Latvian Environment, Geology and Meteorology Centre (Latvia)

The first record of Atrichops crassipes (Meigen, 1920) (Diptera, Athericidae) in Latvia is reported, together with additional findings from Lithuanian waters in 2015. The data are based on larval records collected during freshwater macroinvertebrate research and water‑quality monitoring. Atrichops crassipes represents a new Diptera species record for Latvia and marks the northernmost limit of the species known range. Our data suggest that A. crassipes is expanding its range northward, possibly driven by climate warming.

Main textIn order to validate the participants' calibration measurement capabilities (CMCs) and to provide a basis for the submission of reviewed or new CMCs for National Metrology Institutes of member countries of the "Comité International des Poids et Mesures" (CIPM), supplementary comparisons of mass standards have been carried out under the auspices of the EURAMET. This is a comparison of the 20kg stainless steel mass standard. The aim of this supplementary comparison was to compare the results obtained by NMIs in the calibration of 20kg stainless steel weights. BEV, Austria was the pilot laboratory. Measurements were performed between 15 May 2022 and 28 June 2024. The data analysis was carried out by Dr Lars Nielsen (DFM). The participants' results were in agreement with the comparison reference value except one laboratory (SMU, Slovakia), after two laboratories updated their values.To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database https://www.bipm.org/kcdb/.The final report has been peer-reviewed and approved for publication by the CCM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

Producers and processors of agricultural raw materials are faced with the task of increasing the competitiveness of their products and added value. One of the solutions to these problems is to increase the depth of processing raw materials by agricultural producers or primary processors to obtain valuable products with high added value that are in demand in the markets for the production of final products (in pharmaceuticals, perfume and cosmetics industry, ready-made food production, etc.). In the process of obtaining valuable products of agricultural raw materials there is a need for low-temperature condensation and/or low-temperature adsorption of useful products or intermediate technological substances. Low temperature refrigerated vapour traps with an operating temperature range of -70 °C to -110 °C and below are used for such process operations. In many technological applications, these traps are used in combination with vacuum processes, e.g. in the deposition of vacuum distillation products, which predetermines the requirements for hermetic tightness of the flowing part of such a trap. In recent years, in connection with the struggle to reduce emissions of gases that destroy the ozone layer and contribute to the greenhouse effect, the EU has banned the use of the cheapest and most efficient refrigerants, e.g. R13, which allows to obtain temperatures of about -100 °C using single-stage refrigeration machines. Modern refrigerants on the market, having an order of magnitude higher price, require 2-3 times higher design pressure from the equipment and have a lower cycle efficiency. In this regard, the creation of a low-temperature trap is a complex engineering task associated not only with the design of a multi-stage refrigeration machine, but also with the creation of a control system for the cascades of the refrigeration machine and vacuum pumping equipment, ensuring the safe and reliable operation of the trap and the achievement of the desired low temperature range during its long-term operation. SIA Cryogenic and vacuum systems have created a prototype of this low-temperature trap and is working on creating of processing complexes, included such traps for industrial quantities of processed biomaterials. The article highlights our engineering approaches, calculations and experience in creating a prototype of a low-temperature trap.

The human body emits a multitude of volatile organic compounds (VOCs) via tissues and various bodily fluids or exhaled breath. These compounds collectively create a distinctive chemical profile, which can potentially be employed to identify changes in human metabolism associated with colorectal cancer (CRC) and, consequently, facilitate the diagnosis of this disease. The main goal of this study was to investigate and characterize the VOCs’ chemical patterns associated with the breath of CRC patients and controls and identify potential expiratory markers of this disease. For this purpose, gas chromatography–mass spectrometry was applied. Collectively, 1656 distinct compounds were identified in the breath samples provided by 152 subjects. Twenty-two statistically significant VOCs (p-xylene; hexanal; 2-methyl-1,3-dioxolane; 2,2,4-trimethyl-1,3-pentanediol diisobutyrate; hexadecane; nonane; ethylbenzene; cyclohexanone; diethyl phthalate; 6-methyl-5-hepten-2-one; tetrahydro-2H-pyran-2-one; 2-butanone; benzaldehyde; dodecanal; benzothiazole; tetradecane; 1-dodecanol; 1-benzene; 3-methylcyclopentyl acetate; 1-nonene; toluene) were observed at higher concentrations in the exhaled breath of the CRC group. The elevated levels of these VOCs in CRC patients’ breath suggest the potential for these compounds to serve as biomarkers for CRC.

The increased risk of flooding due to global warming and subsequent heavy rainfall events in the Nordic-Baltic region, call for recommendations directed at long-term planning. One example of such recommendations are climate change allowances. These are often based on expected changes in design precipitation as given by climate model simulations, and are used as a buffer on top of current design values to avoid a future increased damage potential as a consequence of climate change. We here compute expected changes in precipitation design values, so-called climate factors (CFs), for the Nordic-Baltic region, based on 3 km convection permitting simulations from the Nordic Convection Permitting Climate Projections project. These have the advantage of explicitly resolving convection, which has been shown to be the main contributor to increased rainfall. We assess the dependence of the CFs on rainfall duration, return period, and geographical location, focusing on the summer (convective) season, short durations and the high emission scenario RCP8.5. We also compare these CFs to those computed from a non-convection permitting regional climate model ensemble.We found higher CFs for the longer return period, with only few exceptions, and distinctly higher CFs going from daily to sub-daily durations. However, the different simulations give conflicting results for very short-duration rainfall (<3 h). The huge difference in the climate sensitivity of driving GCMs dominates the magnitude of estimated return levels. Our analysis is shaped by the high computational costs of running convection permitting models, resulting in a very limited ensemble (3 members) representing a single emission scenario (RCP8.5). Therefore, we believe that combining results from convection permitting simulations with a larger ensemble (21 members) of non-convection permitting simulations adds value to the assessment of robust climate change allowances for heavy precipitation in the Nordic-Baltic region.

