Combined effects of hydrothermally-altered feldspar and water regime on cadmium minimization in rice.

The accumulation of cadmium (Cd) in grains and edible parts of crops poses a risk to human health. Because rice is the staple food of more than half of the world population, reducing Cd uptake by rice is critical for food safety. HydroPotash (HYP), an innovative potassium fertilizer produced with a hydrothermal process, has the characteristics of immobilizing heavy metals and potential use for remediating Cd-contaminated soils. The objective of this study was to evaluate the HYP as a soil amendment to immobilize Cd in acidic soils and to reduce the accumulation of Cd in rice tissues. The experiment was performed in a greenhouse with a Cecil sandy loam soil (pH 5.3 and spiked with 3 mg Cd kg-1) under either flooding conditions (water level at 4 cm above the soil surface) or at field capacity. Two hydrothermal materials (HYP-1 and HYP-2) were compared with K-feldspar + Ca(OH)2 (the raw material used for producing HYP), Ca(OH)2, zeolite, and a control (without amendment). After 30 days of soil incubation, HydroPotashs, the raw material, and Ca(OH)2 increased both soil solution pH and electrical conductivity. These materials also decreased soluble Cd concentration (up to 99.7%) compared with the control (p < 0.05). After 145 days, regardless of the materials applied, plant growth was favored (up to 35.8%) under the flooded regime. HydroPotash-1 was more effective for increasing dry biomass compared with other amendments under both water regimes. HydroPotashs reduced extractable Cd in soil, Cd content in plant biomass at tillering and maturing stage, and were efficient in minimizing Cd accumulation in rice grains.

Biochar impacts on nutrient dynamics in a subtropical grassland soil: 2. Greenhouse gas emissions.

Land application of biochar reportedly provides many benefits, including reduced risk of nutrient transport, greenhouse gas (GHG) emission mitigation, and increased soil C storage, but additional field validation is needed. We evaluated the effectiveness of biochar in controlling the lability of nutrients in agricultural land. This study was designed to evaluate the impacts of biochar co-applied with various N and P sources on GHG fluxes from a subtropical grassland. Nutrients (inorganic fertilizer and aerobically digested Class B biosolids) were surface applied at a rate of 160 kg plant available N ha-1  yr-1 with or without biochar (applied at 20 Mg ha-1 ). Greenhouse gas (CO2 , CH4 , and N2 O) fluxes were assessed using static chambers and varied significantly, both temporally and with treatments. Greenhouse gas fluxes ranged from 1,247 to 23,160, -0.7 to 42, and -1.4 to 376 mg m-2 d-1 for CO2 , N2 O, and CH4 , respectively. Results of the 3-yr field study demonstrated strong seasonal variability associated with GHG emissions. Nutrient source had no effect on soil CO2 and CH4 emissions, but annual and cumulative (3-yr) N2 O emissions increased with biosolids (8 kg N2 O ha-1  yr-1 ) compared with inorganic fertilizer (5 kg N2 O ha-1  yr-1 ) application. Data suggested that environmental conditions played a more important role on GHG fluxes than nutrient additions. Biochar reduced CO2 emissions modestly (<9%) but had no effects on N2 O and CH4 emissions.

Preparation of highly-conductive pyrogenic carbon-supported zero-valent iron for enhanced Cr(â ¥) reduction.

In this work, electron transfer (ET) moiety of PC was ascertained in chromate (Cr(Ⅵ)) reduction by zero-valent iron supported by pyrogenic carbon (PC) (ZVI/PC) prepared by pyrolysis of hematite (α-Fe2O3)-treated pinewood. X-ray diffraction analysis suggested successive phase transformation of α-Fe2O3→magnetite (Fe3O4)→wustite (FeO)→ZVI (Feo). Raman spectra and Brunauer-Emmett-Teller analysis revealed that ZVI/PC is characterized with more ordered graphitic carbon and greater surface area than pristine PC. Maximal Cr(Ⅵ) removal capacity (pH = 3) as predicted by Langmuir isotherm model were 5.78, 36.12 and 8.39 g kg-1 for PC, ZVI/PC and ZVI, respectively. ZVI/PC maintained significantly greater Cr(Ⅵ) removal capacity than ZVI and PC at pH 3-9, but Cr(Ⅵ) removal dropped rapidly to 6.78 g kg-1 at pH 4 and above. X-ray photoelectron spectroscopy and successive desorption of Cr-laden ZVI/PC and ZVI showed trivalent Cr was the dominant species, suggesting reduction was an important mechanism for Cr(Ⅵ) detoxification. Electrochemical analysis demonstrated that ZVI/PC exhibited greater Tafel corrosion rate and ET quantity, with lower electrical resistance. Besides, Cr(Ⅵ) reduction showed reversal trend with electrical resistance of ZVI/PC. To conclude, ET capacity was closely associated with electrical conductivity of ZVI/PC due to intensified conductive graphitic carbon structure of PC at higher pyrogenic temperatures.

