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1.
We determined the sorption of 2,4‐dichlorophenol (DCP), 2,4,5‐trichlorophenol (TCP) and pentachlorophenol (PCP) to dissolved (DOM) and particulate soil organic matter (POM) from the same soil in controlled equilibrium systems, using 14C‐labelled chlorophenols in combination with reversed‐phase high‐performance liquid chromatography (RP‐HPLC) and liquid scintillation. Associations of DCP, TCP and PCP to DOM and POM were satisfactorily described by linear adsorption isotherms. Together with the absence of substantial competition between DCP and TCP for binding sites, this indicates a hydrophobic partitioning mechanism. The organic carbon normalized partitioning coefficient (KOC) for the binding of DCP was similar in magnitude for POM (KPOC) and for DOM (KDOC), whereas KPOC for the more hydrophobic compounds TCP and PCP were approximately one order of magnitude greater than KDOC. On the basis of the relationships between log KOC and the organic carbon normalized partitioning coefficient (log KOW), the extent of association to POM increases more with the hydrophobicity of the chlorophenol than the extent of association to DOM. This holds for our data obtained for DOM and POM of similar origin, as well as for various sources of POM and DOM reported in the literature. Differences in the magnitude of KPOC and KDOC in our study could not be accounted for by differences in gross carbon chemistry of POM and DOM, as determined by nuclear magnetic resonance (13C‐NMR) and X‐ray photoelectron spectroscopy (XPS). Thus, other factors such as the average size and capacity of hydrophobic moieties could explain differences in chlorophenol association between POM and DOM. We conclude that KPOC and KDOC need to be determined explicitly, when the transport and retention of chlorophenols is modelled, and not calculated from relationships between log KOC and log KOW.  相似文献   

2.
We investigated dissolved organic matter (DOM) from soil, sewage sludges, water from waste disposal sites, and composts as sorbents and potential carriers for hydrophobic polycyclic aromatic hydrocarbons (PAHs) in soil. Partition coefficients (expressed log KDOC) for two 5-ring compounds were 4·8–4·9 for DOM from soil, 4·5–47 from composts, and 4·3–4·4 from sewage sludges. The DOM from compost and sewage sludge can influence the transport of non-ionic organic contaminants because of the large concentrations of dissolved organic carbon (DOC) released from these materials. Leachates from waste disposal sites did not sorb PAHs. The DOM from compost contained a large percentage of organic molecules > 14 000 Da (32–46%), whereas DOM from waste disposal leachates contained only 7-lo%, and so bound less PAHs. The percentage of total hydrophobic components, as characterized by XAD-8 chromatography, was 50 ± 9% for most of the DOM solutions and did not express the differences in affinity of the organic sorbents to PAHs in the same way as the KDOC values. Isolated molecular-weight fractions of DOM from composts sorbed benzo(k)fluoranthene in each fraction. The log KDOC values were 4·1–4·3 for both fractions, < 1000 and 1000–14 000 Da, and 4·8–5·0 for the fraction > 14 000 Da. The interaction of PAHs with DOM < 1000 Da cannot be explained by partitioning within intramolecular nonpolar environments of dissolved macromolecules; rather it seems to be due to the amphoteric properties of DOM. This type of interaction of PAHs with small DOM molecules might affect the mobility of hydrophobic organic chemicals in soils.  相似文献   

3.
Most methods to fractionate natural dissolved organic matter (DOM) rely on sorption of acidified DOM samples onto XAD‐8 or DAX‐8 resin. Procedural differences among methods are large and their interpretation is limited because there is a lack of calibration with DOM model molecules. An automated column‐based DOM fractionation method was set up for 10‐ml DOM samples, dividing DOM into hydrophilic (HPI), hydrophobic acid (HPOA) and hydrophobic neutral (HPON) fractions. Fifteen DOM model components were tested in isolation and in combination. Three reference DOM samples of the International Humic Substances Society were included to facilitate comparison with other methods. Aliphatic low‐molecular‐weight acids (LMWAs) and carbohydrates were classified as HPI DOM, but some LMWAs showed also a partial HPO character. Aromatic LMWAs and polyphenols partitioned in the HPOA fraction, menadione (quinone) and geraniol (terpenoid) in HPON DOM. Molecules with log Kow > 0.5 had negligible HPI fractions. The HPO molecules except geraniol had specific UV absorbance (SUVA, measure for aromaticity) >3 litres g−1 cm−1 while HPI molecules had SUVA values <3 litres g−1 cm−1. Distributions of DOM from eight soils ranged from 31 to 72% HPI, 25 to 46% HPOA and 2 to 28% HPON of total dissolved organic carbon. The SUVA of the HPI DOM was consistently smaller compared with the HPOA DOM. The SUVA of the natural DOM samples was not explained statistically by fractionation and the variation coefficient of SUVA among samples was not reduced by fractionation. Hence, fractionation did not reduce the variability in this DOM property, which casts some doubts on the practical role of DOM fractionation in predicting DOM properties.  相似文献   

