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Enclosure fisheries have accommodated the widespread expansion of aquaculture in many lakes throughout the Yangtze Plain (YP), China, for over four decades. Such practices have increased food provision but have also triggered various detrimental environmental consequences. To restore ecosystem functions, the Chinese government recently implemented specific regulations to remove enclosure fences from lakes throughout the YP. However, little information is available on the spatial and temporal distributions of the enclosure fences, particularly in relation to the enforcement of recent policy changes. Using synthetic aperture radar (SAR) satellite images taken between 2002 and 2018, we conducted the first comprehensive assessment of the interannual changes in enclosure fences in 17 large lakes throughout the YP. Consistent decreases in fence density were found in most lakes after 2015; 15 lakes had >50% of their fences removed, while 9 lakes had >90% removed. The timing and implementation of the development and destruction of enclosure fisheries were related to government policy; before 2015, regional dynamics in enclosure fisheries were attributed to provincial policies, whereas the nearly ubiquitous fence demolition after 2015 was likely a response to national policy. This study represents remotely sensed evidence that demonstrates the importance of both local and national environmental policies and their effectiveness in mitigating ongoing human impacts on vulnerable and valuable natural resources. These findings provide valuable baseline information for future lake environmental monitoring and restoration in the YP region, and the methods used here could be applied to other lacustrine and coastal regions experiencing similar aquaculture activities.

The transformation of CuO nanoparticles (NPs) during interaction with Nicotiana tabacum L. cv. bright yellow-2 (BY-2) cells was investigated in this study. CuO NPs were taken up, and transformed into Cu2O, Cu2S and Cu acetate after incubation with plant cells for 12 h based on high resolution transmission electron microscopy and X-ray absorption near-edge spectroscopy analysis. The transformation of CuO NPs initially occurred on cell walls with Cu2O and Cu2S being the main transformation products. Galacturonic acid as an important component of cell walls was mainly responsible for reducing CuO to Cu2O and cysteine for the formation of Cu2S. Cu2+ ions could not be transformed into any Cu-based particles (CuO, Cu2O, or Cu2S) on cell walls. After internalization, CuO NPs could also be transformed into Cu2O and Cu2S through interacting with protoplasts as well as mitochondria, confirming that CuO NPs were able to transform intracellularly. Moreover, Cu2O NPs showed higher toxicity to plant cells as compared to CuO NPs with similar individual sizes, indicating that the transformation of CuO NPs enhanced their toxicity to plant cells. These findings could provide new insights into better understanding the transformation and fate of metal-based NPs in living organisms and environments.

The roles of Al2O3 particles with different morphologies in altering graphene oxide (GO) toxicity to Chlorella pyrenoidosa were investigated. Algal growth inhibition by GO with coexisting Al2O3 particles was much lower than the sum of inhibitions from the individual materials for all the three Al2O3, showing the toxicity mitigation by Al2O3. The lowest GO toxicity was observed at the concentrations of 300, 150, and 100 mg/L for Al2O3 nanoparticles (NPs, 8-10 nm), bulk particles (BPs, 100-300 nm), and fibers (diameter: 10 nm; length: 400 nm), respectively. GO-Al2O3 heteroaggregation was responsible for the observed toxicity reduction. GO-induced algal membrane damage was suppressed by the three types of Al2O3 due to GO-Al2O3 heteroaggregation, and the reduction in intracellular reactive oxygen species generation and physical contact were confirmed as two main mechanisms. Moreover, the exposure sequence of GO and Al2O3 could highly influence the toxicity, and the simultaneous exposure of individual GO and Al2O3 showed the lowest toxicity due to minimum direct contact with algal cells. Humic acid further decreased GO-Al2O3 toxicity due to enhanced steric hindrance through surface coating of GO-Al2O3 heteroaggregates. This work provides new insights into the role of natural mineral particles in altering the environmental risk of GO.

