This study analyzed the activity concentrations of various radionuclides in irrigation water, rice components, and corresponding soil samples from eleven paddy fields, revealing significant findings with potential environmental and health implications. The soil exhibited high levels of activity concentrations ranging from 350 to 829, 12.4 to 41.2, and 18.5 to 60.3 Bq/kg, with mean values of 609, 31.1, and 45.0 Bq/kg for ⁴⁰K, ²²⁶Ra, and ²³²Th respectively. Additionally, 12 soil samples from two paddy fields showed ¹³⁷Cs activity concentrations of 5.6 ± 1.3 Bq/kg. The rice plant roots accumulated the highest percentages of total activity concentrations for ²²⁶Ra, ²³²Th, and ¹³⁷Cs, ranging from 76–86%, while only 1.1–10.0% were found in the un-hulled grain. For ⁴⁰K, activity concentrations were distributed among the root (23%), stem (32%), leaf (35%), and un-hulled grain (10%). The mean activity concentrations were 99 ± 12, 0.49 ± 0.09, 0.43 ± 0.12, and 0.10–0.31 Bq/kg for ⁴⁰K, ²²⁶Ra, ²³²Th, and ¹³⁷Cs for un-hulled rice grain, respectively. Transfer factors (TFs) from soil to un-hulled rice grain were calculated as (1.21–2.86) × 10⁻¹ for ⁴⁰K, (0.07–0.11) × 10⁻¹ for ²³²Th, (0.11–0.29) × 10⁻¹ for ²²⁶Ra, and (0.16–0.61) × 10⁻¹ for ¹³⁷Cs. Notably, significant negative correlations were observed between TFs and soil concentrations for ⁴⁰K (r = 0.92, p < 0.001, n = 11) and ²²⁶Ra (r = 0.98, p = 0.026, n = 4), suggesting that macronutrients in soil solutions may inhibit the linear transfer of natural nuclides from the soil solution to rice plants.

Soil samples were collected from a college campus in Taiwan to measure the levels of radionuclides, contributing to the sustainable management of campus environments. A high-resolution HPGe gamma spectrometry system was utilized to measure the activity concentrations of natural radionuclides (²²⁶Ra, ²³²Th, and ⁴⁰K) and artificial radionuclide (¹³⁷Cs). The activity concentrations of ¹³⁷Cs were not detected in the campus soils, suggesting that artificial radionuclides did not contaminate the soil, supporting sustainable soil quality. However, the average concentrations of ²³²Th and ⁴⁰K with mean values of 53.4 ± 5.1 and 504.5 ± 75.4 Bq/kg dw were higher than the global soil average of 45 and 420 Bq/kg dw, respectively. Meanwhile, the average concentration of ²²⁶Ra with a mean value of 30.1 ± 3.0 Bq/kg dw was similar to the global soil average of 32 Bq/kg. The average outdoor absorbed gamma dose rate (D_ex) and annual effective doses (AED_ex), with a mean of 67.2 nGy/h and 82.4 μSv/y, were found to be higher than the average world levels of 57 nGy/h and 70 μSv/y, respectively. Despite these findings, the radium equivalent activity Ra_eq and external hazard index H_ex, with average values of 145.2 Bq/kg and 0.39, respectively, were below the recommended limit values of 370 Bq/kg and 1.0, respectively. This study provides useful information on the background radioactivity of the study campus, which is crucial for developing sustainable strategies to ensure a safe and healthy environment, indicating that there are no radiological hazards in the soil.

