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1.
Iris Hindersmann Jörg Hippler Alfred V. Hirner Tim Mansfeldt 《Journal of Soils and Sediments》2014,14(9):1549-1558
Purpose
Middle-European floodplain soils are often contaminated with mercury (Hg) and periodically flooded. In this study, the influence of a flooding event and subsequent dewatering on the volatilization of elemental Hg and methylated species was investigated in a laboratory experiment.Material and methods
Undisturbed soil cores were taken from a topsoil (12.1?±?0.75 mg kg?1 Hg) at the Elbe River in Lower Saxony, Germany. Soil columns were incubated at 20 °C with varying soil moisture (water-saturated for 2 weeks, 95 and 90 % water content for 1 week each), and the redox potential (EH) was recorded. The gaseous Hg that accumulated in the headspace of the flux chamber of the columns was pumped over cooled traps filled with adsorber material and analyzed by gas chromatography/inductively coupled plasma mass spectrometry for the various Hg species.Results and discussion
The watering of the soil resulted in a rapid decrease in the EH and the achievement of strongly reducing conditions (EH??100 mV). Mercury concentrations of the pore waters decreased continuously from 68.3 μg L?1 Hg at the beginning to 5.78 μg L?1 Hg at the end of the experiment. Species analyses revealed that exclusively elemental Hg volatilized. The volatilization rate was between 1.73 and 824 ng m?2 h?1 Hg, which is consistent with other studies at the Elbe River.Conclusions
Even when flooded for a longer period of time, floodplain soils should show neither emission of methylated Hg nor exceptionally high volatilization of elemental Hg. 相似文献2.
Li Jiang Jun Zhu Hui Wang Qingling Fu Hongqing Hu Qiaoyun Huang Antonio Violante Li Huang 《Journal of Soils and Sediments》2014,14(8):1378-1384
Purpose
Sorption of humic substances on other soil components plays an important role in controlling their function and fate in soil. Sorption of humic substances by individual soil components has been studied extensively. However, few studies reported the sorption characteristic of humic substances on composites of soil components. This study aimed to investigate the sorption characteristics of humic acid on Fe oxide-bacteria composites and improve the understanding on the interaction among humic substance Fe oxide bacteria in soil.Materials and methods
Humic acid was purchased from Sigma-Aldrich and was purified. Hematite and ferrihydrite were synthesized in the lab. Bacillus subtilis and Pseudomonas putida were cultivated in Luria-Broth medium and harvested at stationary growth phase. Batch sorption experiments were carried out at pH 5.0. Various amounts of humic acid were mixed with 20 mg of Fe oxide, bacteria, or Fe oxide-bacteria composite (oxide to bacteria of 1:1) in 10 mL of KCl (0.02 mol L?1) to construct sorption isotherms. The effects of phosphate concentration and addition order among humic acid, Fe oxide, bacteria on the sorption of humic acid were also studied. The sorption of humic acid was calculated by the difference between the amount of humic acid added initially and that remained in the supernatant.Results and discussion
The maximum sorption of humic acid on hematite, ferrihydrite, B. subtilis and P. putida was 73.2, 153.5, 69.1, and 56.7 mg C g?1, respectively. The maximum sorption of humic acid on examined Fe oxide-bacteria composite was 28.2–57.2 % less than the predicted values, implying that the sorption of humic acid was reduced by the interaction between Fe oxides and bacteria. The presence of phosphate exerted negligible influence on the sorption of humic acid on bacteria while it inhibited the sorption of humic acid on Fe oxides. On Fe oxide-bacteria composites, inhibiting influences followed by promoting or weak inhibiting effects of phosphate with increasing concentration on the sorption of humic acid were found.Conclusions
The interaction between Fe oxides and bacteria reduced the sorption of humic acid; moreover, the reduction was greater by the interaction of bacteria with ferrihydrite than that with hematite. Phosphate exerted negligible and inhibiting influence on the sorption of humic acid by bacteria and Fe oxides, respectively. On Fe oxide-bacteria composites, humic acid sorption was initially inhibited and then promoted or weakly inhibited by phosphate with increasing concentration. 相似文献3.
