Comparative persistence of pesticides on selected cultivars of specialty vegetables

The behavior and dissipation of several pesticides on selected cultivars of specialty vegetable crops were compared to determine appropriate preharvest intervals for compliance with maximum residue limits. To reduce application variability, a tank mix of pesticides was applied for each trial. Residues of eight pesticides applied to bok choi, Chinese broccoli, and fuzzy squash were similar for the two leafy vegetables; residues were higher than on squash because of the latter's larger mass-to-surface area ratio. Whereas residues of five of the nine pesticides applied to cabbage, Chinese cabbage, and bok choi did not differ significantly from 3 to 14 days after application, residues of cypermethrin and three fungicides were significantly higher on Chinese cabbage and bok choi. The residue deposits of the pesticides were about 50% lower on Chinese cabbage and 90% lower on cabbage than on bok choi. Dissipation of residues on different cultivars of lettuce and cabbage were compared after application of nine pesticides. With the exception of captan, residues on head lettuce were lower than on the other lettuces on day 1; cultivar differences were not significant for most of the nine applied pesticides on days 3 and 8. Generally, residues of the nine individual pesticides on storage cabbage, savoy cabbage, Chinese cabbage, and tah tsai did not differ significantly from day 1 to day 7 after application. Residue concentrations were generally significantly higher on bok choi than on the other cultivars. Residue deposits generally correlated with the rate of application; residues of captan, however, were about 50% of the predicted value. Significant differences in deposit and dissipation were observed among cultivars and pesticides, with dramatic initial decreases for diazinon and parathion. Because of their higher exposed surface area-to-mass ratios, leafier crops had higher residue concentrations than head varieties. Residues on lettuce cultivars were higher than on the cabbages. The results clearly indicate that structure significantly affects residue deposit and dissipation, and pesticide recommendations cannot always be extended to specialty crops without an investigation of the changes in preharvest intervals to prevent violations of the maximum residue limits.     

Determining organohalides in animal fats using gel permeation chromatographic cleanup: repeatability study

Evaluation of a previously published gel permeation chromatographic (GPC) procedure was undertaken to determine whether it can be used for additional organochlorine pesticides. After repeatability studies of many pesticides, the following compounds were approved for inclusion in the U.S. Department of Agriculture Domestic Residue Monitoring Program: coumaphos-S, stirophos, chlorpyrifos, ronnel, carbophenothion, chlorfenvinphos, phosalone, kepone, captan, linuron, and endosulfan I and II. Recoveries ranged from 54% for captan to 123% for ronnel. Ranges of CVs varied from 0-9.5% for carbophenothion to 7.1-47.7% for kepone. Although the minimum acceptable recovery of 50% was attained for all 12 pesticides, the anticipated CV of 20% was waived to include chlorpyrifos, endosulfan I and II, and kepone. For a multiresidue procedure involving approximately 40 compounds, these results were within the acceptable criteria.     

Determination of organophosphorus pesticides in fruit juices by matrix solid-phase dispersion and gas chromatography

A rapid multiresidue method was developed for the determination of nine organophosphorus pesticides in fruit juices. The analytical procedure is based on the matrix solid-phase dispersion (MSPD) of juice samples on Florisil in small glass columns and subsequent extraction with ethyl acetate assisted by sonication. Residue levels were determined by gas chromatography with nitrogen-phosphorus detection. Spiked blank samples were used as standards to counteract the matrix effect observed in the chromatographic determination. The NPD response for all pesticides was linear in the concentration range studied with determination coefficients >0.999. Average recoveries obtained for all of the pesticides in the different juices and fortification levels were >70% with relative standard deviations of <11%. The detection limits ranged from 0.1 to 0.6 microg/kg. The identity of the pesticides was confirmed by gas chromatography with mass spectrometric detection using selected ion monitoring. The proposed MSPD method was applied to determine pesticide residue levels in fruit juices sold in Spanish supermarkets. At least one pesticide was found in most of the samples, although the levels detected were very low, far from the maximum residue levels established for raw fruit.     

