摘要：
Biological soil crusts (BSCs) widely exists in mudflat environment, which is known to be efficient in capturing heavy metals from aqueous solutions; However, their ability to adsorb cadmium (Cd(II)) is limited due to low capacity and selectivity. To address this limitation, manganese ethylenediamine phosphates (MEPs) nanomaterial were incorporated into the BSCs to enhance Cd(II) uptake. The MEPs nanomaterials attached to BSC significantly improved the adsorption capacity, rate, and selection for Cd(II). The adsorption kinetics of Cd(II) by BSCs and BSCs-MEPs was well described by a pseudo-second-order model, with BSCs-MEPs exhibiting a much higher adsorption capacity for Cd(II) (77.00 mg/g) compared to BSCs (55.44 mg/g). The Cd(II) removal by BSCs-MEPs has been accelerated to 2 stages, in which the film diffusion/intraparticle diffusion/chemical reaction participated in the 1st stage. And another stage was dynamic equilibrium process. The adsorption isotherm of BSCs-MEPs demonstrated superior performance for Cd(II) compared to BSCs across a pH range from 2 to 9. Most importantly, even in the presence of high concentration of Na+ or Ca2+ ions, BSCs-MEPs exhibited preferential adsorption for Cd(II), a result not observed with BSCs alone. Analysis of X-ray photoelectron spectroscopy spectra demonstrated that functional groups (-NH2/-COOH/-OH) played an important role in Cd(II) adsorption, while the MEPs attach to BSCs leading to the -NH3+ deprotonation, thus enhanced the BSCs' affinity toward Cd(II). Furthermore, molecular dynamics simulation clearly showed that diffusion coefficients (D) of Cd(II) were much higher than those of Ca2+ in EPS with abundant -NH2, which were responsible for selective adsorption. These findings might provide a valuable approach for treating Cd-contaminated water bodies.
摘要：
Paddy crusts (PCs) influence seriously on the heavy metal migration and transformation in the paddy field system. However, their quantitative effect on heavy metal accumulation in rice plant has been rarely reported. In this study, the influence of microcystis-dominated PCs on Cd content and physicochemical properties of the surface soil, water and rice plants (Oryza sativa L.) during PCs' overall life cycle was investigated. During the PC growth period (0-15 d), the Cd content in the surface soil (0-10 cm) and water decreased by 10-20% due to the accumulation effect. However, during the perish period (15-35 d), the Cd content in the surface soil and water increased by 20-30%, as Cd stored in the PCs was re-released. Moreover, the decomposition of PCs produced a large amount of low-molecular-weight organic substances (<500 Da), significantly increasing the bioavailable acid-soluble Cd in the surface soil. Finally, the PCs increase 25-80% and 60-85% Cd content in rice root and shoot, respectively. A structural equation model demonstrated that the contribution to the Cd in rice roots in the sequence: Cd in surface water > PC > surface soil. Potted experiments using sandy, clay, sandy loam soil containing 0.8-3.5 mg/kg of Cd collected from six provinces' paddy field in southern China confirmed that PCs increased the Cd accumulation in rice plants by as much as 25-80%. Consequently, the presence of PCs can enhance the Cd concentration in rice plants, and the removing PCs could be a potential effectively approach to reducing Cd content in rice plants.
通讯机构：
[Peng, L ] H;Hunan Agr Univ, Coll Resource & Environm, Changsha 410128, Peoples R China.
关键词：
Bacterial diversity;Environmental factor;Paddy crusts;Random forest;Structural equation model
摘要：
Paddy Crusts (PC) play a pivotal role in the migration and transformation of heavy metals within paddy ecosystems, situated at the critical intersection of air, water, and soil. This study focused on PC samples from heavy metal-contaminated rice paddies in six southern Chinese provinces. It's the first time we've screened and quantified the impact of nutrition, physicochemical properties, and heavy metals on bacterial diversity in PC. Our results highlight the significant influence of zinc, total nitrogen, and soil manganese on bacterial diversity. Using structural equation models, we identified the pathways through which these three types of environmental factors shape bacterial diversity. Heavy metal indicators and physical and chemical indicators exerted a direct negative effect on bacterial diversity in PC, while nutritional indicators had a direct and significant positive effect on bacterial diversity. Variance partitioning analysis revealed heavy metals had the most significant impact, accounting for 7.77% of the total effect. Moreover, the influence of heavy metals on bacterial diversity increased as diversity decreased, ranging from 3.81% to 42.09%. To remediate specific heavy metal pollution, our proposed method involves cultivating indigenous bacteria by controlling these environmental factors, based on an analysis of the interplay among bacterial diversity, environmental variables, and heavy metal bioconcentration factors. These findings enhance our understanding of PC and provide insights into rice field heavy metal pollution mitigation.
