Wenxiang He

To evaluate the ecological risks of emerging contaminants (ECs) in soils, we systematically investigated the effects of 28 ECs, including organophosphorus esters (OPEs), novel brominated flame retardants (NBFRs), and organic pesticides on five key soil enzyme activities: β‐glucosidase, urease, alkaline phosphatase, arylsulfatase (ARS), and fluorescein diacetate hydrolase (FDA‐H). Among the enzymes tested, ARS activity was enhanced by nearly half of the ECs (13 out of 28), especially by OPEs. However, enzyme kinetic analyses revealed that reduced substrate affinity offsets the increased maximal reaction velocity, resulting in unchanged or even reduced catalytic efficiency. In contrast, FDA‐H activity was generally inhibited, exhibiting the greatest response ratio (0.115), indicating that it was the most sensitive enzyme to pollutant exposure. Notably, 2,4,6‐tribromophenol inhibited ARS via linear mixed inhibition mechanism, with ecological dose (ED ₁₀ ) values ranging from 7.53 to 13.9 mg kg ⁻¹ , whereas isoprocarb suppressed FDA‐H via competitive inhibition, with ED ₁₀ values of 3.97–6.58 mg kg ⁻¹ . Based on the average magnitude of effects on soil enzymatic activities (mean score: 0.113) and the functional index (0.148), NBFRs potentially pose greater ecological risks to overall soil functionality than OPEs or the evaluated organic pesticides. These findings highlight the significant and diverse impacts of ECs on critical soil microbial functions and emphasize the urgent need for further investigation into the ecological effects of NBFRs in terrestrial environments.

Soil organic carbon (SOC) is the largest carbon pool in terrestrial ecosystems and is crucial for regulating climate change dynamics. Yet, the relationship between SOC's chemical structure and microbial community composition remains elusive, especially under varying temperature conditions. This study investigates soil samples from four distinct cropland sites. The samples were incubated at 0, 10, 20, 30 and 40°C for 200 days. High‐throughput sequencing technology and solid‐state ¹³ C nuclear magnetic resonance ( ¹³ C NMR) spectroscopy were employed in the analysis. Additionally, a data assimilation approach was applied to estimate parameters for three C pools (active, slow and passive) based on time‐series data. Results indicated that the Q ₁₀ values of the C pools increased with resistance to decomposition and decreased as incubation temperature rose. SOC cumulative decomposition was positively correlated with alkyl C/O‐alkyl C ratio (A/O_A), reflecting the degree of SOC degradation. The response of the C pool Q ₁₀ , chemical structure and bacterial community composition to temperature was site‐specific. Firmicutes and proteobacteria showed negative correlations with carbohydrates and positive correlations with aromatic C–O. Interestingly, the interaction between C functional groups and the bacterial community only affects changes in soil C within the active pool. Moreover, soil properties (C/N ratio and clay content) and mean annual temperature (MAT) are the main factors regulating active, slow and passive C pools, respectively. This study demonstrates that in agricultural soils, clay content and carbon quality have a more significant impact on SOC decomposition under increasing temperatures than the bacterial community. Our study highlights the roles of soil properties in the carbon pools of agricultural ecosystems. Future research should explore how these factors govern SOC decomposition, which is crucial for developing effective management strategies to address climate change.

Mercury (Hg) is a persistent soil pollutant, and its toxicity can be evaluated using soil enzyme indicators. However, a thorough understanding of how the enzyme resists and remains resilient to Hg stress is essential, as it significantly impacts the accuracy of toxicity assessments. Therefore, it is worthwhile to understand the functional stability of urease in soil under Hg pollution. This study compares the effects of Hg at different concentrations and exposure times on soil urease. Results indicate that soil urease activity was enhanced in the first two hours under low levels of Hg pollution, decreased after six hours of acute Hg pollution, and reached its maximum reduction in 24 hours. The urease in fluvo-aquic soil, with higher soil organic matter showed higher resistance to Hg acute pollution than that in red soil. Over a longer aging process, soil urease activity gradually recovered with time. Hormesis effects were observed in red soil under high Hg stress after 30 days, showing the strong resilience of urease enzyme function to Hg pollution. The ecological dose, ED₁₀, (the Hg concentration causing a 10% reduction in soil urease activity) ranged from 0.09 to 0.59 mg kg⁻¹ under short-term exposure, and was lower than that under a longer aging process (0.28 to 2.71 mg kg⁻¹). Further, aging reduced the Hg ecotoxicity due to decreased Hg availability and the resilience of soil urease activity. This indicates that the risk of Hg pollution estimated by soil urease as an indicator depends on exposure time and enzyme stability. These factors need consideration in heavy metal pollution assessments using soil enzymes.