Fulvic Acid Carbon Research Articles

Elevational gradient affect functional fractions of soil organic carbon and aggregates stability in a Tibetan alpine meadow

The alpine meadow in the Tibetan plateau is predicted to be sensitive to climate change. Understanding soil organic carbon (SOC) characteristics and soil aggregate stability is essential for scientifically evaluating their effect as a carbon (C) sink or source under a climate change scenario. In this study, the spatial variations of the concentrations of SOC and its fractions, the chemical composition of SOC, and the water stability of aggregates and their relationships with climatic, vegetational and edaphic factors were investigated along an elevational gradient of an alpine meadow (4400–5200m above sea level) on the Tibetan Plateau. The results showed that with increasing elevation, the concentrations of SOC, water-soluble organic carbon (WSOC), easily oxidizable organic carbon (EOC), humic acid carbon (HAC), fulvic acid carbon (FAC), humin carbon (HUC), and macroaggregate- and microaggregate-associated carbon increased gradually, reached a peak at 4800 or 4950m, and subsequently decreased. Similarly, the proportion of alkyl C, the ratios of alkyl C/O-alkyl C, aliphatic C/aromatic C and hydrophobic C/hydrophilic C, and the mean weight diameter (MWD) of water-stable aggregates were higher at 4950m than at other elevations. SOC, WSOC, EOC, HAC, FAC, HUC, macroaggregate- and microaggregate-associated carbon, alkyl C, and MWD were positively correlated with each other and with aboveground biomass (AGB) and free/amorphous Fe- or Al-oxides. The above results indicated that SOC and aggregate stability presented an unimodal pattern along the elevational gradient. The observed unimodal distribution of AGB associated with an optimal combination of temperature and precipitation was responsible for the distribution of SOC and aggregate stability. The physical protection in microaggregates, chemical interactions with Fe- or Al-oxide minerals, and biochemical protection by recalcitrant alkyl C may be the primary mechanisms for SOC preservation in alpine meadows. Our results suggest that climate change in the future can impact SOC and structural stability by regulating the distribution of AGB on this vertical transect. Given the low SOC and structural stability at lower elevations, we recommend that these sites be specifically protected from anthropogenic disturbance to sustain high grassland ecosystems and address future climate change in this region.

Humic substances and its distribution in coffee crop under cover crops and weed control methods

Humic substances (HS) comprise the passive element in soil organic matter (SOM), and represent one of the soil carbon pools which may be altered by different cover crops and weed control methods. This study aimed to assess HS distribution and characteristics in an experimental coffee crop area subjected to cover crops and cultural, mechanical, and chemical weed control. The study was carried out at Londrina, in the state of Parana, southern Brazil (23°21’30” S; 51°10’17” W). In 2008, seven weed control/cover crops were established in a randomized block design between two coffee rows as the main-plot factor per plot and soil sampling depths (0-10 cm, 10-20 cm, 20-30 cm and 30-40 cm) as a split-plot. HS were extracted through alkaline and acid solutions and analyzed by chromic acid wet oxidation and UV-Vis spectroscopy. Chemical attributes presented variations in the topsoil between the field conditions analyzed. Cover crop cutting and coffee tree pruning residues left on the soil surface may have interfered in nutrient cycling and the humification process. Data showed that humic substances comprised about 50 % of SOM. Although different cover crops and weed control methods did not alter humic and fulvic acid carbon content, a possible incidence of condensed aromatic structures at depth increments in fulvic acids was observed, leading to an average decrease of 53 % in the E4/E6 ratio. Humin carbon content increased 25 % in the topsoil, particularly under crop weed-control methods, probably due to high incorporation of recalcitrant structures from coffee tree pruning residues and cover crops.

Carbon fractionation in a mine soil amended with compost and biochar and vegetated with Brassica juncea L