Liyuan Chai Jingwen Tang Yingping Liao Zhihui Yang Lifeng Liang Qingzhu Li Haiying Wang Weichun Yang 《Journal of Soils and Sediments》2016,16(10):2430-2438
Purpose
Soil contamination with arsenic (As) is an increasingly worldwide concern. Immobilization is a potentially reliable, cost-effective technique for the reclamation of As-contaminated soils. The aim of this study is to develop new soil amendments with high As immobilization efficiency, cost-effective, environmental-friendly, and without soil acidification for As-contaminated soil remediation.Materials and methods
Biosynthesis of schwertmannite by Acidithiobacillus ferrooxidans has been conducted, and two types of biogenetic schwertmannites SCH and A-SCH were prepared and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), etc. The A-SCH was formed through pretreating SCH by acidic and alkaline activation. The potential of SCH and A-SCH in As immobilization in contaminated soil was evaluated. The effect of ferrous sulfate and A-SCH on soil pH and immobilization of NaHCO3-extractable As were also investigated for comparison.Results and discussion
The chemical formula of SCH and A-SCH can be expressed as Fe8O8(OH)4.89(SO4)1.55 and Fe8O8(OH)5.19(SO4)1.41, respectively. Compared to SCH, A-SCH exhibits much higher specific surface area of 74.99 m2 g?1 and contains more hydroxyl groups and inner-sphere sulfate complexes. Immobilization efficiency of water-soluble As above 99.5 % can be achieved with A-SCH dosage of 5 % and SCH dosage of 10 %, respectively. The immobilization percentages of NaHCO3-extractable As increased from 31.5 to 90.4 % and from 40.2 to 93.8 % with increasing dosage from 0.5 to 10 wt % for SCH and A-SCH, respectively. In general, both SCH and A-SCH immobilize As in contaminated soil effectively, and the immobilization performance of A-SCH was better than that of SCH, especially at lower dosage.Conclusions
Biogenetic schwertmannite could be used as a potential effective soil amendment for As immobilization in contaminated soil. Our findings in this study also have important implications for in situ immobilization of As in contaminated soils, especially the soils related to acidic iron and sulfate-rich environments.4.
Dina G. Nevidomskaya Tatiana M. Minkina Alexander V. Soldatov Victoria A. Shuvaeva Yan V. Zubavichus Yulia S. Podkovyrina 《Journal of Soils and Sediments》2016,16(4):1183-1192
Purpose
The study is aimed at the analysis of the spatial–structural organization of Pb(II) in Chernozem soils and the relationship between the metal ion and the soil components using X-ray absorption spectroscopy and chemical extractive fractionation.Materials and methods
In a model experiment, soil samples were artificially contaminated with elevated rates of Pb(NO3)2 and PbO (2000 and 10,000 mg kg?1). The samples of mineral phases (bentonite, gibbsite, kaolinite, calcite, and hydromuscovite) were saturated with Pb2+ ions. The sequential fractionation of Pb in the soil was conducted by the Tessier method. X-ray absorption near-edge fine structure (XANES) spectra at the Pb LIII-edge (13.040 keV) were obtained on a Rigaku R-XAS Looper spectrometer. Extended X-ray absorption fine structure (EXAFS) LIII-edge Pb was measured at the Structural Materials Science beamline of the Kurchatov Center for Synchrotron Radiation.Results and discussion
The results of successive extraction showed that Pb is associated with strongly bound organic substances, Fe and Mn (hydr)oxides, and carbonates. An increase in the portion of exchangeable fraction is observed under extreme loads. At the addition of Pb in the form of oxide and nitrate to the soil, the fractional compositions were similar, which indicates the good transformation of PbO in Chernozem. The features of XANES spectra indicate different orbital transitions in the electron shells of Pb2+ ions for monoxide (PbO) and soluble salt (Pb(NO3)2), which affect the ion properties and determine the individual structure of the coordination sphere. The analysis of XANES revealed that sorption of Pb in the soil samples and in the samples of mineral phases does not change its bond valence.Conclusions
The increased degree of soil contamination with Pb is accompanied by decreasing the stable connection between metal and soil components. Lead ions in bentonite, kaolinite, hydromuscovite, gibbsite, and calcite are incorporated in the positions of the inner-sphere complex replacing some aluminum ions in the octahedral sites. This results in changes the Pb–O distances in Pb-bearing octahedrons. We may suggest that Pb2+ is also sorbed by dimer (Pb–Pb) silicate and/or aluminum groups. The structure of adsorbent surface plays the key role in the sorption of Pb2+ by mineral phases.5.
