Radiocarbon dating techniques for tephras in central North Island,New Zealand

Tephra samples from Whakatane Ash and Rotoma Ash in central North Island of New Zealand were subject to a wide range of chemical treatments in order to isolate different components of soil organic matter for radiocarbon dating. These samples were radiocarbon-dated before and after treatments and were then compared with radiocarbon dates derived from charcoal in the same tephra formation.Tephra deposits when dated as whole samples without prior chemical treatments, yielded unreliable radiocarbon dates. The reliability was improved by chemical treatments, particularly those involving acid hydrolysis with 6 M HCl or 72% H₂SO₄. Improvement, however, was less using the classical humus extraction and fractionation procedure.     

RADIOCARBON DATING OF PALEOSOLS USING SOIL ORGANIC MATTER COMPONENTS

Soil organic matter components of classical humic acid and humic fractions were extracted from two paleosols using 0.1 M Na₄ P₃ O₂:0.1 M NaOH. These fractions were subjected to chemical treatment with 6 M HC1 or 70 per cent HNO, before radiocarbon assay, and their radiocarbon dates were compared with those of similar but untreated fractions, untreated buried soils, and previously published charcoal dates. Hydrolysis of humic acid and humin fractions with mineral acids, particularly 70 per cent HNO₃ led to older radiocarbon dates, comparable to, though slightly older than, those of charcoal derived from the same buried layers. In contrast, the dates of soils and their humic acid and humin fractions before acid hydrolysis were younger and therefore less reliable. The application of this procedure to studies of paleosols in New Zealand is discussed.     

Radiocarbon analysis of methane emitted from the surface of a raised peat bog

We developed a method to determine the radiocarbon (¹⁴C) concentration of methane (CH₄) emitted from the surface of peatlands. The method involves the collection of ∼9 L of air from a static gas sampling chamber which is returned to the laboratory in a foil gas bag. Carbon dioxide is completely removed by passing the sample gas firstly through soda lime and then molecular sieve. Sample methane is then combusted to CO₂, cryogenically purified and subsequently processed using routine radiocarbon methods. We verified the reliability of the method using laboratory isotope standards, and successfully trialled it at a temperate raised peat bog, where we found that CH₄ emitted from the surface dated to 195–1399 years BP. The new method provides both a reliable and portable way to ¹⁴C date methane even at the low concentrations typically associated with peatland surface emissions.     

Influence of fertilizers applied to a paddy-upland rotation on characteristics of soil organic carbon and humic acids

The qualitative and quantitative characteristics of soil organic carbon (SOC) and related humic acids (HAs) extracted from the soils of field plots were investigated after 8 years of annual paddy (Oryza sativa L.) and upland maize (Zea mays L.) rotation with various fertilizations. Seven fertilization treatments were selected: Ck (no inputs); Chem (chemical fertilizer of NPK); Comp (swine compost); Comp + 33% of Chem N rate; Comp + 67% of Chem N rate; GM (legume green manure) + 33% of Chem N rate; and peat + 33% of Chem N rate. Organic and inorganic nitrogen inputs of six treatments were equivalent with respect of nitrogen content, but Comp, GM, and peat treatments were complemented with various amounts of inorganic N. After harvest of the eighth paddy crop, surface soil samples collected from the plots were subjected to soil characterizations and extraction of humic substances, which were used for chemical, spectroscopic (FTIR, 13C NMR, ESR, X-ray diffractometry), delta13C, and 14C dating analyses. The yields of HAs extracted from the seven treatments were significantly different. Treatment containing persistent organic compound such as the peat + 33% N treatment increased the humification process in topsoils and produced higher yield of HA. Spectroscopic analyses revealed that fertilization treatments changed the functional groups, alkyl C, crystalline characteristics, and delta13C ratios of HAs and turnover rate of SOC considerably. The SOC of the peat + 33% N treatment had the highest mean residence time of 3100 years. Various fertilizer treatments are correlated with turnover rate of SOC and related HAs, which are associated with concerned carbon sequestration as well as mitigation of CO2 emission in the soil environment.     

