Aluminium speciation in aqueous solutions

Water, Air, & Soil Pollution - An analytical scheme for the speciation of monomeric and polymeric forms of Al in aqueous solutions is presented. After monomer isolation by complexation with...     

Results of the international aqueous mercury speciation intercomparison exercise

Twenty-seven laboratories from around the world agreed to participate in an intercomparison exercise for total Hg (Hg_t) and methyl Hg (MMHg) in pristine lake water. Unfiltered samples from a remote brown water lake in northern Wisconsin (USA) were collected into acid cleaned Teflon^® bottles using ultra-clean sample handling techniques. The samples were acidified in the field with 0.4% by volume of pre-analyzed HCl (12N; <5 pg Hg/mL), and sent to the primary reference laboratory (PRL) by overnight mail. Within one week of receipt, the samples were randomized, and 10% analyzed for Hgt and MMHg at the PRL to verify the homogeneity of the set. Each participating laboratory was then sent 3 randomly selected 1 L bottles, while the PRL retained 30, and the secondary reference laboratory (SRL) retained 12 samples. The participating laboratories were asked to analyze each bottle in triplicate for both Hgt and MMHg, reporting all QA data including blanks, spike recoveries, and detection limits. The PRL analyzed samples in triplicate at both the beginning and the end of the analytical window, to provide a controlled estimate of any changes in concentration or speciation over that time. Of the 23 laboratories that returned results, 18 utilized BrCl oxidation, gold trapping, and cold vapor atomic fluorescence (CVAFS) detection for Hg_t. Four laboratories reported similar techniques, varying either in detector (cold vapor atomic absorption), or wet chemistry. Only 16 laboratories reported MMHg results, with 15 using a variation of the aqueous phase ethylation, GC separation, and CVAFS detection technique. The results show good convergence between the participating labs for both Hg_t and MMHg. For Hgt 18 of 23 labs reported means within 20% of the consensus value and PRL results (1.27±0.18 ng/L and 1.27±0.14 ng/L respectively). For MMHg, 13 of the 16 labs reported results within 20% of either the consensus value (0.420±0.055 ng/L) or the PRL value (0.446±0.041 ng/L).     

黄腐酸和聚天冬氨酸对蕹菜氮素吸收及氮肥去向的影响

为了解黄腐酸(FA)和聚天冬氨酸(PASP)对蕹菜氮素吸收及氮肥去向的影响,采用15N尿素示踪技术,设置不施氮肥(CK),单施尿素(N),尿素配施低、中、高用量的FA和PASP(NF1、NF2、NF3、NP1、NP2、NP3)8个处理,在温室条件下进行盆栽试验。结果表明,与N处理相比,配施FA和PASP后蕹菜地上部鲜重增加了7.46%~17.55%;NP2、NP3和各NF处理显著提高了蕹菜的吸氮量,提高幅度为10.84%~18.25%,其中,蕹菜对非标记氮的吸收量显著增加,且随FA和PASP用量的增大而增加;NF3处理的15N利用率显著低于N处理,其余处理无显著变化;NF2、NF3、NP2和NP3处理的15N损失率比N处理减少了5.41~14.58个百分点;NF2、NF3和NP2处理的15N土壤残留率增加了5.08~20.02个百分点。研究表明,中、高用量的FA和PASP与尿素配施促进了蕹菜对氮素(尤其是非标记氮素)的吸收,同时减少了氮肥的损失,增加了氮肥在土壤中的残留,对土壤氮库的贡献作用显著。     

Seasonal changes of mercury speciation in the coastal sediments

Purpose

Mercury speciation in sediments is linked to environmental conditions and processes. Domination of particular mercury species depends on its source, displays considerable seasonal behavior, and may be further modified due to oxygen levels, icing conditions, or the input of fresh organic matter. The purpose of this study was to examine the coastal area of the Gulf of Gdańsk in terms of mercury contamination and the influence of seasonal environmental changes on its speciation.