The aim of this study was to evaluate the effect of the application of compost and biochar as soil amendments and planting of Brassica juncea L. to improve soil carbon fractions in a copper mine soil. A greenhouse experiment was carried out for 3months amending the mine soil with increasing proportions of compost and biochar mixture (20, 40, 80 and 100%) and planting Brassica juncea L. The results showed that the addition of amendments increased soil pH from 2.7 to 8.66, TC from undetectable levels to 149gkg−1, SOC from undetectable levels to 128gkg−1 and TN from undetectable levels to 11.13gkg−1. Organic amending also increased DOC (dissolved organic carbon) from undetectable levels to 25.56gkg−1, FOM (carbon in the free organic matter) from undetectable levels to 38.04gkg−1, FAP (carbon in fulvic acids removed with phosphoric acid) from undetectable levels to 15.57gkg−1, as well as increased the humification ratio, the humification index, the polymerisation rate and the organic carbon in the humified fractions (humic acids, fulvic acids and humin). Soils amended and vegetated with Brassica juncea showed lower values for FOM and FAP and higher values for humification ratio and polymerisation rate than the amended not-vegetated soils. Therefore, the combination of compost and biochar as soil amendment can be considered an efficient treatment to improve soil carbon fractions, making it suitable for a field scale application.

Temporal responses of soil biological characteristics to organic inputs and mineral fertilizers under wheat cultivation in inceptisol

ABSTRACTA 2-year field experiment was conducted in wheat ecosystem to assess the key soil biological characteristics in inceptisols of northeastern region of India. Nine treatments using organic inputs (farmyard manure and vermicompost) and mineral fertilizers were applied by modulating the doses of organics and mineral N fertilizer. Soil enzymes (urease, phosphatase, dehydrogenase, fluorescein diacetate (FDA) and arylsulphatase), microbial biomass carbon (MBC), bacteria and fungi populations were measured before seed sowing (GS1), at flowering stage (GS2) and after harvest (GS3) of wheat, whereas total organic carbon (TOC) was studied at GS3. GS2 recorded significantly higher soil enzyme activities, except FDA, which increased considerably at GS3. Enzyme activities, available N and TOC significantly (p ≤ 0.05) enhanced with application of organic inputs even with reduced (50%) mineral N. Except urease and phosphatase, other enzymes did not respond significantly to mineral fertilization. Vermicompost application increased mean enzyme activities, MBC, microbial growth and TOC fractions (particulate organic carbon, humic acid and fulvic acid carbon) than farmyard manure. Significant (p ≤ 0.05) positive correlations (r = 0.61–0.87) were obtained between TOC and its fractions with studied soil enzymes. Thus, in conclusion, 5 t ha–1 organics incorporation (especially vermicompost) in wheat fertility programme can uphold soil biological health, reduce (50%) N application and would be a sustainable option for wheat grown in inceptisols of northeastern region of India.

ROLE OF APORRECTODEA CALIGINOSA IN THE PROCESSES OF SOIL ORGANIC MATTER TRANSFORMATION UNDER THE CONDITION OF MONOCULTURE AND MULTISPECIES PLANT COMMUNITY

The study has been carried out in the experimental field of the Centre for Ecological Research of the Polish Academy of Sciences, PAN, located in Dziekanow Leoeny (north of Warsaw). Six hundred lysimeters were installed covering the experimental area. The surface of the experimental plots (both lysimeters and their vicinity) was sown with either one grass ( Festuca rubra ) on half of the area, or with a mixture of 8 grass species on the other half of the area. In the next year, geophagous earthworms A. caliginosa were introduced to half of the lysimeters. The content of C-org, N-total, and the fractional composition of soil humus, were first determined at the beginning; at the end of the experiment also pH and the capacity of sorption complex were identified. The empirical results were subject to statistical analyses. After two years of the study, in comparison to red fescue sodding, the grass mixture sodding caused an increase in the content of organic carbon, total nitrogen and carbon of the humus fraction. The differences between the mean values of both soddings were not statistically significant. In soils under grass mixture, A. caliginosa caused an increase in the contents of organic carbon and fulvic acids carbon in relation to the initial soil; the CHA/CFA ratio significantly decreased. A slight increase in the degree of organic matter humification was observed in both soddings in combination with earthworms.

Isotopic characterization of sequestration and transformation of plant residue carbon in relation to soil aggregation dynamics

