Occupational, public and environmental radiological impact caused by the phosphoric acid industry: the case of Huelva (Spain)

Chapter 5 Occupational, Public and Environmental Radiological Impact Caused by the Phosphoric Acid Industry: The Case of Huelva (Spain) José Luis Guerrero‐Márquez, Fernando Mosqueda Peña, Juan Mantero, Guillermo Manjón, Rafael García‐Tenorio and Juan Pedro Bolívar Additional information is available at the end of the chapter http://dx.doi.org/10.5772/intechopen.68567 Abstract The production of phosphate fertilizers usually uses as raw material sedimentary phosphate rock, which contains enhanced concentrations from U‐series radionuclides about 10–100 times higher than unperturbed soils. This fact implies the need for evaluating the radiological implications of this activity. In our case, the study has been performed in a large fertilizer industrial complex located at Huelva town (SW of Spain), where sedimentary phosphate rock has been processed since 1965 to 2010, generating annually an average of about 2.5 million tons of a by‐product called phosphogypsum (PG), which has been stored in big stacks 1 km away from Huelva city, covering 1000 ha. The fluxes of the radionuclides of interest along the production process and the effective doses received by the workers have been determined. In addition, the radioecological impact associated to the waste management strategy followed has been evaluated. Keywords: NORM, radiation doses, phosphogypsum, radioecological impact 1. Introduction The production of phosphoric acid (PA) from phosphate ore deposits is essential because phosphorus is an essential element to all living systems, and especially for the plants. The phosphate fertilizers and animal feeds (among others) are manufactured by using the PA as © 2017 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. raw material. The bioavailable phosphorus is usually present in very low quantity in most agricultural soils, and for this reason, it is necessary to add it as soluble phosphate. Total global phosphate reserves are estimated to be around 1.6× 109 tons. Most of these deposits are from sedimentary origin, with as little as 4% being of igneous origin [1]. Phosphatic materials are usually characterized in terms of their P2O5 concentration in percentage. This is done as a convenience and not as a strict chemical description. Phosphate ores generally have P2O5 concentrations ranging from 4 to 40%. In simplified form, phosphate ore is converted into commercial products using the following three main process steps: i) After being mined, phosphate ore is beneficiated to produce a concentrate known as phosphate rock (PR). ii) According to International Fertilizer Industry Association [2], as much as 85% of the phosphate rock produced in step (i) is converted into intermediate or final products using a process of acid digestion known as the “wet process.” A relatively small amount of PR is converted directly into elemental phosphorus by reduction in an electric arc furnace in a process known as the”thermal process,” in order to obtain a more pure PA. It is estimated that 71% of all PR produced is processed into phosphoric acid, with the generation of a by‐product called “phosphogypsum” (PG). In addition, the 24% of PR is processed directly into fertilizer without the generation of PG, whereas the remaining 5% is converted directly into various other products. The annual production of P2O5 in the form of PA is more than 30 million tons. iii) Most of the phosphoric acid produced in step (ii) (75–90%) is subjected to further chemical processing to convert it into fertilizer. The fertilizer products so derived from PA thus account for some 55–60% of total phosphate rock production. Of the remaining 10–25% of PA produced in step (ii), about one‐half is processed into animal feed supplements and the other half into a variety of other products. The production of PA for the manufacture of phosphate fertilizers usually use sedimentary phosphate rock as raw material, which contains generally enhanced concentrations from U‐series radionuclides; about two orders of magnitude in relation to unperturbed soils. This implies huge fluxes of radionuclides along the production process, and the generation of wastes and by‐products enriched in natural radionuclides. For that reason, the evaluation of the