This study investigated the toxicity of CuO nanoparticles (NPs) to Nicotiana tabacum L. cv. Bright Yellow-2 (BY-2) cells. CuO NPs with concentrations higher than 2 mg L−1 began to exhibit significant inhibition of the growth of plant cells, and the 24 h median effective concentration was calculated to be 12 mg L−1. CuO NPs (12 mg L−1) showed much higher toxicity than the released Cu2+ (0.8 mg L−1) and bulk particles (BPs, 12 mg L−1) during all the exposure times (0–24 h). CuO NPs were internalized by plant cells through endocytosis, and then located in the cytoplasm, mitochondria and vacuoles. Under CuO NP exposure, the generation of total reactive oxygen species increased by 38.3% and 40.9% compared with CuO BPs and Cu2+ treatments, respectively. The main radical species were identified as H2O2 and OH˙. CuO NPs significantly reduced the activities of complexes I and III on the mitochondrial electron transport chain, blocked the electron transfer from NADH to ubiquinone, and from ubisemiquinone to ubiquinol, induced oxidative stress, and finally led to membrane damage as indicated by an increase in the contents of malondialdehyde and lactate dehydrogenase. Global gene expression analysis from RNA-sequencing showed that CuO NPs (12 mg L−1) significantly induced the expression of 2692 differentially expressed genes (P-value 2) including 1132 up-regulated and 1560 down-regulated genes in BY-2 cells. The differentially expressed genes related to oxidative stress and mitochondria were identified according to gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis. This work provides insights into the molecular mechanism of nanotoxicity toward plants.

Biochar application in agricultural soils can be highly beneficial to plant productivity. However, how plant productivity response (PPR) [% change of plant yield from control (without biochar application)] to biochar application is affected by biochar properties, soil conditions, and their combinations is still unclear. Therefore, a meta-analysis based on 1254 paired comparisons from 153 published studies was conducted. The grand mean of PPR was estimated to be 16.0 ± 1.3%, regardless of biochar/soil conditions. Meanwhile, a large variation of PPR from −31.8% to 974% was also observed under different biochar or/and soil conditions. Specifically, biochar properties including pH, cation exchange capacity (CEC), contents of carbon and ash, bulk density, and soil conditions including texture, pH, CEC, nitrogen content, and C/N ratio significantly affected the results of PPR to biochar addition. Furthermore, the liming effect, improvement in soil physical structure, and increased nutrient use efficiency were suggested as the key mechanisms for the positive PPR in biochar-amended soils. Moreover, PPR could be significantly affected (strengthened or weakened) by the combined effect of biochar properties and soil conditions. Overall, the application of biochars with high ash content (or low carbon content) into sandy soils or acidic soils is highly recommended for increasing plant productivity. This meta-analysis will provide helpful information to elucidate the combined effect of biochar properties and soil conditions on plant growth, which is critical for developing engineered biochar with specific functionality to promote plant production and food security.

The methods of life cycle assessment and cost-effectiveness analysis were employed to compare the energetic, environmental, and economic performances of three household-based modern bioenergy (MBE) utilization systems: biogas utilization (BGs), biomass briquette utilization for energy only (BBs), and biomass briquette utilization for energy and biochar (BCs). The results showed that all the three MBEs performed positive results in net energy output, which ranged from 0.86 to 3.75 MJ (kg crop residues)−1. The positive greenhouse gas reductions also can be acquired when using these three MBEs to substitute for traditional energy, respectively. The cost-effectiveness values of three MBE systems ranged from 343 RMB (tCO2e)−1 for BGs to 598 RMB (tCO2e)−1 for BCs (the CO2e indicates the CO2 equivalent). Considering the supply index analysis results furtherly, the BGs is regarded as the best strategy for the development of MBE in rural households. However, BG leakage during BG digester operations should be received much greater attention to avoid adverse impacts on GHG mitigation.

