氢氧化镁共沉淀富集分离ICP-MS测定海水中的稀土元素

本文通过条件优化、标准验证等建立了一种直接在海水中加入NH₃·H₂O溶液使稀土元素与氢氧化镁形成共沉淀富集分离,电感耦合等离子体质谱仪测定海水中14种稀土元素的方法。海水样品通过共沉淀、离心操作后,主要基体物质得到了分离,目标稀土元素实现了富集。氢氧化镁共沉淀富集的条件是1:1 NH₃·H₂O溶液最佳加入量为0.35 mL,沉淀清洗次数为1次,静置时间为5 min。方法对稀土元素的加标回收率为88.7%~107.1%,稀土元素的方法空白为0.008×10-12 ~0.441×10-12,方法定量下限为0.054×10-12~0.423×10-12,RSD为2.8%~8.6%。所建立的方法与海水标准物质NASS-6的测定结果一致,方法具有准确度与精密度高、操作简便快速等优点,可用于大批量海水样品中稀土元素的定量精确测定。     

Underestimation of phosphorus fraction change in the supernatant after phosphorus adsorption onto iron oxides and iron oxide–natural organic matter complexes

The phosphorus(P) fraction distribution and formation mechanism in the supernatant after P adsorption onto iron oxides and iron oxide-humic acid(HA) complexes were analyzed using the ultrafiltration method in this study.With an initial P concentration of 20 mg/L(I =0.01 mol/L and pH = 7),it was shown that the colloid(1 kDa-0.45 μm) component of P accounted for 10.6%,11.6%,6.5%,and 4.0%of remaining total P concentration in the supernatant after P adsorption onto ferrihydrite(FH),goethite(GE),ferrihydrite-humic acid complex(FH-HA),goethite-humic acid complex(GE-HA),respectively.The 1 kDa component of P was still the predominant fraction in the supernatant,and underestimated colloidal P accounted for 2.2%,55.1%,45.5%,and 38.7%of P adsorption onto the solid surface of FH,FH-HA,GE and GE-HA,respectively.Thus,the colloid P could not be neglected.Notably,it could be interpreted that Fe~(3+) hydrolysis from the adsorbents followed by the formation of colloidal hydrous ferric oxide aggregates was the main mechanism for the formation of the colloid P in the supernatant.And colloidal adsorbent particles co-existing in the supernatant were another important reason for it.Additionally,dissolve organic matter dissolved from iron oxide-HA complexes could occupy large adsorption sites of colloidal iron causing less colloid P in the supernatant.Ultimately,we believe that the findings can provide a new way to deeply interpret the geochemical cycling of P,even when considering other contaminants such as organic pollutants,heavy metal ions,and arsenate at the sediment/soil-water interface in the real environment.     

Dissolved nitrous oxide and emission relating to denitrification across the Poyang Lake aquatic continuum

Most aquatic ecosystems contribute elevated N_2 O to atmosphere due to increasing anthropogenic nitrogen loading. To further understand the spatial heterogeneity along an aquatic continuum from the upriver to wetland to lake to downriver, the study was conducted on spatial variations in N_2 O emission along Poyang Lake aquatic continuum during the flood season from 15 July 2013 to 10 August 2013. The results showed the N_2 O concentrations, the ratio of N_2O/dinitrogen(N_2) gases production, N_2 O emission and denitrification rates ranged from 0.10 to 1.11 μg N/L,- 0.007% to 0.051%,- 9.73 to 127 μg N/m2/hr and 1.33 × 104to31.9 × 104μg N_2/m2/hr, respectively, across the continuum. The average N_2 O concentrations,the ratio of N_2O/N_2 and N_2O emission was significantly lower in wetlands as compared to the rivers and lake(p 0.01). The significantly high denitrification rate and low N_2 O emission together highlighted that most N_2 O can be converted into N_2 via near complete denitrification in the Poyang Lake wetlands. Our study suggests that the wetlands might impact N_2 O budget in an integrated aquatic ecosystems. Moreover, N_2 O emission from different aquatic ecosystem should be considered separately when quantifying the regional budget in aquatic ecosystem.     