Amino acids in Quaternary soil horizons from southwest Poland

Aminostratigraphy has proved to be a useful approach for dating fossils from the Quaternary. In these studies the amino acids in Quaternary soil formations were determined in an attempt to establish their stratigraphical relationships and relative ages. The sampling sites are in the southwest of Poland, in the Trzebnickie Hills. Three samples of fossil soils and two of recent soils were analysed. The absolute age of the soil samples was estimated by radiocarbon dating. We found that the total amount of amino acids decreased with the increasing age of soil. The smallest amounts of amino acids were found in the oldest fossil soil of Denekamp (Vistulian) age dated 29 600 ± 760 years bp . A sample of recent loess soil contained the most total amino acids, whereas the fossil soil of Lower Atlantic age, dated 3540 ± 230 years bp , was intermediate in respect of the total amount of amino acids, oxidation state and degree of biochemical transformation. Neutral amino acids formed a majority of all the amino acids studied. The method we describe could be useful in relative chronostratigraphical identification of fossil soils.     

Influence of organic matter and inorganic fertilizer on the growth and nitrogen accumulation of corn plants

Effects of different nitrogen (N) sources on the growth and N accumulation of corn plants were studied on plots treated with a compost, a leguminous green manure, and a peat, respectively, associated with a chemical N fertilizer. The experiment included seven treatments with a no‐fertilization check and a conventional chemical fertilizer treatment. Whole corn plants were sampled, and total N was analyzed at 22, 33, 56, 77, and 120 days after seeding (DAS). The results showed that compost with an adequate amount of chemical N fertilizer could reach a high dry matter yield and a high N accumulation, even higher than those of the conventional chemical N fertilizer treatment. With green manure, a considerable amount of N was mineralized and utilized by the corn plants for growth and resulted in a good yield. Neither the peat nor the compost alone could supply enough N for the growth of corn plants. There were no significant effect of treatments on the distribution of dry matter yield and N accumulated in various organs. The crop growth rate of the corn plants of different treatments were significantly different at the vegetative growth stage, however, there were no significant difference during the grain filling period. The apparent N recovery of various treatments were between 0.22 to 0.51 kg N for each kg N applied.     

Microwave digestion of fertilizers and soil amendments

Abstract

The trace element pollution hazard of the continuous and large scale application of fertilizers and other amendments to soils depends in part on the chemical composition of these materials. Complete sample dissolution is generally required prior to total elemental analyses. The objectives of this study were to evaluate closed vessel microwave digestion procedures, using HNO₃, HF, H₂O₂, and H₃BO₃, for the total dissolution of fertilizers and soil amendments and to develop a general digestion guide for individual samples. Twenty‐six materials, including commercial fertilizers, rock phosphate, liming materials, organic sources, and a soil sample were studied. More than 99.5% of each of these materials could be dissolved. Commercial nitrogen (N) fertilizers, most of the ammonium phosphates, and a potassium chloride sample could be completely dissolved using exclusively HNO₃. The other samples required HNO₃ and HF, used either in mixtures or consecutively in a stepwise procedure. The sewage sludge materials, the soil sample, and one of the rock phosphates were the only samples that could not be totally dissolved. No improvement in the digestions was observed by including H₂O₂. No significant contamination was evident during the digestions and satisfactory recoveries of 14 trace elements were obtained in digests of 2 standard reference materials. The proposed dissolution procedures are simple and safe. The usual quickness of microwave procedures was partially sacrificed to obtain a more complete dissolution of the samples. Digests obtained with these procedures could be potentially analyzed for other analytes, with the obvious exceptions of N, fluorine (F), and boron (B).     

Effects of Different Organic Materials on Crop Production under a Rice–Corn Cropping Sequence

Soil organic matter (SOM) is an important index of soil quality because of its relationship with crop yield. The application of organic matter to soil is a significant method for increasing SOM. Different organic materials have varying effects in increasing SOM. This study investigates the effects of combining different sources of organic matter (i.e., compost, leguminous green manure, and peat) with a chemical nitrogen (N) fertilizer on the growth and N accumulation in corn and rice plants. This study examines seven treatments, including a no-fertilization check and a conventional chemical fertilizer treatment. Shoots of corn and rice were sampled at the tasseling (panicle initiation for rice) and maturity stages. The biomass yield was measured and the total N was analyzed. At the maturity stage, the soil samples were collected to determine the chemical properties. The results showed that a small percentage of the N in the compost and peat, after their application, was available to the crop during the growth season; the production of biomass and N absorption among rice and corn plants was minimal compared to that treated with chemical N fertilizer. The application of compost and peat resulted in SOM accumulation, particularly with peat. However, the application of compost combined with chemical fertilizer not only produced sufficient nutrients for crop growth but also resulted in an accumulation of SOM, which is vital for enhancing the soil quality. Most of the N in green manure (GM) was mineralized shortly after application, causing excessive growth of rice and corn plants during the early stage, but reducing their reproductive growth and grain yield.     

