Influence of mixtures of acenaphthylene and benzo[a]anthracene on their degradation by Pleurotus ostreatus in sandy soil

Purpose

Polycyclic aromatic hydrocarbons (PAHs) are a class of organic compounds commonly found as soil contaminants. Fungal degradation is considered as an environmentally friendly and cost-effective approach to remove PAHs from soil. Acenaphthylene (Ace) and Benzo[a]anthracene (BaA) are two PAHs that can coexist in soils; however, the influence of the presence of each other on their biodegradation has not been studied. The biodegradation of Ace and BaA, alone and in mixtures, by the white rot fungus Pleurotus ostreatus was studied in a sandy soil.

Materials and methods

Experimental microcosms containing soil spiked with different concentrations of Ace and BaA were inoculated with P. ostreatus. Initial (t ₀) and final (after 15 days of incubation) soil concentrations of Ace and BaA were determined after extraction of the PAHs.

Results and discussion

P. ostreatus was able to degrade 57.7% of the Ace in soil spiked at 30 mg kg^?1 dry soil and 65.8% of Ace in soil spiked at 60 mg kg^?1 dry soil. The degradation efficiency of BaA by P. ostreatus was 86.7 and 77.4% in soil spiked with Ace at 30 and 60 mg kg^?1 dry soil, respectively. After 15 days of incubation, there were no significant differences in Ace concentration between soil spiked with Ace and soil spiked with Ace + BaA, irrespective of the initial soil concentration of both PAHs. There were also no differences in BaA concentration between soil spiked with BaA and soil spiked with BaA + Ace.

Conclusions

The results indicate that the fungal degradation of Ace and BaA was not influenced by the presence of each other’s PAH in sandy soil. Bioremediation of soils contaminated with Ace and BaA using P. ostreatus is a promising approach to eliminate these PAHs from the environment.     

Phosphorus fractions in poultry litter as affected by flue‐gas desulphurization gypsum and litter stacking

Previous research has shown that the addition of flue‐gas desulphurization (FGD) gypsum to poultry litter decreases water‐soluble P. No information is currently available, however, on extractable P fractions in poultry litter and P availability as affected by gypsum. The first objective of this work was to evaluate the effect of incubation time and rate of gypsum addition to litter alone or litter mixed with soil on total P and inorganic P in sequential extracts of H₂O, 0.5 m NaHCO₃, 0.1 m NaOH and 1 m HCl. Poultry litter was mixed with 25, 50, or 75% gypsum (by weight) and incubated alone or mixed with soil for 63–93 days at 25 °C, with periodic sequential extractions. For litter alone or litter mixed with soil, adding gypsum decreased total P and inorganic P in the H₂O fraction and increased both P forms in the NaHCO₃ fraction. These changes did not affect plant P availability as measured by Mehlich‐1 P. Increasing incubation time decreased total P and inorganic P in the H₂O fraction of litter alone or litter mixed with soil, which was apparently caused by P immobilization by fungi. A second objective of this study was to evaluate P in the H₂O and NaHCO₃ fractions of litter as affected by stacking time and depth. Litter was stacked to a height of 1.2 m with samples taken immediately after stacking and 31 days later to be sequentially extracted for total P and inorganic P. Stacking time did not affect P in the H₂O fraction, but it increased P in the NaHCO₃ fraction by 25%. These results suggest that stacking poultry litter may increase the amount of labile P.     

Application of ionic liquids for the extraction and passive sampling of endocrine-disrupting chemicals from sediments

Purpose

The aim of this study was to assess the applicability of ionic liquids (ILs) in the extraction of organic contaminants from sediments and in passive sampling as a receiving phase material.

Materials and methods

Solutions of two water-soluble ionic liquids (WSILs)—1-butyl-3-methyl imidazolium tetrafluoroborate ([BMIm]BF₄) and N-butyl-3-methyl pyridinium tetrafluoroborate ([BMPy]BF₄)—were used for the extraction of endocrine-disrupting chemicals (EDCs), including bisphenol A (BPA), 17β-estradiol (E2), and nonylphenol (NP), from different sediments. Furthermore, a hydrophobic IL (1-hexadecyl-3-methyl imidazolium hexafluorophosphate) was filled in a polyethylene (PE) membrane tubing to build an IL-PE passive sampler for sediment pore water. Uptake kinetics were studied by exposing samplers to sediments artificially contaminated by EDCs and identified by exposing samplers to field-contaminated sediments.

