关帝山不同海拔土壤碳矿化和微生物特征

以山西省关帝山不同海拔的8个样地土壤为研究对象,分析不同海拔土壤碳氮含量、土壤碳矿化和细菌、真菌、放线菌、固氮菌、硝化细菌和反硝化细菌6类微生物量的变化.结果表明,海拔为2163m时,土壤有机碳和活性碳1（LC1）最高,分别为74.41和6.72g/kg,在海拔2700m总氮含量最高为6.54g/kg.土壤碳矿化累积量和碳矿化速率因海拔的升高而显著增加（P<0.05）,土壤碳矿化累积量和活性碳2（LC2）之间有显著正相关.土壤细菌、放线菌和固氮菌的数量在海拔为1791m时最高,分别为3.41×10⁶、1.90×10⁶和1.21×10⁶个/g,细菌、真菌、放线菌和固氮菌的数量随着海拔的升高而逐渐下降,与海拔之间呈显著负相关;相反,硝化细菌和反硝化细菌数量却逐渐增加,在海拔为2700m时最高,分别为1.37×10⁴和6.02×10³个/g,它们与海拔和总氮之间的关系呈显著正相关（P<0.01）.总之,土壤有机碳、总氮、碳矿化累积量、硝化细菌和反硝化细菌随海拔显著增加,而细菌、真菌、放线菌和固氮菌随海拔的变化呈相反的趋势.     

微生物诱导碳酸盐沉淀及其在固定重金属领域的应用进展

生物矿化已受到化学、物理、生物、材料、医学、生命及环境等多学科的广泛关注,其中,以尿素为底物的MICP（微生物诱导碳酸盐沉淀）技术是生物矿化领域的研究热点之一.在分析MICP过程中的酶解机理和生物大分子在微生物矿化过程中的作用基础上,通过对重金属离子的矿化产物和碳酸盐矿化菌的成矿因素分析,揭示MICP矿化产物的特征及形成条件.碳酸盐矿化菌主要产生脲酶分解尿素,增加土壤CO₃2-饱和度,其代谢产生的胞外聚合物具有多种功能团组合和键能连接,起着调控生物矿化的作用.MICP技术可用于固定土壤和水体中的Cu、Pb、Zn、Cd、Cr、As等重金属,重金属主要以共沉淀的形式被固定,阴阳离子型重金属以类质同象置换方式分别占据方解石中的CO₃2-位和Ca2+位,从而促使污染土壤中的可交换态重金属向碳酸盐结合态转移.但是,MICP技术主要针对减少重金属的生物可利用性,不能满足以全量来计算的现行土壤环境质量标准,且MICP技术在长期有效性、生物安全性和土壤理化性质等方面存在诸多隐患.因此,由试验条件转向实际应用具有一定挑战.建议寻找更稳定的方法以阻止碳酸盐矿物中的重金属溶出,且有必要将开发高效的土著微生物复合菌剂作为未来MICP研究的方向之一.      

长期不同施肥对稻田土壤有机碳矿化及激发效应的影响

通过室内模拟培养实验,结合14C同位素标记技术,研究了不施肥(CK)、单施化肥(NPK)、秸秆还田+化肥(ST)这3种施肥处理下稻田耕层土壤有机碳矿化特征及其对添加外源葡萄糖的响应特征.结果表明,56 d培养实验结束时,CK处理土壤累积矿化率(土壤原有有机碳累积矿化量/土壤总有机碳含量)达到1. 64%,而NPK和ST处理较CK处理显著降低了0. 34%和0. 39%(P 0. 05),表明长期施肥对土壤碳有一定的固持作用.长期不同施肥处理土壤对添加外源葡萄糖的响应有所不同,表现出了不同程度的激发效应.随着培养时间的推移,3种处理土壤碳矿化的激发效应由负激发效应逐渐转为正激发效应. 56 d时,ST和NPK处理土壤的负累积激发效应比CK分别显著提高了22. 07和9. 05倍(P 0. 05).结构方程模型分析表明,土壤NH+4-N和DOC含量主要通过影响土壤MBC和MBN含量间接影响土壤累积激发效应,且NH+4-N对土壤累积激发效应有直接的显著负影响.综上所述,长期施肥降低了稻田土壤原有有机碳累积矿化率,有利于增强稻田土壤碳的固持和积累,秸秆还田加化肥效果更加明显.     

