Добірка наукової літератури з теми "Nitrate legacy"

Abstract. While eutrophication is often attributed to contemporary nutrient pollution, there is growing evidence that past practices, like the accumulation of legacy sediment behind historic milldams, are also important. Given their prevalence, there is a critical need to understand how N flows through, and is retained in, legacy sediments to improve predictions and management of N transport from uplands to streams in the context of climatic variability and land-use change. Our goal was to determine how nitrate (NO3−) is cycled through the soil of a legacy-sediment-strewn stream before and after soil drying. We extracted 10.16 cm radius intact soil columns that extended 30 cm into each of the three significant soil horizons at Big Spring Run (BSR) in Lancaster, Pennsylvania: surface legacy sediment characterized by a newly developing mineral A horizon soil, mid-layer legacy sediment consisting of mineral B horizon soil and a dark, organic-rich, buried relict A horizon soil. Columns were first preincubated at field capacity and then isotopically labeled nitrate (15NO3−) was added and allowed to drain to estimate retention. The columns were then air-dried and subsequently rewet with N-free water and allowed to drain to quantify the drought-induced loss of 15NO3− from the different horizons. We found the highest initial 15N retention in the mid-layer legacy sediment (17 ± 4 %) and buried relict A soil (14 ± 3 %) horizons, with significantly lower retention in the surface legacy sediment (6 ± 1 %) horizon. As expected, rewetting dry soil resulted in 15N losses in all horizons, with the greatest losses in the buried relict A horizon soil, followed by the mid-layer legacy sediment and surface legacy sediment horizons. The 15N remaining in the soil following the post-drought leaching was highest in the mid-layer legacy sediment, intermediate in the surface legacy sediment, and lowest in the buried relict A horizon soil. Fluctuations in the water table at BSR which affect saturation of the buried relict A horizon soil could lead to great loses of NO3− from the soil, while vertical flow through the legacy-sediment-rich soil profile that originates in the surface has the potential to retain more NO3−. Restoration that seeks to reconnect the groundwater and surface water, which will decrease the number of drying–rewetting events imposed on the relict A horizon soils, could initially lead to increased losses of NO3− to nearby stream waters.

ABSTRACTThe effect of long-term mixed-waste contamination, particularly uranium and nitrate, on the microbial community in the terrestrial subsurface was investigated at the field scale at the Oak Ridge Integrated Field Research Challenge (ORIFRC) site in Oak Ridge, TN. The abundance, community composition, and distribution of groundwater microorganisms were examined across the site during two seasonal sampling events. At representative locations, subsurface sediment was also examined from two boreholes, one sampled from the most heavily contaminated area of the site and another from an area with low contamination. A suite of DNA- and RNA-based molecular tools were employed for community characterization, including quantitative PCR of rRNA and nitrite reductase genes, community composition fingerprinting analysis, and high-throughput pyrotag sequencing of rRNA genes. The results demonstrate that pH is a major driver of the subsurface microbial community structure and that denitrifying bacteria from the genusRhodanobacter(classGammaproteobacteria) dominate at low pH. The relative abundance of bacteria from this genus was positively correlated with lower-pH conditions, and these bacteria were abundant and active in the most highly contaminated areas. Other factors, such as the concentration of nitrogen species, oxygen level, and sampling season, did not appear to strongly influence the distribution ofRhodanobacterbacteria. The results indicate that these organisms are acid-tolerant denitrifiers, well suited to the acidic, nitrate-rich subsurface conditions, and pH is confirmed as a dominant driver of bacterial community structure in this contaminated subsurface environment.

