Distribution, risk evaluation, and source allocation of cesium and strontium in surface soil in a mining city.

Radioactive nuclides cesium (Cs) and strontium (Sr) possess long half-lives, with 135Cs at approximately 2.3 million years and 87Sr at about 49 billion years. Their persistent accumulation can result in long-lasting radioactive contamination of soil ecosystems. This study employed geo-accumulation index (Igeo), pollution load index (PLI), potential ecological risk index (PEPI), health risk assessment model (HRA), and Monte Carlo simulation to evaluate the pollution and health risks of Cs and Sr in the surface soil of different functional areas in a typical mining city in China. Positive matrix factorization (PMF) model was used to elucidate the potential sources of Cs and Sr and the respective contribution rates of natural and anthropogenic sources. The findings indicate that soils in the mining area exhibited significantly higher levels of Cs and Sr pollution compared to smelting factory area, agricultural area, and urban residential area. Strontium did not pose a potential ecological risk in any studied functional area. The non-carcinogenic health risk of Sr to the human body in the study area was relatively low. Because of the lack of parameters for Cs, the potential ecological and human health risks of Cs was not calculated. The primary source of Cs in the soil was identified as the parent material from which the soil developed, while Sr mainly originated from associated contamination caused by mining activities. This research provides data for the control of Cs and Sr pollution in the surface soil of mining city.

[Changes and influence factors of soil matrix infiltration in Chinese fir plantations with different stand ages in northern Guangxi]. / æ¡‚åŒ—åœ°åŒºä¸åŒæž—é¾„æ‰æœ¨äººå·¥æž—åœŸå£¤åŸºè´¨å ¥æ¸—å˜åŒ–åŠå½±å“å› ç´ .

Soil matrix infiltration is an important pathway for plantations to obtain water, which affects ecological benefits and water conservation function of plantations. The changes of soil matrix infiltration and its influencing factors in different growth stages of Chinese fir plantations remain unclear. We measured soil matrix infiltration process using a tension infiltrometer in Chinese fir plantations (5, 8, 11, and 15 years old) of Beijiang River Forest Farm in Rongshui, Guangxi, and analyzed soil basic physicochemical properties to identify the dominant factors influencing soil matrix infiltration. The results showed that initial infiltration rate, stable infiltration rate, and cumulative infiltration increased with stand ages. The ranges of different stand ages were 141-180 mm·h-1, 109-150 mm·h-1, and 188-251 mm, respectively. The initial infiltration rate, stable infiltration rate, and cumulative infiltration were significantly positively correlated with soil capillary porosity, soil organic matter, soil water stable macroaggregate, sand content, and clay content, while negatively correlated with soil bulk density and silt content. Early thinning had a positive effect on soil matrix infiltration, but thinning measures after 11 years did not enhance soil matrix infiltration further. Philip model was optimal for describing soil matrix infiltration process in this region. In conclusion, soil matrix infiltration capacity of Chinese fir plantations gradually increased from young to middle-aged stands, but matrix infiltration capacity tended to stabilize after 11 years old. Silt content and water stable macroaggregate were the dominant factors influencing matrix infiltration.

Microplastic characteristics and microplastic-heavy metal synergistic contamination in agricultural soil under different cultivation modes in Chengdu, China.

Microplastics have significant implications for global ecosystems. The microplastic distribution, types, sources, and quantified microplastic-heavy metal synergistic pollution in agricultural soil in Chengdu, China were analyzed. The microplastics were detected in all soil samples collected from 103 sites, with concentrations ranging from 1333 to 15067 particle kg-1. The abundance of microplastics in grassland (12,667 ± 3394 particle kg-1) was more than twice higher than that in open field, vegetable field, orchard, and woodland. The main morphological types of microplastics included fibers, films, and granules (all "3-Dimensional" microplastics), with the colors red, blue, and transparent. Granular and fiber microplastics were predominantly in particles < 500 mm, while film microplastics were uniformly distributed at all sizes. The plastic compositions were mainly polypropylene and polyethylene plastics, accounting for 20.73% and 27.90% of the soil microplastic, respectively. Agricultural plastic applications and irrigation water were the sources of soil microplastics. The concentration of Cd, Cr, and Cu in the microplastics was strongly correlated with the corresponding concentration in the soils (p < 0.01), and the microplastic-heavy metal synergistic pollution might deteriorate the soil environment. The results of soil TOC measurements were influenced by microplastics in the soil. The results provide important data for the characteristics of microplastics in the agroecosystem.

Distribution and superposed health risk assessment of fluorine co-effect in phosphorous chemical industrial and agricultural sources.