Results and discussion

EDCs were efficiently extracted by WSIL solutions from the two artificially contaminated sediments, with maximum extraction efficiencies of 84.2–104.6 % by the [BMIm]BF₄ solution and 74.9–103.7 % by the [BMPy]BF₄ solution. However, WSIL solutions are not suitable for EDC extraction from sediment with very low organic carbon contents. EDCs in sediment pore water can be efficiently taken up by the IL-PE sampler, with uptake rate constants of 2.08?×?10^?2?l?g^?1?day^?1 (BPA), 5.74?×?10^?2?l?g^?1?day^?1 (E2), and 2.10 l?g^?1?day^?1(NP).

Conclusion

BPA, E2, and NP can be extracted efficiently by IL water solution from most of the artificially and field-contaminated sediments used in this study. The IL ([HDMIm]PF₆)-PE passive sampler can be used to monitor EDCs in the pore water of sediments. A good match between the calculated and measured concentrations of BPA and E2 in pore water of field-contaminated sediments was observed.     

Changes in Soluble Manganese and Iron Concentrations of Tropical Wetland Soils as Influenced by Glyphosate Dosage

Glyphosate is largely used to control weeds in wetland soils of Brazil. We investigated changes in the chemistry of soluble manganese (Mn) and iron (Fe) in these soils as affected by glyphosate dosage. Triplicate samples of the A horizon of wetland soils with different organic-matter contents were incubated with deionized water (1:2) for 1, 3, and 30 days under flooding. Three different glyphosate doses (0, 0.048, and 0.096 g L^?1 m^?2) were spiked on the flooded water at the beginning of the incubation periods. After incubation, pH was measured and samples of the supernatant were collected for determination of Mn/Fe concentrations by atomic absorption. Glyphosate application impacted Mn but had no effect on pH and Fe. Soluble Mn concentrations decreased as glyphosate dosage increased for the high organic-matter soil after 3 days of incubation. It indicated that glyphosate application can change the chemistry of soil metals. The intensity of these changes depends on the glyphosate dosage, evolved metal, incubation time, and soil properties.     

Carbon sequestration in a temperate grassland; management and climatic controls

Soil management practices that result in increased soil carbon (C) sequestration can make a valuable contribution to reducing the increase in atmospheric CO₂ concentrations. We studied the effect of poultry manure, cattle slurry, sewage sludge, NH₄NO₃ or urea on C cycling and sequestration in silage grass production. Soil respiration, net ecosystem exchange (NEE) and methane (CH₄) fluxes were measured with chambers, and soil samples were analysed for total C and dissolved organic C (DOC). Treatments were applied over 2 years and measurements were carried out over 3 years to assess possible residual effects. Organic fertilizer applications increased CO₂ loss through soil respiration but also enhanced soil C storage compared with mineral fertilizer. Cumulative soil respiration rates were highest in poultry manure treatments with 13.7 t C ha^?1 in 2003, corresponding to 1.6 times the control value, but no residual effect was seen. Soil respiration showed an exponential increase with temperature, and a bimodal relationship with soil moisture. The greatest NEE was observed on urea treatments (with a CO₂ uptake of ?4.4 g CO₂ m^?2 h^?1). Total C and DOC were significantly greater in manure treatments in the soil surface (0–10 cm). Of the C added in the manures, 27% of that in the sewage pellets, 32% of that in the cattle slurry and 39% of that in the poultry manure remained in the 0–10 cm soil layer at the end of the experiment. Mineral fertilizer treatments had only small C sequestration rates, although uncertainties were high. Expressed as global warming potentials, the benefits of increased C sequestration on poultry manure and sewage pellet treatments were outweighed by the additional losses of N₂O, particularly in the wet year 2002. Methane was emitted only for 2–3 days on cattle slurry treatments, but the magnitudes of fluxes were negligible compared with C losses by soil respiration.     

