Surface ozone trends at El Arenosillo observatory from a new perspective.

Surface ozone trends observed at El Arenosillo observatory for the last 22 years (2000-2021) were investigated. The trends for daily averages and daily 5th and 95th percentiles were 1.2 ± 0.3 ppb decade-1, 2.2 ± 0.3 ppb decade-1 and -0.03 ± 0.43 ppb decade-1, respectively, thus showing a significant increase of background ozone. The surface temperature trends were also explored, obtaining trends of 0.5 ± 0.2 °C decade-1, 1.1 ± 0.2 °C decade-1 and -0.3 ± 0.2 °C decade-1 for daily averages, 5th and 95th percentiles, respectively. To identify potential changes in the ozone drivers, the weather pattern shifts were analyzed through the horizontal distribution trends of temperature at 2 m and geopotential height at 850 hPa. A strengthening of the Azores anticyclone and a regional warming were detected, which could contribute to the ozone trends obtained. The surface ozone trend in every month was explored, identifying a monthly pattern, with remarkable opposite trends in December-January (2.4 ± 0.9 ppb decade-1) vs July-August (-0.5 ± 1.1 ppb decade-1). The surface ozone trends for every hour of the day were also explored, identifying two clear patterns. The first pattern occurred from spring to autumn and was characterized by a behavior opposite to the typical daily ozone cycle. The second pattern was observed in winter, and it shows two relative peaks in the ozone trends (around 13:00 and 19:00 UTC). In a context of ozone precursor's depletion, changes in the weather conditions and warmer climate, to improve our knowledge of the ozone trends, we suggest exploring them based on daily and hourly averages.

Improvement in the accuracy of back trajectories using WRF to identify pollen sources in southern Iberian Peninsula.

Airborne pollen transport at micro-, meso-gamma and meso-beta scales must be studied by atmospheric models, having special relevance in complex terrain. In these cases, the accuracy of these models is mainly determined by the spatial resolution of the underlying meteorological dataset. This work examines how meteorological datasets determine the results obtained from atmospheric transport models used to describe pollen transport in the atmosphere. We investigate the effect of the spatial resolution when computing backward trajectories with the HYSPLIT model. We have used meteorological datasets from the WRF model with 27, 9 and 3 km resolutions and from the GDAS files with 1° resolution. This work allows characterizing atmospheric transport of Olea pollen in a region with complex flows. The results show that the complex terrain affects the trajectories and this effect varies with the different meteorological datasets. Overall, the change from GDAS to WRF-ARW inputs improves the analyses with the HYSPLIT model, thereby increasing the understanding the pollen episode. The results indicate that a spatial resolution of at least 9 km is needed to simulate atmospheric flows that are considerable affected by the relief of the landscape. The results suggest that the appropriate meteorological files should be considered when atmospheric models are used to characterize the atmospheric transport of pollen on micro-, meso-gamma and meso-beta scales. Furthermore, at these scales, the results are believed to be generally applicable for related areas such as the description of atmospheric transport of radionuclides or in the definition of nuclear-radioactivity emergency preparedness.

Spatial and temporal variation of surface ozone, NO and NO2 at urban, suburban, rural and industrial sites in the southwest of the Iberian Peninsula.

Surface ozone is one of the most important photochemical pollutants in the low atmosphere, causing damage to human health, vegetation, materials and climate. The weather (high temperatures and high solar radiation), orography (presence of the Guadalquivir valley) and anthropogenic (the cities of Cádiz, Córdoba, Huelva and Seville and two important industrial complexes) characteristics of the southwestern Iberian Peninsula make this region ideal for the formation and accumulation of ozone. To increase the knowledge of ozone behaviour in this area, the monthly, daily and weekly variations of ozone and its precursors, nitrogen oxides (NO(x) = NO + NO2), were analysed over a 4-year period (2003 to 2006). Using the k-means cluster technique, 12 representative stations of five different areas with different ozone behaviour were selected from a total of 29 monitoring sites. This is the first time that the analysis of these atmospheric pollutants has been carried out for the whole area, allowing therefore a complete understanding of the dynamics and the relationships of these compounds in this region. The results showed an opposite behaviour among ozone and NO and NO2 concentrations in urban and suburban zones, marked by maximums of ozone (minimums NO(x)) in spring and summer and minimums (maximums) in autumn and winter. A seasonal behaviour, with lower amplitude, was also observed in rural and industrial areas for ozone concentrations, with the NO and NO2 concentrations remaining at low and similar values during the year in rural zones due to the absence of emission sources in their surroundings. The daily cycles of ozone in urban, suburban and industrial sites registered a maximum value in the early afternoon (14:00-17:00 UTC) while for NOx two peaks were observed, at 7:00-10:00 UTC and 20:00-22:00. In the case of rural stations, no hourly peak of ozone or NO(x) was registered. The weekend effect was studied by using a statistical contrast tests (Student's t). The results indicated that only areas influenced by important traffic emissions presented a weekend effect for NO and NO2, whereas an ozone weekend effect was not detected in any case.