Materials and methods

In three highly dynamic coastal sites, mercury speciation in sediments was studied in relation to other environmental parameters (redox conditions, organic matter concentration, bacteria abundance, etc.). Sediment and water samples were collected monthly during a 3-year study. Sequential extraction of sediments was used for identification of four inorganic mercury species: dissolved, bound with fulvic and humic acids, mercury sulfide, and residual fraction. Cold vapor atomic fluorescence spectrometry (CV-AFS) was used for extracts and liquid sample analysis. Total mercury in sediments was measured with atomic absorption spectrometry (AAS). Changes in salinity were analyzed by measurements of chloride and sulfate ion concentrations using ion chromatography. Bacteria number and biomass were measured by direct counting using epifluorescence microscopy.

Results and discussion

Seasonal changes in mercury speciation were observed at all sites and attributed to different processes. Labile mercury fraction contribution varied from 0 to 80%. The speciation patterns varied locally as the stations selected for the study are diversified in terms of anthropogenic impact, water dynamics, and output from land. Mercury concentrations at all stations fluctuated during phytoplankton blooms, icing of marine waters, precipitation, or increased surface runoff from the land. In this local scale, the global climate changes are visible already as environmental conditions in studied area changed in comparison to elder research.

Conclusions

Obtained results suggest that although mercury emissions to the environment have decreased in recent years, local weather conditions, which may be intensified by climate change, seriously affect the bioavailability of past mercury deposits in coastal sediments.

     

A comparison of the structural characteristics of polymaleic acid and a soil fulvic acid

The purpose of this investigation was to compare structural characteristics of PMA with those of FA in order to assess the suitability of PMA to serve as a model for FA. Chemical (elemental analyses, CO₂H group determinations, increases in OCH₃ after methylation, oxidative degradation) and spectroscopic (visible, UV, fluorescence, IR, ¹³CNMR, and ESR) methods were used for this purpose. While PMA was found to resemble FA in a number of characteristics (water solubility, rich in CO₂H groups, dark brown colour), it significantly differed from FA in a number of respects (UV, fluorescence, ¹³CNMR spectra as well in oxidation products). Compared to FA, PMA appeared to be better organized and more homogeneous at the molecular level, richer in olefinic structures and less aromatic. But the chemical structures of both PMA and FA remain largely unknown.     

Sulfur K-edge XANES spectroscopy reveals differences in sulfur speciation of bulk soils, humic acid, fulvic acid, and particle size separates

X-ray absorption near edge structure (XANES) spectra at the sulfur (S) K-edge (E=2472 eV) were compared for bulk soil material, humic and fulvic acid fractions, and different particle size separates from Ah horizons of two arable Luvisols, from an O and a Bs horizon of a Podzol under Norway spruce forest, and from an H horizon of a Histosol (peat bog). In the bulk soil samples, the contribution of reduced organic S (organic mono- and disulfides) to total sulfur increased from 27% to 52%, and the contribution of ester sulfate and SO₄²⁻-S decreased from 39% to 14% of total S in the following order: arable Luvisols Ah—forested Podzol O—Histosol H. This sequence reflects the increasing organic carbon content and the decreasing O₂ availability in that order. Neither sulfonate nor inorganic sulfide was detected in any of the bulk soil samples. For all samples except the Podzol Bs, the XANES spectra of the bulk soils differed considerably from the spectra of the humic and acid fractions of the respective soils, with the latter containing less reduced S (16-44% of total S) and more oxidized S (sulfone S: 19-35%; ester sulfate S: 14-38% of total S). Also the S speciation of most particle size fractions extracted from the Ah horizon of the Viehhausen Luvisol and the Bs horizon of the Podzol was different from that of the bulk soil. For both soils, the contribution of oxidized S species to total S increased and the contribution of sulfoxides and organic mono- and disulfides decreased with decreasing particle size. Thus, sulfur K-edge XANES spectra of alkaline soil extracts, including humic and fulvic acids or of particle size separates are not representative for the S speciation of the original soil sample they are derived from. The differences can be attributed to (i) artificial changes of the sulfur speciation during alkaline extraction (conversion of reduced S into oxidized S, loss of SO₄²⁻ during purification of the extracts by dialysis) or particle size separation (carry-over of water-soluble S, such as SO₄²⁻), but also to (ii) preferential enrichment of oxidized S in hydrophilic water-soluble soil organic matter (ester sulfate) and in the clay fraction of soils (ester sulfate, adsorbed SO₄²⁻).     