Coordinating transboundary aquifer management is becoming increasingly important worldwide to minimize adverse transboundary impacts. Moreover, the global trend of groundwater consumption is increasing, and groundwater abstraction exceeds sustainable limits in many parts of the world. To avoid future international disputes and maximize the rational and equitable use of common transboundary aquifers, it is imperative to accurately and comprehensively assess groundwater resources' development potential in these aquifers.As part of this study, a transient hydrogeological model using MODFLOW-NWT was developed to assess the changes in groundwater balance and groundwater flow in the transboundary area between Estonia and Latvia in northeast Europe. The model consists of eleven layers that discretize four main aquifers (Quaternary aquifer, Upper-Devonian aquifer, Upper-Middle-Devonian aquifer, and Lower-Middle-Devonian-Silurian aquifer) and represents an area of 45 000 km2. The cell size of the model varies from 0.25 to 1.00 km. The model was used to simulate three scenarios: (1) the base case scenario, which involved no abstraction, (2) the current abstraction, and (3) the maximum abstraction allowed. A detailed water balance for eight transboundary groundwater bodies for all three scenarios was calculated to assess water balance changes and groundwater flow along the national border.Model results indicate that the groundwater balance between groundwater bodies remained the same in Simulations 1 (base case scenario) and 2 (current water extraction), which indicates that the existing water extraction in the territory does not significantly affect the transboundary groundwater flow. Some minor changes were observed in Simulation 3 (maximum water abstraction rates), mostly in the Upper-Devonian groundwater bodies. However, significant changes in cross-border groundwater flow patterns were not expected even with the maximum possible water abstraction.The study has been founded by Iceland, Liechtenstein and Norway through the EEA and Norway Grants Fund for Regional Cooperation project No.2018-1-0137 &amp;#8220;EU-WATERRES: EU-integrated management system of cross-border groundwater resources and anthropogenic hazards&amp;#8221;.

Information on seismic monitoring in the East Baltic region for 2016–2017 is presented. During this period of time, several tectonic earthquakes occurred, the epicenters of which are located in the north and northwest of Estonia and in the area of Lake Võrtsjärv. The territory of Estonia and the adjacent waters of the Baltic Sea are still the most seismically active parts of the East Baltic region. Attention is drawn to the inherited nature of seismicity, i.e. in the areas of modern earthquakes, earthquakes had already occurred before the instrumental period. Another feature of several earthquakes in the East Baltic region is their association with meteorite craters, which are most often found in the East Baltic region in Estonia and near it, in the Baltic Sea. As before, the bulk of seismic information is associated with man-made explosions in industrial quarries and in the Baltic Sea. The identification of earthquakes of small magnitude remains an urgent problem.

The aim: Determination of focal mechanism of Lithuanian earthquake of 12.06.15 (t0 = 08:18:26.4; 55.52° N, 21.40° E; hs = 0.9 км.; ML = 2.6) by waveform inversion using direct waves and a limited number of stations. Method: Matrix method is used for modelling of seismic wave propagation in the medium modelled as horizontally layered heterogeneous elastic structure. There were obtained the relations of displacement waves on the free surface that were used for seismic tensor determination using only direct P- and S- waves. Determination of seismic tensor and the focal mechanism on the base of developed method for a point source is described. Thus, based on forward modeling, numerical techniques are developed for the inversion of observed waveforms for the components of moment tensor. Results: In the paper, a method is presented for the focal mechanism determination of Lithuanian earthquake of 12.06.15 (ML = 2.6) by waveform inversion using limited number of stations. The focal mechanism is determined using the data from two stations: PABE, SLIТ and from three stations: PABE, MTSE, SLIТ. These seismic stations are the part of BAVSEN (BalticVirtualSeismicNetwork). Scientific novelty: 1. In the paper, a method is presented for moment tensor inversion for the focal mechanism determination of events with a low seismicity. The East Baltic region (EBR) is the region with low seismicity. 2. The focal mechanism is determined using the data from a limited number of stations. Practical significance: The results of focal mechanism determination can be used to study seismicity for regions with a low seismicity using a limited number of stations.

In the town Valmiera of Latvia, the abandoned former black fuel storage area was not inspected before on the area contamination and its effect on the quality of groundwater at the storage environs. In 2016-2017, the storage area was investigated. In 2017, the quality of groundwater in the area environs was estimated and the oil contamination migration was explored by means of numerical modelling. The local hydrogeological model was developed jointly by specialists of the Latvian Environment, Geology and Meteorology Centre and Riga Technical University. The model was created by extracting information from the HM of Latvia LAMO4 and by supplying and reshaping its regional data by detailed information on the model area. The results of modelling ensure that in the closest storage area environs the groundwater quality has been only slightly worsened and no pollution of the nearby river should happen. Methods of developing and using the local hydrogeological and contaminant migration models may be useful for specialists dealing with groundwater contamination problems.