Sedimentary environmental quality of a biosphere reserve estuary in southwestern Iberian Peninsula.

The Huelva estuary is formed by the common mouths of the Odiel and Tinto Rivers, and inside this ecosystem is the biosphere reserve of the Odiel saltmarshes. This ecosystem has been historically affected by acid mine drainage (AMD) and by releases of pollutants from five phosphoric acid industrial plants and phosphogypsum (PG) waste stacks located in the area. This study carried out a comprehensive assessment of the environmental impact of the biosphere reserve of the Odiel saltmarshes. To this end, it was necessary to find a suitable sedimentary background (Piedras River in our case). To quantify this impact, several pollution indexes were used. According to the values reached by the indexes, this impact was classified as "serious" pollution for most trace elements, excepting the deepest layers, and "low-moderate" pollution for the 238U-series radionuclides, while no pollution for the 232Th-series and 40K radionuclides was found as expected.

Valorisation diagnosis of waste from the decontamination of phosphogypsum leachates through a combined calcium carbonate/hydroxide process.

Phosphogypsum is an industrial waste considered as naturally occurring radioactive material. Stack disposal and exposure to the environmental condition involve the production of acid leachates with high potential pollutant loads as heavy metals and radionuclides. In this study, a sequential neutralisation process was applied for cleaning the generated releases, and the two obtained residues were characterised from the physical-chemical and radiological point of view before their valorisation. The cleaning process was made up of two steps: the first one using calcium carbonate until pH = 3.5, and the second one using calcium hydroxide until pH = 12. The residue obtained in the first step was mostly calcium fluoride, while in the second step most phosphates were precipitated, mainly as hydroxyapatite. The final liquid was treated to reduce pH lower than 9, which is the limit included in the current directive for discharges of liquid effluents into coastal waters. The main conclusion was that the solids from the first step could be valorised as an additive in the manufacture of commercial Portland cements and ceramics, while the solids from the second step could be used as raw material for the phosphoric acid manufacture.

Occupational exposures in two industrial plants devoted to the production of ammonium phosphate fertilisers.

In order to fill a gap in the open literature, occupational exposures and activity concentrations have been assessed in two NORM industrial plants, located in the south-west of Spain, devoted to the production of mono-ammonium phosphate (MAP) and di-ammonium phosphate (DAP) fertilisers. The annual effective doses received by the workers from these plants are clearly below 1 mSv yr(-1) and the contribution due to external radiation is similar to that due to inhalation. The contribution to the maximum effective doses due to inhalation of particulate matter has been estimated to be about 0.12 mSv yr(-1), while the (222)Rn concentrations inside the plants are of no concern. Consequently, no additional actions or radiological protection measures need to be taken to decrease the natural radiation received by the workers in these facilities.

A new efficiency calibration methodology for different atmospheric filter geometries by using coaxial Ge detectors.

The study of the different pollutants present in atmospheric aerosols such as trace elements and radionuclides is essential to assess the air quality. To analyze the particulate matter (PM), atmospheric filters with different dimensions and geometries (rectangular, circular, slotted, and square filters) are usually employed. Regarding the pollutants existing in atmospheric aerosols, radionuclides are usually analyzed due to their multiple applications such as either in the environmental radiological control or as tracers of atmospheric processes. Therefore, this study aims to develop a new and general methodology to calibrate in efficiency coaxial Ge detectors to properly determine radionuclides present in the PM by gamma-ray spectrometry for several filter types. For this, granular certified reference materials (CRM) containing only natural radionuclides (238U-series, 232Th-series, and 40 K) were selected. Several granular solid CRMs were chosen allowing us to reproduce the same PM deposition geometry and to assure the homogeneity of the added CRMs. These are the main advantages in relation to the typical methods that use liquid CRMs. Furthermore, for filters whose surfaces are relatively large, they were cut in several pieces and placed one on top of the other, achieving the same geometry than the PM deposited onto the filter. Then, the experimental full-energy peak efficiencies (FEPEs) were obtained for each energy of interest (Eγ) and they were fitted versus Eγ, finding a general FEPE function for each filter type. Finally, this methodology was validated for both natural and artificial radionuclides (from 46 to 1332 keV) by using different filter types employed in proficiency test exercises, obtaining |zscore|< 2 for all cases. Supplementary Information: The online version contains supplementary material available at 10.1007/s11869-023-01336-x.

