Availability of linuron to plants in different soils

Total uptake of linuron by wheat seedlings in nutrient solutions was close to that expected from the product of the amounts of water transpired by the plants and the concentrations of herbicide in solution. Uptake from 19 different soils was less than the amount supplied by mass-flow when the concentrations of linuron in the soil solution were estimated from slurry adsorption measurements. Using a pressure-membrane technique, it was shown that the actual soil solution concentrations of linuron were less than those estimated, and following rewetting of pressure-membrane samples, the rate of redistribution of linuron between the adsorbed and solution phases was slow. The results suggest that under the conditions of the uptake experiments, the systems were not in equilibrium, and show that the rates of adsorption and desorption of linuron may be important in determining its availability to plants.     

小麦植株和麦田土壤莠去津残留气相色谱分析方法研究

本研究确立了乙腈振荡提取、弗罗里硅土SPE小柱净化小麦植株和麦田土壤中莠去津残留样本的前处理方法,建立了柱程序升温、GC-NPD残留样品检测方法.结果表明,优化色谱条件下,莠去津的色谱保留时间为5.97 min,在0.105～54.0 mg/L浓度范围内,莠去津浓度与其色谱峰面积在GC-NPD上线性响应良好,回归方程为Y=38.79X-120.34(R2=0.998 8).莠去津在小麦植株和麦田土壤中0.05～1mg/kg的3个水平的加标回收率均大于75％,各添加水平3次平行测定值的RSD均小于7％.其准确度和精密度均符合农药残留分析的要求.该色谱条件下仪器的最低检出量为0.38 ng,方法的最低检出浓度为0.018 mg/kg(植株)和0.021 mg/kg(麦田土壤),此检测灵敏度可以满足该农药在小麦植株和麦田土壤中残留的定量检测要求.     

Simulation of atrazine persistence in Spanish soils

The persistence of atrazine was monitored in three fields at different sites in Spain during two consecutive years (1990 and 1991). Laboratory assays for determining the influence of temperature and soil moisture content on the rate of herbicide degradation were carried out on soil samples from the same fields. The degradation constants derived from these assays, together with weather records for the period of the field experiments, were used in a computer program which simulated herbicide persistence in the field. Some adjustments were made to adapt the model to Spanish conditions. The model predicted with reasonable accuracy the persistence of the herbicide in two soils, although there was a tendency to overestimate the residues at early dates. Discrepancies between predicted and measured residues were greater in the third soil, due to rapid initial losses that were not predicted by the program. In this case, the agreement was improved if the program was run taking time zero to be one month after herbicide application. Possible reasons for these discrepancies are discussed.     

Chemical versus microbial degradation of cyanazine and atrazine in soils

A laboratory study was performed to investigate the relationship between chemical (non-biological) and microbial degradation of cyanazine and atrazine in soils ranging in pH from 5.3 to 8.1. Atrazine degradation was dominated by chemical processes in both a moderately acidic and a neutral pH soil, but showed a significant microbial involvement in the neutral pH soil. The primary cyanazine degradative mechanism was dependent on soil properties. Cyanazine was short-lived in neutral to slightly basic soils, due to rapid microbial degradation. Cyanazine amide and cyanazine acid were the major metabolites formed. In a moderately acidic soil, microbial degradation was slowed and chemical processes were the primary means of cyanazine degradation.     

Rapid dissipation of atrazine in soils taken from various maize fields

A laboratory study was carried out in order to measure the degradation rate of atrazine in 36 different soils taken from maize ( Zea mays L.) fields in Belgium. These soils differed in their alrazme treatment histories. pH. organic matter content and type of organic and mineral fertili-zation, Half-lives of less than 10 days were found in more than 60% of the soils sampled. This rapid dissipation could be linked in a significant way to repeated pretreaiments with atrazine (intensive maize cropping) as well as to higher pH values (from neutral to alkaline), A low organic matter content might also be a factor explaining the rapid degradation of atrazine. but to a lesser extent than the first two factors. On the other hand mineral fertilization was shown to slow down atrazine dissipation. It is hypothesized that repeated treatments of atrazine cause a mi-crobial adaptation to atrazine degradation and that acidic soil conditions impede this adaptation. To date, this is the first time that evidence for widespread accelerated degradation of atrazine has been reported.     

