Investigation of arsenic contamination in soil and plants along the river of Xinzhou abandoned gold mine in Qingyuan, China.

The exploitation of mineral resources is very important for economic development, but disorderly exploitation poses a serious threat to the ecological environment. However, investigations on the advantages of plant species and environmental pollution in polluted mining areas are limited. Thus, a survey was conducted to evaluate the impacts of abandoned mines on the surrounding ecological environment along rivers in polluted areas and to determine the Arsenic (As) pollution status in soil and plants. The results showed that the soil and vegetation along the river in the survey area were seriously polluted by As. The total As content of the 15 samples was significantly greater than the national soil background value (GB 15618-2018), and degree of pollution was nonlinearly related to the distance from the mine source, R2 = 0.9844. B. bipinnata, P. vittata and B. nivea were predominant with degrees of dominance of 0.01-0.33, 0.05-0.11, and 0.06-0.14 respectively. The As enrichment capacities of Juncus and P. vittata were significantly greater than those of the other plants, while the bioaccumulation factors (BCFs) were 21.81 and 7.04, respectively.

Nitrogen addition accelerates litter decomposition and arsenic release of Pteris vittata in arsenic-contaminated soil from mine.

The arsenic (As) release from litter decomposition of As-hyperaccumulator (Pteris vittata L.) in mine areas poses an ecological risk for metal dispersion into the soil. However, the effect of atmospheric nitrogen (N) deposition on the litter decomposition of As-hyperaccumulator in the tailing mine area remains poorly understood. In this study, we conducted a microcosm experiment to investigate the As release during the decomposition of P. vittata litter under four gradients of N addition (0, 5, 10, and 20 mg N g-1). The N10 treatment (10 mg N g-1) enhanced As release from P. vittata litter by 1.2-2.6 folds compared to control. Furthermore, Streptomyces, Pantoea, and Curtobacterium were found to primarily affect the As release during the litter decomposition process. Additionally, N addition decreased the soil pH, subsequently increased the microbial biomass, as well as hydrolase activities (NAG) which regulated N release. Thereby, N addition increased the As release from P. vittata litter and then transferred to the soil. Moreover, this process caused a transformation of non-labile As fractions into labile forms, resulting in an increase of available As concentration by 13.02-20.16% within the soil after a 90-day incubation period. Our findings provide valuable insights into assessing the ecological risk associated with As release from the decomposition of P. vittata litter towards the soil, particularly under elevated atmospheric N deposition.

The application of mixed stabilizing materials promotes the feasibility of the intercropping system of Gynostemma pentaphyllum/Helianthus annuus L. on arsenic contaminated soil.

Intercropping technology and stabilizing materials are common remediation techniques for soils contaminated with heavy metals. This study investigated the feasibility of the Gynostemma pentaphyllum (G. pentaphyllum)/Helianthus annuus L. (H. annuus) intercropping system on arsenic (As) contaminated farmland through field and pot experiments and the regulation of plant As absorption by the application of mixed stabilizing materials in this intercropping system. Field experiments demonstrated that intercropping with H. annuus increased the As concentration in G. pentaphyllum leaves to 1.79 mg kg-1 but still met the requirements of the national food standard of China (2 mg kg-1) (GB2762-2017). Meanwhile, G. pentaphyllum yield in the intercropping system decreased by 15.09%, but the difference was insignificant (P > 0.05). Additionally, the As bioconcentration (BCA) per H. annuus plant in the intercropping system was significantly higher than that in the monoculture system, increasing by 76.37% (P < 0.05). The pot experiment demonstrated that when granite powder, iron sulfate mineral, and "Weidikang" soil conditioner were applied to the soil collectively, G. pentaphyllum leaf As concentration in the intercropping system could be significantly reduced by 42.17%. Rhizosphere pH is the most crucial factor affecting As absorption by G. pentaphyllum in intercropping systems. When these three stabilizing materials were applied simultaneously, the As bioaccumulation (BCA) per H. annuus plant was significantly higher than that of normal intercropping treatment, which increased by 71.12% (P < 0.05), indicating that the application of these stabilizing materials significantly improved the As removal efficiency of the intercropping system. Dissolved organic carbon (DOC) concentration in the rhizosphere soil is the most pivotal factor affecting As absorption by H. annuus. In summary, the G. pentaphyllum-H. annuus intercropping model is worthy of being promoted in moderately As polluted farmland. The application of granite powder, iron sulfate mineral, and "Weidikang" soil conditioner collectively to the soil can effectively enhance the potential of this intercropping model to achieve "production while repairing" in the As polluted farmland.

Intercropping efficiency of Pteris vittata with two legume plants: Impacts of soil arsenic concentrations.

