Browsing by Subject "nitrate"

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  • Rankinen, Katri; Holmberg, Maria; Peltoniemi, Mikko; Akujärvi, Anu; Anttila, Kati; Manninen, Terhikki; Markkanen, Tiina (Molecular Diversity Preservation International (MDPI), 2021)
    Water 13 (2021), 472
    Climate change may alter the services ecosystems provide by changing ecosystem functioning. As ecosystems can also resist environmental perturbations, it is crucial to consider the different processes that influence resilience. Our case study considered increased NO3− concentration in drinking water due to the climate change. We analyzed changes in ecosystem services connected to water purification at a catchment scale in southern Finland. We combined climate change scenarios with process-based forest growth (PREBAS) and eco-hydrological (PERSiST and INCA) models. We improved traditional model calibration by timing of forest phenology and snow-covered period from network of cameras and satellite data. We upscaled the combined modelling results with scenarios of population growth to form vulnerability maps. The boreal ecosystems seemed to be strongly buffered against NO3- leaching by increase in evapotranspiration and vegetation NO3- uptake. Societal vulnerability varied greatly between scenarios and municipalities. The most vulnerable were agricultural areas on permeable soil types.
  • Alasaarela, Juha (Helsingin yliopisto, 2019)
    Ruukkusalaattien tuotanto on kasvanut Suomessa jo vuosikymmeniä. Kasvihuoneet mahdollistavat tuoreiden lehtivihannesten kasvatuksen ympärivuotisesti, mutta pimeä vuodenaika tai valonsaannin heikentyminen yhdessä korkean nitraattilannoituksen kanssa aiheuttavat nitraatin kertymistä salaattiin. Nitraatti ei itsessään ole kovin myrkyllistä ihmiselle, mutta sen aineenvaihduntatuotteet elimistössä voivat olla haitallisia. Siksi ravinnon nitraattipitoisuuksia rajoitetaan EU asetuksella ja kasvisten nitraattipitoisuuksia valvoo Ruokavirasto. Tutkimuksen tavoitteena oli selvittää jääsalaatin (Lactuca sativa L.) nitraattipitoisuuteen vaikuttavia tekijöitä yksityisellä kasvihuonepuutarhalla, ja ehdottaa helposti sovellettavia keinoja nitraattipitoisuuden alentamiseksi. Tutkimuksessa mitattiin vuorokaudenajan, iän ja olosuhteiden vaikutusta jääsalaatin nitraattipitoisuuteen. Mittaukset tehtiin eri kellonaikoina korjatuilta salaateilta, neljän, viiden ja kuuden viikon ikäisiltä salaateilta, sekä viikoittaisilla seurantamittauksilla kolmen kuukauden ajan syksyllä 2017. Salaattien nitraattipitoisuus määriteltiin pikamittausmenetelmällä. Kasveille tulevaa PAR-valoa ja kiertoliuoksen nitraattityppipitoisuutta mitattiin jatkuvatoimisella mittalaitteella. Lisäksi kasvihuoneen automaattisesta ohjausjärjestelmästä saatiin tietoa muista kasvuolosuhteista. Sadonkorjuun kellonaika ei vaikuttanut jääsalaatin nitraattipitoisuuteen. Ikä vaikutti neljän ja viiden viikon ikäisten salaattien nitraattipitoisuuteen, mutta paremmissa valo-olosuhteissa iän vaikutus heikkeni kuuden viikon ikäisillä salaateilla. Nitraattityppilannoituksella ei ollut suoraa vaikutusta salaatin nitraattipitoisuuteen, mutta enemmän valoa saaneissa salaateissa oli vähemmän nitraattia. Kasvuston tasolta tehdystä jatkuvatoimisesta valon mittauksesta on hyötyä salaatin nitraattipitoisuuden hallinnassa. Riski nitraatin enimmäispitoisuusrajan ylitykseen on suuri syyskuussa luonnonvalon määrän vähentyessä. Tekovalojen käytön lisäämisellä voidaan alentaa salaatin nitraattipitoisuutta.
  • Suomi, Johanna; Ranta, Jukka; Tuominen, Pirkko; Hallikainen, Anja; Putkonen, Tiina; Bäckman, Christina; Ovaskainen, Marja-Leena; Virtanen, Suvi; Savela, Kirsti (Evira, 2013)
    Eviran tutkimuksia 2/2013
    Nitraattia esiintyy luonnostaan monissa kasviksissa ja talousvedessä. Osa syödystä nitraatista muuttuu elimistössä nitriitiksi. Nitraattia ja nitriittiä käytetään myös elintarvikelisäaineina, koska ne hillitsevät haitallisten mikrobien kasvua. Toisaalta niiden suuren saannin katsotaan aiheuttavan terveyshaittoja. Esitetty probabilistinen riskinarviointi perustuu vuosina 2004 – 2012 tutkittuihin valvonta- ja tutkimusprojektinäytteisiin sekä kirjallisuustietoihin. Lisäksi käytettiin Terveyden ja hyvinvoinnin laitokselta saatuja Finravinto 2007- ja DIPP-ravintotutkimuksen tuottamia aikuisten ja lasten ruoankulutustietoja. Nitraattialtistus lisäainelähteistä on vähäistä. Valtaosa nitraattialtistuksesta saadaan luontaisista lähteistä: vihanneksista, hedelmistä ja vedestä. Kasvisten käsittely ja hyvä viljelykäytäntö vähentävät saantia. Paljon nitraattia sisältävien kasvisten suurkuluttajien altistus voi ylittää nitraatin hyväksyttävän päivittäissaannin (ADI). Nitriittialtistus elintarvikkeista ja talousvedestä voi ylittää ADI-arvon noin 14 %:lla 3-vuotiaista ja 11 %:lla 6-vuotiaista suomalaislapsista. Suurin altistuslähde ovat ruokamakkarat. Toisaalta jos nitriittipitoisuuksia alennettaisiin nykytasosta, hygieniavaatimuksia ja kylmäketjuhallintaa olisi tehostettava.
