Nuclear Institute for Agriculture and Biology, Jhang Road, Faisalabad, Pakistan.
Environ Sci Pollut Res Int. 2012 Sep;19(8):3327-38. doi: 10.1007/s11356-012-0850-z. Epub 2012 Mar 31.
BACKGROUND, GOAL, AND SCOPE: Natural radioactivity in phosphate rock (PR) is transferred to phosphate fertilizer (PF) during the manufacturing process of the PF. The continuous addition of the PF to the cultivated soil accumulates the radionuclides in the land and increases the level of radioactivity in the soil. The purpose of the present study was to investigate the enhanced level of accumulated radioactivity due to the continuous addition of the PF in the farmlands of Nuclear Institute of Agriculture and Biology (NIAB) at Faisalabad in Pakistan. The selected study area consisted of the highly fertilized farmlands and an unfertilized barren land of the NIAB.
The understudy area is very fertile for the growth of various types of crops; therefore, four agricultural research institutes have been established at Faisalabad and NIAB is one of those. The NIAB has developed various research farmlands at different places in Pakistan. The crop yield has been increased by adding various fertilizers in the farmlands. The addition of the PF accompanied with the radionuclides enhances radioactivity in the fields. Human being is exposed directly or indirectly to this radiological hazard. A prolong exposure may become a cause of health risk.
The area of study consisted of three types of lands: the land under cultivation for the last 40 and 30 years called Site 1 and Site 2, respectively, and the barren land was called Site 3. A total of 75 soil samples were collected within the crop rooting zone (up to 25 cm deep) of the soil of the NIAB farms. The samples were dried, pulverized to powder, sealed in plastic containers, and stored to achieve equilibrium between (226)Ra and (222)Rn. Activity concentrations of the radionuclides (238)U ((226)Ra), (232)Th, and (40)K in soil samples were determined by using a high resolution gamma ray spectrometry system, consisting of an high purity germanium detector coupled through a spectroscopy amplifier with a PC based MCA installed with Geni-2000 software.
The measured activity concentration levels of (40)K were 662 ± 15, 615 ± 17, and 458 ± 20 Bq kg(-1), (226)Ra were 48 ± 6, 43 ± 5, and 26 ± 4 Bq kg(-1), and that of (232)Th were 39 ± 5, 37 ± 5, 35 ± 5 Bq kg(-1), respectively, in the soil of the Sites 1, 2, and 3. Gamma dose rate 1 m above the soil surface was 55, 51, and 40 nGy h(-1) from Sites 1, 2, and 3, respectively. External dose rates in the rooms constructed of the bricks made of the soil from Sites 1, 2, and 3 were 161, 149, and 114 nGyh(-1), respectively.
Activity concentration values of (40)K and (226)Ra in the soil of Sites 1 and 2 were higher than that in the soil of Site 3. The relative rise of (40)K was 43 % and 34 % and that of (226)Ra was 85 % and 65 % respectively in these sites. Activity concentrations of (232)Th in all these sites were in the background range. Gamma dose rate 1 m above soil surface of Sites 1 and 2 was 40 % and 30 % respectively higher than that from the soil of Site 3. The rise in activity of (40)K and (226)Ra and gamma dose from the Site 1 was greater than that from the Site 2. The least activity and dose were observed from the Site 3. Gamma dose in the dwellings made of fertilized soil bricks of Site 1 and Site 2 were respectively calculated to be 41 % and 32 % higher than that in the abodes made of unfertilized soil bricks of Site 3.
Activity concentrations of (226)Ra and (40)K were observed to be enhanced in the fertilized farmlands of the NIAB. Outdoor and indoor gamma dose as radiological hazard were found to be increasing with the continuous addition of PF in the understudy farmlands.
It is recommended that naturally occurring radioactive metal should be removed during the process of manufacturing of the PF from the PR. PROSPECTIVE: The rise in radioactivity in the farmlands due to the addition of the PF can be a source of direct or indirect exposure to radiation that may enhance cancer risk of the exposed individuals.
本研究旨在调查由于在巴基斯坦核农业与生物研究所（NIAB）的农田中持续添加磷肥而导致的累积放射性增强水平。
研究区由高度肥沃的农田和 NIAB 的未施肥荒地组成。该地区非常适合各种类型的作物生长；因此，在费萨拉巴德建立了四个农业研究所，NIAB 是其中之一。NIAB 在巴基斯坦的不同地方开发了各种研究农场。通过在农田中添加各种肥料来提高作物产量。PF 与放射性核素一起添加会增加田间的放射性。人类会直接或间接地暴露在这种辐射危害下。长期暴露可能成为健康风险的原因。
该地区的土壤样本采集自农田的作物根系区（深达 25 厘米），共采集了 75 个土壤样本。将这些样本干燥、粉碎成粉末，密封在塑料容器中，以达到（226）Ra 和（222）Rn 的平衡。土壤样本中的放射性核素（238）U（（226）Ra）、（232）Th 和（40）K 的活度浓度通过高分辨率伽马射线谱仪系统进行测定，该系统由与安装有 Geni-2000 软件的 PC 连接的高纯度锗探测器和光谱放大器组成。
结果表明， Sites1、2 和 3 的土壤中（40）K 的活度浓度分别为 662±15、615±17 和 458±20 Bq kg（-1），（226）Ra 分别为 48±6、43±5 和 26±4 Bq kg（-1），（232）Th 分别为 39±5、37±5 和 35±5 Bq kg（-1）。土壤表面上方 1 米处的伽马剂量率分别为 Sites1、2 和 3 的 55、51 和 40 nGy h（-1）。由 Sites1、2 和 3 的土壤制成的砖块建造的房间内的外部剂量率分别为 161、149 和 114 nGyh（-1）。
在 Sites1 和 2 的土壤中，（40）K 和（226）Ra 的活度浓度高于 Site3 的土壤。这些地点的（40）K 相对增加分别为 43%和 34%，（226）Ra 相对增加分别为 85%和 65%。所有这些地点的（232）Th 活度浓度均处于背景范围内。土壤表面上方 1 米处的 Sites1 和 2 的伽马剂量率分别比 Site3 的土壤高出 40%和 30%。Site1 的（40）K 和（226）Ra 活性和伽马剂量的上升大于 Site2。Site3 的活性和剂量最小。由 Site1 和 Site2 的施肥土壤砖建造的住宅中的伽马剂量分别计算为比 Site3 的未施肥土壤砖建造的住宅高 41%和 32%。
在 NIAB 的肥沃农田中观察到（226）Ra 和（40）K 的活度浓度增强。随着研究农田中 PF 的持续添加，室外和室内伽马剂量作为辐射危害正在增加。
在从磷矿制造磷肥的过程中，应去除天然放射性金属。
由于添加磷肥而导致的农田放射性增强可能成为直接或间接暴露于辐射的来源，这可能会增加暴露个体的癌症风险。
