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Identifying discontinuities of flood frequency curves
Get PDFDiscontinuities in flood frequency curves, here referred to as flood divides, hinder the estimation of rare floods. In this paper we develop an automated methodology for the detection of flood divides from observations and models, and apply it to a large set of case studies in the USA and Germany. We then assess the reliability of the PHysically-based Extreme Value (PHEV) distribution of river flows to identify catchments that might experience a flood divide, validating its results against observations. This tool is suitable for the identification of flood divides, with a high correct detection rate especially in the autumn and summer seasons. It instead tends to indicate the emergence of flood divides not visible in the observations in spring and winter. We examine possible reasons of this behavior, finding them in the typical streamflow dynamics of the concerned case studies. By means of a controlled experiment we also re-evaluate detection capabilities of observations and PHEV after discarding the highest maxima for all cases where both empirical and theoretical estimates display flood divides. PHEV mostly confirms its capability to detect a flood divide as observed in the original flood frequency curve, even if the shortened one does not show it. These findings prove its reliability for the identification of flood divides and set the premises for a deeper investigation of physiographic and hydroclimatic attributes controlling the emergence of discontinuities in flood frequency curves.publishedVersio
Undersøkelse av innsjøresipienter fra Larvikittbruddene, fase 1 - 2022
Get PDFProsjektleder: Camilla H. Corneliussen HagmanTo innsjøer nedstrøms Larvikitt-bruddet i Tvedalen, Larvik kommune, ble i 2022 undersøkt for effekter av påvirkning fra steinbruddet på vannkvalitet, sedimenter, vannplanter og bunndyr. Undersøkelsen ble utført som en oppfølging av tidligere undersøkelser i 2007 og 2008. Resultatene tyder på at vannkvaliteten i innsjøene ikke er eutrofierte, og at turbiditeten er betydelig bedret, men at forholdene fremdeles tilsier signifikant partikkelpåvirkning i form av reduserte lysforhold for vannplanter, spesielt i Bålsrødvannet. I Torpevannet ble det funnet svært lite vannplanter uten opplagt årsak til dette, derfor kunne ikke effekter fra steinbruddet vurderes. Bunndyrundersøkelsene ga ingen opplagte svar på omfanget av evt. påvirkning fra steinbruddet. Resultatene fra 2022 tyder totalt sett på at Bålsrødvannet er mest, og fremdeles, preget av partikkelforurensning fra Tvedalen steinbrudd, men at forholdene er betydelig bedret siden 2007 og 2008.WSP Norge ASpublishedVersio
Forhold for overlevelse av Gyrodactylus salaris i Oslofjorden
Get PDFProsjektleder: André StaalstrømI denne rapporten har modellkjøringer med FjordOs-modellen blitt kalibrert mot målinger av saltholdighet i overflatelaget i Oslofjorden. Disse modellresultatene er brukt for å vurdere muligheten for at vandrende laks kan overføre parasitten Gyrodactylus salaris fra elv til elv via sjøen. Det er en mulighet for G.salaris kan overføres fra Drammenselva til Aulivassdraget, selv om sannsynligheten for at dette skjer er liten. I en ekstrem flomsituasjon i fjordsystemet slik som den i juni 1995, vil det være stor sannsynlighet for at parasitter ville overleve på fisk hvis de hadde vandret mellom Glomma og Aulivassdraget, eller motsatt.Vestfold og Telemark fylkeskommunepublishedVersio
Measuring riverine macroplastic: Methods, harmonisation, and quality control
Get PDFRiver systems are a key environmental recipient of macroplastic pollution. Understanding the sources of macroplastic to rivers and the mechanisms controlling fate and transport is essential to identify and tailor measures that can effectively reduce global plastic pollution. Several guidelines exist for monitoring macroplastic in rivers; yet, no single method has emerged representing the standard approach. This reflects the substantial variability in river systems globally and the need to adapt methods to the local environmental context and monitoring goals. Here we present a critical review of methods used to measure macroplastic flows in rivers, with a specific focus on opportunities for methods testing, harmonisation, and quality assurance and quality control (QA/QC). Several studies have already revealed important findings; however, there