State programs for pesticide residues in foods

Two U.S. data collection and dissemination programs, FEEDCON and FOODCONTAM, are described. FEEDCON provides information on contamination levels in animal feeds of toxic chemical residues (pesticides, industrial chemicals, heavy metals, mycotoxins, natural plant toxins, salmonella, and therapeutic drug cross-contaminations). FEEDCON data are collected from approximately 40 state feed regulatory agencies, feed manufacturers, and related groups who subscribe ($100-$200 per year) to the program, which is sponsored by the Association of American Feed Control Officials. FOODCONTAM provides similar information, but is limited to pesticides, heavy metals and industrial chemicals (polychlorinated and polybrominated biphenyls, etc.) in human foods. Both programs have been developed and initiated under U.S. Food and Drug Administration contracts with the Mississippi State Chemical Laboratory. Program structures of both are outlined conceptually, and FOODCONTAM is described in detail. FOODCONTAM data-sharing program development is essentially complete, but expansion by incorporating FDA data with State Laboratory data is nearing reality.     

The role of shoot residues vs. crop species for soil arthropod diversity and abundance of arable systems

Removal of crop residues has become common practice in arable systems, however, little is known about how soil arthropod communities change in response to reduced resource availability and habitat complexity associated with residue removal. We added maize residues to wheat and maize fields and investigated soil arthropod diversity and abundance over the period of one year. Residue addition did not affect the diversity and little affected the abundance of soil arthropods in wheat and maize fields with the latter being restricted to few taxonomic groups, suggesting that at least in the short-term soil arthropods benefit little from crop residue-mediated increase in food supply and habitat structure. Contrasting the minor effects of residue addition, densities of soil arthropods were much higher in wheat than in maize fields, presumably due to more dense and more continuous coverage by plants, and higher input of root residues. Furthermore, in wheat fields density of arthropods more strongly varied with season, presumably due to more pronounced pulses of root exudates and root residues entering the soil in wheat as compared to maize fields in summer and winter, respectively. Low density and little variation in densities of soil arthropods in maize fields reflect that environmental conditions and resource supply varied little with crop coverage and season. Overall, the results point to low importance of aboveground crop residues for soil arthropod communities and highlight that belowground plant resources, i.e. root exudates and root residues are the major driver of soil arthropod communities of arable systems. Thus, at least in short term removal of crop residues for e.g., biofuel production is likely to be of minor importance for soil arthropod communities. In contrast, changing crop species from wheat to maize markedly reduces the density of soil animals threatening the ecosystem functions they provide.     

Reduction of azinphos-methyl, chlorpyrifos, esfenvalerate, and methomyl residues in processed apples

McIntosh, Red Delicious, and Golden Delicious from two years of experimental spray programs using azinphos-methyl, chlorpyrifos, esfenvalerate, and methomyl were processed into frozen apple slices, applesauce, single-strength juice, and juice concentrate. Residue levels were expressed as micrograms per 150 g of apple or the equivalent amount of apple product to calculate the percentage change in these pesticides brought about by processing. Producing single-strength apple juice reduced azinphos-methyl, chlorpyrifos, esfenvalerate, and methomyl residues by 97.6, 100, 97.8, and 78.1%, respectively. Production of applesauce reduced all four compounds by >/=95%. Azinphos-methyl, chlorpyrifos, esfenvalerate, and methomyl residues were reduced in apple slices by 94.1, 85.7, 98.6, and 94.7%, respectively. Processing is shown to be very effective in reducing the levels of these pesticides.     

农药残留的表面增强拉曼光谱快速检测技术研究现状与展望

果蔬农药残留危害人类健康,施药后,农药分布于其表皮和内部组织,果蔬表面农药绝对残留量低、不均匀,直接光谱检测表征难,而表面增强拉曼散射(surface-enhanced Raman scattering,SERS)技术具有分子级检测精度,可以有效扩增信号,在实现微量物质检测方面优势明显。为此,论文综述了国内外表面增强拉曼散射技术的研究现状,特别是详细介绍了通过设计合理的表面增强拉曼基底结构,实现农药残留信号增强的主要技术手段和表面增强拉曼光谱信号分析方法。在此基础上,指出农药残留的表面增强拉曼检测技术研究中的前沿热点问题,探讨并展望了表面增强拉曼技术在农药残留快速检测方面的发展趋势。基于表面增强拉曼的农药高灵敏度、快速检测表征技术,将在农药违禁使用和农药残留超标监管中有广阔应用前景。     