Abstract. Increased anthropogenic inputs of nitrogen (N) to the biosphere during the last few decades have resulted in increased groundwater and surface water concentrations of N (primarily as nitrate), posing a global problem. Although measures have been implemented to reduce N inputs, they have not always led to decreasing riverine nitrate concentrations and loads. This limited response to the measures can either be caused by the accumulation of organic N in the soils (biogeochemical legacy) – or by long travel times (TTs) of inorganic N to the streams (hydrological legacy). Here, we compare atmospheric and agricultural N inputs with long-term observations (1970–2016) of riverine nitrate concentrations and loads in a central German mesoscale catchment with three nested subcatchments of increasing agricultural land use. Based on a data-driven approach, we assess jointly the N budget and the effective TTs of N through the soil and groundwater compartments. In combination with long-term trajectories of the C–Q relationships, we evaluate the potential for and the characteristics of an N legacy. We show that in the 40-year-long observation period, the catchment (270 km2) with 60 % agricultural area received an N input of 53 437 t, while it exported 6592 t, indicating an overall retention of 88 %. Removal of N by denitrification could not sufficiently explain this imbalance. Log-normal travel time distributions (TTDs) that link the N input history to the riverine export differed seasonally, with modes spanning 7–22 years and the mean TTs being systematically shorter during the high-flow season as compared to low-flow conditions. Systematic shifts in the C–Q relationships were noticed over time that could be attributed to strong changes in N inputs resulting from agricultural intensification before 1989, the break-down of East German agriculture after 1989 and the seasonal differences in TTs. A chemostatic export regime of nitrate was only found after several years of stabilized N inputs. The changes in C–Q relationships suggest a dominance of the hydrological N legacy over the biogeochemical N fixation in the soils, as we expected to observe a stronger and even increasing dampening of the riverine N concentrations after sustained high N inputs. Our analyses reveal an imbalance between N input and output, long time-lags and a lack of significant denitrification in the catchment. All these suggest that catchment management needs to address both a longer-term reduction of N inputs and shorter-term mitigation of today's high N loads. The latter may be covered by interventions triggering denitrification, such as hedgerows around agricultural fields, riparian buffers zones or constructed wetlands. Further joint analyses of N budgets and TTs covering a higher variety of catchments will provide a deeper insight into N trajectories and their controlling parameters.

L’anthropisation grandissante des bassins versants côtiers représente une menace importante pour les eaux souterraines et les écosystèmes qui en dépendent, alors appelés « écosystèmes tributaires des eaux souterraines ». A l’image de l’hydrosystème de Biguglia (Corse), l’urbanisation rapide et désorganisée ainsi que les activités industrielles et agricoles développées sur la plaine de la Marana sont autant de sources de dégradation des eaux souterraines. Cette ressource, pourtant stratégique et utilisée pour l’alimentation en eau potable de la région bastiaise, présente aujourd’hui les marqueurs d’une contamination multiple et diffuse sur l’ensemble de la plaine. En plus d’être problématique pour les besoins en eau humains, la dégradation qualitative des eaux souterraines de l’aquifère de la Marana, constitue également une menace pour l’écosystème fragile de la lagune de Biguglia et la pérennité des services écosystémiques qu’il prodigue. Dans ce contexte de pressions croissantes, la connaissance approfondie du fonctionnement de l’hydrosystème de Biguglia s’impose comme un élément essentiel pour garantir une gestion durable de la ressource en eau. Dans ce but, une approche multi-traceurs géochimiques et isotopiques a été développée afin notamment de mieux contraindre l’état de la ressource, les conditions hydrodynamiques et la nature des interactions aquifères-rivières-lagune. L’étude des isotopes stables de la molécule d’eau (18O, 2H) a mis en évidence la complexité de la recharge. L’aquifère de la Marana bénéficie d’une recharge autochtone par l’infiltration directe des précipitations sur la plaine et d’une recharge allochtone par les précipitations en provenance des contreforts schisteux. A ces mécanismes, s’ajoute également la recharge prodiguée par l’infiltration des eaux du Bevincu et du Golu et la contribution latérale des eaux en provenance des contreforts schisteux de la Corse alpine. Le modèle de mélange développé (18O, Cl- et HCO3-) a permis une estimation semi-quantitative des mélanges. Il démontre la complexité du fonctionnement de l’aquifère, avec une différence notable de la contribution des contreforts schisteux en fonction de la localisation et de la profondeur de la ressource. Il apparaît également de manière claire que la lagune de Biguglia est partiellement tributaire des eaux souterraines. La plaine de la Marana est sujette à une dégradation qualitative liée à la présence excessive de nitrates (NO3-) et de micropolluants organiques. D’après les isotopes du NO3- (15N-NO3-, 18O-NO3-) et du Bore (11B), les principales sources d’azote sont le sol et les eaux usées. La corrélation entre concentrations en NO3- et temps de résidence des eaux (3H et CFCs) a mis en avant la capacité de stockage et d’archivage des eaux souterraines de l’aquifère de la Marana. Mise au regard de l’évolution de l’occupation des sols sur la plaine, la modification progressive des sources azotées enregistrée dans l’aquifère a permis de retracer la trajectoire socio-environnementale de l’hydrosystème de Biguglia. L’état contemporain dégradé de la ressource découle en grande partie de l’héritage des pollutions liées aux activités humaines historiques. Le modèle conceptuel élaboré grâce à ces travaux apporte de nouveaux éléments de compréhension qui pourront aider à l’instauration de stratégies de gestion pertinentes, assurant la pérennité future des ressources en eau et des services écosystémiques qui en dépendent
The exacerbated anthropization of coastal hydrosystems poses a significant threat to groundwater and ecosystems that depend on it, then called "groundwater-dependent ecosystems". Like the Biguglia hydrosystem (Corsica, France), rapid and disorganized urbanization, as well as industrial and agricultural activities developed on the Marana plain are major sources of groundwater degradation. This strategic resource, used for the drinking water supply of the Bastia urban area, presents the markers of multiple and diffuse contaminations. In addition to being problematic for human water needs, the groundwater qualitative degradation of the Marana aquifer also constitutes a threat to the fragile ecosystem of the Biguglia lagoon and the sustainability of the ecosystem services it provides. In this context of increasing pressures, a strong knowledge of the Biguglia hydrosystem behavior is essential to ensure sustainable management of water resources. To this end, a multi-tracer geochemical and isotopic approach has been developed in order to better constrain the state of the groundwater resource, the hydrodynamic conditions and the nature of aquifer-river-lagoon interactions. The study of the stable isotopes of the water molecule (18O, 2H) has highlighted the recharge complexity. The Marana aquifer benefits from an indigenous recharge through direct infiltration of precipitation on the plain and an allochthonous recharge through precipitation from the schistous reliefs. The infiltration of river water from the Bevincu and Golu rivers and the lateral contribution of water from the schistous reliefs also contribute to the aquifer recharge. The developed mixing model (18O, Cl- and HCO3-) allowed a semi-quantitative estimation of the mixing processes. It demonstrates the complex aquifer behavior, with a significant difference in the contribution of schistous groundwater depending on the location and depth of the resource. It is also clear that the Biguglia lagoon is partially dependent on groundwater. The Marana plain is subject to qualitative degradation due to the excessive presence of nitrates (NO3-) and organic micropollutants. According to the NO3- (15N-NO3-, 18O-NO3-) and Boron (11B) isotopes, the main sources of nitrogen are soil and wastewater. The correlation between NO3- concentrations and water residence time (3H and CFCs) highlighted the storage and the groundwater archiving capacity. With regard to the evolution of land use, the progressive modification of the nitrogen sources recorded in the aquifer made it possible to trace the socio-environmental trajectory of the Biguglia hydrosystem. The contemporary degraded state of the resource mainly results from the pollution legacy linked to historical human activities. The conceptual model developed provides new elements that can help towards the implementation of relevant management strategies, to ensure the sustainability of water resources and associated ecosystem services

