~(137)Cs不同污染水平在大亚湾、秦山、北京土壤植物系统的转移

采用我国大亚湾、秦山和北京土壤 ,模拟核裂变产物137Cs在 0Bq kg土、3 3×1 0 4 Bq kg土、3 3× 1 0 5Bq kg土、3 3× 1 0 6 Bq kg土污染水平时 ,研究土壤 -小麦系统的污染影响与137Cs核素的转移规律。结果表明 :在本试验条件下小麦生长发育处于正常状态 ,未发现对小麦有不良影响 ;小麦分别在 3个污染水平下从试验用的 3种土壤中吸收137Cs的趋势是一致的 ;小麦植株中137Cs的比活度随137Cs施入量相应以数量级增加 ,两者间呈十分显著的正相关 ;137Cs在土壤 -小麦系统中的转移系数随土壤的性质不同而变化 ,在同一污染水平下转移系数在n× 1 0 - 2 ～n× 1 0 0 范围变化 ;在同一种土壤中 ,随土壤污染水平的提高 ,转移系数亦有所提高 ,但变化范围不大 ,对北京土转移系数为 2 2× 1 0 - 2 ～ 5 4× 1 0 - 2 ,大亚湾土转移系数为 1 0 4～ 2 0 9,均在同一数量级内变化 ;对秦山土转移系数为 0 51～ 1 2 1。     

~(14)C-绿磺隆在土壤中的可提态残留、结合残留和矿化研究

本文对14 C 绿磺隆在 7种不同类型土壤中形成结合残留 ( 14 C ER)、可提态残留( 14 C ER)以及矿化为14 C CO2 的规律、影响14 C BR的主要因子及其在腐殖质中的分布规律等进行了研究。结果表明 :( 1 ) 14 C 绿磺隆在土壤中形成的14 C ER含量与土壤pH呈显著正相关 ,与土壤粘粒和有机质含量呈显著负相关 ,14 C ER中的绿磺隆母体化合物的消减满足一级反应动力学方程 ,其在 7种土壤中的半减期分别为 1 3 0～ 1 3 3 3d。pH是影响绿磺隆母体化合物降解的主要因子 ;( 2 ) 14 C 绿磺隆在 7种土壤中的14 C BR含量与土壤pH呈显著负相关 ,并与土壤粘粒含量呈显著正相关 ,土壤pH是14 C 绿磺隆在土壤中形成BR的主要影响因子 ;( 3 ) 14 C 绿磺隆形成的14 C BR主要分布在富啡酸和胡敏素中 ;14 C BR分布在胡敏酸中的相对百分比约为 2 % ,在14 C 绿磺隆BR的形成过程中 ,富啡酸的作用 >胡敏素 胡敏酸 ;( 4) 14 C 绿磺隆在 7种土壤中的14 C BR含量 ,在培养 2 0d内均随时间而快速增加 ,2 0d后变化量较小。 7种土壤中的14 C BR含量最大值分别占引入量的 53 5%、40 9%、3 7 8%、1 6 4%、42 5%、41 0 %和 3 1 3 % ;( 5)培养 90d内 ,14 C 绿磺隆通过三嗪杂环开环矿化为14 CO2 的量约占引入量的 4%～9% ,而土壤 1表明14 C     

土壤微生物生物量碳的表观周转时间测定方法

土壤微生物生物量碳周转对土壤有机质和养分循环起着决定作用。本研究建立了土壤微生物生物量碳周转时间的测定方法。培养条件下 (2 5℃、10 0 %湿度 ) ,加入14 C标记葡萄糖标记土壤微生物生物量碳 ,在 10 0d培养期内 ,每隔 2 0d测定一次14 C标记微生物生物量碳 (14 C BC) ,采用一级热力学方程拟合测定期内 (2 0～ 10 0d) 14 C BC 的周转速率常数 (k) ,由此计算土壤微生物生物量碳的表观周转时间。测定的 5个土壤在培养条件下微生物生物量碳的周转时间为 93～ 4 0 0d ,根据培养温度和实际田间年平均温度推算得到田间条件下土壤微生物生物量碳的周转时间为 1 0～ 4 1a。其主要影响因子为土壤质地 ,土壤利用方式的影响较小。土壤微生物生物量碳的周转时间能较好地反映土壤微生物生物量的周转状况及其与土壤有机质的周转和积累的关系。     