Soil aggregates play a key role in preserving soil organic carbon (SOC). However, the mechanisms controlling aggregate formation and SOC distribution in different sizes of aggregates remain unclear. Here, we studied the dynamics of aggregate formation and associated SOC transferring among different aggregate fractions using an isotopic tracer technique (14C-labeled wheat residues). The year-long incubation results demonstrate that the wheat residue carbon applied to soil (Typic Hapludoll) was initially mainly stored in the pores between microaggregates that were agglomerated to form macroaggregates (>250μm). The wheat carbon started to transfer to the inside of microaggregates (250–53μm) after six months of the incubation. The newly formed humic acid carbon (HA14C) and fulvic acid carbon (FA14C) in the macroaggregates were 57–90% and 60–84% more than in microaggregates (250–53μm), respectively. Later, the sequestrated SOC was decomposed or chemically transformed, resulting in a decrease in the ratio of HA14C/FA14C in macroaggregates and an increase in the silt/clay fraction (<53μm). This result indicated that the SOC in the macroaggregates was vulnerable to degradation due to less protection by soil macrostructure, while it experienced a slow degradation due to strong surface adsorption or pore protection in soil microstructure. This study suggests that macroaggregates considerably control SOC turnover and thereby their stability considerably influences how much newly introduced organic carbon could be sequestrated into stable carbon pools like microaggregates. The turnover dynamics of macroaggregates provided insights into the potential of humic carbon formation that facilitates long-term carbon preservation in soil.

Long-Term Grazing Exclusion Improves the Composition and Stability of Soil Organic Matter in Inner Mongolian Grasslands.

Alteration of the composition of soil organic matter (SOM) in Inner Mongolian grassland soils associated with the duration of grazing exclusion (GE) has been considered an important index for evaluating the restoring effects of GE practice. By using five plots from a grassland succession series from free grazing to 31-year GE, we measured the content of soil organic carbon (SOC), humic acid carbon (HAC), fulvic acid carbon (FAC), humin carbon (HUC), and humic acid structure to evaluate the changes in SOM composition. The results showed that SOC, HUC, and the ratios of HAC/FAC and HAC/extractable humus carbon (C) increased significantly with prolonged GE duration, and their relationships can be well fitted by positive exponential equations, except for FAC. In contrast, the HAC content increased logarithmically with prolonged GE duration. Long-term GE enhanced the content of SOC and soil humification, which was obvious after more than 10 years of GE. Solid-state 13C nuclear magnetic resonance spectroscopy showed that the ratios of alkyl C/O-alkyl C first decreased, and then remained stable with prolonged GE. Alternately, the ratios of aromaticity and hydrophobicity first increased, and then were maintained at relatively stable levels. Thus, a decade of GE improved the composition and structure of SOM in semiarid grassland soil and made it more stable. These findings provide new evidence to support the positive effects of long-term GE on soil SOC sequestration in the Inner Mongolian grasslands, in view of the improvement of SOM structure and stability.

Effects of physical-chemical properties of soils on 60Co and 65Zn bioavailability

The purposes of the paper are to estimate the inactivating power of soils in relation to radiologically important long-lived radionuclides 65Zn and 60Co and to develop methodological approaches for assessing effects of edaphic factors on the radionuclides mobility in the soil-plant system. For the experimental studies, different soil samples were collected (16 soil types, classes, and subclasses). A model experiment was carried out in a greenhouse where barley plants were grown under controlled conditions for 2 weeks on soils artificially contaminated by 65ZnCl2 and 60CoCl2. The biological availability of stable “natural” Zn, which is an aggregate of stable nuclides, radionuclides 65Zn and 60Co, was determined using the concentration ratio (CR). The physical and chemical parameters of soil (pH, the sum of silt, and clay particles (<0.01 mm) content, Fe mobile, P mobile, humus content, a ratio of humic and fulvic acid carbon (CHA/CFA), contents of mobile forms of elements (Co, Zn)) were determined. Experimental data were subjected to statistical analysis. An effort has been made to quantify the relationships between the parameters describing physical-chemical properties of soils and those that characterize 65Zn and 60Co bioavailability. A methodological approach has been used, which employs natural diversity of physical-chemical properties of different types and kinds of noncarbonate and carbonate soils in the European part of Russia, to find relevant relationships. The use of radioactive isotopes of trace elements provides an opportunity to predict the behavior of the technogenous origin metals in the soil-plant system. Methodological approach for estimation of soil characteristic contribution to common inactivating capacity in relation to radionuclide migration in the soil-plant system was suggested. On its basis, a scale of soil inactivating capacity can be developed. The derived results allow ranking of the selected physical-chemical parameters of soils by their influence on CR (65Zn or 60Co) value in barley.

