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1.
The competitive adsorption of trace elements is a key issue in assessing the mobility of trace elements in calcareous soils and can be affected by disposal of sewage sludge, municipal waste, and poultry manure. The effect of municipal sewage sludge, poultry manure, and municipal waste compost on the sorption of cadmium (Cd), copper (Cu), zinc (Zn), and nickel (Ni) in surface samples of three calcareous soils was studied. As the applied concentrations increased, Cu and Cd adsorption increased, while Zn and Ni adsorption decreased in all treatments. Based on the distribution coefficient (K d) values and proportion of increase or decrease in metal adsorption, the selectivity sequence in control and amended soils found was Cu ≫ Cd ≫ Ni > Zn and Cu ≫ Cd ≫ Zn > Ni, respectively. In general, among control and amended soils, control soils showed the highest K d for Cd, Cu, and Ni, while sludge, poultry manure, and composted waste-amended soils had lowest K d for Cd, Cu, and Ni, respectively. In the case of Zn, composted waste-amended and control soils had highest and lowest K d, respectively. The present experimental results indicated that the addition of organic amendments to these calcareous soils reduced the sorption of Cd, Cu, and Ni. Thus, the effects of preferential adsorption and organic matter should be considered in assessing the risk associated with applying sewage sludge, poultry manure, and composted material to calcareous soils.  相似文献   

2.
Biochar is charcoal made from waste biomass and intended to be added to soil to improve soil function and reduce emissions from the biomass caused by natural degradation to CO2. Nitrogen (N) forms in biochar can be complex and their lability likely to be influenced by pyrolysis temperature which, together with the nature of carbon (C), will influence N mineralisation or immobilisation. These complex relationships are poorly understood, yet impact strongly on the potential agronomic value of biochar. In this study, N in different biochar samples produced from human and animal waste streams (biosolids and cow manure; each mixed with eucalyptus wood chips in a 1:1 dry wt. ratio) at different pyrolysis conditions (highest heating temperature 250, 350, 450 and 550 °C) was extracted with 6 M HCl. The acid hydrolysable, extractable N (THN) was fractionated into ammonia N (AN), amino acid N (AAN), amino sugar N (ASN) and uncharacterisable hydrolysable N (UHN). Biochar samples were also treated with 0.167 M K2Cr2O7 acid to determine N potentially available in the long term. An incubation study of the different biochar samples mixed with acid washed sand was conducted at 32 °C for 81 days to study both C and N turnover. During incubation, the CO2 released was trapped in NaOH and quantified. Hydrolysable N decreased as pyrolysis temperature increased from 250 to 550 °C. Fractionation into AN, AAN, ASN and UHN revealed progressive structural rearrangement of N with pyrolysis temperature. Based on HCl hydrolysis and dichromate oxidation results, C and N in biochar became more stable as pyrolysis temperature increased. The ratio of volatile C to THN was a useful indicator of whether net N mineralisation or immobilisation of N in biochar occurred. THN thus seems a sound estimate of the labile N fraction in biochar in the short term; however, dichromate-oxidisable N is probably more meaningful in the long run. Further studies using different types of biochar need to be conducted under more realistic conditions to obtain more information on N availability in biochar once in soil.  相似文献   

3.
In this study, bentonite (Ben), compost (Com), and biochar (Bio) were used as soil amendments to enhance sandy soil physical properties. A soil column experiment was conducted in a laboratory. Application rates were 3% (weight/weight) of Bio (T1), Ben (T2), and Com (T3). Furthermore, mixtures 1.5% and 1.5% of Bio and Ben (T4), Ben and Com (T5), and Bio and Com (T6), and a mixture 1%, 1%, and 1% of Bio, Ben, and Com (T7) in addition to control treatment were adopted. The mixtures of amendments and sandy soil were concentrated at the top 10 cm of columns. Results revealed that the cumulative evaporation was reduced by 2.3% and 5.7% as a result of using T3 and T5, respectively. However, the remaining treatments enhanced the cumulative evaporation. The application of amendments increased the capacity of the soil to maintain water by 35.4%, 24.4%, 13.3%, and 10.2%, for soils treated with T5, T3, T7, and T4, respectively. The water content at field capacity had the highest increase in the top 10 cm when treatment T3 was used. Although T3 (compost) was the most efficient for enhancing soil physical properties, this study recommends T5 and T7 to improve hydraulic properties of sandy soils. This is due to the fact that biochar and bentonite remain in the soil for a longer period and resist biodegradation while compost overcomes the negative impact of soil chemical properties as a result of biochar and bentonite additions.  相似文献   