Comparison of biological and chemical methods to predict nitrogen mineralization in animal wastes

Summary Biological and chemical methods to predict the level of plant-available N in animal manure were investigated under laboratory and growth-chamber conditions. Two biological methods (maize cultivation in pots and incubation of soil-waste mixtures) and four chemical methods (N extraction by autoclaving, 0.5 N KMnO₄, pepsin, and 6 N HCl) were compared for their accuracy in determining the availability of N in 10 samples of animal manure applied to soil. The autoclaving, permanganate, and pepsin methods were able to predict N availability in this group of wastes. Total N mineralized in a soil amended with different samples of animal manure ranged from 0 to 311 mg N kg^-1 soil. Expressed as a percentage of organic N added to the soil, mineralized N range from 0 to 39%. The poultry manure samples gave higher mineralization rates than the other types of manure tested. In general, mineralized N became immobilized during the incubation process, except for the second poultry manure sample, which showed an initially rapid then a a slow release of mineral N, and pig manure sample 2, which showed a slow initial rate, followed by a rapid increase, and then a slow rate of N release. The first-order exponential model used was able to describe the pattern of N mineralization in pig manure sample 2, poultry manure sample 2 but not the other samples.     

An anion resin membrane technique to overcome detection limits of isotopically exchanged P in P-sorbing soils

Isotopically exchanged phosphorus is difficult to determine in soils that strongly sorb P (so that there is little P in solution) and in soils with large concentrations of colloidal P in soil suspensions. A method is proposed in which anion exchange membranes (AEM) are added to the soil suspension after an initial period of isotopic exchange with ³²P‐labelled phosphate ions. Isotopically exchanged P, termed E_AEM, is calculated from the ratio of labelled phosphate ions to the total phosphate ions on the membrane. The E_AEM was compared with the E value measured in an aqueous soil extract (E_{Water extract}) for 14 soils with different degrees of P sorption. The two methods gave similar results in soils with large P concentrations in an aqueous soil extract. However, E_{Water extract} values significantly exceeded the E_AEM values by up to 18‐fold when soluble P was near the determination limit (0.008 mg P l^?1). In a second experiment, two Ferralsols received further P from inorganic and plant sources and were incubated for 7 days. Treatment effects on labile P were erroneous as detected by the E_{Water extract} but were significant as detected with the AEM method. Third, E_AEM values were followed in a Lixisol and a Ferralsol which received labelled phosphate ions with carrier just before the beginning of a 23‐day incubation. The approximate recovery of added inorganic P in the E_AEM value suggested that this method adequately samples labile P in P‐sorbing soils. All these results showed that errors in the determination of E values for soils with very small concentrations of P in the soil solution are reduced using the proposed method.     

Short-term N availability in response to dissolved-organic-carbon from poultry manure, alone or in combination with cellulose

 Short-term changes in N availability in a sandy soil in response to the dissolved organic carbon (DOC) from a poultry manure (application rate equivalent to approximately 250 kg N ha^–1) were evaluated in a 44-day aerobic incubation experiment. The treatments included poultry manure alone and two treatments in which an extra source of C, of low water solubility, was added with the poultry manure in the form of a low (1.05 g kg^–1) and a high (4.22 g kg^–1) amount of cellulose. All treatments were fertilised with the equivalent of 60 kg N ha^–1 of (¹⁵NH₄)₂SO₄ in solution. A control treatment consisted of sieved field-moist soil plus 60 kg N ha^–1 of (¹⁵NH₄)₂SO₄ in solution. Measurements were made of N₂O and CO₂ emissions, inorganic N, DOC, biomass N, biomass C and labelled N contained in the inorganic N and biomass N pools. The dynamics of N turnover in this study were driven mainly by processes of mineralisation–immobilisation with little significant loss of N by volatilisation or denitrification. The DOC supplied with the poultry manure played a more important role in N₂O emissions than differences in C/N ratio. Changes in DOC and cumulative CO₂-C production during the first 11 days were also highly correlated (R ²=0.88–0.66, P<0.01). An initial net immobilisation of N, with significant increases in biomass C and biomass N (P<0.05) for all treatments over the control at day 11, indicated a high availability of C from the DOC fraction. The presence of additional C from the applied cellulose did not enable a massive N immobilisation. Total inorganic N and unlabelled inorganic N concentrations were highest in soils treated with poultry manure alone (P<0.05), indicating that an active gross mineralisation of the added poultry manure and a possible positive priming effect were taking place during the incubation. Received: 29 May 1998     