摘要：
Although increasing attention has been paid to agronomic measures for reducing the heavy metal load in rice grain, the effects of duckweed-paddy co-cropping technology on the accumulation of cadmium (Cd) in rice grains remain unclear. To investigate its specific effects on Cd accumulation in paddy fields, three types of duckweed-like hydrophyte (DH), Azolla imbricata, Spirodela polyrrhiza, and Lemna minor were chosen for study. Their use resulted in a reduction of Cd content in rice grains from 0.40mg/kg to <0.20mg/kg, with A. imbricata yielding the best results (0.15mg/kg). The three types of DH reduced the available Cd content in the soil by 10% to 35% after the paddy tillering stage. The reduction of available Cd content was attributed to the absorption, high pH, and increase of relative abundance of special bacteria of immobilizing Cd. In addition, DH could regulate soil nitrogen leading to ammonium nitrogen increased from 75mg/kg to 100mg/kg, while nitrate nitrogen decreased from 0.55 to 0.1-0.3mg/kg. The increase of ammonium nitrogen content might induce the low Cd transfer ability in rice plant and then low Cd content in rice grain. This study demonstrated that DH has a good effect on the reduction of the Cd concentration in rice grains. Consequently, duckweed-paddy co-cropping technology offers a potential solution to heavy metal pollution and agricultural non-point source pollution, as it not only reduces Cd levels in rice plants, but also fixes nitrogen, reducing the need for nitrogen application.
摘要：
A field experiment was conducted to investigate the effectiveness and mechanisms of foliar spraying of transpiration inhibitor (TI) and different amounts of rhamnolipid (Rh) on the Cd content in rice grain. The contact angle of TI on the rice leaves was significantly reduced when it was combined with one critical micelle concentration of Rh. The Cd concentration in the rice grain in the presence of TI, TI + 0.5Rh, TI + 1Rh, and TI + 2Rh significantly decreased by 30.8 %, 41.7 %, 49.4 %, and 37.7 % respectively, compared with the control treatment. Specifically, the Cd content with TI + 1Rh was as low as 0.182 +/- 0.009 mg/kg, which meets the national food safety requirements (< 0.2 mg/kg). The rice yield and plant biomass of TI + 1Rh were highest compared to the other treatments, possibly because of the alleviation of oxidative stress due to Cd. The hydroxyl and carboxyl concentrations in the soluble components in the leaf cells for the TI + 1Rh treatment were the highest compared to the other treatments. Our results demonstrated that the foliar spraying of TI + 1Rh is an efficient method to reduce Cd accumulation in rice grain. It holds potential for the future development of safe food production in soils polluted with Cd.
期刊：
Frontiers in Microbiology,2021年12:749946 ISSN：1664-302X
通讯作者：
Peng, L.
作者机构：
Department of Environmental Science and Engineering, Hunan Agricultural University, Changsha, China;Hunan Engineering and Technology Research, Center for Irrigation Water Purification, Changsha, China;[Kuang, Xiaolin; Song, Huijuan; Si, Kangying; Peng, Liang; Chen, Anwei] Department of Environmental Science and Engineering, Hunan Agricultural University, Changsha, China, Hunan Engineering and Technology Research, Center for Irrigation Water Purification, Changsha, China
通讯机构：
[Peng, L.] D;Department of Environmental Science and Engineering, China
摘要：
<jats:p>Due to the biomagnifying effect in the food chains, heavy metals will cause serious harm to the food produced in paddy soil, and then threaten human health. The remediation of soil heavy metals by the addition of amendments is a common method. However, the combination of the two amendments has been less studied and its effect is unknown. In this study, we investigated the effects of different concentrations of a lime and calcium-magnesium phosphate (CMP) amendments metal availability and paddy soil bacteria biodiversity. The experiment proves that the addition of 0.5 and 1.0‰ amendment can effectively reduce cadmium (Cd) availability and the cadmium content in rice to be below 0.2 mg/kg, meeting the national food safety level. The results demonstrate that increasing pH and phosphorous (P) in soil were two important factors decreasing available cadmium. Furthermore, biodiversity analysis of the treated soil showed that the amendment increased biodiversity. Proteobacteria and Chloroflex were the most abundant bacteria at the phylum level, followed by Acidobacterium and Nitrospirae. The abundance of <jats:italic>Bacterodietes</jats:italic>-<jats:italic>vadinHA17</jats:italic>, <jats:italic>Syntrophaceae</jats:italic>, and <jats:italic>Thiobacillus</jats:italic> increased as phosphorous increased. Cadmium passivation might induce those species.</jats:p>
摘要：
The Mg/Al layered double hydroxide (Mg/Al-LDH) intercalated with the [Formula: see text] (MoS4-LDH) impregnated into poly(acrylamide-co-sodium acrylate) (PP) was synthesized as layered double hydroxides-PP (LDHS-PP), whose characterization, adsorption properties and mechanisms were investigated. The maximum adsorption capacity (qm) for Cd(II) was approximately 2789.58 mg/g by 1% LDHS-PP, while it was approximately 1893.09 mg/g by PP, which indicated that the MoS4-LDH greatly improved the Cd(II) uptake for PP in aqueous solution. In strongly acidic conditions ( approximately pH 3.0), there was still a good removal efficiency of about 45.65% by the 1% LDHS-PP, while that of PP was almost zero. At pH 5.0 the removal efficiency increased to 85.17% by the 1% LDHS-PP. The sorption kinetics for the 1% LDHS-PP was described well by a pseudo-second-order kinetic model. X-ray photoelectron spectrometry (XPS) and elemental distribution maps further confirmed the presence of MoS4-LDH in the PP and most of the Cd(II) chemisorption based on the Cd-S bonding. Due to its high removal efficiency and acid resistance, LDHS-PP is a promising in-situ fixation agent for the remediation of agricultural soil polluted with Cd(II) at low pH.