基于木本泥炭快速构建红壤新垦耕地优质耕作层技术与效果

为了探究木本泥炭对红壤岗地新垦耕地优质耕作层构建的机理以及木本泥炭相对于其他有机物料对红壤新垦耕地的改良效果,采用田间小区试验的方法,研究添加不同有机物料对红壤新垦耕地0—20cm耕作层土壤理化性质和微生物生物量以及水稻产量的影响。试验共设6个不同处理:CK(不添加改良材料)、M30FS(木本泥炭30t/hm2+腐熟秸秆3t/hm2+石灰石粉3.75t/hm2)、M15FS(木本泥炭15t/hm2+腐熟秸秆3t/hm2+石灰石粉3.75t/hm2)、CFS(生物炭15t/hm2+腐熟秸秆3t/hm2+石灰石粉3.75t/hm2)、OFS(有机肥15t/hm2+腐熟秸秆3t/hm2+石灰石粉3.75t/hm2)和FS(腐熟秸秆3t/hm2+石灰石粉3.75t/hm2)。结果表明:(1)与对照相比,添加木本泥炭与有机物料处理显著降低了耕作层土壤容重,提高了土壤总孔隙度和pH,且添加木本泥炭与有机物料处理中土壤肥力均有不同程度提高,其中土壤有机质、全氮、全磷和全钾含量分别提高了36.41%～88.53%,2.22%～37.78%,6.25%～93.75%和27.57%～85.60%,土壤硝态氮、铵态氮、有效磷和有效钾含量分别提高了17.21%～134.85%,1.42%～72.76%,8.71%～156.79%和12.99%～332.39%。(2)添加木本泥炭与有机物料处理对耕作层土壤微生物生物量影响比较明显,与对照相比,各处理中土壤微生物量碳和氮含量分别显著增加了52.95%～219.00%和121.45%～548.73%。(3)添加木本泥炭与有机物料处理中水稻产量均明显提高,其中M30FS增产效果最明显,增幅为39.53%。(4)利用聚类分析方法将添加不同有机物料处理下新垦耕地耕作层土壤质量等级划分为3级,分别为:一级(M30FS)、二级(M15FS,OFS,CFS)、三级(FS,CK),其中经M30FS处理后土壤质量水平等级最高。添加木本泥炭与有机物料可显著降低新垦耕地耕作层土壤容重,提高土壤总孔隙度和pH,解决了红壤黏重和酸化的特征,且土壤养分和微生物量碳、氮含量均得到了提高,改善了土壤理化性状和生物学特征,提高了水稻产量,其中添加30t/hm2木本泥炭对红壤新垦耕地优质耕作层构建效果最明显。     

Interaction between a peat carrier and bacterial seed treatments evaluated for biological control of the take-all diseases of wheat (Triticum aestivum L.)

Summary Field plots were established in Indiana, Oregon, and Montana to evaluate the potential for biological control of various strains of bacteria as seed treatments to reduce the severity of take-all root, crown, and foot rot of wheat. The bacteria were grown in liquid broth Cas-amino acid broth media, mixed with finely ground peat, and applied to seed with methyl cellulose as a glue just before planting in field soils conducive for severe take-all. Autoclave-sterilized peat (minus bacteria) seed treatments increased take-all, immobilized Mn, and reduced plant vigor and grain yields. These effects were intensified when the pH of the natural peat was adjusted from 5.2 to 7.0 with CaCO₃. The ability of the bacterial strains to counteract this peat-induced predisposition to take-all varied, and was influenced by planting site, genetic tolerance of the cultivar, and N treatment. Although the strains differed in their ability to suppress the peat-induced take-all, none of the isolates fully nullified the deleterious effects of the peat carrier. It is clear from this study that the carrier used with potential biological-contol agents may have a greater influence on disease than the biological agent.     

