猪、奶牛粪厌氧发酵中Pb的形态转化及其分布特征

畜禽粪便经厌氧发酵后其中的铅（Pb）仍然保留在沼液和沼渣中,阐明此发酵过程中 Pb 的形态转化对沼液和沼渣的后续处理有重要的参考意义。该研究以猪粪和奶牛粪为发酵原料,在中温（37℃±2℃）条件下,采用连续搅拌反应器进行了130 d中试试验,分析了Pb在固相和液相中的分配及其形态转化。研究结果发现：1）与进料相比,猪粪沼液和奶牛粪沼液中总Pb量降低了约70%和19%;2）猪粪沼液和奶牛粪沼液中Pb在液相中的比例为29%和17%,较发酵前降低约17%和58%;3）厌氧发酵后,猪粪沼液中各形态Pb所占比例的大小顺序为：残渣态（35%）>酸溶态/可交换态（34%）>可还原态（24%）>可氧化态（8%）;奶牛粪沼液中为：可还原态（33%）>酸溶态/可交换态（27%）>残渣态（26%）>可氧化态（15%）;4）厌氧发酵后,猪粪沼渣中残渣态和酸溶态/可交换态Pb的比例都极显著增加,奶牛粪沼渣中可氧化态Pb的比例极显著增加。猪粪和奶牛粪厌氧发酵后,适合通过沉淀池或氧化塘削减沼液中的Pb含量;但沼渣中Pb的浓度较大且化学形态发生显著变化,建议还田前进行重金属钝化处理。     

北京大中型沼气工程冬季运行状况及发酵前后物料理化生物特性

为了解北京市大中型沼气工程冬季运行情况及发酵剩余物理化特性,该文实地调查了北京市29座沼气工程冬季运行情况,以调研问卷的形式了解沼气工程运行状况,并采样分析了发酵原料、沼渣和沼液样品的养分含量、粪大肠菌群数、铜、锌、砷、铅等指标。结果表明:北京29座冬季运行的沼气工程中主要以畜禽粪便为原料,其中有20座沼气工程采用猪粪进行厌氧发酵,厌氧消化反应器类型主要是全混式厌氧反应器和升流式厌氧固体反应器,沼气以供周边农户使用为主,沼渣和沼液以农田利用为主,从区域沼气工程运行状况来看,房山区的沼气工程运行状况相对较好,大兴区和顺义区的沼气工程运行状况参差不齐;所调研沼气工程沼渣和沼液的pH值适宜向农田施用,沼渣的EC值相对原料平均下降了56.97%,沼渣有机质和可挥发性固体的质量分数相对原料分别降低了20.99%和27.93%,沼渣的养分质量分数较高,沼液的养分质量浓度较低,沼渣中的粪大肠菌群数和沼液的化学需氧量、粪大肠菌群数整体偏高,有6座沼气工程的砷含量较高。调查结果可为北京市沼气工程冬季运行效果及沼渣沼液资源化利用提供基础数据,促进北京市沼气工程的可持续发展,提高生态和经济效益。     

钝化剂对猪粪厌氧发酵沼渣中As的钝化效果及工艺优化

由于饲料添加剂的使用,规模化养殖场猪粪中重金属残留加剧。为了减少重金属污染,阐明钝化剂对发酵过程中As在沼渣中的含量及其形态转化的影响,为沼渣沼液的安全合理利用提供科学依据,该文以重金属As为研究对象,猪粪为发酵原料,采用厌氧发酵技术,通过正交试验,选取3个因素,每个因素3个水平,采用BCR提取法分析重金属形态。研究不同种类钝化剂(粉煤灰、硅藻土、活性炭),钝化剂的不同添加比例(2.5%,5%,7.5%)及不同发酵温度(25,30,35℃)对猪粪中重金属钝化效果的影响,结果表明:1)猪粪经厌氧发酵后重金属As大多数存留在沼渣中,在沼渣中质量分数范围在5.50~6.56 mg/kg之间;发酵前猪粪中残渣态质量分数为3.38 mg/kg,猪粪厌氧发酵后残渣态含量升高,说明添加钝化剂可以降低重金属As的生物活性,从而有效减少重金属的危害;2)影响重金属As有效态钝化效果的因素主次顺序为钝化剂种类,钝化剂的添加比例及发酵温度;钝化剂种类对As有效态钝化效果有显著的影响,而钝化剂添加比例及发酵温度对有效态钝化效果影响不显著;3)重金属As有效态的钝化效果最好的是添加7.5%的活性炭,发酵温度为30℃的试验处理,其钝化效果可达到62.34%。猪粪厌氧发酵中添加适量的重金属钝化剂,可以在一定程度上降低沼渣中重金属的有效性以及沼渣利用中重金属污染的风险。     