is significant disparity in the reporting of methodologies and data. There is a need to converge methods, and their adaptations, towards greater comparability. This can be achieved through: i) methods testing to better understand what each method effectively measures and how it can be applied in different contexts; ii) incorporating QA/QC procedures during sampling and analysis; and iii) reporting methodological details and data in a more harmonised way to facilitate comparability and the utilisation of data by several end users, including policy makers. Setting this as a priority now will facilitate the collection of rigorous and comparable monitoring data to help frame solutions to limit plastic pollution, including the forthcoming global treaty on plastic pollution.publishedVersio
Biogeochemical structure of the Laptev Sea in 2015-2020 associated with the River Lena plume
Get PDFThe discharge of rivers and the subsequent dispersion of their plumes play a pivotal role in the biogeochemical cycling of the Arctic Ocean. Based on the data collected during annual transects conducted in the autumn period (September-October) from 2015-2020, this study explores the effect of River Lena plume dispersion on the seasonal and interannual changes in the hydrophysical and biogeochemical structure of the southeastern Laptev Sea. The temperature-salinity relationship (T-S), Redfield ratio and multiparameter cluster analysis were used to investigate variations in the water mass structure along the transect. The results revealed that the plume’s interannual and seasonal spreading patterns play a crucial role in regulating the local physical, biogeochemical, and biological processes in the southern Laptev Sea. During September-October, the hydrochemical water mass structure along the transects shifted from highly stratified to unstratified as the plume’s mixing intensity increased. Anomalous hydrochemical distributions were observed due to coastal upwelling, which was primarily characterized by high total alkalinity and nitrate levels, and low organic phosphorus, nitrite, and ammonia levels in the seawater. Wind and cold weather conditions drive deep vertical mixing of seawater, causing the resuspension of bottom sediment and the subsequent enrichment of bottom water by nutrients. Multi-parameter cluster analysis is used to describe the details of water mass structures in the highly dynamic southern Laptev Sea, with water mass structures typically undergoing significant changes within two weeks between September and October. The migration and transformation of water masses throughout the seasons are influenced by the volume of river discharge, fall-winter cooling, and atmospheric circulation patterns. Furthermore, the general atmospheric circulation is confirmed to be the primary cause of the interannual variation in the spread of the Lena River plume over the southeast Laptev Sea.publishedVersio
Floating Riverine Litter Flux to the White Sea: Seasonal Changes in Abundance and Composition
Get PDFArctic rivers bring litter from their basins to the sea, but accurate data for the Arctic do not exist yet. This study presents the first assessment of floating macro litter input (>2.5 cm) from the Northern Dvina and Onega rivers to the White Sea. The observations were performed based on the European Marine Strategy Framework Directive (MSFD) methodology and using the mobile application of the Joint Research Centre (Ispra, Italy). The results of observations from May 2021 to November 2021 show that 77% of floating objects were of natural origin (mainly leaves, wood and bird feathers). Of the particles of anthropogenic origin, 59.6% were represented by various types of plastics, 27.7% were processed wood, 8.5% paper/cardboard, 2.7% metal, 1.1% were rubber and <1% textiles. The average monthly input of anthropogenic macro litter by the Northern Dvina varies from 250 to 1700 items/hour, and by Onega from 520 to 2350 items/hour. The level of pollution of the studied rivers was found to be higher than in some Europeans rivers but lower than in China. The mass discharge of macroplastics in the Northern Dvina River was compared with the estimates of the discharge of meso- and microplastics; that allowed us to show that the discharge of macroplastics in mass units is much higher than of micro- and mesoplastics.publishedVersio
Tilstandsklassifisering av makroalger i sjøsonen. Revidering av komboindeksen.
