Pb-210 and Po-210 atmospheric releases via fly ash from oil shale-fired power plants

Review on heavy metal contaminants in freshwater fish in South India: current situation and future perspective

The primary natural resource we use in our daily lives for a variety of activities is freshwater for drinking and various developmental goals. Furthermore, the pace of human population increase worldwide is rising rapidly and has a great impact on the Earth's natural resources. Natural water quality has diminished owing to various anthropogenic activities. Water is crucial to the life cycle. On the other hand, chemical and agricultural industries pollute heavy metals. Acute and chronic diseases caused by heavy metals, such as slow metabolism and damage to the gills and epithelial layer of fish species, are divided into two categories. Pollutants can also harm liver tissues and result in ulceration as well as diseases such as fin rot, tail rot, and gill disease. The most prevalent heavy metals are As, Cr, Pb, and Hg, which are systemic toxicants that affect human health. These metals are categorized as carcinogens by the US Environmental Protection Agency and the worldwide agency for cancer research because they cause organ damage even at low exposure levels. The focus of the current study is to review various freshwater sources of heavy metal pollution.

Sediment mercury concentration changes as a response to increased industrial activity in Coronel Bay, Chile

Among the main sources of atmospheric mercury emissions are thermoelectric plants that use coal to generate electricity. This heavy metal is transported by air from its origin to neighboring coastal areas, where it is deposited in the sediment record. This research evaluated the content and temporal distribution of Hg in the coastal sediments of Central Chile, Coronel Bay, industrialized zone with two operative thermoelectric plants, and Coliumo Bay, reference zone free of industry. To this end, sediment cores from the centers of the two bays were obtained. Laboratory results show that the greatest Hg contents were found in the surface strata of the Coronel Bay core, with concentrations up to an order of magnitude greater than those obtained in the same strata in Coliumo Bay. This increase in Hg concentration coincides with the beginning of industrial activity in Coronel, with greater concentrations observed from 2012 on, the year in which the industrial operation of two coal-fired thermoelectric plants on the bay began. Based on ²¹⁰Pb activity and the relationships between Hg content and organic matter, it was established that the main pathway of Hg to sediment is atmospheric deposition, while Coliumo presented inputs that reflect local non anthropogenic sources.

A preliminary study on the eco-environmental geological issue of in-situ oil shale mining by a physical model

As traditional methods of oil shale production emitting high levels of pollutants, in-situ exploitation has aroused great concerns. In order to study the effect of in-situ pyrolysis products on the underground environment, an in-situ oil shale exploitation of underground environment impact laboratory simulation system was designed. Based on the hydrogeological condition of oil shale area in Nong'an City, a physical simulation test was conducted. It was found the temperature of surrounding layers continued to be perturbed after heating of the formation had stopped. The time during which the temperature was perturbed was about 4-5 times the heating period. During the simulation test, stray gas migration through fractures and faults was considered a mechanism for groundwater contamination. In the test, the maximum TOC content in aquifer was the value of 97.0 mg/L. The maximum total petroleum hydrocarbon (TPH) content of the simulated formation was 129 mg/kg after oil pyrolysis.

Correlations between 7Be, 210Pb, dust and PM10 concentrations in relation to meteorological conditions in northern Poland in 1998-2018

Analysis of a twenty-year (1998-2018) data series on ⁷Be concentrations in weekly collected aerosol samples in northern Poland showed a clear pattern of seasonal changes in ⁷Be with a maximum in the summer period associated with the most intensive thermal convection and vertical mixing. Activity concentrations of ⁷Be ranged from 480 μBq m^-3 to 9370 μBq m^-3. A strong relationship has been shown between ⁷Be concentrations observed in years and the activity of the Sun related to the sunspot number. Activity concentrations of ²¹⁰Pb in aerosol ranged from 17 μBq m^-3 to 1490 μBq m-3 with maximum occurring in the winter. The difference in the seasonal pattern in ⁷Be and ²¹⁰Pb concentrations were directly related to the different sources of both isotopes, as an additional source of ²¹⁰Pb was the products of combustion during the heating season. Similar pattern with maximum concentrations in winter was observed for PM10, as the main source is the same as in the case ²¹⁰Pb. A content of PM10 was in the range from 6.5 to 81.7 μg m^-3. A statistically significant correlation between both isotopes occurs. At the same time, ⁷Be, ²¹⁰Pb and PM10 are visibly related to the dust concentrations ranged from 7.3 μg m^-3 in winter to 134.8 μg m^-3 in spring. Statistical analysis carried out with simple regression model, stepwise multiple regression, and Random Forest models showed that the sunspots number, air temperature and sunshine duration have the most substantial impact on transport, and hence the concentration of ⁷Be in the surface layer of the atmosphere. The increase in relative humidity and precipitation and higher wind speed have a statistically significant effect on the reduction of ⁷Be concentrations in surface air.