4.
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5.
Effect of some additives on synthesis of zeolite from coal fly ash   总被引：3，自引：0，他引：3  
Hydrothermal conversion of fly ash into zeolites was conducted and the effects of the addition of sodium halide and waste solutions produced after zeolitization of fly ash, as well as the adjustment of the Si/Al ratio prior to synthesis process on the formation and cation exchange capacity (CEC) of zeolite product were evaluated. Both the addition of NaCl and NaF ameliorated the crystallinity and CEC of synthesized zeolite, but NaF had a better improvement effect. Na+ was considered to enhance the crystallization of zeolite, while F− favored the dissolution of fly ash. The type of zeolite formed depended on the Si/Al ratio of the starting material prior to the nucleation and crystallization of zeolite. The adjustment of the Si/Al ratio of fly ash by addition of Na2SiO4 and Al(OH)3 changed the type and CEC of zeolite. Waste solutions contained large amount of Si and little Al due to the formation of a zeolite named NaP1 in zeolite terminology with the Joint Committee of Powder Diffraction Standard (JCPDS) code of 39-0219. The alkalinity decreased largely. As a result, the CEC value of zeolite products synthesized with waste solution as alkali source decreased. The supplementation of new alkali to adjust the alkalinity of waste solution could enhance the CEC of synthesized product. It was concluded that: (1) addition of sodium halide and adjustment of the Si/Al ratio prior to synthesis can improve the quality of zeolite; (2) waste solutions produced following the zeolitization of fly ash can be reused as an alkali source in the activation of fly ash; zero-emission of waste solution in the synthesis of zeolite from fly ash is possible.  相似文献   

6.
Biochar has been considered a safe soil additive to enhance soil fertility and agronomic traits of different crops. This study was conducted to explore the impacts of sugarcane waste straw biochar on soil characteristics and some agronomic traits of okra. The experiment was carried out with four treatments, i.e., control, sugarcane waste straw biochar (10 ton ha?1), farmyard manure (FYM, 10 ton ha?1), and chemical fertilizers (NPK; 120:100:80 kg ha?1) having three replications of each treatment. Soil samples were tested for texture, bulk density, particle density, pH, electrical conductivity (EC), organic matter content, nitrate nitrogen (NO3-N), and extractable-P. The sugarcane waste straw biochar was characterized for plant major nutrient elements. The impact of various treatments was observed on soils and agronomic traits of okra like plant height, fruit size, fruit length, and yield of okra. Results revealed that sugarcane waste straw biochar expressed higher EC value and noticeable amounts of nitrogen (N), phosphorus (P), potassium (K), sulfur (S), and magnesium (Mg). The sugarcane waste straw biochar, in comparison with FYM and NPK, significantly improved the NO3-N, extractable-P, OM and EC of the calcareous soil, and reduced the soil bulk density. Furthermore, plant growth and yield parameters were significantly improved under biochar application over the control, FYM and NPK. Overall, sugarcane waste straw biochar proved to be a good alternative to conventional organic and inorganic fertilizers under calcareous soil conditions.  相似文献   

7.
A field study was performed to determine the efficiency of diammonium phosphate (DAP) applied alone or combined with biochar, lignite, and farmyard manure (FYM) on growth and cadmium (Cd) accumulation in wheat and rice. Before crop sowing, different treatments were applied in the field such as a control (T1), DAP alone (0.1%, T2), DAP + lignite (0.05% each, T3), DAP + FYM (0.05% each, T4), and DAP + biochar (0.05% each, T5). Afterwards, the wheat seeds were sown in the soil. At wheat postharvest, rice was sown without any further treatment. Raw effluent was applied as an irrigation source during the whole growth period of both crops since it is the common practice of the farmers of study area. It was revealed that the use of amendments enhanced the yield and photosynthesis but lowered the Cd contents in straw as well as grains of both crops. In both crops, the highest yield of straw and grain was found in DAP + FYM whereas the lowest Cd concentration was found in DAP alone. The ammonium bicarbonate-DTPA extractable Cd of post wheat and post rice soils were decreased while the soil pH and immobilization index were increased in all treatments as compared with the control. The present field study highlighted that the DAP + FYM can be effective in increasing yield with decreased Cd concentrations in crop grains.  相似文献   