Monitoring Methyl Tertiary Butyl Ether (MTBE) and other Organic Micropollutants in Groundwater: Results from the Danish National Monitoring Program

The paper presents results of analyses of 7671 groundwater samples collected from 1115 screens in the period 1993 to 2001 for the Danish National Groundwater Monitoring Program. In Denmark groundwater is widely used for drinking water and the objectives of the monitoring program is to describe the present conditions, the development of, and the impacts on the groundwater. The design of the Danish National Groundwater Monitoring Program is described and data are provided. Data originate from monitoring areas and are supplemented with data from the waterworks' control of nearly 6000 water supply wells. In addition to pesticides there is a series of other organic compounds that must be considered in relation to possible groundwater contamination. Sources of these compounds and their importance in relation to groundwater contamination is discussed on the basis of the monitoring data. The organic micropollutants monitored are grouped according to chemical properties: aromatic hydrocarbons, chlorophenols, detergents, halogenated aliphatic hydrocarbons, ethers (MTBE), phenols, and phthalates. The most frequently found compounds were toluene (18.7% ), phenol (14.6%), xylene (10.9), trichloromethane (9.5%), and benzene (in 8.8% of the screens monitored). The five compounds most frequently found at a concentration above the maximum residue limits (MRL) for drinkingwater were: dibuthylphthalate (28%), phenol (14%), 2,4-dichlorophenol (10%), trichloromethane (10%), pentachlorophenol (7% of findings exceeding the MRL for drinkingwater). Overall, one or several compound was observed at least once in 57.8% of the 1115 screens monitored within the period 1993–2001. On a yearly basis the median finding frequency was 19%.     

Development of green onion and cabbage certified reference materials for quantification of organophosphorus and pyrethroid pesticides

Green onion and cabbage certified reference materials for the analysis of pesticide residues were issued by the National Metrology Institute of Japan, part of the National Institute of Advanced Industrial Science and Technology. Green onion and cabbage samples were grown so as to contain several kinds of organophosphorus and pyrethroid pesticides, and those were collected from a field in the Kochi Prefecture in Japan. The certification was carried out by using multiple analytical methods to ensure the reliability of analytical results; the values of target pesticides (diazinon, fenitrothion, cypermethrin, etofenprox, and permethrin for green onion and chlorpyrifos, fenitrothion, and permethrin for cabbage) were obtained by isotope dilution mass spectrometry. Certified values of target pesticides were 0.96-13.9 and 2.41-6.9 mg/kg for green onion and cabbage, respectively. These are the first green onion and cabbage powder certified reference materials in which organophosphorus and pyrethroid pesticides are determined.     

The FDA pesticides monitoring program

The U.S. Food and Drug Administration (FDA) carries out an extensive program to monitor foods for pesticide residues. The 2 main objectives of the program are to enforce tolerances established by the Environmental Protection Agency for pesticide residues on foods and feeds and to determine the incidence and level of pesticide residues in the food supply. Because of the wide diversity of pesticide/commodity combinations encountered, FDA uses a number of different approaches to achieve effective consumer protection. The components of the FDA Pesticides Monitoring Program and the strategy used in its development are described.     

Chlorpyrifos decline curves and residue levels from different commercial formulations applied to oranges

Residue levels and degradation rates of chlorpyrifos in orange fruits, orange leaves, and soil were investigated by using three different formulation types, that is, emulsifiable concentrate (EC), wettable granules (WG), and microencapsulates (ME). The pesticide degradation was studied for a period 131 days in orange fruits and for 161 days in orange leaves and soil. The experimental data were used to establish a mathematical model for the decline curves of chlorpyrifos residues as a function of time and to determine the relevant parameters describing such a process. Field trials showed a different degradation rate for EC and WG formulations as compared to ME formulation. For the first two formulations, the dissipation of chlorpyrifos in orange fruits was fast during the first phase and became much slower during the later period. Residue levels of chlorpyrifos from ME remained almost constant for approximately 65 days and then began to decrease. A similar behavior was observed for the three chlorpyrifos formulations on orange leaves and soil. Although microencapsulation of pesticides leads to improved handling safety, additional risks for the consumers, the agriculture workers, and the environment should be taken into account due to prolonged persistence of high residue levels in fruits as well as in leaves and soil.     

