Based on the panel data of 63 counties of Zhejiang Province from 2003 to 2017, this paper studied the total-factor substitution efficiency of chemical fertilizer input and its spatial-temporal evolution by using the Super-efficiency DEA(Data Envelopment Analysis) model, locational Gini coefficient and Theil index. And the driving factors of the total-factor substitution efficiency of chemical fertilizer input were analyzed by constructing the Panel Tobit model. The results showed that: the comprehensive efficiency of total-factor substitution for chemical fertilizer input in Zhejiang Province is low, and technical efficiency is the main drive for promoting comprehensive efficiency; Gini coefficient is below the warning line of 0.4, and the difference of substitution efficiency, relatively small, mainly comes from the contribution within the region, and the difference ratio of contribution by the Southwestern Zhejiang is rapidly increasing. In detail, financial investment in agriculture serve as the greatest the driving force, and government chemical fertilizer input subsidies have a significantly negative effect. Therefore, we should improve the subsidy policy system, increase government investment in agricultural infrastructure, adjust the structure of agroindustry and improve the income of rural residents under the premise of reducing the fertilizer input intensity.

Particulate matter (PM) pollution is a serious environmental problem in most of the cities in the Yangtze River Delta region. Plants can effectively filter ambient air by adsorbing PM. However, only a few studies have paid attention to the dynamic changes and seasonal differences in particle retention capacities of plants under long-term pollution. In this study, we investigated the dynamic changes in particle retention capabilities of the evergreen, broad-leaved, greening plants—Euonymus japonicus var. aurea-marginatus and Pittosporum tobira—in spring and summer. We employed an open-top chamber to simulate the severity of the tail gas pollution. The results showed that, both the plants reached a saturated state in 18–21 days, under continuous exposure to pollution (daily concentration of PM₂.₅: 214.64 ± 321.33 μg·cm⁻³). This was 6–8 days longer than that in the field experiments. In spring, the maximum retention of total particulate matter per unit leaf area of E. japonicus var. aurea-marginatus and P. tobira was 188.47 ± 3.72 μg cm⁻² (18 days) and 67.63 ± 2.86 μg cm⁻² (21 days), respectively. In summer, E. japonicus var. aurea-marginatus and P. tobira reached the maximum retention of the particle on the 21st day, with a net increase of 94.10 ± 3.77 μg cm⁻² and 27.81 ± 3.57 μg cm⁻², respectively. Irrespective of season, the particle retention capacity of E. japonicus var. aurea-marginatus was higher than that of P. tobira, and it showed a better effect on reducing the concentration of fine particles in the atmosphere. The particle retention of the two plants was higher in spring than that in summer. E. japonicus var. aurea-marginatus displayed a significant difference in particle retention between the seasons, while P. tobira did not show much difference. These results will provide a foundation for future studies on the dynamic changes and mechanism of particle retention in plants and management practices by employing plants for particle retention in severely polluted areas.

Photocatalysis is a promising method to eliminate hexavalent uranium (U(Ⅵ)) and recycle it from wastewater. However, most of researched photocatalysts are metal-contained, inactive in visible light, and inconvenient to recycle, which unfortunately impedes the further utilization of photocatalytic technology in U(Ⅵ) pollution treatment. Herein, g-C₃N₄ isotype heterojunction with interpenetrated tri-s-triazine structure (ipCN) was prepared by inserting urea into the interlayer of tri-s-triazine planes of thiourea-derived g-C₃N₄ and in-site thermal treating. The synthesized nanocomposites were used to convert soluble U(Ⅵ) ions into U(Ⅳ) sediment under visible light. Experimental and characterization results reveal that ipCN possess larger BET surface area, more negative-charged surface, higher U(Ⅵ) adsorption capability, and more efficient mass diffusion and charges transfer properties. With these excellent characteristics, nearly 98% U(Ⅵ) could be removed within 20 min over ipCN₅:₁ and 92% photoreduction efficiency could also be kept after 7 cycle uses, which were equal to or even superior than most reported metal-based photocatalysts. It is also proven that the configuration of U(Ⅵ) and photogenerated ·O₂⁻ play a significant role in the photocatalytic U(Ⅵ) reduction process, with (UO₂)ₓ(OH)y²ˣ⁻ʸ are more prone to be adsorbed and the photoinduced process of ·O₂⁻ will steal electrons from photocatalysts. Furthermore, with the self-generated ·O₂⁻ and H₂O₂, a green and facile regeneration process of photocatalysts was proposed This work provides a promising scheme to extract U(Ⅵ) from the perspectives of photocatalysts exploitation, photocatalytic reduction, and photocatalysts regeneration, which is meaningful for the sustainable U(Ⅵ) resource recovery and U(Ⅵ) pollution purification.