A methodology to determine 212Pb, 212Bi, 214Pb and 214Bi in atmospheric aerosols; Application to precisely obtain aerosol residence times and Rn-daughters' equilibrium factors.

Progeny of 222Rn and 220Rn, (212Pb, 212Bi, 214Pb and 214Bi) are essential to assess radiological hazard, external and internal doses, residence times and equilibrium factors. Precise measurements of these nuclides are quite complex due to their very short half-lives. This study outlines a new and precise methodology to measure these nuclides. Radon-222 and 220Rn were measured using a radon monitoring system, while their respective progenies were collected in an atmospheric filter using an ASS-500 sampler and measured by gamma-ray spectrometry. The 212Pb concentrations were very similar to the thoron ones, where all 212Bi/212Pb ratios were consistently less than 1. The relative uncertainties, σr, of the 212Pb and 212Bi activity concentrations, and 212Bi/212Pb activity ratio are generally less than 10%. Moreover, 214Pb/222Rn ratios were about 0.7, agreeing well with previous works. The σr for 214Pb, 214Bi and 214Bi/214Pb were generally less than 6%. This methodology was applied to estimate aerosol residence times using the 214Pb/222Rn and 212Bi/212Pb activity ratios, and to obtain equilibrium factors, achieving consistent results. Furthermore, the methodology consistency and validity range were studied with time elapsed between sampling end and counting start, and the sampling durations, finding the optimum times to precisely determine 212Pb, 212Bi, 214Pb and 214Bi.

Spatiotemporal evolution of U and Th isotopes in a mine effluent highly polluted by Acid Mine Drainage (AMD).

The spatiotemporal evolution of both U and Th isotopes in a mine effluent highly polluted by acid mine drainage (AMD) was evaluated. The acidic tributary, which born from the outflows of an abandoned sulfide mine, flows into the Odiel River. AMD comprises an important source of natural radionuclides, presenting concentrations of 238U and 232Th, two and four orders of magnitude higher, respectively, than the background values of surface continental waters. These natural radionuclides behave conservatively along the mine effluent (pH < 2.5) throughout the hydrological year. Under AMD conditions uranium is in the hexavalent state U(VI) and the main dissolved species are uranyl sulfate complexes. The polluted tributary has a significant impact on the Odiel River acidifying its waters during the low flow season and increasing up to one order of magnitude the activity concentrations of U and Th isotopes. U presented a conservative behavior in the Odiel River during the low flow season (pH ≈ 3), however it is removed from the liquid phase in the wet season (pH ≈ 6), probably due its coprecipitation/adsorption onto Al-phases. Th shows a high sensitivity to small increases of pH, and it is strongly coprecipitated/adsorbed with or onto Fe-oxyhydroxydizes in the river.

Radioactive impact in South Korea from the damaged nuclear reactors in Fukushima: evidence of long and short range transport.

Traces of long-lived fallout-derived radioisotopes ((134)Cs and (137)Cs) were found in wet and dry deposition samples collected from the west and east coasts of South Korea from March to May 2011 following the release of radionuclides from the damaged nuclear power plants in Fukushima, Japan. The analysis of air mass back trajectory and atmospheric pressure systems indicated that the Fukushima-derived radiocaesium had predominantly reached South Korea from the west by surface westerlies from 11 March to 5 April; however, after 6 April, air masses arrived from Japan directly due to a high pressure system that developed to the east of Japan. Spatial variation of deposition fluxes of radiocaesium in South Korea was partly attributed to the presence of local longitudinal orography.

Radiological and chemical risks by waste scales generated in the titanium dioxide industry.