氮、硫输入对河口湿地土壤有机碳矿化的实验研究

通过室内培养实验,研究了氮、硫输入对闽江河口湿地土壤有机碳矿化和土壤理化性质的影响.结果表明:NH_4Cl(N1)、NH_4NO_3(N3)、K_2SO_4(S)和NH_4Cl+K_2SO_4(NS1)处理显著促进了湿地土壤有机碳矿化速率(p0.05),较对照分别提高了76.57%、60.09%、83.20%和52.59%,并且不同处理下土壤有机碳矿化速率均表现为随培养时间的增加而递减.氮、硫输入在不同时间对湿地土壤有机碳矿化的影响不尽一致,在前6 d各处理的促进作用最明显.湿地土壤有机碳累积矿化量在不同处理下均表现为随培养时间逐渐增加,其增长速率在培养初始阶段较快,而后逐渐减慢;不同培养时间有机碳累积矿化量在N1、N3、S和NS1处理下与对照处理间均存在显著差异(p0.05).短期培养结束后,N3、NS1处理显著增加了湿地土壤DOC含量(p0.05);N1、N3、NS1和NH_4NO_3+K_2SO_4(NS3)处理均显著增加了土壤NH_4~+-N含量(p0.05);KNO_3(N2)、N3、NS2和NS3处理均显著增加了土壤NO_3~--N含量(p0.05);S、NS1、NS2和NS3处理均显著增加了土壤SO_4~(2-)含量(p0.05).不同处理下湿地土壤Cl-、pH、EC具有微弱的波动变化特征,但在不同处理组间均不存在显著差异(p0.05).多元回归分析显示,DOC、NH_4~+-N和SO_4~(2-)是氮、硫输入处理下影响闽江河口湿地土壤有机碳矿化速率的主要控制因素.     

施肥与地膜覆盖对土壤有机质平衡的影响

用田间长期定位试验法研究了施肥与地膜覆盖条件下玉米连作在壤质棕壤中有机质的矿化、积累和平衡。结果表明，土壤有机质矿化率在０．０１０７～０．０４３８／ａ之间，施肥与地膜覆盖有利于土壤有机质的积累与平衡，并加快有机质矿化；在本试验各施肥处理中土壤有机质均有所积累；在连年稳定施肥条件下，有机肥的施用会明显提高土壤有机质平衡值     

Fate of the veterinary antibiotic 14C-difloxacin in soil including simultaneous amendment of pig manure with the focus on non-extractable residues

The fate of ¹⁴C-labeled difloxacin (¹⁴C-DIF) was studied in time course experiments after application on soil (Ap horizon of silt loam) and amendment of authentic DIF containing pig manure (146 mL kg^?1; 4.17 MBq kg^?1; 0.85 mg kg^?1) or water (124 mL kg^?1; 0.42 MBq kg^?1; 0.09 mg kg^?1) for 56 and 120 days of incubation, respectively.

Mineralization of ¹⁴C-DIF was below 0.2% in both experiments after 56 days or 120 days. In the course of the experiments, portions of extractable radioactivity (Accelerated Solvent Extraction (ASE); acetonitrile-water) decreased to 19–21% depending only little on manure amendment. Non-extractable residues of ¹⁴C-DIF increased to 70–74% after 56 days and 120 days, respectively, and therefore were the main route of ¹⁴C-DIF in soil. According to radioanalytical HPLC and LC-MS/MS, only the parent compound was found in all extracts over the whole time of the experiment. According to fractionation of the non-extractable residues (NER) into particle size fractions, ¹⁴C portions were associated to the water used for fractionation, the silt and clay fractions, whereas no radioactivity was detected in the sand fraction. The majority of ¹⁴C was found within the clay fractions.

Fractionation of humic components showed that radioactivity derived from ¹⁴C-DIF was associated with humic acids, fulvic acids, humins and minerals and very little with soluble, non-humic HCl fraction. The highest portions of radioactivity were found in the fulvic acid fraction. Results obtained by size exclusion chromatography (SEC) of the purified fulvic acids were similar for every sample analyzed. One large portion of ¹⁴C co-eluted with fulvic acids of a molecular weight below 910 g mol^?1. Both fractionation methods demonstrated that the parent compound DIF or initial metabolites were rapidly integrated into humic materials and, thus, were major components of NER.     

滇池表层沉积物氮污染特征及其潜在矿化能力

利用滇池53个表层沉积物样品,研究了其不同形态氮含量及空间分布特征,探讨了滇池沉积物氮潜在矿化能力及其污染特征,以期揭示滇池沉积物氮污染影响因素及沉积物氮释放风险.结果表明:1滇池全湖表层沉积物总氮(TN)平均含量为3 515.60 mg·kg-1,其中草海北部疏挖区、盘龙江入湖口及海口入湖区域含量较高,宝象河河口疏挖区域TN含量相对较低;总有机氮(TON)含量较高,占TN的85.86%;溶解态无机氮(DIN)含量较低,占TN的14.10%,TON与TN空间分布趋势一致,而DIN则不同;与我国其他湖泊相比,滇池沉积物氮含量已经处于较高水平,其污染程度仅低于污染严重的城市湖泊;2滇池全湖表层沉积物潜在可矿化氮(PMN)平均含量1 154.76 mg·kg-1,占TN的32.90%,潜在释放风险较大;其中草海湖区、外海北部盘龙江入湖口湖区、中部洛龙河和梁王河入湖口湖区及白鱼口湖区显著高于其它湖区;目前滇池p H值有利于其沉积物氮矿化,有机质通过释放NH+4-N影响其沉积物氮矿化;污染较重的水域,滇池上覆水氮浓度受其沉积物氮矿化影响较大,而污染较轻水域,则受影响较小.     