occupational, public and environmental radiological implications of this industrial activity is needed. This evaluation has been performed for the authors in a large fertilizer chemical industrial complex, located at Huelva town (SW of Spain), where sedimentary phosphate rock has been processed since 1965 to December 31, 2010, generating annually about 2.5 million tons of phosphogypsum waste (PG), which has been stored in big stacks (around 1000 ha and 100 million tons of PG are stored at this repository). The fluxes of the radionuclides of interest along the production process and the effective doses received by the workers have been determined. In addition, the radioecological environmental impact associated to the waste management strategy has been also evaluated. Phosphoric Acid Industry - Problems and Solutions102 2. Phosphoric acid production at Huelva 2.1. Description of the PA production At Huelva five phosphoric acid plants were working, consuming annually around 1.5 million tons of phosphate rock, and producing 0.5 million tons of PA (expressed as P2O5), and 2.5 million tons of PG. PG is an unavoidable by‐product in the production of PA by the sulphuric “wetacid“ method, where 5.5 tons of PG per ton of P2O5 are produced. The process for obtaining the phosphoric acid from the phosphate rock can be described schematically by the following chemical reaction [3]: Ca 3 ( PO 4 ) 2 + 3H 2 SO 4 → 2H 3 PO 4 + 3CaSO 4 + 48.9 kcal (1) In the Huelva phosphoric acid plants the fluorapatite was mainly used as raw material, which in the process conditions induce the production of the phosphogypsum in the di‐hydrate form, according to the following general reaction [3]: Ca 10 ( PO 4 ) 6 F 2 CO 3 Ca + 11H 2 SO 4 + 21H 2 O → 6H 3 PO 4 + 11CaSO 4 ·2H 2 O + 2FH + CO 2 (2) The industrial process can be divided into four different steps (Figure 1): (1) grinding and conditioning of the phosphate rock, (2) dissolution of the phosphate rock with diluted sulphuric acid (60%), (3) filtration, or PG separation from phosphoric acid (liquid fraction), and (4) washing of PG by water. The grinded PR is introduced into the digesters where the phosphate rock is attacked (dissolved), and a pulp is obtained containing mainly PA in solution, and solid PG. This pulp is filtered and PA (24% P2O5) and PG are separately obtained. Then, three successive backwashes are done in order to extract the remaining PA still contained in the phosphogypsum. The first washing is carried out with PA at 12% P2O5 where phosphoric acid with 27% P2O5 is obtained. The second washing is done with 5% P2O5 to produce 12% P2O5 which is used in the first washing. Thirdly, Figure 1. Industrial process of PA production. Occupational, Public and Environmental Radiological Impact Caused by the Phosphoric Acid Industry... http://dx.doi.org/10.5772/intechopen.68567 103 a final washing is performed with hot water to produce 5% P2O5, which is used in the second washing. Finally, the 27% P2O5 (production acid) is concentrated by evaporation for obtaining commercial acid (54% P2O5), since it is the normal concentration needed for the fabrication of the most demanded phosphate fertilizers: monoamonium phosphate (MAP), diamonium phosphate (DAP), and complex fertilizers (NPK). 2.2. Description of PG piles Although during the last years research and attempts have been done for valorization of the PG, the use of the generated one in the Huelva factories has been until now quite limited and mostly in agriculture as a soil amendment [4]. Consequently, due to the lack of any market for this compound, the great majority of the generated PG in Huelva has historically been considered as a waste with the following management policy: (a) During the first 30 years of production (until December 1997), 20% of the PG generated was released directly into the Odiel Channel of the Huelva estuary, whereas the remaining 80% was transported from the phosphoric acid production plants in suspension with sea water to a neighboring marshland area (2 km away from the plants and located in the confluence of the mouths of the Odiel and Tinto rivers), where it was disposed of by means of decantation with the transporting waters draining directly into the estuary [5, 6]; (b) since beginning 1998, all the PG produced in Huelva has been stored in the PG piles following the OSPAR convention [7, 8]. The PG was