4.
The mobility of polycyclic aromatic hydrocarbons (PAH) in soils can be influenced by the presence of dissolved organic matter. Partition coefficients of selected polycyclic aromatic hydrocarbons, ranging from 3-ring to 6-ring compounds, to water-soluble soil organic matter (WSSOM) were determined. Partition coefficients were determined for WSSOM obtained from two soils under agricultural use and forest and for commercially available humic acid (Aldrich), taking advantage of a reversed phase (C18) separation method. The WSSOM was characterised with regard to charge and hydrophilic/hydrophobic properties with a dissolved organic matter (DOM) fractionation method. No sorption to WSSOM was found for the tri- and tetracyclic PAH, whereas the penta- and hexacyclic PAH showed a significant binding to both types of WSSOM and to Aldrich humic acid. The affinity of penta- and hexacyclic PAH to WSSOM was considerably lower compared to the affinity to Aldrich humic acid. This is suggested to be due to the lower amount of hydrophobic fractions, c. 30%, in the natural WSSOM as compared to Aldrich humic acid. Effective partition coefficients (Koceff) for the sorption of PAH to bulk soil calculated from KDOC and DOM in the naturally occurring concentration range were only 60–70% of the Koc values in pure water. The impact of DOM on pollutant transport is further influenced by non-equilibrium behaviour of PAH in soils and by sorption of DOM to the solid-soil matrix. Several scenarios are described in which the effect of DOM on pollutant transport may become important.  相似文献   

5.
We have tested to see if the generic set of NICA‐Donnan model parameters, used to describe isolated humic substances, can also describe soil humic substances in situ. A potentiometric back‐titration technique was used to determine the variable surface charge of two organic peat soils at three different ionic strengths. The non‐ideal, competitive‐adsorption NICA‐Donnan model was used to simulate the surface charge, by assuming a bimodal distribution of H+ affinity on the soil solid phase. The model provided an excellent fit to the experimental data. The Donnan volume, VD, varied slightly with ionic strength, although the variation was less than for humic substances in solution. The values obtained for the parameters that define the affinity distributions, the intrinsic proton binding constant (log Kiint) and the heterogeneity of the site (mi), were similar to those observed for isolated soil humic acids. The abundance of carboxylic groups in the whole soil represented 30% of the typical value for isolated soil humic acids. The composition of the organic matter of the whole soils, obtained by 13C CPMAS NMR, was comparable to the characteristic composition of soil humic acids.  相似文献   

6.
Sorption by soil organic matter (SOM) is considered the most important process affecting the bioavailability of hydrophobic organic chemicals (HOCs)in soil.The sorption capacity of SOM for HOCs is affected by many environmental factors.In this study,we investigated the effects of soil pH and water saturation level on HOC sorption capacity of SOM using batch sorption experiments.Values of soil organic carbon-water partition coefficient (KOC) of six selected polycyclic aromatic hydrocar...  相似文献   

