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Lagrangian sampling was conducted on the Mississippi River in late July through early August 1999 to test the hypothesis that nitrate (NO3) is transported conservatively in the Mississippi River. Three different approaches were pursued to test the hypothesis: (1) a mass balance for NO3 was evaluated for evidence of net gains and losses, (2) stable isotopes of NO3 were measured (δ15N and δ 18O) to determine if fractionation occurred, and (3) the concentrations of dissolved gases (N2O, N2 and Ar) in river water were measured and compared to theoretical equilibrium concentrations. Integrated water samples and flow measurements were obtained at 10 sites on the Mississippi River and 7 sites near the mouths of major tributaries from northern Iowa to southern Louisiana, a distance of about 2,250 river kilometers. Mass balance calculations indicate that more than 80 percent of the NO3 mass discharged from the Mississippi River (1,930 metric tons/day) during the study period originated in the first 500 river kilometers of the study reach. The mass balance calculations also indicate that NO3 was not lost from the water column upstream of Vicksburg, MS, but that there might have been some loss of NO3 in the lower 700 kilometers of the study reach. The stable isotope ratios of N and O (δ15N and δ18O) of NO3 were consistent with mixing and transport in the absence of fractionating gains or losses. The concentrations of nitrogen (N2) and argon (Ar) dissolved in river water decreased in the downstream direction, approximately in equilibrium with air at increasing temperatures, giving no evidence of gains or losses of N2 by nitrogen fixation or denitrification. Nitrous oxide (N2O) concentrations in the Mississippi River were approximately 26 to 200 percent of air saturation, indicating relatively low net production by combination of nitrification and denitrification. Results from this study indicate that most (>90%) of the NO3 that entered the Mississippi River during July-August 1999 was transported to the Gulf of Mexico. [ABSTRACT FROM AUTHOR]

Agricultural chemical transport to surface water and the linkage to other hydrological compartments, principally ground water, was investigated at five watersheds in semiarid to humid climatic settings. Chemical transport was affected by storm water runoff, soil drainage, irrigation, and how streams were linked to shallow ground water systems. Irrigation practices and timing of chemical use greatly affected nutrient and pesticide transport in the semiarid basins. Irrigation with imported water tended to increase ground water and chemical transport, whereas the use of locally pumped irrigation water may eliminate connections between streams and ground water, resulting in lower annual loads. Drainage pathways in humid environments are important because the loads may be transported in tile drains, or through varying combinations of ground water discharge, and overland flow. In most cases, overland flow contributed the greatest loads, but a significant portion of the annual load of nitrate and some pesticide degradates can be transported under base-flow conditions. The highest basin yields for nitrate were measured in a semiarid irrigated system that used imported water and in a stream dominated by tile drainage in a humid environment. Pesticide loads, as a percent of actual use (LAPU), showed the effects of climate and geohydrologic conditions. The LAPU values in the semiarid study basin in Washington were generally low because most of the load was transported in ground water discharge to the stream. When herbicides are applied during the rainy season in a semiarid setting, such as simazine in the California basin, LAPU values are similar to those in the Midwest basins.

Enzyme-linked immunosorbent assay (ELISA) data from surface water reconnaissance were compared to data from samples analyzed by gas chromatography for the pesticide residues cyanazine (2-[[4-chloro-6-(ethylamino)-1,3,5-triazin-2-yl]amino]-2-methylpropanenitrile) and metolachlor (2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl)acetamide). When ELISA analyses were duplicated, cyanazine and metolachlor detection was found to have highly reproducible results; adjusted R2s were 0.97 and 0.94, respectively. When ELISA results for cyanazine were regressed against gas chromatography results, the models effectively predicted cyanazine concentrations from ELISA analyses (adjusted R2s ranging from 0.76 to 0.81). The intercepts and slopes for these models were not different from 0 and 1, respectively. This indicates that cyanazine analysis by ELISA is expected to give the same results as analysis by gas chromatography. However, regressing ELISA analyses for metolachlor against gas chromatography data provided more variable results (adjusted R2s ranged from 0.67 to 0.94). Regression models for metolachlor analyses had two of three intercepts that were not different from 0. Slopes for all metolachlor regression models were significantly different from 1. This indicates that as metolachlor concentrations increase, ELISA will over- or under-estimate metolachlor concentration, depending on the method of comparison. ELISA can be effectively used to detect cyanazine and metolachlor in surface water samples. However, when detections of metolachlor have significant consequences or implications it may be necessary to use other analytical methods.