Oxygen inhibition of acetylene reduction (nitrogen fixation) in soil: Effect of glucose and oxygen concentrations

Sandy loam soil was amended with different concentrations of glucose and was incubated at different pO₂ levels. Under many conditions of incubation time and treatment, N₂ ase activity as determined by 1-h aerobic C₂H₂ reduction assay (flushed with Ar:O₂, 4:1 before assay) was significantly less than that determined by means of ambient assay (carried out at the pO₂ of incubation without flushing with Ar:O₂, 4:1 before assay). The difference between the N₂ase activity in aerobic assay and that in ambient assay increased with decreasing glucose and O₂ concentrations imposed during incubation. The inhition in aerobic assays was analogous to O₂-induced shut-off of N₂ase and amounted to 75 per cent inhibition after incubation at 0.06 atm pO₂ of samples amended with 0.75% glucose (w/w). Similar O₂ inhibition was observed after amendment with mannitol and with lactate. Times of incubation were chosen such that development of anaerobic N₂ase activity was either absent or too low to account for the observed effects of O₂ during assay. It was shown that 0.05 atm pC₂H₂ was adequate for routine 1-h assays of the soil system employed. Individual soil samples could be subjected to repeated 1-h assays (with removal of C₂H₂ and C₂H₄ by evacuation after each assay) thus avoiding side-effects of long exposure to C₂H₂.     

培养温度和时间对磷肥在黑土中转化的影响

采用室内培养试验研究了培养温度和时间对磷酸二氢钙(MCP)、磷酸二氢铵(MAP)和磷酸氢二铵(DAP)在黑土中转化的影响。结果表明:温度升高增加了黑土对肥料磷的固定,且有利于Al-P的形成;培养50 d后,温度由5℃升至25℃时,We-P在添加MAP和MCP处理的土壤中占外源磷的比例分别降低51%和42%,同时Al-P分别上升110%和45%;在培养初期,温度对Ca8-P和Fe-P形成的影响不显著,但随培养时间的延长,差异显著。25℃时,培养时间对Ca2-P和Ca8-P形成的影响较小;Al-P在培养初期形成速率很快,随培养时间的延长,形成速率下降,而Fe-P的形成速率与之相反;Al-P的增加量与We-P的下降量呈显著线性正相关。与MAP和MCP相比,DAP更适合在黑土中施用。     

The liming effect of five organic manures when incubated with an acid soil

A laboratory incubation experiment of 6 months duration was carried out to investigate the liming effects of five organic manures (poultry, pig, and cattle manure, soybean residues, and sewage sludge) when added to an acid soil at a rate of 10 mg g^–1. Soils were sampled after 1, 7, 13, 19, and 25 weeks of incubation. For the animal manures and sewage sludge, soil pH was highest after 1 week incubation and it declined thereafter. However, for soybean residues, pH increased over the first 7 weeks of incubation after which it declined. The decreases in pH were accompanied by accumulation of NO ‐N in the soil. The addition of organic residues to the soil resulted in decreases in the concentrations of exchangeable Al and in both total (Al_t) and monomeric (Al_mono) Al present in the soil solution. The effect was most marked for poultry manure, least marked for cattle manure, and more evident after 7 than 25 weeks incubation. Concentrations of soluble C in the soil solution were elevated in manure‐amended soils. Manure additions resulted in a decrease in the percentage of Al_t present in solution as Al_mono, and this was attributed to complexation of Al by soluble organic matter originating from the manures. It was concluded that organic wastes can act as liming materials when added to acid soils and that the resulting increase in pH and decrease in Al_mono concentrations might provide a window of opportunity for establishment and early growth of crop plants.     

Impact of Soil Type and Application Rate on the Availability of P Applied as Alum‐Treated Poultry Litter

