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The characteristics of dissolved organic carbon loss with different fertilization treatments were examined to derive the best nutrient management method for sloping farmland in the Three Gorges Reservoir area where maintaining the soil carbon balance and reducing environmental pollution caused by carbon loss is crucial. Experimental runoff plots were set up at the Experimental Station for Soil and Water Conservation and Environmental Research in the Three Gorges Reservoir Region, Chinese Academy of Sciences, involving the following five treatmentsNo fertilization (CK), conventional fertilization (conventional), optimum fertilization (optimum), biochar combined with 85% optimum fertilizer (biochar), and straw combined with 85% optimum fertilizer (straw). The effects of the five treatments on runoff flux, sediment yield, and soil organic carbon flux were monitored and evaluated. Results show that①Subsurface flow accounted for 52.84%-92.23% of the runoff (both surface and subsurface flow) and the loss flux of dits was ranked biochar > optimum > straw > conventional > CK. ④Compared to the optimum treatment, the straw treatment and biochar treatment increased the soil organic carbon (SOC) content by 95.79% and 32.16%, respectively. Based on these results, straw combined with 85% of optimum fertilizer is the best nutrient management method for this sloping farmland as it can reduce surface runoff flux, sediment yield, and the loss flux of soil organic carbon while increasing the soil organic carbon content.A pot-based experiment was conducted to study the Cd tolerance and accumulation characteristics of four invasive herbs (Galinsoga quadriradiata, Panicum dichotomiflorum, Setaria geniculata, and Lolium persicum) under exposures of 0 (T0), 5 (T5), 25 (T25), and 50 mg·kg-1 (T50) soil Cd concentrations to screen for potential Cd accumulators for phytoremediation. The results showed that the biomasses of both shoots and roots of G. quadriradiata had no significant changes compared to the control (T0) samples under all Cd treatments, whereas the biomass of the other three Poaceae species significantly decreased under the T25 or T50 treatment. The results indicate that G. quadriradiata had stronger Cd tolerance than the other three species. The Cd concentrations in the shoots and roots of the four herbs significantly increased with an increase in soil Cd concentrations, but the shoot bioconcentration factors (SBCF) of the four plant species significantly decreased under T5, T25, and T50 treatment. The SBCF of G. quadriradiata and P. dichotomiflorum were greater than 1 whereas those of S. geniculata and L. persicum were lower than 1. see more The translocation factors (TF) of G. quadriradiata were 0.93, 0.73, and 1.04 under T5, T25, and T50 treatment, respectively, which were significantly higher than those of the other three plants under the same soil Cd concentration. In addition, both the total Cd and shoot Cd contents of G. quadriradiata were notably higher than in the other three species under the same Cd treatment. Moreover, 90% of the Cd in G. quadriradiata could be transferred aboveground, which was significantly higher than for the other three plants. Based on our comprehensive comparison of Cd tolerance and accumulation capacity, we suggest that G. quadriradiata is a high-Cd accumulator with considerable phytoremediation potential.Peppers are a high Cd-enriched vegetable. On the basis of a preliminary screening experiment of 91 pepper varieties and soil culture experiments during the entire growth period of 26 varieties, a high Cd variety (X15), medium Cd variety (X39), and two low varieties (X45 and X55) were selected to study the effect of different cadmium levels (0, 5, and 10 mg·kg-1 Cd) on enrichment, transport, and accumulation as well as its subcellular distribution and chemical form. Based on the results, 5 mg·kg-1 and 10 mg·kg-1 of Cd inhibited shoot dry weights of four pepper varieties but increased the root dry weights of X15, X45, and X55 varieties. Sodium chloride-bound cadmium and acetate-bound cadmium are the main forms of cadmium in the pepper fruits. Subcellular cadmium concentrations in the roots, leaves, and fruits of pepper plants were ranked in order cytoplasm > cell wall > organelle, and in the stems the order was cell wall > cytoplasm > organelle. Cd compartmentalization plays an important role in pepper resistance to cadmium stress. Under dosages of 5 mg·kg-1 Cd and 10 mg·kg-1 Cd, Cd concentrations in stems and leaves were ranked in order X39 > X15 > X55 > X45, with fruit Cd concentrations ranked in order X15 > X39 > X55 > X45. The Cd concentration was lowest in the roots of X15 whereas this variety has the highest concentrations in its fruit. The Cd concentrations in the roots, stems, and leaves of X39 were the highest among the four varieties whereas the concentration in the fruit was lower than in the X15 variety. The concentration of Cd in pepper fruits depends on the Cd transport capacity redistribution ability to the shoots.In order to study the characteristics and factors influencing Cd accumulation in surface soils and crops in karst areas, and to provide a theoretical basis for safe land use, 360 surface soil samples, 7 deep soil samples, and 85 rice samples were collected from central Qianjiang District, Chongqing. The samples and 73 corn samples (corresponding to root-zone soil samples), were analysed to determine the content of Cd, TFe2 O3, Mn, organic matter (Corg), Se, and pH. Based on geostatistical analyses, the spatial distribution and Cd enrichment of the surface soils were determined and a safety evaluation for the soil and crops was carried out. The