8.
Arsenic (As) sorptivity and acetate (pH 4.8) and oxalate (pH 3.0) extractable iron levels were monitored for 180 d, during and after flooding of two As contaminated soils. The effects of three different organic matter supplements/amendments, for example farm yard manure (FYM), municipal solid waste compost (MSWC) and sewage-sludge (SS) on the above parameter were also examined. In nonflooded soils, As sorptivity was mainly influenced by clay content. On flooding, there were large increases in acetate, oxalate extractable iron and As sorptivity. Organic matter addition increased the same parameters. Among the organic matters, SS showed greater effect on As sorption followed by MSWC and FYM. During flooding, As sorption is mainly dependent upon poorly crystalline iron oxide. During oxidation of previously flooded soils, levels of As sorptivity, acetate and oxalate extractable iron decreased rapidly, but did not return to the levels occurring before reduction. SS and MSWC served as binding agents for native and irrigation water As, thereby moderating the rapid As mobilization to the crop rizosphere.  相似文献   

9.
We studied the effects of poultry manure and pistachio compost with and without phosphorus fertilizer on the kinetics of phosphorus desorption in two calcareous soils of Kerman and Koohbanan farms in the southeastern of Iran. For this purpose mono potassium phosphate, at rates of 0, and 100 parts per million of phosphorus, and air-dried manure, at rates of 0 and 4% were mixed with the soils. The soils were incubated at 24–25°C and near field capacity for 90 days in the greenhouse. Afterwards, the desorption of P was studied by the successive extraction with 0.5 M NaHCO3. The results of this research indicated that application of OM and fertilizer P combined increased P recovery in each of the extraction time, adding poultry manure and 100 mg phosphorus together to the soils, increased P desorption more than pistachio compost in the soils. The phosphorus desorption rate was initially rapid and then became slower until equilibrium was approached. Kinetic data were best described by power function and simple Elovich equations. Subsequent to these equations, parabolic diffusion equation was also well fitted the time-dependent P desorption data.  相似文献   

10.
This study investigated the removal efficiency of pharmaceuticals from aqueous solutions supported on chemically treated fly ash. The coal fly ash was supplied by the electric power station in Krakow, Poland. There are plenty of studies showing the utilization of fly ash as a low-cost adsorbent for wastewater containing heavy metals or dyes. Adsorption and immobilization of pharmaceuticals and personal care products on fly ash is a relatively new method but it is a very promising one. In this study, the adsorptive removal of diclofenac, ketoprofen, carbamazepine, bezafibrate, bisphenol A, 17α-ethinyl estradiol and estriol by HCl- and NaOH-treated fly ash was assessed. Chemical treatment of fly ash changed structures of particles and enhanced specific surface areas. HCl-treated fly ash was characterized by the highest BET specific surface area 47.9 m2 g?1 and unburned carbon content 8.1%. Isotherms for all compounds except for 17α-ethinyl estradiol (EE2) and estriol (E3) were linear. Higher linear regression coefficients (R 2) obtained for isotherms of EE2 and E3 show that the Freundlich model better describes their sorption. Adsorption coefficients K d varied between 109.5 (L kg?1) for bisphenol A and 471.5 (L kg?1) for bezafibrate. Freundlich constants (K F) for EE2 and E3 were 62.3 and 119.9 (µg1?1/n L1/n kg?1), respectively. Acid treatment of fly ash increased adsorption of diclofenac, ketoprofen, carbamazepine, bezafibrate and bisphenol A. Comparison of the octanol–water partitioning coefficients (log K OW) with the partitioning coefficients normalized on unburned carbon content (log K UC) revealed similarities but no strong correlation. The increasing of unburned carbon increased sorption of compounds to fly ash.  相似文献   

11.
Most arid and semi-arid soils, especially calcareous sandy soils, are widely distributed in the Middle East region; the deficiency in their content of many nutrients particularly phosphorus and organic matter limits crops production. This study aimed to assess the effects of adding biochar (B) with farmyard manure (FYM) and poultry manure (PM) on some soil properties, phosphorus (P) availability, and barley growth in calcareous sandy soil. The pot experiment includes the following treatments: Control, B, B?+?FYM (1:1), B?+?PM (1:1), B?+?FYM (2:1), B?+?PM (2:1), FYM?+?B (2:1), and PM?+?B (2:1). Biochar combined with FYM and PM enhanced the water holding capacity (WHC) and soil organic matter (SOM) content in calcareous sandy soil. Phosphorus availability was increased significantly by applying biochar mixed with farmyard manure and poultry manure at all treatments. Green biomass of barley improved because of adding biochar alone, poultry manure alone, and biochar co-applied with poultry manure at all mixing ratios. Biochar application caused significant increases in phosphorus use efficiency (PUE) by barley plants compared to all other treatments, except for the control. We recommend adding biochar either individually or mixed with poultry manure to improve the productivity of calcareous sandy soil.  相似文献   