不同地理种群鸭跖草Commelina communis L.对莠去津的耐受性

鸭跖草是我国常见杂草,目前已成为农田难除杂草之一。生产实践中,莠去津对玉米田鸭跖草的防效已有所降低。2016-2017年,为了探讨鸭跖草不同地理种群对莠去津的耐受性,采用莠去津单剂量甄别方法,从黑龙江、吉林、辽宁、河北、江苏、浙江、湖北和贵州8个省份采集46个鸭跖草种群,进行了其对莠去津的耐受性初筛试验。在此基础上,选择7个不同地理来源的代表性种群,研究其对莠去津的敏感性差异,结果显示:种群JS-10、HB-3和HB-6对莠去津敏感,GR_(50)分别为122.21、153.27 g/hm~2和158.13 g/hm~2;种群JL-13、HLJ-2、JL-7和JL-1对莠去津耐受性相对较强,GR_(50)分别为273.98、277.29、374.68 g/hm~2和379.57 g/hm~2。以上结果表明,不同地理种群鸭跖草对莠去津的耐受水平存在差异,从地理分布上呈由南向北耐受水平增加的趋势。各地理种群对莠去津的耐受性差异可能与不同地区莠去津的使用年限、使用剂量和使用频度相关。     

Inhibition of photosynthesis in intact plants of biotypes resistant or susceptible to atrazine and cross-resistance to other herbicides

A concentration of atrazine of 0?1 mm 1^?1 in the nutrient solution resulted in complete inhibition of photosynthesis in intact leaves of susceptible biotypes of Amaranthus retroflexus L., Polygonum lapathifolium L., Chenopodium album L., Solanum nigrum L., Poa annua L. and Stellaria media (L.) Vill. within a few hours of treatment, whereas the inhibition of the resistant biotypes by the same concentration varied from small to moderate. In contrast, diuron (10 or 20 μm 1^?1) produced only minor differences between resistant and susceptible biotypes. The influence of some other herbicides on photosynthesis of these resistant biotypes was also smaller than that on the susceptible biotypes. This cross-resistance was evaluated with the resistance factor for intact leaves of Brassica napus L., A. retroflexus, and S. nigrum. This factor is equal to the ratio of the herbicide concentration in leaves of the resistant biotype to that in leaves of the susceptible biotype with inhibition to half-maximum rate of photosynthesis. This concentration in the leaves was calculated from the concentration in the nutrient solution, and the total transpiration divided by leaf area from the beginning of the herbicide treatment until the moment of half-maximum of photosynthesis. The resistance factors for intact leaves of A. retroflexus, S. nigrum and B. napus were 26–30 for atraton, 3–7 for metamitron, 2–9 for bromacil, 3–5 for monolinuron, 1 for diuron and < 1 for bentazone. For isolated chloroplasts much higher values have been reported. The reason for this discrepancy is not clear. A somewhat higher resistance factor (around 50–60) was derived after infiltration of detached leaves of these species with atraton solutions.     

Simulation of the persistence of atrazine in soil at different sites in Portugal

The effects of soil temperature and soil moisture content on the rates of degradation of atrazine, were measured in the laboratory in soils from different sites in Portugal. Persistence of atrazine was measured in the same soils in the field during the spring and summer of 1984, 1985, 1986 and 1987. Weather records from the different sites, measured during the periods of the field experi ments, were used in conjunction with appropriate constants derived from the laboratory data in a computer program to simulate persistence in the field. The model generally overestimated the ob served soil residues, particularly during the first 7–14 days after application. The fit from the model was good from day 14 to the end of the experiments.     

Resistance of Amaranthus hybridus to atrazine

Resistance of weeds to triazine herbicides has been recorded in many countries. The extent of the problem in South Africa is uncertain. In a pilot study, the atrazine resistance of Amaranthus hybridus L. (smooth pigweed) was investigated. Suspected resistant (R) and susceptible (S) biotypes were treated with commercially formulated atrazine. After post-and pre-emergence applications under tunnel conditions, it was found that the suspected R biotype plants were not affected at herbicide dosages of belween 1.25 and 25.0 kg a.i. ha^-1, i.e. up to 20 times gieater than the lowest recommended dosage. However, the S biotype plants were killed by the lowest dosage. In the fieid, mortalities in the R biolype were not observed after post-emergence applications of 1.25-10.00 kg a.i. ha^-1. In contrast, all S biotype plants were killed. In tunnel experiments, the R biotype was also found to be resistant to cyanazine and cyanazine+atrazine, while slight tolerance to linuron was observed. All these treatments resulted in 100% mortality of the S biotype. Although S biotype seeds oi A. hybridus were found to germinate slightly sooner under controlled conditions than R biotype seeds, preliminary results suggest that there are no major differences. Indications are that, although the growth of the S biotype may be greater than that of the R biotype, the competitive effect of the two biotypes on crop seedlings may well be similar.     