Determination of polonium-210 in environmental samples using diglycolamide-based cloud point extraction coupled to alpha spectrometry analysis

This study presents a novel cloud point extraction (CPE) methodology for the separation and enrichment of polonium-210 prior to alpha-spectrometric quantification in water, urine and digested samples. The extractive behaviour of diglycolamide-based ligands towards Po by CPE was determined and optimised in various acidic conditions. The extraction efficiency and selectivity of the CPE systems depend greatly on the choice of the extracting agent and acidic conditions. The thorough optimisation of those specific parameters has led to the development of a suitable cloud point extraction system for the determination of polonium-210 at ultra-trace levels compatible with alpha-spectrometry. To facilitate this coupling, a back-extraction procedure was optimised and performed on the surfactant-rich phase to enable the spontaneous deposition of polonium-210 onto a silver disk; this also avoids making the matrix transfer step mandatory due to the presence of a nitric medium. Method detection and quantification limits of 3.5 and 12 mBq L^-1, respectively, were determined by alpha spectrometry. The robustness of the proposed methodology was demonstrated by the determination of polonium ions concentration in various environmental and biological samples and solid certified reference materials.

Modeling of 210Pb and 210Po radionuclide emissions from local power plants in central Poland

Due to the more volatile nature of ²¹⁰Po in relation to ²¹⁰Pb, an imbalance of activity concentrations in high temperature combustion processes can be observed, especially in fine particulates (diameter < 0.1, 0.2 and 0.5 μm). In the atmosphere and in the soil around coal-fired power plants, ²¹⁰Pb and ²¹⁰Po concentrations are a combination of activities from natural and anthropogenic sources. In this study only portions of ²¹⁰Po and ²¹⁰Pb radionuclides resulting from energy production activities were analyzed. Due to the high mobility of fine particles, a surface area of 172 km × 140 km in central Poland was chosen for simulation. For validation of the modeling approach, three grid versions were applied: 1 km, 2 km and 4 km. Simulated results confirmed experimental-computational values of an excess of both radionuclides in the atmosphere in 2017 in the city of Lodz. Different aerosol fractions, seasons and various grids in the selected area were subjected to 36 individual simulations. The ²¹⁰Po activity concentrations measured in winter and summer 2017 were 42.5 and 8.99 μBq m^-3, respectively. Simulated and measured values of artificial ²¹⁰Po and ²¹⁰Pb activities are well correlated.

Enrichment of naturally occurring radionuclides and trace elements in Yatagan and Yenikoy coal-fired thermal power plants, Turkey

Coal, residues and waste produced by the combustion of the coal contain naturally occurring radionuclides such as ²³⁸U, ²²⁶Ra, ²¹⁰Pb, ²³²Th and ⁴⁰K and trace elements such as Cd, Cr, Pb, Ni and Zn. In this work, coal and its combustion residues collected from Yatagan and Yenikoy coal fired thermal power plants (CPPs) in Turkey were studied to determine the concentrations of natural radionuclides and trace elements, and their enrichments factors to better understand the radionuclide concentration processes within the combustion system. In addition, the utilization of coal fly ash as a secondary raw material in building industry was also studied in terms of radiological aspects. Fly ash samples were taken at different stages along the emission control system of the thermal power plants. Activity concentrations of naturally occurring radionuclides were determined with Canberra Broad Energy Germanium (BEGe) detector BE3830-P and ORTEC Soloist PIPS type semiconductor detector. The particle size distribution and trace elements contents were determined in various ash fractions by the laser scattering particle size distribution analyzer and inductively coupled plasma (ICP-OES). From the obtained data, natural radionuclides tend to condense on fly ash with and the activity concentrations increase as the temperature drop in CPPs. Measured ²¹⁰Pb and ²¹⁰Po concentration varied between 186 ± 20-1153 ± 44 Bq kg^-1, and 56 ± 5-1174 ± 45 Bq kg^-1, respectively. The highest ²¹⁰Pb and ²¹⁰Po activity concentrations were determined in fly ash taken from the temporary storage point as 1153 ± 44 Bq kg^-1 and 1174 ± 45 Bq kg^-1, respectively. There were significant differences in the activity concentrations of some natural radionuclide and trace elements (Pb and Zn) contents in ash fractions among the sampling point inside both of the plants (ANOVA, p < 0.001). Coal and ash sample analysis showed an increase activity concentration and enrichment factors towards the electrostatic precipitators for both of the power plants. The enrichment factors for Zn follow a similar trend as Pb, increasing in value towards the end of the emission control system. The calculated activity indexes were above 1.0 value for both of the power plants, assuming the utilization of fly ash at 100%. It can be concluded that the reuse of fly ash as a secondary raw material may not be hazardous depending on the percentage of utilization of ash.