12.
《Applied Geochemistry》2002,17(8):1159-1164
Fly ash was modified by hydrothermal treatment with 7 M NaOH. The resultant product displayed an 8-fold increase in surface area. The primary crystalline component of the modified fly ash was identified by X-ray diffraction to be hydroxysodalite (Na6Al6Si6O248H2O). The cation exchange capacity of the modified ash was significantly increased over that of the raw fly ash (188 vs 2 meq g−1). Adsorption experiments showed that the modified fly ash adsorbed a cationic dye (methylene blue) to a much greater extent than an anionic dye (alizarin sulfonate). Saturation adsorption revealed that the capacity of the ash for methylene blue had increased 10-fold during modification when compared to the raw ash. Adsorption is thus ascribed to be a surface effect rather than involving incorporation into the channels of the hydroxysodalite structure.  相似文献   

13.
A field-scale experiment was conducted to evaluate various organic C sources as amendments for passive treatment of tailings pore water. Varied mixtures of peat, spent-brewing grain (SBG) and municipal biosolids (MB) were assessed for the potential to promote dissimilatory sulfate reduction (DSR) and metal-sulfide precipitation. Five amended cells and one control were constructed in the vadose zone of a sulfide- and carbonate-rich tailings deposit, and the geochemistry, microbiology and mineralogy were monitored for 4 a. Increases in pore-water concentrations of dissolved organic C (DOC) and decreases in aqueous SO4 concentrations of >2500 mg L−1 were observed in cells amended with peat + SBG and peat + SBG + MB. Removal of SO4 was accompanied by shifts in δ34S-SO4 values of >+30‰, undersaturation of pore water with respect to gypsum [CaSO4·2H2O], and increased populations of SO4-reducing bacteria (SRB). Decreases in aqueous concentrations of Zn, Mn, Ni, Sb and Tl were observed for these cells relative to the control. Organic C introduction also supported growth of Fe-reducing bacteria (IRB) and increases in Fe and As concentrations. Enhanced Fe and As mobility occurred in all cells; however, maximum concentrations were observed in cells amended with MB. Subsequent decreases in Fe and As concentrations were attributed to DSR and metal-sulfide precipitation. The common presence of secondary Zn-S and Fe-S phases was observed by field emission-scanning electron microscopy (FE-SEM) and energy dispersive X-ray (EDS) spectroscopy. Selective extractions indicated that large decreases in water-soluble SO4 occurred in cells that supported DSR. Furthermore, amendments that supported DSR generally were characterized by slight decreases in solid-phase concentrations of extractable metal(loid)s. Amendment of tailings with organic C amendments that supported ongoing DOC production and DSR was essential for sustained treatment.  相似文献   

14.
Clay liners or compacted earthen barriers are important barrier materials used for preventing contaminant transport through soils. A low hydraulic conductivity (k) is a significant parameter that governs the design and construction of clay liners. Compacted expansive clays, which are montmorillonite clays, also have a very low hydraulic conductivity (k). When expansive clays are blended with fly ash, an industrial waste, the hydraulic conductivity (k) further reduces as the ash-clay blends result in increased dry densities at increased fly ash contents. Hence, fly ash-stabilised expansive clay can also be proposed as a unique clay liner material. As expansive clays undergo heave when they come into contact with water, it is necessary to study the heave behaviour of fly ash-stabilised expansive clay liners. This paper presents heave studies on fly ash-stabilised expansive clay liners. Fly ash in different contents by dry weight of the expansive clay was added to the clay, and the ash-clay blend was compacted as a liner overlying a natural field soil layer. Compacted lateritic clay was used for simulating the natural field soil into which contaminants migrate. Calcium chloride (CaCl2) solution of varying concentration (5, 10, 20, 50, 100 and 500 mM) was used as the permeating fluid in the heave studies. The rate of heave and the amount of heave of the fly ash-stabilised expansive clay liners were monitored. Deionised water (DIW) was also used as inundating fluid for comparative study. Heave (mm) decreased with increase in solute concentration for all fly ash contents. For a given solute concentration, heave decreased up to a fly ash content of 20 % and thereafter it increased when the fly ash content was increased to 30 %. Heave of the fly ash-stabilised expansive clay liners was correlated with their permeability, liquid limit (LL) and free swell index (FSI) pertaining to the respective fly ash content and CaCl2 concentration.  相似文献   