Availability to plants of herbicide residues in soil. Part II: Data for use in vegetable crop rotations

The response of a variety of vegetable crops to fifteen herbicides was estimated in culture solution over concentration ranges chosen to correspond with those that might occur in soil solution. Examples are given to show how these results can be used, in conjunction with the method for estimating the available herbicide residues (in Part I), to decide which crops may safely be sown in soil containing a herbicide residue.     

Availability and biodegradation of metribuzin in alluvial soils as affected by temperature and soil properties

Herbicide degradation in soils is highly temperature‐dependent. Laboratory incubations and field experiments are usually conducted with soils from the temperate climatic zone. Few data are available for cold conditions and the validation of approaches to correct the degradation rate at low temperatures representative of Nordic environments is scarce. Laboratory incubation studies were conducted at 5, 15 and 28°C to compare the influence of temperature on the dissipation of metribuzin in silt/sandy loam soils in southern and northern Norway and in a sandy loam soil under temperate climate in France. Using ¹⁴C‐labelled metribuzin, sorption and biodegradation were studied over an incubation period of 49 days. Metribuzin mineralisation and total soil organic carbon mineralisation rates showed a positive temperature response in all soils. Metribuzin mineralisation was low, but metabolites were formed and their abundance depended on temperature conditions. The rate of dissipation of ¹⁴C‐metribuzin from soil pore water was strongly dependent on temperature. In Nordic soils with low organic content, metribuzin sorption is rather weak and biodegradation is the most important process controlling its mobility and persistence.     

Phytotoxicity of four herbicides in different synthetic soils

The relative phytotoxicity of four soil-applied herbicides, benzthiazuron, cycloate, delachlor, and pyrazon, used for sugar beet (Beta vulgaris L.), was tested on a dilution series of peat, Newe Ya’ar clay soil and Hamadia calcareous clay soil mixed with sand, and of Newe Ya’ar clay soil mixed with lime. The phytotoxicity was assessed with oats (Avena sativa L. cv. Mulga). Cycloate was the most potent herbicide of the four, except in soils with high organic matter ( ?11%), where delachlor was more active. Benzthiazuron was the least phytotoxic herbicide in the peat + sand mixtures, but it was more active than pyrazon in lighter soils of the Newe Ya’ar series. The addition of sand to the peat and the soils increased the phytotoxicity of all herbicides. The addition of lime to Newe Ya’ar clay soil decreased the phytotoxicity of benzthiazuron and pyrazon but not of delachlor.     

Behaviour of ddt in three soils exposed to solar radiations under different conditions

Volatilization, mineralization, degradation and binding of soil-applied [¹⁴C]DDT were studied in three different soils from a tropical region of southern India subjected to solar irradiation and flooding for a period of 42 days. The soil types–red cotton soil, nursery soil and canal bank soil–differed in their organic carbon content, pH and texture. Under unflooded conditions, volatile losses were highest in the sandy canal bank soil. Flooding significantly enhanced volatilization, and this effect was maximal in the nursery soil, which had the highest organic carbon. The soils fully exposed to solar radiations in quartz tubes registered 1.5-1.8 times greater volatility. The volatilized organics contained appreciable quantities of DDE under both flooded and unflooded conditions. In addition, greater quantities of DDD volatilized from the flooded systems. The rate of formation of DDE was faster when soils were irradiated in quartz tubes. Mineralization remained minimal throughout the period of exposure and flooding the soil appeared to reduce further the [¹⁴C]carbon dioxide evolution. Canal bank soil exhibited the least mineralization and degradation. The data indicate that volatilization was significantly influenced by solar radiation and flooding to a much greater degree than by the differences in soil properties. Binding of DDT to soil was significantly increased by flooding the soil, thus leaving up to 33% of the initial DDT as bound residues in the nursery soil.     

两种沉水植物在不同水深和生长时期对入侵植物的响应

为研究沉水植物在不同水深和生长时期对不同种类入侵植物的响应,选取2种湿地入侵植物凤眼莲Eichhornia crassipes、水盾草Cabomba caroliniana和2种常见本地沉水植物黑藻Hydrillaverticillata、菹草Potamogeton crispus为研究对象,通过模拟试验探究在不同水深（0.2、0.4 m）和生长时期（生长初期和生长旺期）的本地沉水植物对2种入侵植物的响应。结果显示,当水深为0.4 m时更有利于黑藻的生长,并可削弱入侵植物对黑藻生长的消极作用,而水深对菹草的生长无显著影响;入侵植物种类对本地沉水植物的生长无显著影响,但影响方式却存在差异,其中水盾草倾向于直接抑制本地沉水植物的生长,而凤眼莲可以通过降低水体透明度以及总磷含量进而间接抑制本地沉水植物的生长。此外,外来植物在本地沉水植物生长初期入侵对本地沉水植物产生的消极影响较生长旺期入侵时更显著。表明凤眼莲及水盾草入侵对本地沉水植物生长的影响机制存在差异,本地沉水植物在适宜水深和生长旺期对2种入侵植物具有更强的抵抗能力。     