Intercropping of hyperaccumulators with crops has emerged as a promising method for remediating arsenic (As)-contaminated soil in agroecosystems. However, the response of intercropping hyperaccumulators with different types of legume plants to diverse gradients of As-contaminated soil remains poorly understood. In this study, we assessed the response of plant growth and accumulation of an As hyperaccumulator (Pteris vittata L.) intercropped with two legume plants to three gradients of As-contaminated soil. Results indicated that soil As concentration had a substantial effect on the As uptake by plants. P. vittata growing in slightly As-contaminated soil (80 mg kg-1) exhibited higher As accumulation (1.52-5.49 folds) than those in higher As-contaminated soil (117 and 148 mg kg-1), owing to the lower soil pH in high As-contaminated soil. Intercropping with Sesbania cannabina L. increased As accumulation in P. vittata by 19.3%- 53.9% but decreased in intercropping with Cassia tora L. This finding was attributed to S. cannabina providing more NO3--N to P. vittata to support its growth, and higher resistance to As. The decreased rhizosphere pH in the intercropping treatment also resulted in the increased As accumulation in P. vittata. Meanwhile, the As concentrations in the seeds of the two legume plants met the national food standards(<0.5 mg kg-1). Therefore, the intercropping P. vittata with S. cannabina is a highly effective intercropping system in slightly As-contaminated soil and provides a potent method for As phytoremediation.

Effects of different planting distances and fertilizer use on the remediation of farmland contaminated with Cd by intercropping Cucurbita moschata and Amaranthus hypochondriacus L.

Selecting suitable agronomic measures can strengthen the application of intercropping in the remediation of cadmium (Cd)-contaminated soil. In this study, the effects of different planting densities and fertilizer applications on the crop growth and Cd absorption of a pumpkin (Cucurbita moschata)-Amaranthus hypochondriacus L. intercropping system was determined. The goal was to provide enhanced means and a scientific basis for the promotion and application of this intercropping system. The Cd content of pumpkin in different planting systems was lower than the national food safety standard (0.05 mg kg-1). In the IN-1 (4 pumpkin plants intercropped with 200 A. hypochondriacus plants) and IN-2 (4 pumpkin plants intercropped with 400 A. hypochondriacus plants) intercropping systems, the bioconcentration amount (BCA) per plant of Cd in A. hypochondriacus increased by 32.43% and 25.25%, respectively, compared with that of the monocropping system (P < 0.05). The IN-2 system had the highest equivalent ratio of heavy metal removal (3.08), indicating that this model had a substantial advantage for removing Cd. The land equivalent ratio of IN-1 (2.89) and IN-2 (2.60) was significantly higher than that of other intercropping systems, indicating that these two models had obvious yield advantages. In our study, chicken manure was the best at promoting the growth and yield of the two plants and sludge treatment significantly enhance Cd absorption of A. hypochondriacus. In general, intercropping four pumpkin plants with 400 A. hypochondriacus plants and applying chicken manure fertilizer can strengthen the application of this intercropping system in Cd-contaminated soil.

Dose-dependent inhibitory effects of glyphosate on invasive Pomacea canaliculata reproductive and developmental growth under oxidative deposition.

Glyphosate (GLY) is the most widely used herbicide worldwide, and its effects on animals and plants have attracted increasing attention. In this study, we explored the following: (1) the effects of multigenerational chronic exposure to GLY and H2O2, alone or in combination, on the egg hatching rate and individual morphology of Pomacea canaliculata; and (2) the effects of short-term chronic exposure to GLY and H2O2, alone or in combination, on the reproductive system of P. canaliculata. The results showed that H2O2 and GLY exposure had distinct inhibitory effects on the hatching rate and individual growth indices with a substantial dose effect, and the F1 generation had the lowest resistance. In addition, with the prolongation of exposure time, the ovarian tissue was damaged, and the fecundity decreased; however, the snails could still lay eggs. In conclusion, these results suggest that P. canaliculata can tolerate low concentrations of pollution and in addition to drug dosage, the control should focus on two time points, the juvenile and early stage of spawning.

Luffa cylindrica Intercropping with Semen cassiae-A Production Practice of Improving Land Use in Soil Contaminated with Arsenic.

In recent years, research on the safe utilization and green remediation of contaminated soil by intercropping has become common. In this study, the growth of an intercropping system of Luffa cylindrica-Semen cassiae in soil contaminated with medium amounts of arsenic (As) was studied using field (91.60 mg kg-1) and pot (83.34 mg kg-1) experiments. The field experiments showed that intercropping significantly increased the yield per plant of L. cylindrica by 27.36%, while the yield per plant of S. cassiae decreased by 21.66%; however, this difference was not significant. Intercropping reduced the concentration of As in all organs of L. cylindrica but increased the concentration of As in all parts of S. cassiae. The accumulation of As per plant of L. cylindrica was reduced by 20.72%, while that in a single plant of S. cassiae was increased by 201.93%. In addition, the concentration of As in the fruit of these two crops in these two planting modes was low enough to meet the National Food Safety Standard of China (GB2762-2017). In addition, the land equivalent ratio and As metal removal equivalent ratio of the intercropping mode was 1.03 and 2.34, indicating that the intercropping mode had advantages in land use and As removal. In the pot experiment, the biomass and As concentration of L. cylindrica and S. cassiae were roughly consistent with those in the field experiment. During the sampling period, intercropping reduced the concentration of As in the rhizosphere soil solution of L. cylindrica by 3.1-23.77%, while it increased the concentration of As in the rhizosphere soil solution of S. cassiae by 13.30-59.40%. The changes in pH and redox potential were also closely related to the content of water-soluble As in the rhizosphere environment, which affects the absorption of As by plants. In general, the L. cylindrica-S. cassiae intercropping system is a planting mode that can effectively treat soil that is moderately contaminated with As and remove it from the soil to an extent.