We systematically investigated the reduction mechanisms and reduction kinetics of silver ions (Ag ions) by graphene oxide (GO) under ambient condition. UV–vis spectroscopy, transmission electron microscopy, and electron diffraction results revealed that silver nanoparticles (Ag NPs) could be formed from aqueous Ag ions in the presence of GO at pH 8 under light. Formation of Ag NPs increased with increasing pH (7.4, 8, and 9) and temperature (from 30 to 90); however, the increasing ionic strength and dissolved oxygen reduced the Ag NPs yield. The Ag ions reduction by GO followed pseudo-first-order kinetics under both dark and light, and light irradiation significantly accelerated the Ag NPs formation induced by GO. The phenolic-OH on GO was the dominating electron donator for Ag ion reduction in dark. Exposure to light increased the concentration of phenolic-OH on the GO surface, thereby stimulating the reduction rate of Ag ions by GO. In addition, the light induced electron-hole pairs on GO surface and light activated oxygen-centered radicals on GO surface promoted the reduction of adsorbed Ag ions by GO. Our findings provide important information for the role of GO in reducing Ag ions to Ag NPs in aquatic environments, and shed light on understanding the environmental fate and risk of both Ag ions and GO materials.

Crop residue (CR) based-technology has several benefits, including renewable energy production and improvement in the environment and waste biomass management. However, the quantitative assessment of different CR based-technologies in terms of these benefits is limited. In this study, three typical CR-based technologies, CR biochar (CR-BC), CR direct-fired power (CR-DFP), and CR briquette biofuel (CR-BB), were assessed in terms of energy- and environment-related performances using a mixed-unit input-output life cycle assessment method. The results indicated that CR-BB performed better in energy production and air pollution mitigation than the other two technologies. Energy conversion efficiency was suggested as a key factor in determining the potentials of bioenergy production and environmental improvement. Furthermore, based on the energy demand from the Chinese agricultural sector and CR supply in 2012, the energy supply capacity (ESI) of CR-BC, CR-DFP, and CR-BB was estimated to be 24.3, 2.89, and 53.0, respectively, and their total greenhouse gas (GHG) reduction potential (TRGHG) was estimated to be 1.41 × 106, 4.81 × 106, and 1.68 × 106 t CO2e (CO2 equivalent), respectively. Overall, the CR-DFP and CR-BC are recommended for the high-value utilization of CR resources. The findings of this study could provide a basis for the development of CR-based technologies and CR management policy.

Engineered nanoparticles (NPs) are being released into aquatic environments with their increasing applications. In this work, we investigated the interaction of CuO NPs with a floating plant, water hyacinth (Eichhornia crassipes). CuO NPs (50 mg/L) showed significant growth inhibition on both roots and shoots of E. crassipes after 8-day exposure, much higher than that of the bulk CuO particles (50 mg/L) and their corresponding dissolved Cu2+ ions (0.30 mg/L). Scanning electron and light microscopic observations showed that the root caps and meristematic zone of E. Crassipes were severely damaged after CuO NP exposure, with disordered cell arrangement and a destroyed elongation zone of root tips. It is confirmed that CuO NPs could be translocated to shoot from both roots and submerged leaves. As detected by X-ray absorption near-edge spectroscopy analysis (XANES), CuO NPs were observed in roots, submerged leaves, and emerged leaves. Cu2S and other Cu species were also detected in these tissues, providing s...

