| 1. |
- Pehme, Kaur-Mikk, et al.
(författare)
-
Field Study on the Efficiency of a Methane Degradation Layer Composed of Fine Fraction Soil from Landfill Mining
- 2020
-
Ingår i: Sustainability. - : MDPI. - 2071-1050. ; 12:15, s. 1-16
-
Tidskriftsartikel (refereegranskat)abstract
- The main components of landfill gas are methane and carbon dioxide. Emissions of methane, a strong greenhouse gas, can be minimized by in situ oxidation in the bioactive cover layer. Typically, organic-rich porous materials such as compost are used for this process. In this study, the material for a biocover was obtained from the same landfill by landfill mining. The objective was to study the spatial distribution of gases and the efficiency of methane degradation in the biocover. The methane and carbon dioxide emissions were measured at 29 measuring points six times on the surface and once at a depth of 0.5 m. The highest values of both gases from the surface were recorded in July 2015: 1.0% for CO(2)and 2.1% for CH4. Deeper in the cover layer, higher values of methane concentration were recorded. The results showed that (a) methane from the waste deposit was entering the biocover, (b) the migration of methane to the atmosphere was low, (c) fluctuations in the composition of gases are seasonal, and (d) the trend in the concentration of CH(4)over time was an overall decrease. The described cover design reduces the CH(4)emissions in landfills using elements of circular economy-instead of wasting natural soils and synthetic liners for the construction of the final cover layer, functional waste-derived materials can be used.
|
|
| 2. |
|
|
| 3. |
- Burlakovs, Juris, 1977-, et al.
(författare)
-
Environmental Quality of Groundwater in Contaminated Areas—Challenges in Eastern Baltic Region
- 2020
-
Ingår i: Water Resources Quality and Management in Baltic Sea Countries. - Switzerland : Springer. - 9783030397005 - 9783030397012 ; , s. 59-84
-
Bokkapitel (refereegranskat)abstract
- The lack of water in the future will force society to find more sophisticated solutions for treatment and improvement of groundwater wherever it comes from. Contamination of soil and groundwater is a legacy of modern society, prevention of contaminants spread and secondary water reuse options shall be considered. The aim of the book chapter is to give oversight view on problems and challenges linked to groundwater quality in Eastern Baltic region whilst through case studies explaining the practical problems with groundwater monitoring, remediation and overall environmental quality analysis. The reader will get introduced with case studies in industry levels as credibility of scientific fundamentals is higher when practical solutions are shown. Eastern Baltic countries experience cover contamination problems that are mainly of historic origin due to former Soviet military and industrial policy implementation through decades. Short summaries for each case study are given and main conclusions provided in form of recommendations at the very end of the chapter.
|
|
| 4. |
- Burlakovs, Juris, 1977-, et al.
(författare)
-
Platinum Group Elements in Geosphere and Anthroposphere : Interplay among the Global Reserves, Urban Ores, Markets and Circular Economy
- 2020
-
Ingår i: Minerals. - : MDPI. - 2075-163X. ; 10:6, s. 1-19
-
Forskningsöversikt (refereegranskat)abstract
- Industrial and strategic significance of platinum group elements (PGEs)-Os, Ir, Ru, Rh, Pd, Pt-makes them irreplaceable; furthermore, some PGEs are used by investors as "safe heaven" assets traded in the commodity markets. This review analyzes PGEs from various aspects: their place in the geosphere, destiny in the anthroposphere, and opportunity in the economy considering interactions among the exploration, recycling of urban ores, trade markets, speculative rhetoric, and changes required for successful technological progress towards the implementation of sustainability. The global market of PGEs is driven by several concerns: costs for extraction/recycling; logistics; the demand of industries; policies of waste management. Diversity of application and specific chemical properties, as well as improper waste management, make the recycling of PGEs complicated. The processing approach depends on composition and the amount of available waste material, and so therefore urban ores are a significant source of PGEs, especially when the supply of elements is limited by geopolitical or market tensions. Recycling potential of urban ores is particularly important in a long-term view disregarding short-term economic fluctuations, and it should influence investment flows in the advancement of innovation.
|
|
| 5. |
- Ghazzali, Mohamed I D M, 1974, et al.
(författare)
-
Synthesis, EPR and DFT calculations of rare Ag(II)porphyrins and the crystal structure of [Zn(II)tetrakis(4-bromo-2-thiophene)porphyrin]
- 2008
-
Ingår i: Inorganic Chemistry Communication. - : Elsevier BV. - 1387-7003 .- 1879-0259. ; 11:9, s. 1019-1022
-
Tidskriftsartikel (refereegranskat)abstract
- Meso-tetrakis (4-bromo-2-thiophene) and (5-bromo-2-thiophene) porphyrins were synthesized in 18% yield from freshly distilled pyrrole and the corresponding aldehydes in refluxing propionic acid. Reaction of both porphyrins with either Zn(OAc) 2 · 2H 2 O or Ag(OAc) afforded the corresponding metal complexes in 20% yield. The free bases and metal complexes were characterized by IR, NMR, EPR, MS and XPS. The crystal structure of 5,10,15,20(4-bromo-2-thiophene)porphyrinato Zn(II) was determined by X-ray diffraction and shows a 'zigzag-like' packing pattern due to S···S intermolecular interaction. Structural features of these molecules are discussed by DFT quantum chemical calculations. © 2008 Elsevier B.V. All rights reserved.
|
|
| 6. |
- Gilbert, M. Thomas P., et al.