The purpose of this laboratory incubation study was to assess the solubility of phosphorus (P) in alum‐treated poultry litter (ATPL) when applied to three Virginia soils at equivalent P‐based rates. Three poultry litter sources (one that had received no alum additions and two that had received alum additions) were utilized in the study. These litter sources and monopotassium phosphate (KH₂PO₄) were applied at rates of 66, 132, and 197 mg P kg^?1 with a 0‐P check treatment included for each soil. Soils were incubated for 1 year, and samples were collected at 1, 3, 6, and 12 months after treatment application. Data collected were used to calculate the relative extractability of P applied in the three litter sources. Results indicated that ATPL applications reduced P solubility compared to untreated poultry litter (NPL); this effect was most significant at 1 month after application. However, at 12 months, significant differences in extractable P between NPL and ATPL treatments were limited at the 66 mg P kg^?1 rate. This resulted from continuous decline in the extractability of P applied in the NPL, whereas the extractability of P applied in the ATPL source changed little with time and in some cases increased slightly between the 1‐ and 3‐month sampling periods. Calculated values of relative extractability were influenced not only by litter source but also P application rate, soil type, and incubation time. Therefore, use of relative extractability values as P source coefficients should be done with caution, because experimental protocol can have profound effects on their magnitude.     

Formation and distribution of methylmercury in sediments at a mariculture site: a mesocosm study

Purpose

The aim of the present study was to investigate the differences of methylmercury (MeHg) formation and distribution between mariculture (aquaculture) sediments (MS) and reference sediments (RS) collected from a site in Hong Kong.

Materials and methods

The MS and RS samples were split into four batches, three of which were spiked with HgCl₂ aqueous solution to a concentration of 0.8, ,2 and 8 mg k g^?1 in sediment samples SP1, SP2, and SP3, respectively, while the rest served as a control batch (referred to as C).

Results and discussion

The results showed that the highly Hg-polluted sediment produced greater amounts of MeHg. During the culture period, MeHg concentrations in sediments decreased over time. The decreasing percentage increased in the order of SP3?<?SP2?<?SP1, which might be due to the inhibition of MeHg degradation by high Hg concentrations. The mean value of MeHg concentrations and %MeHg of the total Hg (THg) in MS was significantly lower than those in RS, possibly due to the complexation of Hg with organic ligands, leading to lower Hg bioavailability for methylation bacteria. The distribution coefficient of THg (K_dT) was relatively high in MS compared to RS, indicating that the former had a greater number of binding sites for Hg adsorption.

Conclusions

Methylmercury formation was inhibited in MS, probably due to increased complexation of Hg²⁺ with organic matter and adsorption of Hg to MS. Furthermore, the mean value of K_dT in MS was relatively high when compared to RS, which illustrates that MS sediments have more binding sites than RS for adsorption of Hg.     

Zinc toxicity on N2O reduction declines with time in laboratory spiked soils and is undetectable in field contaminated soils

Denitrification assays in soils spiked with zinc salt have shown inhibition of the N₂O reduction resulting in increased soil N₂O fluxes with increasing soil Zn concentration. It is unclear if the same is true for environmentally contaminated soils. Net production of N₂O and N₂ was monitored during anaerobic incubations (25 °C, He atmosphere) of soils freshly spiked with ZnCl₂ and of corresponding soils that were gradually enriched with metals (mainly Zn) in the field by previous sludge amendments or by corrosion of galvanized structures. Total denitrification activity (i.e. the sum of N₂O+N₂ production rate) was not inhibited by freshly added Zn salts up to 1600 mg Zn kg⁻¹, whereas N₂O reduction decreased by 50% (EC₅₀) at total Zn concentrations of 231 mg Zn kg⁻¹ (ZEV soil) and 368 mg Zn kg⁻¹ (TM soil). In contrast, N₂O reduction was not reduced by soil Zn in any of the field contaminated soils, even at total soil Zn or soil solution Zn concentrations exceeding more than 5 times corresponding EC₅₀'s of the freshly spiked soil. The absence of adverse effects in the field contaminated soils was unrelated to soil NO₃ or organic matter concentration. Ageing (2-8 weeks) and soil leaching after spiking reduced the toxicity of Zn on N₂O reduction, either expressed as total Zn or soil solution Zn, suggesting adaptation reactions. However, no full recovery after spiking was identified at the largest incubation period in one soil. In addition, the denitrification assay performed with sewage sludge showed elevated N₂O release in Zn contaminated sludges (>6000 mg Zn kg⁻¹ dry matter) whereas this was not observed in low Zn sludge (<1000 mg Zn kg⁻¹ dry matter) suggesting limits to adaptation reactions in the sludge particles. It is concluded that the use of soils spiked with Zn salts overestimates effects on N₂O reduction. Field data on N₂O fluxes in sludge amended soils are required to identify if metals indeed promote N₂O emissions in sludge amended soils.     

