Measurement of the bioconcentration factors of pesticides by freshwater fish and their correlation with physicochemical properties or acute toxicities

The bioconcentration factors (BCF) for 15 pesticides by a freshwater fish (topmouth gudgeon) were measured under continuous flow conditions in water containing 5 to 20 μg litre^?1 of each pesticide at the equilibrium condition. A significant correlation was found between the BCF by the fish and the water solubility of the pesticide or its partition coefficient (PC) between octan-1-01 and water. Moreover, a significant correlation was also found between the BCF by topmouth gudgeon and the acute toxicities to carp, rainbow trout and water flea. It would therefore appear that the bioconcentration potential of a pesticide by a fish may be predicted from knowledge of its solubility or PC, and that the acute toxicity of a pesticide to a fish may be predicted from knowledge of the BCF.     

Spatial correlation between weed species densities and soil properties

The spatial cross‐correlation between weed species densities and six soil properties within fields was analysed using cross‐semivariograms. The survey was carried out in three successive years in two fields. The most consistent relationship between weed species density (numbers m^?2) and soil properties was negative cross‐correlation between the density of Viola arvensis Murray and clay content. This correlation was found in both fields; however, the range of spatial dependence varied between fields. In one of the fields, the density of Lamium purpureum L. was positively cross‐correlated with the phosphorus content in the soil in all years. The density of Veronica spp. and Poa annua L. was negatively cross‐correlated with pH in all three years. Other spatial cross‐correlations that were found in this study were inconsistent over time or field site. The densities of some of the weed species were spatially cross‐correlated with more than one soil property. The results showed that the range of spatial dependence varied not only between fields, but also between weed species and soil properties, as well as between years. This study indicates that the weed pattern is field‐specific and that the spatial variation in soil properties within a field is one of several factors affecting weed patchiness.     

Spatiotemporal variation and correlation of soil enzyme activities and soil physicochemical properties in canopy gaps of the Tianshan Mountains,Northwest China

The study of the heterogeneity of soil enzyme activities at different sampling locations in canopy gaps will help understand the influence mechanism of canopy gaps on soil ecological processes. In this paper, we analyzed the spatiotemporal variation of soil enzyme activities and soil physicochemical properties at different sampling locations (closed canopy, expanded edge, canopy edge, gap center) in different sampling time (December, February, April, June, August, and October) on the northern slope of the Tianshan Mountains, Northwest China. The results showed that soil catalase, cellulase, sucrase, and acid phosphatase activities were relatively high from June to October and low from December to April, and most of soil enzyme activities were higher at closed canopy than at gap center. Soil urease activity was high during December-February. The soil temperature reached the highest value during June-August and was relatively high at gap center in October, December, and February. Soil water content was significantly higher in December and April than in other months. Soil bulk density was higher at gap center than at closed canopy in December. Soil pH and soil electrical conductivity in most months were higher at closed canopy than at gap center. Soil organic carbon, soil total nitrogen, and soil total phosphorus were generally higher at gap center than at closed canopy. Furthermore, sampling time played a leading role in the dynamic change of soil enzyme activity. The key factors affecting soil enzyme activity were soil temperature and soil water content, which were governed by canopy gaps. These results provide important support for further understanding the influence mechanism of forest ecosystem management and conservation on the Tianshan Mountains.     

生物质炭及炭基硝酸铵肥料理化性质研究

通过元素分析、灰分测定、环境扫描电镜、红外光谱及土壤水分特征曲线测定,较系统分析和评价竹炭和木炭两种生物质炭及生物质炭基硝酸铵的部分理化性质、形貌结构及土壤水分吸持特征,以为生物质炭作肥料缓释载体应用提供参考。研究表明:实验所用生物质炭含碳量高达60%以上,并含有N、H、O等元素。竹炭比木炭富含灰分,而竹炭比木炭负载硝酸铵量低,其分别约为8%和18%。生物质炭基硝酸铵呈无定形、多孔状结构,基本保持生物质炭的微观形态。生物质炭与氮肥复合是靠物理吸附相结合的,复合中未发生化学变化。供试生物质炭呈碱性,吸附氮肥后pH值降低。两种生物质炭对土壤持水容量或能力有一定的改善作用,其改善程度与土壤质地有关。传统工艺竹炭、木炭也可作肥料养分的载体。     

Studies on BHC isomers and related compounds: Penetration and translocation of BHC isomers in the cockroach and their correlation with physicochemical properties

Penetration of BHC isomers through the integument of Periplaneta americana (L.) is a composite of several first-order events. Translocation and accumulation in the head appears to be a zero-order function. The correlation of some of the biological properties with physicochemical properties such as partition coefficients and binding constants are discussed.     

