首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 15 毫秒
1.

Purpose  

Prometryne with moderate to low mobility in soil is a ubiquitous environmental pollutant in water and soil. Bioremediation is widely used to remove pollutants from contaminated soil. Bacterial-feeding nematodes have been tested on the decomposition of soil organic matter and the release of nutrients through their interaction with soil microorganisms, but little attention has been paid to their effects on the removal of herbicides in soil. In this study, we investigated the effects of bacterial-feeding nematodes (Cephalobus Bastian) on the dissipation of prometryne and microbial activity in prometryne contaminated soil.  相似文献   

2.

Purpose  

Land utilization of sewage sludge and sludge compost is a common practice in many countries. Soils amended with sewage sludge and sludge compost display different physicochemical properties, especially in terms of dissolved organic matter (DOM) composition that affects the electron-donating capacity (EDC) of DOM in soils. The aim of this paper was to compare the EDC of DOM derived from sewage sludge and sludge compost for enhancing Fe(III) bioreduction. It is expected that this research could be helpful for further understanding of soil remediation in the future.  相似文献   

3.

Purpose

Dissolved organic matter (DOM), a heterogeneous mixture of low concentrations of organic matter draining from soils, plays a significant role in soil C cycling and in nutrient and pollutant transport. DOM from undisturbed soil profiles has rarely been studied. Hydrophobic acids (Ho) and hydrophilic acids (Hi), the major components of DOM, were recovered, using XAD-8 and XAD-4 resins in series, from waters draining in winter and in spring periods from well-drained and poorly drained Irish grassland soil profiles in lysimeters.

Materials and methods

Waters were collected from 45 soil undisturbed lysimeters at the Teagasc Research Centre, Johnstown Castle, Wexford, Ireland. Four Irish representative soils had been collected as undisturbed 1.0-m-deep monoliths, transported to the experiment site and arranged randomly in an experimental facility. Water collections were carried out in winter and spring periods. The DOM was isolated and fractionated using an XAD-8 and XAD-4 resins in-tandem procedure, and hydrophobic acids (Ho) and hydrophilic acids (Hi) were isolated.

Results and discussion

The amounts of DOM recovered in the winter period were much greater than those in the spring period, and the soil types had only minor influences on the DOM concentrations recovered. The Ho and Hi fraction contents ranged from 62 to 90 and 10 to 28%, respectively, of the total DOM content extracted. The Hi acids were most enriched in 13C, and considered to reflect greater microbial inputs. The neutral sugar (NS) contents for the Ho and Hi fractions were in the range of 15 to 52 μg mg?1, with the Hi fraction most enriched. The amino acids (AAs) for the Ho and Hi fractions varied from 0.6 to 2.4%, and the total AAs and NS of the Ho acids were well correlated. The DOM fractions from the drainage waters contained much less AAs and NS than the corresponding fractions in the parent soils. The solid- and liquid-state NMR data indicated organic structures with low aromaticity, significant amounts of carbohydrate and with lesser amounts of peptide structures, and with long-chain methylene (CH2)n and methine (-CH-) groups.

Conclusions

The application of a variety of wet chemistry and of spectroscopy procedures has given a more in-depth awareness of the compositions of the DOM in the drainage waters from four different soils in 1.0-m-deep lysimeter arrangements. Based on wet chemistry analyses, and FTIR and liquid- and solid-state NMR spectrometry, it is clear that there are some differences between the compositions of the DOM fractions recovered. Alkyl functionalities dominated the structures. These included significant amounts or O-alkyl (predominantly carbohydrate), and with lesser (and variable amounts in the different fractions) aromatic structures (to which aromatic amino acid components were considered to be significant contributors), and with no evidence for lignin-derived structures The results suggest that, during residence in the soil solution, microbiological processes transform the SOM components released into products that are greatly different from their materials of origin in the SOM.
  相似文献   

4.

Purpose

Soil dissolved organic matter (DOM) as the labile fraction of soil organic carbon (SOC) is able to facilitate biogeochemical redox reactions effecting soil respiration and carbon sequestration. In this study, we took soil samples from 20 sites differing in land use (forest and agriculture) to investigate the electron transfer capacity of soil DOM and its potential relationship with soil respiration.