15.
The adsorption capacity of seven organic wastes/by-products (slash pine, red gum and western cypress bark, composted green waste, prawn exoskeletons, spent brewery yeast and mill mud from a sugar mill) for transition metals were determined at two metal concentrations (10 and 100 mg L−1) and three equilibrium pH values (4.0, 6.0 and 8.0) in batch adsorption experiments. All tested materials indicate a positive affinity to adsorb metal cations from aqueous solution and spent yeast was the least effective. Adsorption generally increased with increasing pH and the order of selectivity of metals was: Cr3+ > Cu2+ > Pb2+ > Zn2+ ≥ Cd2+. For pine bark, compost, spent yeast and prawn shell, quantities of previously adsorbed Pb and Cd desorbed in 0.01 M NaNO3 electrolyte were negligible. However, 0.01 M HNO3, and more particularly 0.10 and 0.50 M HNO3 were effective at removing both adsorbed Pb and Cd. Using 0.10 M HNO3 as the regenerating agent, pine bark and compost maintained their Pb and Cd adsorption capacity over eight successive adsorption/regeneration cycles. For mill mud and prawn shell, there was a pronounced decrease in adsorption capacity after only one regeneration cycle. A subsidiary experiment confirmed that acid pre-treatment of the latter two materials appreciably reduced their Pb and Cd adsorption capacity. This was ascribed to the metal adsorption capacity of prawn shell and mill mud being partially attributable to their significant CaCO3 content and acid treatment induces dissolution of the CaCO3. It was shown that in relation to both adsorption capacity and desorption/regeneration capability, composted green waste showed the greatest potential.  相似文献   

16.
《Applied Geochemistry》2002,17(2):93-103
Mimicking geochemical processes to solve environmental problems was implemented in dealing with waste acidic jarosite and alkaline coal fly ash. By placing these two chemically different materials adjacent to one another, a self-sealing layer was formed at the interface between both wastes, isolating and immobilizing chemical constituents in the process. A series of leaching experiments were performed on each material separately to study the release behavior of the principal constituents. Radiotracer experiments were conducted to explore diffusion and reaction of constituents such as Fe3+ in a combined jarosite/fly ash system. A model has been developed to simulate the coupled processes of diffusion and precipitation taking into account porosity change due to pore filling by precipitates. The formation of a self-sealing isolation layer in a hypothetical jarosite/fly ash disposal site was modelled. Leaching results indicate that the release of elements from jarosite is much larger than that from fly ash, and that the highly pH dependent release of Fe, Al, and Zn was controlled by the solubility of their hydroxides. Leaching results also suggest that precipitation reactions can be expected to occur at the interface between jarosite and alkaline coal fly ash where a large pH gradient exists. Radiotracer experiments showed that accumulation of constituents occurred at the interface. Modeled Fe3+ profiles in layered jarosite/fly ash were well validated by experiments. Modeling results also showed that with the accumulation of constituents at the interface, a new layer with low porosity was formed. Application of this model suggests that there is a potential use to form a self-sealing layer in jarosite/fly ash co-disposal sites.  相似文献   

17.
The objective of this study was chemical and radiological characterization of Kastela Bay sediments exposed to numerous anthropogenic sources like deposition of fly and bottom ash enriched in radionuclides and heavy metals, chemical plant, cement plant, iron plant, shipyard, electroplating facility, untreated industrial and domestic waste waters as well as heavy traffic. Totally, 33 samples of the mixture of fly and bottom ash, 12 sediment cores ranging from 0 to 40 cm and nine surface sediment samples were analyzed. Enrichment in heavy metals in the mixture of fly and bottom ash was ranging from 1.5 to 36 times compared to flysch soil while 226Ra and 238U were up to 50 times enriched compared to average activities characteristic for surrounding soils developed on the Middle and Upper Eocene flysch. Maximum 238U activity was approximately 32 times higher and 226Ra approximately 40 times higher in the Kastela Bay sediment compared to mean value determined for Adriatic sediments. The highest enrichment in sediment cores compared to background values were found for Zn (35.6 times), Pb (16 times), Cr (9.1 times) and Ni (4 times)  相似文献   