玉米秸秆还田保护性耕作对产量及土壤理化性状影响的灰色关联分析

通过在甘肃中部干旱区设置的农艺农机结合持续秸秆还田保护性耕作试验,研究了玉米增产量(率)与年限的关系及与土壤理化性状的灰色关联度,并对与有机质关联度高且相关关系显著的肥力因子进行了回归分析.结果表明:秸秆还田保护性耕作2～6a的增产率为2.63%～6.08%.土壤理化性状与增产量的灰色关联序为有机质(0.7456)＞全...     

生物炭对土壤理化性质和玉米生长的影响

以玉米品种'利禾1号'为试验材料,设计6个施肥处理,分别为空白对照(CK,不施肥);常规施肥处理(T1,N:P2O5:K2O=27:12:6);在常规施肥处理基础上减氮20％并分别增施生物炭,生物炭施用量分别为2.25(T2)、4.50(T3)、6.75(T4)、9.00 t·hm-2(T5),研究生物质炭基施对宁夏扬...     

Effects of the herbicide prometryn on the physicochemical properties of artificial model membranes

Several derivatives of 1,3,5-triazine (eg atrazine, prometryn) are effective herbicides and have been extensively used in agriculture. A study of prometryn (Prom)-phospholipid (PL), with different charges, was carried out by means of calorimetric and spectroscopic techniques. The Prom-dipalmitoylphosphatidylcholine (DPPC) and Prom-dipalmitoylphosphatidic acid (DPPA) water suspensions systems at pH values ranging from 5 to 9 were investigated. The results show that Prom does not significantly perturb the hydrophobic core of the lipid bilayer and suggest that the herbicide localizes near the glycerol backbone of the lipid, perturbing the environment of the carbonyls of the two ester groups. At pH 5 the vibrational band attributable to N–H stretch of Prom disappears thus suggesting that the absorption into the bilayer modifies the physicochemical properties of the herbicide. The two PL considered behave similarly and the effect of the charge is not noticeable. The strength of the Prom-PL interaction decreases with decreasing pH. © 1999 Society of Chemical Industry     

小麦叶锈菌越夏与气象因子相关性初步分析

小麦叶锈病是一种严重威胁小麦安全生产、依靠气流传播的真菌病害,近年来发生呈逐年加重趋势。为明确气象因子对小麦叶锈菌越夏的影响,本研究通过对全国698个气象站点7月-8月最热10 d的日均温和平均日最高气温进行回归分析,对7月-8月0 cm平均地温、平均风速、平均降水量、平均日照时数和平均相对湿度进行空间插值,提取了93个小麦叶锈菌越夏调查点的气象数据,再与调查点小麦叶锈菌能否越夏进行相关性分析,结果显示小麦叶锈菌越夏与7月-8月最热10 d日均温和最热10 d平均日最高气温之间存在极显著相关性(P<0.01),与其他气象因子相关性不显著(P> 0.05),结果为小麦叶锈病的越夏区划奠定了基础。     

A review of the interactions between multiple insecticide resistance loci

Insecticide resistance is an ever escalating problem worldwide in many pest populations and numerous cases of insecticide resistance are polygenic. Therefore, it is important to investigate the types of interactions that occur between insecticide resistance loci as this will dictate the level of resistance (and effectiveness of a chemical control strategy). Interactions also play a role in the evolution and/or maintenance of multigenic resistance in the field. Given that a limited number of mechanisms confer resistance, it might be possible to establish general rules for interactions between mechanisms. Several variables might dictate the type of interaction, such as the nature of the resistance mechanisms, genotype, etc. Interactions can be synergistic, antagonistic or additive. Based on this literature review, the most common interaction of multiple homozygous resistance loci is synergistic and additive when loci are heterozygous. When one locus is homozygous and the other locus is heterozygous the most common interaction was synergistic, although very few studies have examined this type of interaction. Possible factors that drive these interactions, exceptions to the trends, and future research needs are discussed.     

