Extracellular polymeric substance induces biogenesis of vivianite under inorganic phosphate-free conditions

Vivianite is often found in reducing environments rich in iron and phosphorus from organic debris degradation or phosphorus mineral dissolution. The formation of vivianite is essential to the geochemical cycling of phosphorus and iron elements in natural environments. In this study, extracellular polymeric substances (EPS) were selected as the source of phosphorus. Microcosm experiments were conducted to test the evolution of mineralogy during the reduction of polyferric sulfate flocs (PFS) by Shewanella oneidensis MR-1 (S. oneidensis MR-1) at EPS concentrations of 0, 0.03, and 0.3 g/L. Vivianite was found to be the secondary mineral in EPS treatment when there was no phosphate in the media. The EPS DNA served as the phosphorus source and DNA-supplied phosphate could induce the formation of vivianite. EPS impedes PFS aggregation, contains redox proteins and stores electron shuttle, and thus greatly promotes the formation of minerals and enhances the reduction of Fe(III). At EPS concentration of 0, 0.03, and 0.3 g/L, the produced HCl-extractable Fe(II) was 107.9, 111.0, and 115.2 mg/L, respectively. However, when the microcosms remained unstirred, vivianite can be formed without the addition of EPS. In unstirred systems, the EPS secreted by S. oneidensis MR-1 could agglomerate at some areas, resulting in the formation of vivianite in the proximity of microbial cells. It was found that vivianite can be generated biogenetically by S. oneidensis MR-1 strain and EPS may play a key role in iron reduction and concentrating phosphorus in the oligotrophic ecosystems where quiescent conditions prevail.     

Cultivar-dependent rhizobacteria community and cadmium accumulation in rice: Effects on cadmium availability in soils and iron-plaque formation

The association between the rhizospheric microbial community and Cd accumulation in rice is poorly understood. A field trial was conducted to investigate the different rhizobacterial communities of two rice cultivars with high Cd accumulation (HA) and low Cd accumulation (LA) at four growth stages. Results showed that the Cd content in the roots of the HA cultivar was 1.23 - 27.53 higher than that of the LA cultivar (0.08 - 10.5 µg/plant) at four stages. The LA cultivar had a significantly lower Cd availability in rhizosphere and a higher quantity of iron plaque (IP) on the root surface than the HA cultivar at four stages. This resulted in the reduction of Cd concentration in IPs and Cd translocation from IP-to-root. Microbial analysis indicated that the LA cultivar formed a distinct rhizobacterial community from the HA cultivar and had less α-diversity. The rhizosphere of the LA cultivar was enriched in specific bacterial taxa (e.g., Massilia and Bacillus) involved in Cd immobilization by phosphate precipitation and IP formation by iron oxidization. However, the rhizosphere in the HA cultivar assembled abundant sulfur-oxidizing bacteria (e.g., Sulfuricurvum) and iron reduction bacteria (Geobacter). They promoted Cd mobilization and reduced IP formation via the metal redox process. This study reveals a potential approach in which specific rhizobacteria decrease or increase Cd accumulation in rice on contaminated soil and provides a new perspective for secure rice production.     

Identification and characterization of Fe3O4/peroxodisulfate advanced oxidation products from sulfameter

Sulfonamides (SAs) are one of the most widely used antibiotics and their residuals in the environment could cause some negative environmental issues. Advanced oxidation such as Fenton-like reaction has been widely applied in the treatment of SAs polluted water. Degradation rates of 95%-99.7% were achieved in this work for the tested 8 SAs, including sulfisomidine, sulfameter (SME), phthalylsulfathiazole, sulfamethoxypyridazine, sulfamonomethoxine, sulfisoxazole, sulfachloropyridazine, and sulfadimethoxine, in the Fe₃O₄/peroxodisulfate (PDS) oxidation system after the optimization of PDS concentration and pH. Meanwhile, it was found that a lot of unknown oxidation products were formed, which brought up the uncertainty of health risks to the environment, and the identification of these unknown products was critical. Therefore, SME was selected as the model compound, from which the oxidation products were never elucidated, to identify these intermediates/products. With liquid chromatography-high resolution tandem mass spectrometry (LC-HRMS/MS), 10 new products were identified, in which 2-amino-5-methoxypyrimidine (AMP) was confirmed by its standard. The investigation of the oxidation process of SME indicated that most of the products were not stable and the degradation pathways were very complicated as multiple reactions, such as oxidation of the amino group, SO₂ extrusion, and potential cross-reaction occurred simultaneously. Though most of the products were not verified due to the lack of standards, our results could be helpful in the evaluation of the treatment performance of SAs containing wastewater.     

Clean and effective removal of Cl(-I) from strongly acidic wastewater by PbO2

Recycling strongly acidic wastewater as diluted H₂SO₄ after contaminants contained being removed was previously proposed, however, Cl(-I), a kind of contaminant contained in strongly acidic wastewater, is difficult to remove, which severely degrades the quality of recycled H₂SO₄. In this study, the removal of Cl(-I) using PbO₂ was investigated and the involved mechanisms were explored. The removal efficiency of Cl(-I) reached 93.38% at 50℃ when PbO₂/Cl(-I) mole ratio reached 2:1. The identification of reaction products shows that Cl(-I) was oxidized to Cl₂, and PbO₂ was reduced to PbSO₄. Cl₂ was absorbed by NaOH to form NaClO, which was used for the regeneration of PbO₂ from the generated PbSO₄. Cl(-I) was removed through two pathways, i.e., surface oxidation and •OH radical oxidation. •OH generated by the reaction of PbO₂ and OH⁻ plays an important role in Cl(-I) removal. The regenerated PbO₂ had excellent performance to remove Cl(-I) after six-time regeneration. This study provided an in-depth understanding on the effective removal of Cl(-I) by the oxidation method.     