中南地区淋溶土的层间羟基物矿物

将北纬 3 0°～ 3 2°亚热带花岗岩发育的两个淋溶土B层黏粒样分别用连二亚硫酸钠—柠檬酸钠—重碳酸钠 (DCB)溶液溶提处理和经DCB溶液处理后再用柠檬酸钠溶液溶提处理。从上述处理后样品的X射线衍射图谱中可看出 :供试土壤的膨胀性矿物层间有羟基物质 ,它们能被DCB溶液—柠檬酸钠溶液所溶解提取 ,含羟基物质的黏土矿物主要来源于蛭石 ,少量来自蒙皂石。DCB溶液—柠檬酸钠溶液处理前后黏粒红外差分光谱上显示的 980～ 970cm- 1 ,91 0～940cm- 1 吸收带 ,标志着供试土壤膨胀性矿物层间含有羟基铝硅酸和羟基铝离子。从而首次揭示了中国中南地区淋溶土的膨胀性矿物层间有羟基铝硅酸。     

不同木薯渣形态和添加比例对番茄产量品质及抗氧化能力的影响

  【目的】  为积极应对我国基质生产原料草炭紧缺的难题,提升农业废弃物的综合利用水平,研究木薯渣形态和添加比例在番茄生产上的应用效果,以期为木薯渣在番茄无土栽培上的推广应用提供理论依据。  【方法】  以‘千禧’樱桃番茄 (QX) 和‘传奇2号’大番茄 (CQ) 为试材,进行了槽栽试验。通过计算机模拟,共配置了4个栽培基质,包括草炭∶蛭石∶珍珠岩∶粉状木薯渣 = 5∶5∶5∶5 (T1);草炭∶蛭石∶珍珠岩∶颗粒状木薯渣 = 5∶5∶5∶5 (T2);草炭∶蛭石∶珍珠岩∶颗粒状木薯渣 = 6∶4∶4∶6 (T3) 和草炭∶蛭石∶珍珠岩∶粉状木薯渣 = 4∶4∶4∶8 (T4)。以常规基质草炭∶蛭石∶珍珠岩=10∶5∶5为对照 (CK)。测定了各栽培基质的理化性状和养分含量,调查了番茄生长和果实产量及品质。  【结果】  CQ和QX番茄在T1和T4处理下,其茎粗、根系活力、地下部和地上部干重均显著高于CK,且T1处理下增幅大于T4;T2和T3处理下,果实品质和抗氧化能力显著高于CK,且T2处理下增幅大于T3处理,T2处理下,CQ和QX番茄中可溶性糖、可溶性固形物含量、糖酸比、维生素C、番茄红素、可溶性蛋白和总酚含量分别较CK提高42.5%、29.4%、26.7%、21.0%、25.1%、51.1%、17.1%和28.0%、26.3%、19.4%、46.0%、22.4%、19.0%、25.8%,果实总抗氧化能力和DPPH自由基清除能力分别较CK提高51.9%、44.0%和40.4%、72.4%;T1处理下产量显著高于其它处理,CQ和QX番茄产量分别较CK提高15.6%和33.7%;两品种番茄的综合评价均为T1 > T4 > T2 > T3 > CK。  【结论】  添加颗粒状和粉状木薯渣均能不同程度地提高基质的pH、电导率、容重及速效氮、速效磷和速效钾含量,且颗粒状木薯渣处理提高幅度大于粉状木薯渣处理,但添加颗粒状木薯渣的基质气水比亦增加,持水性不如粉状木薯渣。4个配方中,以木薯渣替代一半草炭的增产提质效果最好,超过一半效果显著降低。在替代一半草炭的两个配方中,添加颗粒状木薯渣 (T2) 提高番茄品质的效果最佳,而添加粉状木薯渣 (T1) 的番茄产量最高。DTOPSIS综合分析,T1处理下的C_i值最大。因此,推荐草炭∶蛭石∶珍珠岩:粉状木薯渣=5∶5∶5∶5 (T1) 配方基质作为番茄无土栽培专用基质进行推广应用。     

Lead in Three Peat Bog Profiles,Jura Mountains,Switzerland: Enrichment Factors,Isotopic Composition,and Chronology of Atmospheric Deposition