Carbon and Nitrogen Mineralization and Humus Composition Following Municipal Solid Waste Compost Addition to Laterite Soils under Continuous Cassava Cultivation

A glasshouse incubation experiment was conducted to study the carbon (C) and nitrogen (N) mineralization of municipal solid waste compost (MSWC) added at differential rates to a laterite soil where cassava has been continuously cultivated for the past 10 years. The rate of C mineralization from added substrates increased with increasing rates of addition of MSWC. Available N significantly increased with increase in the rate of application of MSWC. There was a decreasing trend in E₄₆₅/E₆₆₅ ratio of humic acid as we increased the rate of application of MSWC from 2.5 to 20 t ha^?1. The Cross Polarization Magic Angle Spinning (CPMAS) ¹³C NMR spectral analysis revealed that there are differences in the rate of humification of added MSWC, and application of MSWC at 15 t ha^?1 resulted in least humification with the greatest alkyl C, lowest aromatic C, and greater O-alkyl C content. The decomposition rate (R) was found to be greater for this treatment. The residual C in soil was found to increase over time coincident with greater rates of MSWC application, indicating increased C stabilization, which could improve soil quality.     

Methods for estimating temperature sensitivity of soil organic matter based on incubation data: A comparative evaluation

Although the temperature sensitivity (Q₁₀) of soil organic matter (SOM) decomposition has been widely studied, the estimate substantially depends on the methods used with specific assumptions. Here we compared several commonly used methods (i.e., one-pool (1P) model, two-discrete-pool (2P) model, three-discrete-pool (3P) model, and time-for-substrate (T4S) Q₁₀ method) plus a new and more process-oriented approach for estimating Q₁₀ of SOM decomposition from laboratory incubation data to evaluate the influences of the different methods and assumptions on Q₁₀ estimation. The process-oriented approach is a three-transfer-pool (3PX) model that resembles the decomposition sub-model commonly used in Earth system models. The temperature sensitivity and other parameters in the models were estimated from the cumulative CO₂ emission using the Bayesian Markov Chain Monte Carlo (MCMC) technique. The estimated Q₁₀s generally increased with the soil recalcitrance, but decreased with the incubation temperature increase. Our results indicated that the 1P model did not adequately simulate the dynamics of SOM decomposition and thus was not adequate for the Q₁₀ estimation. All the multi-pool models fitted the soil incubation data well. The Akaike information criterion (AIC) analysis suggested that the 2P model is the most parsimonious. As the incubation progressed, Q₁₀ estimated by the 3PX model was smaller than those by the 2P and 3P models because the continuous C transfers from the slow and passive pools to the active pool were included in the 3PX model. Although the T4S method could estimate the Q₁₀ of labile carbon appropriately, our analyses showed that it overestimated that of recalcitrant SOM. The similar structure of 3PX model with the decomposition sub-model of Earth system models provides a possible approach, via the data assimilation techniques, to incorporate results from numerous incubation experiments into Earth system models.     

Inoculation with N2-generating denitrifier strains mitigates N2O emission from agricultural soil fertilized with poultry manure

Pelleted poultry manure is recommended for use with agricultural soil as a replacement for chemical fertilizers; however, application of the manure stimulates nitrous oxide (N₂O) emission from the soil through denitrification. To mitigate the N₂O emission caused by application of pelleted poultry manure, soil microcosms were set up; each microcosm was inoculated with one of the following N₂-generating denitrifier strains previously been isolated from paddy soil: Azoarcus, Dyella, Dechloromonas, Niastella, and Burkholderia. When pelleted poultry manure was incubated on its own, N₂O was produced by denitrification. In contrast, N₂O emission was significantly lowered when the manure was inoculated with most of the N₂-generating strains. In soil microcosms, N₂O was emitted during incubation after application of the pelleted manure, while N₂O flux was significantly lowered when the soil was inoculated with Azoarcus sp. KS11B, Niastella sp. KS31B, or Burkholderia sp. TSO47-3 on the 12th day of incubation. In addition, when pelleted manure was inoculated with the strains prior to application in the soil microcosms, the level of N₂O emission was significantly lowered to ca. 40–60 % that from the non-inoculated control. Our study provides the prototype of a technique that uses microbial technology to mitigate N₂O emission from agricultural soil fertilized with pelleted poultry manure.     

