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51.
SOM fractionation methods: Relevance to functional pools and to stabilization mechanisms 总被引:2,自引:0,他引:2
Margit von Lützow Ingrid Kögel-Knabner Heinz Flessa Egbert Matzner 《Soil biology & biochemistry》2007,39(9):2183-2207
Soil organic matter (SOM) consists of various functional pools that are stabilized by specific mechanisms and have certain turnover rates. For the development of mechanistic models that predict changes in SOM storage, these pools have to be quantified and characterized. In the past, numerous fractionation schemes have been developed to separate and analyse such SOM fractions. In this review, the SOM fractions obtained with such operational fractionation procedures are described in terms of their pool sizes, chemical properties, and turnover rates. The main objective of this review is to evaluate these operationally defined fractions with respect to their suitability to describe functional SOM pools that could be used to parameterize SOM turnover models. Fractionation procedures include (1) physical separation of SOM into aggregate, particle size, and density fractions and fractions according to their magnetic susceptibility, and (2) various wet chemical procedures that fractionate SOM according to solubility, hydrolysability, and resistance to oxidation or by destruction of the mineral phase. Furthermore, combinations of fractionation methods are evaluated.The active SOM pool with turnover rates <10 years may best be represented by the soil microbial biomass and the light fraction (<1.6-2 g cm−3) obtained by density fractionation (if black carbon contents are considered). Most chemical and physical fractionations as well as combinations of methods yield SOM fractions that are not homogeneous in terms of turnover rates. It has proven to be particularly difficult to isolate functional fractions that represent the passive model pools in which the majority of soil SOM is stabilized. The available fractionation methods do not correspond to specific stabilization mechanisms and hence do not describe functional SOM pools. Another problem is that comprehensive data for turnover rates and data for whole soil profiles are only now becoming available, especially for new fractionation methods. Such information as well as the use of specific markers and compound-specific isotope analysis may be important for future differentiation and evaluation of functional SOM fractions. 相似文献
52.
Surface water quality of factory-based and vegetable-based peri-urban areas in the Yangtze River Delta region,China 总被引:1,自引:0,他引:1
QingLi Zhang XueZheng Shi Biao Huang DongSheng Yu I. Öborn K. Blombäck HongJie Wang T.F. Pagella F.L. Sinclair 《CATENA》2007
Detailed surveys of surface water in two contrasting peri-urban areas in the Yangtze River Delta region of China were conducted to determine the distribution of heavy metals, nitrogen (N) and phosphorus (P) as well as the speciation of N and P. A factory-based (FB) area was compared with a vegetable-based (VB) area during the dry season. The concentrations of heavy metals in the surface water in the FB area were higher than those in the VB area, suggesting modest contamination of surface water with Zn, Cu, Cr and Pb but not Cd, from discharge of factory effluent in the FB area but not the VB area. Although total N (TN) and total P (TP) levels in the surface water were high in both areas, the surface water in the VB area had significantly higher levels of nitrate N (NO3–N), organic N (ON) and TN than those in the FB area. In both areas, the levels of water-soluble P (WP), organic P (OP) and TP were high in the river water that received municipal wastewater. The distribution of N and P species throughout the surface water system indicated that the NO3–N and ON mainly came from vegetable fields, while ammonium N (NH4–N), WP and OP were mainly from municipal wastewater. Treatment of municipal wastewater prior to discharge to reduce N and P by purification is recommended together with research and extension to develop more efficient use of N and P fertilizer by vegetable farmers. 相似文献
53.
Ingrid K Thomsen Per SchjønningJørgen E Olesen Bent T Christensen 《Soil biology & biochemistry》2003,35(6):765-774
The turnover of native and applied C and N in undisturbed soil samples of different texture but similar mineralogical composition, origin and cropping history was evaluated at −10 kPa water potential. Cores of structurally intact soil with 108, 224 and 337 g clay kg−1 were horizontially sliced and 15N-labelled sheep faeces was placed between the two halves of the intact core. The cores together with unamended treatments were incubated in the dark at 20 °C and the evolution of CO2-C determined continuously for 177 d. Inorganic and microbial biomass N and 15N were determined periodically. Net nitrification was less in soil amended with faeces compared with unamended soil. When adjusted for the NO3-N present in soil before faeces was applied, net nitrification became negative indicating that NO3-N had been immobilized or denitrified. The soil most rich in clay nitrified least N and 15N. The amounts of N retained in the microbial biomass in unamended soils increased with clay content. A maximum of 13% of the faeces 15N was recovered in the microbial biomass in the amended soils. CO2-C evolution increased with clay content in amended and unamended soils. CO2-C evolution from the most sandy soil was reduced due to a low content of potentially mineralizable native soil C whereas the rate constant of C mineralization rate peaked in this soil. When the pool of potentially mineralizable native soil C was assumed proportional to volumetric water content, the three soils contained similar proportions of potentially mineralizable native soil C but the rate constant of C mineralization remained highest in the soil with least clay. Thus although a similar availability of water in the three soils was ensured by their identical matric potential, the actual volume of water seemed to determine the proportion of total C that was potentially mineralizable. The proportion of mineralizable C in the faeces was similar in the three soils (70% of total C), again with a higher rate constant of C mineralization in the soil with least clay. It is hypothesized that the pool of potentially mineralizable C and C rate constants fluctuate with the soil water content. 相似文献
54.