Get PDFProsjektleder: Camilla With FagerliKomboindeksen er en klassifiseringsindeks for makroalger som baserer seg på vurderinger av makroalgesamfunnets tilstand i fjæresonen kombinert med vurderinger i sjøsonen. Komboindeksen har blitt utprøvd gjennom Miljødirektoratets ØKOKYST program siden 2017. Det er ønskelig å tilpasse komboindeksen slik at den kan inkluderes som indeks for tilstandsvurdering av makroalgesamfunn i klassifiseringsveilederen. Basert på nåværende kunnskapsgrunnlag foreslås det å inkludere nedre voksedyp for sukkertare og beitetrykk fra kråkeboller som vurderingsparametere for økologisk tilstandsvurdering i en revidert utgave av komboindeksen. For å undersøke sammenhengen mellom organisk belastning og masseforekomster av filtrerende organismer bør forekomsten av filtrerende organismer registreres systematisk under datainnsamling for komboindeksen.MiljødirektoratetpublishedVersio
Microplastics could be marginally more hazardous than natural suspended solids - A meta-analysis
Get PDFMicroplastics (MP) are perceived as a threat to aquatic ecosystems but bear many similarities to suspended sediments which are often considered less harmful. It is, therefore pertinent to determine if and to what extent MP are different from other particles occurring in aquatic ecosystems in terms of their adverse effects. We applied meta-regressions to toxicity data extracted from the literature and harmonized the data to construct Species Sensitivity Distributions (SSDs) for both types of particles. The results were largely inconclusive due to high uncertainty but the central tendencies of our estimates still indicate that MP could be marginally more hazardous compared to suspended sediments. In part, the high uncertainty stems from the general lack of comparable experimental studies and dose-dependent point estimates. We therefore argue that until more comparable data is presented, risk assessors should act precautionary and treat MP in the 1–1000 µm size range as marginally more hazardous to aquatic organisms capable of ingesting such particles.publishedVersio
Kartlegging av radioaktive stoffer i Oslofjorden
Get PDFProsjektleder: Anders RuusDSA har ønsket å undersøke om utslipp av radioaktive stoffer fra helsesektoren kan gjenfinnes i miljøet og om I-131 tas opp og/eller oppkonsentrerer i Oslofjorden. Det ble ikke funnet I-131 eller Tc-99m i biota i detekterbare mengder. Dette tyder på lavt opptak, og liten tilknyttet risiko for organismer i Oslofjorden. Lave konsentrasjoner av Tc-99m og I-131 ble målt i noen vannprøver, samt I-131 i noen sediment prøver. Lu-177 ble ikke detektert i noen prøver. Disse observasjonene er ikke i konflikt med strømningsmønsteret i området, men partiklene skal også rekke å sedimentere til bunnen, tidsnok til at deteksjon er mulig (I-131 har halveringstid på 8 døgn). Selv med fordeling av prøvene over fire ulike prøveinnsamlingstidspunkter ble det for lang tid mellom prøvetaking og måling, med så lave konsentrasjoner av kortlevde radionuklider. Med så lave nivåer må man i fremtiden ta sikte på færre prøver og enda kortere tid mellom prøvesamling og måling, kanskje ved å fokusere på et mindre geografisk område. Resultatene gir et innblikk i situasjonen før en forventet økning i bruk av nukleærmedisin ved sykehusene.Direktoratet for strålevern og atomsikkerhet (DSA)publishedVersio
Insights from the management of offshore energy resources: Toward an ecosystem-services based management approach for deep-ocean industries
Get PDFThe deep ocean comprises complex ecosystems made up of numerous community and habitat types that provide multiple services that benefit humans. As the industrialization of the deep sea proceeds, a standardized and robust set of methods and metrics need to be developed to monitor the baseline conditions and any anthropogenic and climate change-related impacts on biodiversity, ecosystem function, and ecosystem services. Here, we review what we have learned from studies involving offshore-energy industries, including state-of-the-art technologies and strategies for obtaining reliable metrics of deep-sea biodiversity and ecosystem function. An approach that includes the detection and monitoring of ecosystem services, with open access to baseline data from multiple sectors, can help to improve our global capacity for the management of the deep ocean.publishedVersio