季节性温度升高对落干期消落带土壤氮矿化影响

为揭示季节性温度升高对消落带落干期土壤氮矿化的影响,分别采集三峡支流澎溪河消落带上游和下游两个水文断面,155 m(低)、165 m(中)和175 m(高)这3个水位高程表层土壤,结合落干期气温变化特点,在25℃和35℃两个温度下进行恒温培养.结果表明,消落带土壤总氮和硝态氮在上游断面和高水位高程含量更高,而下游和低水位高程含量更低,铵态氮分布与其相反.硝态氮是无机氮的主要存在形式,占无机氮的57.4%~84.7%.相同培养温度下,氨化、硝化、净氮矿化速率均表现为随水位高程增加,随流域断面由下至上而显著增加(P0.05);总体上,在水位高程和流域断面上均表现为:温度升高使硝化速率和净氮矿化速率显著增加(P0.05),而对土壤氨化速率无显著影响(P0.05).     

Variation in soil organic carbon mineralization and microbial community structure induced by the conversion from double rice fields to drained fields北大核心CSCD

Land use conversion is an important factor influencing the carbon gas exchange between land and atmosphere. The effect of land use conversion on soil organic carbon mineralization and microbial function is important for soil organic carbon sequestration and stability. This research studied the effects of land use conversion on soil chemical properties, organic carbon mineralization and microbial community structure after two years of conversion from double rice cropping (RR) to maize-maize (MM) and soybean-peanut (SP) double cropping systems in southern China. The results showed that soil pH significantly decreased by 0.50 (MM) and 0.52 (SP, P = 0.002), and dissolved organic carbon significantly increased by 23%- 35% (P = 0.016). No significant difference was found in soil organic carbon mineralization rate with the land use conversion, though the accumulated mineralization decreased after 13 days of incubation (P = 0.019). Land use conversion from paddy to upland significantly changed soil microbial community structure. The total PLFAs, bacterial, gram-positive bacterial (G+), gram-negative bacterial (G-) and actinomycetic PLFAs decreased significantly (P < 0.05), the ratio of fungal PLFAs to bacterial PLFAs (F/B) increased significantly (P = 0.006). But no significant differences in microbial groups were found between MM and SP. The accumulated mineralization at the beginning period of the incubation were significantly positively correlated with soil actinomycetic PLFAs (P = 0.034). After 13 days of incubation, soil F/B showed a positive correlation with the accumulated mineralization (P = 0.004). However, soil microbial community structure(P = 0.014)and total PLFAs(P = 0.033)showed a positive correlation with the accumulated mineralization after 108 days of incubation. Our results indicated that after conversion from paddy soils to drained soils, soil pH and total nitrogen are the key factors regulating the variations in soil microbial community structure and biomass, and then influencing soil organic carbon mineralization.     

The fate of nitrogen in a moderately alkaline and calcareous soil amended with biosolids and urea

The determination of nitrogen (N) based loading rates for land application of biosolids is challenging and site specific. Over loading may contribute to environmental, agricultural, or human health problems. The objective of this study was to monitor N mineralization and losses in a moderately alkaline and calcareous desert soil amended with either anaerobically digested (AN) or lime-stabilized (LS) biosolids, and irrigated with and without urea enriched water. For Experiment 1, N inputs, leaching and residuals in soil were evaluated in an open soil column system. For Experiment 2, ammonia (NH₃) emissions were evaluated in a closed soil column system. In Experiment 1, AN and LS biosolids increased soil ON (organic N) by three and two fold, respectively. Respective net N mineralization of ON from biosolids alone was 90% and 62% without urea, and 71% and 77%, respectively with added urea. Nitrogen leaching losses and residuals in amended soil did not account for all N inputs into the soil/biosolids system. In Experiment 2, NH₃ emissions were not significantly different among treated soils with or without added urea, except LS amended soil receiving urea. Ammonia losses did not account for unaccounted N in Experiment 1. We concluded that deep placement and rapid mineralization of AN biosolids promoted anaerobic soil conditions and denitrification, in addition to the high denitrification potential of desert soil. LS biosolids showed greater potential than AN biosolids for safe and beneficial land application to desert soils regardless of biosolids placement and the inclusion of N rich irrigation water.