Materials and methods

DOM was extracted from 20 soil samples representing different land uses: forest (nos. 1–12) and agriculture (nos. 13–20) in Guangdong Province, China. Chronoamperometry was employed to quantify the electron transfer capacity (ETC) of the DOM, including electron acceptor capacity (EAC) and electron donor capacity (EDC), by applying fixed positive or negative potentials to a working electrode in a conventional three-electrode cell. The reversibility of electron accepting from or donating to DOM was measured by applying switchable potentials to the working electrode in the electrochemical system with the multiple-step potential technique. Carbon dioxide produced by soil respiration was measured with a gas chromatograph.

Results and discussion

Forest soil DOM samples showed higher ETC and electron reversible rate (ERR) than agricultural soil DOM samples, which may be indicative of higher humification rate and microbial activity in forest soils. The average soil respiration of forest soil (nos. 1–12) and agricultural soil (nos. 13–10) was 26.34 and 18.58 mg C g?1 SOC, respectively. Both EDC and EAC of soil DOM had close relationship with soil respiration (p?<?0.01). The results implied that soil respiration might be accelerated by the electroactive moieties contained in soil DOM, which serve as electron shuttles and facilitate electron transfer reactions in soil respiration and SOC mineralization.

Conclusions

DOM of forest soils showed higher ETC and ERR than DOM of agricultural soils. As soil represents one of the largest reservoirs of organic carbon, soil respiration affects C cycle and subsequently CO2 concentration in the atmosphere. As one of the important characteristics of soil DOM related to soil respiration, ETC has a significant impact on greenhouse gas emission and soil carbon sequestration but has not been paid attention to.  相似文献   

5.

Purpose  

Returning of rice straw into paddy field, which not only can increase the organic carbon content of soil but also can introduce dissolved organic matter (DOM) into soil, is a popular farm management strategy. However, chemical and structural heterogeneities of DOM derived from rice straw are not well characterized. The aim of this paper was to study the chemical and structural characteristics of DOM derived from rice straw at the different stages of decay.  相似文献   

6.
Dissolved organic matter (DOM) is a small but reactive pool of the soil organic matter (SOM) that contributes to soil dynamics including the intermediary pool spanning labile to resistant SOM fractions. The solubilization of SOM (DOM production) is commonly attributed to both microbially driven and physico-chemically mediated processes, yet the extent to which these processes control DOM production is highly debated. We conducted a series of experiments using 13C-ryegrass residue or its extract (13C-ryegrass-DOM) separately under sterile and non-sterile conditions to demonstrate the importance of DOM production from microbial and physico-chemical processes. Soils with similar properties but differing in parent material were used to test the influence of mineralogy on DOM production. To test the role of the source of C for DOM production, one set of soils was leached frequently with 13C-ryegrass-DOM and in the other set of soils 13C-ryegrass residue was incorporated at the beginning of the experiment into the soil and soils were leached frequently with 0.01 mol L−1 CaCl2 solution. Leaching events for both treatments occurred at 12-d intervals over a 90-day period. The amount of dissolved organic C and N (DOC and DON) leached from residue-amended soils were consistently more than 3 times higher in sterile than non-sterile soils, decreasing with the time. Despite changes in the concentration of DOC and DON and the production of CO2, the proportion of DOC derived from the 13C-ryegrass residue was largely constant during the experiment (regardless of microbial activity), with the majority (about 70%) of the DOM originating from native SOM. In 13C-residue-DOM treatments, after successive leaching events and regardless of the sterility conditions i) the native SOM consistently supplied at least 10% of the total leached DOM, and ii) the contribution of native SOM to DOM was 2–2.9 times greater in 13C-residue-DOM amended soils than control soils, suggesting the role of desorption and exchange reactions in DOM production in presence of fresh DOM input. The contribution of the native SOM to DOM resulted in higher aromaticity and humification index. Our results suggest that physico-chemical processes (e.g. exchange or dissolution reactions) can primarily control DOM production. However, microbial activity affects SOM solubilization indirectly through DOM turnover.  相似文献   

7.