(författare)
-
Paleo-Eskimo mtDNA genome reveals matrilineal discontinuity in Greenland
- 2008
-
Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 320:5884, s. 1787-1789
-
Tidskriftsartikel (refereegranskat)abstract
- The Paleo- Eskimo Saqqaq and Independence I cultures, documented from archaeological remains in Northern Canada and Greenland, represent the earliest human expansion into the New World's northern extremes. However, their origin and genetic relationship to later cultures are unknown. We sequenced a mitochondrial genome from a Paleo- Eskimo human by using 3400- to 4500- year- old frozen hair excavated from an early Greenlandic Saqqaq settlement. The sample is distinct from modern Native Americans and Neo- Eskimos, falling within haplogroup D2a1, a group previously observed among modern Aleuts and Siberian Sireniki Yuit. This result suggests that the earliest migrants into the New World's northern extremes derived from populations in the Bering Sea area and were not directly related to Native Americans or the later Neo- Eskimos that replaced them.
|
|
| 7. |
|
|
| 8. |
- Osadchuk, Irina, et al.
(författare)
-
Reduced State of Iridium PCP Pincer Complexes in Electrochemical CO2 Hydrogenation
- 2016
-
Ingår i: ACS Catalysis. - : American Chemical Society (ACS). - 2155-5435 .- 2155-5435. ; 6:6, s. 3834-3839
-
Tidskriftsartikel (refereegranskat)abstract
- We present a computational study on the mechanism for electrochemical reduction of CO2 using a PCP pincer iridium(III) dihydride complex. Our results point toward a mechanism that involves an in situ-generated iridium(I) hydride as the active species for the CO2 to formate reduction. The iridium(III) path can operate in parallel but is associated with higher activation free energies in the reaction between the metal hydride and CO2, compared to the reaction at the in situ-generated iridium(I) species.
|
|
| 9. |
- Osadchuk, Irina, et al.
(författare)
-
Theoretical Investigation of a Parallel Catalytic Cycle in CO2 Hydrogenation by (PNP)IrH3
- 2015
-
Ingår i: Organometallics. - : American Chemical Society (ACS). - 0276-7333 .- 1520-6041. ; 34:20, s. 4932-4940
-
Tidskriftsartikel (refereegranskat)abstract
- The (PNP)IrH3 (2,6-bis(diisopropylphosp-hinomethyl)pyridine iridium trihydride) complex by Nozaki is a highly active and selective catalyst for CO2 hydrogenation to formic acid in aqueous KOH. Previous theoretical investigations found that regeneration of the catalyst is the rate-determining step in this reaction. In the current article we present results from a computational study using density func- theory in order to consider the possibility of sequential insertion of two CO2 molecules in two Ir-H bonds before the reaction with hydrogen. We found that insertion of a second CO2 molecule is indeed possible; moreover, this sequential insertion allows formation of a more electrophilic iridium mono-hydride intermediate, and thereby the process of H-2 cleavage is facilitated. In addition, we considered the influence of ligands coplanar with the PNP ligand on the energy of CO2 insertion into the (PNP)IrH2X complex and found that sigma- and pi-donating ligands promote the reaction.
|
|
| 10. |
- Pehme, Kaur-Mikk, et al.
(författare)
-
Urban hydrology research fundamentals for waste management practices
- 2019
-
Ingår i: 25<sup>th</sup> Annual International Scientific Conference "Research for Rural Development 2019" 15 - 17 May, 2019, vol 1. - Jelgava : Latvia University of Life Sciences and Technologies. ; , s. 160-167
-
Konferensbidrag (refereegranskat)abstract
- The urbanization and increasing growth of planet’s population accumulates significant volume of disposed wasteas well as increases risks on human health and environmental safety. Landfill systems are the dynamic, livingin space and time, potentially harmful entities that must be managed in as careful and smart way as possible.There are many studies related to landfill emissions such as leachates and methane. However, there is a need foradvanced understanding of landfill hydrological regime and risks related to climate change and associated changesof hydrological cycle. The comprehensive studies about the urban hydrology are available; however, applicationto landfill management is fragmentary and inconsistent in several aspects. Landfill in long term has an impact onhydrological cycle. The heterogeneous land surface is one of aspects; however, there are still unanswered questionsabout the urban environment impact on water balance components. The aim of this study is to describe fundamentalsof landfill hydrology in urban hydrological response unit context as well as evaluate the potential risks to environmentand human health related to landfill geomorphology and hydrological balance in temporal climate conditions. Thelandfill hydrological cycle has similarities with urban hydrological cycle; however, there are additional componentsrelated to landfill specification, e.g., irrigation or leachate recirculation as well as total produced leachate.
|
|