transported to the disposal area with fresh water, which was reintroduced in the industrial process following a closed cycle, in order to prevent any impact on the estuarine ecosystem [9]. Since December 31, 2010, the production plants of phosphoric acid have been closed, and, as a consequence, the production of PG has been halted. The legacy from these plants involves a major area where millions of tons of PG have been accumulated, and can be considered as formed by four different areas called Zone 1, Zone 2, Zone 3 and Zone 4, as it is shown in Figure 2. Zone 1 is a 450 ha sector and it was the first area submitted to regeneration work. It is calculated that about 12 × 106 tons of PG, including unknown amounts of urban wastes and mining wastes, were released in this sector. Restoration tasks were performed during 1990 by the Andalusia Regional Government in order to minimize both the visual and the environmental impact associated to the different wastes that were released there. To do that, a soil cover of about 30 cm average thickness and a vegetal coverage were added above the naked PG surface. Furthermore, several tenths of soil hills (1.5 m high) were scattered above the soil cover layer in order to allow small tree species to grow. In Zone 2 (270 ha), the wastes were released until 2010 inside the water recirculation system. In this zone, the gypsum stacks reached 15 m in height above the natural ground, and it continued to grow following a pyramid shape. As the height increases, the sides of the pyramid are covered with a soil layer and a vegetal coverage, in order to minimize the visual impact. Zone 3 (180 ha) is close to Zone 2. It is only conformed by PG, without any soil coverage. Phosphoric Acid Industry - Problems and Solutions104 Zone 4 was submitted to a similar restoration process than Zone 1. More detailed, different kinds of industrial and urban wastes were added above the PG: in the first place, a building debris layer was added; thereafter, different kinds of industrial wastes were added and finally, a soil layer like that of zone 1 for different vegetable species can grow on this cover. The total thickness of the coverage (including the three layers: wastes, debris, and soil) is more than 1 m. Furthermore, one of the sectors contained within the PG stacks was contaminated some years ago by the radioactive ashes produced during the Acerinox Steel factory accident in 1998. An industrial 137Cs radioactive source was accidentally melted with iron wastes in the steel factory. These wastes were treated in a purifier plant in the industrial complex of Huelva. Finally, the wastes and a certain amount of their ashes were released in Zone 4 and mixed with the PG. As a consequence of the releases, the Spanish National Wastes Enterprise (ENRESA) sealed the sector and restoration works were developed consisting in a cover with a layer of clay to minimize permeability and migration of radioactive cesium. Finally, different vegetal species were planted in the sector, and a vigilance program was established. Besides, from Zone 3, it has been possible to observe liquid leakages (filtrations), mostly with a certain flow, into the Tinto River and adjacent marshlands, while from Zone 2, these leakages are clearly minor in number and diffused after overflowing the perimeter channel barrier. Figure 2. Aerial photograph of the area of the Tinto river marshes. (1) Settling ponds, dumping area of FY; (2) regulating reservoir, (3) perimeter channel, and (4) pumping station. Occupational, Public and Environmental Radiological Impact Caused by the Phosphoric Acid Industry... http://dx.doi.org/10.5772/intechopen.68567 105 Currently, there is an environmental plan under study in order to restore Zones 2 and 3; for the total application of which, a duration of 10 years has been estimated. It is expected that the planned restoration should solve the environmental impact on the neighboring areas. 