Purpose

The content and composition of dissolved organic matter (DOM) in sediment directly affect nutrient cycling and material exchange in lake ecosystems. This study investigated the content and composition of DOM and its fractions in sediments, as well as the relationship between the different parameters and nitrogen (N) forms in DOM. The main aim of this study was to evaluate the compositional characteristics of DOM, hydrophobic bases (HOB), hydrophobic acids (HOA), hydrophobic neutral fractions (HON), and hydrophilic matter (HIM) in sediments from Erhai Lake, China.

Materials and methods

Seven surface sediment samples with different environmental characteristics were collected. The DOM in the sediment was fractionated into HOB, HOA, HON, and HIM using XAD-8 resin based on compound hydrophobicity. The contents of DOM and its fractions were measured using a TOC analyzer. The structural characteristics of DOM and its fractions were investigated using fluorescence spectroscopy and UV–Vis absorbance. Correlation analyses were carried out to better understand the relationships between the parameters of the spectral characteristics and the contents of the different N forms in DOM and its fractions.

Results and discussion

The content, spatial distribution and structure of DOM and its fractions in Erhai Lake sediment were affected by water depth and aquatic plants. The DOM content in sediment ranged from 0.2 to 0.5 g kg?1. HON accounted for 41.3 to 85.7 % of DOM, whereas HIM constituted 15.0 to 58.7 % and was significantly negatively correlated with HON (R 2 ?=?0.856, P?Conclusions (1) Hydrophobic fractions are the major components of DOM in the sediments from the seven sites in Erhai Lake. (2) DOM and its fractions mainly originated from microbial sources. (3) The A 253/A 203 ratio is useful for evaluating the contents of N forms. The structure of DOM and its fractions are important in affecting the contents of DON. Nitrate (NO3-N) contributes to eutrophication, and thus cannot be ignored from studies of Erhai Lake sediment.  相似文献   

8.
While dissolved organic matter (DOM) in soil solution is a small but reactive fraction of soil organic matter, its source and dynamics are unclear. A laboratory incubation experiment was set up with an agricultural topsoil amended with 13C labelled maize straw. The dissolved organic carbon (DOC) concentration in soil solution increased sharply from 25 to 186 mg C L−1 4 h after maize amendment, but rapidly decreased to 42 mg C L−1 and reached control values at and beyond 2 months. About 65% of DOM was straw derived after 4 h, decreasing to 29% after one day and only 1.3% after 240 days. A significant priming effect of the straw on the release of autochthonous DOM was found. The DOM fractionation with DAX-8 resin revealed that 98% of the straw derived DOM was hydrophilic in the initial pulse while this hydrophilic fraction was 20-30% in control samples. This was in line with the specific UV absorbance of the DOM which was significantly lower in the samples amended with maize residues than in the control samples. The δ13C of the respired CO2 matched that of DOC in the first day after amendment but exceeded it in following days. The straw derived C fractions in respired CO2 and in microbial biomass were similar between 57 and 240 days after amendment but were 3-10 fold above those in the DOM. This suggests that the solubilisation of C from the straw is in steady state with the DOM degradation or that part of the straw is directly mineralised without going into solution. This study shows that residue application releases a pulse of hydrophilic DOM that temporarily (<3 days) dominates the soil DOM pool and the degradable C. However, beyond that pulse the majority of DOM is derived from soil organic matter and its isotope signature differs from microbial biomass and respired C, casting doubt that the DOM pool in the soil solution is the major bioaccessible C pool in soil.  相似文献   

9.

Purpose

The aim of this paper has been to determine the seasonal changes in the content of dissolved organic matter (DOM) in the soils under agricultural use based on assaying changes in dissolved organic carbon (DOC) and dissolved nitrogen (DNt) as well as determining the factors which can define the DOM in soils.

Materials and methods

The research has involved the soils under agricultural use sampled in the Kujawsko-Pomorskie province (Poland). Phaeozems and Luvisols were sampled from the depth of 0–30, 30–60, and 60–100 cm, November 2011 through September 2013, in November, March, May, July, and September. The soil samples were assayed for the grain size composition, pH, dry weight content, content of total organic carbon, and total nitrogen. Dissolved organic matter was extracted with 0.004 mol dm3 CaCl2; in the DOM extracts, the content of dissolved organic carbon (DOC) and dissolved nitrogen (DNt) were assayed. The research results were statistically verified.