秸秆碳的田间原位分解和微生物量碳的周转特征

应用14 C示踪技术研究了杂交狼尾草秸秆在稻麦轮作田中为期 1年的原位分解。结果表明 :秸秆用量对其分解率影响甚微 ,1年后秸秆C分解了 72 %左右 ,分解速率常数为 2 7× 1 0 - 3d- 1,但秸秆用量的多少与土壤原有碳的分解和土壤有机碳平衡密切相关。黄棕壤原有C年分解率为 5 4 5 %～ 6 0 7% ,分解速率常数在 1 0 4× 1 0 - 4～ 1 1 8× 1 0 - 4d- 1之间。随秸秆用量增加 ,黄棕壤原有C分解率和分解量均增加 ,土壤有机碳的亏缺减少。微生物量14 C占加入秸秆14 C的 3 79%～ 1 0 63% ,占土壤残留14 C的 1 2 2 7%～1 7 4 3% ,其大小变化及减少程度均较微生物量12 C显著。微生物量12 C约为微生物量14 C的 0 74～ 3 85倍 ,说明大多数情况下 ,土壤原有C仍是土壤微生物活动所需能量和养分的主要来源。微生物量14 C的周转率在 1 1 0～ 1 1 8a- 1之间 ,微生物量12 C的周转率在 0 97～ 1 0 6a- 1之间。增加秸秆用量可加快土壤微生物量C的周转速度 ,反过来微生物量C周转速度的加快又加速了秸秆C和土壤原有C的分解。土壤原有C和秸秆C的分解进程与微生物量12 C和微生物量14 C的动态变化趋势一致 ,说明有机碳分解的快慢是土壤微生物活动强弱的外在表现。     

土壤中~(14)C-甲磺隆的结合残留及其在腐殖质中的分布规律

实验室培养条件下 ,研究了14 C 甲磺隆在 7种不同类型土壤中形成结合残留( 14 C BR)的规律、主要影响因子及14 C BR在腐殖质中的动态分布规律等。结果表明 :( 1 ) 14 C 甲磺隆在 7种土壤中形成的14 C BR含量在培养初期的 2 0d内与土壤pH呈显著负相关且与土壤粘粒含量呈显著正相关 ;而 2 0d后 ,14 C BR含量只与土壤pH呈显著负相关。土壤pH是14 C 甲磺隆在土壤中形成BR的主要影响因子。14 C -甲磺隆在各类土壤中的14 C BR的最大值分别占引入量的 48 5%、46 5%、52 6%、1 9 3 %、49 7%、42 0 %和 46 5% ;( 2 )在整个培养试验过程中 ,14 C 甲磺隆在 7种不同类型土壤中的14 C BR ,主要分布在富啡酸和胡敏素中 ,前者中的相对百分比大于后者 ,而在胡敏酸中的相对百分比较小。土壤中14 C 甲磺隆BR的形成过程中 ,富啡酸的作用 >胡敏素 胡敏酸     