2.3. Samplings 2.3.1. Phosphoric acid plants In relation to the studies made inside the fertilizer plants, several sampling campaigns have been developed in the phosphoric acid factory located at Huelva (Spain), with the aim of analyzing the distribution [10–12] and levels of radionuclides in the materials involved in its production and evaluating the occupational, public and environmental radiological impact of this factory. Solid, liquid and air‐filter samples were collected in: (a) the four steps of the PA process: (1) milling and grinding, (2) acid attack or digestion, (3) filtration and washing, and (4) PA concentration; and in (b) the plants devoted to the production of monoamonium phosphate (MAP) and diamonium phosphate (DAP) fertilizers. The solid samples included several matrices, from the phosphate rock until commercial phosphoric acid (54% P2O5). The water samples were collected at the regulating reservoir associated to the big active pile where the PG was finally stored until 2010. This water is used for the phosphogypsum pumping into the ponds, and it was collected over a year at a rate of one sample per 2 months, in order to evaluate the possible temporal evolution in its radionuclide contents. In order to estimate the committed effective doses received by the workers of the PA, MAP and DAP plants due to inhalation, aerosol filters were collected from different representative places of the plants. The aerosol collections were performed with Andersen PM10 high‐vol‐ ume samplers. The external radiological effective doses were measured by using a radiation monitor Universal Monitor (UMo) model LB 123. The “Universal Monitor” (UMo), manufactured by Berthold, is a monitor designed specifically for low dose rates. It is equipped with a probe which works on proportional mode and allows the measurement of both dose rate and integrated dose. 2.3.2. Phosphogypsum stacks The research groups involved in the writing of this chapter have been performing research and monitoring studies associated to the PG stacks and their neighboring environmental compartments since the end of the 1980s. Several sampling campaigns have been done inside the PG stacks in order to characterize the material accumulated, to analyze the spatial degree of variation in the levels of the radionuclides associated [4, 13], and to evaluate its radiological impact through external radiation, inhalation of particle matter and radon emanation. And also a detailed sampling campaign was done after the halting of the PG production in order to evaluate the radioactive content of the liquid leakages of the piles and the associated formed efflorescences [14]. Phosphoric Acid Industry - Problems and Solutions106 In addition, dozens of sampling campaigns have been performed in the PG neighboring environments as are summarized in the following paragraphs. In this sense, more than 10 sampling campaigns have been performed from the end of the 1980s until now in the estuaries of the Odiel and Tinto rivers to evaluate the temporal evolution of the environmental radioactive contamination generated by the PG piles and the effluents from fertilizer plants. The majority of these sampling have involved the collection of waters (dissolved and particulate matter fractions), and superficial sediments, although special sampling campaigns were performed, for example, for the collection of several sediment cores in the estuaries to evaluate its possible use as historical archives of the radioactive contamination in the area [15]. In addition, sediments were collected in order to perform speciation studies [16]. In all the cases, several actions were taken in order to preserve the integrity and quality of the samples for radionuclide determinations (acidification of the waters after filtration, drying at room temperature of the sediments in order to avoid changes in the forms of association of the radionuclides to their different phases, etc.). On the other hand, in addition to the studies carried out in the estuaries mostly with surveillance purposes, other sampling campaigns were performed in order to carry out more pure radioecological studies. In this sense, several sampling campaigns were performed for the collection of vegetation in the marshes surrounding the PG piles (halophytes plants) and the determination of natural radionuclide transfer factors (TFs) [17–19], and the collection and analysis of other biota samples (shellfish, shrimps, etc.). 