Ines Ahumada Karen Sepúlveda Priscilla Fernández Loreto Ascar Cristina Pedraza Pablo Richter Sally Brown 《Journal of Soils and Sediments》2014,14(5):886-896
Purpose
This study assessed the effect of biosolid application on the bioavailable fraction of some trace elements (Cu, Cr, Ni, and Zn) using a bioassay with sunflower (Helianthus annuus) and a chemical assay, diffusion gradient in thin films (DGT).Materials and methods
Five surface soil samples (0–20 cm) were collected from an agricultural zone in Central Chile where biosolids are likely to be applied. Municipal biosolids were mixed with the soil at concentrations of 0, 30, 90, and 200 Mg ha?1. The experiment to determine the bioavailability of metals in the soil using the bioassay was performed using sunflower. The DGT technique and Community Bureau of Reference (BCR) sequential extraction were used to determine the bioavailable fractions of the metals.Results and discussion
The application of biosolids increased the phytoavailability of Zn, Ni, and Cr in most of the soils, as indicated by the increasing concentrations in sunflower plants as the biosolid application rate increased. In two of the soils, Codigua and Pelvín, this increase peaked at an application rate of 90 Mg ha?1. Decreases in the bioavailable fractions of Zn, Ni, and Cr were observed with higher biosolid application rates. The bioavailability of metals was estimated through multiple linear regression models between the metals in the sunflower plants and the different chemical fractions of metals in the soils treated with different biosolid rates, which displayed a positive contribution of the labile (water soluble, carbonate, and exchangeable), oxide, and organic metal forms in the soil, particularly with respect to Ni and Zn at application rates of 30 and 90 Mg ha?1. The bioavailable fraction of metals was determined in soils using the DGT technique. The effective concentration (C E) results were compared with those in sunflower plants. The DGT technique could effectively predict the bioavailable fractions of Cr, Ni, and Zn in the Taqueral soil but only that of Zn in the Polpaico soil.Conclusions
The application of biosolids significantly increased the labile fraction of most of the metals in the studied soils, particularly at the highest biosolid application rate. C E increased as the concentration of biosolids increased for most of the metals. The effectiveness of the DGT technique for predicting the bioavailability of metals was dependent on the soil type and the metal. However, the C E for soil Cu was not related to plant Cu for all soils studied. 相似文献6.
Wenjie Pan Zhaoliang Song Hongyan Liu Lukas Van Zwieten Yutong Li Xiaomin Yang Yue Han Xu Liu Xiaodong Zhang Zijuan Xu Hailong Wang 《Journal of Soils and Sediments》2017,17(10):2420-2427
Purpose
A better understanding of the role of grassland systems in producing and storing phytolith-occluded carbon (PhytOC) will provide crucial information in addressing global climate change caused by a rapid increase in the atmospheric CO2 concentration.Materials and methods
Soil samples of typical steppe, meadow steppe, and meadow in Inner Mongolia, China, were taken at 0–10-, 10–20-, 20–40-, and 40–60-cm depths in July and August of 2015. The soil phytoliths were isolated by heavy liquid (ZnBr2), and the soil PhytOC was determined by the traditional potassium dichromate method.Results and discussion
The results of our study showed that the storage of soil phytoliths was significantly higher in the meadow (33.44 ± 0.91 t ha?1) cf. meadow steppe (26.8 ± 0.98 t ha?1) and typical steppe (21.19 ± 4.91 t ha?1), which were not different. The soil PhytOC storage was significantly different among grassland types, being: meadow (0.39 ± 0.01 t ha?1) > meadow steppe (0.29 ± 0.02 t ha?1) > typical steppe (0.23 ± 0.02 t ha?1). PhytOC storage in typical steppe soil within the 0–60-cm soil layer is the lowest and that in meadow soils is the highest. The grassland type and the soil condition play significant roles in accumulation of phytoliths and PhytOC in different grassland soils. We suggest that the aboveground net primary productivity (ANPP) is important in soil phytolith accumulation and PhytOC content.Conclusions
Phytolith and PhytOC storages in grassland soil are influenced by factors such as grass type, local climate and soil conditions, and management practices. Management practices to increase grass biomass production can significantly enhance phytolith C sequestration.7.
Purpose
The main objective of this study was to evaluate the potential of a counter-current leaching process (CCLP) on 14 cycles with leachate treatment at the pilot scale for Pb, Cu, Sb, and Zn removal from the soil of a Canadian small-arms shooting range.Materials and methods
The metal concentrations in the contaminated soil were 904?±?112 mg Cu kg–1, 8,550?±?940 mg Pb kg–1, 370?±?26 mg Sb kg–1, and 169?±?14 mg Zn kg–1. The CCLP includes three acid leaching steps (0.125 M H2SO4?+?4 M NaCl, pulp density (PD)?=?10 %, t?=?1 h, T?=?20 °C, total volume?=?20 L). The leachate treatment was performed using metal precipitation with a 5-M NaOH solution. The treated effluent was reused for the next metal leaching steps.Results and discussion
The average metal removal yields were 80.9?±?2.3 % of Cu, 94.5?±?0.7 % of Pb, 51.1?±?4.8 % of Sb, and 43.9?±?3.9 % of Zn. Compared to a conventional leaching process, the CCLP allows a significant economy of water (24,500 L water per ton of soil), sulfuric acid (133 L H2SO4 t–1), NaCl (6,310 kg NaCl t–1), and NaOH (225 kg NaOH t–1). This corresponds to 82 %, 65 %, 90 %, and 75 % of reduction, respectively. The Toxicity Characteristic Leaching Procedure test, which was applied on the remediated soil, demonstrated a large decrease of the lead availability (0.8 mg Pb L–1) in comparison to the untreated soil (142 mg Pb L–1). The estimated total cost of this soil remediation process is 267 US$ t–1.Conclusions
The CCLP process allows high removal yields for Pb and Cu and a significant reduction in water and chemical consumption. Further work should examine the extraction of Sb from small-arms shooting range. 相似文献8.
