Pond studies

It is the objective of the Quality Assurance Section to inspect each Research Farm and each Development scientist annually however, the inspections are often more frequent at sites where complex nonroutine studies are being done such as pond studies, soil dissipation studies, or groundwater studies. 

Comparisons among laboratory and field observations are understandably less readily available for aquatic plants than for fish, but some field work has been done with duckweed. The data from pond studies by Rawn et al. (15) with permethrin allow some... 

Corbet et al. (1983) reported that a rooted plant species (Potemagetonpectimatus) and a surface-dwelling duckweed (Lemna sp.) accumulated concentrations of 1,3,6,8-TCDD of 280 and 105 ng/g (dry weight), respectively, following exposure to water containing 1,000 ng/L (ppt). The maximum concentrations were observed 8 days post-application and represented 6% of the total TCDD applied. These results are similar to those reported by Tsushimoto et al. (1982) in an outdoor pond study, in which a maximum bioaccumulation of 2,3,7,8-TCDD in the pond weeds Elodea nuttali and Ceratophyllon demersum equivalent to a BCF of 130 occurred after 5 days of exposure. In both studies, the tissue concentrations reached equilibrium in approximately 20 days and remained constant until the end of the experiment (approximately 58 and 170 days, respectively). These experimental data indicate that CDDs can accumulation in aquatic plant species through waterborne exposure. 

In a laboratory-scale waste treatment study, Davis et al. (1981) estimated that 25% of the nitrobenzene was degraded and 75% was lost through volatility in a system yielding a loss of about 80% of initial nitrobenzene in 6 days. In a stabilization pond study, the half-life by volatilization was about 20 hours, with approximately 3% adsorbed to sediments (Davis et al. 1983). 

The natural-pond study was conducted in a pond that had been studied for a number of years. The pond had a maximum depth of 2 m Chara and higher... 

R. H. Spmte and D. J. Kelsh, E/ectrokinetic Densif cation of So/ids in a Coa/Mine Sediment Pond—A Feasibi/ity Study, Bureau of Mines Report of Investigations 9137, 1988. 

Two of the study systems, Lake Michigan and Pond 3513, exhibit cyclic behavior in their concentrations of Pu(V) (Figure 2 and 3). The cycle in Lake Michigan seems to be closely coupled with the formation in the summer and dissolution in the winter of calcium carbonate and silica particles, which are related to primary production cycles in the lake(25). The experimental knowledge that both Pu(IV) and Pu(V) adsorb on calcium carbonate precipitates(20) confirms the importance of carbonate formation in the reduction of plutonium concentrations in late summer. Whether oxidation-reduction is important in this process has not been determined. 

Amphibians such as frogs and salamanders depend heavily on temporary ponds for breeding. These ponds are highly vulnerable to the "acid shock" events associated with storms or snowmelt. In several studies, reproduction of amphibians has been shown to be seriously restricted when acidity of their habitat decreases to a pH value of less than 5 14). 

Releases to the atmosphere from production facilities and disposal sites have also been reported. Studies have shown that releases of methyl parathion to the atmosphere occur in the vicinity of pesticide-producing factories. At two predominately downwind sites located 1 mile from a plant producing methyl parathion, average monthly concentrations were <0.57 and <0.64 ng/m (Foster 1974). Air emissions from methyl parathion production facilities have been reported to contain 1.0 kg/1,000 kg pesticide produced. In addition, evaporation from holding ponds for pesticide waste potentially contributes 7.4 mg/1,000 kg pesticide produced to the atmosphere (EPA 1978d). 

Mathematical models have also predicted a low volatility for methyl parathion (Jury et al. 1983 McLean et al. 1988). One study using a laboratory model designed to mimic conditions at soil pit and evaporation pond disposal sites (Sanders and Seiber 1983) did find a high volatility from the soil pit model (75% of the deposited material), but a low volatility for the evaporation pond model (3. 7% of the deposited material). A study of methyl parathion and the structurally similar compound ethyl parathion, which have similar vapor pressures, foimd that methyl parathion underwent less volatilization than ethyl parathion in a review of the data, the reduced level of volatilization for methyl parathion was determined to be due to its adsorption to the soil phase (Alvarez-Benedi et al. 1999). 

Estimates of bioconcentration factors, BCE, in aquatic organisms, based on calculations from water solubility and gave a log BCE of 1.80-2.89 (Kenaga 1980). Studies in outdoor ponds yielded log... 

BCF factors in fish ranging from 1.08 to 1.85, indicating that bioconcentration of methyl parathion is not an important fate process (Crossland and Bennett 1984). In another study, methyl parathion was added to the water of a carp-rearing pond and the concentration of methyl parathion was measured in water, soil, macrophytes, and carp over a 35-day period. Results showed that methyl parathion accumulated in macrophytes for 1 day and in carp for 3 days following exposure, and then dissipated. The concentrations of methyl parathion decreased in macrophytes by 94% by day 35 and by 98% in carp tissue by day 28 (Sabharwal and Belsare 1986). These data indicate the potential for biomagnification in the food chain is likely to be low because methyl parathion appears to be metabolized in aquatic organisms. 

Pyrethroids can also persist in sediments. In one study, alpha-cypermethrin was applied to a pond as an emulsifiable concentrate (Environmental Health Criteria 142). After 16 days of application, 5% of the applied dose was still present in sediment, falling to 3% after a further 17 days. This suggests a half-life of the order of 20-25 days—comparable in magnitude to half-lives measured in temperate soils. 

Because of the high toxicity of pyrethroids to aquatic invertebrates, these organisms are likely to be adversely affected by contamination of surface waters. Such contamination might be expected to have effects at the population level and above, at least in the short term. In one study of a farm pond, cypermethrin was applied aerially, adjacent to the water body (Kedwards et al. 1999a). Changes were observed in the composition of the macroinvertebrate community of the pond that were related to levels of the pyrethroid in the hydrosoil. Diptera were most affected, showing a decline in abundance with increasing cypermethrin concentration. Chironimid larvae first declined and later recovered. 

Okamoto K, Iwata Y (1982) Preparation of pond sediment. In Okamoto K, ed. Preparation, Analysis and Certification of Pond Sediment Certified Reference Material. Research Report No. 38, pp 13-22. National Institute for Environmental Studies, Ibaraki. 

A number of different open pond snow and ice storage techniques have been suggested. In Ottawa a storage for 90,000 m3 of snow in an abandoned rock quarry (120 x 80 x 9.5 m3, L x W x H), was studied. The mean cooling load was 7,000 kW. A light colored PE plastic tarpaulin was suggested as insulation, with melt water re-circulation for cold extraction. The estimated payback time was 10 years (Morofsky, 1981). 

Chemicals can pass through soil liners by molecular diffusion as well as by advective transport. One can study the molecular diffusion of chemicals in the soil by compacting soil at the bottom of an impermeable beaker and ponding waste liquid or leachate on top of the soil. At the start of the experiment, the concentration c is equal to c0 in the waste liquid. The soil is clean. Even though no water flows into the soil by advection, chemicals move into the soil by the process of molecular diffusion. Eventually, the concentration of the waste liquid and the soil will be one and the same (see Figure 26.12). 

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