不同旱作节水灌溉条件对土壤理化性质及水稻产量的影响

为探索更为适合的水稻节水灌溉方式,于2017—2019年在宁夏暖泉农场开展大田试验,采用三因素对比设计,设置3种不同水稻节水灌溉方式(保墒旱直播MDDS、播后上水旱直播IDFS及覆膜滴灌旱作FMDI),研究了不同节水灌溉方式对水稻土壤理化性质及产量的影响。结果表明：FMDI分蘖期0～10 cm土层日平均地温3 a平均较IDFS和MDDS增加1.7℃(P<0.05);FMDI节水效果明显,在灌溉水平为80%田间持水量条件下,依然可以保持较高的土壤含水量(3年分别为20.1%、19.9%及20.3%);MDDS和IDFS土壤紧实度分别比FMDI平均高出1.74倍、1.77倍;FMDI处理连续3 a土壤有机质、全氮、全磷和全钾较其他2种耕作处理均有显著增加;FMDI处理有显著增产作用,其3 a经济产量和收获指数均最高,与MDDS相比,FMDI的水分利用效率3个年份增幅分别为54.0%、60.0%和56.0%。综上可知,覆膜滴灌旱作(FMDI)方式为适宜该地区水稻种植的蓄水保墒、增温稳温、培肥地力和高产高效的土壤耕作覆盖措施。     

农田耕种对土壤酶活性及土壤理化性质的影响

通过分析连续耕种5、10、15、20、30年农田土壤的4种酶活性及土壤理化性质,得出结论：随着种植年限的增加,灌溉、耕作、施肥等人类生产活动改变了酶在各土层间的活性格局。过氧化氢酶活性和蔗糖酶活性随年限的增加总体趋势增加,有机质和土壤水分变化类似,一致表现出＂N＂形的变化趋势,脲酶活性和磷酸酶活性呈现＂M＂形的相似变化...     

银川平原沟渠边坡土壤理化性状空间分异特征

基于银川平原沟渠边坡植物群落的生态序列更替,在沟渠边坡从堤坝顶部到坡底设置了A区、B区和C区3个样区,通过野外调查采样、实验室分析,结合经典统计学方法,对沟渠边坡土壤含水量、全盐、pH值、有机碳(SOC)、碱解氮(AN)、有效磷(AP)等的空间分布特征及其与植被的相互反馈机制进行了探究。结果表明:银川平原沟渠边坡土壤理化性状具有明显的空间异质性;A区、B区、C区的土壤含水量依次呈现递增变化规律;A区、B区、C区的pH值分别介于8.18~10.37、8.29~9.79、8.08~9.75之间,盐碱化程度较高;土壤全盐表聚效应显著,其中以B区0~10 cm土层富集效应最显著(P0.05),形成了明显的"盐带";SOC、AN、AP分别在B区的0~30、0~30、0~10 cm土层富集效应显著(P0.05),形成了明显的"肥区"。土壤理化性状间的相互作用直接或间接地影响了土壤理化性状的空间差异,其中,土壤含水量的变化是植物群落更替效应的本源,进而影响了土壤理化性状。土壤资源的空间异质性和植物群落的生态序列梯度相伴而生、相互制约,共同维护着银川平原沟渠湿地的植物多样性和绿洲生态系统的稳定。     

助剂对氯虫苯甲酰胺药液理化性质及在玉米叶片上沉积分布的影响

为选择用于植保无人机作业的喷雾助剂,利用全自动张力仪和接触角测量仪测定添加4种不同喷雾助剂后0.5%氯虫苯甲酰胺药液的表面张力及在玉米叶片上的接触角,应用大疆T20型植保无人机进行田间喷雾,分析添加4种喷雾助剂对玉米冠层不同位置雾滴密度、雾滴覆盖率和雾滴沉积量的影响。结果显示,添加迈飞和Agrospred 910喷雾助剂后,药液的表面张力分别较未添加助剂时显著降低19.6%和30.1%;不同喷雾助剂对药液在玉米叶片上接触角的影响各不相同,添加Agrospred 910助剂后液滴接触叶片60 s后接触角降至11.92°;添加4种喷雾助剂能够有效提高玉米冠层的雾滴密度、雾滴覆盖率和雾滴沉积量,其中添加Agrospred 910助剂后雾滴密度、雾滴覆盖率及雾滴沉积量分别较对照增加了36.93%、35.92%和61.90%。表明在玉米田间使用植保无人机喷雾施药时,可以优选使用Agrospred 910喷雾助剂。     

不同连作年限棉田土壤理化性质及微生物区系变化规律研究

于2007年以不同连作年限棉田为研究对象,研究分析连作5 a、8 a、12 a年和15 a棉田土壤容重、土壤氮、磷、钾养分及微生物区系的变化规律,以揭示长期连作造成棉田减产的主要因素。研究结果表明：在棉农自主经营管理条件下,棉田土壤容重并未随着连作年限的增加呈现有规律的变化。随着连作年限的增加土壤速效磷、全氮、全钾含量均呈下降趋势,土壤有机质以及土壤速效钾含量则是连作8 a之后随着连作年限的增加呈下降趋势。随着连作年限的增加,棉田土壤微生物总量呈明显的下降趋势,连作8 a、12 a、15 a棉田的土壤微生物总数平均值分别比连作5 a的下降了40.1%、46.7%、52.4%,而且微生物菌群结构也发生了变化,总体表现为细菌和放线菌数量减少,真菌数量增加的发展态势。     

