Field contamination

Another consideration when planning field fortification levels for the matrices is the lowest level for fortification. The low-level fortification samples should be set high enough above the limit of quantitation (LOQ) of the analyte so as to ensure that inadvertent field contamination does not add to and does not drive up the field recovery of the low-fortification samples. Setting the low field fortification level too low will lead to unacceptably high levels of the analyte in low field spike matrix samples if inadvertent aerial drift or pesticide transport occurs in and around where the field fortification samples are located. Such inadvertent aerial drift or transport is extremely hard to avoid since wind shifts and temperature inversions commonly occur during mixer-loader/re-entry exposure studies. 

Van Hoof, P.L., Kukkonen, J.V.K., Landrum, P.F. (2001) Impact of sediment manipulation on the bioaccumulation of polycyclic aromatic hydrocarbons from field-contaminated and laboratory-dosed sediments by an oligochaete. Environ. Toxicol. Chem. 20, 1752-1761. 

Little is known about field contamination by ochratoxin A. Coffee is one of the crops susceptible to ochratoxin, and contamination is often correlated to insect damage. Ochratoxin-producing Penicillium typically infest grain (especially wheat) in temperate zones. Further investigation is required to understand the factors that determine ochratoxin A contamination in coffee and in other susceptible crops. 

Pavlostathis, S.G. and Mathavan, G.N. Desorption kinetics of selected volatile organic compounds from field contaminated soils. Environ. Sci. TechnoL, 26(3) 532-538, 1992. 

Johnston AE, Goulding KWT, Poulton PR (1986) Soil acidification during more than 100 years under permanent grassland and woodland at Rothamsted. Soil Use Manage 2 3-10 Kahn SU (1982) Bound pesticides residues in soil and plant. Residue Rev 84 1-25 Kan AT, Chen W, Tomson MB (2000) Desorption kinetics from neutral hydrophobic organic compounds from field contaminated sediment. Environ Pollution 108 81-89 Kang SH, Xing BS (2005) Phenanthrene sorption to sequentially extracted soil humic acids and humans. Environ Sci Technol 39 134-140... 

In previous studies, the solubilization of hydrophobic organic contaminants using surfactants has been shown to increase the rate of contaminant desorption from soil to water (Deitsch and Smith 1995 Yeom et al. 1995 Tiehm et al. 1997). A 3,000 mg/L solution of Triton X-100 (CMC = 140 mg/L) increased the rate of desorption of laboratory-contaminated TCE from a peat soil (Deitsch and Smith 1995). However, the solubilization effect was secondary compared to the surfactant s effect on the desorption rate coefficient. Yeom et al (1995) developed a model that satisfactorily predicted the extent of polycyclic aromatic hydrocarbon solubilization from a coal tar-contaminated soil. Only at high surfactant dosages did the model fail to accurately predict the ability of different surfactants to solubilize polycyclic aromatic hydrocarbons. It was hypothesized that mass-transfer limitations encountered by the polycyclic aromatic hydrocarbons in the soil caused the observed differences between the data and the model simulations. In another study (Tiehm et al. 1997), two nonionic surfactants, Arkopal N-300 and Saogenat T-300, increased the rate of polycyclic aromatic hydrocarbon desorption from a field-contaminated soil. The primary mechanism for the enhanced desorption of polycyclic aromatic hydrocarbons was attributed to surfactant solubilization of the polycyclic aromatic hydrocarbons. 

Belfroid, A., van den Berg, M., Seinen, W., Hermens, J. van Gestel, K. (1995) Uptake, bioavailability and elimination of hydrophobic compounds in earthworms (Eisenia andrei) in field-contaminated soil. Environ. Toxicol. Chem. 14, 605-612. 

We observed that only a small fraction of the adsorbed mass would desorb even after a number of successive desorption steps. The investigation on laboratory contaminated soil showed a biphasic behavior, namely an easily desorbed fraction and a desorption resistant fraction. Both field contaminated and aged soils also showed the same behavior. The first stage involved a loosely bound fraction and the second stage involved a tightly bound fraction. The desorption constants calculated or estimated for the two fractions were em-... 

Also, vegetation monitoring is commonly proposed. Very few of the suggested approaches, however, are beyond the early research stage to the point where they could be deployed to provide reliable data concerning field contamination. 

Lethality due to ingestion of food contaminated by trichothecenes has been reported in horses (Rodricks and Eppley, 1974), cattle (Hsu et al, 1972), and humans (Joffe, 1974). General clinical signs include emesis, food refusal and weight loss, dermal effects, and immune suppression with secondary infection. Clinical signs are dependent on the specific trichothecene involved, the dose, species, route of exposure, as well as the nature of the exposure. Spontaneous and experimental exposures may give somewhat different results, as can exposure to field contaminated materials, when compared to purified toxin. In the case of field contamination or experimental use of crude extracts, multiple mycotoxins, both known and unknown, may be present at the same time. 

Endosulfan can accumulate in bodies of animals that live in contaminated water. It is highly toxic to many aquatic fishes. Male, 3-4-month-old Mallard ducks showed tremors, high carriage, wings crossed at the back and tail pointed down. In August 1995, more than 240000 fish in Alabama, United States, were killed due to a run-off from cotton fields contaminated with endosulfan. 

Ten Hulscher, Th. E. M., B.A. Vrind, H. van den Heuvel, L.E. van der Velde, P.C.M. van Noort, J.E.M. Beurskens, and H.A.J. Covers. 1999. Triphasic desorption of highly resistant chlorobenzenes, polychlorinated biphenyls, and polycyclic aromatic hydrocarbons in field contaminated sediment. Environ. Sci. Technol. 33 126-132. 

There should be documented prior usage of the pesticide in the field site, preferably for several previous years. If possible, the field should be separate hydrogeologically and physically from other fields where the pesticide under study has been previously used. This avoids the possibility of runoff from other fields contaminating the study fields and leaching from other fields contaminating the underlying aquifer. 

Gong P et al., Effects and bioavailability of 2,4,6-trinitrotoluene in spiked and field-contaminated soils to indigenous microorganisms, Environ, Toxicol. Chem., 18, 2681,1999. 

Most data on the relation of temperature to aflatoxin formation have been obtained with A. parasiticus. Aflatoxin contamination of cottonseed by A. flavus in the field occurs primarily in low-altitude areas of Arizona and the Imperial Valley of California and not in the hot and humid Southeastern States. Chronic field contamination of cottonseed apparently requires daily mean temperature of 34 C or above (T.E. Russell, personal communication). The significant difference between Arizona and the Southeast cotton areas is the high night temperatures of 32-34 C in Arizona. 

The results of Suer and Lifvergren (2003) indicate that mercury was removed from a field-contaminated soil by a combination of redox and complexation processes with iodide/iodine and electrokinetic mobilization. Iodide added to the cathode compartment was transported into the soil and oxidized to iodine near the... 

The use of either Avadex or Avadex at a rate of 1-1/2 lbs per acre, ccmpletely eradicates fields contaminated with wild oats and without being toxic to such crops as bcirley, wheat, oats, sugar beets and flctx. 

The wood is of Pliocene age and should be radiocarbon-dead. However, the finite age measured here for ffie humic and fulvic acid fractions probably reflects field contamination from microbial degradation and diagenetic breakdown products from the parent wood. 

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