Ingrid M. van AarleBengt Söderström Pål Axel Olsson 《Soil biology & biochemistry》2003,35(12):1557-1564
Arbuscular mycorrhizal (AM) development in different soil types, and the influence of AM fungal hyphae on their original soil were investigated. Plantago lanceolata, which can grow in soils of a very wide pH range, was grown in two closely related limestone soils and an acid soil from rock habitats. Plants were colonised by the indigenous AM fungal community. The use of compartmented systems allowed us to compare soil with and without mycorrhizal hyphae. Root colonisation of P. lanceolata was markedly higher in the limestone soils (30-60%) than in the acid soil (5-20%), both in the original habitat and in the experimental study. Growth of extraradical AM fungal hyphae was detected in the limestone soils, but not in the acid soil, using the signature fatty acid 16:1ω5 as biomass indicator. Analysis of signature fatty acids demonstrated an increased microbial biomass in the presence of AM fungal hyphae as judged for example from an increased amount of NLFA 16:0 with 30 nmol g−1 in one of the limestone soils. Bacterial activity, but not soil phosphatase activity, was increased by around 25% in the presence of mycorrhizal hyphae in the first harvest of limestone soils. AM fungal hyphae can thus stimulate microorganisms. However, no effect of AM hyphae was observed on the soil pH or organic matter content in the limestone soils and the available P was not depleted. 相似文献
55.
Background, Aims and Scope Contaminated land is a high priority environmental problem in most of Europe and North-America. Sweden is no exception and
generic guideline values have been developed for the initial assessment, but site-specific assessments are also needed. The
generic guideline values are not applicable when the exposure conditions are different from the typical Swedish conditions
or when the site contains a particularly sensitive ecosystem. The Swedish guideline values have, like in many other countries,
been set by using deterministic point estimates for all variables and constants in the used multimedia model. The same approach
is common also for site-specific assessments, and a limitation is that it fails to quantify variability and uncertainty. Probabilistic
risk assessment provided a method to deal with this problem. Variability and uncertainty in the input parameters (variables
or constants) are described by probability distributions, and likewise the output (risk or exposure) is presented as a probability
distribution. A substantial number of probabilistic risk assessments for contaminated land at sites in North America, Europe
and Asia have been published. However, an extensive review of the literature did not identify any study where probabilistic
risk assessment was applied to a site contaminated by an iron or steel industry. Here we will describe such a case, where
we have compared a deterministic point estimate with a probabilistic risk assessment for six elements and benzo[a]pyrene.
Methods The site had different metallurgical plants in operation for more than 100 years. Most parts of the steel mill were closed
by the mid 1980s, and today the site is used by small-sized enterprises. The soil is contaminated with metals from the previous
industrial operations. The present owner plans to develop the site and has therefore initiated extensive investigations of
soil contamination. Sixty-two soil samples collected between 1997 and 2000 provided a good coverage of the whole site, and
were analyzed for the content of different elements and polycyclic aromatic hydrocarbons (PAH). The exposure assessments were
focused on six elements with high concentrations compared to the generic guideline values; arsenic (As), lead (Pb), cadmium
(Cd), chromium (Cr), copper (Cu) and zinc (Zn). In addition, benzo[a]pyrene was included due to the high toxicity and comparatively
high concentrations. Variability and uncertainty were characterized in a Monte Carlo simulation of exposures (10 000 iterations),
and the exposures were evaluated with two land use scenarios; less sensitive use and sensitive use.
Results and Discussion The deterministic point estimates and the probabilistic estimates of the 95th percentile are in approximately the same ranges
in the scenario of less sensitive land use. It is only the exposure for arsenic that is slightly above the toxicological reference
value (TRV) in the deterministic assessment. In the probabilistic assessment, the exposure for all elements is below the TRV.
The results for sensitive land use are applicable to a scenario where the site is developed for general housing. The deterministic
point estimates and the probabilistic estimates of the 95th percentile are also here in approximately the same ranges, but
the exposure exceeds the TRV for arsenic, cadmium and lead. Drinking water, vegetables grown on site and soil ingestion are
the major exposure pathways for this scenario. In this assessment, the estimated intake distributions are applicable to a
randomly selected individual. The probability distributions used here to characterize the different soil parameters are typically
representing both variability and uncertainty, and the same is true the majority of the exposure variables. We therefore decided
not to attempt to separate variability and uncertainty at this stage, but with additional data from a more in-depth site investigation
it might be possible to achieve this.