Effects of bacteria on metal bioavailability,speciation, and mobility in different metal mine soils: a column study

Purpose  

Successful phytoremediation depends mainly on the bioavailability of heavy metals in the soil. Recently, soil microbes possess several mechanisms that are able to change metal bioavailability in the soil, which provides a new strategy for investigating biogeochemical cycling of metals in contaminated soils. Three metal mines soils with elevated concentrations of Cd, Pb, and Zn from China were applied in this column study to (1) evaluate the effects of metal tolerant bacterial inoculation (Burkholderia cepacia, accession number: AB051408) on metal release, (2) monitor the migration of metals in the rhizospheric horizon (0–20 cm), and (3) investigate metal speciation and sequential fractions in soil.     

Effect of solid-phase speciation on metal mobility and phytoavailability in sludge-amended soil

Sequential extraction was utilized for partitioning Cd, Cr, Ni, and Zn, in soil and sludge samples into five operationally-defined fractions: exchangeable, bound to carbonates, bound to Fe-Mn oxides, bound to organic matter and residual. The highest amounts of Cd, Ni, and Zn, expressed as per cent of the total, were found in the Fe-Mn oxide fraction of the sewage sludge. Chromium was significantly associated with the organic fraction of the sludge. The residue was the most abundant fraction for all metals studied in the untreated soil, and for Cd and Ni in the sludge-treated soil. The concentration of exchangeable Cd and Cr was relatively low in the untreated soil and did not change much after sludge application, whereas the concentrations of exchangeable Zn increased about 50 times and the concentrations of exchangeable Ni doubled in the sludge-treated soil. The lysimetric experiment revealed an increase in Zn and Ni uptake by ryegrass and in the percentage of metals leached from the soil profile after massive sludge application. In contrast only negligible changes were observed for Cd and Cr. The assumption that mobility and biological availability are related to metal speciation was confirmed by the agreement between the distribution pattern of Cd, Cr, Ni and Zn in the soils, the uptake of the metals by plants and their capacity for leaching out from the soils.     

Effects of ammonium sulphate fertilization on arsenic mobility,speciation, and toxicity in soils planted with barley

Journal of Soils and Sediments - Arsenic (As) is one of the most widespread toxic elements, affecting human health through consumption of contaminated water or food. This work studied the effects...     

Effect of fulvic acid on the crystallization of aluminum hydroxides

Effects of addition of increasing amounts of fulvic acid (FA) on the crystallization of aluminum hydroxides from AlCl₃, solution, neutralized to different degrees, were investigated. All systems were allowed to age at 30°C for 70 days.In the absence of FA, gibbsite was formed at pH 6, a mixture of nordstrandite and bayerite at pH 8, and bayerite crystallized at pH 10. At pH 6 and 8, the addition of increasing amounts of FA (up to 10 mg/l or $\text{FA/Al molar ratio}\text{? 10}{}^{\mathrm{?2}}$) first delayed and then inhibited the crystallization of these aluminum-hydroxide polymorphs but tended to favor the crystallization of pseudoboehmite, an aluminum oxyhydroxide. At pH 10, the addition of FA totally inhibited crystallization and precipitation.Our data suggest that FA so strongly complexes Al that it prevents its full hydroxylation to Al(OH)₃. Another explanation is that the action of FA on the crystallization of aluminum hydroxides resembles that of salts in that FA appears to favor the formation of Al-O-Al (oxo) over that of

(ol) linkages. Either reaction mechanism throws new light on the genesis of some bauxites, which consist of submicroscopic boehmite-like particles which are very similar to pseudoboehmite.     

Alkaline cupric oxide oxidation of a methylated fulvic acid

Fulvic acid, (FA), extracted from the Bh horizon of a Podzol soil, was methylated and then oxidized with alkaline cupric oxide. The oxidation products were extracted into organic solvents, remethylated and separated by column-, thin layer-, and preparative gas chromatography into relatively pure components, which were identified by matching their mass and i.r. spectra and gas Chromatographic retention times with those of authentic specimens.The degradation products isolated and identified accounted for approximately 18 per cent of the weight of the initial methylated FA. Major oxidation products were: (a) methylated phenolic aldehydes and esters (66.9 per cent): (b) benzenecarboxylic acid methyl esters (14.6 per cent): (c) aliphatic dicarboxylic acid methyl esters (2.7 per cent): and (d) adsorbed materials such as n-alkanes (0.3 per cent), n-fatty acid methyl esters (0.3 per cent) and dioetyl adipate (15.2 per cent). The oxidalive degradation of methylated FA indicates the presence of two types of basic structural units: (1) those yielding phenolic aldehydes and esters, and (2) those producing benzenecarboxylic acids. Alkaline cupric oxide oxidation of methylated FA is relatively selective for the isolation of the phenolic components and appears to be a promising technique for structural investigations on humic substances.     