Iron-cyanide complexes in soil under varying redox conditions: speciation, solubility and modelling 总被引:1,自引:0,他引:1
The distribution of iron‐cyanide complexes between ferrocyanide, [FeII(CN)6]4–, and ferricyanide, [FeIII(CN)6]3–, in soils on contaminated sites depends on the redox potential, EH. We carried out microcosm experiments in which ferrocyanide (20 mg l?1) was added to an uncontaminated moderately acidic subsoil (pH 5.2), and varied the EH of the soil suspension between 200 and 700 mV over up to 109 days. Ferrocyanide and ferricyanide were analysed by capillary isotachophoresis. At redox potentials ranging from 400 to 700 mV, small amounts of iron‐cyanide complexes were adsorbed, and ferrocyanide was almost completely oxidized to ferricyanide. Decreasing EH to 200 mV led to nearly complete removal of iron‐cyanide complexes from solution, and the complexes were not mobilized after subsequent aeration (EH > 350 mV). Under weakly to moderately reducing conditions (EH ≈ 200 mV), iron‐cyanide complexes were removed from solution by precipitation, which occurred, presumably in the form of e.g. Fe2[FeII(CN)6], Fe4[FeII(CN)6]3 or Mn2[FeII(CN)6], after reductive dissolution of Mn and Fe oxides. Four different sets of geochemical model calculations were carried out. The species distribution between ferrocyanide and ferricyanide in solution was predicted reliably under varying pH and redox conditions when iron‐cyanide complex concentrations and Fe concentrations, excluding Fe bound in iron‐cyanide complexes, were used in model calculations. In model calculations on the fate of iron‐cyanide complexes in soil, adsorption reactions must be considered, especially under oxidizing conditions. Otherwise, the calculated iron‐cyanide complex concentrations are larger than those actually measured. 相似文献
9.
Bing Han Xuhong Ye Wen Li Xichao Zhang Yulong Zhang Xiangui Lin Hongtao Zou 《Journal of Soils and Sediments》2017,17(10):2457-2468
Purpose
Intensive agricultural practices have enhanced problems associated with the competing use of limited water resources. Nitrous oxide (N2O) is a major contributor to global warming. It is important for researchers to ascertain the relationship between irrigation and soil N2O emissions in order to identify mitigation strategies to reduce nitrous oxide emissions. Different irrigation amounts affect soil water dynamics and nitrogen turnover. The effect of three lower limits of irrigation on soil N2O emissions, influencing factors, and abundance of genes involved in nitrification and denitrification were investigated in tomato irrigated in a greenhouse.Materials and methods
Observations were performed between April and August 2015 in a long-term irrigated field subjected to different lower limits of irrigation: 20 kPa (D20), 30 kPa (D30), and 40 kPa (D40) from greenhouse soil during the tomato crop season. Soil N2O fluxes were monitored using the static chamber-gas chromatograph method. Copy numbers of genes were determined using the real-time quantitative polymerase chain reaction (real-time PCR) technique. Characteristics of soil N2O emissions were analyzed, and differences between irrigation regimes were determined. The effects of influencing factors on soil N2O emissions were analyzed, including soil temperature, soil moisture, soil pH, and soil mineral nitrogen, as well as changes in the abundance of soil ammonia-oxidizing bacteria (AOB) and ammonia-oxidizing archaea (AOA) based on amoA genes and denitrifier genes (nosZ, nirK, and cnorB).Results and discussion
Our results showed that peaks in N2O emissions occurred 1–5 days after each irrigation. During the whole tomato growth period, soil N2O fluxes were lowest under D30 treatment compared with those under D20 and D40 treatments. Soil NO3 ?-N concentrations were significantly higher than NH4 +-N concentrations. Soil N2O fluxes were significantly related to soil moisture, NH4 +-N concentrations (P < 0.01), soil pH, and AOA copy numbers (P < 0.05). There was no consistent correlation between soil N2O emissions, soil temperature, and soil NO3 ?-N concentrations. Different irrigation regimes significantly affected AOA copy numbers but did not affect the expression of other genes. AOA copy numbers were higher than those of AOB. Soil N2O fluxes significantly affected the AOA copy numbers and potential nitrification rates (P < 0.05).Conclusions
Soil moisture, pH, and NH4 +-N concentration were important factors affecting soil N2O emissions. Compared with other genes associated with nitrification and denitrification, AOA plays an important role in N2O emissions from greenhouse soils. Selecting a lower limit of irrigation of 30 kPa could effectively reduce N2O emissions from vegetable soils.10.
