In heavy metal-contaminated areas, the simultaneous occurrence of increasing microplastic pollution and persistent acid rain poses a serious threat to food security. However, the mechanisms of combined exposure to microplastics (MP) and acid rain (AR) on the toxicity of cadmium (Cd) in rice seedlings remain unclear. Our study investigated the combined effects of exposure to polyvinyl chloride microplastics and AR (pH 4.0) on the toxicity of Cd (0.3, 3, and 10 mg/L) in rice seedlings. The results showed that at low Cd concentrations, the combined exposure had no significant effect, but at high Cd concentrations, it alleviated the effects of Cd stress. The combined application of MP and AR alleviated the inhibitory effects of Cd on seedling growth and chlorophyll content. Under high Cd concentrations (10 mg/L), the simultaneous addition of MP and AR significantly reduced the production of reactive oxygen species (ROS), the content of malondialdehyde (MDA), and the activity of the superoxide dismutase (SOD). Compared with AR or MP alone, the combination of MP and AR reduced root cell damage and Cd accumulation in rice seedlings. Transcriptomic analysis confirmed that under high Cd concentrations, the combination of MP and AR altered the expression levels of genes related to Cd transport, uptake, MAPK kinase, GSTs, MTs, and transcription factors, producing a synergistic effect on oxidative stress and glutathione metabolism. These results indicate that co-exposure to MP and AR affected the toxicity of Cd in rice seedlings and alleviated Cd toxicity under high Cd concentrations to some extent. These findings provide a theoretical basis for evaluating the toxicological effects of microplastic and acid rain pollution on crop growth in areas contaminated with heavy metals, and are important for safe agricultural production and ecological security.

This study examines how acid rain affects the microstructure and mechanical properties of cement-amended loess, crucial for ensuring the safety of engineering projects. We aimed to investigate how acid rain influences the micro-mechanical behavior of cement-amended loess and its damage characteristics under combined acid rain and loading conditions. Cement-amended loess samples were exposed to artificial acid rain with varying pH levels, and changes in their strength and microstructure were analyzed using unconfined compression tests, SEM, NMR, and XRD techniques. Our findings reveal that acid rain erosion of cement-amended loess triggers hydration and erosion reactions. As acid rain concentration increases, the unconfined compressive strength of the amended soil gradually decreases, accompanied by an expansion of pore spaces from small to large-medium pores. Additionally, particle contacts shift from face-to-face and side-to-side to point-to-point and side-to-side configurations. Furthermore, prolonged erosion time exacerbates pore space expansion, indicating a time-dependent effect on soil integrity. To characterize these effects, we developed a constitutive equation within the framework of damage mechanics that incorporates both erosion and loading. This equation successfully aligns with experimental data, providing a comprehensive understanding of the coupled effects of acid rain erosion and mechanical loading on cement-amended loess. These insights are pivotal for designing resilient engineering solutions in environments prone to acid rain erosion.

Acid rain and nitrogen deposition resulting from fossil fuel combustion and atmospheric NH3 enrichment have inflicted significant damage to ecosystems on a global scale. However, their specific impacts on forest soil ecosystems, particularly in soil carbon (C), nitrogen (N), and phosphorus (P) cycling, remain unclear. For this study metagenomic sequencing was employed to study the effects of simulated acid rain and nitrogen deposition on microbial functional genes in a subtropical plantation in the Yangtze River Delta region. Our findings indicated that acid rain and nitrogen deposition did not have significant impacts on overall functional Shannon diversity. However, acid rain treatments did alter microbial functional structures, particularly as relates to C, N, and P cycling. Notably, the soil pH had a significant correlation with microbial functional profiles. In the absence of nitrogen deposition, acid rain led to an increase in the relative abundance of starch and carbon monoxide (CO) oxidation processes, while reducing the relative abundance of multiple systems and reductive tricarboxylic acid (rTCA) pathway processes. Further, acid rain decreased the relative abundance of nitrogen fixation and nitrification processes, as exemplified by hao, nirK, and norZ genes, while increasing the relative abundance of norC and narI genes. Additionally, acid rain was associated with a decrease in the relative abundance of P starvation regulation and inorganic P solubilization processes. However, N deposition did not have a significant effect on microbial functional processes related to C, N, and P cycling. Our study emphasized the negative impacts of short-term acid rain on soil N and P cycling in a subtropical plantation, which surpassed that of short-term N deposition.

Sunflower is an ideal crop for phytoremediation of cadmium-contaminated farmland, as it brings economic benefits while conducting soil remediation. Due to industrial emissions and car exhaust, Cd contaminated areas are often accompanied by acid rain. However, the impact of acid rain on the Cd remediation capacity of sun-flowers and its potential influencing factors are unclear. An experiment was manipulated to elucidate the effects of Cd concentration (0,10,50,100 mu mol/L) and acid rain (pH 4.0) on the phytoremediation ability of sunflowers, in which the properties of them were explored. The results indicated that Cd stress is the main factor affecting the growth of sunflowers. Without AR, Cd treatment decreased sunflower biomass by 67.5-85.6%. Under AR, Cd treatment decreased sunflower biomass 53.9-86.4%. Compared without AR, the relative chlorophyll content with AR increased by 22.3-23.1%, while the YII with AR decreased by 6.5-20.0%. There was an interaction between acid rain and Cd stress on antioxidant enzyme activity. With AR, CAT activity at 0 mu mol/L Cd treatment increased by 25.6%, compared without AR. Whether there is acid rain or not, the POD and SOD activities were increased at 10, 50 mu mol/L Cd treatment, but they were decreased at 100 mu mol/L Cd treatment. Among them, acid rain exacerbated the impact of POD activity (decreased by 31.4%) at 100 mu mol/L Cd treatment and SOD activity (decreased by 15.1%) at 50 mu mol/L Cd treatment, compared without AR. In this experiment, the phytoremediation capacity of sunflowers mainly depended on the concentration of Ca in the leaves and their antioxidant capacity. Acid rain enhanced 77.5% the total Cd accumulation at 10 mu mol/L Cd treatment, compared without AR. Acid rain exacerbated the damage of Cd to the chloroplast structure of sunflowers, and reduced the accumulation of starch particles. The study findings may be useful for improving the phytoremediation of Cd-contaminated soil.