雪被斑块对高山森林凋落叶腐殖化过程中胡敏酸和富里酸累积的影响

高山森林凋落叶腐殖化过程中胡敏酸(Humic acid,HA)、富里酸(Fulvic acid,FA)等腐殖物质的累积是土壤形成和碳吸存的重要途径,并可能受到冬季不同厚度雪被斑块的影响,但一直缺乏必要关注。本文采用凋落物网袋法,于2012/2013年冬季研究了川西高山森林天然形成的不同厚度雪被斑块(厚雪被、中雪被、薄雪被和无雪被)下优势树种岷江冷杉(Abies faxoniana)、方枝柏(Sabina saltuaria)、四川红杉(Larix mastersiana)、红桦(Betula albo-sinensis)、康定柳(Salix paraplesia)和高山杜鹃(Rhododendron lapponicum)凋落叶在不同雪被关键期(雪被形成期、雪被覆盖期和雪被融化期)腐殖化过程中胡敏酸和富里酸累积特征。结果表明:经过一个冬季,6种凋落叶胡敏酸碳和富里酸碳含量在各雪被关键期均表现出随雪被厚度减少而增加的趋势,而净累积量表现出在雪被形成期和融化期随雪被厚度减少而增加、在雪被覆盖期随雪被厚度减少而减少的趋势,且均受到凋落叶初始酸不溶性组分含量的影响。同时,不同雪被斑块下6种凋落叶胡敏酸碳均累积且净累积量为四川红杉康定柳岷江冷杉高山杜鹃红桦方枝柏,而除红桦外的其他5种凋落叶富里酸碳均出现不同程度的降解且降解量为四川红杉高山杜鹃康定柳方枝柏岷江冷杉红桦。这些结果清晰地表明,未来气候变暖情景下冬季雪被的减少可能促进高山森林凋落叶腐殖质累积,但在雪被覆盖不同时期受到雪被斑块特征和凋落叶基质质量的调控。     

Cationic speciation in nutrient solutions as a function of pH

The pH of a nutrient solution is a property that is inherent to its composition. Changing the pH of a nutrient solution affects its composition, elemental speciation and bioavailability. The term ‘speciation” indicates the distribution of elements among their various chemical and physical forms like: free ions, soluble complexes, chelates, ion pairs, solid and gaseous phases, and different oxidation states. For a standard nutrient solution elemental speciation is calculated for a pH range from 2 to 9. For each cation the formation of precipitates, ion pairs, complexes, and chelates is illustrated as a function of pH. The calculation of elemental speciation in nutrient solutions is an indispensable tool in the design, the analysis and the interpretation of experiments with the mineral composition of nutrient solutions in plant nutritional research.     

不同分子量黄腐酸对冬小麦生长和养分吸收利用的影响

【目的】黄腐酸在作物生产中有较为显著的促生、抗逆作用,但黄腐酸的结构复杂、分子量分布宽,影响其效果的稳定性。因此,我们研究了不同分子量黄腐酸对冬小麦生长和养分吸收利用的影响。【方法】采用生物半透膜将黄腐酸按分子量分为<3000 D (W1)、3000～10000 D (W2)和>10000 D (W3) 3个等级,对其进行结构分析,并进行冬小麦盆栽试验。在小麦拔节期将黄腐酸溶液施入土壤中,每个分子量的黄腐酸均设置0(CK)、10 (C1)、25 (C2)、50 (C3) mg/kg共4个施用量。在冬小麦开花期和成熟期采集植株样品和土壤样品,测量生物量、产量和养分含量等指标。【结果】结构分析表明,W1和W2的芳香烃饱和度更低,含氧官能团更多,侧链更发达,并且具有更高的亲水性。与对照相比,施用不同分子量黄腐酸均显著提高了冬小麦籽粒产量(21.62%～49.06%)、籽粒铁浓度(62.81%～100.67%)、籽粒氮累积量(19.47%～38.49%),提高了氮吸收效率(10.67%～19.66%)和氮肥偏生产力(21.63%～49.07%)。施用W1,以上各指标随黄腐酸施用量的...     