新疆奎屯垦区土壤砷含量及耐砷植物的筛选

土壤砷污染是一种严重的环境问题,植物对砷的耐性与积累性,已经成为污染生态学研究的热点。以新疆奎屯垦区为研究区域,通过对该地区土壤和植物中砷含量的测定,分析土壤中砷的污染状况,研究该区域内植物对砷的吸收特征,筛选适合当地气候的耐砷植物。结果表明:奎屯垦区土壤中砷的含量范围在7.25-39.63mg·kg-1,平均值为19.32mg·kg-1,高于全国的平均水平。对该区域内植物的采样分析发现藨草(ScirpusL)和芦苇(Phragmites)两种植物对砷具有较强的耐性。砷在两种植物中的含量分别为:藨草根部251.40mg·kg-1,地上部12.38mg·kg-1;芦苇根部92.91mg·kg-1,地上部4.03mg·kg-1,两种植物根部砷含量均高于土壤中砷含量(39.63mg·kg-1),表现出根部囤积型植物的特征。     

A bioassay technique to study the leaching behaviour of sulfonylurea herbicides in different soils

A bioassay procedure is described for quantitative determination of sulfonylurea herbicides in water and for studying their leaching behaviour in soils. Sunflower (Helianthus annuus L.) was found a more susceptible bioassay species than turnip (Brassica rapa L.) or lentil (Lens culinaris Medic.). The limit of quantitative detection (EC₃₀) in soil leachates was 0.12 μg 1^?1 for triasulfuron and 0.15 μg 1^?1 for metsulfuron-methyl. Leaching experiments were carried out by uniformly packing the soil in glass columns corresponding to its natural bulk density and applying simulated irrigation of 50 mm day^?1 with leachate water from untreated soil columns. Results obtained by measuring fresh weights of the true leaves of sunflowers in soil leachates showed that metsulfuron-methyl was much more mobile than triasulfuron in two soils with different sorption capacity. The BBA soil with low sorptive capacity showed very little retardation of both herbicides in the columns. The Horotiu soil with high sorptive capacity retarded triasulfuron for a long period, even under high flow conditions. Une technique d'essai biologique pour étudier l'aptitu.de au lessivage des herbicides sul-fony-lurées dans des différents sols Un protocole d'essai biologique est décrit pour la détermination quantitative des herbicides sulfonylurées dans l'eau, et pour l'étude de leur lessivage dans les sols. Le tournesol (Helianthus annuus) a été reconnu comme une espèce pour l'essai biologique plus sensible que le navet (Brassica rapa) ou la lentille (Lens culinaris). La limite de détection quantitative (EC₃₀) dans le lessivat du sol a été 0,12 μg 1^?1 pour le triasulfuron et 0,15 μg 1^?1 pour le metsulfuron methyl. Des études de lessivage ont été con-duites en mettant unifomément du sol dans des colonnes de verre de façon équivalente à la densité naturelle dans le sol et en appliquant une irrigation simulée de 50 mm jour^?1 avec de l'eau d'un lessivat de sol non traité. Les résult ats obtenus en mesurant le poids frais des feuilles vraies de tournesol dans les lessivats de sol ont montré que le metsulfuron-methyl était beau-coup plus mobile que le triasulfuron dans les 2 sols de capacités d'adsorption différentes. Le sol BBA avec une capacité d'adsorption faible a entraiîné un faible ralentissement des 2 herbicides dans les colonnes. Le sol Horotiu avec une capacité d'adsorption élevée a retardé le triasulfuron pendant une longue période, même sous des conditions de fortes précipitations. Biotestmethode zur Bestimmung des Ein-waschungsverhaltens von Sulfonyl-Harnstoff-herbiziden in unterschiedlich sorptiven Böden Eine Biotestmethode zum quantitativen Nach-weis von Sulfonyl-Harnstoffherbiziden in Was-serproben zur Bestimmung des Einwaschungs-verhaltens wurde entwickelt. Sonnenblume (Helianthus annuus L.) war unter den geprüf-ten Testpflanzen wesentlich empfindlicher als Herbstrübe (Brassica rapa L.) oder Linse (Lens culinaris Medic.). Als empfindlichste Meßgröße erwiesen sich die Echten Laubblätter der Sonnenblume. Die Nachweisgrenzen (EC₃₀-Werte) in Bodenperkolatwasser lagen bei 0,12 μg 1^?1 für Triasulfuron und 0,15 μg l^?1 für Metsulf-uron-methyl. Die Einwaschungsversuche wurden in Glassäulen durchgeführt, wobei die Böden gleichmäßig entsprechend ihrer Lagerungsdichte gepackt wurden. Die Beregnung erfolgte mit 50 mm Perkolat/Tag, das von nicht mit Herbiziden behandelten Säulenversuchen vorab gewonnen wurde. In beiden, unterschiedlich sorptiven, Böden zeigte Met-sulfuron-methyl eine stärkere Einwaschung als Triasulfuron. Im schwach sorptiven BBA-Boden wurden beide Wirkstoffe kaum retardiert, während Triasulfuron im stark sorptiven Horotiu-Boden über einen langen Zeitraum, auch unter den extremen Flußraten, zurückgehalten wurde.     