有机无机肥配施对旱地作物养分利用率及氮磷流失的影响

采用2年的田间小区试验,研究猪粪、猪粪堆肥或沼渣沼液与化肥配施对春玉米-小白菜轮作地氮磷径流损失与肥料利用率的影响.结果表明,有机无机肥配施可明显减少旱地氮素流失,NH+-N和NO3--N流失量占总氮流失的比例为49.08％～52.02％,且地表氮素径流损失量随着猪粪堆肥用量的增加而降低;与施纯化肥相比,以20％的猪粪堆肥N与80％化肥N配施可分别降低氮素径流损失28.95％,2年总氮肥利用率提高8.13％.以猪粪堆肥或沼渣沼液与化肥配施可明显降低磷素径流损失,并提高磷、钾肥利用率;与施纯化肥相比,以20％的猪粪堆肥氮或沼渣沼液氮与80％的化肥氮配施可分别减少磷素流失4.74％和2.76％,2年总磷肥利用率分别提高1.06％和2.75％,2年总钾肥利用率分别提高2.62％和11.48％.     

不同沼肥对油菜产量、品质及氮素利用效率的影响

利用温室盆栽试验研究了鸡粪沼肥(鸡粪沼渣、沼液)和牛粪沼肥(牛粪沼渣、沼液)对油菜产量、品质及氮素利用效率的影响。试验共设8个处理,分别为:不施肥(CK),鸡粪沼渣全部做底肥(JZ),鸡粪沼渣做底肥、沼液做追肥(JZ+JY),鸡粪沼液一半做底肥另一半做追肥(JY),牛粪沼渣全部做底肥(NZ),牛粪沼渣做底肥与沼液做追肥(NZ+NY),牛粪沼液一半做底肥另一半做追肥(NY),化肥一半做底肥另一半做追肥(HF),以上处理除空白外均按等氮量施用。研究结果表明,施用鸡粪沼肥比施用牛粪沼肥处理的油菜产量高,JZ、JZ+JY、JY3个处理油菜产量分别为13.8,14.9,14.8 g/盆,分别比牛粪沼肥相同处理(NZ、NZ+NY和NY)高40%,23%和11%。施用鸡粪沼肥处理油菜的硝酸盐含量要比相应施用牛粪沼肥的高,但在Vc含量上差异不显著;鸡粪沼肥氮素利用效率显著高于牛粪沼肥,这可能和鸡粪沼肥比牛粪沼肥速效养分含量高、养分释放快有关系。     

光照强度对猪粪、牛粪厌氧发酵的影响研究

研究光照强度对猪粪、牛粪厌氧发酵的影响,为沼气池的改进、提高产气量提供参考。试验以猪粪、牛粪为发酵原料,设置0、6、12、24h4组光照梯度处理,在恒温35℃和料液总固体质量分数为8%的条件下进行厌氧发酵。结果显示,不同光照强度下同一发酵原料的产气量差别较大,猪粪、牛粪在12h光照条件下的累积产气量分别是0h光照条件下的（黑暗）1.80、2.34倍;相同的光照强度不同发酵原料产气量存在差别,0h光照条件下（黑暗）猪粪的累积产气量为8136mL,牛粪的累积产气量为3282.5mL;光照条件改变发酵料液的理化性质,使累积产气量与发酵料液的碱度、挥发性脂肪酸（Volatile fatty acids,VFA）、pH值、氨态氮的相关性呈动态变化。     