  • Uusheimo, Sari; Tulonen, Tiina; Huotari, Jussi; Arvola, Lauri (2020)
    Agriculture contributes significantly to phosphorus and nitrogen loading in southern Finland. Climate change with higher winter air temperatures and precipitation may also promote loading increase further. We analyzed long-term nutrient trends (2001-2020) based on year-round weekly water sampling and daily weather data from a boreal small agricultural watershed. In addition, nutrient retention was studied in a constructed sedimentation pond system for two years. We did not find any statistically significant trends in weather conditions (temperature, precipitation, discharge, snow depth) except for an increase in discharge in March. Increasing trends in annual concentrations were found for nitrate, phosphate, and total phosphorus and total nitrogen. In fact, phosphate concentration increased in every season and nitrate concentration in other seasons except in autumn. Total phosphorus and total nitrogen concentrations increased in winter as well and total phosphorus also in summer. Increasing annual loading trend was found for total phosphorus, phosphate, and nitrate. Increasing winter loading was found for nitrate and total nitrogen, but phosphate loading increased in winter, spring, and summer. In the pond system, annual retention of total nitrogen was 1.9-4.8% and that of phosphorus 4.3-6.9%. In addition, 25-40% of suspended solids was sedimented in the ponds. Our results suggest that even small ponds can be utilized to decrease nutrient and material transport, but their retention efficiency varies between years. We conclude that nutrient loading from small boreal agricultural catchments, especially in wintertime, has already increased and is likely to increase even further in the future due to climate change. Thus, the need for new management tools to reduce loading from boreal agricultural lands becomes even more acute.
  • Soronen, Päivi (Helsingin yliopisto, 2019)
    Nitrogen (N) availability often limits plant growth in the boreal forest ecosystem. There has been a lack of reliable method to study soil N supply as in traditionally used potassium chloride (KCl) extraction sampling and sample preparation disturb soil structure and stimulate N mineralization, leading to the overestimation of inorganic N forms ammonium (NH4+) and nitrate (NO3-) and underestimation of organic N forms such as amino acids. Diffusion-based microdialysis technique for the sampling of soil diffusive N fluxes gives an opportunity to study soil N supply at a scale that is relevant for plant N uptake, as microdialysis probe has a membrane that reminds the plant fine root in its scale and also, to some extent, in its function. During sampling, the movement of water inside the microdialysis probe induces diffusive flux of solutes across the membrane surface along the concentration gradient. The aim of this study was to test the performance of microdialysis technique at different soil moisture content levels and its capability to monitor temporal changes in diffusive N fluxes in laboratory experiments (ex situ). Soil fine-scale N dynamics were further studied by comparing the diffusive N fluxes in the field (in situ) in boreal forest soil to multiple factors that are thought to affect forest soil N availability. In this study, soil diffusive NH4+, NO3- and amino acid N fluxes were sampled ex situ from sieved soils taken from three different sites – clear-cut, spruce stand (MT spruce) and pine stand (VT pine) in Lapinjärvi, Finland in November 2017. In ex situ microdialysis experiments, the diffusive N fluxes were observed at three different soil moisture content levels and after N addition. In situ microdialysis sampling was run at the logging residue experiment of the Lapinjärvi clear-cut site and at the MT spruce site in June 2018 and at the pine logging residue experiment in Kiikala, Finland in September 2018. The results from the in situ microdialysis were compared with soil moisture content, pH, C-to-N ratio and temperature as well as with the net N mineralization and net nitrification rates, microbial biomass C and N contents and the concentrations of volatile monoterpenes and condensed tannins, factors that are assumed to affect N availability in forest soil. Nitrogen fluxes sampled ex situ showed that the total amino acid flux in the soil taken from the clear-cut site was only half of that in the MT spruce soil whereas NO3- flux was two times higher at the clear-cut site than at the MT spruce site. MT spruce soil with a moisture content of 60 % water-holding capacity (WHC) had significantly higher NH4+ flux than the same soil in its field moisture content (44 % WHC). Nitrogen pulse was detected in all soil samples as increased NH4+ flux after the N addition, followed by a subsequent decrease near to the initial level. In situ microdialysis sampling showed that the total amino acid fluxes were 5–15 nmol N cm-2 h-1 and they dominated the total diffusive N fluxes in Lapinjärvi and Kiikala. On average, the smallest share of the total free amino acids (54 %) was observed at the control plots of the logging residue experiment in Lapinjärvi. No correlation between the KCl-extractable NH4+-N concentration and the diffusive NH4+ flux was found, but instead the KCl-extractable NH4+-N concentration showed a significant positive correlation with the diffusive fluxes of both total free amino acid N and nitrate. Moreover, the diffusive NH4+ flux correlated positively with the net N mineralization rate. In general, ex situ microdialysis sampling showed 2–10 times higher amino acid fluxes and 10–20 times higher ammonium fluxes than the in situ microdialysis that reflects the effect of sampling, sample storage and preparation. The effect of soil moisture on the diffusive N fluxes could be further studied in laboratory experiments and in situ. The results of this study showed that the diffusive fluxes of different N forms are decoupled from the bulk soil concentrations. Moreover, microdialysis could be possibly used to quantify the transformation processes of N compounds in soil. These results increase the evidence that microdialysis has potential to detect temporal changes in N fluxes and possibly give new information about the ongoing processes at soil microsites.