Chemical characterization of soil organic profiles for assessing the European morphogenetic reference base of humus forms in Mediterranean environments

In the Castelporziano Reserved Area (Tyrrhenian coast near Rome, Italy), the organic horizons of 14 forest sites were chemically characterized to assess the European reference base of humus classification in Mediterranean ecosystems and evaluate the impacts of typical ecological disturbances on humification processes. Soils were sampled in three diagnostic horizons OL (litter), OF (fulvic) and OH (humic), and the biological type of humus were investigated on a morpho-functional basis and assigned to the taxonomic levels Mull, Amphi and Moder. For each diagnostic horizon, the total organic carbon (TOC%), the C/N ratio, the extractable carbon (TEC%), the humic and fulvic acids carbon (CHA%, CFA%), the degree (DH%) and the index of humification were determined. All data were statistically analyzed (ANOVA, post hoc HSD Tukey’s). In the OF horizon of some OL/OF sites, the CHA values were found very high, indicating the presence of a not-detected OH horizon. Conversely, part of the sites sampled with a complete humus profile, did not show differences between OF and OH, which should thus be grouped into a single diagnostic horizon. The humification parameters showed a fairly good correlation with the humus forms, limited to the first taxonomic level and the OF horizon. Overall, several discrepancies were found between humus classification and the chemical fingerprint of the humic profiles. In this regard, the use of screening analytical methods, i.e., the chemical characterization of OM, may provide a powerful support in modeling the morpho-functional references of humus forms on the peculiar features of Mediterranean forest environments.

Quantity and Quality of Organic Matter in Soil after Application of Various Organic Materials/Ilość I Jakość Materii Organicznej W Glebie Po Aplikacji Różnych Materiałów Organicznych

Abstract Organic carbon concentrations in soil, irrespective of the year of research increased significantly after application of organic materials for the soil fertilization in comparison with the soil from the NPK mineral treatment. The content of low molecular humus compounds extracted from soil using H2SO4 solution was small, regardless of the applied fertilization or year of research. However, after the third year of research a significant increase in this humus fraction content was noted in soil of all treatments where fertilization was applied. After the third year of research, carbon content in alkaline extract rose significantly in soil of all treatments where fertilization with organic materials was applied, in comparison with the soil from mineral NPK treatment. The content of humic acid carbon in soil was lower than fulvic acid carbon, which resulted in lower than one values of Cha : Cfa ratio. However, obtained results point to marked increase in both humus fractions in results of residual effect of applied fertilization. Residual effect of applied fertilization apparently increased the value of absorbance coefficient A4/6, which points to a decreased degree of condensation of humic acid molecule and greater aliphatisation.

Responses of soil nitrogen, phosphorous and organic matter to vegetation succession on the Loess Plateau of China

Revegetation is a traditional practice widely used for soil protection. We evaluated the effect of natural revegetation succession on soil chemical properties and carbon fractions (particulate organic carbon (POC), humus carbon (HS-C), humic acid carbon (HA-C) and fulvic acid carbon (FA-C)) on the Loess Plateau of China. The vegetation types, in order from the shortest to the longest enclosure duration, were: (a) abandoned overgrazed grassland (AbG3; 3 years); (b) Hierochloe odorata Beauv. (HiO7; 7 years); (c) Thymus mongolicus Ronnm (ThM15; 15 years); (d) Artemisia sacrorum Ledeb (AtS25; 25 years); (e) Stipa bungeana Trin Ledeb (StB36; 36 years) and (f) Stipa grandis P. Smirn (StG56; 56 years). The results showed that the concentrations of soil organic carbon, total nitrogen and available phosphorus increased with the increase of restoration time except for ThM15. The concentration of NH4-N increased in the medium stage (for ThM15 and AtS25) and decreased in the later stage (for StB36 and StG56) of vegetation restoration. However, NO3-N concentration significantly increased in the later stage (for StB36 and StG56). Carbon fractions had a similar increasing trend during natural vegetation restoration. The concentrations of POC, HS-C, FA-C and HA-C accounted for 24.5%–49.1%, 10.6%–15.2%, 5.8%–9.1% and 4.6%–6.1% of total carbon, respectively. For AbG3, the relative changes of POC, HS-C and FA-C were significantly higher than that of total carbon during the process of revegetation restoration. The higher relative increases in POC, HS-C and FA-C confirmed that soil carbon induced by vegetation restoration was sequestrated by higher physical and chemical protection. The increases of soil C fractions could also result in higher ecological function in semiarid grassland ecosystems.