Results and discussion

It has been demonstrated that in the first year of research, the content of dissolved organic carbon in the soils was changing throughout the year. The highest differences in the content of that carbon fraction occurred across the soil sampled in autumn and the soil sampled in spring. In the second year of research, an inverse dependence was noted. DOC was migrating to deeper layers of the soil profile; yet, the migration got more intensive in summer. The content of dissolved nitrogen was not changing significantly throughout the year. Higher DNt content in the surface layer, in general, resulted in a higher content of dissolved nitrogen in deeper profile layer, which could have been due to leaching of the nutrient deep down the soil profile.

Conclusions

The content of dissolved organic carbon was significantly related to the content of total organic carbon and total nitrogen. Significant changes in the content of dissolved forms of nitrogen were reported in the profile of Phaeozems due to mineral fertilization and irrigation. The soils where irrigation and higher nitrogen rates had been applied demonstrated a higher content and share of soluble forms of nitrogen, as compared with the soils non-irrigated and the soils where lower nitrogen rates had been supplied.
  相似文献   

10.
The cycling of dissolved organic matter (DOM) in soils is controversial. While DOM is believed to be a C source for soil microorganisms, DOM sorption to the mineral phase is regarded as a key stabilization mechanism of soil organic matter (SOM). In this study, we added 14C-labelled DOM derived from Leucanthemopsis alpina to undisturbed soil columns of a chronosequence ranging from initial unweathered soils of a glacier forefield to alpine soils with thick organic layers. We traced the 14C label in mineralized and leached DOM and quantified the spatial distribution of DO14C retained in soils using a new autoradiographic technique. Leaching of DO14C through the 10 cm-long soil columns amounted up to 28% of the added DO14C in the initial soils, but to less than 5% in the developed soils. Biodegradation hardly contributed to the removal of litter-DO14C as only 2–9% were mineralized, with the highest rates in mature soils. In line with the mass balance of 14C fluxes, measured 14C activities in soils indicated that the major part of litter DO14C was retained in soils (>80% on average). Autoradiographic images showed an effective retention of almost all DO14C in the upper 3 cm of the soil columns. In the deeper soil, the 14C label was concentrated along soil pores and textural discontinuities with similarly high 14C activities than in the uppermost soil. These findings indicate DOM transport via preferential flow, although this was quantitatively less important than DOM retention in soils. The leaching of DO14C correlated negatively with oxalate-extractable Al, Fe, and Mn. In conjunction with the rapidity of DO14C immobilization, this strongly suggests that sorptive retention DOM was the dominating pathway of litter-derived DOM in topsoils, thereby contributing to SOM stabilization.  相似文献   

11.
Dissolved organic matter (DOM) in soil solution represents a complex mixture of organic molecules and plays a central role in carbon and nitrogen cycling in plant–microbial–soil systems. We tested whether excitation–emission matrix (EEM) fluorescence spectroscopy can be used to characterize DOM and support previous findings that the majority of DOM is of high molecular weight (MW). EEM fluorescence spectroscopy was used in conjunction with MW fractionation to characterize DOM in soil solution from a grassland soil land management gradient in North Wales, UK. Data analysis suggested that three distinct fluorescence components could be separated and identified from the EEM data. These components were identified as being of humic‐like or fulvic‐like origin. Contrary to expectations, the majority of the fluorescence signal occurred in the small MW (<1 kDa) fraction, although differences between soils from the differently managed grasslands were more apparent in larger MW fractions. We conclude that following further characterization of the chemical composition of the fluorophores, EEM has potential as a sensitive technique for characterizing the small MW phenolic fraction of DOM in soils.  相似文献   

12.

Purpose  

The dynamics and availability of potassium (K) in soils depend on many factors, including the mineralogy of fractions and the soil geochemical conditions. The objective of this work is to quantify K in distinct lowland soil compartments in the south of Brazil, relating them to particle size fractions and mineralogical constitution.  相似文献   

13.