7.
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8.
Abstract

Humic acids (HAs) obtained from four different soils by sequential extraction with pyrophosphate solutions at different pH values (i.e. at pH 3, 5, 7, 9, 11, and 13), were examined by ultraviolet and visible (UV-VIS) spectroscopy and elemental analysis. UV-VIS spectra from 230 to 700 nm were measured, and absorbance coefficients of 1% humic acid solutions at 600 nm (E 1% 600) and Δlog K were calculated. The shape of the spectra of humic acids depended on the soil types rather than on the pH values. The (E 1% 600) values were higher in the neutral region, and lower in the alkaline region, for each pH value they decreased in the following order: buried Andosol > Andosol > Histosol ≧ Cambisol. The Δlog K values for each pH value were higher in the following order: Histosol> Cambisol > buried Andosol≧Andosol. Although the linear correlation was found to be significant between the E 1% 600 and Δlog K values, the relation between these optical properties and pH values differed among the soil types. However, in the neutral region, the higher E 1% 600 values of humic acids from buried Andosol and Andosol and the lower Δlog K values of humic acids from Cambisol and Histosol suggest that the humification degree was higher in the neutral region. Data of elemental composition and atomic ratios were obtained for each humic acid. The H/C ratios in the four soils increased gradually with increasing pH values from 5 to 13, and those for each pH value were commonly higher in the following order: Cambisol> Histosol> Andosol> buried Andosol. The O/C and OIH ratios decreased with increasing pH values. The results of the H/C versus O/C diagram suggested that decarboxylated humic acids were extracted at the higher pH values. A highly significant correlation coefficient was obtained between the H/C and OIH ratios (r= ?0.891***). Results showing that the decrease of the pH values corresponded to the order of the humic acids in the correlation curve in the H/C versus O/H diagram suggest that the humic acids with a higher content of unsaturated bonds and a higher degree of oxidation were extracted at the lower pH values within the range from 5 to 13.  相似文献   

9.

Purpose  

Polycyclic musk compounds (PMC) are used as fragrances in cosmetics and detergents and enter rivers via domestic wastewater and sewage treatment plants. Soils can be contaminated by PMC through application of sewage sludge. Accumulation of PMC occurs in sediments and biota due to their persistence and lipophilicity. Dissolved organic matter (DOM) is of special relevance for their transport and behavior in the environment as it acts as solubilizer and carrier in aquatic and terrestrial systems. With the distribution coefficient KDOC, one can predict their affinity to DOM. Different approaches exist to determine KDOC, resulting in a range of coefficients for a number of organic pollutants. The objective of this study was to determine KDOC values for PMC using solid-phase microextraction (SPME).  相似文献   

10.
The binding of metal to humic substances is problematical. The approaches for studying metal binding to organic matter are briefly reviewed. Ion-selective electrodes (Cu2+ and Pb2+) were used to measure metal complexation by a whole peat and an extracted humic acid (HA) fraction. Scatchard plots and calculation of incremental formation constants were used to obtain values for the binding constants for the metals onto both peat and HA. Both the peat and the humic acid had a larger maximum binding capacity for Pb2+ than for Cu2+ (e.g. at pH = 5 HA gave 0·188 mmol Cu2+ g?1 and 0·564 mmol Pb2+ g?1: peat gave 0·111 mmol Cu2+ g?1 and 0·391 mmol Pb2+ g?1). Overall, the humic acid had a larger metal binding capacity, suggesting that extraction caused conformational or chemical changes. The binding constants (K1) for Cu2+ increased with increasing pH in both peat and humic acid, and were larger in the peat at any given pH (e.g. at pH = 5 HA gave log K1= 2·63, and peat gave log K1= 4·47 for Cu2+). The values for Pb2+ showed little change with pH or between peat and humic acid (e.g. at pH = 5 HA gave log K1= 3·03 and peat gave log K1= 3·00 for Pb2+). In the peat, Cu2+ may be more able to bind in a 2:1 stoichiometric arrangement, resulting in greater stability but smaller binding capacity, whereas Pb2+ binds predominantly in a 1:1 arrangement, with more metal being bound less strongly. Whole peat is considered to be more appropriate than an extracted humic acid fraction for the study of heavy metal binding in organic soils, as this is the material with which metals introduced into an organic soil would interact under natural conditions.  相似文献   