18.
Municipal solid waste compost and cattle manure are used as organic fertilizers in agriculture and horticulture. These wastes, however, may also have some negative effects on the agricultural environment. This study investigates the effects of municipal solid waste compost of Kerman (MSC) and cattle manure (CM) on availability of the heavy metal in calcareous soil (extractable with EDTA) in greenhouse conditions. The MSC and CM were mixed thoroughly with soil at rates of 0%, 2%, and 4% of dry matter. After 90 days of incubation, the soil samples were analyzed. Addition of levels of each two organic wastes into soil significantly decreased the soil pH and increased the soil EC as compared with control (unamended soil).The available contents (EDTA-extractable) of Cd, Pb, Cu, Zn, and Cu in the soil samples were increased because of each two organic treatments applied. The heavy metal contents in the soil samples amended with MSC were more than CM. The heavy metal contents of organic wastes were well below the maximum allowed by USEPA. It is recommended that in Iran, the legal maximum permissible limit for heavy elements in organic wastes must be determined.  相似文献   

19.
The isotopic compositions of S (δ34S) and C (δ13C) were determined for the coal utilized by a power plant and for the fly ash produced as a by-product of the coal combustion in a 220-MW utility boiler. The coal samples analyzed represent different lithologies within a single mine, the coal supplied to the power plant, the pulverized feed coal, and the coal rejected by the pulverizer. The ash was collected at various stages of the ash-collection system in the plant. There is a notable enrichment in 34S from the base to the top of the coal seam in the mine, with much of the variation due to an upwards enrichment in the δ34S values of the pyrite. Variations in δ34S and in the amount of pyritic S in the coal delivered to the plant show that there was a change of source of coal supplied to the plant, between week one and week two of monitoring, supporting a previous study based on metal and sulfide geochemistry for the same plant. The fly ash has a more enriched δ34S than the pulverized coal and, in general, the δ34S is more enriched in fly ashes collected at cooler points in the ash-collection system. This pattern of δ34S suggests an increased isotopic fractionation due to temperature, with the fly ash becoming progressively depleted in 34S and the flue gas S-containing components becoming progressively enriched in 34S with increasing temperatures. Substantially less variation is seen in the C isotopes compared to S isotopes. There is little vertical variation in δ13C in the coal bed, with δ13C becoming slightly heavier towards the top of the coal seam. An 83–93% loss of solid phase C occurs during coal combustion in the transition from coal to ash owing to loss of CO2. Despite the significant difference in total C content only a small enrichment of 0.44–0.67‰ in 13C in the ash relative to the coal is observed, demonstrating that redistribution of C isotopes in the boiler and convective passes prior to the arrival of the fly ash in the ash-collections system is minor.  相似文献   

20.
《Applied Geochemistry》1995,10(4):391-405
Extensive NO3− contamination of groundwater in the Abbotsford aquifer to levels above drinking water limits is a major problem in the Fraser Lowlands of southwestern British Columbia, Canada. Nitrate concentrations in the aquifer ranged from 0 to 151 mg/l NO3−, with a median concentration of 46 mg/l NO3−. Of 117 wells sampled, 54% had NO3− concentrations exceeding the drinking water limit of 45 mg/1. Approximately 80% of the study area had groundwater NO3− concentrations exceeding 40 mg/1 NO3−. Potential NO3− source materials were poultry manure N and synthetic NH4 based fertilizers. Theδ15N of solid poultry manure samples ranged between + 7.9 and + 8.6‰ (AIR). Four brands of synthetic fertilizers commonly used hadδ15N values between −1.5 and −0.6‰. Ammonia volatilization caused theδ15N of groundwater NO3− produced from poultry manure N to range between +8 and +16‰. Theδ18O values of groundwater NO3−, by contrast, mostly ranged between +2 and +5‰ (SMOW). This narrow range ofδ18O values fell within the expected range of NO3− produced by nitrification of reduced N forms such as poultry manure N and NH4 fertilizers, and had a similar range ofδ18O values as NO3− in the upper part of the unsaturated zone below raspberry fields and beneath former manure piles. Theδ15N-NO3− andδ18O-NO3− data confirmed that NO3− in the aquifer was predominantly derived from poultry manure and to a lesser extent from synthetic fertilizers. Theδ18O-NO3− data further suggested the nitrification process occurred mainly in the summer months, with the soil NO3− produced subsequently flushed into the aquifer during fall recharge. Theδ15N-NO3−andδ18O-NO3− data conclusively indicated that no significant bacterial denitrification is taking place in the Abbotsford aquifer.  相似文献   

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