One metre cores were taken from three peat bogs in the Jura Mountains of Switzerland: Etang de la Gruère (EGr), La Tourbière des Genevez (TGe), and Praz Rodet (PRd). Dried peat samples were analyzed for lead (Pb) using the EMMA XRF and scandium (Sc) using INAA. Enrichment factors (EF) were calculated by normalizing to the background Pb/Sc ratio at EGr. Age dates were obtained using 210Pb (CRS Model) and confirmed using pollen chronostratigraphic markers in replicate cores. The isotopic composition of Pb in selected peat samples from EGr and TGe was determined using TIMS. Two pronounced peaks in Pb EF occur in the uppermost sections of all three bogs: the upper one corresponds to the late 1960's to late 1970's and the lower one to approximately 1900 to 1920. At EGr, sample 2f5 (11 cm, 86 µg/g Pb, EF = 91, and dated at A.D. 1967 ± 2) has an isotopic composition similar to that of leaded gasoline used in Berne in the 1970's. For comparison, the older peak at EGr (sample 2fl 1 at 29 cm, 84 µg/g Pb, EF = 79 and dated at A.D. 1905 ± 6) is significantly different. In contrast to these two samples, the isotopic composition of sample 2fl 5 (41 cm, 30 µg/g Pb, EF = 13 and pre-dating ca. A.D. 1800) approaches the present day "average terrestrial lead" and is likely to be predominately lithogenic. Therefore, the isotopic data show that the Pb introduced to the bog from leaded gasoline has not penetrated to this depth in the profile. A simple mass balance using the measured Pb concentrations and the isotopic compositions shows that vertical migration of gasoline Pb cannot explain the deeper, older peak in Pb EF. A more likely explanation is that the older peak reflects the rates of atmospheric Pb deposition during the first two decades of the 20th century. Taken together, the Pb concentrations, age dates, and isotopic data suggest that these peat profiles have preserved the record of changing rates of atmospheric Pb deposition. In addition, the results indicate that the isotopic composition of Pb deposited on the surface of the bogs gradually shifted away from lithogenic ratios as long ago as the middle of the 19th century, a change which clearly pre-dates the introduction of leaded gasoline.     

Influence of water depth and soil amelioration on greenhouse gas emissions from peat soil columns

Recently, large areas of tropical peatland have been converted into agricultural fields. To be used for agricultural activities, peat soils need to be drained, limed and fertilized due to excess water, low nutrient content and high acidity. Water depth and amelioration have significant effects on greenhouse gas (GHG) production. Twenty-seven soil samples were collected from Jabiren, Central Kalimantan, Indonesia, in 2014 to examine the effect of water depth and amelioration on GHG emissions. Soil columns were formed in the peatland using polyvinyl chloride (PVC) pipe with a diameter of 21 cm and a length of 100 cm. The PVC pipe was inserted vertically into the soil to a depth of 100 cm and carefully pulled up with the soil inside after sealing the bottom. The treatments consisting of three static water depths (15, 35 and 55 cm from the soil surface) and three ameliorants (without ameliorant/control, biochar+compost and steel slag+compost) were arranged using a randomized block design with two factors and three replications. Fluxes of carbon dioxide (CO₂), methane (CH₄) and nitrous oxide (N₂O) from the soil columns were measured weekly. There was a linear relationship between water depth and CO₂ emissions. No significant difference was observed in the CH₄ emissions in response to water depth and amelioration. The ameliorations influenced the CO₂ and N₂O emissions from the peat soil. The application of biochar+compost enhanced the CO₂ and N₂O emissions but reduced the CH₄ emission. Moreover, the application of steel slag+compost increased the emissions of all three gases. The highest CO₂ and N₂O emissions occurred in response to the biochar+compost treatment followed by the steel slag-compost treatment and without ameliorant. Soil pH, redox potential (Eh) and temperature influenced the CO₂, CH₄ and N₂O fluxes. Experiments for monitoring water depth and amelioration should be developed using peat soil as well as peat soil–crop systems.     