Conclusions and Outlook To the best of our knowledge, this study is the first report on a probabilistic risk assessment on a former iron and steel
works site. The materials handled by this industry were less toxic than for many other metallurgical operations, but contaminants
may still severely limit the options for future land use. This case study shows that probabilistic exposure estimates for
a set of soil contaminants can be quite similar to deterministic point estimates. The main difference is instead to be found
in the additional information obtained with the probabilistic assessment. The sensitivity analyses show pathways and input
variables that contribute most to variations in the total intake of each contaminant, e.g. dermal contact and ingestion of
soil, vegetables and drinking water. This information can be used both in the planning of future land use and for active measures
to reduce current exposure. The probabilistic assessment also provides information on the magnitude of exposure and the margin
of safety. This information may facilitate risk communication between decision-makers and stakeholders. The presentation of
results from probabilistic risk assessments is only briefly discussed in the literature and here we see a need for research
and opportunities for enhancement. The choice of data analytical tools may then be of importance, since more complex multimedia
models are rather difficult to decipher when implemented within traditional spreadsheet software. Some of the research needs
are identified here and in a previous review article in this journal. 相似文献
56.
Instrumental measurement of redness loss (decrease in a* value) was evaluated as a tool to follow hemoglobin (Hb)-mediated lipid oxidation in fish muscle. Two washed cod mince model systems were used (prepared at pH 6.5 and 5.5), both fortified with 15 micromol/kg of trout Hb and adjusted to pH 6.5 and 81% moisture. The rate of oxidation was varied through pH alterations (pH 6.1 and 6.9) and addition of an antioxidative cod muscle press juice. During ice storage, TBARS, painty odor, and a* values were followed. In all "oxidizing" samples, a* values correlated well with TBARS and painty odor development; r = -0.95 and -0.77, respectively. In press juice containing samples, the correlation was lower (0.55 for a vs TBARS) because there was a slight a* value decrease even in the absence of measurable lipid oxidation. a* values distinguished between "oxidizing" and stable samples within 1 day, before any lipid oxidation products could be chemically detected. It was confirmed in an aqueous phosphate buffer model system that the redness loss corresponded to a buildup of brownish met-Hb at the expense of oxy- and deoxy-Hb. The a* value data were best used as a lipid oxidation index by calculating the rate of decrease (k value) in the "initial phase" of the redness loss (before accumulation of lipid oxidation products) or in the "differentiation phase" (during the exponential raise in TBARS/painty odor). Calibration to lipid oxidation products must, however, be made for each specific sample type. Washing method, pH, Hb-type, etc., all affected both k values and absolute a* readings. Small yellowness (b*) increases also occurred along with a value losses, possibly the result of polymerized Schiff bases. 相似文献
57.
Various methods exist for the isolation of particulate organic matter (POM), one of the soil‐organic‐matter (SOM) fractions reacting most sensitive on land‐use or soil‐management changes. A combination of density separation and ultrasonic treatment allows to isolate two types of POM: (1) free POM and (2) POM occluded in soil aggregates. POM fractions are closely linked to their biochemical function for the formation and stabilization of aggregates, therefore methods using different aggregate sizes may result in different POM fractions isolated. We evaluated two physical fractionation procedures to reveal whether they yield different POM fractions with respect to amount and composition, using grassland and arable soils with sandy‐loam to sandy–clay‐loam texture and thus low macroaggregate stability. Method I used air‐dried aggregates of <2.0 mm size and a low‐energy sonication for aggregate disruption, method II used field‐moist aggregates <6.3 mm and a high‐energy–sonication procedure for aggregate disruption. POM fractions were analyzed by elemental analysis (C, N) and CPMAS 13C‐NMR spectroscopy. With both methods, about similar proportions of the SOM are isolated as free or occluded POM, respectively. The free‐ and occluded‐POM fractions obtained with method I are also rather similar in C and N concentration and composition as shown by 13C‐NMR spectroscopy. Method II isolates a free‐ and occluded‐POM fraction with significantly different C and N concentrations. NMR spectra revealed significant differences in the chemical composition of both fractions from method II, with the occluded POM having lower amounts of O‐alkyl C and higher amounts of aryl C and alkyl C than the free POM. Due to the use of larger, field‐moist aggregates with minimized sample pretreatment, two distinctly different POM fractions are isolated with method II, likely to be more closely linked to their biochemical function for the formation and stabilization of aggregates. High‐energy sonication as in method II also disrupts small microaggregates <63 µm and releases fine intraaggregate POM. This fraction seems to be a significant component of occluded POM, that allows a differentiation between free and occluded POM in sandy soils with significant microaggregation. It can be concluded, that microaggregation in arable soils with sandy texture is responsible for the storage of a more degraded occluded POM, that conversely supports the stabilization of fine microaggregates. 相似文献
58.
