Mean Nitrate Research Articles

Sulfate and nitrate chemistry in cumuliform clouds

Analyses of chemical measurements in and around cumuliform clouds in the western portion of Washington State indicate that for the 13 cases studied the mean sulfate production was 0.9 μg m −3 with an uncertainty of 0.5 μg m −3. Mean nitrate production in the clouds did not differ significantly from zero at the 90% confidence level. Nitrite concentrations in the cloud water (up to 0.19 ppm) appeared to be greater than can be explained by the absorption of NO x and HNO 2. The following mean values and standard deviations were obtained for scavenging coefficients between cloud base and a few hundred meters above cloud base: 0.6 ± 0.2 for sub-μm aerosol, 0.7 ± 0.4 for sulfate, 0.9 ± 0.2 for particulate nitrate, 0.9 ± 0.2 for gaseous nitrate, and 0.9 ± 0.1 for total nitrate. Comparisons of the measurements of sulfate production and the pH of the cloud water for four of the cumulus clouds with values obtained from an adiabatic, Lagrangian parcel model suggest that the measurements are explicable in terms of currently accepted aqueous SO 2 oxidation mechanisms.

The Glaciochemistry of Snow-Pits from Quelccaya Ice Cap, Peru, 1982

We present glaciochemical data from a pilot study of two snow-pits from Quelccaya ice cap, Peruvian Andes. These are the first samples to be analyzed from Quelccaya for nitrate and sulfate by ion chromatography (IC), for nitrate-plus-nitrite, reactive silicate and reactive iron by colorimetry, and for sodium by atomic absorption spectrophotometry. The 3 m pits used in this study represent a one year record of mass accumulation and the 29 samples collected provide the first glaciochemical data from this area which can be compared with glaciochemical studies from other locations.Reactive iron, reactive silicate and sodium, and the profiles of >0.63μm microparticles from Thompson and others (1984) are coincident, suggesting that transport and deposition into this area of each species are controlled by similar processes. The common source is probably local, resulting from crustal weathering. In general, the reactive silicate values are lower than those observed in other alpine glacier ice. The highest sulfate and nitrate values were observed in the upper few centimeters of the snow-pit. Most of the sulfate concentrations were less than 3 μM and are similar to values obtained for fresh surface snows from Bolivia (Stallard and Edmond 1981). Since biological gaseous emissions are thought to be the major source of sulfur and nitrogen to the atmosphere over the Amazon basin, the sulfate and nitrate fluctuations may be due to seasonal biological input and/or seasonal shifts in wind direction bringing material to Quelccaya.With only one exception, the colorimetric nitrate-plus-nitrite data were higher than the IC nitrate data. Unfortunately, the IC analyses were conducted 81 d after the colorimetric analyses. The difference between the two data sets could be attributable to the following: (1) the colorimetric technique may yield erroneously high results as suggested for polar ice by Herron (1982), (2) the IC technique yields erroneously low results due, in part, to the possible exclusion of nitrite concentrations, and/or (3) nitrite was lost via biological removal during the 81 d period before the IC analyses. If the IC data are correct, the mean nitrate value is 0.4μΜ (n = 29). This value is similar to those reported from pre-industrial aged polar ice (Herron 1982). If the colorimetric mean value (1.1 μM) is correct, it is similar to colorimetrically determined values from other high-elevation alpine ice (Lyons and Mayewski 1983).

The Glaciochemistry of Snow-Pits from Quelccaya Ice Cap, Peru, 1982

We present glaciochemical data from a pilot study of two snow-pits from Quelccaya ice cap, Peruvian Andes. These are the first samples to be analyzed from Quelccaya for nitrate and sulfate by ion chromatography (IC), for nitrate-plus-nitrite, reactive silicate and reactive iron by colorimetry, and for sodium by atomic absorption spectrophotometry. The 3 m pits used in this study represent a one year record of mass accumulation and the 29 samples collected provide the first glaciochemical data from this area which can be compared with glaciochemical studies from other locations. Reactive iron, reactive silicate and sodium, and the profiles of >0.63μm microparticles from Thompson and others (1984) are coincident, suggesting that transport and deposition into this area of each species are controlled by similar processes. The common source is probably local, resulting from crustal weathering. In general, the reactive silicate values are lower than those observed in other alpine glacier ice. The highest sulfate and nitrate values were observed in the upper few centimeters of the snow-pit. Most of the sulfate concentrations were less than 3 μM and are similar to values obtained for fresh surface snows from Bolivia (Stallard and Edmond 1981). Since biological gaseous emissions are thought to be the major source of sulfur and nitrogen to the atmosphere over the Amazon basin, the sulfate and nitrate fluctuations may be due to seasonal biological input and/or seasonal shifts in wind direction bringing material to Quelccaya. With only one exception, the colorimetric nitrate-plus-nitrite data were higher than the IC nitrate data. Unfortunately, the IC analyses were conducted 81 d after the colorimetric analyses. The difference between the two data sets could be attributable to the following: (1) the colorimetric technique may yield erroneously high results as suggested for polar ice by Herron (1982), (2) the IC technique yields erroneously low results due, in part, to the possible exclusion of nitrite concentrations, and/or (3) nitrite was lost via biological removal during the 81 d period before the IC analyses. If the IC data are correct, the mean nitrate value is 0.4μΜ (n = 29). This value is similar to those reported from pre-industrial aged polar ice (Herron 1982). If the colorimetric mean value (1.1 μM) is correct, it is similar to colorimetrically determined values from other high-elevation alpine ice (Lyons and Mayewski 1983).