长期施肥对土壤生物活性有机碳库的影响

采用土壤培养实验方法,研究了25年施肥对平凉黑垆土土壤生物活性有机碳库(C0)的影响。结果表明:土壤生物活性有机碳库(C0)以施用有机肥处理显著增大,其中以S+NP处理最高,达1071.00μg/g,M+NP处理为940.85μg/g,M处理为776.90μg/g,分别比CK增加1.86倍、1.51倍和1.07倍,单施N肥处理对土壤生物活性有机碳库影响不大,为399.10μg/g,仅比CK增加6.4%,NP配合处理为621.60μg/g,比CK增加65.76%。增施有机肥料可明显增大土壤生物活性有机碳库(C0),NP化肥配合施用也有良好效果,N肥单施无明显作用。土壤生物活性有机碳库(C0)占土壤总有机碳(TOC)的百分比为2.70%～6.34%,生物活性有机碳库的周转速率(K)为0.0223～0.0301d-1,生物活性有机碳库在土壤中的半周转期(T1/2)为22.55～31.09d。土壤生物活性有机碳库(C0)与土壤全氮呈极显著性正相关,与总有机碳(TOC)呈显著性正相关。     

红壤微生物生物量C周转及其研究

采用14 C底物标记技术测定了三种不同质地 (红砂土菜地、黄筋泥桔园和茶籽园 )的红壤微生物生物量C的周转期。结果表明 ,在 2 5℃、5 0 %田间持水量培养条件下 ,三种红壤微生物生物量C的周转期分别为 80天、1 39天和 1 70天。周转期与粘粒含量关系较为密切 ,砂质土壤的周转期较粘粒土壤短 ,提示砂质土壤有机质易被微生物降解 ,有利于养分的迅速释放 ,而粘粒土壤则更有利于养分的持留。周转期与利用方式、pH以及有机质含量无明显相关。红壤微生物生物量C周转期总体上较报道的其他类型土壤微生物生物量C周转期短 ,表明热带—亚热带地区酸性红壤有机质和养分周转相对较快 ,这有可能是造成红壤养分贫瘠的一个原因。根据周转期估算 ,通过微生物年周转的C量 (即年流通量 )为微生物生物量C的 2倍以上     

质子对小麦的诱变效应及作用机理研究 Ⅰ.质子对小麦的诱变效应

用 2MeV～ 9MeV 7个能量 ,5C～ 1 60C 1 2个剂量的质子处理 5个品种 ,研究质子对小麦的诱变效应。结果表明 ,M1代的生物损伤随剂量的提高而加重 ,在一定能量范围内 ( 6MeV以下 ) ,随能量的增加而加大 ,超过一定能量 ,生物损伤有所减轻 ;M1代较易出现γ辐照中少见的叶绿素条状缺失损伤。M2 代诱变效果显著 ,突变谱宽 ,有益突变频率明显高于γ射线 ,较易诱发早抽穗性状变异 ;明确诱变小麦的适宜能量为4MeV ,适宜剂量为 1 4× 1 0 10 ～3 7× 1 0 10 P cm2 。     

水稻土中广灭灵残留动态及降解影响因子的研究

对水稻土中广灭灵残留消解动态及降解影响因子研究结果表明 ,广灭灵在 4种水稻土中降解符合 1级动力学方程C =C0 e-kt,其降解半衰期为 5 7～ 2 2 0d。广灭灵降解以微生物降解为主 ,土壤灭菌处理大大降低广灭灵降解速率 ,土壤理化性质、温度、湿度、pH值是影响广灭灵降解的重要因素。广灭灵降解速率与不同类型水稻土有机质含量呈显著负相关关系 ,相关系数为 - 0 8336。随温度上升而广灭灵降解有加速趋势 ,但常温 2 5℃时广灭灵降解速率高于 35℃处理 ,增加土壤湿度及施用石灰增加土壤 pH值均加快广灭灵降解速率     

壳聚糖电离辐射降解的研究

利用60 Coγ射线辐照技术 ,研究了壳聚糖辐射降解后产物分子量、粘度、微量元素与辐照剂量之间的关系。结果表明 ,1 0～ 45 0kGy的辐照剂量可以使壳聚糖的相对分子量由 8 2× 1 0 5降至 1 0× 1 0 3 左右 ,降解效果明显 ,最适辐照降解剂量为 47 75kGy ;经 1 0～ 45 0kGy剂量辐照 ,壳聚糖粘度减小 ,分子量和粘度均随辐照剂量的增大而降低。     

