John R. Garbarino

Contaminants in Arctic Snow Collected over Northwest Alaskan Sea Ice

Snow cores were collected over sea ice from four northwest Alaskan Arctic estuaries that represented the annual snowfallfrom the 1995–1996 season. Dissolved trace metals, major cationsand anions, total mercury, and organochlorine compounds weredetermined and compared to concentrations in previous arctic studies. Traces (<4 nanograms per liter, ng L-1) of cis- and trans-chlordane, dimethyl 2,3,5,6-tetrachloroterephthalate, dieldrin, endosulfan II, andPCBs were detected in some samples, with endosulfan I consistently present. High chlorpyrifos concentrations (70–80 ng L-1) also were estimated at three sites. The snow washighly enriched in sulfates (69–394 mg L-1), with highproportions of nonsea salt sulfates at three of five sites (9 of 15 samples), thus indicating possible contamination throughlong-distance transport and deposition of sulfate-rich atmospheric aerosols. Mercury, cadmium, chromium, molybdenum, and uranium were typically higher in the marine snow (n = 15) in relation to snow from arctic terrestrial studies, whereas cations associated with terrigenous sources, such as aluminum,frequently were lower over the sea ice. One Kasegaluk Lagoon site (Chukchi Sea) had especially high concentrations of totalmercury (mean = 214 ng L-1, standard deviation = 5 ng L-1), but no methyl mercury was detected above the method detection limit (0.036 ng L-1) at any of the sites. Elevated concentrations of sulfate, mercury, and certain heavymetals might indicate mechanisms of contaminant loss from the arctic atmosphere over marine water not previously reported overland areas. Scavenging by snow, fog, or riming processes and thehigh content of deposited halides might facilitate the loss of such contaminants from the atmosphere. Both the mercury and chlorpyrifos concentrations merit further investigation in view of their toxicity to aquatic organisms at low concentrations.

An Inductive-coupled Plasma Atomic-Emission Spectrometric Method for Routine Water Quality Testing

Induction-coupled plasma atomic-emission spectrometry offers an ideal method for simultaneous multielement analysis of natural water samples. The Water Resources Division of the U.S. Geological Survey currently employs this technique for quantitative analysis of 17 major and trace constituents. These include analysis of Ba, Be, Cd, Co, Cu, Fe, Pb, Li, Mn, Sr, Mo, V, Zn, Ca, Mg, Na, and SiO2 in a routine production mode, in which an excess of 1000 determinations can be made in a normal working day. Comparability studies with conventional single-element methods of analysis, such as atomic absorption spectrometry and colorimetric techniques, show essentially equivalent accuracy and precision, frequently at much higher sensitivity.

A Babington-type Nebulizer for Use in the Analysis of Natural Water Samples by Inductively Coupled Plasma Spectrometry

The construction and evaluation of a Babington-type pneumatic nebulizer for use in the inductively coupled plasma, emission spectrometric analysis of natural water samples is described. The performance of the nebulizer is relatively insensitive to suspended particulate matter, and detection limits for a wide variety of elements are equivalent to or better than those achieved with other pneumatic nebulizers. An accuracy comparison with a conventional crossflow pneumatic nebulizer shows essentially no analysis bias.

The effect of using different 0.45 μm filter membranes on ‘dissolved’ element concentrations in natural waters

Abstract The effect of 4 different 0.45 μm pore size filter membrane systems on the ‘dissolved’ concentration of 28 elements in 5 natural water samples of varying matrix is reported. In 3 of the 5 waters, consistently higher concentrations of most elements (minor and trace) are obtained using Nucleopore 47 mm filter and the cellulose acetate/nitrate 47 mm filter than those measured using the 142 mm cellulose nitrate MFS filter or the Gelman capsule 47 mm filter. These distinct and coherent patterns in elemental behaviour disappear for the other 2 samples, an organic-rich peat water of high suspended load and a mineralised sample high in Si and Ca. Thus the nature and degree of filtration artifacts is matrix-dependent. These trends are evident in both data sets produced by 2 independent laboratories using different instrumentation, techniques and calibrating procedures. The average relative standard deviation in elemental concentration across the 4 filter types is in the range 9–21%. The presence of such filtration artifacts must be considered in projects where, for example, seasonal variability of water composition is under examination, data from various sources are being merged or hydrogeochemical surveys are being conducted.

