Pressed non-fired bricks from phosphogypsum waste for non-load bearing wall

In several countries of the world, phosphogypsum represents a large quantity of waste that poses serious problems of environmental and groundwater pollution. This study aims at recovering phosphogypsum, in its raw state without treatment, in the manufacture of non-load-bearing non-fired bricks. The study starts with the analysis of the radionuclide activity of the materials constituting the bricks, in particular phosphogypsum, in order to avoid any human health problems after the manufacture and use of the bricks. Then, several compositions are tested with several preservation methods in order to optimize the composition. The physical, chemical and mechanical resistance is determined. The results show the possibility to produce non-load-bearing bricks based on untreated phosphogypsum which comply with the standards requirements, using low energy. Indeed, among the considered mixtures, two compositions (60% of PG and of 75% of PG) perfectly verify the physical and mechanical tests. Also, storage of the mixtures for two days in the laboratory and then three days in an oven at 70°C, allows to obtain the best resistance to compression. Thus, the obtained resistance is much higher than the minimum value required for non-load-bearing bricks.

Assessment of radiation state of marine environment in the Leningrad NPP area according to long-term monitoring data (1973–2019)

The aim of the study was to conduct a radioecological assessment of the Leningrad NPP marine cooling reservoir – Koporye Bay of the Gulf of Finland. According to the international basic safety standards, accepted at the IAEA General Conference, this issue is of particular relevance due to the need to justify protection from technogenic radiation exposure both to humans and the environment. The assessment was based on the long-term radioecological monitoring data (1973–2019) within the Leningrad NPP observation area: radionuclides concentration in seawater, bottom sediments, and hydrobionts. The reference levels of radionuclides content in seawater and bottom sediments were used as indicators of the radiation state of the marine environment; their calculation procedure is defined in the Recommendations R 52.18.852-2016 and R 52.18.873-2018, issued by the Federal Service for Hydrometeorology and Environmental Monitoring (the Ministry of Natural Resources and Environment of the Russian Federation). These recommendations, developed by RPA “Typhoon” specialists, contain a methodology for assessing the radioecological state of the marine environment by the level of radionuclides activity, based on the principles, ensuring the maintenance of favorable environment, safety of marine hydrobionts, and radiation protection of humans. In the presence of various radionuclides in the marine environment, the sum of technogenic radionuclide activity ratios in seawater (bottom sediments) to the corresponding reference levels shall be below 1. According to monitoring data in the early period of NPP operation (1973–1985), a wide spectrum of technogenic radionuclides was observed in the marine ecosystem components. Along with 137Cs, significant contributors to the contamination of seawater and bottom sediments were 54Mn and 60Co. In contrast to reference levels for 137Cs, reference levels for 54Mn and 60Co in seawater are determined by an environmental criterion, not a radiation-hygienic one. The presence of technogenic radionuclides in algae was registered at distances, exceeding 10 km from the NPP. Biogenic transfer of corrosion radionuclides (54Mn, 60Co, and 65Zn) by fish into rivers, flowing into the Koporye Bay, was noted. The Chernobyl disaster led to a noticeable increase in the pollution of the Koporye Bay with technogenic radionuclides. In May – December 1986, the sum of technogenic radionuclide activity ratios in seawater to the reference levels exceeded the pre-accidental level by 100 times, and in bottom sediments – by 30 times. In 1986, 137Cs and 134Cs were the main contributors to the marine ecosystem radioactive contamination. Currently, the technogenic radioactivity of seawater and bottom sediments of the Koporye Bay is mainly determined by 137Cs; its level is relatively constant, which indicates the stability of the radioecological situation in the Leningrad NPP marine cooling reservoir.

Radioactivity measurements in the atmosphere and water column of Rogoznica Lake (central Adriatic)

<p>Croatian Science Foundation MARRES project (MARine lake (Rogoznica) as a model for EcoSystem functioning in a changing environment) aims to investigate the unique environment (slow exchange of seawater with the sea; atmospheric input is the only source of freshwater) of the marine lake which is an example of highly stratified (permanent anoxia bellow 9 m depth), and by climate changes affected marine system in the middle of the eastern Adriatic coast (43.53° N, 15.95° E). The area of the lake is characterized by the extensive tourism and mariculture, and the low impact of local industrial activities. It is also affected by the combined influence of long-range transport of air masses and local emissions (open-fire events).</p><p>An important part of the project is focused on the exchange and interaction between atmosphere, water column and sediment by measuring the atmospheric input (wet and dry deposition) of sulphur compounds, organic carbon, trace metals and radionuclides (Be-7, Pb-210).</p><p>This work for the first time will present the current state of the measurements of radioactivity in the Rogoznica lake area, including samples of aerosol particulate matter, PM2.5 < 2.5 um, rainwater and lake water column. Namely, the concentrations of Be-7 and Pb-210 in PM2.5 are measured to determine and correlate the dynamics of particle transport, meteorological information, especially origin of air masses and seasonal variation of PM2.5. While presence of Be-7 indicates the recent wet or dry deposition from the upper parts of the atmosphere, Pb-210 may be used as a tracer for continental air masses. Therefore, it can also indicate the influence of the pollution induced by human activity. Regarding that, special attention will be paid to compare results before and during the Covid-19 lockdown periods.</p><p>So far, preliminary results do not show significant difference in PM2.5 masses and measured radionuclide activity concentrations for the lockdown period. Be-7 and Pb-210 were regularly detected in aerosols collected on a glass fiber filters during a one-week sampling periods with the air flow rate of 2.3 m<sup>3</sup>/h. Their activity concentrations are determined by gamma spectrometry using High Purity Germanium detectors. The results are found to be correlated with PM2.5 masses, ranging from 2.9 to 12.2 Bq/m<sup>3</sup> for Be-7 and from 0.5 to 2.5 Bq/m<sup>3</sup> for Pb-210. First analyses show that the highest values can be related to the long-range transport of air masses and to the recorded near open-fire event. As expected, Be-7 is also detected in almost every rainwater sample (event), with the activity concentration up to 5.6 Bq/L, while low activities of Pb-210 are detected only sporadically. Related to that, Be-7 is detected in lake water column as well, but only in the surface layer and in samples collected during, or immediately after the rain events. </p><p>Dynamics and seasonal variation of radionuclide activity concentrations in here studied samples will be discussed, and the relationships with some meteorological parameters (temperature, wind speed, relative humidity, precipitation level) as well as local and long-range transport and physico-chemical conditions in the lake water column will be established.</p>