From illite/smectite clay to mesoporous silicate adsorbent for efficient removal of chlortetracycline from water

A series of mesoporous silicate adsorbents with superior adsorption performance for hazardous chlortetracycline(CTC) were sucessfully prepared via a facile one-pot hydrothermal reaction using low-cost illite/smectite(IS) clay,sodium silicate and magnesium sulfate as the starting materials.In this process,IS clay was "teared up" and then "rebuilt" as new porous silicate adsorbent with high specific surface area of 363.52 m~2/g(about 8.7 folds higher than that of IS clay) and very negative Zeta potential(- 34.5 mV).The inert Si- O- Si(Mg,Al) bonds in crystal framework of IS were broken to form Si(Al)- O~- groups with good adsorption activity,which greatly increased the adsorption sites served for holding much CTC molecules.Systematic evaluation on adsorption properties reveals the optimal silicate adsorbent can adsorb 408.81 mg/g of CTC(only 159.7 mg/g for raw IS clay) and remove 99.3%(only 46.5%for raw IS clay) of CTC from 100 mg/L initial solution(pH 3.51;adsorption temperature 30℃;adsorbent dosage,3 g/L).The adsorption behaviors of CTC onto the adsorbent follows the Langmuir isotherm model,Temkin equation and pseudo second-order kinetic model.The mesopore adsorption,electrostatic attraction and chemical association mainly contribute to the enhanced adsorption properties.As a whole,the high-efficient silicate adsorbent could be candidates to remove CTC from the wastewater with high amounts of CTC.     

Fabrication of mesoporous lignin-based biosorbent from rice straw and its application for heavy-metal-ion removal

Lignocellulosic biomass offers the most abundant renewable resource in replacing traditional fossil resources. However, it is still a major challenge to directly convert the lignin component into value-added materials. The availability of plentiful hydroxyl groups in lignin macromolecules and its unique three-dimensional structure make it an ideal precursor for mesoporous biosorbents. In this work, we reported an environmentally friendly and economically feasible method for the fabrication of mesoporous lignin-based biosorbent (MLBB) from lignocellulosic biomass through a SO₃ micro-thermal-explosion process, as a byproduct of microcrystalline cellulose. BET analysis reveal the average pore-size distribution of 5.50 nm, the average pore value of 0.35 cm³/g, and the specific surface area of 186 m²/g. The physicochemical properties of MLBB were studied by fourier transform infrared spectroscopy (FTIR), attenuated-total-reflection fourier transform infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS), and element analysis. These results showed that there are large amounts of sulfonic functional groups existing on the surface of this biosorbent. Pb(II) was used as a model heavy-metal-ion to demonstrate the technical feasibility for heavy-metal-ion removal. Considering that lignocellulosic biomass is a naturally abundant and renewable resource and SO₃ micro-thermal-explosion is a proven technique, this biosorbent can be easily produced at large scale and become a sustainable and reliable resource for wastewater treatment.     

燃煤小锅炉替代方案论证及效益分析——以济南市为例

通过对燃煤小锅炉各可行替代方案的分析,从环境标准要求、政策要求、环境效益、经济效益和节能等方面,论证了燃煤小锅炉替代的必要性与可行性。结果表明天然气、电和生物质锅炉及集中供热均具有良好的环境效益和经济可行性,可作为燃煤小锅炉的替代方案。济南市通过实施燃煤小锅炉替代,预计将减少烟尘排放量182.61 t/a,减少SO_2排放量898.8 t/a,减少NO_x排放量2 710.7 t/a,与淘汰前燃煤小锅炉排放量相比,分别降低了87.7%、82.9%和86.2%,年可节约折标煤140 903.27 t。节能减排效益显著。可为同类燃煤小锅炉替代工程提供参考。     