无居民海岛土地开发适宜性动态评价——以福建平潭大屿岛为例

无居民海岛开发与保护是当前我国国土空间开发与海洋可持续发展的重要议題,开发适宜性评价关乎其开发保护格局的优化。本研究以福建平潭大屿岛为例,采用GIS空间分析技术和层次分析法评估海岛开发前（2014年）和开发后（2019年）的土地开发适宜性动态变化。结果表明,2019年现状开发区域占2014年土地适宜性评价中适宜开发区的43.8%,反映现有开发空间格局尚待优化;对比开发前后,适宜开发位置基本不变,但部分开发前的不适宜开发地区转为开发后的限制开发区,说明2019年以后开发潜力增大。研究结果可为大屿岛的空间用途管制以及我国类似无居民海岛的开发与保护提供借鉴。     

不同施肥措施下长江经济带地区农田土壤有机碳含量的变化分析

收集整理1992年1月至2022年5月长江经济带地区长期定位施肥试验文献,提取并整合了其中农田土壤有机碳的资料.采用归一化处理和变化速率的分析方法,研究长期不同施肥措施下长江经济带地区农田土壤有机碳含量的总体变化,并比较3种耕作模式及不同土壤类型下土壤有机碳含量的变化差异,判断分析试验持续年限长短对土壤有机碳动态的影响.结果表明,在长期不同施肥措施下,我国长江经济带地区农田土壤有机碳含量整体呈上升趋势,无机氮肥磷肥配施(NP)、无机氮磷钾肥配施(NPK)、单独施用有机肥(O)和有机无机肥配施(NPKO)处理均能增加农田土壤的有机碳含量,其中以NPKO处理为最大,而单独施用无机氮肥(N)则会降低土壤有机碳含量.旱田、水田和水旱轮作农田土壤有机碳含量变化速率分别为0.22、 0.24和0.16g·(kg·a)^-1,3种耕作模式在土壤固碳效果方面并无显著性差异.O和NPKO处理下所带来的有机碳相对快速增加效应在旱田土壤中的持续年限最高不超过28 a,而在水田及水旱轮作土壤中依然可以持续到28 a以上.在不同的土壤类型下,土壤有机碳含量的变化速率存在着一定的差异,平均有机...     

经济发达县域耕地土壤重金属污染评价及其影响因素分析

通过对昆山市14个区镇91个土壤样品中As、Cd、Cr、Cu、Pb、Ni、Hg、Zn 8种重金属测定分析，对该市耕地土壤重金属污染进行评价并进行重金属污染的影响因素分析。结果表明，昆山市耕地土壤存在不同程度的轻微污染，重金属Cd、Cr、Cu、Pb、Hg、Zn均超过国家土壤背景值，旱地、水田中均以Hg污染范围较广、变异系数较大。综合污染指数表现为水田（115）>旱地（100）。区镇耕地重金属污染评价表明千灯、陆扬、石浦、锦溪、石牌处于警戒值之内，蓬朗、周庄、张浦、正仪、周市、巴城、淀山湖、花桥、陆家轻度污染；昆山市耕地土壤中重金属元素均未超过土壤环境基本容量，能够保证作物品质和农业持续发展。同时，研究表明区域重金属轻微污染具有复合污染的特性，Cd、Pb相关性最高(〖WTBX〗P〖WTBZ〗=0621 0)， Pb与Hg、Cu、Zn、Cu与Cr也有相关性（0438 7、0426 0、0350 9、0394 0），区域重金属的轻微污染受人为因素影响显著，研究指出应加强对区域优先控制污染物Hg、次优先控制污染物Pb、Cd、Zn、Cu、Cr的控制与治理。     

Comparative studies on the concentration of rare earth elements and heavy metals in the atmospheric particulate matter in Beijing, China, and in Delft, The Netherlands

Atmospheric particulate matter (APM) was collected at three sampling sites in Beijing, China, from February to June 1998. The concentrations of rare earth elements (REE) and cobalt (Co), zinc (Zn), copper (Cu), cadmium (Cd) and lead (Pb) in the APM were determined by inductively coupled plasma mass spectrometry (ICP-MS). The results obtained in Beijing, China, were compared to that obtained in Delft, the Netherlands, in 1997. The influence of coal combustion was considered. The results demonstrated that the content of APM, the concentrations of REE and Co, Zn, Cd, Pb in the APM in Beijing, China, were higher than that in Delft, the Netherlands. From the ratios of La to Ce, and La to Sm, which may be used as tracers for the origin of the REE, it is concluded that the origins of REE in China differ from those in the Netherlands.     

Location and migration of cations in Cu(2+)-adsorbed montmorillonite

Locations of Cu2+ ion in Cu(2+)-adsorbed montmorillonite have been studied by electron paramagnetic resonance (EPR), supplemented by X-ray diffraction (XRD) and differential thermal analysis (DTA). In the EPR spectra of Cu(2+)-adsorbed montmorillonite, three signals, corresponding to Cu2+ ion, have been simultaneously recorded. Some Cu2+ ions seemed to replace the original interlayer metal cations and some entered into the hexagonal cavities. A small fraction of Cu2+ ions penetrated into the octahedral vacancies. There were two ways for the adsorption of Cu2+ ion by montmorillonite--exchangeable and specific. On heating, the hydrated Cu2+ ion in the interlayer loses the coordinating water and then enters into the hexagonal cavities. When the heating temperature further increased, dehydroxylation occurs, which facilitates Cu2+ ion in the hexagonal cavities to penetrate into the octahedral vacancies.