Purpose  

We investigated the chemical fractions of Zn, Cd and Cu in soils collected from positions at different distances from a copper smelter and studied the relationships between distribution patterns of Zn, Cd and Cu, fractions and soil organic carbon (SOC), especially “black carbon” (BC), in contaminated soils. The relationships between soil particle size and concentrations of Zn and Cd in contaminated soil were also examined.  相似文献   

14.

Purpose

Dissolved organic matter (DOM) has been shown to be an efficient electron transfer facilitator in biogeochemical reactions due to its ability to mediate redox reactions. It has been known that various fractions of DOM differed in their chemical and biogeochemical behaviors in environment. However, there has been relatively little work directed at predicting the dependence of redox properties of DOM on its fractions.

Materials and methods

DOM was extracted from sewage sludge compost. Freeze-dried DOM was grouped into three fractions of different molecular sizes (<3,500, 3,500–14,000, and >14,000 Da) using dialysis bags (Spectra/Por 3 and 4, Spectrum Industries, California, US). Cycle voltammetry was used to investigate the redox behavior of the fractions. Chronoamperometry was employed to study their electron accepting capacities and electron donating capacities by applying fixed positive or negative potential to the working electrode in a conventional three-electrode cell. Fourier-transform infrared and three-dimensional excitation/emission matrix fluorescence spectroscopies were used to determine the functional groups in the fractions. Shewanella putrefaciens 200 (SP200) and Klebsiella pneumoniae L17 (L17) were used for all microbial iron(III) reduction experiments.

Results and discussion

Electrochemical methods show that the electron transfer capacity (ETC) of DOM depends on its molecular weight, and ETC is in the order of high-molecular weight DOM (H-DOM) > moderate-molecular weight DOM > low-molecular weight DOM. The same trend is discovered in the DOM-stimulated iron(III) oxide bioreduction where DOM fractions act as electron shuttles transferring electrons from the Fe(III)-reducing bacteria to the iron oxide. Both spectroscopic and cyclic voltammogram assays show the highest abundance of redox moieties associated to H-DOM, which is possibly responsible for its strongest electron-shuttling ability.

Conclusions

DOM has a wide molecular weight (MW) distribution due to the complexity of its chemical composition and structure. In addition to structural variations, DOM fractions with different MW have different redox properties and electron-shuttling capacities in microbial Fe(III) reduction. The results are of great significance for further studies on DOM geochemical behavior in environment.  相似文献   

15.
The response of a fresh, agricultural soil when contaminated with pentachlorophenol (PCP) and supplemented with compost (C) or dissolved organic matter (DOM) was studied in the laboratory. The concentration of PCP and the changes in various functionally related properties (i.e. microbial biomass, basal respiration, soil hydrolase and oxidoreductase activity) were measured over 150 d. Variations in the main physical and chemical properties of the soils were also monitored. Two different doses of compost (C1 = 0.27% and C2 = 0.83%, corresponding to 10 and 30 t ha−1, respectively) or DOM (D1 = 0.07% and D2 = 0.2%) equivalent to the carbon content of the two compost doses C1 and C2 were used and the following five systems were investigated: soil (S), soil–compost (S-C1 and S-C2) and soil–DOM (S-D1 and S-D2). PCP concentrations declined progressively and significantly with time. This effect was most pronounced for the soils amended with the lower compost dose C1 (S-C1) and with the two DOM (S-D1 and S-D2) amounts. Significantly reduced amounts of PCP were extracted after its 500-d residence in the various systems. Higher amounts of the residual PCP were extracted from the humic acids (HA), fulvic acids (FA) and humin–mineral (HU) fractions of the 500 d aged samples than from the same unfractionated samples, indicating that the residual PCP preferentially accumulated in the organic fractions of soil. The soil showed an endogenous microbial activity as indicated by basal respiration, microbial biomass and all the enzymatic activities tested (dehydrogenase, glucosidase, phosphatase, arylsulphatase and urease). Addition of the PCP severely depressed some of the tested biochemical properties suggesting an inhibitory effect on microbial activity. Conversely, higher basal respiration, and similar β-glucosidase and phosphatase activities were measured in comparison with the controls. No significant effects were observed following the addition of two doses of the compost or the DOM. Fungal colonies belonging to the taxonomic group of Ascomycetes and identified as Byssochlamys fulva developed with time in all the PCP-contaminated samples. Growth of B. fulva in vitro in the presence of PCP showed that the isolate was tolerant to 12.5 and 25 mg l−1 PCP and degraded 20% of its initial concentration in 8 d. Overall, the results indicate that many complex processes occurred in the contaminated soil and combinations of these determined the response to PCP contamination. The sorption of PCP to the soil matrix (which increased with time) and its degradation/transformation by indigenous soil microbial activity were likely involved. Both the processes appeared to be favoured by the presence of dissolved organic matter.  相似文献   