Along the industrial process devoted to the production of titanium dioxide pigments by using ilmenite as main raw material, small residues amounts are generated, remaining clearly enriched in natural radionuclides and chemical pollutants. Between them, we can remark the scales enriched in both radium isotopes and lead, which are formed in the internal walls of pipes and some equipment. These scales are radiological anomalies that demand its mineralogical, elemental and radiometric characterization as a basis for a detailed radiological and toxicological assessment from the occupational and public point of view. In this work, several scales collected in a TiO2 pigment production plant in South of Spain have been mineralogically characterized by XRD, while information about their elemental composition and morphology have been obtained by applying the XRF and SEM techniques. In addition, radiometric determinations have been performed by gamma-ray and alpha-particle spectrometry. The performed study indicates that the radiological doses received due to the scales by the workers performing its conventional activities are clearly lower than 1 mSv/y. Special dosimetric and chemical controls could be needed for the workers in charge of the maintenance labours (which include the removal of the scales) if these workers belong to an external company devoted to perform maintenance operations in several NORM industries.

Behaviour of heavy metals and natural radionuclides in the mixing of phosphogypsum leachates with seawater.

Phosphogypsum (PG) is disposed worldwide in large stacks usually placed in coastal zones, as in the case of Huelva (SW of Spain), where around 100 Mt of PG are stored on the salt marshes of the Tinto River estuary covering a surface of about 1000 ha. This management generates the weathering of PG, and due to its high acidity (pH ≈ 2) and pollutant load can provoke significant emissions into their surroundings. In this work were evaluated by laboratory experiments the effects of pH increase in the behaviour of heavy metals and natural radionuclides during the mixing of phosphogypsum leachates with seawater. The acidic phosphogypsum leachates showed concentrations of heavy metals from two to three orders of magnitude higher than natural continental waters, and natural radionuclides (U-isotopes and 210Po) from four to five orders of magnitude higher than unperturbed aquatic systems. Major elements and some heavy metals as Mn, Ni, Cd, As, Sb and Co showed a conservative behaviour during the neutralisation of the leachates with seawater, remaining in the liquid phase, while other ones as Al, Fe, Cr, Zn, Cu, Pb precipitated and/or were adsorbed onto the solid phase. The U-isotopes and 210Po showed a clear non-conservative behaviour probably due to coprecipitation/adsorption processes onto the formed precipitates, but while 210Po reached a total removal at pH ≈ 7, U- isotopes after a total removal at pH ≈ 5 returned into the liquid phase due to redissolution/desorption processes at near neutral pH. The formed precipitates, mainly composed by iron phosphates particles, showed heavy metal and natural radionuclide concentrations from one to three orders of magnitude higher than unperturbed soils. All these facts demonstrate the serious environmental impact produced by the PG stacks into their surroundings and the urgency of effective restoration measures.

Radon transport events associated with the impact of a NORM repository in the SW of Europe.

Two radon measurement stations located to the north and south of a NORM (Naturally Occurring Radioactive Materials) repository of phosphogypsum (southwest of Europe) were used to monitor radon behavior during 2018. The stations are located at opposing sides of the repository, one in Huelva City to the north and other one in a rural area to the south. This setup aimed to identify the influence of the NORM repository on each station and use radon levels as a marker of atmospheric transport in the local area. To achieve this, a comparison was carried out with other coastal stations in the south of Spain, finding higher average concentrations in Huelva City, ~3.3 Bq m-3. Hierarchical clustering was applied to identify days with different radon patterns at each Huelva station, detecting possible local radon transport events from the repository. Three events were investigated with WRF (Weather Research and Forecasting) and FLEXPART-WRF (FLEXible PARTicle dispersion model). It was found that both sampling sites required atmospheric stagnant conditions to reach high radon concentration. However, under these conditions the urban station showed high radon regardless of wind direction while the rural station also required radon transport from the repository, either directly or indirectly.

Arsenic removal procedure for the electrolyte from a hydro-pyrometallurgical complex.

Commercial copper (Cu) is obtained by a hydro-pyrometallurgical process, where the Cu anodes obtained in the furnaces (Cu > 99.5%) are enriched up to 99.99% in "cathodes" by electrorefining at an electrolysis plant. During this process, some impurities accumulate in the electrolyte, mainly arsenic (As), which decrease the quality of the Cu cathode. For this reason, the electrolyte is sent to an electrolyte cleaning plant (ECP) for its purification. Electrolyte sludge (ES) is produced in the last stage of purification and is recirculated back to the furnace due to the high Cu content. This recirculation involves a severe problem of As accumulation in the industrial process. The objective of this work was to develop a procedure to fully dissolve the ES, removing the As and recovering its Cu content. The ES dissolution process was optimised (dissolution efficiency > 99%) in H2SO4 (1.4 M)/HNO3 (1.8 M) medium using a 1:20 g mL-1 solid-to-liquid ratio. As was removed from the ES solution by its precipitation as iron (III) arsenate, with high efficiency (more than 70%). After As removal, the Cu can be precipitated as copper sulphate, which is used in several applications.