2.4. Measuring techniques The radioactive characterization of the great majority of the samples collected either in the production plants, in the PG stacks or in the neighboring environmental compartments (PG, waters, sediments, soils, efflorescences, vegetation, biota, etc.) have been performed by applying two independent techniques: both gamma‐ray and alpha‐particle spectrometry. Gamma measurements in solid samples (PG, soils, sediments, biota, etc.) were carried out using along the time several gamma spectrometry systems, most of them based in High‐ Purity Germanium (HPGe) detectors, although in some specific cases when the amount of material was limited a well‐Ge detector was used. The calibration of the gamma systems were performed following procedures as the described in Ref. [20], applying when was needed corrections due to self‐absorption effects. In the same solid samples, as well as in waters, Th‐isotopes, U‐isotopes and 210Po activity concentrations were determined by alpha‐particle spectrometry after the application of validated radiochemical methods, such as the described in Ref. [21], for the sequential isolation of the elements of interest. Alpha‐spectrometric systems formed by independent chambers working in parallel and equipped with 450 mm2 PIPS detectors were used for the measurements. After U and Th were isolated from the matrix under analysis, they were independently adapted for measurement by electrodepositing them onto stainless steel discs by applying the method of Hallstadius [22], whereas Po was self‐deposited onto silver discs of 1 inch diameter using Flynn’s (1968) method. Occupational, Public and Environmental Radiological Impact Caused by the Phosphoric Acid Industry... http://dx.doi.org/10.5772/intechopen.68567 107 Along the 35 years of measurements in the area, other techniques have been also used for specific radionuclide determinations: U and Th elemental determinations, for example, have been performed in waters, PG and sediment samples by ICP‐MS. 226Ra and 210Pb determinations in waters have been performed after radiochemical isolation by using the Liquid Scintillation Counting (LSC) technique or low‐background gas‐flow proportional counters; 222Rn determinations have been carried out on the PG stacks using Rn monitors, etc. All the procedures used for radionuclide determination have been periodically validated through the regular participation in intercomparison exercises organized at national (Spanish Security Council) and international (IAEA) level. Additionally, different quality control (QC) procedures were routinely applied: performance of replicate analysis, measurement of blank samples, measurement of certified reference materials, regular control of system’s background, etc. 2.5. Radioactive characterization 2.5.1. Phosphoric acid plants The sedimentary phosphate rock treated for the production of phosphoric acid is clearly enriched in radionuclides from the uranium series. They are at least 50 times higher than in representative unperturbed soils worldwide [23]. In addition, in the PR all members of the uranium series are in secular equilibrium (Table 1), as expected due to the fact that the material does not experiment any radionuclide enrichment during the physical processes applied before its digestion. On the other hand, the activity concentrations of the radionuclides belonging to the 232Th chain in the treated phosphate rock are quite reduced. During the digestion step, the first clear evidence of different behavior that the analyzed radionuclides from the U series show in the process is observed. A clear fractionation of the radionuclides contained in the mineral is produced between the liquid and solid fractions from the pulp samples collected from the digesters. The liquid fractions, corresponding mainly to the phosphoric acid formed at this step, are clearly enriched in uranium, whereas the concentrations of 230Th, 226Ra, and 210Pb are very much lower or even negligible (this is the case of 226Ra). On the contrary, solid samples contain the major proportion of the 230Th, 226Ra, and 210Pb originally present in the phosphate rock, whereas the uranium isotopes concentrations are slightly lower. This solid fraction is mostly composed of the PG formed in reaction to the phosphate rock with sulphuric acid. However, it may also contain a proportion of nonattacked phosphate rock and some phosphoric acid occluded between the PG grains and not separated from the liquid samples. The results obtained in the analysis of the samples collected in the filtration step allowed the confirmation of the different behavior of the uranium isotopes and their daughters previously drawn. By observing the