Zhijie Chen Heikki Setälä Shicong Geng Shijie Han Shuqi Wang Guanhua Dai Junhui Zhang 《Journal of Soils and Sediments》2017,17(1):23-34
Purpose
Anthropogenic-induced greenhouse gas (GHG) emission rates derived from the soil are influenced by long-term nitrogen (N) deposition and N fertilization. However, our understanding of the interplay between increased N load and GHG emissions among soil aggregates is incomplete.Materials and methods
Here, we conducted an incubation experiment to explore the effects of soil aggregate size and N addition on GHG emissions. The soil aggregate samples (0–10 cm) were collected from two 6-year N addition experiment sites with different vegetation types (mixed Korean pine forest vs. broad-leaved forest) in Northeast China. Carbon dioxide (CO2), nitrous oxide (N2O), and methane (CH4) production were quantified from the soil samples in the laboratory using gas chromatography with 24-h intervals during the incubation (at 20 °C for 168 h with 80 % field water capacity).Results and discussion
The results showed that the GHG emission/uptake rates were significantly higher in the micro-aggregates than in the macro-aggregates due to the higher concentration of soil bio-chemical properties (DOC, MBC, NO3 ?, NH4 +, SOC and TN) in smaller aggregates. For the N addition treatments, the emission/uptake rates of GHG decreased after N addition across aggregate sizes especially in mixed Korean pine forest where CO2 emission was decreased about 30 %. Similar patterns in GHG emission/uptake rates expressed by per soil organic matter basis were observed in response to N addition treatments, indicating that N addition might decrease the decomposability of SOM in mixed Korean pine forest. The global warming potential (GWP) which was mainly contributed by CO2 emission (>98 %) decreased in mixed Korean pine forest after N addition but no changes in broad-leaved forest.Conclusions
These findings suggest that soil aggregate size is an important factor controlling GHG emissions through mediating the content of substrate resources in temperate forest ecosystems. The inhibitory effect of N addition on the GHG emission/uptake rates depends on the forest type.11.
Xi-En Long Ju-Pei Shen Jun-Tao Wang Li-Mei Zhang Hongjie Di Ji-Zheng He 《Journal of Soils and Sediments》2017,17(2):384-392
Purpose
Nitrification and denitrification processes dominate nitrous oxide (N2O) emission in grassland ecosystems, but their relative contribution as well as the abiotic factors are still not well understood.Materials and methods
Two grassland soils from Duolun in Inner Mongolia, China, and Canterbury in New Zealand were used to quantitatively compare N2O production and the abundance of bacterial and archaeal amoA, denitrifying nirK and nirS genes in response to N additions (0 and 100 μg NH4 +–N g?1 dry soil) and two soil moisture levels (40 and 80 % water holding capacity) using microcosms.Results and discussion
Soil moisture rather than N availability significantly increased the nitrification rate in the Duolun soil but not in the Canterbury soil. Moreover, N addition promoted denitrification enzyme activities in the Canterbury soil but not in the Duolun soil. The abundance of bacterial and archaeal amoA genes significantly increased as soil moisture increased in the Duolun soil, whereas in the Canterbury soil, only the abundance of bacterial amoA gene increased. The increase in N2O flux induced by N addition was significantly greater in the Duolun soil than in the Canterbury soil, suggesting that nitrification may have a dominant role in N2O emission for the Duolun soil, while denitrification for the Canterbury soil.Conclusions
Microbial processes controlling N2O emission differed in grassland soils, thus providing important baseline data in terms of global change.12.