宁南山区植被恢复对土壤团聚体水稳定及有机碳粒径分布的影响

土壤团聚作用和土壤有机碳固定之间密切相关.对宁南山区不同植被恢复措施和年限下土壤团聚体粒径分布及稳定性、土壤团聚体中有机碳及其组分分布进行了研究,探讨了有机碳及其组分对植被恢复的响应.结果表明,不同植被恢复措施下,土壤团聚体粒径分布表现为"V"字分布:> 5 mm和< 0.25 mm这两个粒径的团聚体含量最多,5-2 mm、1-0.25 mm团聚体的含量次之,2-1 mm粒径的团聚体含量最少.坡耕地的平均重量直径(MWD)最低,为1.4,其他植被恢复措施下土壤的平均重量直径MWD在1.9-3.1之间.不同的植被恢复措施下,0-20 cm土层和20-40 cm土层全土有机碳含量在7.4-17.7 g/kg之间、微生物碳含量分布在50.3-664.7 mg/kg之间、腐殖质碳含量在0.9-2.5 g/kg之间.胡敏酸碳含量分布在0.2-0.6 g/kg,富里酸碳含量在0.6-1.9 g/kg之间.全土有机碳、微生物碳、腐殖质碳、富里酸碳均为坡耕地最低,其他植被恢复措施的有机碳、微生物碳、腐殖质碳、富里酸碳含量分别是坡耕地的1.1-2.3倍、2.0-8.4倍、1.0-2.0倍、1.2-2.4倍.不同粒径团聚体有机碳相比较,大多呈现中间高两边低的变化趋势,最大值出现在中间粒径,即5-2 mm、2-1 mm、1-0.25 mm这3个粒径.逐步回归表明,5-2 mm团聚体和1-0.25 mm团聚体有机碳含量的提高有助于土壤水稳性团聚体的形成.研究结果表明,植被恢复提高了土壤团聚体有机碳含量,在碳形态上,富里酸碳和微生物生物量碳对不同植被恢复措施的敏感度较高,胡敏酸碳含量则相对稳定.;A close correlation exists between soil aggregation and soil organic carbon sequestration. Soil organic matter is the main material needed in the formation of soil aggregates and soil aggregates provide a place for soil organic matter to sequester carbon. The effects of different revegetation types on the aggregation of soil particles, the stability of soil aggregates, as well as carbon and fractions in soil aggregates were studied in a loess hilly-gully area; soil organic carbon and fraction's micro-response to different revegetation types are discussed. The results show the distribution of soil aggregates has a V distribution under a variety of revegetation and restoration measures. Small (< 0.25 mm) and large (> 5.0 mm) particle sizes form the most aggregates. The next largest aggregate size classes were 2-5 mm and 0.25-1.0 mm, while the 1-2 mm size class had the fewest aggregates. The mean weight diameter (MWD) of cropland is approximately 1.4. After land is revegetated the MWD increased to 1.9-3.1 in the soil indicating soil aggregate stability and porosity increased significantly. The aggregate stability of an area of natural grassland and also in a stand of 25-year-old <em>Caragana korshinskii </em>Kom. was higher than aggregate stability in a stand of 15-year-old <em>C. korshinskii </em>Kom. We measured various soil conditions under different revegetation types and found differences between the 0-20 cm and 20-40 cm soil layers. The soil organic carbon content was 7.4 and 17.7 g/kg; the microbial carbon content was 50.3 and 664.7 mg/kg; the carbon content of humus was 0.9 and 2.5 g/kg; the content of humic acid carbon was 0.2 and 0.6 g/kg; and the fulvic acid was 0.6 and 1.9 g/kg for the 0-20 cm and 20-40 cm soil layers, respectively. The organic carbon and the fraction in 0-20 cm soil layer were higher than measurements in 20-40 cm soil layer. The content of organic carbon, microbial carbon, humus carbon and fulvic acid carbon in the soil are the lowest in cropland; these contents under other revegetation types were 1.1-2.3 times, 2.0-8.4 times, 1.0-2.0 times and 1.2-2.4 times higher than those of cropland soils, respectively. Most of the soil organic carbon content was concentrated on intermediate sized aggregates (2-5 mm, 1-2 mm, 0.25-1.0 mm). The result of stepwise regression analysis show the higher the content of soil organic carbon was in the small and large particles (0.25-1.0 mm and 2-5 mm diameter aggregate, respectively) the more stable the water-stable aggregates were. The findings suggest vegetation restoration improved the soil organic carbon aggregate content, and in terms of forms of soil carbon, soil microbial biomass carbon and fulvic acid carbon, their content in the soil was sensitive to changes in aggregate size, while humic acid carbon was stable regardless of aggregate size.