Sawdust wastes were used as precursors to prepare adsorbents by combustion and pyrolysis for experimental and mechanism studies and determine the potential of biomass extracted from agro-industrial residues for Pb-polluted soil remediation. Pot experiments were conducted on contaminated soils near Pb–Zn mining with sawdust ash (SA) and sawdust biochar (SB) in different proportions and dosage ratios. Studies have indicated that the application of biomass materials can enhance the adsorption, complexation and precipitation of Pb cations in soil and reduce the mobility of Pb. The concentrations of SPLP-Pb and DTPA-extractable Pb in amended soils were the lowest under 1% 1:2 and 5% 1:1 treatment, respectively. Results of fraction extraction and XANES analysis showed that the materials change the main forms of Pb in soil. Moreover, the binding behavior of Pb with organic matter increases the proportion of Pb (Ac)₂, leading to the transformation of high toxicity Pb-compounds into precipitates and complexes. The remediation methods of 2% 1:2 and 5% 1:2 were better than those of other methods in stabilizing Pb in soil. This study indicated that heat-treated sawdust can be used for Pb-polluted soil remediation, which is a type of environmental remediation measure with considerable ecological potential.

Rice (Oryza sativa) tends to accumulate elevated levels of arsenic (As) in grain, threatening food safety and human health. The rice rhizosphere has a micro-environment that differs markedly from the bulk soil. Yet, little is known about how this micro-environment influences the mobility of As in the rhizosphere. Using rhizoboxes with two rice cultivars (cv. Shenyou 957 and Yangdao 6) differing in their radial oxygen loss (ROL), we investigated the in situ transformation of As in the rhizosphere associated with changes in microbial communities and As-related functional genes. Contrary to expectation, dissolved (porewater) As concentrations within the rhizosphere increased by 1.3–2.4 fold compared to the bulk soil during the seedling stage, with the magnitude of this difference gradually decreasing over time. The increased As mobilization in the rhizosphere was associated with increased soluble Fe. This increasing trend was associated with the increased abundance of both Fe-reducing bacteria (FeRB) and As-related functional genes within the rhizosphere. Furthermore, bacterial 16S rRNA gene sequencing data showed that the abundances of Geobacter and Clostridium were 3.1 times and 12.4 times higher in the rhizosphere, respectively. The importance of FeRB was also suggested by the fact that dissolved As concentrations were highly correlated with dissolved Fe concentrations (r² = 0.83) and also with the relative abundance of genus Clostridium_sensu_stricto_10 (r² = 0.85). This study highlights that although the rice rhizosphere favors a more aerobic condition compared to the bulk soil, As is more mobilized in the rhizosphere, and that Geobacter and some species of Clostridium play a critical role in controlling As mobilization in the rhizosphere.