Muhammad Farrakh Nawaz Guilhem Bourrié Fabienne Trolard Jacques Ranger Sadaf Gul Nabeel Khan Niazi 《Journal of Soils and Sediments》2016,16(9):2223-2233
Purpose
Soil compaction resulting from mechanisation of forest operations reduces air permeability and hydraulic conductivity of soil and can result in the development of hydromorphic and/or anoxic conditions. These hydromorphic conditions can affect physico-chemical properties of the soils. However, early detection of these effects on mineralogical portion of soils is methodologically difficult.Materials and methods
To analyse the effects of soil compaction on iron minerals in loamy Luvisol, three compacted and three non-compacted soil profiles up to the depth of 50 cm were collected from an artificially deforested and compacted soils after 2 years of treatment. Soil was compacted with the help of 25 Mg wheeler’s load to increase the dry bulk density of soil from 1.21?±?0.05 to 1.45?±?0.1 g cm?3. Soil samples were analysed by X-ray diffraction (XRD) and were treated by citrate bicarbonate (CB) and dithionite citrate bicarbonate (DCB) under controlled conditions. Major and minor elements (Fe, Al, Mg, Si and Mn) were analysed by ICP-AES in the CB and DCB extracts.Results and discussion
It was found that X-ray diffraction is not an enough sensitive method to detect the quick mineralogical changes due to soil compaction. Results obtained from CB-DCB extractions showed that soil compaction resulted in larger CB and smaller DCB extractable elements as compared to non-compacted soil. Labile Fe was found 30 % of total Fe oxides in compacted soil against 10–14 % in non-compacted soils. Compaction thus resulted in Fe transfer from non-labile to labile oxides (s.l.). Results showed that soil compaction leads to the reduction of Fe3+ to Fe2+. The effects of hydromorphic conditions due to soil compaction were observed up to the depth of 35 cm in forest soil profile. Furthermore, a close association of Al with Fe oxides was observed in the soil samples, while Mn and Si were mainly released from other sources, Mg showing an intermediate behaviour.Conclusions
Hydromorphic conditions owing to soil compaction affect the mobility and crystallisation process of iron mineral. CB-DCB selective extraction technique, in contrast to XRD technique, can be effectively used to examine the possible effects of soil compaction on iron minerals.13.
Zejiang Cai Minggang Xu Boren Wang Lu Zhang Shilin Wen Suduan Gao 《Journal of Soils and Sediments》2018,18(9):2893-2903
Purpose
Crop straws and animal manure have the potential to ameliorate acidic soils, but their effectiveness and the mechanisms involved are not fully understood. The aim of this study was to evaluate the effectiveness of two crop (maize and soybean) straws, swine manure, and their application rates on acidity changes in acidic red soils (Ferralic Cambisol) differing in initial pH.Materials and methods
Two red soils were collected after 21 years of the (1) no fertilization history (CK soil, pH 5.46) and (2) receiving annual chemical nitrogen (N) fertilization (N soil, pH 4.18). The soils were incubated for 105 days at 25 °C after amending the crop straws or manure at 0, 5, 10, 20, and 40 g kg?1 (w/w), and examined for changes in pH, exchangeable acidity, N mineralization, and speciation in 2 M KCl extract as ammonium (NH4+) and nitrate plus nitrite (NO3??+?NO2?).Results and discussion
All three organic materials significantly decreased soil acidity (dominated by aluminum) as the application rate increased. Soybean straw was as effective (sometimes more effective) as swine manure in raising pH in both soils. Soybean straw and swine manure both significantly reduced exchangeable acidity at amendment rate as low as 10 g kg?1 in the highly acidic N soil, but swine manure was more effective in reducing the total acidity especially exchangeable aluminum (e.g., in the N soil from initial 5.79 to 0.50 cmol(+) kg?1 compared to 2.82 and 4.19 cmol(+) kg?1 by soybean straw and maize straw, respectively). Maize straw was less effective than soybean straw in affecting soil pH and the acidity. The exchangeable aluminum decreased at a rate of 4.48 cmol(+) kg?1 per pH unit increase for both straws compared to 6.25 cmol(+) kg?1 per pH unit from the manure. The NO3??+?NO2? concentration in soil increased significantly for swine manure amendment, but decreased markedly for straw treatments. The high C/N ratio in the straws led to N immobilization and pH increase.Conclusions
While swine manure continues to be effective for ameliorating soil acidity, crop straw amendment has also shown a good potential to ameliorate the acidity of the red soil. Thus, after harvest, straws should preferably not be removed from the field, but mixed with the soil to decelerate acidification. The long-term effect of straw return on soil acidity management warrants further determination under field conditions.14.
Nitrogen transformation rates and N<Subscript>2</Subscript>O producing pathways in two pasture soils
Ting Lan Helen Suter Rui Liu Xuesong Gao Deli Chen 《Journal of Soils and Sediments》2018,18(9):2970-2979
Purpose
Better understanding of N transformations and the regulation of N2O-related N transformation processes in pasture soil contributes significantly to N fertilizer management and development of targeted mitigation strategies.Materials and methods
15N tracer technique combined with acetylene (C2H2) method was used to measure gross N transformation rates and to distinguish pathways of N2O production in two Australian pasture soils. The soils were collected from Glenormiston (GN) and Terang (TR), Victoria, Australia, and incubated at a soil moisture content of 60% water-filled pore space (WFPS) and at temperature of 20 °C.Results and discussion
Two tested pasture soils were characterized by high mineralization and immobilization turnover. The average gross N nitrification rate (ntot) was 7.28 mg N kg?1 day?1 in TR soil () and 5.79 mg N kg?1 day?1 in GN soil. Heterotrophic nitrification rates (nh), which accounting for 50.8 and 41.9% of ntot, and 23.4 and 30.1% of N2O emissions in GN and TR soils, respectively, played a role similar with autotrophic nitrification in total nitrification and N2O emission. Denitrification rates in two pasture soils were as low as 0.003–0.004 mg N kg?1 day?1 under selected conditions but contributed more than 30% of N2O emissions.Conclusions
Results demonstrated that two tested pasture soils were characterized by fast N transformation rates of mineralization, immobilization, and nitrification. Heterotrophic nitrification could be an important NO3?–N production transformation process in studied pasture soils. Except for autotrophic nitrification, roles of heterotrophic nitrification and denitrification in N2O emission in two pasture soils should be considered when developing mitigation strategies.15.
