Natural radioactivity in groundwaters around a fertilizer factory complex in South of Spain

doi:10.1016/S0969-8043(00)00380-8

Applied Radiation and Isotopes

Volume 55, Issue 3, September 2001, Pages 419-423

https://doi.org/10.1016/S0969-8043(00)00380-8 Get rights and content

Abstract

A study of the concentration of the U isotopes, ²²⁶Ra and ²³⁰Th in a groundwater system has been carried out. This aquifer, located in the provinces of Sevilla and Huelva, is the most important in the south of Spain having a surface area of $2500 km^{2}$ . The proximity of a fertilizer factory complex to this aquifer system is of particular concern given that it releases a significant part of its waste directly into the estuary of the Odiel and Tinto rivers, also storing a further part on the right bank of the Tinto river. Investigation has been made of the environmental impact of the fertilizer factory, either as a result of leaching of radionuclides from the phosphogypsum piles or otherwise as a result of intrusion of the Odiel and Tinto waters, both of which are in close contact with the aquifer. Results show U concentration in waters of this system around the phosphogypsum piles to be significantly higher than those in other areas of the same aquifer. The low ²²⁶Ra concentrations found in the same locations add support to the origin of part of the U in these samples.

Introduction

In southwest Spain, the presence of elevated levels of U, Th and ²²⁶Ra in rivers around a fertilizer factory complex has been established in several previous studies (Martı́nez-Aguirre and Garcı́a-León, 1991; Martı́nez-Aguirre et al., 1994). In particular, elevated concentrations of several natural radionuclides were found in water, suspended particles and sediments collected along the course of the Odiel and Tinto rivers. Contamination along the Odiel river was mainly attributed to solid and liquid waste discharges which were made directly into the course of this river at its estuary. This area is highly affected by tidal movement, with contamination migrating both up- and downstream. Tidal movements of the waters also lead to contamination of the Tinto river in areas close to the Odiel, these rivers having a common confluence into the Atlantic ocean. A smaller degree of contamination of the Tinto river has been observed to be due to storage of solid wastes (phosphogypsum piles). Concentrations as high as 950 and $2000 mBq / g$ of U and ²²⁶Ra were obtained in samples of phosphogypsum collected in 1988 (Martı́nez-Aguirre, 1991). These waste piles, connected by several small tributaries to the Tinto river, allow for the possibility of leachate entering the riverine system. However, the phosphogypsum piles are mainly calcium suphates and, complexed in this form, Ra is insoluble.

The groundwater system of interest is the most important in southwestern Spain, covering a surface area of $2500 km^{2}$ . This aquifer system, used both for consumption and irrigation water, may be affected either through intrusion by the elevated concentration levels of contaminants in the Odiel and Tinto rivers or by leachate from the phosphogypsum piles. Consequently, contamination of this aquifer system would affect a large region of Spain. Investigating the possible influence of the fertilizer manufacture, either by direct leaching of radionuclides from the phosphogypsum piles or intrusion of Odiel and Tinto river waters, is the main objective of this paper.

Section snippets

Samples and experimental methods

Twenty-two monitoring stations (see Fig. 1) have been selected across the Almonte-Marismas groundwater system in order to determine what influence the contamination produced by the fertilizer factory located in the Huelva estuary may have on the system. Some of the samples have been collected near the city of Sevilla in order to compare these with water samples collected around the fertilizer complex. Activity concentrations of the U-isotopes, ²³⁰Th and ²²⁶Ra have been measured in the samples.

Results and discussion

In Table 1, activity concentrations for U-isotopes, ²²⁶Ra and ²³⁰Th are presented together with the pH and temperature of the waters at the time of sampling. As seen, most samples have close to neutral pH, in the range 6.7–8. Exceptions are samples A11 and A14, with pHs of 8.8 and 8.5, respectively. The water temperatures ranged from 12°C to 18°C with no apparent trend between stations. Samples 7–22 were collected around the Tinto river channel and the phosphogypsum piles (see Fig. 1).

U-isotope

Conclusion

U concentration in samples of water from the Almonte-Marismas groundwater system, collected in the vicinity of solid waste (phosphogypsum) piles of the Huelva fertilizer factory, are significantly higher than those in other areas of the same aquifer. This could either result from U leaching from the phosphogypsum piles or intrusion of Odiel and Tinto river waters into the aquifer system. The low ²²⁶Ra concentrations found in the same locations are related to the high insolubility of calcium

Acknowledgements

We would like to thank Dr. R. Periañez from the University of Seville and Dr. M. Jurado from the University of Badajoz for their help in the sampling works.

