Carl J. Popp

Aquatic insects as environmental monitors of trace metal contamination: Red River, New Mexico

Discontinuous sampling of water for toxic chemicals is unreliable in lotic ecosystems or in systems subjected to sporadic discharges. Such sampling either fails to detect the contaminants or seriously underestimates their concentrations. This study explored the use of resident aquatic insects as biomonitors of trace metal contamination in a river subjected to episodic spills of Mo mill tailings. Aquatic insects at sites downstream from the mill accumulated more Mo and Cu than upstream insects. Due to a prolonged shutdown at the mine, no tailings spills were recorded during this study and Mo and Cu levels in water and bottom sediments declined to near background levels. However, concentrations of these metals in insects declined only slightly. This study indicates that aquatic insects are useful biomonitors of trace metal contamination in an intermittently impacted system. Reduction of elevated trace metal concentrations from the insects occurred at a slower rate than from the non-living components of the river ecosystem thereby facilitating detection of the spills.

The dissociation of oxy-acids at elevated temperatures

Abstract The heat capacities of dissociation for carbonic, bicarbonate, phosphoric, biphosphate, silicic, nitric, boric and bisulfate oxy-acids have been evaluated at temperatures up to 300°C using published dissociation constants, heat capacities and a model which explicitly accounts for both electrostatic and nonelectrostatic contributions to the thermodynamic properties of dissociation. The heat capacities calculated are independent of the entropies of dissociation or the chemical characteristics of the acids, and are the same for all acids of a given dissociation type ( i.e. , 1st, 2nd, etc.). The average deviation between measured and calculated log K T s is less than 0.05 log units in the temperature range from 25 to 300°C. Dissociation constants for acetic acid can be accurately calculated using the oxy-acid heat capacity expression. The heat capacities are used to calculate dissociation constants for the oxy-acids of Cr(VI), N(III), S(IV), S(II), Se(IV), Se(VI), As(III), As(V), Te(VI), Cl(I), Cl(III), I(V) and C 1 –C 3 aliphatic acids to temperatures of 300°C.

Use of radiometric (Cs-137, Pb-210), geomorphic, and stratigraphic techniques to date recent oxbow sediments in the Rio Puerco drainage Grants uranium region, New Mexico

In the absence of historic geochemical baseline data for the Grants uranium region, environmental changes resulting from uranium mine-mill activities can be determined only by indirect methods. A methodology for determining the age of recent sediments in streams draining the region has been established based on combined geomorphic, stratigraphic, and radiometric dating techniques. Because clayrich sediments retain possible radionuclides and heavy metals derived from mineralization and mined sources, sample sites which contain fine-grained deposits that both predate and postdate mine-mill activity were located in abandoned-channel segments (oxbows) of major streams draining the eastern Grants uranium region. Aerial photographs (and derivative maps) taken between 1935 and 1971 provided the historical and geomorphic documentation of approximate dates of oxbow formation and ages of alluvial fills in the abandoned-channel segments. Pits were dug at these oxbow sites to determine stratigraphy and composition of the deposits. Samples collected from pit walls and auger holes below the pits were subjected to radiometric analysis by gamma ray spectrometry for the artificial radionuclide Cs-137 and the natural radionuclide Pb-210 as well as other U-238 and Th-232 daughters. Because of the dynamic nature of the system, absolute dating with Cs-137 was not possible but samples could be dated as either pre-or post-1950. The 1950 date is important because it marked the beginning of the uranium exploitation in the region. The Pb-210 dating was not possible because background Pb-210 was very high relative to fallout Pb-210.

Measurements of 7Be and 210Pb in rain, snow, and hail

Abstract Measurements of the levels of 7Be and 210Pb are reported for rain, snow, and hail samples taken at Argonne, Illinois, and Socorro, New Mexico. These natural radioisotopes are indicators of the sources of the aerosols contributing materials to the precipitation samples. The data presented indicate that the more soluble 7Be is enriched in the precipitation samples with respect to 210Pb, as compared to the ratios of these radioisotopes found in aerosol samples. Use of the 210Po/210Pb activity ratios as an internal clock indicated that the aerosols contributing to the precipitation ranged in age from 10 to 47 days. Levels of 7Be ranged from 11 to 55 pCi L−1 for the samples, with the highest levels in a stratus precipitation event and in a thunderstorm with the lowest wet deposition rate. These results are discussed with regard to the potential for use of these radioisotopes in the determination of stratospheric-tropospheric mixing and in their geochemical usage as indicators of sedimentation rates.

Acidic Precipitation in Western North America: Trends, Sources, and Altitude Effects in New Mexico 1979–1985

Volume-weighted pH values in central New Mexico have averaged 3.8 to 5.1 during the period 1979–1985. Samples collected at a high altitude site (3200m) have lower pH values than found for low altitude samples (1400m). Both dry deposition and event-averaged pH values have been higher than the volume-weighted averages due to neutralization by terrestrial material. During the period 1980–1984, changes in pH values and wet sulfate loading have correlated to S02 emissions from regional non-ferrous smelters. Sulfur isotope analyses of sulfate extracted from regional rain samples yielded a δ34SCD(%) of + 3.91 ± 1.1, indicating very little regional differentiation which, in turn, suggests that the regional atmospheric sulfate scavenged by precipitation is well-mixed and relatively homogeneous.

Transition metal complexes of diazine N-oxides

Abstract Metal complexes of pyrazine 1,4 dioxide, pyridazine N-oxide and 4,6-dimethylpyrimidine N-oxide with 3d transition metal perchlorates were synthesized. Transition metal chloride complexes of 4,6-dimethylpyrimidine N-oxide were also synthesized. The new complexes were characterized by elemental analysis, IR spectra, molar electrolytic conductance measurements, magnetic susceptibility measurements and electronic spectra. Stoichiometries indicated 6-coordinated complexes except for the copper and chloride complexes which were 4-coordinated. Conductivity measurements demonstrated that the perchlorate anions were uncoordinated and the chloride complexes contained coordinated chloride. The complexes were found to be coordinated through the oxygen in all cases. Electronic spectra were used to calculate 10 Dq values for the complexes. The ligand field strengths found were equivalent to those determined for substituted pyridine N-oxide complexes. The pKa values of the N-oxides have been determined by comparing ΔνNO of the liquids and ΔνOH of phenol-ligand complexes to σPyNO values for pyridine N-oxides.

Remote measurement of NO2 in the brown cloud over Albuquerque, New Mexico

Remote measurements of nitrogen dioxide (NO2) were recorded in the ‘brown cloud’ over Albuquerque, NM, using absorption spectroscopy in the winter of 1987-88 and summer of 1989. The NO2 burdens (optical densities) measured in this manner were found to be in excess of 100 ppm-m. These long pathlength measurements correspond to total concentrations of approximately 5–10 ppb over the integrated observation pathlengths, which ranged from 10–20 km. These concentrations compare well with single location, independent NOx analyses. Using two correlation (absorption) spectrometers simultaneously, it was shown that the NO2 distribution is not uniform over the city and can change on the order of minutes in the boundary layer late in the day, demonstrating the advantages of NO2 optical measurements for assessing the location and extent of urban nitrogen dioxide levels in the boundary layer.