Search

Understanding the behavior of colloidal phosphorus (Pcoll) under anoxic conditions is pivotal for addressing soil phosphorus (P) mobilization and transport and its impact on nutrient cycling. Our study investigated Pcolldynamics in acidic floodplain soil during a 30-day flooding event. The sudden oxic-to-anoxic shift led to a significant rise in pore-water Pcolllevels, which exceeded soluble P levels by more than 2.7-fold. Colloidal fractions transitioned from dispersed forms (<220 nm) to colloid-associated microaggregates (>220 nm), as confirmed by electron microscopy. The observed increase in colloidal sizes was paralleled by their heightened ability to form aggregates. Compared to sterile control conditions, anoxia prompted the transformation of initially dispersed colloids into larger particles through microbial activity. Curiously, the 16S rRNA and ITS microbial diversity analysis indicated that fungi were more strongly associated with anoxia-induced colloidal release than bacteria. These microbially induced shifts in Pcolllead to its higher mobility and transport, with direct implications for P release from soil into floodwaters.

Biodegradable silicate nanoconstructs have aroused tremendous interest in cancer therapeutics due to their variable framework composition and versatile functions. Nevertheless, low intratumoral retention still limits their practical application. In this study, oxygen vacancy (OV)-enriched bimetallic silicate nanozymes with Fe–Ca dual active sites via modification of oxidized sodium alginate and gallic acid (GA) loading (OFeCaSA-V@GA) were developed for targeted aggregation-potentiated therapy. The band gap of silica markedly decreased from 2.76 to 1.81 eV by codoping of Fe3+and Ca2+, enabling its excitation by a 650 nm laser to generate reactive oxygen species. The OV that occurred in the hydrothermal synthetic stage of OFeCaSA-V@GA can anchor the metal ions to form an atomic phase, offering a massive fabrication method of single-atom nanozymes. Density functional theory results reveal that the Ca sites can promote the adsorption of H2O2,and Fe sites can accelerate the dissociation of H2O2, thereby realizing a synergetic catalytic effect. More importantly, the targeted delivery of metal ions can induce a morphological transformation at tumor sites, leading to high retention (the highest retention rate is 36.3%) of theranostic components in tumor cells. Thus, this finding may offer an ingenious protocol for designing and engineering highly efficient and long-retention nanodrugs.

The bioavailability for varied-size phosphorus (P)-binding colloids (Pcoll) especially from external P sources in soil terrestrial ecosystems remains unclear. This study evaluated the differential contribution of various-sized biogas slurry (BS)-derived colloids to plant available P uptake in the rhizosphere and the corresponding patterns of phosphatase response. Keeping the same content of total P input (15 mg kg–1), we applied different size-fractioned BS-derived colloids including nanosized colloids (NCs, 1–20 nm), fine-sized colloids (FCs, 20–220 nm), and medium-sized colloids (MCs, 220–450 nm) respectively to conduct a 45-day rice (Oryza sativa L.) rhizotron experiment. During the whole cultivation period, the dynamics of chemical characteristics and P fractions in each experimental rhizosphere soil solution were analyzed. The spatial and temporal dynamics examination of P-transforming enzymes (acid phosphatases) in the rice rhizosphere was visualized by a soil zymography technique after 5, 25, and 45 days of rice transplantation. The results indicated that the acid phosphatase activities and its hot spot areas were significantly 1) correlated with the relative bioavailability of colloidal P (RBAcoll), 2) increased with the colloid-free (truly dissolved P) and BS-derived NC addition, and 3) affected by the plant growth stage. With the nanosized BS colloid addition, the RBAcolland plant biomass were respectively found to be the highest (64% and 1.22 g plant–1), in which the acid phosphatase-catalyzed hydrolysis of organic Pcollplayed an important role. All of the above suggested that nanosized BS-derived colloids are an effective alternative to conventional phosphorus fertilizer for promoting plant P uptake and P bioavailability.

