the (NH4)2SO4 molecule between gaseous NH3 and particle NH4+ under stoichiometric equilibrium may control the observed 15N enrichment. At low nitrogen concentrations in the aerosols, representing PM10 with both the highest primary N and lowest secondary N proportions, comparison with the δ15N of potential sources indicate that emissions from diesel car and power plant emissions may represent the major vectors of primary nitrogen.

The coupled study of metal concentrations and electron paramagnetic resonance (EPR) of lichens (Hypogymnia physodes) from the Swietokrzyski National Park-environmental implications.

SO2, NOx, and metals (including Cd, Cu, Pb, Zn, Mn, Mg, Fe) present in airborne particulate matter are a major threat to preserving good air quality. The complicated pathways and transformation processes that can change their physical/chemical state in the atmosphere renders identifying their origin extremely difficult. With the objective of alleviating this difficulty, we identified and characterized potential local and regional sources of atmospheric pollutants using bioindicators (Hypogymnia physodes) from the Swietokrzyski National Park (SE Poland): 20 lichen samples were collected during winter (February; heating period) and summer (June; vegetative period) seasons and analyzed for metal contents and free radicals concentrations. Our results indicate that the highest gaseous pollutant levels were observed during the heating season, along roads (NO2) and at the highest elevation (SO2). The semiquinone/phenoxyl radical concentrations correlated during the heating season with the atmospheric SO2: ln (free radicals concentrations) = 0.025 SO2atmosphere + 39.11. For Mn/Fe ≥ 2, the electron paramagnetic resonance (EPR) spectra presented a hyperfine splitting. Results showed that since 1994 metal concentrations increased for Cd, Mn, and Mg, Fe remained somewhat constant for Zn and Cu but slightly decreased for Pb, in agreement with the phasing out of lead in gasoline. Finally, a principal component analysis (PCA) identified two main factors controlling variability within the analyzed parameters: air pollutants transport over long distances and local fuel combustion by both transport and home heating.

Characterizing sources and natural attenuation of nitrate contamination in the Baix Ter aquifer system (NE Spain) using a multi-isotope approach.

Nitrate pollution is a widespread issue affecting global water resources with significant economic and health effects. Knowledge of both the corresponding pollution sources and of processes naturally attenuating them is thus of crucial importance in assessing water management policies and the impact of anthropogenic activities. In this study, an approach combining hydrodynamic, hydrochemical and multi-isotope systematics (8 isotopes) is used to characterize the sources of nitrate pollution and potential natural attenuation processes in a polluted basin of NE Spain. δ2H and δ18O isotopes were used to further characterize the sources of recharge of the aquifers. Results show that NO3- is not homogeneously distributed and presents a large range of concentrations, from no NO3- to up to 480mgL-1. δ15N and δ18O of dissolved NO3- identified manure as the main source of nitrate, although sewage and mineral fertilizers can also be isotopically detected using boron isotopes (δ11B) and δ34S and δ18O of dissolved sulphate, respectively. The multi-isotope approach proved that natural denitrification is occurring, especially in near-river environments or in areas hydrologically related to fault zones. δ34S and δ18O indicated that denitrification is not driven by pyrite oxidation but rather by the oxidation of organic matter. This could not be confirmed by the study of δ13CHCO3 that was buffered by the entanglement of other processes and sources.

Strontium isotope characterization of wines from Quebec, Canada.

The (87)Sr/(86)Sr isotope ratios were measured on grape, wine and soil samples collected in 13 commercial vineyards located in three major wine producing areas of Quebec (Canada). The soils yield Sr isotope ratios that are intimately related to the local geology and unambiguously discriminate the different producing areas. A strong relationship exists between the (87)Sr/(86)Sr isotope ratios of the wine and the grapes. This suggests that the vinification process does not alter the overall Sr budget. Although the Sr isotope ratios of the grapes do not show a strong correlation with the bulk Sr isotope composition of the soil, they do correlate strongly with the Sr isotope composition contained in the labile fraction of the soil. This indicates that the labile fraction of the soil represents the Sr reservoir available to the plant during its growth. This study demonstrates that the Sr isotope approach can be used as a viable tool in forensic science for investigating the provenance of commercial wines.

Improved analysis of micro- and nanomole-scale sulfur multi-isotope compositions by gas source isotope ratio mass spectrometry.

RATIONALE: Multiple sulfur isotope compositions are usually measured on relatively large samples (in the range of micromoles); however, sometimes only small amounts are available and thus it is necessary to analyze small (sub-micromole) samples. We report an improved method to measure multiple sulfur isotope compositions: δ(33) S, δ(34) S and δ(36) S values on the SF6 molecule (m/z 127, 128, 129, 131) for quantities down to 0.1 micromole, and δ(33) S and δ(34) S values for quantities down to 20 nanomoles. METHODS: Multiple sulfur isotope analyses including fluorination and purification of two international Ag2 S standards, IAEA-S1 and IAEA-S3, were carried out at various low concentrations on a dual-inlet isotope ratio mass spectrometer using a microvolume and modified resistor capacities. RESULTS: The analyses yielded a narrow range of δ(34) S values vs CDT (the international standard), with an overall standard deviation of ±0.2 ‰, which was within the range of certified values. This demonstrates the feasibility of determining both Δ(33) S and Δ(36) S values on the sub-micromole scale, and Δ(33) S values on the nanomole scale with similar accuracy to conventional dual-inlet analyses. CONCLUSIONS: The analysis of the three S-isotope ratios on the SF6 molecule using the so-called conventional fluorination method and dual-inlet ion ratio mass spectrometry is reliable for sample sizes down to ~20 nanomoles. Despite being close to the theoretical limits for maintaining the viscous flow regime of gas in the capillary, errors were not limited by counting statistics, but probably relate to sample gas purification. Copyright © 2016 John Wiley & Sons, Ltd.

