Soil sorption of acidic pesticides: modeling pH effects

A model of acidic pesticide sorption in soils was developed from theoretical modeling and experimental data, which initially considered a combination of a strongly acidic pesticide and a variable-charge soil with high clay content. Contribution of 2,4-D [(2,4-dichlorophenoxy) acetic acid] anionic-form sorption was small when compared with molecular sorption. Dissociation of 2,4-D was not sufficient to explain the variation in Kd as a function of pH. Accessibility of soil organic functional groups able to interact with the pesticide (conformational changes) as a function of organic matter dissociation was proposed to explain the observed differences in sorption. Experimental 2,4-D sorption data and K(oc) values from literature for flumetsulam [N-(2,6-difluorophenyl)-5-methyl [1,2,4] triazolo [1,5-a] pyrimidine-2-sulfonamide] and sulfentrazone [N-[2,4-dichloro-5-[4-(difluromethyl)-4,5-dihydro-3-methyl-5-oxo-1H-1,2,4-triazol-1-yl] phenyl] methanesulfonamide] in several soils fit the model.     

Radioactivity in environmental samples: Calibration standards measurement methods,quality assurance,and data analysis

The numerous environmental radioactivity measurements made by and for the U.S. Environmental Protection Agency (U.S. EPA) include measurements on samples of water, urine, food, milk, and air filters. Calibration standards are listed which are available in the form of water solutions and soils for a wide range of radionuclides. Method validation procedures for U.S. EPA approval include protocol development and single-laboratory and multiple-laboratory evaluation for precision and accuracy. Interlaboratory comparison studies are conducted for both cross-check and performance evaluation samples and involve 295 federal, state, and local laboratories. For water samples, 80%–90% of the participating laboratories are within the control limits for most of the radionuclides measured; however, some problem areas exist, especially for radium-228 and strontium-89 and -90. For milk and food samples, more than 90% of the laboratories are within control limits for cobalt-60 and cesium-137 but some problems exist for the measurement of strontium-90, iodine-131, and potassium-40. For tritium, 91% of the laboratories are within the control limit for water samples and 87% are within the control limits for the urine samples. The laboratory performance for air filter samples shows some problems for gross beta, strontium-90 and cesium-137 measurements.     

Prey chemical discrimination and strike-induced chemosensory searching in the lizardLiolaemus zapallarensis

Summary Experimental tests were conducted to determine whether the ambush foraging iguanian lizard,Liolaemus zapallarensis, was capable of discriminating prey chemicals from control substances and whether this lizard exhibits strike-induced chemosensory searching (SICS) or its components after biting prey. The two components of SICS are a poststrike elevation in tongue-flicking rate (PETF) and apparent searching movements for relocation of prey that has been bitten, but released or escaped.Liolaemus zapallarensis failed to discriminate prey chemicals from control substances, but exhibited significant PETF lasting one minute. SICS was absent inL. zapallarensis because no post-strike movements were observed. The absence of both prey chemical discrimination and SICS exhibited byL. zapallarensis is common to all the insectivorous iguanians and ambush foraging lizards studied to date. However,L. zapallarensis is the first insectivorous iguanian species shown to exhibit PETF. The results suggest thatL. zapallarensis does not use the tongue for detection, identification, or relocation of prey while foraging. The possibility does remain thatL. zapallarensis may be capable of chemically identifying prey once the prey stimuli reach the oral cavity.     

Descriptive ecology of offshore,deep-water,benthic algae in the temperate western North Atlantic Ocean

The vertical distribution, floristic composition and habitat ecology of sublittoral, benthic algae are described for two deep water, offshore stations in the Gulf of Maine, based on in situ observations and collections to 47 m depth during SCUBA and submarine dives. Twenty species of macroscopic algae were collected between 29 and 45 m. These occurred in two benthic algal associations: a Ptilota serrata association of fleshy, almost exclusively red algae from 29 to 37 m; and a deeper Lithothamnium glaciale association dominated by encrusting corallines and extended from ca 38 m to the lowest limit of macroscopic vegetation at 44 to 45 m. Below 45 m only endozoic and epizoic diatoms associated with sponges were observed. Owing to the seasonal stability, homogeneous composition and clear extinction depths of the two associations, we propose that the extinction depth of benthic seaweeds may provide a useful bioassay for making temporal comparison of water conditions at a single geographic region and, where substrata are similar, spatially among different geographic regions. Data obtained during the Jeffreys Ledge study are discussed in relation to this hypothesis.     

Materials policy — planning for consensus : Henniker V

The 1978 Henniker Conference on materials policy attracted a record number of participants from the USA and abroad. The week-long biennial gathering brought together 110 high-level materials administrators, policy makers, and researchers from government and private sectors. Henniker V, 30 July-4 August 1978, Henniker, New Hampshire.     

MISSISSIPPI EMBAYMENT AQUIFER SYSTEM IN MISSISSIPPI: GEOHYDROLOGIC DATA COMPILATION FOR FLOW MODEL SIMULATION1

ABSTRACT: As part of the Gulf Coast Regional Aquifer System Analysis (GC RASA) study, data from 184 geophysical well logs were used to define the geohydrologic framework of the Mississippi embayment aquifer system in Mississippi for flow model simulation. Five major aquifers of Eocene and Paleocene age were defined within this aquifer system in Mississippi. A computer data storage system was established to assimilate the information obtained from the geophysical logs. Computer programs were developed to manipulate the data to construct geologic sections and structure maps. Data from the storage system will be input to a five-layer, three-dimensional, finite-difference digital computer model that is used to simulate the flow dynamics in the five major aquifers of the Mississippi embayment aquifer system.