The high concentrations of trace elements in the environment, especially the carcinogenic elements Cr, Cd, and As, in populated areas can lead to an increased non-carcinogenic risk and carcinogenic risk in humans via the effective exposure pathways (inhalation and dermal contact). In this study, the concentrations of the trace elements Cd, Cr, and As in four media were comprehensively evaluated by collecting samples from atmospheric precipitates (A), wheat (W), soil (S), and groundwater (G) in the agricultural plain. This study not only considers the health risk level, but also focuses on the relationship between soil properties and the soil–wheat system. First, according to the results of the analysis, the concentration of carcinogenic elements in atmospheric precipitates was higher than that in other media. The sequence follows the order A > S > W > G. Moreover, the input flux of A was at a relatively higher level (determined via an input flux calculation) than other farming areas. Second, the pollution of Cr, Cd, and As in A and S were analyzed using the geoaccumulation method, and the level of Cd reached mild to moderate pollution. In addition, it was found that the bioaccumulation factors (BAFs) of Cd were much higher than those of As and Cr in the soil–wheat system. Furthermore, it was found that the negative relationship between BAFs and pH, CEC (cation exchange capacity), Corg (soil organic carbon), and clay was significant. Lastly, the hazard quotient (HQ) of the non-carcinogenic risk and carcinogenic risk (CR) of the three elements in multiple media were calculated using the health risk model. The HQ results showed that the total non-carcinogenic risk index (HI) of Cd, As, and Cr in the multiple-media did not exceed the risk limit (1.00), and there was no significant risk to the locally exposed population. However, the total carcinogenic risk index (TCR) indicated that the risk index of Cr, As and Cd in multiple media exceeded the safety index range (≈10⁻⁶–10⁻⁴), and the three elements posed a significant carcinogenic risk to local residents via the main pathways. In terms of individual elements, the risk of cancer was highest via the ingestion of the carcinogenic element Cd in G and W.

Global agricultural intensification leads to a decline in soil quality; however, the extent to which long-term rice cultivation adversely impacts soil, based on chemical and microbial perspectives, remains unclear. The present study was conducted on a seed multiplication farm in Wuchang, Heilongjiang Province, China, to quantify changes in the nutrient properties and microbial profiles of meadow soil in cultivated (rhizosphere and bulk soil) and uncultivated paddy plots from spring to winter. A non-parametric method was used to compare carbon metabolism characteristics among the three groups of soil samples. Principal component analysis was used to distinguish soil chemical properties and carbon source utilization profiles among the soil samples across different seasons. Under rice cultivation, pH, organic matter, total nitrogen, and alkali-hydrolyzed nitrogen concentrations were generally higher in rhizosphere soils than in bulk or uncultivated soils. However, microbial biomass in cultivated soils was consistently lower than in uncultivated soils. There was a discernible difference in carbon substrate preference between summer and other seasons in the three sample groups. In conclusion, agricultural activities in rice cultivation could reshape soil microbial communities in the long term. Notably, specific cultivation activity may induce distinct soil microbial responses, which are more sensitive than chemical responses.

The North China Plain (NCP) is the most populous plain in China and forms the core of the Beijing-Tianjin-Hebei economic circle. With urbanization, anthropogenic heavy metals have increasingly dispersed and accumulated in urban topsoil, especially in hazy cities. To investigate the major sources of haze and their relation to topsoil heavy metals concentrations in cities of the NCP, 220 topsoil samples (0–10 cm) were collected from Shijiazhuang city (capital of Hebei Province). The concentrations of eight selected metals were determined. Statistical and spatial distribution analyses suggest that coal combustion and industrial processes (Ni, Cr, Cd and Hg) were the dominant anthropogenic sources of haze in Shijiazhuang city, followed by vehicle exhausts (Pb, Zn Cu and Hg). Contrastingly, As was derived from parent materials of the NCP. A health risk assessment showed that Pb, Cr and As pose significant non-carcinogenic risks to children (hazard index > 1) via oral ingestion. A potential carcinogenic risk to children (CRs > 10⁻⁴) is also posed by As. While Cd and Hg do not pose health risks in Shijiazhuang city, they may pose important ecological risks as ecological risk factors > 40 were observed, resulting in ecological risk indexes of 150–600 (moderate to considerable ecological risks).

Efficient management of soil nitrogen and phosphorus availability is important for soil fertility and crop productivity, but the field responses of rhizosphere microbial communities to arbuscular mycorrhizal fungi (AMF) and clay-mineral amendments remain unclear. A wheat-field experiment compared four treatments: an untreated control (A), bentonite (B; 39 kg ${\mathrm{plot}}^{-1}$), sepiolite (C; 39 kg ${\mathrm{plot}}^{-1}$), and AMF inoculation (E; 2.25 kg inoculum ${\mathrm{plot}}^{-1}$; 120 spores ${\mathrm{g}}^{-1}$). Each treatment comprised six 4 × 7.5 m plots. Soil physicochemical properties were evaluated using all six plots, whereas rhizosphere microbial sequencing used three plots per treatment (plots 2, 4, and 6; n = 3). Treatment E showed higher mean alkali-hydrolyzable nitrogen (101.50 vs. 93.33 mg ${\mathrm{kg}}^{-1}$) and available phosphorus (56.00 vs. 20.98 mg ${\mathrm{kg}}^{-1}$) than the control, whereas treatment B showed a 32.8% higher mean available potassium. None of the bacterial or AMF alpha-diversity indices differed significantly among treatments. Taxonomic summaries showed descriptive variation among treatments, whereas principal component analysis (PCA) and analysis of similarities (ANOSIM) did not detect significant treatment-level separation of either the bacterial or AMF communities. Shotgun metagenomic annotation, rather than 16S-based functional inference, further showed descriptive differences in nitrogen- and phosphorus-related gene-abundance profiles and functional potential; Pseudomonadota and Actinomycetota accounted for substantial shares of several nutrient-cycling gene categories, while pstB showed comparatively pronounced numerical variation among treatments. These metagenomic profiles represent genetic functional potential and do not demonstrate transcript abundance or metabolic activity. Overall, AMF inoculation and clay-mineral amendments were associated with descriptive differences in nutrient availability, taxonomic profiles, and metagenomic functional potential in alkaline wheat farmland, but significant treatment-level separation of the overall bacterial and AMF communities was not detected.