This study analyzes the concentration of radioactive material in the soil near the Maanshan nuclear power plant (NPP). Out of the thirty samples, only one sample was found to have ¹³⁷Cs radioactivity measuring 2.58 Bq/kg. The activity concentrations were 77.2–517.7 Bq/kg, 3.9–31.6 Bq/Kg, and 5.3–39.1 Bq/kg, respectively, with mean values of 344.4 Bq/kg, 18.6 Bq/kg, and 26.5 Bq/kg for ⁴⁰K, ²²⁶Ra, and ²³²Th, respectively. These levels are lower than the global average of soil activity concentrations. The activity concentrations varied, with the highest levels being 7–8 times greater than the lowest levels. Clay content had a positive correlation and sand content had a negative correlation with ⁴⁰K, ²²⁶Ra, and ²³²Th activity concentrations. The activity concentrations followed a normal distribution for ⁴⁰K, ²²⁶Ra, and ²³²Th. The activity ratios for ²³²Th/²²⁶Ra, ⁴⁰K/²³²Th, and ⁴⁰K/²²⁶Ra were 1.43 ± 0.22, 13.1 ± 1.9, and 18.8 ± 4.1, respectively, and ratios show light minerals in the soils. The average values for external hazard indices (H_ex) and radium equivalent activity (Ra_eq) were 0.22 Bq/kg and 83.0 Bq/kg, respectively, both of which are below the recommended limit values of 1.0 Bq/kg and 370 Bq/kg, respectively. The outdoor absorbed dose rate (D_Rex) and annual effective dose equivalent (AED_ex) were 39.0 nGy/h and 47.8 μSv/y, respectively, both of which are lower than the global soil average of 59 nGy/h and 70 μSv/y, respectively. These results indicate that local residents and tourists are not at significant risk of radiological hazards from the soil. The soil activity concentrations can serve as a baseline for continuous monitoring, even after the Maanshan NPP is decommissioned in 2025.

This study investigated the distribution of copper in sediment dissolved and particulate organic matter (DOM and POM) based on their size. The DOM and alkaline extracted POM (AEOM) were separated into five size fractions using a cross-flow ultrafiltration (CFUF) system. The results showed that Cu mass was mainly distributed in the low molecular weight (<1 kDa, LMW) fraction of the DOM with an average range of 78.1–83.1%. Conversely, the high molecular weight (1 kDa–0.45 μm, HMW) AEOM fraction had a higher distribution of Cu mass with an average range of 92.6–93.3%. The Cu and AEOM binding affinity ratios (CuBA_AEOM) ranged from 17.0 to 149.6 μmol/g-C in site-1 and from 20.6 to 143.7 μmol/g-C in site-2. The HMW CuBA_AEOM ratios were significantly higher than the LMW ratios. The Cu and DOM binding affinity ratios (CuBA_DOM) ranged from 5.6 to 358.6 μmol/g-C and 17.2 to 126.6 μmol/g-C in site-1 and site-2, respectively. However, the LMW CuBA_DOM ratios were significantly higher than the HMW ratios. Optical indices suggested that the AEOM had more aromaticity and terrestrial and allochthonous contributions than the DOM. The optical indices were significantly correlated with the CuBA_AEOM ratios but weakly correlated with the CuBA_DOM ratios. Sediment exchange between POM and DOM may affect copper distribution. DOM has a low-molecular-weight composition, while POM retains high-molecular-weight organic matter.

This study investigated the distribution and binding affinity of dissolved copper (Cu) and organic carbon (OC) in size-fractioned dissolved organic matter (DOM) in a constructed wetland (CW). Two sites were studied: one at the inflow (P-1) and one within the wetland (P-2). The DOMs (<0.45 μm) were separated into six size fractions using a cross-flow ultrafiltration system. In the wetland (P-2), the concentrations of dissolved organic carbon (DOC) increased while the concentrations of Cu decreased. The high molecular weight fraction (1 kDa–0.45 μm, HMW) contained most of the OC mass (57.4–71.2% averages). On the other hand, Cu was almost equally distributed in HMW and low molecular weight fractions (<1 kDa, LMW) with mean HMW percentages of 50.3–51.3%. The mean Cu binding affinity to DOM ratios (CuBA_DOM) was 74.9 ± 24.0 μmol/g-C at site P-1 and 17.3 ± 2.6 μmol/g-C at site P-2. The CuBA_DOM ratios were decreased in wetlands of bulk and size-fractioned DOM (p < 0.001 to p = 0.073). The SUVA₂₅₄ values for bulk DOM solution were 2.54 ± 0.15 and 1.68 ± 0.18 L/mg-C/m, and humidification index (HIX) values were 1.74 ± 0.16 and 2.09 ± 0.19 for sites P-1 and P-2, respectively. Optical indicators suggested that the wetland process decreased aromaticity but increased the humification degree of DOM. Furthermore, the CuBA_DOM ratios positively correlated with SUVA₂₅₄ and HIX within the constructed wetland DOM but not in the influent DOM. Understanding the Cu distribution and binding affinity to size-fractioned DOM makes it possible to develop strategies to mitigate the potential effects of copper pollution in wetlands.