11.
Wood ash fertilization increases the pH and concentration of dissolved organic carbon (DOC) in the soil solution and enhances the activity of soil microorganisms. However, it is unknown whether DOC or pH is primarily responsible for the increase in microbial activity. We designed an experiment to separate the effects of DOC and/or pH on soil microbial activity using suspensions of humus extracts and bacteria that had not previously been exposed to wood ash fertilization. After a 3-week incubation, DOC extracts were obtained from control (DOCC) and ash (DOCA) treatments with carbon concentrations of 9.1 and 32.5 mg C l−1, respectively. These extracts were supplied to bacterial suspensions at concentrations of 0 and 5 mg C l−1. We controlled for pH by matching adjustments, i.e. the original pH of the DOCC extract was 4.5 and its adjusted pH was 6.9, whereas the DOCA extract was pH 6.9 originally and pH 4.5 adjusted. The relative bacterial growth rate (RBGR), as measured by 3H-thymidine incorporation, increased in suspensions of 5 mg C l−1 DOC as compared to control suspensions of 0 mg C l−1. At pH 6.9, RBGR was higher for both DOC extracts than at pH 4.5. These results suggest that both DOC and pH influence microbial activity. As the growth rate at pH 6.9 with DOCA was higher than with DOCC, the quality of the DOC extract must also play a role since the carbon concentration was controlled for. The decrease in relative abundance of hydrophobic and hydrophilic acids in DOCA compared to DOCC indicates a quality shift. As measured by DGGE banding patterns, the bacterial community structure changed over the course of the 24-h experiment in the following three trials, all of which received 5 mg C l−1: DOCC at pH 6.9 and DOCA at pH 4.5 and 6.9. These results demonstrate that both the DOC origin (control vs. ash) and the pH influence a subset of the bacterial community.  相似文献   

12.
The soil solution chemistry of a podzolized soil in the north of Sweden was monitored for four years using percolation lysimeters. Weak organic acids were a major constituent of the soil solution and are important because of their ability to form complexes with aluminium. Dissolved organics leached from the mor layer enhance the weathering rate in the eluvial horizon by forming complexes with aluminium, especially during the autumn when the leaching of dissolved organics was greatest. The weak organic acids were titrated and their pKa values were evaluated. Aluminium was speciated with an ion-exchange method and by applying equilibrium calculations. Formation constants for the organic aluminium complexes were calculated to be log KAlong=5.42±0.32 m ?1 (n=13) in spring and summer and log KAlorg=4.87±0.14 m ?1 (n=6) in autumn. Equilibria of Al3+ with solid phases were also examined using solubility constants. Percolation lysimeters below undisturbed and cut-off mor layers were compared.  相似文献   

13.
我国几种土壤中腐殖质性质的研究   总被引：10，自引：0，他引：10       下载免费PDF全文
研究了几种土壤腐殖酸的基本性质,其中包括土壤的腐殖质组成,胡敏酸以及富里酸的元素组成,含氧官能团含量,光密度值与芳化度等,计算了E4与E4/E6比值与上述性质的相关系数。结果表明土壤腐殖质组成和性质与其形成条件有着密切的联系,并且有一定的地带规律性。水稻土中有机质含量增加,HA/FA比值变高,其活性HA显著降低,说明水稻土有利于有机质的积累并改变了腐殖质的组成。E4、E4/E6比值与元素组成,C/H比值,含氧官能团及芳化度之间的相关系数表明E4除了与C%,O%,酚羟基-O%,醌基-O%呈极显著或显著相关外,还与C/H比值及芳化度呈极显著相关,因此E4值可作为腐殖物质芳化度的一个指标。  相似文献   

14.
Abstract

Diethylaminoethyl cellulose (DEAE cellulose), a weak anion exchange resin, has been used to isolate dissolved organic matter (DOM) from soil solutions collected from three different soil types, to investigate the amount of DOM isolated from soil solutions of various origin, and the extent to which inorganic ions are isolated together with DOM. The concentration of DOM in the various soil solutions ranged from 2.5 to 32.8 mg#lbL‐1 DOC. More than 80% of dissolved organic carbon (DOC) was usually isolated with DEAE cellulose. High concentrations of aluminum (Al) and sulfate (SO4 2‐) in the soil solutions have reduced DOC recovery. More than 90% of potassium (K+), calcium (Ca2+), and magnesium (Mg2+), were removed during the isolation procedure, but 10 to 20% of Al and 30 to 40% of iron (Fe) were isolated together with the DOC, probably due to strong complexation to DOM. The advantages of using DEAE cellulose were that the use of strong acids and bases was limited and that pH adjustments of the sample, leading to chemical modification of DOM, was not required.  相似文献   