Short-term decomposition of <Superscript>14</Superscript>C-labelled glucose in a fluvo-aquic soil as affected by lanthanum amendment

In this study, we investigated the effects of lanthanum (La), one of the rare earth elements (REEs), on microbial biomass C as well as the decomposition of ¹⁴C-labelled glucose in a fluvo-aquic soil in 28 days. The soil was collected from the field plots under maize/wheat rotation in Fengqiu Ecological Experimental Station of Chinese Academy of Sciences, Henan Province, China. Application of La decreased soil microbial biomass C during the experimental period, and there was a negative correlation (P < 0.01) between microbial biomass and application rate of La. La increased microbial biomass ¹⁴C after ¹⁴C glucose addition, and the increase was significant (P < 0.05) at the rates of more than 160 mg kg⁻¹ soil. La slightly increased ¹⁴CO₂ evolution at lower rates of application but decreased it at higher rates 1 day after ¹⁴C glucose addition, while there was no significant effect from days 2 to 28. For the cumulative ¹⁴CO₂ evolution during the incubation of 28 days, La slightly increased it at the rates of less than 120 mg kg⁻¹ soil, while significantly decreased (P < 0.05) it at the rate of 200 mg kg⁻¹ soil. The results indicated that agricultural use of REEs such as La in soil could decrease the amount of soil microbial biomass and change the pattern of microbial utilization on glucose C source in a short period.     

添加^14C标记稻草对喀斯特典型土壤有机碳矿化的影响

为了研究有机物质对喀斯特地区典型土壤有机碳积累与转化的影响,采集两种喀斯特典型土壤（棕色石灰土、黑色石灰土）和一种对照土壤（红壤）的表层土壤（0～15cm）,设置不添加外源物质（CK）和添加14C标记的稻草（T1）的处理,进行为期100d的土壤培养试验及矿化试验。测定并分析了这3种典型土壤类型的微生物生物量碳（MBC）表观周转时间和田间周转时间、外源有机物质对土壤原有有机碳的激发效应以及CO2释放量。结果表明：MBC表观周转时间和田间周转时间依次分别为（71±2）d、（243±20）d、（254±45）d和0.29、1.0、1.04a。添加标记的14C有机物质后,土壤原有有机质的激发效应大小依次为红壤〉棕色石灰土〉黑色石灰土。在相同条件下,红壤不利于土壤有机质的累积,而棕色石灰土和黑色石灰土有利于土壤有机质的累积。     

土壤水分状况对14C标记秸秆的腐解及腐殖质中碳素分布的影响

¹⁴C-tracer technique and closed incubation method were used to study straw ¹⁴C decomposition and distribution in different fractions of newly formed humus under different moisture regimes. Decomposition of straw ¹⁴C was faster during the initial days, and slower thereafter. Decay rate constants of straw ¹⁴C varied from 3.29 × 10^-3 d^-1 to 7.06 × 10^-3 d^-1. After 112 d incubation, the amount of straw ¹⁴C mineralized was 1.17~1.46 times greater in submerged soils than in upland soils. Of the soil residual ¹⁴C, 9.08%~15.73% was present in humic acid (HA) and 31.01%~37.62% in fulvic acid (FA). Submerged condition favored the formation of HA, and HA/FA ratio of newly formed humus (labelled) was greater in submerged soils than in upland soils. Clay minerals affected the distribution of straw ¹⁴C in different humus fractions. Proportion of ¹⁴C present in HA to ¹⁴C remaining in soil was greater in Vertisol than in Ultisol.     