Abstract Traditionally, negative environmental impacts of cutting fluid disposal have not been considered during cutting fluid selection. These impacts may result from hazardous chemicals or chips that might be found in a spent cutting fluid or from excesses in biochemical oxygen demand (BOD), oil content (FOG), nitrates, or phosphates that cutting fluids typically feature. By considering the portion of the cutting fluid life cycle after final use at the machine tool, this work considers simple, quantifiable metrics that might be used to compare fluids based on their impact on industrial wastewater pre-treatments and publicly owned treatment works (POTWs). The discussion begins with definitions of various environmental issues associated with cutting fluid disposal. Subsequently, a three component matrix is developed that can serve as a metric to compare alternative cutting fluids on the basis of the cost of disposal and legally defined hazards due to fluid chemistry and workpiece residuals found in cutting fluid wastes.

The employer is obliged to proceed with accordance with a large number of legal norms. The act of law no. 82/2005 Collection of laws on Illegal employment is one of them. The article presented deals with the topic of illegal employment. The goal of the article is to analyse the actual situation concerning the illegal employment considering the individual regions of Slovakia based on data provided by National Labour Inspectorate, Central Office of Labour, Social Affairs and Family and Offices of Labour, Social Affairs and Family. Based on information acquired, it is possible to state, that the most violations of the prohibition of illegal employment were discovered by inspections in the Nitra, Bratislava and Košice Regions. The least number of violations of the prohibition of illegal employment discovered by the competent authorities were in the Trenčín Region. It should be in the interest of the state that the people work based on legal contracts as it is the base of financial and budgetary stability of the state in the field of taxes and levies. Because of that reason, it would be suitable to intensify the inspections in the field concerned. The improvement of the economic environment and decreasing of the tax-levy burden of employers could also help to reduce the attractivity of illegal employment to the employers.