data shown in Table 1, we can affirm that most of the uranium tends to be associated to the phosphoric acid fraction, whereas the majority of 230Th, 226Ra, and 210Pb tends to be associated to PG. These conclusions are evident by observing the obtained activity concentrations measured in the phosphoric acid in relation to the P2O5 concentration. The U concentration decreases in the PG samples according to their successive washings, which indicates that the remaining P2O5 of the PG is sequentially removed from the different Phosphoric Acid Industry - Problems and Solutions108 washings. On the contrary, the concentrations of 230Th, 226Ra, and 210Pb remain practically constant along the successive washings, showing this fact that this type of radionuclides are very hard bound on the PG fraction. A clear linear correlation between both U and P2O5 concentrations was obtained by using the different materials involved in the phosphate fertilizer production process, with a slope of 35 ± 2 Bq kg−1 238U/% P2O5. This result demonstrate that the uranium follows the same route that the PA along the full fertilizer production process. Another conclusion of these studies was that a high fraction of the uranium series radionuclides (mainly U and 230Th) input in the P2O5 manufacturing arrives finally into the environment by the use of phosphate fertilizers in the agriculture. 2.5.2. Phosphogypsum stacks The activity concentrations measured in the materials stored in the PG piles reflect the radionuclides fractionation in the PA manufacturing, being found for PG that the levels are in the sequence: 226Ra ≈ 210Pb ≈ 210Po > 230Th > 234U = 238U. Activity concentrations of 500–700 Bq kg−1 for both 226Ra and 210Pb, and 80–200 Bq kg−1 for 234U and 238U have been determined along the PG 238U234U230Th 226Ra 210Pb 232Th 228Th 228Ra PR 1653 ± 21 1405 ± 504 1600 ± 87 1565 ± 124 1578 ± 95 26 ± 5 20 ± 3 21 ± 1 22% P2O5870 ± 50 870 ± 50 95 ± 4 3.0 ± 0.4 74 ± 14 53 ± 11 1.7 ± 0.4 <1.8 Cake dig. L 1213 ± 186 1197 ± 189 305 ± 104 5 ± 1 73 ± 11 4 ± 2 5 ± 2 4 ± 4 Cake dig. S 490 ± 61 490 ± 61 650 ±125 607 ± 146 660 ± 185 15 ± 1 11 ± 2 12 ± 3 Pulp cake Solid 1340 ± 90 1330 ± 90 425 ± 78 4.0± 0.4 60 ± 12 6.5 ± 1.4 4 ± 0.5 <1. 0 Pulp cake liquid 150 ± 30 450 ± 30 750 ± 30 590 ± 25 590 ± 120 16 ± 2 11 ± 2 9. 4 ± 1.1 27% P2O51070 ± 110 1090 ± 110 230 ± 30 5,6 ± 0.5 78 ± 15 9.8 ± 1.8 3.9 ± 0.5 <1.8 22% P2O5870 ± 50 870 ± 50 95 ± 4 3.0 ± 0.4 74 ± 14 53 ± 11 1.7 ± 0.4 <1.8 12% P2O5470 ± 40 470 ± 40 80 ± 10 6,1 ± 0.5 <225 6.0 ± 1.5 <1.7 <1.9 5% P2O5290 ± 20 290 ± 20 4,2 ± 0.3 1,8 ± 0.3 <135 0,17± 0.06 <1.0 <1.5 Gypsum 425 ± 152 439 ± 143 775 ± 47 635 ± 39 620 ± 16 26 ± 8 10 ± 3 10 ± 1 Sludges L 1675 ± 587 1670±608 750 ± 707 6 ± 2 65 ± 27 14 ± 12 11 ± 7 1.7 ± 0.1 Sludges S 1070 ± 226 1065±233 1455±771 2805±2114 1660±339 20 ± 11 21 ± 15 41 ± 33 32% P2O51300 ± 70 1320 ± 70 NM 3.6 ± 0.3 <135 NM 6.5 ± 0.4 <0.9 54% P2O51830 ± 180 1810 ± 180 NM 7.9 ± 0.5 109 ± 14 NM 13.2 ± 1.4 <1.0 Note: Uncertainty = standard deviation, L = liquid fraction, S = solid fraction, NM = not measured. Table 1. Activity concentrations (mean values in Bq kg−1) obtained for the samples collected along the milling, digestion, filtration, washing, and acid concentration steps. Occupational, Public and Environmental Radiological Impact Caused by the Phosphoric Acid Industry... http://dx.doi.org/10.5772/intechopen.68567 109 The peculiarities of the estuary formed by the confluence of the Tinto and Odiel rivers from the radioactive point of view, with relatively well‐defined sources of several radionuclides from the uranium series, has converted the area in a natural laboratory where different radioecological studies have been and can be performed. In this sense, determinations of distribution coefficient factors (kd), and of transfer factors soil to plants (TF), have been performed. In addition, this estuarine ecosystem and the huge amount of radioactive data generated in it, has served for the historical development of numerical hydrodynamic models to explain and predict the dispersion of the radioactive pollution and to gain in this way a lot of information about the environmental behavior of different radionuclides in estuarine compartments [29]. These models solve water circulation due to tides and river stream flows, include uptake/release reactions of radionuclides between the