12 research outputs found
Normative Mineralogy of 1170 Soil Profiles across Canada
Weathering of soil minerals provides base cations that buffer against acidity, and nutrients that support plant growth. In general, direct observations of soil minerals are rare; however, their abundance can be determined indirectly through soil geochemistry using normative-calculation procedures. This study compiled a data set of major oxide content from published and archived soil geochemical observations for 1170 sites across Canada (averaged over the soil profile [A, B, and C horizons], weighted by depth and bulk density to a maximum depth of 50 cm). Quantitative soil mineralogy (wt%) was systematically determined at each site using the normative method, ‘Analysis to Mineralogy’ (A2M); the efficacy of the approach was evaluated by comparison to X-ray Diffraction (XRD) mineralogy available for a subset of the study sites. At these sites, predicted A2M mineralogy was significantly related to estimated XRD, showing a strong linear relationship for plagioclase, quartz, and K-feldspar, and a moderate linear relationship for chlorite and muscovite. Further, the predicted A2M plagioclase content was almost identical to the estimated XRD soil mineralogy, showing no statistical difference. The Canada-wide predicted quantitative soil mineralogy was consistent with the underlying bedrock geology, such as in north-western Saskatchewan and north-eastern Alberta, which had high amounts of quartz due to the Western Canadian Sedimentary Basin. Other soil minerals (plagioclase, potassium feldspar, chlorite, and muscovite) varied greatly in response to changing bedrock geology across Canada. Normative approaches, such as A2M, provide a reliable approach for national-scale determination of quantitative soil mineralogy, which is essential for the assessment of soil weathering rates
From minerals to trees: Reducing uncertainty in estimating weathering rates for sustainable forest growth
Sustainable forest growth is fundamentally dependent on long-term supply of nutrients from mineral dissolution. Over the past century, losses of base cations (Ca, K, Mg, Na) from forest soils have been accelerated through increased forest production and anthropogenic acidification. Substantial uncertainties about the accuracy in weathering rate estimates has hampered designation of appropriate levels for maintaining sustainable forest production. The aim of this thesis was to improve the accuracy of estimates by using better mineralogical data inputs to a frequently applied weathering estimation model (PROFILE) and by comparing weathering rates derived from three different methods that differ conceptually, based on harmonised input data and boundary conditions. A new site-specific approach for calculating indirect quantitative soil mineralogy with the “Analysis to Mineralogy” (‘A2M’) model was developed, by direct determination of the mineralogical input data to A2M. Overall, A2M-derived quantitative mineralogy reproduced the main pattern of “reference” mineral contents (measured directly by X-ray powder diffraction (XRPD)). An exception to this was observed for major K-bearing minerals in the regional quantitative A2M mineralogy. Regardless of these observed discrepancies, PROFILE weathering estimates were uncertain irrespective of the type of mineralogical input data that was used. For Ca and Mg, uncertainties arose from lack of knowledge about presence or absence of specific minerals characterised by high dissolution rates (i.e. apatite, amphibole, pyroxene, calcite and illite). For K and Na, uncertainties related to use of inaccurate dissolution rate coefficients for dioctahedral mica and plagioclase. Overall, the PROFILE model and the depletion method were shown to estimate present-day and long-term weathering rates of Ca and Mg with reasonable accuracy. Comparisons of weathering rates in a base cation budget showed that trees take up base cations from forest soils, at least when growing intensively, probably from sources other than weathering
Pedon-scale silicate weathering : comparison of the PROFILE model and the depletion method at 16 forest sites in Sweden
Weathering of soil minerals is important for the recovery from acidification and for the sustainability of forestry. However, there is still substantial uncertainty about its absolute rate. This study presents a harmonized comparison of field weathering rates estimated with the mechanistic model PROFILE and the depletion method for 16 intensively sampled soil profiles across Sweden representing different site conditions. In general, a correspondence in total weathering rates was found between the two methods except in rare cases where either method yielded deviating results. The weathering rate was higher according to the depletion method than according to PROFILE for Mg, while PROFILE produced higher weathering rates for the other base cations. The Spearman rank correlation (rho) between the two methods indicated significant correlation for Ca (rho = 0.44, p = 0.04) and non-significant correlation for Mg (rho = 0.51, p = 0.09), Na (rho = 0.25, p = 0.34), K (rho = 0.07, p = 0.80), and the sum of the base cations (rho = 0.11, p = 0.67). The variation in weathering rates with depth showed opposite gradients in the upper 50 cm, which reflects the conceptual differences between the methods. This study shows the potential of using multiple methods to identify a probable weathering rate, if harmonized input data are used. Furthermore, it highlights the importance of making comparisons for individual elements in order to interpret differences between methods. Regardless of the method used, weathering rates were below or at the same level as the losses caused by whole-tree harvesting, particularly in southern Sweden, indicating a risk of negative effects on soils and waters. (C) 2013 Elsevier B.V. All rights reserved
