Environmental letters最新文献

In line with the then emerging air pollution control regulations Union Electric installed a limestone injection wet scrubber sulfur dioxide removal system on an intermediate size coal-fired utility boiler at its Meramec Power Plant on an experimental basis in September, 1968. Approximately 3 years of operation many difficulties were encountered with plugging and scaling of various system components by calcium sulphate. As a result of this experience along with related experiences by other utilities employing similar systems, the experiment was terminated in June, 1971. As a result of the experiences gained, however, second generation experiments in sulfur dioxide removal have been initiated elsewhere with the hope of improved performance. A number of experimental projects are still under tests. Costs in resources, reliability, and disposal of residual by-products are matters of great concern. The ture cost of sulfur dioxide removal systems in dollars and resources is not well known and perhaps a reevaluation of current and future SO2 removal projects is in order at this time before additional resources are committed.

Gossyplure used to bait field traps at a dose of 50 micrograms admixed with 4-16 milligrams of an antioxidant attracted and captured male pink bollworm moths early in the cotton-growing season (early May) in Israel, whereas 20 milligrams of hexalure plus antioxidant was completely inactive under identical conditions. Although gossyplure without antioxidant was inactivated through decomposition within ten days, the mixtures remained attractive for at least two months; the antioxidant also increased moth catches 2.5 fold. Monitoring data obtained with 3000 gossyplure-baited traps, at one trap per 50 dunams, in cotton fields in the Beth-Shann region proved that capture thresholds of 5 moths/trap/night to the end of July and 8 moths/trap/night afterward were completely satisfactory for maintaining a low 2.8% average boll infestation for which only 5.8 insecticidal treatments were required during the entire growing season; results were even better in other areas of the country.

Pentachloro[U-14C]phenol was administered orally to Charles River CD strain pregnant rats on day 15 of gestation. Concentrations found in the placentas and fetuses up to 32 hr remained very small indicating that the amount that passes through the placental barrier is negligible. Unlabeled compound was administered on days 8, 9, 10, 11, 12, and 13 of gestation. The incidence of resorptions in the treated animals was not significantly greater than that in the controls. Although malformations were observed, the number was minimal and could have been due to the toxic effects of the compound on the maternal rat.

The reduction of arsenate ion to arsenite ion by a variety of tissues was widely distributed, and not a property of any particular tissue. The nature of the reduction was investigated by using various chemical inducers and inhibitors and is believed to be chemical in nature.

A comparison of the field attractiveness of five samples of American-synthesized and one sample of Japanese-synthesized (Z,E)-9,11-tetradecadien-1-01 acetate (9,11-TDDA), the sex pheromone of Spodoptera littoralis Boisd. and S. litura (F.), showed that traps baited with one of the American-produced samples and the Japanese product were equally effective in attracting and capturing S. littoralis males in cotton and alfalfa fields of Israel. Optimum captures were obtained for periods up to three months with 4800 mug of 9,11-TDDA plus 8 mg of an antioxidant; higher doses were not advantageous. Paper squares were superior to two types of rubber septa and to closed polyethylene vials as dispensers for the pheromone; the polyethylene vials were least effective. In terms of numbers of moths captured, open polyethylene vials were as effective as paper dispensers when both were baited with 9-11-TDDA plus antioxidant. Admixture of (Z,E)-9,12-tetradecadien-1-o1 acetate (9,12-TDDA) with 9,11-TDDA was antagonistic at ratios of 1:20 and 1:50, but ratios from 1:500 to 1:1600 were synergistic, increasing moth catches up to 2.5-fold. Pheromone traps placed in Caesarea sand dunes located at least 3 km from the nearest host area captured larger numbers of males than traps placed in cultivated areas. It is therefore recommended that safety belts of pheromone traps, about 500 m apart, be used around cultivated areas to prevent invasion of the pest from outside and to attract males present inside such areas, thus reducing both the male population and mating through mass trapping and disruption of sex communication.

A method for the determination of neophytadiene in the total particulate matter of cigarette smoke was developed and applied to test its relationship to isoprene deliveries. Neophytadiene is suggested as a preferred measure of the contribution of terpenoids to experimental tobacco smoke carcinogenicity. Typical deliveries of neophytadiene are presented.

The transfer of 35SO4= from water to air by bursting bubbles was studied as a function of three levels each of three variables in a bubbling solution. The variables were pH, surfactant concentration, and Na2 35SO4 concentration. One combination of the above variables was also studied at three different temperatures. Sterile water solutions containing different combinations of the above factors and a fixed amount of 22NaCl were bubbled in an enclosure for 1 hour. After bubbling, samples of the aerosol produced, the larger drops that fell out of the air, and the bulk solution were collected and assayed for their 35S and 22Na content using liquid scintillation counting. The 35S/22Na enrichment for each droplet sample as compared to the ratio for the bulk solution was determined, and it was found to be dependent upon the combination of the factor levels being bubbled. Both positive and negative enrichments were found, with large positive enrichments being found consistently only for the highest value of surfactant concentration. The temperature study showed no significant enrichment differences for any of the three temperatures studied.

Design traffic volumes, vehicle emission factors and meterological data are used to assess the impact of a suburban limited-access highway segment. Mesoscale effects are determined by emission inventory techniques. Microscale effects are determined using a pollutant dispersion model developed by the California Division of Highways. The air pollution impact of the highway segment is small, and should not be considered a significant criteria for decisions concerning construction of the highway.

A series of chemical extraction procedures are used to obtain data on the partitioning of trace metals among the various geochemical phases of sediments. These components include intersititial water, solubility of solid minerals, ions on exchange sites, metal carbonates, easily reducible phases, organics and sulfides, iron oxides, and lithogenous (mineral residual) fractions. In general, a mass balance of less than 10% deviation can be obtained. Experimental results show very small fractions of trace metals to be in the form of interstital water or soluble ions. Trace metals in the exchangeable phase are almost negligible, and those in the mineral residual phases range from 2.5% Cd for one sediment to 98% Cu for another. The non-residual trace metals content is found to increase with decreasing sand content.