dissolved phase and bed sediments in a dynamic way (using kinetic transfer coefficients) and allow to evaluate the relative significance of the different radionuclides sources into the estuary as well as the independent effect of the two components of water circulation (tides are river flows) on radionuclide dispersion patterns. Quite recently [19], a detailed study has been performed analyzing natural radionuclide concentrations in three species of halophytes plants growing in salt marshes from the Tinto estuary. The results of this work have shown that, (a) natural radionuclide concentrations (specially the U‐isotopes) in the Tinto salt‐marsh sediments are one order of magnitude higher than those determined in unpolluted salt marshes taken as a reference, and (b) these radionuclide enhancements are reflected in the different organs of the plants having increased concentration of these radionuclides. The transfer factor (TF) of the most polluted radionuclides (U‐isotopes and 210Po) in the Tinto salt marshes are one order of magnitude higher than in the unpolluted reference site indicating that the fraction of each radionuclide in the sediment originating from the pollution is more available for the plants than the indigenous fraction. This last conclusion allows indicating that the plants of the salt marshes are unhelpful as bioindicators or for the phytoremediation of radionuclides. In this work additional information was obtained by analyzing the internal distribution of the natural radionuclides in the plants, by distinguishing among its main organs (roots, stems, and leaves). In representative aliquots of living biota that can be found in the Huelva estuary, natural radionuclide determinations have been also performed. In particular, shrimps and different shellfish species collected in the Huelva estuary have been analyzed after 1998, and it is found that the levels of 210Po, 210Pb, U‐isotopes, and 230Th are similar to the determined ones for the same species in aliquots collected in an unperturbed estuary located nearby, and to the determined ones for the same species in unperturbed estuarine ecosystems distributed over the world. This fact indicates that the radioactive pollution existing in the Huelva estuary, which is diminishing since 1998 to levels near to background nowadays, have a quite or very limited impact in the upper levels of the trophic chain. If in addition, we have in consideration that (a) the possible interaction of the radioactive pollution existing in the estuary with continental waters is limited to a possible interaction with an aquifer located below the phosphogypsum piles that is saline and consequently its waters have no use in agriculture and as a source of drinking water, and (b) no detectable increments in particulate matter and 222Rn activity concentrations have been observed in the vicinity of the PG piles, we can conclude indicating that the public radiological impact associated to the radioactive Phosphoric Acid Industry - Problems and Solutions116 pollution of the Huelva estuary and to the presence of the PG piles is extremely limited—lower than 20 µSv yr−1, being adopted for this estimation as extremely conservative assumptions. Acknowledgements Parts of this chapter are reproduced from the authors’ previous publications (Refs. [10, 11, 14], among others). This work was partially supported by the Ministry of Economy and Competitiveness of Spain through the research project with Ref.: CTM2015‐68628‐R. Author details José Luis Guerrero‐Márquez1, Fernando Mosqueda Peña1, Juan Mantero2, Guillermo Manjón2, Rafael García‐Tenorio2 and Juan Pedro Bolívar1* *Address all correspondence to: boliv[email protected] 1 Department of Integrated Sciences, Campus El Carmen, University of Huelva, Huelva, Spain 2 Department of Applied Physics II, University of Seville, Seville, Spain References [1] Northolt AJG, Sheldon RP, Davidson DF, editors. Phosphate Deposits of the World. Vol. 2: Phosphate Rock Resources. Cambridge, UK: Cambridge University Press; 2005. p. 600 [2] International Fertilizer Industry Association. Phosphate production in the new economics. Presentation to Joint IAEA‐FIPR Phosphate Workshop. Bartow, Florida. 2006 [3] Fertiberia S.A. Documentation on the Industrial Process at the Huelva Phosphoric Acid Production Plant. 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