The initial rate of C substrate utilization and longer-term soil C storage

The initial reaction of microbial transformation and turnover of soil carbon inputs may influence the magnitude of longer-term net soil C storage. The objective of this study was to test the merit of the hypothesis that the more rapid substrates are initially utilized, the longer the residual products remain in the soil. We used simple model C compounds to determine their decomposition rates and persistence over time. Pure ¹⁴C compounds of glucose, acetate, arginine, oxalate, phenylalanine, and urea were incubated in soil for 125 days at 24°C. Total respired CO₂ and ¹⁴CO₂ was quantitatively measured every day for 15 days and residual soil ¹⁴C after 125 days. The percent ¹⁴C remaining in the soil after 125 days of incubation was positively and significantly correlated with the percent substrate utilized in the first day of incubation. The ¹⁴C in the microbial biomass ranged from 4–15% after 15 days and declined through day 125, contributing significantly to the ¹⁴C that evolved over the longer time period. Priming of ¹²C soil organic matter (SOM) was negative at day 3 but became positive, reaching a maximum on day 12; the total increase in soil C from added substrates was greater than the primed C. The primed C came from ¹²C SOM rather than the microbial biomass. This data supports the concept that the more rapidly a substrate is initially mineralized, the more persistent it will be in the soil over time.     

Fungal biomass production and turnover in soil estimated using the acetate-in-ergosterol technique

We report the first attempt to estimate fungal biomass production in soil by correlating relative fungal growth rates (i.e., acetate incorporation into ergosterol) with fungal biomass increase (i.e., ergosterol) following amendments with dried alfalfa or barley straw in soil. The conversion factor obtained was then used in unamended soil, resulting in fungal biomass productions of 10-12 μg C g⁻¹ soil, yielding fungal turnover times between 130 and 150 days. Using a conversion factor from alfalfa-treated soil only resulted in two times higher estimates for biomass production and consequently lower turnover times. Comparing fungal biomass production with basal respiration indicated that these calculations overestimated the former. Still, the turnover times of fungal biomass in soil were in the same range as turnover times estimated in aquatic systems. The slow turnover of fungal biomass contrasts with the short turnover times found for bacteria. The study thus presents empirical data substantiating the theoretical division of bacteria and fungi into a fast and a slow energy channel, respectively, in the soil food web.     

Zinc effects on soil microflora and glucose metabolites in soil amended with 14C-glucose

Summary The effects of zinc added to a diluvial sandy clay loam soil on its microflora and the metabolic products of amended glucose in the soil were investigated, and its influences on both biological and chemical turnover are discussed.Changes in the soil microflora were followed by counting the microbes and measuring their contributions to soil respiration. The transformations of ¹⁴C-glucose products were traced in five divided fractions.Amended glucose was readily assimilated into microbial tissues and transformed to metabolites in the control soil. Within the initial 24 h of the incubation, most of the glucose was decomposed and about 40% of the substrate evolved as carbon dioxide. This primary metabolism was attributed to the bacterial population, and the subsequent secondary metabolism was associated with fungal growth rather thanbacteria. On the other hand, zinc (1000 g/g) added as chloride prolonged the primary metabolism of glucose and a large part of the incubation period for 96 h was occupied by this metabolism, which was mostly dependent on the fungal population. Viable bacterial number noticeably within the first 24 h of the incubation. During the course of the subsequent incubation, however, this number increased and the selection for zinc tolerance was suggested.     

Measurement of protein synthesis by soil bacterial assemblages with the leucine incorporation technique