施肥对灌漠土作物产量、土壤肥力与重金属含量的影响

有机物还田是提升土壤肥力的主要措施,但也存在造成土壤金属污染的潜在风险。为查明不同有机物还田对土壤质量及作物产量的影响,本文通过长期定位试验,研究了无肥对照、常规施化肥(氮磷配施)以及70%常规化肥与牛粪、沼渣、污泥、鸡粪、菌渣和猪粪配施对土壤理化性状、有机碳和氮的固存率、氮磷钾活化系数、作物产量及重金属含量的影响。结果表明:牛粪、沼渣、污泥、菌渣、鸡粪和猪粪与70%化肥配施虽作物产量与常规施化肥相似,但6种有机物处理土壤有机质、全氮和碱解氮含量都较常规施化肥处理显著增加,污泥、鸡粪和猪粪处理土壤全磷与速效磷含量较常规施化肥处理显著增加,而且牛粪、沼渣、鸡粪和猪粪处理的速效钾、土壤磷活化系数和土壤钾活化系数较常规施化肥处理也显著提升。牛粪、沼渣、污泥、菌渣、鸡粪和猪粪处理土壤有机碳固存率为36.42%～71.61%,较常规施化肥处理都显著提高;而其氮固存率为6.47%～49.44%,仅有菌渣处理与常规施化肥处理差异不显著,而其他处理较常规施化肥处理显著增加。长期施鸡粪和菌渣处理的土壤铜含量较常规施化肥处理显著增加,增加量分别为4.17mg·kg~(-1)和14.2mg·kg~(-1);而污泥、鸡粪和菌渣处理的土壤锌含量较常规施化肥处理显著增加,增加量分别为13.53 mg·kg~(-1)、22.60 mg·kg~(-1)和49.73mg·kg~(-1)。综上,等有机质(4 500kg×hm~(-2))的牛粪、沼渣、污泥、菌渣、鸡粪和猪粪可替代30%氮磷肥,作物产量不受影响;不同有机物培肥土壤效果为污泥、鸡粪和猪粪优于牛粪和沼渣,而沼渣的培肥效果略差。为保证土壤环境质量稳定不恶化,种植小麦时有机物铜和锌的年携入量应分别低于53.01g×hm~(-2)和221.30 g×hm~(-2),而种植玉米时应分别低于153.40 g×hm~(-2)和347.04 g×hm~(-2)。     

硼泥对猪粪厌氧发酵重金属铬及其光谱特性的影响

随着含有重金属添加剂饲料的使用,规模化养殖场畜禽粪便中重金属含量增加。为减少重金属的危害,该文以猪粪为发酵原料,重金属Cr为研究对象,硼泥为钝化剂,在接种物量为30%、TS为10%、温度为35℃、pH值为7的条件下进行40 d厌氧发酵试验。研究添加2.5%、5.0%、7.5%3种比例的硼泥对猪粪厌氧发酵中重金属Cr的形态变化、有效态钝化效果及发酵前后沼渣光谱特征的影响,采用BCR连续提取法(European community bureau of reference sequential extraction)分析重金属Cr的形态变化,采用傅里叶红外光谱(Fourier transform infrared spectrometer, FTIR)对物料光谱特征的变化进行研究。结果表明:猪粪厌氧发酵过程中添加硼泥有利于重金属Cr从有效态转化为稳定态,当添加7.5%硼泥处理时有效态Cr转化为稳定态Cr的效果较好;猪粪在厌氧发酵过程中添加硼泥能提高重金属Cr的钝化效果,且随着硼泥添加量的增加,钝化效果越好;通过显著性分析,添加7.5%硼泥处理时钝化效果较好,达到63.79%,显著优于猪粪单独发酵和添加2.5%与5.0%硼泥的处理(P0.05);FTIR显示厌氧发酵后,沼渣中酰胺化合物、碳水化合物、蛋白质、脂肪族化合物等有机物分解减少,芳香族等腐殖质增加,且添加7.5%硼泥时有机物腐殖化程度最好。因此猪粪在厌氧发酵过程中添加适量硼泥,可以降低沼渣中重金属Cr的生物有效性,促进有机物转化为腐殖质,研究结果可为减少猪粪中重金属的有效性和提高厌氧发酵质量提供参考。     