Heavy Metal Pollution and Ecological Assessment around the Jinsha Coal-Fired Power Plant (China)

Heavy metal pollution is a serious problem worldwide. In this study, 41 soil samples and 32 cabbage samples were collected from the area surrounding the Jinsha coal-fired power plant (JCFP Plant) in Guizhou Province, southwest China. Pb, Cd, Hg, As, Cu and Cr concentrations in soil samples and cabbage samples were analysed to study the pollution sources and risks of heavy metals around the power plant. The results indicate that the JCFP Plant contributes to the Pb, Cd, As, Hg, Cu, and Cr pollution in nearby soils, particularly Hg pollution. Cu and Cr in soils from both croplands and forestlands in the study area derive mainly from crustal materials or natural processes. Pb, Cd and As in soils from croplands arise partly through anthropogenic activities, but these elements in soils from forestlands originate mainly from crustal materials or natural processes. Hg pollution in soils from both croplands and forestlands is caused mainly by fly ash from the JCFP Plant. The cabbages grown in the study area were severely contaminated with heavy metals, and more than 90% of the cabbages had Pb concentrations exceeding the permissible level established by the Ministry of Health and the Standardization Administration of the People’s Republic of China. Additionally, 30% of the cabbages had As concentrations exceeding the permissible level. Because forests can protect soils from heavy metal pollution caused by atmospheric deposition, close attention should be given to the Hg pollution in soils and to the concentrations of Pb, As, Hg and Cr in vegetables from the study area.

Long-term modelling of fly ash and radionuclide emissions as well as deposition fluxes due to the operation of large oil shale-fired power plants

Two of the world's largest oil shale-fired power plants (PPs) in Estonia have been operational over 40 years, emitting various pollutants, such as fly ash, SO_x, NO_x, heavy metals, volatile organic compounds as well as radionuclides to the environment. The emissions from these PPs have varied significantly during this period, with the maximum during the 1970s and 1980s. The oil shale burned in the PPs contains naturally occurring radionuclides from the ²³⁸U and ²³²Th decay series as well as ⁴⁰K. These radionuclides become enriched in fly ash fractions (up to 10 times), especially in the fine fly ash escaping the purification system. Using a validated Gaussian-plume model, atmospheric dispersion modelling was carried out to determine the quantity and a real magnitude of fly ash and radionuclide deposition fluxes during different decades. The maximum deposition fluxes of volatile radionuclides (²¹⁰Pb and ²¹⁰Po) were around 70 mBq m^-2 d^-1 nearby the PPs during 1970s and 1980s. Due to the reduction of burned oil shale and significant renovations done on the PPs, the deposition fluxes were reduced to 10 mBq m^-2 d^-1 in the 2000s and down to 1.5 mBq m^-2 d^-1 in 2015. The maximum deposition occurs within couple of kilometers of the PPs, but the impacted area extends to over 50 km from the sources. For many radionuclides, including ²¹⁰Po, the PPs have been larger contributors of radionuclides to the environment via atmospheric pathway than natural sources. This is the first time that the emissions and deposition fluxes of radionuclides from the PPs have been quantified, providing the information about their radionuclide deposition load on the surrounding environment during various time periods.