摘要：
<jats:p>An amino-functionalized water-retaining agent (PPM40-NH<jats:sub>2</jats:sub>) and a water-retaining agent lacking functionalization (PPM40) were prepared to investigate their selective Cd(II) removal properties. The affinity for Cd(II) was increased after introducing the amino functional group.
The <jats:italic>SF<jats:sub>Cd/Ca</jats:sub></jats:italic> of PPM40-NH<jats:sub>2</jats:sub> was 3–7 fold higher than that of PPM40 although the <jats:italic>C</jats:italic><jats:sub>Ca</jats:sub> was 100–1000 times higher than that of <jats:italic>C</jats:italic><jats:sub>Cd</jats:sub>. The chelating effect of –COOH and –NH<jats:sub>2</jats:sub> in PPM40-NH<jats:sub>2</jats:sub> corresponded
well with the selective adsorption of Cd(II), as confirmed by simulations. A seed germination experiment demonstrated that PPM40-NH<jats:sub>2</jats:sub> could act as a filter of heavy metals to supply “clean” water for the roots of the <jats:italic>pakchoi</jats:italic> plant. The leaching experiment indicated
that PPM40-NH<jats:sub>2</jats:sub> is an efficient in situ fixation agent for the remediation of agricultural soil contaminated with Cd(II) in the presence of high concentrations of Ca(II) salts.</jats:p>
摘要：
Chitosan-stabilized FeS magnetic (MC-FeS) composites were successfully prepared to address the easily oxidization of FeS and enhance Cr(VI) removal from water. Results showed that the MC-FeS composites enhanced the Cr(VI) removal capacity as compared to bare FeS. Further investigation using X-ray photoelectron spectroscopy showed that FeOOH, S8, Cr2O3, Cr2S3, and a Fe(III)-Cr(III) complex were apparently introduced by Cr(VI), Fe(II), and S(-II), respectively. The sorption kinetics could be interpreted using a pseudo-second-order kinetic model, whereas the isotherms were simulated using the RedlichPeterson isotherm model indicating Cr(VI) removal by MC-FeS composites was a hybrid chemical reactionsorption process. In addition, the MC-FeS composite presented high stability against aging and performed well in a long-term reaction system and typical natural water environment. The effective performance of MC-FeS composites shows their great potential in wastewater remediation contaminated by heavy metals.
摘要：
The ecological implications of livestock production intensification have received sustained attention across the globe. Anaerobic digestion is the main process for livestock waste treatment. However, the ecological consequences of dissolved organic matter originating from anaerobic digestion (AD-DOM) in eutrophic water bodies remain elusive. In this study, the physiological responses of a bloom-forming cyanobacterium, Microcystis aeruginosa, to AD-DOM were investigated. Moreover, the composition of AD-DOM was identified by using thermochemolysis followed by gas chromatography-mass spectrometry (GC-MS) analysis. The growth of M. aeruginosa FACHB905 was not sensitive to low levels (0.625-1.25%, V/V) of AD-DOM but was inhibited by high levels (2.5-5%, V/V) of AD-DOM, resulting from photoinhibition damage to photosystem II (PSII). The main target of AD-DOM in PSII was the electron accepting side (psi(0)) or the electron donor side (phi P-0), depending on time variables. The reactive oxygen species (ROS) level showed a positive correlation with AD-DOM addition; however, it was higher than that of the control for 3.75-5% AD-DOM on the 6th day. The intracellular microcystin contents (including MC-LR and Dha(7)-MC-LR) decreased in response to AD-DOM addition, but extracellular microcystin increased after 6 days of exposure. In addition, GC-MS detection showed that AD-DOM is mainly composed of lignin-derived aromatic compounds, alkanes/alkene, nitrogencontaining compounds, and sterols. The results presented in this study suggested that AD-DOM released from the livestock industry may play a subtle role in affecting harmful algal blooms through level-dependent variables. In addition, the ecological consequences of microcystin released by toxin-producing species under AD-DOM stress are still worth considering. (C) 2019 Elsevier B.V. All rights reserved.