Most aquatic systems show characteristic seasonal fluctuations in the total nutrient pool supporting primary productivity. The nutrient dynamics essentially exacerbate critical demand for the counterpart micronutrients towards achieving ecosystem equilibrium. Herein, the phytoplankton demand for iron (Fe) uptake under high concentration of nitrate-nitrogen during spring in Xiangxi Bay, China, was studied. Our result confirmed that significant Fe concentrations (P = 0.01) in both autumn (0.62 ± 0.02 mgL⁻¹) and winter (0.06 ± 0.03 mgL⁻¹) relative to spring (0.004 ± 0.01 mgL⁻¹) are linked to the low NO₃⁻N paradigms during autumn and winter. As NO₃⁻N showed a sharp increase in spring, a dramatic reduction in the Fe pool was observed in the entire tributary, driving the system to a critical Fe limited condition. Bioassay study involving Fe additions both alone and in combinations led to maximum growth stimulation with biomass as chla (16.44 ± 0.82 μgL⁻¹) and phytoplankton cell density (6.75 × 10⁶ cellsL⁻¹) which differed significantly (P = 0.03) with the control. Further, the study demonstrated that Fe additions triggered biomass productions which increased linearly with cell densities. The P alone addition caused biomass production (15.26 ± 2.51 μgL⁻¹) greater than both NO₃⁻N (9.15 ± 0.66 μgL⁻¹) and NH₄⁺N (13.65 ± 1.68 μgL⁻¹) separate additions but reported a low aggregate cell density (3.18 × 10⁶ cellsL⁻¹). This indicates that nutrient and taxonomic characteristics e.g., high cell pigment contents rather than just the cell bio-volume also determine biomass. The Bacilliarophyta, Chlorophyta, and Cryptophyta with the total extinction of Cyanophyta characterized the bloom in spring. The anthropogenic NO₃⁻N input into XXB would have driven to higher NO₃⁻N than NH₄⁺N situation, and incapacitated the Cyanophyta that preferentially utilize NH₄⁺N. Our study provides a useful report for incorporation into the monitoring programs for prudent management of phytoplankton bloom and pollution across the eutrophic systems.

Hexavalent chromium, Cr(VI), is a heavy metal contaminant and the reduction of Cr(VI) is accompanied by large isotopic fractionation. In this study, the sources of Cr were explored using the Cr isotopic composition of sediments from the Xiaoqing River, a heavily polluted river located in the Shandong Province of China, which flows into Laizhou Bay. The results show that δ⁵³Cr values of the sediments are the highest upstream near the pollution source, and gradually decrease along the river toward the range for igneous reservoirs observed near the estuary. Based on the calculation of authigenic Cr isotopic composition (δ⁵³Crₐᵤₜₕ) using the detrital index and leaching experiments, we suggest that the authigenic Cr in the sample near the pollution source with the highest δ⁵³Crₐᵤₜₕ value mainly comes from the reduction of Cr(VI) discharged by anthropogenic activity, and authigenic Cr in other samples in the midstream with δ⁵³Crₐᵤₜₕ values slightly higher than the range of igneous reservoirs may come from natural oxidative Cr weathering products. By introducing a Rayleigh model, we calculate that at least 31%–55% of Cr(VI) in the river water had been reduced to Cr(III) near the pollution source. Due to the self-purification ability of the river, Cr(VI) was reduced; thus, there is no record of high δ⁵³Crₐᵤₜₕ values in the downstream of the Xiaoqing River and Laizhou Bay, indicating no obvious Cr pollution in these locations. The limited variation of δ⁵³Cr values for samples from a sediment core in Laizhou Bay is also indicative of no obvious Cr pollution in the history. The Cr isotopic compositions of the river sediments are useful for the identification of Cr sources and can be used to advise environmental remediation on Cr pollution.