UV-TiO2 Photocatalytic Degradation of Landfill Leachate

Mature landfill leachate contains some macromolecular organic substances that are resistant to biodegradation. The photocatalytic process helps to enhance biodegradability of landfill leachate. Batch experiments were employed to determine the optimum conditions for removal of organic matter by UV-TiO₂ photocatalysis. Under optimum conditions, the removal of chemical oxygen demand (COD), dissolved organic carbon (DOC), biological oxygen demand (BOD), and color was determined. Moreover, gas chromatography coupled with mass spectrometry (GC/MS) was used to analyze the organic matter in the treated leachate before and after treatment by the photocatalysis. The experimental results indicated that the removal of COD, DOC, and color by UV-TiO₂ photocatalysis could reach above 60%, 70% and 97%, respectively. Under optimal conditions, the ratio of biological oxygen demand (BOD)/chemical oxygen demand (COD) was elevated from 0.09 to 0.39, representing substantial improvement in biodegradability. GC/MS analysis revealed that 37 out of 72 kinds of organic pollutants in the leachate remained after 72 h treatment. Esters were produced during photocatalytic process and ketones, hydrocarbons, aromatic hydrocarbons, hydroxybenzenes, and acids were easier to be degraded during photocatalytic oxidation processes. The UV-TiO₂ photocatalysis systems proposed may be a cost-effective approach for pre-treatment of landfill leachate.     

Effect of Steeping Treatment on Pasting and Thermal Properties of Sorghum Starches

Chemical treatments in wet milling could improve the physico‐chemical properties of starch isolated from high‐tannin sorghums. Sorghums Chirimaugute (medium‐tannin), DC‐75 (high‐tannin), and SV2 (tannin‐free) were steeped in water, dilute HCl (0.9%, v/v), formaldehyde (0.05%, v/v), and NaOH (0.3%, w/v) solutions before wet milling and starch separation. Pasting, textural, and thermal properties of starch were determined. Steeping in NaOH resulted in starches with higher peak viscosity (PV), cool paste viscosity (CPV), and setback than when water, HCl, and formaldehyde were used. The time to PV (P_time) and PV temperature (P_temp) were markedly reduced by treatment with NaOH. NaOH could have caused a degree of pregelatinization. HCl treatment gave starches with higher P_temp and P _time, presumably due to delayed granule swelling. Gel hardness was largely determined by the starch amylase content. The low hardness of DC‐75 starch gels was slightly improved in NaOH‐treated grains. Gelatinization temperatures of sorghum starches were generally low, regardless of steeping treatment. Starch from NaOH‐treated grain generally had slightly higher gelatinization temperatures than when water, HCl, or HCHO was used. Chemical treatments during steeping of sorghum grains greatly affected starch properties. Dilute alkali steeping during wet milling could be used to improve properties of starch isolated from tannin‐containing sorghums.     

GROWTH OF PRIMULA PLANT IN COIR DUST AND PEAT-BASED GROWING MEDIA

This study was performed under greenhouse conditions, with coir dust, moss peat, and sedge peat as the main components of the growing media. The performance of the media was evaluated through the growth of the primula (Primula obconica) plant. In general, aeration capacities were found to be relatively low, except for growing media that included moss peat mixtures. Nevertheless, easily available water content of all growing media was found to be within the appropriate ranges. Total and water-available plant nutrient contents of coir dust, moss peat, and sedge peat significantly fluctuated. Ornamental parameters related to media treatments were statistically significant, with respect to visual score performances, total leaf numbers, crown width, and total plant fresh weights. This study determined that coir dust, which is an industrial by-product, could be utilized for up to 50% of the total composition of coir dust-moss peat based media in floricultural aims. As floricultural quality parameters considered, 50% coir dust and 50% moss peat and 25% coir dust and 75% moss peat gave good results as much as 100% moss peat.     