不同植被覆盖下植物残体分解特性

以黄土丘陵沟壑区子午岭次生林区为研究区域,研究了不同植被覆盖下植物残体的分解特性。结果表明:不同植被类型覆盖下,植物残体腐解速率为苜蓿>玉米>大油芒>辽东栎>沙棘,添加氮素比不加氮素的植物残体腐解速度快。根据腐解残留量的变化可将腐解过程分为4个阶段:快速分解阶段(0~1个月)、分解停滞阶段(2~7个月)、缓慢分解阶段(8~12个月)和趋于稳定阶段(13~15个月)。根据Olson指数衰减模型对植物残体腐解速率和腐解时间进行拟合,发现玉米、苜蓿、大油芒、辽东栎、沙棘分解95%所需的时间(T0.95)分别为43.73、23.35、52.56、108.1和161.1个月,且检验结果均达到显著相关水平。     

西花蓟马对不同寄主植物的选择及嗅觉行为反应

为比较西花蓟马Frankliniella occidentalis对不同寄主植物的选择性,本研究采用罩笼法观察了西花蓟马对8种不同蔬菜寄主植物(茄子、甘蓝、辣椒、黄瓜、莴笋、番茄、芹菜、香菜)的选择性,并使用"Y"形嗅觉仪评价了西花蓟马对不同蔬菜的嗅觉行为反应.结果 表明,在8种不同蔬菜寄主植物中,西花蓟马对茄子、甘蓝...     

双氟磺草胺在不同类型土壤中的吸附与淋溶特性研究

农药在土壤中的吸附和淋溶特性是评价其环境行为的重要指标。采用批量平衡法和土柱淋溶法,研究了双氟磺草胺在小麦种植区3种代表性土壤中的吸附和淋溶特性。结果表明:双氟磺草胺在安徽黏土、山东砂质壤土和河南砂质黏壤土中的吸附规律均可以较好地用Freundlich方程描述,其吸附系数(Kf)在0.39~0.62之间;土壤有机碳归一化吸附系数(Koc)在66.91~81.35之间,表明双氟磺草胺在3种土壤中均属于难吸附型;吸附自由能(ΔG)在-10.90~-10.42kJ/mol之间,均属于物理吸附。双氟磺草胺在3种土壤中的淋出率在71.7%~74.1%之间,说明其在3种土壤中的淋溶性均较强。双氟磺草胺初始添加量和腐殖酸对淋出率具有一定影响。综合试验结果,认为双氟磺草胺在3种土壤中的吸附和淋溶可能受土壤有机质含量、黏粒含量、阳离子交换量和土壤pH值等多个因素的综合影响,其对地下水的污染风险较大,因此应引起高度重视。     

HPLC determination of fenoxaprop and fenoxaprop-ethyl in different soils

This paper describes a method for the determination of fenoxaprop ethyl and fenoxaprop residues in four soil types using two extraction procedures: extraction with 0.1 M hydrochloric acid/methanol, partitioning with dichloromethane and extraction with ethyl acetate. The extracts were purified on florisil or alumina cartridge. The analyses were performed by reverse phase HPLC with UV detection at 280 nm. The best results in terms of recovery, clean-up efficiency and independence of soil characteristics were obtained with the combination ethyl acetate extraction alumina clean-up. Under these conditions, the recoveries were higher than 70 % and the detection limit was 0.02 mg kg^?1 soil.