畜禽粪便与秸秆厌氧-好氧发酵气肥联产碳氮元素变化研究

传统沼气工程的气肥联产工艺中,厌氧发酵产气与好氧发酵产肥互相独立,产气和产肥周期均较长、有机肥品质差,影响工程的高效运行。为缩短发酵周期、提高产气效率和有机肥品质,该研究将猪粪、鸡粪和秸秆混合进行15和30 d的干法厌氧发酵,将得到的沼渣添加秸秆辅料混合,分别设置65%和70%的发酵物料初始含水率进行15 d的高温好氧发酵,对比分析了不同厌氧-好氧发酵组合对产气和产肥的影响。结果表明:厌氧发酵阶段,混合物料的日产气率自发酵开始后逐渐上升,并在第8天达到最高峰,至第15天降至峰值的50%以下,此时累积产气量达到30 d发酵周期的71%,平均容积产气率达到1.91 m~3/(m~3?d),比发酵30 d平均容积产气率高41.5%。好氧发酵阶段,各处理组碳元素含量持续下降,氮元素含量先下降后增加,所得发酵产物均达到腐熟标准。采用15 d厌氧发酵所获得的沼渣进行好氧发酵,所得发酵产物的电导率、腐殖化程度和发芽指数均优于采用30 d厌氧发酵所获得的沼渣进行好氧发酵所得的发酵产物,同时总有机碳和总氮含量也较其分别提高了6.0%～21.7%和3.0%～10.2%,不同好氧发酵物料初始含水率对发酵产物的品质影响较不明显。因此,采用厌氧、好氧发酵周期均为15 d的组合,可缩短发酵周期、大幅提高产气效率和发酵产物的碳氮营养元素含量,有利于提高沼气工程运行效率和经济效益。     

不同预处理玉米秸秆对猪粪厌氧发酵重金属镉钝化效果

由于养殖饲料中重金属添加剂的使用,使畜禽粪便中重金属含量增加。为减少畜禽粪便重金属的污染,该研究以猪粪为发酵原料,通过添加不同预处理(稀H2SO_4处理、Na OH处理)的玉米秸秆,在温度35℃,接种物量30%,总固体(Total Solid,TS)浓度为10%,pH值为7.0,C/N比为25的条件下进行90 d厌氧发酵试验,旨在研究添加玉米秸秆对重金属Cd钝化效果的影响。结果表明:猪粪厌氧发酵过程中添加玉米秸秆有利于重金属Cd从有效态转化为稳定态;猪粪在厌氧发酵过程中添加玉米秸秆能提高重金属Cd的钝化效果,添加碱处理玉米秸秆钝化效果最佳,为32.38%,添加稀酸处理玉米秸秆的处理钝化效果次之,为32.00%。显著性分析表明,猪粪厌氧发酵过程中添加酸碱处理玉米秸秆对重金属Cd的钝化效果显著高于猪粪单独发酵和添加不经过处理的玉米秸秆(P0.05),而添加稀酸处理秸秆与添加碱处理秸秆重金属钝化效果差异不显著(P0.05);傅立叶红外光谱法(Fourier Transform Infrared Spectrometer,FTIR)显示厌氧发酵后,沼渣中碳水化合物、蛋白质、脂肪族化合物等有机物含量减少,腐殖质含量增加,添加玉米秸秆后有机物腐殖化程度有所提高,且添加碱处理玉米秸秆时有机物腐殖化程度较好,其次是添加酸处理玉米秸秆的处理。因此在猪粪厌氧发酵过程中适量添加经过酸、碱处理的玉米秸秆,可以降低沼渣中重金属Cd的生物有效性。研究结果可为畜禽粪便厌氧发酵重金属钝化提供参考。     