Flame Ionization Mass Spectrometry: Isotope Ratio Determinations for Potassium

The air/acetylene flame provides a convenient ion source for the determination of potassium isotopic ratios by mass spectrometry. Unlike the argon inductively coupled plasma (ICP), the flame provides low background in the mass region of interest. Ion production is quite satisfactory for isotope ratio measurements at the micrograms per milliliter (µg/mL) level and slightly below, with 1 µg/mL potassium giving about 105counts/second at a nominal mass-to-charge ratio of 39. The detection limit for potassium was 2–3 nanograms per milliliter (ng/mL). The ratio of 41K/39K was measured with 0.5–1% relative standard deviation, and a 41K spike representing 0.2% of the total potassium was readily detected. Both signal levels and signal stability were improved by adding a second easily ionized element such as cesium to samples and standards. Alternatively, a cesium solution could be aspirated for about 1 minute between sample measurements to ensure signal stability.

Totally automated inductively coupled plasma spectrometer for routine water quality testing

Abstract A completely automated ICP-AES system is implemented by using a dedicated minicomputer. The minicomputer system provides ICP-AES spectrochemical data acquisition, processing and storage, control for an automatic sampler, real-time quality control, and automatic standardization. Checks made on the elemental spectrochemical data insure that all the results fall within the analytical range of the method. The automatic sampler is a modified commercially available sampler that permits computer control and continuously variable rinse und sample equilibration periods. Real-time quality control is based on results obtained for a check standard. analyzed periodically between unknown samples. Automatic standardization is implemented by using a computer-actuated stepper motor that drives a multi-position rotary valve. Rotating the valve to the desired port permits the chosen standard solution to be pumped to the nebulizer of the spectrometer. Experiments have shown that the automated ICP-AES system produces results similar in accuracy to the manually operated system in addition to providing improvements in manpower efficiency and sample throughput.

Statistical Evaluation of an Inductively Coupled Plasma Atomic Emission Spectrometric Method for Routine Water Quality Testing

In an interlaboratory test, inductively coupled plasma atomic emission spectrometry (ICP-AES) was compared with flame atomic absorption spectrometry and molecular absorption spectrophotometry for the determination of 17 major and trace elements in 100 filtered natural water samples. No unacceptable biases were detected. The analysis precision of ICP-AES was found to be equal to or better than alternative methods. Known-addition recovery experiments demonstrated that the ICP-AES determinations are accurate to between ±2 and ±10 percent; four-fifths of the tests yielded average recoveries of 95–105 percent, with an average relative standard deviation of about 5 percent.

Automated standardization technique for an inductively-coupled plasma emission spectrometer

Abstract The manifold assembly subsystem described permits real-time computer-controlled standardization and quality control of a commercial inductively-coupled plasma atomic emission spectrometer. The manifold assembly consists of a branch-structured glass manifold, a series of microcomputer-controlled solenoid valves, and a reservoir for each standard. Automated standardization involves selective actuation of each solenoid valve that permits a specific mixed standard solution to be pumped to the nebulizer of the spectrometer. Quality control is based on the evaluation of results obtained for a mixed standard containing 17 analytes, that is measured periodically with unknown samples. An inaccurate standard evaluation triggers restandardization of the instrument according to a predetermined protocol. Interaction of the computer-controlled manifold assembly hardware with the spectrometer system is outlined. Evaluation of the automated standardization system with respect to reliability, simplicity, flexibility, and efficiency is compared to the manual procedure.