Assessing the impact of acid rain and forest harvest intensity with the HD-MINTEQ model – soil chemistry of three Swedish conifer sites from 1880 to 2080
Forest soils are susceptible to anthropogenic acidification. In the past,
acid rain was a major contributor to soil acidification, but, now that
atmospheric levels of S have dramatically declined, concern has
shifted towards biomass-induced acidification, i.e. decreasing soil solution
pH due to tree growth and harvesting events that permanently remove base
cations (BCs) from forest stands. We use a novel dynamic model, HD-MINTEQ (Husby Dynamic MINTEQ), to
investigate possible long-term impacts of two theoretical future harvesting
scenarios in the year 2020, a conventional harvest (CH, which removes stems
only), and a whole-tree harvest (WTH, which removes 100 % of the
above-ground biomass except for stumps) on soil chemistry and weathering
rates at three different Swedish forest sites (Aneboda, Gårdsjön, and
Kindla). Furthermore, acidification following the harvesting events is
compared to the historical acidification that took place during the 20th century
due to acid rain. Our results show that historical acidification due
to acid rain had a larger impact on pore water chemistry and mineral
weathering than tree growth and harvesting, at least if nitrification
remained at a low level. However, compared to a no-harvest baseline, WTH and
CH significantly impacted soil chemistry. Directly after a harvesting event
(CH or WTH), the soil solution pH sharply increased for 5 to 10 years before
slowly declining over the remainder of the simulation (until year 2080). WTH
acidified soils slightly more than CH, but in certain soil horizons there
was practically no difference by the year 2080. Even though the pH in the WTH
and CH scenario decreased with time as compared to the no-harvest scenario
(NH), they did not drop to the levels observed around the peak of historic
acidification (1980–1990), indicating that the pH decrease due to tree growth
and harvesting would be less impactful than that of historic atmospheric
acidification. Weathering rates differed across locations and horizons in
response to historic acidification. In general, the predicted changes in
weathering rates were very small, which can be explained by the net effect of
decreased pH and increased Al3+, which affected the weathering rate in
opposite ways. Similarly, weathering rates after the harvesting scenarios in
2020 remained largely unchanged according to the model.</p
Storm disturbances in a Swedish forest-A case study comparing monitoring and modelling
A Norway spruce (Picea abies Karst) forest site in southwest Sweden was chosen to study the effects of storm disturbances over the period 1997-2009, during which two storms, 'Lothar' (December 1999) and 'Gudrun' (January 2005), affected the area. Monitored deposition data, soil water chemistry data and forest inventory data were compared with the predictions of an integrated ecosystem model, ForSAFE, in an effort to reveal and understand the effects of storms on acidification/recovery in forest soils. Both storms caused windthrow loss leading to increased nitrate and sulphate concentrations in soil water as a result of stimulated mineralization. Lothar led to increased concentrations of Na+, Mg2+, and Cl- in soil water due to sea-salt episode. No general sea-salt episode was seen following Gudrun, but small sea-salt episodes were observed in 2007 and 2008. Each sea-salt episode caused a temporary decrease of pH, and a subsequent recovery, but overall, the soil water pH decreased from 4.54 to 3.86 after Lothar. Modelling suggested that the site was recovering from acidification from 1990s, and would continue to recover in future. Both modelled and monitored data showed that storm caused disturbances in the recovery; monitored data even suggested that soil acidification happened due to storm disturbances. Sea-salt episode does not increase soil acidity in the long term, and will probably decrease the soil acidity by replenishing the base saturation. The modelled data also suggested that storms with only windthrow would not have effects on soil acidification recovery in the long term, but they may influence the soil fertility by losses of base cations. (C) 2015 Elsevier B.V. All rights reserved
Dynamic modelling of weathering rates – the benefit over steady-state modelling
Weathering rates
are of considerable importance in estimating the acidification sensitivity
and recovery capacity of soil and are thus important in the assessment of the
sustainability of forestry in a time of changing climate and growing demands
for forestry products. In this study, we modelled rates of weathering in
mineral soil at two forested sites in southern Sweden included in a
monitoring network, using two models. The aims were to determine whether the
dynamic model ForSAFE gives comparable weathering rates to the steady-state
model PROFILE and whether the ForSAFE model provided believable and useful
extra information on the response of weathering to changes in acidification
load, climate change and land use.