Assessing sources of nitrate contamination in the Shiraz urban aquifer (Iran) using the δ(15)N and δ(18)O dual-isotope approach.

Nitrate ([Formula: see text]) is one of the major threats to the quality of the drinking water taken from the Shiraz aquifer. This aquifer undergoes high anthropogenic pressures from multiple local urban (including uncontrolled sewage systems), agricultural and industrial activities, resulting in [Formula: see text] concentrations as high as 149 mg L(-1), well above the 50 mg L(-1) guideline defined by the World Health Organisation. We coupled here classical chemical and dual isotope (δ(15)N and δ(18)O of [Formula: see text]) approaches trying to characterize sources and potential processes controlling the budget of this pollutant. Chemical data indicate that nitrate in this aquifer is explained by distinct end-members: while mineral fertilizers isotopically show to have no impact, our isotope approach identifies natural soil nitrification and organic [Formula: see text] (manure and/or septic waste) as the two main contributors. Isotope data suggest that natural denitrification may occur within the aquifer, but this conclusion is not supported by the study of other chemical parameters.

Tracking mobility using human hair: What can we learn from lead and strontium isotopes?

The isotope ratios of strontium (Sr) and lead (Pb) in water derive from local geology and their isotopic signature can be linked to the age and type of underlying bedrocks and soils (if applicable), and are transferred up the food-chain. Both elements are transferred to human blood through diet and water, and some of it will ultimately be incorporated into the hair structure, making Sr and Pb isotopes interesting tools for tracing human mobility. In this study, we analyzed both the elemental concentration and isotope ratios of Sr and Pb from four different women of different ages to monitor their permanent relocation from central France to Eastern Canada during the summer 2012. For comparison, we also characterized bulk hair samples of sedentary individuals and local tap waters from their regions of origin and of settlement. Our results indicate that the 87Sr/86Sr and 206Pb/204Pb ratios are significantly modified by the change of environment, but also confirm that human hair compositions are impacted by other external factors (such as dust). Sr and Pb isotope systematics demonstrate their added value for detecting human mobility, but require further studies to better constrain the main sources and processes controlling their respective budgets in human hair for provenancing purposes.

Carbon isotope ratio measurements of glyphosate and AMPA by liquid chromatography coupled to isotope ratio mass spectrometry.

The interest in compound-specific isotope analysis for product authenticity control and source differentiation in environmental sciences has grown rapidly during the last decade. However, the isotopic analysis of very polar analytes is a challenging task due to the lack of suitable chromatographic separation techniques which can be used coupled to isotope ratio mass spectrometry. In this work, we present the first method to measure carbon isotope compositions of the widely applied herbicide glyphosate and its metabolite aminomethylphosphonic acid (AMPA) by liquid chromatography coupled to isotope ratio mass spectrometry. We demonstrate that this analysis can be carried out either in cation exchange or in reversed-phase separation modes. The reversed-phase separation yields a better performance in terms of resolution compared with the cation exchange method. The measurement of commercial glyphosate herbicide samples show its principal applicability and reveals a wide range of δ(13)C values between -24 and -34 ‰ for different manufacturers. The absolute minimum amounts required to perform a precise and accurate determination of carbon isotope compositions of glyphosate and AMPA were in the sub-microgram range. The method proposed is sensitive enough to further perform the experiments that are necessary to better understand the carbon isotope fractionation associated to the natural degradation of glyphosate into AMPA. Furthermore, it can be used for contaminant source allocation and product authenticity as well.

Improving the management of nitrate pollution in water by the use of isotope monitoring: the δ15N, δ18O and δ11B triptych.

In spite of increasing efforts to reduce nitrogen inputs into ground water from intensive agriculture, nitrate (NO(3)) remains one of the major pollutants of drinking-water resources worldwide, with NO(3) levels approaching the defined limit of 50 mg l(-1) in an increasing number of water bodies. Determining the source(s) of contamination in water is an important first step for improving its quality by emission control. The Life ISONITRATE project aimed at showing the benefit of a multi-isotope approach (δ(15)N and δ(18)O of NO(3), and δ(11)B), in addition to conventional hydrogeological analysis, to track the origin of NO(3) contamination in water. Based on land use and local knowledge, four distinct cases were studied: (1) natural soil NO(3), (2) natural denitrification, (3) single source of NO(3) pollution and (4) multiple sources of NO(3) pollution. Our results show the added value of combining isotope information, compared to knowledge based on local authorities' experience, land use and the 'classical' chemical approach, by efficiently identifying the number and type of NO(3) source(s) for each watershed studied.