Yasser Mahmoud Awad Sang Soo Lee Yong Sik Ok Yakov Kuzyakov 《Journal of Soils and Sediments》2017,17(3):611-620
Purpose
Various soil conditioners, such as biochar (BC) and anionic polyacrylamide (PAM), improve soil fertility and susceptibility to erosion, and may alter microbial accessibility and decomposition of soil organic matter (SOM) and plant residues. To date, no attempts have been made to study the effects of BC in combination with PAM on the decomposition of soil SOM and plant residues. The objective of this study was to evaluate the effects of BC, PAM, and their combination on the decomposition of SOM and alfalfa residues.Materials and methods
An 80-day incubation experiment was carried out to investigate the effects of oak wood biochar (BC; 10 Mg ha?1), PAM (80 kg ha?1), and their combination (BC?+?PAM) on decomposition of SOM and 14C-labeled alfalfa (Medicago sativa L.) residues by measuring CO2 efflux, microbial biomass, and specific respiration activity.Results and discussion
No conditioner exerted a significant effect on SOM decomposition over the 80 days of incubation. PAM increased cumulative CO2 efflux at 55–80 days of incubation on average of 6.7 % compared to the soil with plant residue. This was confirmed by the increased MBN and MB14C at 80 days of incubation in PAM-treated soil with plant residue compared to the control. In contrast, BC and BC?+?PAM decreased plant residue decomposition compared to that in PAM-treated soil and the respective control soil during the 80 days. BC and BC?+?PAM decreased MBC in soil at 2 days of incubation indicated that BC suppressed soil microorganisms and, therefore, decreased the decomposition of plant residue.Conclusions
The addition of oak wood BC alone or in combination with PAM to soil decreased the decomposition of plant residue.16.
Purpose
Forest soil respiration is an important component of global carbon budgets, but its spatial variation is inadequately understood. This research aimed to measure soil respiration (R s), soil water content (M s-5), soil temperature (T), and carbon dioxide (M co2) in a coastal protection forest (CPF), which is one kind of man-made forests designed for coastal protection primarily along the coast in China, to determine the relationships among them, and to analyze their spatial distributions in a small scale.Materials and methods
We measured R s, M s-5, T, and M co2 of 100 plots in an approximately flat grid (totally 4 hm2) by LI-8100A in a Casuarina equisetifolia L. forest on a state-owned forest farm of 326 hm2 in SE China. Traditional statistics and geo-statistics including semivariance, Moran’s I index, and fractal dimension were used to analyze data.Results and discussion
Key findings were that (1) the spatial mean of R s, M s-5, T, and M co2 were 1.194 μmol m?2 s?1, 11.387 mmol mol?1, 14.153 °C, and 407.716 ppm, respectively, in the forest; (2) the relationship between soil respiration and the other three factors was weak, while M s-5, T, and M co2 have strong relationships with each other; and (3) the four factors, especially soil respiration, had strong autocorrelation within given limits and showed great heterogeneity with 95 % confidence intervals around the means in the study area, all of which can provide important value for the study of carbon cycling and for the sustainable management of coastal protection forests.Conclusions
According to geo-statistical analysis and field investigations, soil respiration in the coastal forest is less than in some broad-leaf forests but higher than in some conifers. Strong heterogeneity and autocorrelation are clear; however, its relation with other three factors is weak. CPF is a considerable potential forest for carbon conservation if it is well managed.17.