Sorption, desorption, and degradation of (4-chloro-2-methylphenoxy)acetic acid in representative soils of the Danubian Lowland, Slovakia

Herbicide leaching through soil into groundwater greatly depends upon sorption–desorption and degradation phenomena. Batch adsorption, desorption and degradation experiments were performed with acidic herbicide MCPA and three soil types collected from their respective soil horizons. MCPA was found to be weakly sorbed by the soils with Freundlich coefficient values ranging from 0.37 to 1.03mg1−1/nkg−1L1/n. It was shown that MCPA sorption positively correlated with soil organic carbon content, humic and fulvic acid carbon contents, and negatively with soil pH. The importance of soil organic matter in MCPA sorption by soils was also confirmed by performing sorption experiments after soil organic matter removal. MCPA sorption in these treated soils decreased by 37–100% compared to the original soils. A relatively large part of the sorbed MCPA was released from soils into aqueous solution after four successive desorption steps, although some hysteresis occurred during desorption of MCPA from all soils. Both sorption and desorption were depth-dependent, the A soil horizons exhibited higher retention capacity of the herbicide than B or C soil horizons. Generally, MCPA sorption decreased in the presence of phosphate and low molecular weight organic acids. Degradation of MCPA was faster in the A soil horizons than the corresponding B or C soil horizons with half-life values ranging from 4.9 to 9.6d in topsoils and from 11.6 to 23.4d in subsoils.

Transformation of some organic matter components in organic soils exposed to drainage

In drained Histosols used as pastures or arable fields the muck-forming process transforms organic soil formations into muck. The rush vegetation (Caricetum acutiformis and Glycerietum maximae) covering Histosols in the organic matter accumulation stage is replaced by meadow vegetation (Molinietalia order). During sustained drainage mucks are transformed into muck-like formations that contain less than 12% organic carbon. The aim of this study was to report the changes in organic matter initiated by the muck-forming process. Soil organic matter was fractionated into humic-acid carbon, fulvic-acid carbon, and humins. The amount of carbon susceptible to oxidation with KMnO4 was also determined and, based on these results, lability, carbon pool, and management indices were calculated. Additionally, hot-water extractable carbon, corresponding to microbial biomass, was determined. The study's results show that the muck-forming process caused a decrease in organic carbon and the concentration of total nitrogen, indicating a reduction in carbon sequestration in the soils. The humin fraction was predominant in untransformed soils and was positively correlated with clay, total nitrogen, and non-oxidizable carbon. Drainage of Histosols contributed to increasing the solubility of humus compounds. The humification index, and the content of humic and fulvic acids was higher in drained soils. Humic acids and fulvic acids content was 24% and 11%-12% of organic carbon, respectively. Muck formations contained more humic acids than muck-like formations. Higher \SigmaCHCF:humins ratios were also observed in drained soils. In muck-like formations this ratio was 0.91 (11-fold higher than in reference soils). Drainage contributed to an increase in hot-water extractable carbon. Carbon indices were higher in mucks than in muck-like formations.

Organic carbon and nitrogen stocks in reed meadow soils converted to alfalfa fields

Soil organic carbon and nitrogen are key elements of sustainable agriculture. Converting forest land and grassland to arable land is known to decrease the content of soil organic carbon (SOC), whereas converting land under annual crops into perennial grasslands has the potential to increase organic C and N sequestration, an assumption tested in this study. Compared to the levels in reed meadows, SOC and total nitrogen (TN) stocks in the top layer of 2489 Mg soil ha −1 (about 0–15 cm depth) significantly increased 3 years after the conversion, despite a slight decrease numerically in the first year following the conversion. And the mass of light fraction organic carbon (LFOC), total extractable carbon (TEC), humic acid carbon (HAC), and fulvic acid carbon (FAC) stocks all decreased significantly in the first year in the top layer but recovered after 3 years. In the deeper layer of 2549 Mg soil ha −1 (about 15–30 cm depth), however, the levels of SOC and heavy fraction organic carbon (HFOC) stocks began increasing from the first year itself. During the period of 1–10 years after the conversion, the degree of humification rate (HR) for the deeper layer were consistent, averaging 30%, whereas the same parameters in the top layer stabilized after 3 years at 33%. After 10 years of conversion, the soil recorded higher levels of SOC and TN stocks, used as indicators in this study, than those that had prevailed in the reed meadows, demonstrating the positive combined effects of the conversion on the retention of atmospheric C-CO 2 in the soil. This study suggests that proper management of alfalfa fields can maintain or even improve chemical and physical quality of converted reed meadows soils.