陕西省耕地资源禀赋与贫困关系量化研究

对陕西省108个县(区)的耕地资源指标和贫困指标进行了相关分析。运用Excel软件和Supermap软件处理耕地资源与人类社会经济关系的一系列指标。结论:1)陕西省耕地资源丰富县与贫困县相关性分析结果为无相关性;陕西省耕地资源禀赋与经济贫困之间的相关分析结果为无相关性;所以陕西省耕地资源禀赋与贫困之间没有相关性。2)陕西省贫困地区分布特点:全省贫困县主要分布在陕北和陕南;耕地资源丰富县主要分布在陕北和关中的山区;耕地资源丰富且贫困的地区主要分布在陕北和关中的山区;既非贫困县又非耕地资源丰富县主要分布在关中的平原地区。     

Study of the relation between carbofuran degradation and microbial or physicochemical characteristics of some french soils

In France, corn rootworm (Agriotes sp.) is controlled by applying insecticides such as carbofuran to the soil. In recent years, the failure of carbofuran to control this pest has been observed in the south-west area of France in continuous corn cropping. A soil survey was conducted in order to determine the main factors which could influence carbofuran degradation in various soils. Degradation estimates were based on measurement of the release of [ 14 C]carbon dioxide from [carbonyl- 14 C]carbofuran. The enhanced degradation of carbofuran observed in laboratory conditions corresponded to the growth of micro-organisms able to use carbofuran as sole carbon and nitrogen source. The size of this microbial population and the rates of carbofuran degradation were higher in the samples taken from plots with a history of carbofuran use than in samples from previously untreated plots. Abiological degradation was only observed in alkaline soil conditions. Statistical analyses showed that carbofuran-degrading activity was not related to any particular pedological characteristics.     

The bioaccumulation and biotransformation of cis,trans-cypermethrin in the rat

The disposition of the pyrethroid insecticide cypermethrin, (RS)-a-cyano-3-phenoxybenzyl (1RS)-cis, trans-3-(2,2-dichlorovinly)-2, 2-dimethylcyclopropane-carboxylate, has been studied in male and female rats following a single toxic oral dose (200mg kg⁻¹) of two radiolabelled forms ([¹⁴C-benzyl] and [¹⁴C-cyclopropyl]) of the insecticide. The bioaccumulation and elimination of ¹⁴C-benzyl-labelled cypermethrin, following repeated administration at a sub-toxic dose (2mg kg⁻¹), has also been studied in male and female rats. Although, at the toxic dose, radioactivity from the two radiolabelled forms was rapidly eliminated in urine and faeces, the increased excretion in the faeces, over that for low doses, was evidence that absorption was incomplete. The major pathways of metabolism involved cleavage of the ester bond, with subsequent hydroxylation and glucuronidation of the cyclopropyl acid moieties, together with hydroxylation and sulphation of the 3-phenoxybenzyl moiety. The absence of sex- or dose-dependent changes was reflected by the constant proportions of these metabolites found in the urine. Constant levels of radioactivity in tissues were achieved rapidly, generally within the first week of repeated administration. Elimination was rapid on the cessation of dosing, although less rapid from the fat and skin. The material in the fat was mainly the cis-isomers of cypermethrin, which were eliminated with a mean half-life of 18.2 days, compared with 3.4 days for the trans-isomers.     

保护性耕作对黄土高原春玉米田土壤理化特性的影响

为了探索黄土高原春玉米区保护性耕作农田土壤理化特性变化,测定分析了保护性耕作处理第二年春玉米生长不同时期农田土壤容重、水分和养分变化.结果表明,保护性耕作处理在玉米生长前期0～10 cm土壤容重呈下降趋势且小于传统耕作,但后期增加幅度较大;与传统耕作相比保护性耕作能显著增加玉米生长前期表层0～60 cm和后期100～200 cm土壤含水量 ,有较好保水、蓄水作用;保护性耕作下表层0～20 cm土壤养分指标除全磷外,均表现为稳定升高趋势,且能有效提高土壤全钾和速效钾含量;土壤有机质、全氮、速效氮、速效磷含量低于传统耕作,但变异系数较小.