Jun Cui Jingjing Wang Jun Xu Chonghua Xu Xiaoniu Xu 《Journal of Soils and Sediments》2017,17(8):2156-2164
Purpose
Evergreen broad-leaved forest ecosystems are common in east China, where they are both ecologically and economically important. However, nitrogen (N) addition over many years has had a detrimental effect on these ecosystems. The objective of this research was to evaluate the effect of 4 years of N addition on microbial communities in an evergreen broad-leaved forest in southern Anhui, China.Materials and methods
Allochthonous N in the form of aqueous NH4NO3 and phosphorus (P) in the form of Ca(H2PO4)2·H2O were applied at three doses with a control (CK, stream water only without fertilizer): low-N (50 kg N ha?1 year?1), high-N (100 kg N ha?1 year?1) and high-N+P (100 kg N ha?1 year?1 + 50 kg P ha?1 year?1). Quantitative PCR analysis of microbial community size and Illumina platform-based sequencing analysis of the V3-V4 16S rRNA gene region were performed to characterize soil bacterial community abundance, structure, and diversity.Results and discussion
Bacterial diversity was increased in low-N and high-N treatments and decreased in the high-N+P treatment, but α-diversity indices were not significantly affected by N additions. Proteobacteria, Acidobacteria, and Actinobacteria were the predominant phyla in all treatments, and the relative abundance of different genera varied among treatments. Only soil pH (P = 0.051) showed a weak correlation with the bacterial community in CK and low-N treatment.Conclusions
The composition of the bacterial community and the abundance of different phyla were significantly altered by N addition. The results of the present study indicate that soil bacterial communities in subtropical evergreen broad-leaved forest are, to a certain extent, resilient to changes derived from N additions.18.
Xiaodong Zhang Zhaoliang Song Kim McGrouther Jianwu Li Zimin Li Ning Ru Hailong Wang 《Journal of Soils and Sediments》2016,16(2):461-466
Purpose
Occlusion of carbon in phytoliths is an important biogeochemical carbon sequestration mechanism and plays a significant role in the global biogeochemical carbon cycle and atmospheric carbon dioxide (CO2) concentration regulation at a millennial scale. However, few studies have focused on the storage of phytolith and phytolith-occluded carbon (PhytOC) in subtropical forest soils.Materials and methods
Soil profiles with 100-cm depth were sampled from subtropical bamboo forest, fir forest, and chestnut forest in China to investigate the variation of phytoliths and PhytOC storage in the soil profiles based on amass-balance assessment.Results and discussion
The storage of phytoliths in the top 100 cm of the bamboo forest soil (198.13?±?25.08 t ha?1) was much higher than that in the fir forest (146.76?±?4.53 t ha?1) and chestnut forest (170.87?±?9.59 t ha?1). Similarly, the storage of PhytOC in the bamboo forest soil (3.91?±?0.64 t ha?1) was much higher than that in the fir forest soil (1.18?±?0.22 t ha?1) and chestnut forest soil (2.67?±?0.23 t ha?1). The PhytOC percentage in the soil organic carbon pool increased with soil depth and was the highest (4.29 %) in the bamboo forest soil. Our study demonstrated that PhytOC in soil was significantly influenced by forest type and the bamboo forest ecosystem contributed more significantly to phytolith carbon sequestration than other forest ecosystems.Conclusions
Different forest types have a significant influence on the soil PhytOC storage. Optimization of bamboo afforestation/reforestation in future forest management plans may significantly enhance the biogeochemical carbon sink in the following centuries.19.
Fuxia Pan Stephen James Chapman Yaying Li Huaiying Yao 《Journal of Soils and Sediments》2017,17(10):2428-2437
Purpose
Organic matter amendment is usually used to improve soil physicochemical properties and to sequester carbon for counteracting climate change. There is no doubt that such amendment will change microbial activity and soil nitrogen transformation processes. However, the effects of straw and biochar amendment on anammox and denitrification activity and on community structure in paddy soil are unclear.Materials and methods
We conducted a 30-day pot experiment using rice straw and rice straw biochar to deepen our understanding about the activity, microbial abundance, and community structure associated with soil nitrogen cycling during rice growth.Results and discussion
Regarding activity, anammox contributed 3.1–8.1% of N2 production and denitrification contributed 91.9–96.9% of N2 production; straw amendment resulted in the highest denitrification rate (38.9 nmol N g?1 h?1), while biochar amendment resulted in the highest anammox rate (1.60 nmol N g?1 h?1). Both straw and biochar amendments significantly increased the hzsB and nosZ gene abundance (p < 0.05). Straw amendment showed the highest nosZ gene abundance, while biochar amendment showed the highest hzsB gene abundance. Phylogenetic analysis of the anammox bacteria 16S rRNA genes indicated that Candidatus Brocadia and Kuenenia were the dominant genera detected in all treatments.Conclusions
Straw and biochar amendments have different influences on anaerobic ammonia oxidation and denitrification within paddy soil. Our results suggested that the changes in denitrification and anammox rates in the biochar and straw treatments were mainly linked to functional gene abundance rather than microbial community structure and that denitrification played the more major role in N2 production in paddy soil.20.
Bangliang Deng Zhenzhen Li Ling Zhang Yingchao Ma Zhi Li Wenyuan Zhang Xiaomin Guo Dekui Niu Evan Siemann 《Journal of Soils and Sediments》2016,16(3):777-784