贵州草海耕地土壤与农作物中DDTs和HCHs残留及污染特征

采集草海流域周边成熟期整株农作物及土壤样品,分析测试其中DDTs和HCHs的含量,对比研究了土壤和作物中DDTs和HCHs污染水平及其在作物中富集能力。结果表明：研究区域土壤中HCHs和DDTs残留检出率均为100％,残留范围分别为0．06～16．66μg·kg^-1和0．08-39．77μg·kg^-1,土壤中HCHs和DDTs的残留量均小于国家土壤环境质量一级标准;三种农作物中DDTs、HCHs及∑（DDTs,HCHs）残留量差异显著,HCHs含量最高的是玉米,DDTs和（DDTs,HCHs）最高的是马铃薯;三种农作物中HCHs和DDTs残留的风险系数均为1．1,属于低度风险,农作物中DDTs、HCHs及∑（DDTs,HCHs）的安全指数IFSc均小于1,DDTs和HCHs残留量对三种农作物安全影响的风险是可以接受的。     

我国亚热带山地丘陵区特征及开发中的有关问题

我国亚热带山地丘陵区，山多地少、人口众多、经济基础薄弱，生态环境严重恶化，障碍着区内经济的发展，区内开发应按照以下几个方面搞好：１、协调山－林－地－人的关系；２．调整粮食－林牧－融渔关系；３．改善生产－生活－生态环境。４．提高生态－经济－社会效益。     

红薯对Pb、Cd的吸收累积特征及根际土壤Pb、Cd形态分布研究

为了解土壤在Pb、Cd单一以及复合污染条件下红薯对Pb、Cd的吸收和积累规律,通过盆栽试验对红薯地上部和地下部的生物量和重金属含量进行测定,分析了单一及复合污染土壤中重金属Pb、Cd形态分布特点。结果表明,相对于对照,较低浓度的Pb、Cd能显著促进红薯的生长（P〈0.05）,Pb超过50mg.kg-1、Cd超过3mg.kg-1时,红薯生长受到显著抑制（P〈0.05）,Cd是影响红薯生长的主要因素;随着试验处理浓度的升高,红薯体内重金属含量也随之升高,二者之间存在极显著的相关性（P〈0.01）,Pb、Cd共存对红薯吸收累积Pb、Cd具有明显的交互作用,Pb促进Cd向地上部转移,Cd促进Pb在地下部积累。根际土壤中Pb、Cd以可交换态与碳酸盐结合态为主,二者均占总量的55以上,在复合污染条件下,Pb浓度为50mg.kg-1时其活性系数显著高于其他Pb处理（P〈0.05）,并在很大程度上促进有效态Cd含量的增加。     

百菌清和毒死蜱在大棚番茄中的分布与降解特征

大棚和露地环境下,分别对番茄植株一次性喷洒推荐剂量的百菌清（CHT）和毒死蜱（CHP）,研究喷药后两周内农药在番茄根、茎、叶和果实中分布的持久性及其动态降解规律。实验结果表明,百菌清在大棚番茄中的残留浓度分布呈现为叶片垌果实〉茎〉根;毒死蜱呈现为叶片〉果实垌茎〉根。大棚番茄各部位的最高残留浓度出现时间滞后于喷药时间8~60h;空间浓度分布上表现为大棚中间区域浓度高于两侧,这与棚内的空气对流有关。大棚番茄果实中百菌清和毒死蜱的残留半衰期分别为5.8d和7.2d,明显高于文献报道。     

Degradation and development of peatlands in Peninsular Malaysia and in the islands of Sumatra and Borneo since 1990