Analysis of Genetic Relationships among Turkish Cultivars and Breeding Lines of Lens culinatis Mestile Using RAPD Markers 总被引:1,自引:0,他引:1
Ertuğrul Yüzbaşıoğlu Sebahattin Özcan Leyla Açık 《Genetic Resources and Crop Evolution》2006,53(3):507-514
Randomly Amplified Polymorphic DNA markers were used to determine the genetic relationships among Turkish lentil cultivars
and breeding lines. Fourteen cultivars and thirteen breeding lines were evaluated to determine genetic variability using nine
random 10-mer primers (among 45 primers). Forty-one reproducible bands were obtained, 54% of which were polymorphic. Genetic
distances among cultivars and breeding lines were obtained from the simple matching coefficients (SM). The lowest genetic
distance was observed between the cultivars of Ali Dayi and Kafkas with 5.0%, while ‘Seyran-96’ and ‘Ozbek’ had the highest
genetic distance with 58.3%. An unweighted pair-group method with arithmetic averages (UPGMA) cluster analysis was performed
on the distance matrix using Phylip software. The dendrogram clearly showed two distinct groups. The first group is composed
of Akm 565 and Akm 563. The second group contains all the cultivars and remaining eleven breeding lines. 相似文献
59.
Soil pH is one of the main factors influencing the solubility and availability of trace elements in arable soils. Thus pH can affect the trace element contents of agricultural crops and thereby indirectly influence human health. The aim of this study was to determine Cd, Ni, Zn, Cu, Mn, Cr, Al and Se contents in spring wheat, potatoes and carrots (Cd, Ni and Zn) and estimate their correlations with certain soil factors (surface and subsurface soil pH and organic matter content) governing the plant availability of these elements. Commercial fields were sampled in Sweden in order to cover a wide range of soil types with respect to pH, soil texture and organic matter content. Concentrations of Zn, Mn, Ni (grain) and Cd (straw) in spring wheat (n=43); Cd, Ni, Zn, Mn, Cu and Al in potatoes (n=69); and Cd, Ni and Zn in carrots (n=36) showed significant negative correlations with surface soil pH (0–25 cm). The Se content of potatoes and Cr content of spring wheat straw were positively correlated with soil pH. Stepwise multiple regressions including a combination of soil pHs (0–25 and 25–50 cm) and organic matter contents (0–25 cm) showed that the organic matter content as well as the surface and subsurface soil pH significantly influenced concentrations of several trace elements in one or more of the studied crops. It was concluded that, if acid deposition together with other acidifying processes (fertilisation, harvest of biomass, etc.) are not balanced by a sufficient amount of liming there might be a decrease in the pH of arable soils, which, in turn will lead to decreased levels of Se in edible crops but an overall increase concentrations of other trace elements. 相似文献
60.
Araújo CL Bezerra IW Oliveira AS Moura FT Macedo LL Gomes CE Barbosa AE Macedo FP Souza TM Franco OL Bloch-J C Sales MP 《Journal of agricultural and food chemistry》2005,53(11):4381-4387
A proteinaceous inhibitor with high activity against trypsin-like serine proteinases was purified from seeds of the tamarind tree (Tamarindus indica) by gel filtration on Shephacryl S-200 followed by a reverse-phase HPLC Vidac C18 TP. The inhibitor, called the tamarind trypsin inhibitor (TTI), showed a Mr of 21.42 kDa by mass spectrometry analysis. TTI was a noncompetitive inhibitor with a Ki value of 1.7 x 10(-9) M. In vitro bioinsecticidal activity against insect digestive enzymes from different orders showed that TTI had remarkable activity against enzymes from coleopteran, Anthonomus grandis (29.6%), Zabrotes subfasciatus (51.6%), Callosobruchus maculatus (86.7%), Rhyzopertha dominica(88.2%), and lepidopteron, Plodia interpuncptella (26.7%), Alabama argillacea (53.8%), and Spodoptera frugiperda (75.5%). Also, digestive enzymes from Diptera, Ceratitis capitata (fruit fly), were inhibited (52.9%). In vivo bioinsecticidal assays toward C. capitata and C. maculatus larvae were developed. The concentration of TTI (w/w) in the artificial seed necessary to cause 50% mortality (LD50) of larvae was 3.6%, and that to reduce mass larvae by 50.0% (ED50) was 3.2%. Furthermore, the mass C. capitata larvae were affected at 53.2% and produced approximately 34% mortality at a level of 4.0% (w/w) of TTI incorporated in artificial diets. 相似文献