15.
The objective was to develop and adapt a versatile analytical method for the quantification of solvent extractable, saturated long‐chain fatty acids in aquatic and terrestrial environments. Fulvic (FA) and humic (HA) acids, dissolved organic matter (DOM) in water, as well as organic matter in whole soils (SOM) of different horizons were investigated. The proposed methodology comprised extraction by dichloromethane/acetone and derivatization with tetramethylammonium hydroxide (TMAH) followed by gas chromatography/mass spectrometry (GC/MS) and library searches. The C10:0 to C34:0 methyl esters of n‐alkyl fatty acids were used as external standards for calibration. The total concentrations of C14:0 to C28:0 n‐alkyl fatty acids were determined in DOM obtained by reverse‐osmosis of Suwannee river water (309.3 μg g—1), in freeze‐dried brown lake water (180.6 μg g—1), its DOM concentrate (93.0 μg g—1), humic acid (43.1 μg g—1), and fulvic acid (42.5 μg g—1). The concentrations of the methylated fatty acids (n‐C16:0 to n‐C28:0) were significantly (r2 = 0.9999) correlated with the proportions of marker signals (% total ion intensity (TII), m/z 256 to m/z 508) in the corresponding pyrolysis‐field ionization (FI) mass spectra. The concentrations of terrestrial C10:0 to C34:0 n‐alkyl fatty acids from four soil samples ranged from 0.02 μg g—1 to 11 μg g—1. The total concentrations of the extractable fatty acids were quantified from a Podzol Bh horizon (26.2 μg g—1), Phaeozem Ap unfertilized (48.1 μg g—1), Phaeozem Ap fertilized (57.7 μg g—1), and Gleysol Ap (66.7 μg g—1). Our results demonstrate that the method is well suited to investigate the role of long‐chain fatty acids in humic fractions, whole soils and their particle‐size fractions and can be serve for the differentiation of plant growth and soil management.  相似文献   

16.
Two sequential extractions with unbuffered 0.1 m BaCl2 were done to study the release of salt-exchangeable H+ and Al from mineral horizons of five Podzols and a Cambisol. Released Al was found to have a charge close to 3+ in all horizons and in both extractions. This finding was supported by the near-equality of the titrated exchangeable acidity (EAT) and the sum of exchangeable acids (EA = He + 3Ale, calculated from the pH and Al concentration of the extract). The ratio between EA of the second and the first extraction was over 0.50 in the Bs2 and C horizons and smaller in the other horizons. H+ was assumed to be in equilibrium with weak acid groups, and the modified Henderson–Hasselbach equation, pKHH = pH ? n log (α/(1 ? α)), was used to explain pH of the extract. The degree of dissociation (α) was calculated as the ratio between effective and potential cation exchange capacity. Value of the empirical constant n was found to be near unity in most horizons. When the monoprotic acid dissociation was assumed in all horizons, pKHH had the same value in both extractions. For Al3+, two equilibrium models were evaluated, describing (i) complexation reactions of Al3+ with soil organic matter, and (ii) equilibrium with Al(OH)3. Apparent equilibrium constants were written as (i) pKo = xpH ? pAl3+, and (ii) log Qgibbs= log Al3+ ? 3log H+. The two extractions gave an average reaction stoichiometry x close to 2 in all horizons. Results suggest that an equilibrium with organic Al complexes can be used to express dissolved Al3+, aluminium being apparently bound to bidentate sites. The value of log Qgibbs was below the solubility of gibbsite (log Kgibbs = 8.04) in many horizons. In addition, log Qgibbs of the second extraction was greater than that of the first extraction in all horizons except the C horizon. This indicates that equilibrium with Al(OH)3 cannot explain dissolved Al3+ in the soils. We propose that the models of pKHH and pKo can be used to simulate exchangeable H+ and Al3+ in soil acidification models.  相似文献   