In this study, we investigated the extent of peatland degradation and development in Peninsular Malaysia and in the islands of Sumatra and Borneo, in the western part of insular Southeast Asia, since 1990. Furthermore, carbon emissions caused by these land cover changes were estimated in order to evaluate their contribution to global climate change. High resolution Landsat (30 m spatial resolution) and Satellite Pour l'Observation de la Terre (SPOT; 10–20 m) satellite images were used to derive information on land cover in 1990 and 2008. Analysis of land cover changes since 1990 revealed remarkable reduction and degradation of peatswamp forest ecosystems. In less than 20 years, 5·1 Mha of the total 15·5 Mha of peatland had been deforested (11·6 Mha → 6·5 Mha; 75 per cent → 42 per cent) and the great majority of the remaining forests had been selectively logged. Simultaneously, area covered by unmanaged secondary growth ecosystems had doubled to nearly a quarter of all peatlands and industrial plantations had expanded dramatically (0·3 Mha → 2·3 Mha; 2 per cent → 15 per cent). It was conservatively estimated that these changes have caused minimum of 1·5 Gt carbon emissions into the atmosphere since 1990. Currently, peatlands of the study area emit at least 81 Mt of carbon (equivalent to 300 Mt of carbon dioxide) on annual basis due to mere peat decomposition. Thereby, it was concluded that peatland degradation and development in insular Southeast Asia during the past two decades have not only put the existence of Southeast Asian peatswamp forest ecosystems in danger but it has also caused globally significant carbon emissions and created a constant source of carbon dioxide. Copyright © 2010 John Wiley & Sons, Ltd.     

Immobilization and species of heavy metals in soils in the absence and presence of rhizobia

Abstract

The effect of bacterial inoculation of Rhizobium fredii HN01 on the immobilization and speciation of Cu, Zn, and Cd was studied in Red and Cinnamon soil which are typical Chinese soils. The soil was mixed with bacterial suspension for one week followed by an immobilization of each heavy metal for another week. The total binding and fractionation of heavy metals in soils were analyzed. As compared with the control, the retention of total Cu, Zn, and Cd in Red soil increased by 28, 16, and 28%, respectively, in the presence of rhizobia. The amount of exchangeable, NH₄OAc-extractable, Mn oxides-bound and organic matter-bound Cu increased by 23–123%. There were significant decrease of exchangeable Cu and marked increases of NH₄OAc-extractable and Mn oxide-bound Cu in Cinnamon soil with the presence of rhizobial cells, although no changes for the total retention of Cu were observed. The amount of exchangeable Zn in Red soil-rhizobia composite was 20% greater than that of the no-rhizobia soil. Addition of rhizobia also increased exchangeable Cd and specifically-adsorbed Cd by 25 and 93%, respectively, in Red soil. No considerable differences were found for the total immobilization of Zn and Cd as well as their distribution in various solid fractions of Cinnamon soil in the absence and presence of rhizobial cells. In terms of soil components, it is assumed that bacterial biomass had a relatively less impact on the species of heavy metals bound with Fe oxides. Results suggested that the retention and speciation of heavy metals in soil are governed largely by the interactions of bacteria with various inorganic and organic soil constituents. The data are useful in understanding the impact of microorganisms on the behavior, mobility and transformation of heavy metals in soil environments.     

福建茶园土壤六六六和滴滴涕残留水平及来源分析

采用现场采样及室内测试方法,分析了福建茶园土壤中六六六（HCHs）和滴滴涕（DDTs）类有机氯农药（OCPs）的分布、组成和来源。结果表明,∑HCHs和∑DDTs浓度分别为0.251-1.120 ng.g^-1和0.210-2.406 ng.g^-1,属于清洁背景范围;漳浦、福鼎和福州茶园土壤∑OCPs浓度显著高于其他样点。除福州外,其他样点HCH同系物中γ-HCH相对含量最高,占HCHs总量的26.3%-76.3%。DDTs中以o,p′-DDT相对含量最高,为34.7%-60.8%。0-15 cm土壤HCHs和DDTs浓度（分别为0.593 ng.g^-1和1.340 ng.g^-1）均高于15-30 cm（0.451 ng.g^-1和0.862 ng.g^-1）。除福州β-（/α＋γ）-HCH和α-/γ-HCH值较高外,其他样点均较低,表明福州HCHs为历史污染,其他样点均存在HCHs新输入,并可能存在林丹的使用或输入;除福鼎p,p′-DDE/p,p′-DDT值较高外,其他样点均较低,表明除福鼎外其他样点均有DDTs的新输入;o,p′-DDT/p,p′-DDT值均较高,表明可能有大量三氯杀螨醇的使用或输入。     

Expression and inheritance of isozymes in Brassica species and in their interspecific hybrids