Calcium overload can lead to tumor cell death. However, because of the powerful calcium channel excretory system within tumor cells, simplistic calcium overloads do not allow for an effective antitumor therapy. Hence, the nanoparticles are created with polyethylene glycol (PEG) donor‐modified calcium phosphate (CaP)‐coated, manganese‐doped hollow mesopores Prussian blue (MMPB) encapsulating glucose oxidase (GOx), called GOx@MMPB@CaP‐PEG (GMCP). GMCP with a three‐mode enhancement of intratumor reactive oxygen species (ROS) levels is designed to increase the efficiency of the intracellular calcium overload in tumor cells to enhance its anticancer efficacy. The released exogenous Ca2+and the production of cytotoxic ROS resulting from the perfect circulation of the three‐mode ROS outbreak generation that Fenton/Fenton‐like reaction and consumption of glutathione from Fe2+/Fe3+and Mn2+/Mn3+circle, and amelioration of hypoxia from MMPB‐guided and GOx‐mediated starvation therapy. Photothermal efficacy‐induced heat generation owing to MMPB accelerates the above reactions. Furthermore, abundant ROS contribute to damage to mitochondria, and the calcium channels of efflux Ca2+are inhibited, resulting in a calcium overload. Calcium overload further increases ROS levels and promotes apoptosis of tumor cells to achieve excellent therapy. To overcome the limitation of calcium overload due to calcium channel regulation, a calcium phosphide‐coated Mn‐doped hollow Prussian blue‐derived nanocomposite with a three‐mode enhancement of intratumor cytotoxic reactive oxygen species levels is rationally designed and engineered to increase the efficiency of the intracellular calcium overload in tumor cells and synergize with it to enhance its anticancer efficacy.

Emergent plant biochar modified with Fe(II)/Fe(III) enhanced P adsorption capacity.Canna indicaresidue-derived MB exhibited the best P adsorption efficiency.MBspromoted P adsorption mainly via inner-sphere complexation and electrostatic attraction.P species adsorbed by MBswere mainly orthophosphate followed by orthophosphate monoesters and DNA.

Nano and colloidal particles (1–1000 nm) play important roles in phosphorus (P) migration and loss from agricultural soils; however, little is known about their relative distribution in arable crop soils under varying agricultural geolandscapes at the regional scale. Surface soils (0–20 cm depth) were collected from 15 agricultural fields, including two sites with different carbon input strategies, in Zhejiang Province, China, and water-dispersible nanocolloids (0.6–25 nm), fine colloids (25–160 nm), and medium colloids (160–500 nm) were separated and analyzed using the asymmetrical flow field flow fractionation technique. Three levels of fine-colloidal P content (3583–6142, 859–2612, and 514–653 μg kg–1) were identified at the regional scale. The nanocolloidal fraction correlated with organic carbon (Corg) and calcium (Ca), and the fine colloidal fraction with Corg, silicon (Si), aluminum (Al), and iron (Fe). Significant linear relationships existed between colloidal P and Corg, Si, Al, Fe, and Ca and for nanocolloidal P with Ca. The organic carbon controlled colloidal P saturation, which in turn affected the P carrier ability of colloids. Field-scale organic carbon inputs did not change the overall morphological trends in size fractions of water-dispersible colloids. However, they significantly affected the peak concentration in each of the nano-, fine-, and medium-colloidal P fractions. Application of chemical fertilizer with carbon-based solid manure and/or modified biochar reduced the soil nano-, fine-, and medium-colloidal P content by 30–40%; however,the application of chemical fertilizer with biogas slurry boosted colloidal P formation. This study provides a deep and novel understanding of the forms and composition of colloidal P in agricultural soils and highlights their spatial regulation by soil characteristics and carbon inputs.

Irrigation and fertilization management are important for controlling agricultural soil salinity and increasing productivity in extremely arid regions. The objective of this research was to evaluate the effects of long‐term drip irrigation and organic fertilizer application on soil salinity, fruit quality and yield of jujube [Ziziphus ziziphus(L.) Karst]. We established a 7‐yr field experiment in a desert‐oasis area in Northwest China. Six treatments were performed: CK (conventional irrigation, no fertilizer), CIMF (conventional irrigation, mineral fertilizer), CIOF (conventional irrigation, organic fertilizer), DI (drip irrigation, no fertilizer), DIMF (drip irrigation, mineral fertilizer), and DIOF (drip irrigation, organic fertilizer). The results showed that soil organic carbon (SOC) concentration in soil treated with organic fertilizer increased gradually over years. Treatment DIOF favored the accumulation of SOC with the highest content and stock after 7 yr. Lower salt content in root zone was found in DIOF after 7 yr. The yield of DIOF increased annually and reached an equilibrium level after the fourth year (14.88 to 16.69 Mg ha−1). Total carbohydrate and vitamin C (Vc) of DIOF of fruit were all significantly higher than CIOF and DIMF. The boosted regression tree showed that SOC content had the highest relative contribution rate to jujube yield. Path analysis identified the most important factor affecting SOC in the drip‐fertigation system was the input of organic fertilizer, with path coefficient 0.65. Long‐term combination of drip irrigation and organic fertilizer application would be an effective strategy maintaining productivity and improve fruit quality in extremely arid areas.