17.
石林  张迪  曹艳贝  张凰 《土壤学报》2020,57(1):251-257
采用体积排阻色谱和总有机碳分析法,分别测定腐殖酸体系中加入盐酸、甲酸、乙酸和丙酸后其分子量和溶解性发生的变化;通过分析抗坏血酸、苯甲酸、苯酚和邻苯二酚4种模型化合物在甲酸影响下的紫外光谱,以验证电荷辅助氢键的存在。结果表明:小分子有机酸能够明显降低腐殖酸的分子量;此外,当腐殖酸体系pH接近小分子有机酸的pKa时(DpKa<0.5),腐殖酸溶解性明显增大。小分子有机酸可能与腐殖酸之间形成电荷辅助氢键,从而打破弱作用力维持的腐殖酸超分子的稳态结构,导致腐殖酸分子量的降低和溶解性的增加;且弱酸与有机物之间的pKa相差越小,形成的电荷辅助氢键能量越高,腐殖酸分子结构受到的扰动程度越大。一维紫外光谱和同步二维相关紫外光谱分析进一步表明,小分子有机酸可能与pKa接近的化合物之间形成电荷辅助氢键,整体跃迁所需能量提高,造成低波长吸收增大而高波长吸收减小的结果。  相似文献   

18.
Dissolved organic matter (DOM) is involved in many important biogeochemical processes in soil. As its collection is laborious, very often water‐soluble organic matter (WSOM) obtained by extracting organic or mineral soil horizons with a dilute salt solution has been used as a substitute of DOM. We extracted WSOM (measured as water‐soluble organic C, WSOC) from seven mineral horizons of three forest soils from North‐Rhine Westphalia, Germany, with demineralized H2O, 0.01 M CaCl2, and 0.5 M K2SO4. We investigated the quantitative and qualitative effects of the extractants on WSOM and compared it with DOM collected with ceramic suction cups from the same horizons. The amounts of WSOC extracted differed significantly between both the extractants and the horizons. With two exceptions, K2SO4 extracted the largest amounts of WSOC (up to 126 mg C kg–1) followed by H2O followed by CaCl2. The H2O extracts revealed by far the highest molar UV absorptivities at 254 nm (up to 5834 L mol–1 cm–1) compared to the salt solutions which is attributed to solubilization of highly aromatic compounds. The amounts of WSOC extracted did not depend on the amounts of Fe and Al oxides as well as on soil organic C and pH. Water‐soluble organic matter extracted by K2SO4 bore the largest similarity to DOM due to relatively analogue molar absorptivities. Therefore, we recommend to use this extractant when trying to obtain a substitute for DOM, but as WSOM extraction is a rate‐limited process, the suitability of extraction procedures to obtain a surrogate of DOM remains ambiguous.  相似文献   

19.
Using Sephadex G 50 gel filtration, three soil humic acids were separated into two to four fractions, which differed more or less in their spectrophotometric properties. The distribution of a humic acid fraction on an RF-Δlog K diagram was classified into two cases; in the first case, the RF increased and Δlog K decreased with the elution order, and in the second case, humic acid fractions distributed clockwise around the original humic acid.

A small amount of B type humic acid was separated by gel filtration from newly formed Rp type humic acid obtained from the mixtures of grass and soil materials incubated for four months under alternate field and air-dry conditions.  相似文献   

20.
水溶性有机物与多环芳烃结合特征的红外光谱学研究   总被引：10，自引：0，他引：10  
水溶性有机物（DOM）与多环芳烃（PAHs）之间的相互作用一直是尚未弄清的理论问题。对其正确阐释有利于更好地理解DOM对PAHs环境行为与生态效应的影响及科学地评估PAHs的环境风险，并对PAHs污染土壤的修复具有极其重要的意义。本研究以有机物料猪粪、污水污泥和带根茬水稻土作为DOM的提取材料，以菲（Phenanthrene，Phe）和芘（Pyrene，Pyr）为PAHs代表，采用红外光谱学技术研究DOM与PAHs的相互作用。红外图谱显示，供试DOM在4000—3000cm^-1、2969—2900cm^-1、1700-1375cm^-1、1300—1000cm^1和900-600cm^-1存在明显的吸收峰，这说明DOM中含有-OH或酚-OH、-NH、苯环、-C-O及-CH2等功能团。对比DOM与DOM—Phe／Pyr的图谱发现，DOM—Phe／Pyr在4000—3000cm^-1、1700—1375cm^-1和900—600cm^-1的吸收峰发生不同程度的朝长波方向飘移，表明NH-π和π-π作用参与了DOM与Phe及Pyr结合物的形成。  相似文献   

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