Observation of specific ion effects in humus aggregation process

Specific ion effects play a vital role in a variety of colloidal and interfacial processes. However, few studies have reported the specific ion effects in the humus aggregation process, which strongly influence the transport and fate of environmental pollutants. In this study, soil humus colloids were prepared and characterized, and the specific ion effects on humus aggregation in electrolyte solutions were investigated at a variety of concentrations and p H values using dynamic light scattering methods. Activation energy(?E), which is known to reflect the dynamics and stability of a colloidal system, was used to quantitatively characterize the specific ion effects. The results showed that given ?E value of 2.48 × 10~3 J mol~(-1) at p H 3.0, the electrolyte concentrations were 91.6, 58.2, 3.8, and 0.8 mmol L~(-1) for Na~+, K~+, Mg~(2+), and Ca~(2+), respectively, thus indicating significant specific ion effects in the humus aggregation process. Most importantly, decreasing the electrolyte concentrations increased the differences in the ?E value between two cation species with the same valence(i.e., ?EN_a-?E_K and ?E_(Mg)-?E_(Ca)), while increasing the p H increased the magnitude of ?E_(Mg)-?E_(Ca). However, the classic Derjaguin,Landau, Verwey, and Overbeek(DLVO) theory and the double layer theory, as well as the currently widely used ionic hydration and dispersion effects, failed to predict the experimentally observed increase in the specific ion effects with decreasing electrolyte concentrations in a quantitative sense. These results have implications for the necessity of involving specific ion effects for a better understanding of humus aggregation and interactions in aqueous and soil systems.     

Impacts of biochar and processed poultry manure,applied to a calcareous soil,on the growth of bean and maize

Direct use of poultry manure on agricultural lands may cause environmental concerns, so there is a need to establish the suitability of the application of biochar derived from poultry manure for calcareous soil chemical properties and plant growth. The purpose of this study was to evaluate the effects of processed poultry manure (0, 5, 10 and 20 g/kg) and its biochar (0, 2.5, 5, 10 and 20 g/kg) on soil chemical properties of a calcareous soil and growth of bean (Phaseolus vulgaris) and maize (Zea mays) plants. In the incubation experiment, both processed poultry manure (PPM) and biochar decreased pH and the concentration of plant‐available Fe of soil but increased plant‐available P, Zn, Cu and Mn concentrations. PPM and biochar increased the concentrations of exchangeable cations (K, Ca and Mg) in soil. PPM and biochar applications increased the growth of maize and bean plants. PPM and biochar resulted in increased concentrations of N, P, K, Ca, Fe, Zn, Cu and Mn in bean plants. In maize plants, PPM and biochar applications increased the N, P, K, Zn, Cu and Mn but decreased the Ca and Mg concentrations. Results of this study reveal that poultry manure biochar can be used effectively for agricultural purposes.     

Respiratory quotients and Q10 of soil respiration in sub-alpine Australia reflect influences of vegetation types

Identifying and quantifying attributes that help predict rates of heterotrophic soil respiration is a key issue. Similarly, assessing the temperature sensitivity (Q₁₀) of soil C is critical to establishing if increases in Mean Annual Temperature will serve to further increase atmospheric CO₂. Using organic soils from three sub-alpine communities that differ significantly in structure, species composition and productivity, we measured the respiratory quotient (RQ = rates of CO₂ efflux/rates of O₂ uptake) and temperature sensitivity of heterotrophic respiration during long-term (120 days) incubation. As a directly measurable parameter, RQ is free of empirical assumptions and provides an additional tool that can be used in conjunction with constants derived from fitted Arrhenius or exponential equations, to help understand shifts in microbial use of C substrates and how changes in vegetation might affect soil processes. Q₁₀ did not change significantly over the course of a 120-day incubation for any of our studied soils. RQs varied with vegetation type and were consistently lower in grassland soils than woodland soils. RQs also varied during long-term incubations and declined consistently with time for grassland soils. RQs declined towards the end of the 120-day incubation for woodland soils. The generally low E_a for these soils from sub-alpine vegetation types in Australia, and the fairly rapid decline in RQ during incubation, suggest the likely greater temperature sensitivity of recalcitrant C relative to labile C could provide a strong positive feedback to increases in Mean Annual Temperature.