SCR-katalysaattorin ammoniakkilatauksen LQG-säätö

SCR-järjestelmä (engl. Selective Catalytic Reduction, selektiivinen katalyyttinen pelkistyminen) on dieselmoottorin pakokaasun jälkikäsittelyjärjestelmä, jonka avulla dieselmoottorin tuottamia typen oksidien (NOx) päästöjä voidaan vähentää. Tiukentuvien päästölainsäädännön asettamien rajojen vuoksi SCR-järjestelmältä vaaditaan tulevaisuudessa entistä parempaa tehokkuutta. Suunnitteilla olevassa työkoneiden Tier 5 -päästöstandardissa typen oksidien rajaksi ehdotetaan 0,04 g/kWh, joka on 90 % nykyistä 0,4 g/kWh rajaa pienempi. Käytännössä tiukentuva päästöraja tarkoittaa, että SCR-järjestelmältä vaaditaan lähes täydellistä NOx-konversiota järjestelmän ollessa toiminta-alueellaan. Tässä työssä suunnitellaan SCR-järjestelmän urearuiskutuksen takaisinkytketty säätö. Urea hajoaa pakokaasussa ammoniakiksi, joka pelkistää typen oksidit SCR-katalysaattorissa. Järjestelmän NOx-konversiota hallitaan syötetyn urean ruiskutusmäärää ohjaamalla. Tavoitteena on ylläpitää mahdollisimman suuri NOx-konversio ilman liian suurta ammoniakkipäästöä. Tavoitteen saavuttamiseksi suunnitellaan katalysaattoriin varastoituneen ammoniakin eli ammoniakkilatauksen hallintaan perustuva, vahvistusskeduloitu LQG-säädin (engl. Linear Quadratic Gaussian). Katalysaattorin ammoniakkilatauksen estimoimiseksi suunnitellaan katalysaattorin keskelle sijoitetun ammoniakkianturin mittausta hyödyntävä laajennettu Kalman-suodin. Suunnitellun säätöjärjestelmän suorituskyky validoitiin moottoridynamometrillä suoritetuilla käytännön kokeilla. Järjestelmällä saavutettiin erittäin matala NOx-päästötaso, NOx-konversion ollessa lähes täydellinen SCR-järjestelmän ollessa toiminta-alueella. Tyyppihyväksynnässä käytettävässä NRTC-testisyklissä NOx-päästökertoimeksi mitattiin 0,011 g/kWh kuumakäynnistyksenä ajetussa syklissä. Suurin mitattu katalysaattorin jälkeinen ammoniakkipitoisuus oli 8,61 ppm, joka syntyi moottorin kuormannostotilanteesta johtuvan katalysaattorin lämpötilan nopean nousun aikana

Water quality and the biodegradability of dissolved organic carbon in drained boreal peatland under different forest harvesting intensities

Boreal peatiands are major sources of nitrogen (N), phosphorus (P) and dissolved organic carbon (DOC) to downstream aquatic ecosystems, and forest harvesting generally further increases the loading of DOC and nutrients. Continuous cover forestry (CCF) is proposed to be an environmentally more sustainable management option for peatland forests than conventional even-aged clear-cutting. However, the impacts of CCF on water quality, the biodegradability of DOC and consequent CO2 emissions from inland waters are poorly known. We studied the concentrations of N, P and DOC, the quality of DOC, and the mineralization of DOC to CO2 in ground water and ditch water in clear-cut, partially harvested, i.e. CCF, and uncut drained forests in Finland. Groundwater total N, NH4-N and PO4-P concentrations were significantly lower in CCF and uncut forest than in the clear-cut forest. Groundwater DOC concentrations were often highest in the clear-cut forest, where the water table was doser to the soil surface. Ditch water DOC and N concentrations were lowest next to the clear-cut area. DOC aromaticity in ground water was higher in the uncut forest than in the clear-cut and CCF, whereas ditch water aromaticity did not differ between the treatments. The biodegradation of DOC was studied by incubating water (at 15 degrees C for 24 h) 1, 3, 7 and 21 days after sampling. The results indicated that the majority of the CO2 production took place during the first three days, and CO2 fluxes were considerably higher from the ditch water than from the groundwater. The CO2 emissions were lower in summer than in the other seasons. Ditch water and groundwater CO2 production were generally significantly higher in the clear-cut than in the uncut forest. The results suggest that CCF can decrease the nutrient concentrations as well as CO2 emissions from inland waters compared to conventional clear-cutting. (C) 2021 The Authors. Published by Elsevier B.V.Peer reviewe

Healthy eaters beat unhealthy eaters in prototype evaluation among men, but abstinence may pose a risk for social standing

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Replacing centralised waste and sanitation infrastructure with local treatment and nutrient recycling : Expert opinions in the context of urban planning

© . This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0

Impact of Forest Harvesting Intensity and Water Table on Biodegradability of Dissolved Organic Carbon in Boreal Peat in an Incubation Experiment