改良剂施用对矿区复垦土壤水稳性团聚体及有机碳组分的影响

  目的  探究施用不同种类和数量改良剂对矿区复垦土壤水稳性团聚体和有机碳的影响。  方法  在山西省古交市屯兰煤矿复垦6年的地块上设置随机区组试验,在0 ~ 20 cm土层按土壤重量的1%、3%、5%分别施用腐殖酸和泥炭两种改良剂,于施用后1年和2年时两次取样测定0 ~ 20 cm土壤团聚体组成、有机碳含量及其组分,对不同种类和数量改良剂的改良效果进行评价。  结果  施用腐殖酸、泥炭后1年时各处理土壤 > 2 mm水稳性团聚体质量分数均高于对照,增幅为1.53% ~ 62.27%,且土壤水稳性团聚体均以大团聚体（> 0.25 mm）为主;施用改良剂后2年时各处理土壤水稳性大团聚体含量降低,降幅为1.73% ~ 11.35%,土壤团聚体以 < 0.053 mm粒级的团聚体为主。施用改良剂后腐殖酸处理的土壤有机碳储量、固碳量和固碳速率呈先增加后减少的趋势,泥炭处理随泥炭施用量的增加而增加。施用改良剂后土壤 > 2 mm粒级团聚体质量分数与土壤有机碳储量呈显著正相关。施用改良剂能增加复垦土壤矿物结合态有机碳含量,且施用腐殖酸处理的含量高于泥炭处理。施用改良剂后2年时与1年相比,复垦土壤颗粒态有机碳含量呈增长的趋势,土壤铁铝键结合态有机碳含量则呈降低趋势。施用腐殖酸、泥炭可增加复垦土壤羧酸、醇类等官能团含量,显著增加土壤中多糖物质的含量。  结论  在矿区复垦土壤上施用腐殖酸、泥炭可显著增加土壤大团聚体数量,提高土壤有机碳、矿物结合态有机碳和颗粒态有机碳含量及土壤固碳量;随腐殖酸、泥炭施用量增加,土壤固碳速率增加、固碳效率减小;复垦区土壤改良需逐年施用腐殖酸、泥炭等改良剂,才能获得稳定的改良效果。     

THE OCCURRENCE OF COPPER-PORPHYRIN COMPLEXES IN SOIL HUMIC ACIDS

Electron paramagnetic resonance (e.p.r.) spectroscopy has been used to show that humic acids, which were isolated from a range of soils and from which most of the iron was removed by boiling with hydrochloric acid, contain copper in the form of porphyrin complexes. The amounts of porphyrin-bound copper in the acid-boiled humic acids were estimated to be ≤ 20 mg/kg (equivalent to 0.05-0.9 mg/kg in the soils). The acid-boiled humic acids from cultivated mineral soils showed no great capacity for further uptake of copper as copper porphyrin when treated with CuSO₄, most of this additional copper being held by groups not involving N-donor groups. In contrast, copper treatment of the acid-boiled humic acid from a raised bog peat produced a large increase in copper-porphyrin signal strength, indicating that in the peat there are considerable amounts of porphyrin by which added copper could be complexed. It is suggested that porphyrin groups may be involved in the fixation of copper by organic matter in soils.     

Comparison of chemical fractionation methods for isolating stable soil organic carbon pools

Stable soil organic matter (SOM) is important for long‐term sequestration of soil organic carbon (SOC), but the usefulness of different fractionation methods to isolate stable SOM is open to question. We assessed the suitability of five chemical fractionation methods (stepwise hydrolysis, treatment with H₂O₂, Na₂S₂O₈, NaOCl, and demineralization of the NaOCl‐resistant fraction (NaOCl + HF)) to isolate stable SOM from soil samples of a loamy sand and a silty loam under different land use regimes (grassland, forest and arable crops). The apparent C turnover time and mean age of SOC before and after fractionation was determined by ¹³C and ¹⁴C analysis. Particulate organic matter was removed by density fractionation before soils were exposed to chemical fractionation. All chemical treatments induced large SOC losses of 62–95% of the mineral‐associated SOC fraction. The amounts of H₂O₂‐ and Na₂S₂O₈‐resistant SOC were independent from land use, while those of NaOCl‐ (NaOCl + HF)‐ and hydrolysis‐resistant SOC were not. All chemical treatments caused a preferential removal of young, maize‐derived SOC, with Na₂S₂O₈ and H₂O₂ being most efficient. The mean ¹⁴C age of SOC was 1000–10000 years greater after chemical fractionation than that of the initial, mineral‐associated SOC and mean ¹⁴C ages increased in the order: NaOCl < NaOCl + HF ≤ stepwise hydrolysis ≪ H₂O₂≈ Na₂S₂O₈. None of the methods appeared generally suitable for the determination of the inert organic matter pool of the Rothamsted Carbon Model. Nonetheless, our results indicate that all methods are able to isolate an older, more stable SOC fraction, but treatments with H₂O₂ and Na₂S₂O₈ were the most efficient ones in isolating stable SOM.