  • Jokinen, Kari; Salovaara, Anna-Kaisa Johanna; Wasonga, Daniel; Edelmann, Minnamari; Simpura, Ilkka; Mäkelä, Pirjo (2022)
    Leafy vegetables like lettuce (Lactuca sativa L.) naturally have high nitrate content and the European Commission has set maximum level for nitrate in lettuce. Glycinebetaine is an organic osmolyte alleviating plant stress, but its role in leaf nitrate accumulation remains unknown. The uptake of glycinebetaine by lettuce roots, and its potential to regulate lettuce nitrate content and improve plant quality were investigated. Two hydroponic lettuce experiments were conducted with different glycinebetaine application rates (Exp1 : 0, 1, 7.5, and 15 mM; Exp2: 0, 1 + 1 + 1, 1 + 10, and 4 mM). Plants were analyzed at varying time points. Root application resulted in glycinebetaine uptake and translocation to the leaves. Glycinebetaine concentrations > 7.5 mM reduced leaf nitrate up to 40% and increased leaf dry matter content. Glycinebetaine showed a positive effect on leaf mineral and amino acid composition. Thus, glycinebetaine could be a novel strategy to reduce the nitrate content in hydroponic lettuce.
  • Lyhs, Ulrike; Björkroth, Johanna; Hyytiä, Eija; Korkeala, Hannu (Elsevier, 1998)
    The spoilage flora of vacuum-packaged, salted, cold-smoked rainbow trout fillets, with or without the addition of nitrate or nitrite, stored at 4°C and 8°C, was studied. Of 620 isolates, lactic acid bacteria were the major fraction (76%), predominating in all samples of spoiled product. However, the phenotypical tests used were insufficient to identify the lactic acid bacteria to the species level. Gram-positive, catalase-positive cocci, Gram-negative, oxidase-negative rods and Gram-negative, oxidase-positive rods were found in 6%, 16% and 2% of the samples, respectively. Of 39 Gram-positive, catalase-positive cocci, 29 were identified as staphylococci and 10 as micrococci. Eighty-five isolates were found to belong to the family Enterobacteriaceae, with 45 of those being Serratia plymuthica. Eleven isolates from the nitrate treated samples stored at 8°C were identified as Pseudomonas aeruginosa. The occurrence of P. aeruginosa and staphylococci in the nitrate-containing samples, stored at 8°C, may cause problems with respect to the safety of the product. The types of lactic acid and other bacteria in the spoilage flora were generally reduced by the addition of nitrate or nitrite to fillets.
  • Jaakkola, Sauli (Helsingfors universitet, 2013)
    Assessing and avoiding environmental impact of agriculture and forestry has become more and more important during recent years. In Finland, half of the phosphorus load and nearly 40 % of the nitrogen load in the water system is caused by agriculture and forestry. Traditionally water quality monitoring has been carried out with manual water sampling and laboratory analyses. The problem with manual sampling is low amount of samples. Continuously working water quality sensors have been used for a relatively short time, which is why continuous water quality monitoring needs more research. The objective of the study is to clarify the feasibility of optical sensors in monitoring water quality and nutrient loading in an agricultural and forest management area. The study was carried out in three monitoring stations of the Savijoki catchment in Southwest Finland. Two of the stations were identically equipped and were located in forested subcatchments. A third station was located at the Savijoki catchment discharge point, making it possible to study how sensors work in different water qualities. According to the study, monitoring with continuously working sensors will result in more accurate nutrient loading estimates. With sensors used in the study it is also possible to draw conclusions about dynamics between run-off and nutrient concentrations in water. A prerequisite for successful monitoring is utilizing the appropriate sensors in the correct location. For example, low nitrate levels in water in forested areas have to be taken into consideration when choosing sensors. During the monitoring it is important to actively keep track of the quality of data and to check that sensors are working properly. Water quality sensors always need good calibration and control water samples from the entire concentration range. Sensors also have to be equipped with an automatic cleaning mechanism.