Biochar reduced Pcollby 15.5–32.1% in leachate during DRW cycles.Pcolldecreased with increasing phoD- and phoC-harboring microbial communities.Proteobacteria and Cyanobacteria were the key taxa driving Pcollcontent.

The analytical techniques and instrumentation used to assess agricultural and rural nonpoint‐source organic pollution loading are usually complex and expensive. There has been a strong demand for alternative methodologies to determine the presence and composition of organic pollutants and to predict their levels. In the current work, we investigated a simple and inexpensive approach combining excitation–emission matrix and support vector machine that measures pollution and predicts the levels of precursors to disinfection by‐products, which are organic pollutants derived from agricultural and rural nonpoint sources in small watersheds. Through parallel factor analysis, a four‐component model was developed to explain the composition of dissolved organic matter in water impacted by nonpoint‐source pollution. Support vector classification and support vector regression with model components can use fluorescence properties as proxy indicators for nonpoint‐source pollution. When the model components are used as input variables, formation potential of disinfection by‐products can be predicted. This method provides water utilities managers with tools to control pollution, supervise aquatic environments, and ensure the safety of drinking water. Parallel factor (PARAFAC) components are indicators of nonpoint‐source pollution.PARAFAC components can predict disinfection by‐product (DBP) formation potential (FP).Correlation among DBP FPs and PARAFAC components was visualized by ordination diagram.Effects on FPs across PARAFAC components were visualized by ordination diagram.Humic‐ and protein‐like substances were origins of organic nonpoint‐source pollution.

Biochar has attracted widespread attention due to its high carbon (C) content, abundant surface functional groups and porous structure. Numerous studies have shown that biochar has beneficial effects on the soil phosphorus (P) cycle. This article reviewed the current literatures on biochar and the effects of biochar amendments on the soil P cycle. The P biogeochemistry in biochar (e.g., total P content, P speciation, and P stability) that were prepared from several common feedstocks (e.g., animal manure, woody species, herbaceous species, sewage sludge) is highly variable and the pyrolysis-temperature dependent. Furthermore, the effects of biochar on the soil P availability, P speciation, characteristics of P loss in soils, changes in phosphatase activity, P uptake efficiency by plants, and soil P immobilization were discussed in detail. In summary, it is clear that soil P biogeochemical processes are largely influenced by biochar amendments in soils. The mechanisms and processes of P reaction dynamics in biochar amended soils should be further investigated to evaluate the potential sustainable use of biochar in agricultural soils.

Nonpoint sources are difficult to control because their nutrient contribution from different parts of a watershed can vary substantially. Identifying critical source areas of nutrient loss is an important step in watershed pollution mitigation programs. This study sought to use an integrated index model to differentiate between subbasins that serve as critical source areas of N and P nonpoint sources of pollution in China's Tiaoxi watershed. In contrast with previous N and P indices, multiple sources of pollution (i.e., agronomic activity, domestic wastewater, livestock farming, and aquaculture) were considered. Nitrogen and P source factors (i.e., N and P annual export loads) and transport factors were multiplied to determine the overall risk of nutrient loss in the integrated index model. Critical source areas were identified by a higher nutrient loss index. Of the 92 subbasins within the Tiaoxi watershed, 13 were determined to be critical sources for N, 10 for P, and seven for both N and P. Critical source area identification corresponds well with water quality data from the subbasins. The results show the potential use of the integrated index model for prioritizing and targeting watershed pollution mitigation activities at the subbasin level. Multiple nonpoint sources are included in an integrated index model.Critical source areas are identified by higher nutrient loss indices.The model provides information to target watershed pollution mitigation activities.