Boreal peatlands are vast carbon (C) stores but also major sources of dissolved organic C (DOC) and nutrients to surface waters. Drainage and forest harvesting accelerates DOC leaching. Continuous cover forestry (CCF) is considered to cause fewer adverse environmental effects. Yet, the effects of CCF on DOC processes are unrecognised. We study DOC production and quality in unharvested, CCF, and clear-cut drained peatland forests and in a non-forested alluvial sedge fen. Parallel replicate peat columns with ground vegetation are collected from the uppermost 50 cm at each site, and the water table (WT) is set to -20 or -40 cm depths on the columns. During the eight-month ex situ incubation experiment, the soil water samples are extracted monthly or bi-monthly. The samples are incubated at 15 degrees C for multiple 72 h incubation cycles to study pore water quality and biodegradation of DOC. The CO2 production occurs during the first three days. The DOC concentrations and the CO2 release per volume of water are significantly lower in the sedge fen than in the drained peatland forests. The WT has a negligible effect on DOC concentrations and no effect on DOC quality, but the higher WT has generally higher CO2 production per DOC than the lower WT. The results suggest that peat in the drained peatlands is not vulnerable to changes per se but that forest management alters biotic and abiotic factors that control the production, transport, and biodegradation of DOC.Peer reviewe

Impact of Forest Harvesting Intensity and Water Table on Biodegradability of Dissolved Organic Carbon in Boreal Peat in an Incubation Experiment

Boreal peatlands are vast carbon (C) stores but also major sources of dissolved organic C (DOC) and nutrients to surface waters. Drainage and forest harvesting accelerates DOC leaching. Continuous cover forestry (CCF) is considered to cause fewer adverse environmental effects. Yet, the effects of CCF on DOC processes are unrecognised. We study DOC production and quality in unharvested, CCF, and clear-cut drained peatland forests and in a non-forested alluvial sedge fen. Parallel replicate peat columns with ground vegetation are collected from the uppermost 50 cm at each site, and the water table (WT) is set to −20 or −40 cm depths on the columns. During the eight-month ex situ incubation experiment, the soil water samples are extracted monthly or bi-monthly. The samples are incubated at 15 °C for multiple 72 h incubation cycles to study pore water quality and biodegradation of DOC. The CO2 production occurs during the first three days. The DOC concentrations and the CO2 release per volume of water are significantly lower in the sedge fen than in the drained peatland forests. The WT has a negligible effect on DOC concentrations and no effect on DOC quality, but the higher WT has generally higher CO2 production per DOC than the lower WT. The results suggest that peat in the drained peatlands is not vulnerable to changes per se but that forest management alters biotic and abiotic factors that control the production, transport, and biodegradation of DOC

Impact of Forest Harvesting Intensity and Water Table on Biodegradability of Dissolved Organic Carbon in Boreal Peat in an Incubation Experiment

Boreal peatlands are vast carbon (C) stores but also major sources of dissolved organic C (DOC) and nutrients to surface waters. Drainage and forest harvesting accelerates DOC leaching. Continuous cover forestry (CCF) is considered to cause fewer adverse environmental effects. Yet, the effects of CCF on DOC processes are unrecognised. We study DOC production and quality in unharvested, CCF, and clear-cut drained peatland forests and in a non-forested alluvial sedge fen. Parallel replicate peat columns with ground vegetation are collected from the uppermost 50 cm at each site, and the water table (WT) is set to −20 or −40 cm depths on the columns. During the eight-month ex situ incubation experiment, the soil water samples are extracted monthly or bi-monthly. The samples are incubated at 15 °C for multiple 72 h incubation cycles to study pore water quality and biodegradation of DOC. The CO2 production occurs during the first three days. The DOC concentrations and the CO2 release per volume of water are significantly lower in the sedge fen than in the drained peatland forests. The WT has a negligible effect on DOC concentrations and no effect on DOC quality, but the higher WT has generally higher CO2 production per DOC than the lower WT. The results suggest that peat in the drained peatlands is not vulnerable to changes per se but that forest management alters biotic and abiotic factors that control the production, transport, and biodegradation of DOC

Contamination by Norovirus and Adenovirus on Environmental Surfaces and in Hands of Conscripts in Two Finnish Garrisons

This study investigated the presence of norovirus and adenovirus, especially enteric adenovirus, on the environmental surfaces (n = 481) and military conscripts' hands (n = 109) in two Finnish garrisons (A and B) in 2013 and 2014. A questionnaire study was conducted to reveal possible correlations between viral findings on the conscripts' hands and their acute gastroenteritis symptoms. In addition to the swab samples, 14 fecal samples were obtained for viral analysis. In total, norovirus was present in 9.0 % of the surface swabs in 2013, whereas enteric adenovirus was present in 0.0 % and non-enteric adenovirus in 9.4 %. In the same year, 2.6 % of the hand swabs contained norovirus, 2.6 % enteric adenovirus, and 40.3 % non-enteric adenovirus. Norovirus GI.6 was continually detected on the surfaces of garrison A, and identical virus was detected in some of the fecal samples. In garrison B, two slightly different norovirus GII.4 strains were present on the surfaces. The questionnaires revealed no recent acute gastroenteritis cases in garrison A, but in garrison B, where the norovirus-positive hand swabs were collected, 30.6 % of the conscripts reported of recent symptoms. In 2014, norovirus was rarely detected, but adenovirus was again frequently present, both on the surfaces and hands. Taken together, our results suggest that gastroenteritis outbreaks occurred in 2013, but not in 2014. Due to the low number of hand swabs positive for enteric viruses, no conclusions about associations between viral findings and gastroenteritis symptoms could be drawn. This study increased our understanding of the possible transmission of viruses via contaminated environment and hands.Peer reviewe