The average weathering rates calculated with ForSAFE were very similar to
those calculated with PROFILE for the two modelled sites. The differences
between the models regarding the weathering of certain soil layers seemed to
be due mainly to differences in calculated soil moisture. The weathering
rates provided by ForSAFE vary seasonally with temperature and soil
moisture, as well as on longer timescales, depending on environmental
changes. Long-term variations due to environmental changes can be seen in
the ForSAFE results, for example, the weathering of silicate minerals is
suppressed under acidified conditions due to elevated aluminium
concentration in the soil, whereas the weathering of apatite is accelerated
by acidification. The weathering of both silicates and apatite is predicted
to be enhanced by increasing temperature during the 21st century. In this
part of southern Sweden, yearly precipitation is assumed to be similar to
today's level during the next forest rotation, but with more precipitation
in winter and spring and less in summer, which leads to somewhat drier soils
in summer but still with increased weathering. In parts of Sweden with a bigger
projected decrease in soil moisture, weathering might not increase despite
increasing temperature.
These results show that the dynamic ForSAFE model can be used for weathering
rate calculations and that it gives average results comparable to those from
the PROFILE model. However, dynamic modelling provides extra information on
the variation in weathering rates with time and offers much better
possibilities for scenario modelling.</p
Study of Mobile Robot Operations Related to Lunar Exploration
Mobile robots extend the reach of exploration in environments unsuitable, or unreachable, by humans. Far-reaching environments, such as the south lunar pole, exhibit lighting conditions that are challenging for optical imagery required for mobile robot navigation. Terrain conditions also impact the operation of mobile robots; distinguishing terrain types prior to physical contact can improve hazard avoidance.
This thesis presents the conclusions of a trade-off that uses the results from two studies related to operating mobile robots at the lunar south pole. The lunar south pole presents engineering design challenges for both tele-operation and lidar-based autonomous navigation in the context of a near-term, low-cost, short-duration lunar prospecting mission. The conclusion is that direct-drive tele-operation may result in improved science data return.
The first study is on demonstrating lidar reflectance intensity, and near-infrared spectroscopy, can improve terrain classification over optical imagery alone. Two classification techniques, Naive Bayes and multi-class SVM, were compared for classification errors. Eight terrain types, including aggregate, loose sand and compacted sand, are classified using wavelet-transformed optical images, and statistical values of lidar reflectance intensity. The addition of lidar reflectance intensity was shown to reduce classification errors for both classifiers. Four types of aggregate material are classified using statistical values of spectral reflectance. The addition of spectral reflectance was shown to reduce classification errors for both classifiers.
The second study is on human performance in tele-operating a mobile robot over time-delay and in lighting conditions analogous to the south lunar pole. Round-trip time delay between operator and mobile robot leads to an increase in time to turn the mobile robot around obstacles or corners as operators tend to implement a `wait and see\u27 approach. A study on completion time for a cornering task through varying corridor widths shows that time-delayed performance fits a previously established cornering law, and that varying lighting conditions did not adversely affect human performance. The results of the cornering law are interpreted to quantify the additional time required to negotiate a corner under differing conditions, and this increase in time can be interpreted to be predictive when operating a mobile robot through a driving circuit
Behavior of fluids in clay-hosted nanopores: insights from molecular dynamics
Our understanding of fluid behavior and transport in shales, especially in organic or kerogen pore systems, has grown rapidly over the last few years. Yet, given the prevalence of inorganic material that often hosts the organics in shales, little attention has been devoted to how fluids move and distribute themselves in clay-hosted pores. In this work, I use classical molecular dynamics simulations to investigate fluid behavior and transport in charged clay-hosted nanopores. I focus on mixtures of brines and hydrocarbon confined in clay slit pores and consider two different surface charges. A very important constraint I impose on the models is rigidity to avoid clay swelling behavior. My initial set of simulations focuses on oil-solvent mixtures in clay pores and the conditions under which they become miscible, and the impact of confinement on the self-diffusion of hydrocarbon as well as viscosity. At specific pore widths and water saturations, water is shown to bridge across the pore from one clay surface to the other, and not merely be adsorbed. My work discusses the conditions under which these bridges form and their impact on fluid movement. I show that increasing brine salinities can dissipate the water bridges which motivates me to discuss optimizing salinity for waterfloods or hydraulic fracturing fluids when clays are predominant. The final discussion is the effect of varying salinity on the shape and stability of surfactant-solvent microemulsions in clay pores
Molecular phylogeny of Archaea in boreal forest soil, freshwater and temperate estuarine sediment
Suurin osa luonnossa havaitsemistamme mikrobeista on sellaisia, joita emme edelleenkään osaa kasvattaa laboratorio-oloissa, vaikka tietomme mikrobien monimuotoisuudesta paranevat koko ajan. Luonnontilaisen mikrobieliöstön kokoonpano eri ympäristöissä on paljolti epäselvä ja ymmärrämme vielä hyvin puutteellisesti mikrobien ekologiaa ja niiden rooleja eliöyhteisöissä. Nykyaikaiset molekulaariset tutkimusmenetelmät auttavat selvittämään mikrobien monimuotoisuutta kokonaisvaltaisesti ja nopeasti. Ympäristöstä kemiallisesti puhdistetut ribosomaalista RNA:ta koodaavat geenit edustavat periaatteessa kaikkia eliöyhteisön geneettisesti toisistaan poikkeavia eliöitä. Niistä voidaan valikoida halutut genomit jatkotutkimuksia varten.