Nutrient runoff losses from cropping fields can lead to nonpoint source pollution; however, the level of nutrient export is difficult to evaluate, particularly at the regional scale. This study aimed to establish a novel yet simple approach for estimating total nitrogen (TN) and total phosphorus (TP) runoff losses from regional paddy fields. In this approach, temporal changes of nutrient concentrations in floodwater were coupled with runoff‐processing functions in rice (Oryza sativaL.) fields to calculate nutrient runoff losses for three site‐specific field experiments. Validation experiments verified the accuracy of this method. The geographic information system technique was used to upscale and visualize the TN and TP runoff losses from field to regional scales. The results indicated that nutrient runoff losses had significant spatio‐temporal variation characteristics during rice seasons, which were positively related to fertilizer rate and precipitation. The average runoff losses over five study seasons were 20.21 kg N ha−1for TN and 0.76 kg P ha−1for TP. Scenario analysis showed that TN and TP losses dropped by 7.64 and 3.0%, respectively, for each 10% reduction of fertilizer input. For alternate wetting and drying water management, the corresponding reduction ratio was 24.7 and 14.0% respectively. Our results suggest that, although both water and fertilizer management can mitigate nutrient runoff losses, the former is significantly more effective. A new model based on GIS was used to estimate regional nutrient runoff losses from paddy fields.Regional variation of nutrient runoff losses was influenced by rainfall and fertilizer application.Increasing floodwater storage is more advisable than fertilizer reduction to reduce nutrient runoff losses.

Speciation of colloidal P (Pcoll) is vital yet little known. For the first time ever, the P species in readily released colloids from agricultural soils were determined by P K‐edge X‐ray absorption near‐edge structure (XANES) and solution 31P nuclear magnetic resonance (P‐NMR) spectroscopy. Water‐dispersible Pcollwas the dominant fraction of readily released P (<1 μm) from the studied soils cultivated with rice (Oryza sativaL.) (RS; 80.9%) and vegetables (VS; 55.1%). The Pcollin these samples was predominantly in inorganic form, which XANES showed to be moderately labile Fe‐ and Al‐associated P (total 70.4–83.3%) and nonlabile hydroxyapatite (16.8–19.7%). The P‐NMR analysis showed that the dominant organic P compound class in colloids from RS was orthophosphate monoesters, of which inositol hexakisphosphate was the largest component. These results strongly suggested that colloids are richer in stable P forms and poorer in labile and mineralizable P than the bulk soils.

Ultisols in China need phosphorus (P) fertilization to sustain crop production but are prone to P loss in runoff. Balancing P inputs and loss requires detailed information about soil P forms because P speciation influences P cycling. Analytical methods vary in the information they provide on P speciation; thus, we used sequential fractionation (SF), solution 31P nuclear magnetic resonance (P‐NMR), and P K‐edge X‐ray absorption near‐edge structure (XANES) spectroscopy to investigate organic P (Po) and inorganic P (Pi) species in Chinese Ultisols managed for different crops and with different fertilizer inputs in the first study to combine these techniques to characterize soil P. Sequential fractionation showed that moderately labile NaOH‐P was the largest P pool in these soils, Povaried from 20 to 47%, and residual P ranged from 9 to 31%. Deoxyribonucleic acid (1–5%) and myo‐inositol hexakisphosphate (myo‐IHP, 4–10%) were the major Poforms from P‐NMR. Orthophosphate diesters determined by NMR were significantly correlated with labile NaHCO3–Poin SF (r> 0.981; P< 0.001). Soil Piwas shown to be predominantly associated with iron and soluble calcium (Ca) by XANES. Furthermore, XANES identified hydroxyapatite in the soil receiving the highest rates of Ca‐phosphate fertilizer, which had the highest HCl‐P pool by SF, and also identified IHP (7%) in the soil with the highest proportion of myo‐IHP from P‐NMR. These results strongly suggest that a combined use of SF, solution P‐NMR, and P K‐edge XANES spectroscopy will provide the comprehensive information about soil P species needed for effective soil P management.