The aging of biochar by low molecular weight organic acids (LMWOAs), which are typical root-derived exudates, is not well understood. Three LMWOAs (ethanoic, malic, and citric acids) were employed to investigate their aging impacts on the biochars from furfural production residues at 300-600°C (BC300-600). The LMWOAs created abundant macropores in BC300, whereas they significantly increased the mesoporosity and surface area of BC600 by 13.5-27.0% and 44.6-61.5%, respectively. After LMWOA aging, the content of C and H of the biochars increased from 51.3-60.2% and 1.87-3.45% to 56.8-69.9% and 2.06-4.45%, respectively, but the O content decreased from 13.8-24.8% to 7.82-19.4% (except BC300). For carbon fraction in the biochars, the LMWOAs barely altered the bulk and surface functional properties during short-term aging. The LMWOAs facilitated the dissolution of minerals (e.g., K2Mg(PO3)4, AlPO4, and Pb2P2O7) and correspondingly promoted the release of not only plant nutrients (K+, Ca2+, Mg2+, Fe3+, PO43-, and SO42-) but also toxic metals (Al3+ and Pb2+). This research provided systematic insights on the responses of biochar properties to LMWOAs and presented direct evidence for acid activation of inorganic minerals in the biochars by LMWOAs, which could enhance the understanding of environmental behaviors of biochars in rhizosphere soils.

Biochar has been suggested as a potential tailored technology for mediating soil conditions and improving crop yields. However, the efficacies of biochar and biochar-based amendments (e.g., composted biochar) in agricultural soils under a rotation system remain uncertain. In this study, an arable soil was subjected to peanut shell biochar (PBC) and biochar-based amendment (PAD) combined with or without nitrogen (N) fertilizer to evaluate their effects on vegetable yield, N bioavailability, and their relative contribution to vegetable biomass in four consecutive planting seasons. PBC alone or in co-application with N fertilizer had little effect on vegetable yield, while PAD co-application with N fertilizer decreased vegetable biomass because of the inhibition of root morphology by excessive nutrient supply. PBC and PAD applications increased rhizosphere soil pH due to OH– and HCO3– release and NO3−-N uptake. Although the addition of PAD increased soil N contents due to its high contents in PAD, it had little effects on N utilization efficiency (NUE) in the four seasons. The relative contribution of PBC, PAD, and their interaction with N fertilizer to biomass yield was maintained at a low level. Our results indicated that a biochar-based amendment (e.g., PAD) was a potential alternative to N fertilizer, but the ratio of biochar to additives should be managed carefully to generate optimal benefits. Notably, the efficacy of PAD on plant growth was closely associated with plant species, and further related research on different plants is encouraged.

We systematically investigated the toxicity mechanism of three graphene-family materials (GFMs), graphene oxide (GO), reduced graphene oxide (rGO) and multi-layer graphene (MG), to algae (Chlorella pyrenoidosa). GFMs exhibited much higher toxicity than other carbon materials (carbon nanotube and graphite), with the 96 h median effective concentration (EC50) values of 37.3 (GO), 34.0 (rGO), and 62.2 (MG) mg/L. Shading effect contributed approximately 16.4% of growth inhibition by GO due to its higher dispersibility and transformation while the other GFMs did not show any shading effect. Hydrophobic rGO and MG more readily heteroagglomerated with algae than GO, thus likely leading to more direct contacts with algae. Flow cytometry results showed significant decrease of membrane integrity after GFM exposure, and rGO caused the highest membrane damage, which was confirmed by the increased DNA and K+ efflux. The observed membrane damage was caused by a combination of oxidative stress and physical penetration/extraction. Moreover, all the three GFMs could adsorb macronutrients (N, P, Mg, and Ca) from the algal medium, thus leading to nutrient depletion-induced indirect toxicity. GO showed the highest nutrient depletion (53% of total toxicity) due to its abundant functional groups. The information provided in this work will be useful for understanding toxicity mechanism and environmental risk of different GFMs in aquatic environments.

This study investigated the adsorption of cadmium (Cd(II)) by cerium oxide nanoparticles (CeO2 NPs) and oyster shells in seawater. The results showed that the addition of Cd(II) significantly inhibited the agglomeration of CeO2 NPs both in DI water and seawater, increased the positive charges of CeO2 NPs in DI water and neutralized the negative charges of CeO2 NPs in seawater. Additionally, CeO2 NPs could adsorb Cd and the bioavailability of Cd was reduced in the presence of oyster shells. This study demonstrated that the adsorption of metals on shells should not be neglected for the accumulation of metals by shellfish.