Reduction of pesticide residues on produce by rinsing

In 1997 this laboratory initiated a research program with the objective of examining the effect that rinsing of produce with tap water would have on pesticide residues. Samples were obtained from local markets and/or grown at our experimental farm. Because approximately 35% of produce from retail sources contains pesticide residues, growing and treating produce at an experimental farm had the advantage that all such samples contain pesticide residues. Pesticides were applied under normal field conditions to a variety of food crops and the vegetation was allowed to undergo natural weathering prior to harvest. The resulting samples contained field-incurred or "field-fortified" residues. This experimental design was employed to mimic as closely as possible real world samples. Crops were treated, harvested, and divided into equal subsamples. One subsample was processed unwashed, whereas the other was rinsed under tap water. The extraction and analysis method used was a multi-residue method developed in our laboratory. Twelve pesticides were included in this study: the fungicides captan, chlorothalonil, iprodione, and vinclozolin; and the insecticides endosulfan, permethrin, methoxychlor, malathion, diazinon, chlorpyrifos, bifenthrin, and DDE (a soil metabolite of DDT). Statistical analysis of the data using the Wilcoxon signed-rank test showed that rinsing removed residues for nine of the twelve pesticides studied. Residues of vinclozolin, bifenthrin, and chlorpyrifos were not reduced. The rinsability of a pesticide is not correlated with its water solubility.     

Fast turnaround multiresidue screen for pesticides in produce.

A rapid multiresidue screen for 110 pesticides was applied to 5628 produce samples. Samples were extracted, analyzed, and evaluated within 6 1/2 h of receipt. Analyses were confirmed within a 24 h period on those samples in which a potential residue was found above the U.S. Environmental Protection Agency's tolerance level. A thorough yet quick chromatographic interpretation program is also described.     

Behavior of 78 pesticides and pesticide metabolites on four different Ultra-Bond gas chromatographic columns

The gas chromatographic (GC) elution order and relative retention time data (compared to aldrin) are presented for 78 pesticides and pesticide metabolites on 4 different types of commercially available 2 mm id Ultra-Bond columns including Ultra-Bond 20M (20M), Ultra-Bond 20SE (20SE), Ultra-Bond 20M coated with 1% OV-210 (OV-210), and Ultra-Bond 20M coated with 0.5% OV-210 + 0.65% OV-17 (mixed phase). Relative retention time data (compared to parathion) are also represented for 19 organophosphorus insecticides on the 4 Ultra-Bond columns evaluated. Corresponding 4 mm id Ultra-Bond columns were evaluated at the same time as the 2 mm id columns, and results and comparisons for these larger-diameter columns are discussed. These data indicate that, with aldrin as a reference peak, a complement of the mixed-phase column and either the 20M, the 20SE, or the OV-210 column represents a useful chromatographic tool for dual-column analysis of pesticide residues. The 2 mm id columns were more useful in chromatographing later-eluting pesticides whereas the corresponding 4 mm id columns were more useful in chromatographing earlier-eluting pesticides.     

Pesticide residues in milk and fish samples collected from two Egyptian Governorates

Because of the intensive use of pesticides for the control of certain pests in Egypt, country-wide residue monitoring programs must be established that can cover all the Egyptian Governorates exposed to pesticide treatments. To do so, limited programs must be adopted first, so that current situations and future needs for improved programs are identified. The present paper reports results from a limited monitoring program, which started in 1985 in one governorate and then expanded to include another in 1986. Fish and milk samples were the commodities selected for residue analysis. The results showed that milk samples collected from Beni-Suef Governorate in 1986 had lower levels of organochlorine residues compared to those collected in 1985. Residues in boltifish and catfish samples in 1986 were much higher than those detected in 1985. In comparison with Beni-Suef Governorate, and contrary to expectations, milk derived from Fayoum Governorate in 1986 was more contaminated with pesticides. While the amount of residues in boltifish was comparatively higher, catfish samples were less contaminated.     