Fire impact on forest soils evaluated using near-infrared spectroscopy and multivariate calibration

The assessment of physico-chemical properties in forest soils affected by fires was evaluated using near infrared reflectance (NIR) spectroscopy coupled with chemometric methods. In order to describe the soil properties, measurements were taken of the total organic carbon on solid phase, the total nitrogen content, the organic carbon and the specific absorbences at 254 and 280 nm of humic substances, organic carbon in humic and fulvic acids, concentrations of NH 4 +, Ca 2+, Mg 2+, K + and phosphorus in addition to NIR spectra. Then, a fire recurrence index was defined and calculated according to the different fires extents affecting soils. This calculation includes the occurrence of fires as well as the time elapsed since the last fire. This study shows that NIR spectroscopy could be considered as a tool for soil monitoring, particularly for the quantitative prediction of the total organic carbon, total nitrogen content, organic carbon in humic substances, concentrations of phosphorus, Mg 2+, Ca 2+ and NH 4 + and humic substances UVSA 254. Further validation in this field is necessary however, to try and make successful predictions of K +, organic carbon in humic and fulvic acids and the humic substances UVSA 280. Moreover, NIR coupled with PLS can also be useful to predict the fire recurrence index in order to determine the spatial variability. Also this method can be used to map more or less burned areas and possibly to apply adequate rehabilitation techniques, like soil litter reconstitution with organic enrichments (industrial composts) or reforestation. Finally, the proposed recurrence index can be considered representative of the state of the soils.

Effect of soil and sediment composition on acetochlor sorption and desorption

Herbicide fate and its transport in soils and sediments greatly depend upon sorption-desorption processes. Quantitative determination of herbicide sorption-desorption is therefore essential for both the understanding of transport and the sorption equilibrium in the soil/sediment-water system; and it is also an important parameter for predicting herbicide fate using mathematical simulation models. The total soil/sediment organic carbon content and its qualitative characteristics are the most important factors affecting sorption-desorption of herbicides in soil or sediment. Since the acetochlor is one of the most frequently used herbicides in Slovakia to control annual grasses and certain annual broad-leaved weeds in maize and potatoes, and posses various negative health effects on human beings, our aim in this study was to investigate acetochlor sorption and desorption in various soil/sediment samples from Slovakia. The main soil/sediment characteristics governing acetochlor sorption-desorption were also identified. The sorption-desorption of acetochlor, using the batch equilibration method, was studied on eight surface soils, one subsurface soil and five sediments collected from the Laborec River and three water reservoirs. Soils and sediments were characterized by commonly used methods for their total organic carbon content, distribution of humus components, pH, grain-size distribution, and smectite content, and for calcium carbonate content. The effect of soil/sediment characteristics on acetochlor sorption-desorption was examined by simple correlation analysis. Sorption of acetochlor was expressed as the distribution coefficient (K (d)). K (d) values slightly decreased as the initial acetochlor concentration increased. These values indicated that acetochlor was moderately sorbed by soils and sediments. Highly significant correlations between the K (d) values and the organic carbon content were observed at both initial concentrations. However, sorption of acetochlor was most closely correlated to the humic acid carbon, and less to the fulvic acid carbon. The total organic carbon content was found to also significantly influence acetochlor desorption. Since the strong linear relationship between the K (d) values of acetochlor and the organic carbon content was already released, the corresponding K (oc) values were calculated. Considerable variation in the K (oc) values suggested that other soil/sediment parameters besides the total soil organic carbon content could be involved in acetochlor sorption. This was revealed by a significant correlation between the K (oc) values and the ratio of humic acid carbon to fulvic acid carbon (C(HA)/C(FA)). When comparing acetochlor sorption in a range of soils and sediments, different K (d) values which are strongly correlated to the total organic carbon content were found. Concerning the humus fractions, the humic acid carbon content was strongly correlated to the K (d) values, and it is therefore a better predictor of the acetochlor sorption than the total organic carbon content. Variation in the K (oc) values was attributed to the differences in distribution of humus components between soils and sediments. Desorption of acetochlor was significantly influenced by total organic carbon content, with a greater organic carbon content reducing desorption. This study examined the sorption-desorption processes of acetochlor in soils and sediments. The obtained sorption data are important for qualitative assessment of acetochlor mobility in natural solids, but further studies must be carried out to understand its environmental fate and transport more thoroughly. Although, the total organic carbon content, the humus fractions of the organic matter and the C(HA)/C(FA) ratio were sufficient predictors of the acetochlor sorption-desorption. Further investigations of the structural and chemical characteristics of humic substances derived from different origins are necessary to more preciously explain differences in acetochlor sorption in the soils and sediments observed in this study.