Phosphorus fertilization may lead to increased P runoff and leaching, contributing to surface water and groundwater pollution. Plots of a 25-yr field study in subtropical China representing eight P fertilization treatments were sampled to determine the effects of P fertilization on P loss potential and correlations among soil test P, soil neutral phosphatase activity, and water P content. Phosphorus fertilization increased soil test P and neutral phosphatase activity in the plow layer compared with P-free fertilization. Total P content of paddy surface water increased with P fertilization, from <0.01 to 0.35 mg L-1. Phosphorus fertilization created P runoff loss risk, especially with the combined application of both inorganic fertilizers and organic amendments. The P runoff loss potential could be reduced or avoided by utilizing physical barriers on field margins to reduce or eliminate runoff. Soil neutral phosphatase activity, soil test P in the 0- to 5-cm layer, and surface water P content were significantly and positively correlated. Soil neutral phosphatase activity contributed to soil test P and the potential of P runoff loss. Fertilization did not affect soil test P or neutral phosphatase activity beneath the plow layer or total P of paddy groundwater at the 100-cm depth. The P content of paddy groundwater was not related to that of surface water, indicating that downward movement of P and P leaching did not occur. The results suggest that paddy wetland ecosystems can store P with proper management, especially for organic amendments.

Effective nutrient management to reduce high N losses and to improve N use efficiency has been an important focus of agricultural and environmental science research. Understanding the influence of duckweed (Lemna minorL.), a common floating macrophyte in flooded rice (Oryza sativaL.) fields, on NH3volatilization and grain yield is required for better management of applied N fertilizer. We conducted an on‐farm experiment with three levels of urea (0, 90, 180 kg urea N ha−1) applied alone or in combination with duckweed. Our results indicate that total ammoniacal‐N concentration, pH, and temperature of the floodwater were significantly lower in the plots with a duckweed cover. As a consequence, NH3volatilization rates were reduced by duckweed from 20.0 to 53.7% and from 19.0 to 33.2% in plots supplied with 90 and 180 kg urea‐N ha−1, respectively. Duckweed increased rice grain yields by approximately 0.7 and 0.7 Mg ha−1(9.8 and 9.4%) in plots supplied with 90 and 180 kg urea N ha−1, respectively. Ammonia losses from urea‐N applications can be reduced and N use efficiencies can be improved by the presence of duckweed in flooded rice fields.

3,4‐Dimethylpyrazole phosphate (DMPP) was validated as an effective nitrification inhibitor to reduce nitrate leaching. Its effects on ammonia (NH3) volatilization were not clear, especially on farmland scale with crop rotations. In this study, on‐farm experiments at the Jiaxing (JX) and Yuhang (YH) sites in Taihu Lake Basin, China were conducted to evaluate the effect of DMPP application on mineral nitrogen (N) (NH4–N and NO3–N) leaching and NH3volatilization losses in a rice–rapeseed cropping system. Treatments included urea alone (UA), urea + 1% DMPP (UD), and no fertilizer (CK). The results show that DMPP reduced NO3–N leaching fluxes by 44.9 to 59.9% and increased NH4–N leaching fluxes by 13.0 to 33.3% at two sites during rice and rape seasons compared with urea alone. Reductions in mineral‐N leaching fluxes by DMPP in two seasons at the JX and YH sites were 9.5 and 14.3 kg N ha−1, respectively, compared with UA treatment. The application of DMPP had no significant effects on NH3volatilization loss fluxes at either site. The rice and rapeseed yields were 5.3 to 7.4% higher in UD plots than in UA plots at two sites. These results that indicate DMPP could reduce leaching losses of mineral‐N from crop fields and promote grain yields by conserving more applied N in soil in rice–rapeseed rotation systems.

Phosphate as one of the most essential components of living systems, robust analytical techniques available for phosphate sensing in natural waters and soils are essential for monitoring and predicting water quality and agronomic evaluation of phosphate. Using cyclic voltammetry, a point-of-use electrochemical sensor zirconium dioxide/zinc oxide/multiple-wall carbon nanotubes/ammonium molybdate tetrahydrate/screen printed electrode (ZrO2/ZnO/MWCNTs/AMT/SPE) was applied to explore the electro-redox reaction of phosphomolybdate complexes on the surface of electrode, which produced a quantitative electrochemical response of phosphate anions. The modification of the electrode surface with ZrO2/ZnO/MWCNTs nanocomposites is able to generate the electroactive species via chemical reaction between molybdenum (Mo(VI)) and the targeted phosphate anions, leading to a sensitive detection technique for trace phosphate with a lower detection limit (LOD = 2.0 × 10–8mol L–1), higher reproducibility, anti-interference, and precision in different soil sources. This system will be of great potential to advance the trace-level understanding of phosphate especially in field environmental analysis.