Uusien menetelmien käyttö on tuonut esiin sen merkittävän seikan, että "tavanomaisten" elinympäristöjen eliöyhteisöihin kuuluu suuri joukko entuudestaan tuntemattomia arkkieliöitä. Aiemmin kuviteltiin, että arkkieliöt asuttavat vain sellaisia "epätavallisia" tai "äärimmäisiä" elinympäristöjä, joita luonnehtii joku seuraavista ominaisuuksista: hyvin korkea lämpötila, korkea suolapitoisuus, korkea happamuus tai emäksisyys, hapettomuus. Tutkijat ovat viimeisen noin kymmenen vuoden aikana osoittaneet, että arkkieliöt asuttavat hyvin monenlaisia kylmän ja lauhkean vyöhykkeen ympäristöjä, yhtä hyvin maaperää kuin suolaisen ja makean veden pohjaa tai pintakerroksia. Nämä löydöt ovat avanneet uuden alun arkkieliöiden tutkimukselle, erityisesti sen selvittämiselle, mitkä ovat niiden fysiologiset ja ekologiset roolit monimuotoisissa mikrobiyhteisöissä.
Tämä väitöskirja kuvaa entuudestaan tuntemattomien arkkieliöiden löytymistä havumetsävyöhykkeen metsämaasta.
Arkkieliöitä löytyi myös lauhkean vyöhykkeen vuorovesialueelta, murtoveden huuhtelemasta pohjasta. Nämä löydöt ovat perustavalaatuisia vuorovesialueen eliöyhteisöjen ymmärtämiseksi.
Suomalaisen metsäjärven vedestä määritettiin molempien arkkieliöiden pääryhmien - tieteellisiltä nimiltään Crenarchaeota ja Euryarchaeota - edustajia. Euryarchaeota-ryhmän edustajia voitiin havainnoida myös fluoresenssi-mikroskopoinnilla. Löydöt viittaavat siihen, että arkkieliöillä on oma biogeokemiallinen roolinsa makeanveden ravintoketjujen hiilen käytössä.
Tässä työssä määritetyt uudet arkkieliöiden genomien nukleotidisekvenssit on toimitettu ARB-tietokantaan, jonka kasvava vertailuaineisto edelleen parantaa uusien arkkieliösekvenssien analyysiä ja auttaa hybridisaatiokoetinten ja polymeraasiketjureaktioalukkeiden suunnittelussa ja arvioinnissa.
Tässä väitöskirjassa esitellyt tulokset yhdessä lukuisien vesi-, maaperä- ja muiden ympäristöjen arkkieliöitä käsittelevien julkaisujen kanssa osoittavat, että arkkieliöt asuttavat monia erilaisia elinympäristöjä ja että ne ovat ekologisesti paljon menestyneempiä, kuin tieteenalalla on kuviteltu. Voimme olettaa, että heti kun joitain näistä eliöistä onnistutaan kasvattamaan ja ylläpitämään laboratorio-oloissa, niiden joukosta löydetään aivan uusia, entuudestaan tuntemattomia fysiologisia fenotyyppejä, jotka avaavat mielenkiintoisia näkymiä aineenvaihdunnan ja perinnöllisten ominaisuuksien tutkimukselle