贵阳城市环境功能定位研究

环境功能定位是城市环境总体规划的重要组成内容和出发点,同时也是城市维持环境功能、环境形态和环境安全的基础。文章以第二批城市环境总体规划试点城市之一的贵阳市为案例,结合城市环境功能定位的经验方法,从大系统和长周期角度出发,分析了长江流域和长江经济带对贵阳市的环境功能需求,梳理了贵阳市环境问题演变和与工业化、城镇化发展历程之间的相互关系,对比分析了贵阳市在西南地区主要城市中的环境比较优势,最终得出贵阳市的4大环境功能定位。最后分析了贵阳市发挥4大环境功能存在的问题和挑战,并且提出了相应的对策建议。     

CaO2不同投加方式对黑臭河道底泥内源磷释放抑制作用

以S市某黑臭河道底泥和上覆水为研究材料,研究了CaO_2在3种不同投加方式下对内源磷释放的抑制效果.结果表明CaO_2在3种投加方式下,均导致上覆水中pH和DO有所增加.注射条件下,上覆水DO浓度明显低于覆盖,说明注射确实延缓了CaO_2的氧化速度,有利于创造底泥微氧化环境.CaO_2覆盖和注射条件下,上覆水中TP和DIP浓度以及变化趋势基本一致,均明显低于混匀条件.但是,覆盖条件下,间隙水中DIP浓度最高,达到注射条件下的120.33~142.18倍.相反,注射条件下,间隙水中DIP浓度最低,并且上覆水中DIP浓度也较低,说明注射条件下CaO_2对内源磷的释放确有抑制作用,这与其创造的微氧化环境密切相关.底泥中不同形态磷数量分布也证实了这一点.投加CaO_2加快了有机磷的矿化速度,铁铝结合态磷和钙结合态磷也明显增加,使得内源磷持留能力增强.     

不同营养水平下沉水植物的抑藻效应

控制水体的营养盐浓度,尤其是磷浓度,可以控制藻类水华的发生.然而,经济成本很高.相对藻类而言,沉水植物对水体营养盐升高敏感性更低,且沉水植物的存在可以改变藻类的群落结构和生长速率.为探讨沉水植物在营养盐与蓝藻水华控制关系中的作用,本研究探讨了有无水生植物存在下,不同营养盐浓度(磷浓度分别为0.025、0.05、0.1 mg·L~(-1),对应地表水Ⅲ～Ⅴ类)下蓝藻水华暴发(chlorophyll-a10μg·L~(-1))的频率、强度和持续时间.结果表明,初始藻浓度为5μg·L~(-1)和10μg·L~(-1)情况下,3种磷浓度下都会发生水华,磷浓度的升高会导致蓝藻水华暴发的强度和持续时间增加.然而,在加入水生植物金鱼藻后,初始藻浓度为5μg·L~(-1)的条件下,没有形成水华.初始藻浓度为10μg·L~(-1)的条件下,各处理组在实验初始时会形成短暂水华,之后,各处理组的叶绿素a浓度均低于10μg·L~(-1),显示蓝藻生长受到抑制.因此,沉水植物存在情况下,在营养盐较高的水体,蓝藻水华也不会发生.     

我国东北地区地表水酸化现状

2011年8月对我国东北地区东部的溪流进行采样调查,以评价地表水的酸化现状.通过对采集的33个水体pH值和酸中和容量(ANC)的分析发现,只有长白山上少数溪流的pH值低于6.0,而所有采样水体的ANC均高于0.2 meq.L-1,说明该地区尚未大面积发生地表水酸化问题.离子浓度分析结果表明,HCO3-是水体中最主要的阴离子,而SO24-浓度往往小于150μeq.L-1,NO3-浓度更是远低于SO24-,这说明该地区酸沉降污染较轻.但是,东北地区广泛分布着风化速率较低的酸性森林土壤,导致一些水体缓冲酸沉降的能力较弱,水体酸化的可能性仍然存在.以此类推,东北亚目前的酸沉降水平尚不足以产生严重的地表水酸化问题,周边国家不应过分夸大我国排放酸性气体的越境输送导致的环境影响.