Abstract

Gene expression was analysed by means of isozyme electrophoresis for three diploid species Brassica rapa (genome AA), B. nigra (BB), and B. oleracea/ B. oleracea var. alboglabra (CC), three amphidiploids B. juncea (AABB), B. napus (AACC) and B. carinata (BBCC), and in 15 interspecific hybrids from crosses within and between the diploids and the amphidiploids. Five enzyme systems were assessed: glucosephosphate isomerase, leucine aminopeptidase, phosphoglucomutase, 6-phosphogluconate dehydrogenase and malate dehydrogenase. Alleles descending from the diploid species were found both in natural and artificially produced amphidiploids. No effect of reciprocal crosses was observed. i.e., the Brassica isozymes were under nuclear gene control. Mendelian segregation in the F₂ generation from crossing two resynthesized B. napus was observed for the loci glucosephosphate isomerase-2 and phosphoglucomutase-3. Genome-specific alleles were identified for several loci. No alteration in the allelic expression of isozymes was found when assembling all three Brassica genomes in the trigenomic interspecific hybrids. Moreover, trigenomic hybrids were capable of disclosing a silent allele of leucine aminopeptidase from B. carinata, and thus in this study the capability of isozyme analysis for detecting hidden variation was demonstrated.     

Presence and dispersal of infective Frankia in peat and meadow soils in Sweden

Summary Use of the N₂-fixing grey alder, Alnus incana (L.) Moench, as a short-rotation crop for energy production is currently being explored. To evaluate the need for inoculation of alders, the distribution of infective propagules of Frankia in the soil at potential sites for alder plantations was examined. Uninoculated grey alder seedlings were grown in three types of soil. Frequent nodulation was found in a meadow soil which had been free from actinorhizal plants for nearly 60 years, but the alder seedlings failed to nodulate in peat soil from two different bog sites. One of these bogs had been exploited for peat and the surface layer of the peat had been removed, so that the soil samples were taken from deep layers of the peat. At the other site, an area of cultivated peat, there were no infective propagules of Frankia in plots without alders; the infective Frankia was present in plots only where it had been introduced by inoculated alders. There was no detectable air-borne dispersal of Frankia. Instead, water movement might account for the dispersal of Frankia in peat. Although the apparent absence of Frankia in these peat soils necessitates inoculation of alder seedlings before planting out, this makes it possible to introduce and maintain Frankia strains with selected beneficial characteristics, since there is no competition from an indigenous Frankia flora.     

除草剂莠去津和灭草松单用和混用在土壤中的降解

The application of a mixture of bentazone （3-isopropyl-1H-2,1,3-benzothiadiazin-4（3H）-one-2,2-dioxide） and atrazine （6-chloro-N2-ethyl-N4-isopropyl-1,3,5-triazine-2,4-diamine） is a practical approach to enhance the herbicidal effect. Laboratory incubation experiments were performed to study the degradation of bentazone and atrazine applied in combination and individually in maize rhizosphere and non-rhizosphere soils. After a lag phase, the degradation of each individual herbicide in the non-autoclaved soil could be adequately described using a first-order kinetic equation. During a 30-d incubation, in the autoclaved rhizosphere soil, bentazone and atrazine did not noticeably degrade, but in the non-autoclaved soil, they rapidly degraded in both non-rhizosphere and rhizosphere soils with half-lives of 19.9 and 20.2 d for bentazone and 29.1 and 25.7 d for atrazine, respectively. The rhizosphere effect significantly enhanced the degradation of atrazine, but had no significant effect on bentazone. These results indicated that biological degradation accounted for the degradation of both herbicides in the soil. When compared with the degradation of the herbicide applied alone, the degradation rates of the herbicides applied in combination in the soils were lower and the lag phase increased. With the addition of a surfactant, Tween-20, a reduced lag phase of degradation was observed for both herbicides applied in combination. The degradation rate of bentazone accelerated, whereas that of atrazine remained nearly unchanged. Thus, when these two herbicides were used simultaneously, their persistence in the soil was generally prolonged, and the environmental contamination potential increased.