Graphene oxide (GO), as a novel carbon-based nanomaterial (CBN), has been widely applied to every respect of social life due to its unique composite properties. The widespread use of GO inevitably promotes its interaction with heavy metal cadmium (Cd), and influences its functional behavior. However, little information is available on the effects of GO on greening hyperaccumulators under co-occurring Cd. In this study, we chose a typical greening hyperaccumulator (Lonicera japonica Thunb.) to show the effect of GO on Cd accumulation, growth, net photosynthesis rate (P_n), carbon sequestration and oxygen release functions of the plant under Cd stress. The different GO-Cd treatments were set up by (0, 10, 50 and 100 mg L⁻¹) GO and (0, 5 and 25 mg L⁻¹) Cd in solution culture. The maximum rate of Cd accumulation in the roots and shoots of the plant were increased by 10 mg L⁻¹ GO (exposed to 5 mg L⁻¹ Cd), indicating that low-concentration GO (10 mg L⁻¹) combined with low-concentration Cd (5 mg L⁻¹) might stimulate the absorption of Cd by L. japonica. Under GO treatments without Cd, the dry weight of root and shoot biomass, P_n value, carbon sequestration per unit leaf area and oxygen release per unit leaf area all increased in various degrees, especially under 10 mg L⁻¹ GO, were 20.67%, 12.04%, 35% and 28.73% higher than the control. Under GO-Cd treatments, it is observed that the cooperation of low-concentration GO (10 mg L⁻¹) and low-concentration Cd (5 mg L⁻¹) could significantly stimulate Cd accumulation, growth, photosynthesis, carbon sequestration and oxygen release functions of the plant. These results indicated that suitable concentrations of GO could significantly alleviate the effects of Cd on L. japonica, which is helpful for expanding the phytoremediation application of greening hyperaccumulators faced with coexistence with environment of nanomaterials and heavy metals.

“Hormesis” is considered a dose–response phenomenon mainly observed at hyperaccumulator plants under heavy metals stress. In this study, the effects of electric fields on hormesis responses in Lonicera japonica Thunb. under cadmium (Cd) treatments were investigated by assessing the plant growth and photosynthetic characteristics. Under Cd treatments without electric fields, the parameters of plant growth and photosynthetic characteristics increased significantly when exposed to 5 mg L⁻¹ Cd, and decreased slightly when exposed to 25 mg L⁻¹ Cd, showing an inverted U-shaped trend, which confirmed that low concentration Cd has a hormesis effect on L. japonica. Under electric fields, different voltages significantly promoted the inverted U-shaped trend of the hormesis effect on the plant, especially by 2 V cm⁻¹ voltage. Under 2 V cm⁻¹ voltage, the dry weight of the root and leaf biomass exposed to 5 mg L⁻¹ Cd increased significantly by 38.38% and 42.14%, and the photosynthetic pigment contents and photosynthetic parameters were also increased significantly relative to the control, indicating that a suitable electric field provides better improvements for the hormesis responses of the plant under Cd treatments. The synergistic benefits of the 5 mg L⁻¹ Cd and 2 V cm⁻¹ electric field in terms of the enhanced hormesis responses of growth and photosynthetic characteristics could contribute to the promoted application of electro-phytotechnology.

The pollution of heavy metals in agricultural soil poses a dangerous health risk to nearby residents. This study presents a method to assess the health risks of heavy metal pollution using Monte Carlo simulations. Soil samples from an agate dyeing village were collected and their heavy metal contents were analyzed. The results indicate the contamination of heavy metals in the study area soil, the singlefactor index values of Pb, Cu, Cr, and Ni were found to indicate mild pollution, and the Nemerow complex index values of all investigated metals were ranked at level IV, indicating moderate pollution. The health assessment indicates an unacceptable total carcinogenic risk for adults and children and noncarcinogenic hazard quotient for adults. Oral ingestion was found to be the main exposure pathway, and the most sensitive factors were the adherence factor, soil ingestion rate, and body weight.

Context: The Songnen Plain is a crucial grain-producing region in China, and its western area, influenced by natural conditions and long-term human activities, faces severe issues of soil salinisation. In recent years, soil organic carbon (SOC) in saline-alkali soils has gained increasing attention as a material foundation for grain production and an essential carbon sink for mitigating climate change. However, the driving factors behind regional-scale changes in SOC in saline-alkali soils remain unclear. Aims: This research was conducted to assess changes in soil organic carbon stocks and identify main driving factors in saline soils at 40-years scale. Methods: Taking Tongyu County in the western part of the Songnen Plain as a case study, this research explored the spatiotemporal variation of soil organic carbon density (SOCD) and soil organic carbon storage (SOCS) from 1982 to 2022 using GIS. Random forest regression and structural equation modelling were employed to identify environmental factors influencing SOCD distribution in different soil layers. Key results: (1) From 1982 to 2022, the average SOCD in the surface, subsurface, and bottom soil layers decreased by 0.65, 0.34, and 0.46 kg m−2, respectively, resulting in a total carbon storage reduction of 12.93 Tg C. (2) In 1982, the vertical distribution of SOCD was higher at the top and bottom layers and lower in the middle; however, by 2022, it exhibited a gradual decrease layer by layer. (3) Topographic factors only influenced surface SOCD, while the influence of environmental humidity and land use on SOCD decreased with increasing depth. Conclusions: These findings provided valuable scientific insights for implementing regional soil carbon sequestration and soil nutrient conservation measures.

The carbon sequestration and oxygen release of landscape plants are dominant ecological service functions, which can play an important role in reducing greenhouse gases, improving the urban heat island effect and achieving carbon peaking and carbon neutrality. In the present study, we are choosing Lonicera japonica Thunb. as a model plant to show the effects of Cd stress on growth, photosynthesis, carbon sequestration and oxygen release characteristics. Under 5 mg kg⁻¹ of Cd treatment, the dry weight of roots and shoots biomass and the net photosynthetic rate (P_N) in L. japonica had a significant increase, and with the increase in Cd treatment concentration, the dry weight of roots and shoots biomass and P_N in the plant began to decrease. When the Cd treatment concentration was up to 125 mg kg⁻¹, the dry weight of root and shoots biomass and P_N in the plant decreased by 5.29%, 1.94% and 2.06%, and they had no significant decrease compared with the control, indicating that the plant still had a good ability for growth and photoenergy utilization even under high concentrations of Cd stress. The carbon sequestration and oxygen release functions in terms of diurnal assimilation amounts (P), carbon sequestration per unit leaf area (WCO₂), oxygen release per unit leaf area (WO₂), carbon sequestration per unit land area (PCO₂) and oxygen release per unit land area (PO₂) in L. japonica had a similar change trend with the photosynthesis responses under different concentrations of Cd treatments, which indicated that L. japonica as a landscaping Cd-hyperaccumulator, has a good ability for carbon sequestration and oxygen release even under high concentrations of Cd stress. The present study will provide a useful guideline for effectively developing the ecological service functions of landscaping hyperaccumulators under urban Cd-contaminated environment.