Development of a reference material for analysing naturally occurring radioactive material from the steel industry.

Accurate measurement of naturally occurring radionuclides in blast furnace slag, a by-product of the steel industry, is required for compliance with building regulations where it is often used as an ingredient in cement. A matrix reference blast furnace slag material has been developed to support traceability in these measurements. Raw material provided by a commercial producer underwent stability and homogeneity testing, as well as characterisation of matrix constituents, to provide a final candidate reference material. The radionuclide content was then determined during a comparison exercise that included 23 laboratories from 14 countries. Participants determined the activity per unit mass for 226Ra, 232Th and 40K using a range of techniques. The consensus values obtained from the power-moderated mean of the reported participant results were used as indicative activity per unit mass values for the three radionuclides: A0(226Ra) = 106.3 (34) Bq·kg-1, A0(232Th) = 130.0 (48) Bq·kg-1 and A0(40K) = 161 (11) Bq·kg-1 (where the number in parentheses is the numerical value of the combined standard uncertainty referred to the corresponding last digits of the quoted result). This exercise helps to address the current shortage of NORM industry reference materials, putting in place infrastructure for production of further reference materials.

Ground-based and OMI-TROPOMI NO2 measurements at El Arenosillo observatory: Unexpected upward trends.

Eleven years, January 2008 to June 2019, of hourly nitrogen dioxide (NO2) levels recorded at El Arenosillo observatory (Southwestern Europe) were analyzed. Annual averages ranged between 4 µg m-3 and 6 µg m-3 with peaks exceeding 40 µg m-3. A slight monthly variation was observed with maximum and minimum values in the cold (∼6 µg m-3) and warm (∼4 µg m-3) seasons respectively. A diurnal pattern was found with a weak amplitude (∼3 µg m-3). The monthly trends were investigated using surface observations and OMI (Ozone Monitoring instrument) satellite measurements. An unexpected upward trend was obtained in the last five years. The periods with elevated NO2 concentrations in the last years were analyzed, showing an increase in its frequency and concentrations, linked with the upward trend observed. The weather conditions in these NO2 peaks were studied using local surface meteorology, mean sea level pressure and wind fields from the data reanalysis of ERA5. The transport of NO2 was explored using TROPOMI (Tropospheric Monitoring Instrument) measurements. The events occurred under conditions governed by high-pressure systems, which induced weak synoptic airflows or the development of mesoscale processes. Four scenarios of NO2 transport were identified, associated with weak synoptic flows from inland or Southern Portugal and with mesoscale processes. The gulf of Cadiz plays an important role as a reservoir where the NO2 coming from the south of Portugal, the Western Mediterranean Basin and urban-industrial areas can be accumulated and later transported inland. A strong correlation was found between the increase of NO2 observed in the last years and positive anomalies of the temperature and geopotential height at 850 and 500 hPa levels. These findings could indicate that the causes of the changes in the NO2 would be attributed to alterations in the weather patterns associated with a warmer climate.

Influence of the accumulation chamber insertion depth to measure surface radon exhalation rates.

A common method to measure radon exhalation rates relies on the accumulation chamber technique. Usually, this approach only considers one-dimensional gas transport within the soil that neglects lateral diffusion. However, this lateral transport could reduce the reliability of the method. In this work, several cylindrical-shaped accumulation chambers were built with different heights to test if the insertion depth of the chamber into the soil improves the reliability of the method and, in that case, if it could limit the radon lateral diffusion effects. To check this hypothesis in laboratory, two reference exhalation boxes were manufactured using phosphogypsum from a repository located nearby the city of Huelva, in the southwest of Spain. Laboratory experiments showed that insertion depth had a deep impact in reducing the effective decay constant of the system, extending the interval where the linear fitting can be applied, and consistently obtaining reliable exhalation measurements once a minimum insertion depth is employed. Field experiments carried out in the phosphogypsum repository showed that increasing the insertion depth could reduce the influence of external effects, increasing the repeatability of the method. These experiments provided a method to obtain consistent radon exhalation measurements over the phosphogypsum repository.

Radiological and physico-chemical characterization of materials from phosphoric acid production plant to assess the workers radiological risks.