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Analysis of the different source terms of natural radionuclides in a river affected by NORM (Naturally Occurring Radioactive Materials) activities
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This fact, together with the lower uranium content in the sediments of REG2 and REG3 relative to REG1, makes uranium remobilization seem unlikely to be responsible for the increased level in the surface water. The last hypothesis was the entry into solution of chemicals used as fertilizers (Alcaraz and Martinez, 2001) and their run-off into the Regallo river. In order to check this, the radionuclide content of a fertilizer commonly used in the area (an NPK type) was analyzed – both the total content and the water-soluble fraction (Table 5).
The present work studied the radioacitivity impact of a coal-fired power plant (CFPP), a NORM industry, on the water of the Regallo river which the plant uses for cooling. Downstream, this river passes through an important irrigated farming area, and it is a tributary of the Ebro, one of Spain’s largest rivers. Although no alteration of the ²¹⁰Po or ²³²Th content was detected, the ^234,238U and ²²⁶Ra contents of the water were significantly greater immediately below CFPP’s discharge point. The ²²⁶Ra concentration decreased progressively downstream from the discharge point, but the uranium content increased significantly again at two sampling points 8 km downstream from the CFPP’s effluent. This suggested the presence of another, unexpected uranium source term different from the CFPP. The input from this second uranium source term was even greater than that from the CFPP. Different hypotheses were tested (a reservoir used for irrigation, remobilization from sediments, and the effect of fertilizers used in the area), with it finally being demonstrated that the source was the fertilizers used in the adjacent farming areas.
Radioactivity and fluoride contamination derived from a phosphate fertilizer plant in Egypt
2009, Applied Radiation and Isotopes
The environmental pollution caused by the wastewater from a phosphate fertilizer plant in Egypt was investigated. The concentrations of radionuclides and fluoride in phosphate fertilizer (raw materials, end products and by-products) and other types of fertilizer samples were measured. The concentrations of these elements were also measured in environmental samples (water, sediment and plant) collected from the proximity of outlet of wastewater discharge pipes of the phosphate fertilizer company.
The fluoride concentration was ranged from 0.03 to 0.25 mg/g, 0.002 to 0.006 mg/g, 0.42 to 1.88 mg/g and 0.44 to 7.3 mg/l for phosphate fertilizer, other types of fertilizer, sediment and water samples, respectively. The activity concentrations of ²²⁶Ra were ranged from 244 to 1312 Bq/kg, 0.6 to 12.1 Bq/kg, 15.4 to 33.8 Bq/kg, 0.06 to 1.3 Bq/l and 8.9 to 17.3 Bq/kg for phosphate fertilizer, other types of fertilizer, sediment, water and plant samples, respectively. The ²³²Th activity concentrations were ranged from 0.7 to 24 Bq/kg, 0.7 to 14.5 Bq/kg, 10.4 to 19.3 Bq/kg, 0.02 to 0.16 Bq/l and 2.0 to 29.8 Bq/kg for these samples, respectively. Also, the ⁴⁰K activity concentrations were ranged from 2.1 to 1.4 Bq/kg, 2.1 to 5313 Bq/kg, 128 to 281 Bq/kg, 0.14 to 0.6 Bq/l and 686 to 977 Bq/kg for these samples, respectively. Low content of ¹³⁷Cs was determined in only two phosphate fertilizer samples (F2 and F3; mean 1.3 Bq/kg) and in most of sediment samples (with range 1.0–2.4 Bq/kg). The radium equivalent, as a radiation hazard index, was ranged from 284 to 1316, 9.6 to 432 and 47 to 70 Bq/kg for phosphate fertilizer, other types of fertilizer and sediment samples, respectively.
The results indicated that the wastewater polluted with fluoride produced from the phosphate fertilizer company may be affecting the environment. The radioactivity content measurements indicated that the environment may be slightly affected with low concentrations of ²²⁶Ra and ²³²Th isotopes due to the discharged wastewater from the phosphate fertilizer industry. On the other hand, the results of comparison studies for radioactivity concentrations are also presented and discussed.
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Natural radioactivity in groundwaters around a fertilizer factory complex in South of Spain

Abstract

Introduction

Section snippets

Samples and experimental methods

Results and discussion

Conclusion

Acknowledgements

Earth Planet. Sci. Lett.

Earth Planet. Sci. Lett.

Earth Planet. Sci. Lett.

J. Environ. Radioact.