Silver nanoparticles (AgNP) are commonly used in medical, cosmetics, clothing, and industrial applications for their antibacterial and catalytic properties. As AgNP become more prevalent, the doses to which humans are exposed may increase and pose health risks, particularly through incidental inhalation. This exposure was evaluated through in-vitro methods simulating lung fluids and lung epithelium, and through computational fluid dynamics (CFD) methods of AgNP transport. A high-dose scenario simulated a short-term inhalation of 10 μg AgNP/m³, based on an exposure limit recommended by the National Institute of Occupational Safety and Health for the case of a health-care worker who handles AgNP-infused wound dressings, and regularly wears AgNP-imbedded clothing. Bioaccessibility tests were followed by a Parallel Artificial Membrane Permeability Assay (PAMPA) and supported by CFD models of the lung alveoli, membrane, pores, and blood capillaries. Results indicate that such exposure produces an average and maximum AgNP flux of approximately 4.7 × 10⁻²¹ and 6.5 × 10⁻¹⁹ mol m⁻²·s⁻¹ through lung tissue, respectively, yielding a blood-silver accumulation of 0.46–64 mg per year, which may exceed the lowest adverse effect level of 25 mg for an adult male. Results from in-silico simulations were consistent with values estimated in vitro (within an order of magnitude), which suggest that CFD models may be used effectively to predict silver exposure from inhaled AgNP. Although the average short-term exposure concentrations are 3 orders of magnitude smaller than the reported threshold for mammalian cytotoxicity effects (observed at 5000 ppb), cumulative effects resulting from constant exposure to AgNP may pose risks to human health in the long-term, with predicted bioaccumulation reaching potential toxic effects after only five months of exposure, based on maximum flux.

Previous epidemiological studies have indicated that prenatal exposure to individual metals affect fetal growth. However, the ordinary linear regression has not enough power to assess the mixture effect of multiple metals and cannot capture the possible differences in associations of metal exposures by subgroups of infant birth weight distribution. To investigate the associations of prenatal exposure to metal mixtures with birth weight, and further to assess whether the sensibilities to metal toxicity are dissimilar among infants with poor and normal fetal growth. A total of 16 metals were analyzed in 736 cord samples from a Chinese birth cohort study. Weighted quantile sum regression (WQSR) found the estimate of the metal mixtures was negatively related to birthweight z-score overall [β (95% CI): −0.31 (−0.42, −0.20)], and the major contributors to the mixture index were Cu (39.7%), Ni (18.3%), Mn (14.0%), and Cd (13.1%). Quantile regression showed stronger relations in the tails of birthweight z-score distribution [e.g. the associations of Cu at specific birth weight z-score quantiles were: 10th percentile −0.70 (95% CI: −1.06, −0.35), the 90th percentile −0.35 (95% CI: −0.63, −0.06)]. Our study found that prenatal exposure to Cu, Mn, Ni, and Cd were negatively linked with birthweight z-score. The associations observed were stronger in the tails of birth weight z-score distribution.

Mining is responsible of releasing trace elements to the environment with potential negative effects on wildlife. Traditionally, wildlife exposure assessment has been developed by analyzing mainly environmental compartments or internal tissues. Nowadays, the use of non-destructive matrices such as hair or feathers has increased. Nevertheless, its use in free-living terrestrial mammals or in birds other than raptors or passerines is less frequent. The main objective of our study was to determine the potential for hair and feathers in a rabbit and bird species to be used as non-invasive proxy tissues for assessing internal metal concentrations at polluted sites from mining. We tested whether hair of European rabbit (Oryctolagus cuniculus) and feathers of red-legged partridge (Alectoris rufa) can be used as non-destructive biological monitoring tools of both essential (Cu, Zn) and non-essential (Pb, Cd, As) trace elements in a currently active copper mining site. We found significant different concentrations, particularly in non-essential elements, between reference area and mining site. Non-essential elements Pb and Cd showed higher correlations between tissues and hair/feathers, while few significant patterns were observed for essential elements such as Cu and Zn. Although feathers showed lower levels of correlation with internal tissues than hair, both could be useful as non-destructive biological monitoring tools. Further tissues, and more importantly, hair and feathers allowed discrimination between polluted and reference sites to indicate bioavailability and pollution status. In addition, hair and feathers can be used in monitoring pollution of an active mining site, being specially interesting for biomonitoring a certain period of time in the event of a particular episode of pollution, in addition to the chronic exposure. As occurred with hair in rabbits, feathers seem to be a good compartment to detect differences between a potential polluted area, such the surrounding of an active mine site, and a non-polluted area.