In April 1995, the US Geological Survey began a study to determine the occurrence and temporal distribution of 49 pesticides and pesticide metabolites in air and rain samples from an urban and an agricultural sampling site in Mississippi. The study was a joint effort between the National Water-Quality Assessment and the Toxic Substances Programs and was part of a larger study examining the occurrence and temporal distribution of pesticides in air and rain in the Mississippi River basin. Concurrent high-volume air and wet-only deposition samples were collected weekly. The air samplers consisted of a glass-fiber filter to collect particles and tandem polyurethane foam plugs to collect gas-phase pesticides. Every rain and air sample collected from the urban and agricultural sites had detectable levels of multiple pesticides. The magnitude of the total concentration was 5-10 times higher at the agricultural site as compared to the urban site. The pesticide with the highest concentration in rain at both sites was methyl parathion. The pesticide with the highest concentration in the air samples from the agricultural site was also methyl parathion, but from the urban site the highest concentration was diazinon followed closely by chlorpyrifos. More than two decades since p,p'-DDT was banned from use in the United States, p,p'-DDE, a metabolite of p,p'-DDT, was detected in every air sample collected from the agricultural site and in more than half of the air samples from the urban site.

Weekly composite air samples were collected from early April through to mid-September 1995 at three paired urban and agricultural sites along the Mississippi River region of the Midwestern United States. The paired sampling sites were located in Mississippi, Iowa, and Minnesota. A background site, removed from dense urban and agricultural areas, was located on the shore of Lake Superior in Michigan. Each sample was analyzed for 49 compounds; of these, 21 of 26 herbicides, 13 of 19 insecticides, and 4 of 4 related transformation products were detected during the study, with most pesticides detected in more than one sample. The maximum number of pesticides detected in an air sample was 18. Herbicides were the predominant type of pesticide detected at every site. Detection frequencies of most herbicides were similar at the urban and agricultural sites in Iowa and Minnesota. In Mississippi, herbicides generally were detected more frequently at the agricultural site. The insecticides chlorpyrifos, diazinon, and carbaryl, which are used in agricultural and non-agricultural settings, were detected more frequently in urban sites than agricultural sites in Mississippi and Iowa. Methyl parathion was detected in 70% of the samples from the Mississippi agricultural site and at the highest concentration (62 ng/m3 air) of any insecticide measured in the study. At the background site, dacthal (100%), atrazine (35%), cyanazine (22%), and the (primarily atrazine) triazine transformation products CIAT (35%) and CEAT (17%) were detected most frequently, suggesting their potential for long-range atmospheric transport.

Background: We review the literature and report a case of refractory erythema elevatum diutinum associated with IgA paraproteinemia that was successfully controlled with intermittent plasma exchange (PLEX)., Observations: Typical lesions of erythema elevatum diutinum developed in a 72-year-old patient with IgA paraproteinemia; the condition predictably flared whenever IgA levels reached a threshold of 8 g/L. After 8 years of unsuccessful treatment with various agents, we instituted a trial of PLEX during an acute flare. Following 6 exchanges over a period of 2 weeks, the IgA level decreased from 8 to 2 g/L and the skin lesions cleared. Three weeks later, new skin lesions developed and the IgA level had rebounded from 2 to just over 8 g/L. A second course of PLEX was administered, with excellent results, and a 3-month course of oral chlorambucil (2 mg/d) was initiated. The patient's condition remained in clinical remission for 10 months. Over the ensuing 9 years, she suffered 11 further flares, each of which was associated with IgA levels of 8 to 10 g/L and each responding dramatically to 3 to 5 PLEXs followed by a consolidative dose of intravenous cyclophosphamide (250-500 mg)., Conclusion: We believe that PLEX may have an important role in the management of severe erythema elevatum diutinum associated with monoclonal paraproteinemia refractory to other therapy.

Common causes of hair loss include androgenic hair loss, alopecia areata, trichotillomania, tinea capitis, telogen effluvium, and traction alopecia. The author discusses their distinguishing clinical features and those of less common alopecias.

A case of Sézary's syndrome occurred in a 45-year-old man. The unusual noteworthy features in this case are dermal sclerosis, peripheral neuropathy, and bone marrow fibrosis. In two other cases, reviewed here, there was a tendency to fibrosis; therefore, we propose that this process may be an integral part of Sézary's syndrome.