16.
Dissolved organic matter(DOM) in soil plays an important role in the fate and transport of contaminants.It is typically composed of many compounds,but the effect of different extraction factors on the abundance of different DOM components is unknown.In this study,DOM was extracted from three soils(paddy field,vegetable field and forest soils) with various extraction time,liquid to solid ratios(LSRs),extractant types,and extractant concentrations.The LSR had a significant effect on DOM content,which increased by 0.5–4.0 times among the three soils when LSR increased from 2:1 to 10:1(P 0.05).Dissolved organic matter content increased by 4%–53% when extraction time increased from 10 to 300 min(P 0.05).Extractant concentration had different effects on DOM content depending on the extractant.Higher concentrations of KCl promoted DOM extraction,while higher concentrations of KH_2PO_4 inhibited DOM extraction.Therefore,grey relational analysis was used to further quantitatively evaluate the effect of extraction time,LSR,and extractant concentration on DOM,using KCl as an extractant.For the paddy field and forest soils,the impact of these three factors on DOM extraction efficiency was in the following order:KCl concentration LSR extraction time.However,the effect was different for the vegetable field soil:LSR extraction time KCl concentration.Taking all these factors into account,1.50 mol L~(-1) KCl and an LSR of 10:1 with a shaking time of 300 min was recommended as the most appropriate method for soil DOM extraction.  相似文献   

17.
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   

18.
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   

19.
Sterilized soil is often used, for example in degradation studies, sorption experiments, microbiological tests and plant test systems, to distinguish between microbial processes and abiotic reactions. The most commonly used technique for sterilization is autoclaving of the soil. Another technique is irradiation with high‐level gamma radiation (γ‐radiation). One major drawback of sterilization procedures is the possible alteration of the structure of soil components, for example the organic matter. A change in the chemical structure of the soil organic matter can cause different reactions in the above‐mentioned experiments and hence interfere with the aim of clearly distinguishing between biotic and abiotic processes. Two soils (Gleyic Cambisol and Orthic Luvisol) were sterilized by two γ‐irradiation procedures (4 kGy hour?1 for 9 hours and 1.3 kGy hour?1 for 27 hours) and repeated autoclaving at 121°C. Gentle physical aggregate fractionation of the sterilized soils revealed a decrease in the aggregation of the soil, which was reflected in an increase of the clay fraction. Subsequent analysis of the aqueous phase revealed much more dissolved organic matter (DOM) in the γ‐sterilized and autoclaved soils than in the untreated soils. Ultraviolet (UV) and fluorescence spectra of the DOM showed a decrease in the aromaticity and polycondensation of the dissolved organic carbon (DOC). 13C cross‐polarization/magic‐angle spinning nuclear magnetic resonance (13C‐CP/MAS NMR) spectra of the unfractionated soils and their respective soil fractions before and after sterilization showed that the most important change occurred in the carbohydrate and N‐alkyl region, the main components of microorganisms. In general, the impact of the sterilization method was stronger for autoclaving. The γ‐sterilized soils and fractions displayed both fewer and smaller changes in the soil organic matter.  相似文献   

20.

Purpose  

Chemometric methods were used to analyze chemical/spectroscopic data of fulvic acid (FA) isolated from soils in Hetao Irrigation District of China and to indicate humification degree of soil organic matter and assess soil salinization processes.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号