Enzhu Hu

Copper (Cu) and sulfur (S)-based compounds have long been used in agriculture, yet their conventional soluble formulations often require repeated application and can contribute to off-target environmental loading. In recent years, nanoforms of Cu and S have been explored as alternative agricultural materials due to their reactivity, release kinetics, and biological interactions, which can differ markedly from those of bulk or ionic counterparts. Building on this progress, this review examines the potential of copper sulfide nanoparticles (CuS NPs) as an emerging material that integrates micronutrient chemistry, redox activity, and nanoscale functionality. The number of studies directly evaluating CuS NPs in agriculture remains relatively limited, but existing reports suggest three main application pathways: as antifungal/antibacterial agents, as nanocarriers for pesticidal active ingredients, and as controlled nutrient-delivery platforms for plant-relevant elements. Several studies have reported promising agronomic performance of CuS NPs compared to Cu-containing NPs and synthetic pesticides. However, results are highly context dependent. This review identifies key gaps in benchmarking, mechanistic validation, and fate assessment under realistic soil–plant exposure scenarios. Such studies are required to strategically design and assess CuS formulations that will deliver tangible agronomic benefits without unacceptable environmental risks.

Elevated tropospheric ozone concentration ([O₃]) may substantially influence the belowground processes of the terrestrial ecosystem. Nevertheless, a comprehensive and quantitative understanding of the responses of soil C and N dynamics to elevated [O₃] remains elusive. In this study, the results of 41 peer-reviewed studies were synthesized using meta-analytic techniques, to quantify the impact of O₃ on ten variables associated with soil C and N, i.e., total C (TC, including soil organic C), total N (TN), dissolved organic C (DOC), ammonia N (NH₄⁺), nitrate N (NO₃^-), microbial biomass C (MBC) and N (MBN), rates of nitrification (NTF) and denitrification (DNF), as well as C/N ratio. The results depicted that all these variables showed significant changes (P < 0.05) with [O₃] increased by 27.6 ± 18.7 nL/L (mean ± SD), including decreases in TC, DOC, TN, NH₄⁺, MBC, MBN and NTF, and increases in C/N, NO₃^- and DNF. The effect sizes of TN, NTF, and DNF were significantly correlated with O₃ fumigation level and experimental duration (P < 0.05). Soil pH and climate were essential in analyses of O₃ impacts on soil C and N. However, the responses of most variables to elevated [O₃] were generally independent of O₃ fumigation method, terrestrial ecosystem type, and additional [CO₂] exposure. The altered soil C and N dynamics under elevated [O₃] may reduce its C sink capacity, and change soil N availability thus impact plant growth and enhance soil N losses.

Elevated tropospheric ozone (O₃) concentration may substantially influence the below-ground processes of terrestrial ecosystems. Nevertheless, a comprehensive and quantitative understanding of O₃ impacts on soil CO₂ emission remains elusive, making the future sources or sinks of soil C uncertain. In this study, 77 pairs of observations (i.e., elevated O₃ concentration treatment versus control) extracted from 16 peer-reviewed studies were synthesized using meta-analysis. The results depicted that soil CO₂ efflux was significantly reduced under short-term O₃ exposure (≤1 year, p < 0.05), while it was increased under extended duration (>1 year, p < 0.05). Particularly, soil CO₂ emission was stimulated in nonagricultural ecosystems, in the free-air CO₂ enrichment (FACE) experiment, and in the soils of lower pH. The effect sizes of soil CO₂ efflux were significantly positively correlated with experimental duration and were significantly negatively correlated with soil pH, respectively. The ozone effect on soil CO₂ efflux would be enhanced at warm temperatures and high precipitation. The duration of O₃ exposure was the fundamental factor in analyzing O₃ impacts on soil CO₂ emission.

The accumulation of microplastics (MPs) in soil and sediments may influence the penetration of contaminants into subsurface environments. However, little attention has been paid to comparing the different roles of two common polyethylene (PE) types—low-density polyethylene (LDPE) and high-density polyethylene (HDPE). In this study, the transport behaviors of tetracycline in saturated quartz sand columns in the presence and absence of these two MPs were investigated, respectively. The results showed that both types of PE MPs restrained the mobility of tetracycline at neutral conditions, while such detrimental effects were weak at acid and alkaline conditions. The degree of nonequilibrium adsorption was higher, and tetracycline transferred easier to the kinetic site for the existence of LDPE than of HDPE. The increased roughness and Brunauer-Emmett-Teller (BET) surface areas, more negative zeta potentials and the formation of oxygen function groups on the surface of MPs after UV-weathering intensified the retardation of tetracycline transport. This study revealed that the PE type and weathering should be taken into account in risk assessment, along with the solution chemistry.

The feedstock type and pyrolytic temperature used in producing biochar influence the characteristics of the obtained product and affect the adsorption behavior of naphthalene. In this study, different biochars were pyrolyzed from wheat straw, soybean straw, and corn straw at four temperatures (400 degrees C to 700 degrees C). Analyses of the elemental composition, pH, ash content, and specific surface area, scanning electron microscopy, and Fourier transform infrared spectroscopy were performed. The adsorption variations of the naphthalene for the different biochars were evaluated. The results showed that as the pyrolytic temperature increased, the carbon content, ash content, and pH of the biochars increased, the hydrophilicity, aromaticity, and polarity decreased, and the naphthalene adsorption was enhanced. The pseudo-second-order model fit the naphthalene adsorption kinetics better. Both the Langmuir and Freundlich isotherm models confirmed that naphthalene adsorption by all of the produced biochars were effective. Under moderate pyrolytic temperatures, the soybean straw-derived biochar showed a greater naphthalene adsorption capacity and faster adsorption rate than the wheat straw- and corn straw-derived biochars. This study provides a theoretical basis for selecting crop residues and optimizing the pyrolytic temperature with a high efficiency of naphthalene removal from water.

Soil contamination with polycyclic aromatic hydrocarbons (PAHs) is a serious problem in Northeast China, especially in the steel industrial area. The objective of this study was to evaluate the feasibility of using basic oxygen furnace (BOF) slag to activate the Fenton-like remediation of PAH-contaminated soil to achieve the objectives of “waste control by waste” and “resource recycling” in Chinese steel industry. The effects of BOF slag dosages, H₂O₂ concentrations, and exothermicity-driven evaporation were evaluated with respect to the removal efficiencies of phenanthrene (Phe) and pyrene (Pyr). Results indicated that PAH oxidation was proportional to the BOF slag dosages and was increased exponentially with H₂O₂ concentrations. Evaporation due to increasing temperature caused by exothermic reaction played an important role in total soil PAH losses. The sequential Fenton-like oxidation with a 3-times application of 15% H₂O₂ and the same BOF slag repeatedly used were able to remove 65.87% of Phe and 58.33% of Pyr, respectively. Soluble iron oxides containing in BOF slag were reduced, while amorphous iron oxide concentration remained stable during the repeated Fenton-like process. Column study mimics real field applications showing high removal efficiencies of Phe (36.05–83.20%) and Pyr (21.79–68.06%) in 30-cm depth of soil profile. The tests on soluble heavy metal concentrations after the reactions with high slag dosage or high H₂O₂ concentration confirmed that BOF slag would not cause heavy metal contamination. Consequently, BOF slag may provide an efficient way for enhancing the Fenton-like based remediation of heavily PAH-polluted soil with little risk on collateral heavy metal contamination. However, an external gas collection and purification equipment would be essential to eliminate the evaporated PAHs.