The incorporation of [¹⁴C]-leucine into protein by soil organisms was measured both in soil slurries and for bacteria extracted from soil by homogenization-centrifugation. The result was compared with thymidine incorporation. Using a soil slurry, 9.1×10^-10 mol leucine h^-1g^-1 dry weight of soil was incorporated into protein, with a calculated leucine: thymidine ratio (mol:mol) of about 34. Non-specific labelling of macromolecules other than protein was observed with both the soil slurry and the homogenization-centrifugation method. With the latter, 46.5% of the total incorporation was found in the protein fraction (hot-acid insoluble). The incorporation of leucine was linear with time for at least 4 h for extracted bacteria. Even at 2000 nM, [¹⁴C]-leucine did not saturate incorporation into protein. Isotope dilution plots indicated that with 750 nM leucine, the degree of participation of the labelled substance in protein synthesis was 0.59. With this value, the ratio of leucine:thymidine incorporation into total macromolecules was calculated as 41 for extracted bacteria. On the basis of incorporation into protein (leucine) and incorporation into DNA (thymidine) only, the leucine:thymidine ratio was calculated as 117. The mean turnover time of bacteria at 22°C, calculated using conversion factors from published studies and leucine incorporation into protein of extracted bacteria, was 4.3 days.     

Photoassimilate partitioning in hypernodulation mutant of soybean (Glycine max (L.) Merr.) NOD1-3 and its parent williams in relation to nitrate inhibition of nodule growth

Nodule growth of a hypernodulating soybean (Glycine max (L.) Merr.) mutant line NOD1-3 was compared to that of its wild-type parent cv. Williams from 14 to 18 days after planting (DAP) in the absence of nitrate treatment (hereafter referred to as “0 mM treatment”) or with 5 mM nitrate treatment. The growth rate determined by increase in the diameter of the nodules was relatively lower in the mutant NOD1-3 than that of the parent Williams under nitrogen-free conditions (0 mM nitrate). The inhibition of nodule growth by 5 mM nitrate started at 1 d after the onset of the nitrate treatment in Williams, while the inhibition did not occur before the application of the nitrate treatment for 2 d in NOD1-3. The nodule growth was completely inhibited after 2 d in Williams and after 3 d in NOD1-3 during the 5 mM nitrate treatment period. After 4 d of 5 mM nitrate treatment, the nodule dry weight decreased by 22% in NOD1-3 and by 58% in Williams, respectively. The treatment with 5 mM nitrate decreased the acetylene reduction activity (ARA) in NOD1-3 by 60% per plant and by 50% per nodule g DW and these parameters were less sensitive to the treatment than those in Williams in which the inhibition rate was 90% per plant and 80% per nodule g DW. These results indicate that NOD1-3 is partially nitrate-tolerant in terms of individual nodule growth as well as total nodule dry weight and Nz fixation activity. A whole shoot of Williams and NOD1-3 plants was exposed to ¹⁴CO₂ for 120 min followed by 0 or 5 mM nitrate treatment for 2 d, and the partitioning of the photoassimilates among the organs was analyzed. Under 0 mM nitrate treatment, the percentages of the distribution of ¹⁴C radioactivity between the nodules and roots were 63 and 37% in Williams and 89 and 11% in NOD1-3. Under the 5 mM nitrate conditions, the percentages of the distribution of ¹⁴C between the nodules and roots changed to 14 and 86% in Williams and 39 and 61% in NOD1-3, respectively. These results indicated that the hypernodulating mutant NOD1-3 supplied a larger amount of photoassimilates to the nodules than to the roots under nitrogen-free conditions, and that the nitrate depression of photoassimilate transport to the nodules was less sensitive than that of the parent line.     

Effects of trifluralin and metabolites on the decomposition of selected substrates by soil microorganisms

Summary The effects of trifluralin and 12 of its soil-formed metabolites on the decomposition of radio-labelled glucose, protein and cellulose were determined, using ¹⁴CO₂ evolution from soil as a measure of decomposition. Trifluralin increased ¹⁴C-glucose mineralization rates, but these increases could be eliminated by adding N. Trifluralin had no inhibitory effect on the mineralization of protein or cellulose, but five of the metabolites inhibited glucose mineralization. None of the trifluralin metabolites affected protein mineralization. Seven trifluralin metabolites increased the rate of cellulose mineralization when applied at rates exceeding those that would be expected in soil. After considering the rate of metabolite application and the magnitude of the responses observed these compounds are expected to have no major effects on the microbial decomposition processes in soil.