Aquatic Organisms Field Studies

Although diflubenzuron is not sprayed directly on freshwaters in gypsy moth control, aerial spraying of large forest tracts may result in exposure of streams by way of leaf litter. Residual diflubenzuron was present for 

No data are available on effects of diflubenzuron on mammalian wildlife. However, results of studies on small laboratory animals and domestic livestock are available, and these indicate several trends. Adverse effect levels occurred in dogs fed diets containing 160.0 mg/kg (6.2 mg/kg BW daily) for 13 weeks (abnormal blood chemistry), in mice given 125.0 mg/kg BW daily for 30 days (hepatocellular changes), in rabbits fed diets containing 640.0 mg/kg for 3 weeks (abnormal hemoglobin), and in rats given 5000.0 mg/kg BW daily for 13 weeks 

Intestinal absorption of diflubenzuron in laboratory rats, measured as the sum of urinary and biliary excretion, decreases with increasing dose from 50% at a single oral dose of 4.0 mg/kg BW to 4% at 900.0 mg/kg BW. Excretion is almost complete after 75 h at that time up to 4% of the administered dose is recovered from skiimed carcasses. About 80% of diflubenzuron metabolites excreted by rats seem to have the basic diflubenzuron structure intact. Three metabolites are largely excreted as conjugates in the bile. One metabolite, 

6- difluorobenzoic acid, is excreted largely in urine. Its counterpart, 4-chlorophenylurea, was not present in urine or bile in appreciable quantity, nor was 4-chloroaniline detected. Lifetime feeding studies of 4-chloroaniline, a relatively common diflubenzuron metabolite, showed no compound-related effects in laboratory mice and rats. 

6- difluorobenzoic acid, and 4-chloroaniline compose only 15% of the total residue in liver the bulk of the residue is not extractable. Dietary levels of 5.0 mg/kg ration produce 

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Diflubenzuron effects on selected aquatic organisms field studies... 

Table 17.5 Diflubenzuron Effects on Selected Aquatic Organisms Field Studies Ecosystem, Dose, and...

Bio accumulation studies in aquatic nontarget organisms (field)... 

Research into the aquatic chemistry of plutonium has produced information showing how this radioelement is mobilized and transported in the environment. Field studies revealed that the sorption of plutonium onto sediments is an equilibrium process which influences the concentration in natural waters. This equilibrium process is modified by the oxidation state of the soluble plutonium and by the presence of dissolved organic carbon (DOC). Higher concentrations of fallout plutonium in natural waters are associated with higher DOC. Laboratory experiments confirm the correlation. In waters low in DOC oxidized plutonium, Pu(V), is the dominant oxidation state while reduced plutonium, Pu(III+IV), is more prevalent where high concentrations of DOC exist. Laboratory and field experiments have provided some information on the possible chemical processes which lead to changes in the oxidation state of plutonium and to its complexation by natural ligands. 

The previous section described active samplers where the air is swept of particles using mechanical mechanisms. This section describes passive samplers that do not move, but collect material that deposits by impaction or sedimentation deposition. These types of collector are the most common type for field studies aimed at assessing exposure of aquatic and terrestrial organisms to pesticides. 

The inherent chemical complexity of DOM presents many challenges to understanding the role of DOM in C and N cycling and other processes in aquatic ecosystems. The measurement of trace organic moieties in major fractions of DOM, such as fulvic acids, can provide valuable data for understanding sources and biogeochemical pathways. In field studies, multiple lines of evidence can be critical for definitive interpretation of results. The tracer approaches outlined in this chapter should be used in conjunction with mass balance and flux measurements, for example. 

Field and laboratory studies were conducted to determine the levels of Cd, Pb, and HCBD in various samples collected from a swamp environment in Louisiana and to assess the toxicities of As, Cd, and Hg to two species of aquatic organisms (bluegills and crawfish) indigenous to this swamp [18]. Cadmium and Pb were present in almost all collected samples. Their concentrations in fish were below the action levels set by EPA for the protection of human health. However, hazardous levels of these two elements were found in samples of crawfish, vegetation, soil, sediment, and water to some extent. Low levels of HCBD were recorded in water and sediment samples. In bioassay studies, Hg was found to be the most toxic metal, while As was the least toxic. Between the two test organisms, blue-gills appeared to be more sensitive than crawfish. Mixtures of Cd with As or Hg resulted in a combined toxic effect which was simply additive. However, a synergistic effect was recorded with the mixtures of As and Hg. 

Many multispecies tests and field studies are designed to look at only certain populations or other attributes of the ecosystem. This is not the fault of the study per se, since the funding, personnel, and physical resources are usually limited. The danger lies in the picking and choosing of secondary results from these studies. For example, the standardized aquatic microcosm contains 16 species that are initially inoculated into the system. However, in the results for publication, the dynamics and interactions of all species and the combinations are not reported. To do so would be cumbersome and expensive. Only the dynamics of the organisms and interactions which are apparently the critical components are reported. Assuming that the other components are not affected because of their omission or lack of space in the article could be erroneous. Anecdotal data from field or multispecies tests are similarly difficult to interpret. Omission or inclusion of a report may reflect more the nature of the researcher than the presence or absence of the effect. 

Not all fish species seem equally well suited to study DNA adduct formation. Van der Oost (1997) summarized that about 50% of the species studied under field conditions can be considered as responders by showing significant increases of DNA adduct levels in liver in a polluted environment. In general, in order to obtain meaningful results, the choice of appropriate reference sites is of crucial importance in studies on aquatic organisms. Furthermore, fish from different... 

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