The industry devoted to the production of phosphoric acid by using as raw material sedimentary phosphate rock (PR) is considered as a NORM activity (Naturally Occurring Radioactive Materials), due to the high levels of U-series radionuclides contained in this ore, which are 1-2 orders of magnitude higher than those in unperturbed soils. This fact allowed us to develop a deep characterization of the raw materials, wastes, main intermediate materials, and final products obtained at a typical phosphoric acid factory. The elemental composition (major, minor and trace elements), radionuclide concentrations, grain size distribution, mineralogy and micro-structural composition were analyzed. The aim of this characterization was to obtain information for operators and maintenance personnel involved in clean-up and waste management operations. The highest concentrations of some heavy metals and radionuclide activity concentrations were found in the "scales" (or internal incrustations)from the pipes that carry either phosphoric acid (PA) or the phosphogypsum waste (PG). The highest concentrations where found for 226Ra and 40K,with values up to 9 and 5 Bq g-1, respectively. In addition, high concentrations of many toxic heavy metals and trace elements, such as Cd, Cr, Ni, Sr, Y, V, Zn, Th, and U, were found in some sludge samples. The shielding effect of the containers/vessels/pipes has an essential role in the measured external dose in the intermediate products. The radiological implications of natural radionuclides with higher activity showed that if the maximum particulate matter concentration established in the Spanish regulation is verified, and taking into account the most conservative scenario, the annual limit of 1 mSv y-1 is not exceeded.

Evidences of different meteorological patterns governing 7Be and 210Pb surface levels in the southern Iberian Peninsula.

7Be, 210Pb and PM10 levels in surface air have been simultaneously measured at two sampling sites in the southern Iberian Peninsula for a period of two years. Each site covers one different meteorological area of the Guadalquivir valley, from the mouth (Huelva) to the middle point (Cordoba). The objective of the present study is to analyse the spatial variability of both natural radionuclides, and to identify and characterise the meteorological patterns associated with similar and different surface concentration levels in this complex region. Concentrations are similar in both sampling sites. 7Be level is in the 0.6-15.5 mBq m-3 range in Huelva and 1.2-13.3 mBq m-3 in Córdoba, 210Pb activity concentrations are between 0.04 and 2.30 mBq m-3 in Huelva, and between 0.03 and 1.2 mBq m-3 in Cordoba, and PM10 concentrations are found to be in the 5.1-81.3 µg m-3 range in Huelva, and 8.2-76.3 µg m-3 in Cordoba, respectively. A linear regression analysis indicates more regional variability for 210Pb than for 7Be between simultaneous measurements. Principal components analysis (PCA) is applied to the datasets and the results reveal that aerosol behaviour is mainly represented by two components, which explain 82% of the total variance. The analysis of surface measurements and meteorological parameters revealed that component F1 groups sampling periods in which the influence of similar meteorological conditions over the region lead to similar 7Be, 210Pb and PM10 concentration levels in both sampling sites. On the other hand, component F2 detaches the 7Be, 210Pb and PM10 concentration levels between monitoring sites, and the meteorological analysis shows how surface concentrations within this component are associated with the development of different mesoscale circulations in each part of the valley. The identification of sampling periods characterised by differences in surface concentrations and wind patterns between stations suggests that the valley could not be considered as one single unit for certain meteorological scenarios. These results evidence how the understanding of wind characteristics within a complex terrain provide some essential knowledge in the regionalization and/or optimization of monitoring networks.

An improved method for radium-isotopes quartet determination by alpha-particle spectrometry by using 225Ra (229Th) as isotopic tracer.

A new method for the determination of radium quartet (223,224,226,228Ra) in environmental samples by alpha-particle spectrometry with PIPS detectors is described. This uses 225Ra as yield tracer, in equilibrium at the beginning with 229Th. Thorium is removed from the sample by using AG1X8 anion-resin, and then radium isotopes are isolated and purified with a cation-exchange column Biorad AG50X8, verifying that Ac has been fully removed from the sample to ensure the good evaluation of the Ra yield (average decontamination factor > 92%). Finally, the counting source of radium is obtained by micro-precipitation with BaSO4. This method produces high spectral resolution (<35 keV), and quantitative Ra recoveries (>70%). In this new method, NH4Ac in 0.1 M HNO3 is used to remove the 225Ac contained in the sample in order to avoid its future spectral interference in the yield calculation. The method has been validated by using certified reference samples with known concentrations of radium isotopes.