Ozonation of Animal Wastes Containing Oxytetracycline

The efficiency of ozonation on the degradation of oxytetracycline, a veterinary antibiotic, has been investigated in both cow manure and synthetic animal feeding operation wastewater at varying experimental conditions. With a rapid degradation of antibiotic in synthetic wastewater, ozonation improved its biodegradability and eliminated bacterial toxicity caused by oxytetracycline. The degradation rate of oxytetracycline depended on pH and applied ozone dose, but not initial antibiotic concentration in wastewater. In the case of manure treatment, ozonation efficiency in terms of oxytetracycline degradation was negatively affected by moisture and antibiotic content of manure. The degradation rate of oxytetracycline in manure slowed down upon the extension of treatment time since ozone could not react with strongly adsorbed antibiotic on manure. Increase in humic and fulvic acid carbon and mineral nitrogen content was an indicator for the improvement of fertilizing value of manure by ozonation.

Maturity assessment of composted olive mill wastes using UV spectra and humification parameters

In this study, two olive mill wastes – exhausted olive cake (EOC) and paste of olive mill wastewater naturally dehydrated (POMW) – were co-composted and mixed with 25% sesame bark (SB). The humification process was evidenced by quantifying the humic substances and the generally accepted humification indices: (i) the ratio of humic acid (HA) carbon to fulvic acid (FA) carbon (CHA/CFA), (ii) the ratio of water soluble organic carbon (CW) to total organic nitrogen (Cw/Norg), (iii) and the ratio of humic acid carbon to total organic carbon CHA/Corg and by determining the absorbance ratios: E2/E4, E2/E6 and E4/E6. The results showed that the time required to reach maturity was dependant on the chemical properties of the initial raw materials used. The compost including EOC had more nitrogen and synthesised more polymerised HA, the POMW compost also had acceptable degrees of stability and maturity at the end of the process. Maturation was confirmed by a decline in Cw below 1.7, an increase in nitrogen, in HA, in CHA/CFA and an elimination of phytotoxicity. Composts produced with olive mill wastes, experimented on potato culture in the field, can be considered beneficial to soils because of their humification indexes and no toxicity.

Influence of treatment techniques on Cu leaching and different organic fractions in MSWI bottom ash leachate

The leaching of heavy metals, such as copper, from municipal solid waste incinerator (MSWI) bottom ash is of concern in many countries and may inhibit the beneficial reuse of this secondary material. Previous studies have focused on the role of dissolved organic carbon (DOC) on the leaching of copper. Recently, a study of the Energy Research Centre of The Netherlands (ECN) showed fulvic acid-type components to exist in the MSWI bottom ash leachates and to be likely responsible for the generally observed enhanced copper leaching. These findings were verified for a MSWI bottom ash (∅ 0.1–2 mm) fraction from an incinerator in Flanders. The filtered leachates were subjected to the IHSS fractionation procedure to identify and quantify the fractions of humic acid (HA), fulvic acid (FA) and hydrophilic organic carbon (Hi). The possible complexation of fulvic acid with other heavy metals (e.g., lead) was also investigated. The identified role of fulvic acids in the leaching of copper and other heavy metals can be used in the development of techniques to improve the environmental quality of MSWI bottom ash. Thermal treatment and extraction with a 0.2 M ammonium-citrate solution were optimized to reduce the leaching of copper and other heavy metals. The effect of these techniques on the different fractions of organic matter (HA, FA, Hi) was studied. However, due to the obvious drawbacks of the two techniques, research is focused on finding other (new) techniques to treat MSWI bottom ash. In view of this, particle size-based separation was performed to evaluate its effect on heavy metal leaching and on HA, FA and Hi in MSWI bottom ash leachates.