黄腐酸添加量对低氮胁迫下小麦生长和根系形态的影响

【目的】黄腐酸(FA)是腐植酸中分子量较小、活性最大的组分,作为一种生物刺激素,FA可以促进植物生长,提高植株的抗逆性。研究黄腐酸不同添加量对低氮胁迫下小麦生长及根系形态的影响,为小麦减氮增效提供实践和理论参考。【方法】以小麦品种‘鑫华麦818’为材料进行了水培试验。将营养液氮浓度调节为硝态氮0.1 mmol/L模拟低氮胁迫(LN),并分别设置FA添加量0、30、60、90、120 mg/L,即LN-FA0、LN-FA30、LN-FA60、LN-FA90、LN-FA120,共5个处理;以正常供氮营养液(硝态氮4 mmol/L)为对照(NN)。分析了小麦根系形态、植株生物量、植株氮浓度、氮累积量、叶片氮代谢关键酶活性等指标。【结果】与LN-FA0相比,LN-FA30、LN-FA60、LN-FA90和LN-FA120处理的地上部生物量分别提高了16.31%、23.18%、26.75%和35.16%,LN-FA120的地上部生物量与正常氮处理已无显著差异;LN-FA30、LN-FA60和LNFA90总根长增加了35.00%～44.67%,根表面积增加了39.93%～95.42%,根体积增加了...     

Multielement analysis and mercury speciation in atmospheric samples from the Toronto area

Inductively coupled plasma atomic emission spectrometry. (ICP-AES), graphite furnace atomic absorption (GFAAS) and gas chromatography with an atomic absorption detector (GC-AAS) were used for the analysis of atmospheric samples collected in the Toronto area of Southern Ontario. Airborne particulate matter and particulate and soluble fractions of snow were analyzed for S, Al, Fe, Ca, Mg, P, Pb, Zn, Cu, Cr, Cd, Ni, As, and Hg. Also, determinations of organic Hg compounds in filtered snow were performed. The element concentrations in airborne particulate matter from Toronto were similar in amount to those found in other major cities and were the highest in winter. Regional differences in the chemical composition of snow were shown to be related to industrial density. The majority of elements existed in the highest concentrations in the soluble fraction of snow, except for Al, Fe, and Pb, which were largely present in particulate matter. Differences in the distribution of elements in particulate matter in fresh and old snow were observed and depended on particle size and element. The results demonstrated the usefulness of snow as an indicator of atmospheric pollution.     

生化黄腐酸对不同质地苏打盐碱土水盐运移特征的影响

为了探讨生化黄腐酸（biochemical fulvic acid, BFA）对不同质地（砂质壤土和壤质砂土）苏打盐碱土的改良作用机理,明确BFA对不同质地苏打盐碱土水盐运移特征的影响,该研究通过室内一维垂直入渗试验,对不同BFA施加量（0（CK）、1、2、4、8 g/kg）条件下土壤水盐运移特征、入渗模型参数和土壤八大盐分离子的变化特征进行了研究。结果表明：对于砂质壤土,当入渗至280 min时,与CK相比,BFA施加量为1、2、4、8 g/kg处理的累积入渗量分别减小了3.70%、10.19%、12.04%、25.00%,湿润峰深度分别减小了9.33%、17.00%、24.00%、27.33%;对于壤质砂土,当入渗至40 min时,与CK相比,BFA施加量为1、2、4、8 g/kg处理的累积入渗量分别减小了1.36%、10.51%、18.98%、29.83%,湿润峰深度分别减小了5.00%、11.33%、21.67%、31.33%。土壤水分入渗速率会随着BFA施加量的增加而减小,在0、5、10、15、20、25、30 cm土层深度,8 g/kg施加量处理的砂质壤土含水率分别高于CK处理11.43%、4.99%、8.54%、8.79%、9.02%、4.98%、-7.76%,而壤质砂土含水率分别高于CK处理4.76%、9.28%、6.18%、9.25%、8.05%、8.77%、-0.06%。Kostiakov和Philip模型均能较好地模拟土壤水分入渗过程,且随着BFA施加量的增加,吸渗率逐渐减小。然而施加BFA同样会增加不同深度土层的含盐量,在土壤钙离子、镁离子浓度较低的情况下,可能会使得土壤中富集钠离子。因此,施加BFA能够改变不同质地苏打盐碱土的水盐运移特征,为了防止施加BFA加剧土壤的次生盐碱化以及考虑施加BFA后的经济效益,该研究推荐BFA施加量为2～4 g/kg时对于不同质地苏打盐碱土具有更好的改良效果。     