Cadmium absorption and translocation of amaranth (Amaranthus mangostanus L.) affected by iron deficiency.

Amaranth (Amaranthus mangostanus L.) has superior capability for accumulating cadmium (Cd) and has the potential to be used for phytoremediation of Cd contaminated soils. Iron (Fe) is chemically similar to Cd and may mediate Cd-induced physiological or metabolic impacts in plants. The purpose was to investigate the model of time-dependent and concentration-dependent kinetics of Cd absorption under Fe deficiency, understanding the physiological mechanism of Cd absorption in amaranth roots. The kinetic characteristics of Cd uptake by amaranth grown in Cd enriched nutritional solution with or without Fe addition and with methanol-chloroform, carbonyl cyanide 3-chlorophenylhydrazone (CCCP), and lanthanum chloride (LaCl3) were compared using 109Cd2+ isotope labeling technique. The results showed that Cd uptake was time-dependent and about 90-93% of uptake occurred during the first 150 min. The kinetics of Cd uptake showed that two stages were involved. The saturation stage fitted the Michaelis-Menten model when concentrations of Cd were lower than 12.71 µmol/L and then the absorption of Cd by roots was increased linearly during the second stage. Only linear absorption was observed with methanol-chloroform treatment while the metabolic inhibitor CCCP inhibited only the saturation absorption process, and the Ca channel inhibitor LaCl3 partially inhibited the two stages of absorption. These results indicated that the root absorption of 109Cd2+ was enhanced under Fe deficiency which induced more Fe transporters in the root cell membrane, and the Ca channel, apoplastic and symplastic pathways enhanced the Cd absorption in roots.

Magnetic-Sensitive Nanoparticle Self-Assembled Superhydrophobic Biopolymer-Coated Slow-Release Fertilizer: Fabrication, Enhanced Performance, and Mechanism.

Although commercialized slow-release fertilizers coated with petrochemical polymers have revolutionarily promoted agricultural production, more research should be devoted to developing superhydrophobic biopolymer coatings with superb slow-release ability from sustainable and ecofriendly biomaterials. To inform the development of the superhydrophobic biopolymer-coated slow-release fertilizers (SBSF), the slow-release mechanism of SBSF needs to be clarified. Here, the SBSF with superior slow-release performance, water tolerance, and good feasibility for large-scale production was self-assembly fabricated using a simple, solvent-free process. The superhydrophobic surfaces of SBSF with uniformly dispersed Fe3O4 superhydrophobic magnetic-sensitive nanoparticles (SMNs) were self-assembly constructed with the spontaneous migration of Fe3O4 SMNs toward the outermost surface of the liquid coating materials ( i.e., pig fat based polyol and polymethylene polyphenylene isocyanate in a mass ratio 1.2:1) in a magnetic field during the reaction-curing process. The results revealed that SBSF showed longer slow-release longevity (more than 100 days) than those of unmodified biopolymer-coated slow-release fertilizers and excellent durable properties under various external environment conditions. The governing slow-release mechanism of SBSF was clarified by directly observing the atmosphere cushion on the superhydrophobic biopolymer coating using the synchrotron radiation-based X-ray phase-contrast imaging technique. Liquid water only contacts the top of the bulges of the solid surface (10.9%), and air pockets are trapped underneath the liquid (89.1%). The atmosphere cushion allows the slow diffusion of water vapor into the internal urea core of SBSF, which can decrease the nutrient release and enhance the slow-release ability. This self-assembly synthesis of SBSF through the magnetic interaction provides a strategy to fabricate not only ecofriendly biobased slow-release fertilizers but also other superhydrophobic materials for various applications.