Manningwest1963

Wetting-drying alternation irrigation (WDI) can harvest high grain yield under effective irrigation water saving conditions. However, the kernel cadmium (Cd) content usually exceeds the national standard of 0.20 mg Cd per kg kernel in WDI. Applying a passivating agent with high-efficient repairing capabilities could be a feasible approach to reduce Cd content lower than 0.20 mg·kg-1 in WDI. Therefore, a field experiment was conducted with different irrigation regimes and passivating agents in a mildly Cd-polluted paddy field, of which the irrigation regimes were WDI and traditional flooded irrigation (FI) and the six passivating agents treatments were CK (no passivating agent; T1), slaked lime with 1125 kg·hm-2(T2), 1125 kg slaked lime and 3000 kg biochar per hectare (T3), 1125 kg slaked lime and 3000 kg organic fertilizer per hectare (T4), 1500 kg porous Nano stupalith per hectare (T5), and 1125 kg slaked lime combined with 1500 kg porous Nano stupalith per hectare (T6). Two typical Indica hybrid rice varietulated capacity is used. Thus, the combined mode of the WDI+T6+cultivar with accumulated low Cd content could be considered an optimized cultivation scheme to obtain no Cd contaminated kernels with high grain yield and water-use efficiency in mildly polluted paddy fields.The bioaccessibility and health risks of heavy metals in soil-rice system of southwestern Fujian province were studied by combining a simple bioavailability extraction method (SBET) with a health risk assessment model. The results showed that some heavy metals in the agricultural soils and rice of southwestern Fujian province were enriched. The contents of Cd, Zn, Pb, and Cu were greater than the screening value of soil pollution risk for agricultural land (GB 15618-2018) by 32.4%, 15.5%, 14.1%, and 12.7% in the study areas, respectively. The accumulation ability of heavy metals was different and followed the approximately decreasing order of Cd > Zn > Cu > Ni > Hg > As > Cr > Pb. The bioaccessibility of heavy metals in soils and rice were quite different. The bioaccessibility of each heavy metal in rice was greater than the bioaccessibility of the heavy metals in soil, which indicated that the heavy metals in rice were more easily absorbed by the human body. The comprehensive non-carcinogenic risk index (HI) of heavy metals to adults and children was 2.71 and 4.06, respectively, indicating that there were non-carcinogenic risks. The comprehensive carcinogenic risk index (TCR) of heavy metals to adults and children was 1.42×10-3 and 5.28×10-4, respectively, indicating that there was a carcinogenic risk present. The non-carcinogenic risks were mainly due to As, while the carcinogenic risks were mainly contributed by Cd. The non-carcinogenic risk of children was higher than that of adults, while the carcinogenic risk of children was lower than that of adults. find more This result may be related to physiological characteristics, exposure period, and dietary intake. The dietary intake route may be the main pathway for heavy metals in the soil-rice system of southwest Fujian province to cause health risks. Therefore, more attention should be paid to the risks of dietary exposure in the risk management of heavy metals.The simulation analysis of the migration path and soil accumulation trend of Cd in paddy soil systems could contribute to improved scientific and reasonable risk decision-making. In this study, based on a regional survey of environmental media in Youxian County, Hunan Province, a pollutant accumulation model (PAM) was built to predict the cumulative trend of Cd in paddy soils. Combined with Monte Carlo simulation, the PAM model was used to evaluate the effectiveness and sustainability of various remediation measures. Results showed that the probability of Cd accumulation in paddy soils in Youxian County exceeded that of the national soil environmental quality standard by 2-fold and was up to 82.1%, and the average accumulation rate reached 4.28 μg·(kg·a)-1 after 50 years of cultivation under current input pattern. Sensitivity analysis results showed that atmospheric deposition and rice uptake were the key processes affecting Cd accumulation in paddy soils. Results of a multi-scenario simulation showed that the comprehensive measures, such as reducing the straw returning, optimizing the layout of industrial and mining enterprises that reduce the atmospheric deposition of Cd, and cleaning irrigation water, could reduce the Cd accumulation in paddy soils by 43.7% and reduce the probability of light Cd pollution by 80.6% after 50 years, which would be an effective long-term measure to prevent and control Cd pollution risk in paddy soils.Mastering the spatial distribution of heavy metals in the soil plays an important supporting role in the scientific formulation of soil pollution risk management and control strategies. Few factors were considered and multiple collinearity between parallel variables existed,resulting in low prediction accuracy. OK (common Kriging method), NRK (regressive Kriging method based on natural factors only), and NARK (regressive Kriging based on natural-human factors)were used to simulate the spatial distribution of soil Cd by selecting 23 natural-artificial influencing factors. The prediction accuracy was evaluated based on an empirical study of the area around Shaoguan Qujiang smelter. The results showed that the above-standard rate of soil cadmium in this area reached 85.93%, and the effect on the spatial heterogeneity of soil cadmium was shown as air emissions from smelters > air emissions from steel plants > pH > organic matter > Euclidean distance to road > Euclidean distance to river. The root-mean-square error and average absolute error of NARK's prediction results for soil cadmium were 26.86% and 30.56% lower than that of the OK method, respectively. The model determination coefficient R2 increased from 0.78 to 0.88. Compared with that of NRK, it was reduced by 24.15% and 24.23% and R2 increased from 0.81 to 0.88. The NRK combining natural and human factors significantly improved the simulation accuracy of the spatial distribution of soil cadmium, and the addition of human factors as auxiliary variables, especially atmospheric point source pollution emissions, greatly contributed to the improvement of the model accuracy.