The industrial and agricultural activities based on phosphorous can increase the F content in the surrounding area, causing a widespread adverse effect on the organisms. However, the current information on the superposed health risk posed by the multi-exposure to the F contamination in an area jointly affected by agricultural and industrial activities (DA) is limited. Herein, the F distribution in multi-environmental media and the exposure risk to humans by ingestion, inhalation, and dermal contact pathways are studied in an DA. The content of soil water-soluble fluorine (WF) was higher in the DA than in the area individually affected by agricultural activities (SA). This indicated a superposed contribution of the industrial and agricultural activities to increase the F toxicity in the soil. The correlation of the soil pH and the organic matter content with the soil WF concentration in DA suggested an inter-relationship between the soil physicochemical properties and the toxicity of F in the soil by industrial and agricultural activities. Irrigation water was not a major anthropogenic source of the cropland soil F. The large variation in F concentration in the crops (101.8-195.6%) might have originated from the discrepancies in the soil F content and air F concentration. The air F pollution (0.6-1.6 µg dm-2 d-1) in the area particularly influenced by intensive industrial activities should be important. The exposure of residents to F was mainly from the ingestion of F-enriched crops. The higher exposure of adults to F than that of children could be attributed to more industrial and agricultural outdoor activities, larger exposure area of the skin, and more daily ingestion of F-enriched food by adults. Overall, present insights into the distribution of and the multi-exposure to F may be beneficial for decreasing the adverse F effects on the residents in DAs worldwide.

Microplastic serves as a potential vector for Cr in an in-vitro human digestive model.

Microplastics (MPs), polymer particles capable of adsorbing heavy metals from ambient environment, have been found in diverse human food resources. Through the consumption of MPs, heavy metals adsorbed on MPs might be transported into human body. This study aims to explore the behavior of heavy metal-contaminated MPs in human digestive system which is not previously researched. Firstly, a chromium (Cr) adsorption/desorption study was conducted with four commonly used nondegradable MPs [polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC) and polystyrene (PS)] as well as one degradable MP (polylactic, PLA). Then, the whole digestive system in-vitro method (WDSM), a systematic model including mouth, gastric, small intestine, and large intestine digestive phases, was conducted on the Cr-loaded MPs. Additionally, the bioaccessibilities and hazard quotients (HQs) of Cr(VI) and Cr(III) were evaluated. Among five MPs, although PLA showed the weakest adsorption capacity for Cr, the Cr(VI) bioaccessibilities for PLA reached the highest values of 19.9%, 15.6% and 3.9% in gastric, small intestinal and large intestinal phases, respectively. The bioaccessibilities of Cr(VI) in gastric phase were significantly higher than those in other phases, while no Cr release from MPs was detected in the mouth phase. In gastric phase, the bioaccessibilities of Cr(VI) were significantly higher than those of Cr(III) in the gastric phase, and both of them approached to a similar level in intestinal phases. In the WDSM, the HQs of Cr(VI) and Cr(III) on MPs were lower than the critical level for both adults and children. Based on the measured bioaccessibilities, the maximum daily total Cr intake for different human groups (female children, male children, female adults and male adults) through MP consumption was estimated from 0.50 to 1.18 µg/day. In general, the five tested MPs were potential to serve as Cr vectors in the WDSM.

Distribution, health risk assessment, and anthropogenic sources of fluoride in farmland soils in phosphate industrial area, southwest China.

The high concentration of fluoride (F) in soils has become a rising concern for its toxicity to microbes, plants, animals and human health. In the present study, the spatial and vertical distribution, health risk assessment and anthropogenic sources of F in farmland soils in an industrial area dominated by phosphate chemical plants were studied. Concentrations of total fluoride (TF) and water soluble fluoride (WSF) in the surface soils decreased with distance within the range of 2500 m at the prevailing downwind of the industrial area. The soil TF and WSF concentrations in 0-40 cm profiles were higher than those in 40-100 cm layers in the industrial area. At the prevailing downwind of the industrial area within 700 m, the hazard quotient values of human exposure to surface soils were higher than 1, indicating that a potential risk may exist for human health in this area. The main exposure pathway for children and adults was oral ingestion and particulate inhalation, respectively. The source apportionment model of soil F was modified based on years' historical data and experimental data. The results showed that the proportion of anthropogenic sources of soil F was dustfalls (69%) > irrigation water (23%) > air (5%) > chemical fertilizers (3%) in the industrial area. The high F concentration of dustfalls was mainly due to the phosphate rock, phosphogypsum, and surface soils with high F contents from the factories. In order to safeguard human health and alleviate hazards of F to surroundings, the control of pollutants emission from factories was a basic and vital step to reduce F in the soils in industrial areas.

[Rectal toxicity prediction based on accurate rectal surface dose summation for cervical cancer radiotherapy].

OBJECTIVE: To propose arectal toxicity prediction method based on deformable surface dose accumulation. METHODS: The clinical data were collected retrospectively from 42patients receiving radiotherapy for cervical cancer. With the first fraction as the reference, the other fractions of rectum surface were registered to the reference fraction to obtain the deformation vector fields (DVFs), which were used to deform and sum the fractional rectal doses to yield the cumulative rectal dose. The cumulative rectal dose was flattened via 3D-2D mapping to generate a 2D rectum surface dose map. Two dosimetric features, namely DVPs and DGPs were extracted. Logistic regression embedded with sequential forward feature selection was used as the prediction model. The predictive performance was evaluated in terms of the accuracy, sensitivity, specificity, and the area under the receiver operating characteristic (ROC) curve (AUC). RESULTS: Significant improvements for rectum surface DIR were achieved. The best predictive results were achieved by using both DVPs and DGPs as the features with a sensitivity of 79.5%, a specificity of 81.3% and an AUC of 0.88. CONCLUSION: The proposed method is feasible for predicting clinical rectal toxicity in patients undergoing radiotherapy for cervical cancer.