Uptake and speciation of mercury and selenium in vegetable crops grown on compost-treated soil

The uptake and speciation of Hg and Se were assessed for the edible portion of 16 different vegetable crops grown on a garden plot which had been exclusively treated with residential compost for 6 yr. This study was conducted under actual field conditions typical of residential gardening and utilized organic gardening techniques. Crops had methylmercury levels averaging 12.8 % of the total edible tissue Hg content, divalent inorganic Hg being the only other element form identified. An average of 20.0% of the total Se content was present as hexavalent Se, the remainder being divalent and tetravalent Se forms. In terms of plant/soil concentration factors, Se was more readily assimilated by crops than Hg.     

控释尿素配施黄腐酸对小麦产量及土壤养分供应的影响

【目的】 控释尿素可调控氮素缓慢释放使其与作物养分吸收速率基本同步,黄腐酸可调控土壤与肥料养分转化,两者均能显著提高肥料利用率,然而控释尿素配伍黄腐酸对小麦的协同增效研究鲜有报道。本文研究控释尿素配施黄腐酸对小麦产量和土壤肥力的影响,为其科学施用提供依据。 【方法】 以小麦 (Triticum aestivum L.) 为试材进行了盆栽试验,供试土壤为棕壤。试验设不施氮 (CK)、尿素全量 (U)、尿素减量1/3(U2/3)、尿素全量及减量配施黄腐酸 (U + FA、U2/3 + FA)、控释尿素全量及减量 (CRU、CRU2/3)、控释尿素全量和减量配施黄腐酸 (CRU + FA、CRU2/3 + FA) 共9个处理。所有处理P₂O₅ 和K₂O施入量均为150 kg/hm2和75 kg/hm2,尿素全量处理为N 225 kg/hm2,黄腐酸处理黄腐酸用量为45 kg/hm2。控释尿素处理均为一次性基施,普通尿素处理于拔节期追施尿素,基追比为1∶1。于小麦苗期、返青期、拔节期、开花期和成熟期取0—20 cm土壤样品,测定土壤硝态氮、铵态氮含量,同时测定株高和叶片SPAD值,收获期调查了小麦产量和土壤养分含量。 【结果】 1) 控释尿素CRU、CRU2/3较等氮尿素U、U2/3处理产量平均显著增加7.3%,净收益显著提高24.9%;CRU2/3与处理U产量差异不显著;CRU + FA较CRU显著增产6.4%,净收益显著增加12.6%;与U2/3处理相比,U2/3 + FA显著增产10.6%;U + FA较U处理显著减产12.8%。2) 等氮条件下,CRU、CRU2/3处理与U、U2/3处理小麦株高、叶片SPAD值差异不显著,CRU + FA、CRU2/3 + FA与CRU、CRU2/3处理间差异均不显著。3) 拔节期,CRU、CRU2/3处理土壤硝态氮含量比等氮U、U2/3处理平均显著高出54.7%,CRU2/3处理与U处理差异不显著;配施黄腐酸处理U + FA、U2/3 + FA、CRU + FA、CRU2/3 + FA的土壤有效磷含量均呈现先降低后增加最后降低的趋势,拔节期CRU处理的土壤有效磷含量与U处理无显著差异,CRU2/3、U2/3 + FA的土壤有效磷含量较CRU处理显著提高了18.6% 和20.6%;拔节期U + FA、U2/3 + FA较等氮U、U2/3处理土壤pH平均显著降低了0.11个单位,其他时期U + FA和CRU + FA处理与等量单施化肥处理差异不显著。 【结论】 控释尿素配施黄腐酸可协同增效,满足小麦各生育期氮素需求,一次性基施显著提高小麦中后期土壤养分供应强度,显著提高了小麦产量、肥料利用率和净收益。