results showed that the spatial distribution of Cd in the surface soil was uneven, with the surface layer showing significant enrichment. This pattern was controlled by the soil parent material and human activities. The enrichment of surface layer was mainly affected by iron manganese oxides and organic matter (Corg). Soil Cd was mainly found at ‘non-polluted’ and ‘lightly polluted’ levels, although some areas present strong ecological risks. The main contaminated area occurs in association with Permian strata, demonstrating a geological control on soil Cd pollution. Slight-to-severe Cd pollution was identified in bulk crops; the recommended daily consumption limit for rice is 0.87 kg·d-1 and corn is 1.53 kg·d-1. The bioavailability of Cd is affected by soil pH and Se content. Under acidic conditions, Cd bioavailability is high, and crops in areas with high soil Se are safer. It is recommended that crops with low Cd accumulation are planted in the Permian outcrop area of Shuitian Township, or alternatively, soil pH should be adjusted to control the risk of Cd pollution and ensure safe land use. In addition, planting crops in areas with high soil Se content is preferable.Cadmium (Cd) is easily enriched in rice, resulting in an excessive Cd content in the grain, which seriously threatens human health. Manganese (Mn) is an essential element of plants. In a field experiment on Cd-contaminated acid soils, we investigated the effectiveness and mechanism of Mn in minimizing Cd accumulation in rice via foliar spraying using 0.1%, 0.3%, and 0.5% nano-MnO2 solutions at an early stage of heading. Compared with a control treatment, foliar spraying effectively reduced the Cd content of rice leaves, husks, and brown rice; increased the Mn content of all rice organs; but had no effect on rice yield. Foliar application of nano-MnO2 alleviated the plant stress induced by Cd by improving leaf photosynthesis, inhibiting lipid peroxidation, and increasing the content of the oxidative stress protein kinase. In addition, foliar application of nano-MnO2 limited the absorption of Cd by roots by increasing the content of iron-manganese plaque on the surfaces of rice roots and strengthening its adsorption/co-precipitation of Cd. Therefore, foliar application of nano-MnO2 during the early stages of rice heading is an effective measure to increase the Mn content and reduce the Cd content of brown rice.Using an in-situ experiment in Cd contaminated paddy fields in Chongqing, the absorption and distribution of Cd in rice plants was examined following the combined application of lime and organic matter, and the mechanisms driving changes in Cd fractions in soil were also studied. The results showed that pH, OM content, and CEC in the soil were significantly enhanced, and OM and CEC were significantly positively correlated, as pH showed a significant positive correlation; pH and CEC was mainly associated with a change in Cd from the acidic extractable fraction to the reducible, oxidable, and residual fractions. The percentage of acidic extractable Cd dropped by 22.92%-31.25% with the application of the amendments, thus reducing the accumulation of Cd in rice plants in the followed orderCK (control group)≫B6 (lime and maize straw)≈B4 (lime and biochar)≈B3 (lime and activated humic acidic fertilizer) > B2 (lime and humic acidic fertilizer)≈B1 (lime) > B5 (lime and oil cake). On the other hand, for both the treatments and control conditions (CK), the Cd content of brown rice was higher than Chinese standard (GB 2762-2017), while that of polished (white) rice was lower than the Chinese standard after treatment. Overall, treatment using all of the remediation agents offers some benefit for the safe utilization of agricultural contaminated soil and safe food production. The combined application of lime and oil cake proved the best measure for treating Cd contaminated acidic rice fields, yielding a reduction in acidic extractable Cd (31.25%), a reduction in the Cd content of rice plants (33.32%), and the lowest Cd content (0.13 mg·kg-1) in polished rice (a 42.17% compared to the control).A pot-based planting experiment of Chinese brassica was carried out to study the influence of the compound modifier FZB (iron sulfate+zeolite+modified biochar) on the physical and chemical properties of soil, As and Cd bioavailability and morphology, and the ability of Chinese brassica to accumulate As and Cd at different dosages. The results showed that, after application of FZB, the pH, OM, and CEC contents of the rhizosphere soil tended to increase in As and Cd compound contaminated farmland soils. The concentrations of available As and available Cd in the soil gradually reduced with an increase in FZB application, with maximum reductions of 65.99% and 30.68%, respectively. The application of FZB significantly changed the morphology of heavy metals in the soil, which consequently decreased the exchangeable concentrations of As and Cd, while the concentrations of aluminum-bound As, iron-bound As, organic bound Cd, and residual Cd increased. At the same time, the application of FZB effectively reduced the concentrations of As and Cd in the roots and aerial parts of Chinese brassica. When 8 g·kg-1 of FZB was applied, compared with the control group, the concentrations of As and Cd in the aerial parts of Chinese brassica were reduced by 42.09% and 31.34%, respectively. FZB application decreased the As and Cd bioaccumulation capacity of the roots and aerial parts, and decreased the capacity of the plant to translocate As from the roots to the aerial parts. The study shows that the composite modifier FZB has good application prospects for reducing the bioavailability of As and Cd in farmland soils.