Tolerance setting process in the U.S. Environmental Protection Agency

The U.S. Environmental Protection Agency (EPA) is responsible for setting tolerances for pesticide residues in food, under the authority of the Federal Food, Drug, and Cosmetic Act. The residue chemistry data required to set tolerances include metabolism in plants and animals, analytical methods, magnitude of the residue, and concentration in processed foods. A key aspect of tolerance-setting procedures is the identity of the residue in the matrix of concern; without knowledge of the chemical moieties that occur as residues, it is impossible to develop suitable methods or generate meaningful residue data. For new chemicals, EPA carries out a single-laboratory validation of the analytical method needed to generate residue data and to enforce tolerances. Tolerance enforcement methods need to be rapid and inexpensive and to use commercially available equipment and reagents. Methods are more complex for many newer pesticides, which are polar compounds that leave low levels of residue. EPA now requires that the registrants of older pesticides, for which methods are not acceptable by today's standards, must develop better methods.     

农产品/食品中农药残留快速检测方法研究进展

农药残留的识别和量化通常依赖于气相色谱法、高效液相色谱法、气/液相色谱-质谱联用法以及毛细管电泳法,这些方法需涉及大而贵重的仪器、费时的样品处理以及专门的技术培训。因此,建立在线、高灵敏度、高选择性、简单高效、低成本的农药残留快速检测方法和技术非常重要。该文综述了用于农产品/食品的农药残留分析快速检测方法,主要包括酶抑制法、免疫分析法、光谱法(包括可见/近红外、红外、拉曼和激光诱导击穿光谱等)以及各种生物传感器等,分别介绍了这些方法最新的研究进展,同时分析并总结了这些快速检测方法和技术的基本原理和特点。目前的研究在灵敏度、重复性、准确性方面存在着一些不足,商品化的农药残留检测仪器也比较单一。由于纳米生物技术、分子印迹技术和微流控技术等技术有着巨大的应用潜力,因此特别介绍了这些技术在农药残留分析中的应用。农药残留快速分析技术未来将会朝着检测仪器的小型化和集成化、多通道检测、无线通讯方向发展,提高快速检测方法和仪器的稳定性和可靠性是必然趋势。     

Dissipation of teflubenzuron and triflumuron residues in field-sprayed and cold-stored pears.

Dissipation of residues of benzoylurea insecticides teflubenzuron (TFB) and triflumuron (TFM) under field conditions was evaluated on a pear orchard in Greece. Residues were determined by UV-HPLC analysis, with a detection limit of 0.030 mg/kg for both pesticides. TFB residues in pears were found to persist for 2 weeks and decline thereafter with 48% of the initial deposit remaining 42 days after the last application. TFM residues were found to decline following first-order kinetics and with a half-life of 39(+/-7) days. Residues of both pesticides found in pears collected at harvest maturity were lower than the maximum residue limits (MRLs) set by individual countries. Dissipation of TFB and TFM in cold-stored pears was also evaluated. TFB residues were very persistent for the whole storage period, whereas TFM residues did not dissipate for 6 weeks and then showed a constant decline; 7% of the initial concentration remained at the end of the storage period of 29 weeks.     

Organochlorinated compounds and selected metals in waters and soils from Doñana National Park (Spain)

A study on contamination levels by organochlorinated compounds (pesticides and PCBs) and heavy metals (Hg, Cd, Pb, Cu and Zn) in Doñana National Park (Spain) area and its surrounding region has been carried out. Residue levels of xenobiotics were determined in water and soils samples from seventeen sites selected through the park and nearest surrounding farm lands affecting to the inner Park. Also we analyzed some stations along the Guadiamar Basin in the north of Doñana region to determined the movement and influence of one mine situated over 40 km away, in Aznalcóllar, where the commercial expoitation of pyrites ores rich in Zn, Pb and Cu is being operated.     

我国土壤多参数快速检测方法和技术研发进展与展望

快速、准确获取土壤多种属性信息是土壤质量快速检测与评估以及现代精准农业发展的必然需求。本文系统阐述了我国在土壤水分、盐分、养分、pH、温度等多参数快速检测方法、技术与设备等方面的研发进展,比较了不同快速检测方法和技术的优缺点,分析了土壤多参数检测技术及设备的研发现状、专利申请情况以及国家重大科研仪器项目的资助情况。未来应加强土壤快速检测设备的核心软硬件系统开发与集成技术研究,实现土壤检测的多参数快速智能化,同时应进一步加大土壤快速检测方法和技术的科技投入与联合攻关研究,以满足我国土壤多参数快速检测及土壤质量快速调查与评估的实际需要。