Conversion of Arizona chaparral to grass increases water yield and nitrate loss

Converting an Arizona chaparral watershed to grass cover by using a soil application of karbutilate granules increased streamflow and the nitrate content of the water. Nitrate concentrations in streamflow from an untreated control watershed remained less than 1 ppm throughout the study, whereas nitrate from the treated watershed increased during the first posttreatment year to a maximum concentration of 56 ppm, with an annual weighted mean concentration of 16 ppm. Maximum concentrations of 60 and 69 ppm occurred during the third and fourth posttreatment years, when annual mean concentrations were 66‐ and 100‐fold above normal. After 11 years the annual mean concentration was still 14‐fold above normal. The mean nitrate concentration of the streamflow from the treated watershed for the entire 11‐year period was 29‐fold greater than that for the control watershed.

Phytoplankton succession in Lake Valencia, Venezuela

Phytoplankton counts and supporting physical and chemical data were taken on Lake Valencia, Venezuela, over a five-year interval. The data are used to test the validity of a successional paradigm for class-level taxa. According to the paradigm, formulated from previous studies of Lake Lanao, Philippines, and from data on temperate lakes, the order of taxa from early to late succession is: diatoms, chlorophytes, blue-green algae, dinoflagellates. A successional episode is considered to begin when stability of a water column is restored after deep mixing. As the episode progresses, there is a steady decrease in concentration of the limiting macronutrient (in this case, N). In a test of the validity of the paradigm for Lake Valencia, dates of exceptional population increase or decrease were obtained for each taxon. Since nitrate concentration declines steadily as succession progresses, the entry of a given taxon into the successional sequence is indicated quantitatively by the mean nitrate concentration on dates of exceptional increase in population density, and exit from the successional sequence is indicated by mean nitrate concentration on dates of exceptional population declines. The successional position of each major taxon, bounded by its entry and exit in the sequence, can be mapped on the complete spectrum of nitrate concentrations observed in the lake. For Lake Valencia, the nitrate mapping procedure agrees exactly with the predictions based on the successional paradigm. Conformance of Lake Valencia phytoplankton with predictions made a priori suggests that there is a generalized pattern in the phytoplankton succession of the mixed layers of temperate and tropical lakes.

Physical and chemical variability of the Baltic Sea: a joint experiment in the Gotland Basin

An area of 25 × 30 nmi with a subarea of 20 × 20 nmi in the Baltic Sea Gotland Basin was surveyed for about one month by vertical CTD and fluorometric chlorophyll a casts, and by towed profiles with a chemical profiler (nutrients, CTD, O 2, pH) and an undulating CTD. Autonomous current meter data were available for the same period. Five CTD surveys with a 5-mile spacing showed the existence of synoptic eddies and several other perturbations. A first mode eddy (with all the isopycnals lifted within the halocline) had reduced salinities in the upper layer and chlorophyll concentrations were reduced by 2 to 3-fold. A second mode eddy (with the isopycnals lifted in the top of the halocline and lowered in the bottom layers) with a diameter of 20 km was under prolonged observation. Anticyclonic currents at 96-m depth were up to 25 cm s −1. Along the section across the eddy at 80-m depth, the mean nitrate concentration dropped from about 7 to 8 to 5 μmol dm −3 while other chemical parameters lacked intense variations. An increased activity of the intrusive fine-structure was detected in the eddy center. The Baltic eddies are essentially non-linear, and transport water in their ‘nuclei’. An internal front, separating waters with different T,S composition, was discovered in the upper layers. The observations are discussed with respect to discovering long-term trends while monitoring the Baltic environment.

Seasonal variations in nitrate leaching in structured clay soils under mixed land use

Nitrate leaching was studied for 2 years in a structured clay soil (Evesham series) under grass, winter wheat and spring barley at N fertilizer inputs of 135–144 kg ha −1 year −1. Measurements of soil water to 2 m depth by neutron probe showed that the year could be divided into well defined periods of deficit, separated by a period when the soil was at its winter mean water content. Soil water potentials showed very little gradient for water flow below 1 m, and a persistent convergent zero flux plane at 40–60 cm depth during the autumn wetting-up period (September—November). Nitrate concentration in the drainage increased with discharge rates up to 3–6 mm day −1. Mean nitrate concentrations were generally highest during intermittent drain-flow in the autumn. Of the total N leached over the 2 years, 23 to 28% (5–7 kg N ha −1) was lost during this period. The remainder (13–25 kg N ha −1) was leached during winter and virtually no N was lost in the following spring-early summer. This seasonal pattern of N leaching was interpreted in terms of intermittent flow during rainfall of nitrate-rich water from surface layers, which bypassed the relatively dry soil matrix at 40–60 cm, but was intercepted by natural and artificial drainage channels. Implications for the prediction of N leaching loss based on the concept of excess winter rainfall are discussed. When predicting the start of N leaching in structured clay soils, the soil water status should be assessed from measurements of water potential rather than water content.

Fate of fertilizer nitrogen applied to grassland. I. Field leaching results

SummaryResults are presented from a 3 year investigation into nitrate leaching from isolated 0.4 ha grassland plots fertilized with 250, 500 and 900 kg N ha−1 a−1. Cumulative nitrate leaching over the 3 years was equivalent to 1.5%, 5.4% and 16.7% of the fertilizer applied at 250, 500 and 900 kg N ha−1 rates respectively. Over a whole drainage season, mean nitrate leachate concentrations at 250 kg N ha−1 did not exceed 4 mgl−1, although maximum values of 13.3 mgl−1 were observed. In contrast, at 900 kg N ha−1, the mean nitrate leachate concentration in two of the years exceeded 90 mgl−1. Mineral nitrogen balances constructed for the 1979 growing season indicated that leaching at 250 kg N ha−1 was low because net mineralization of soil organic nitrogen was small, and crop nitrogen uptake almost balanced fertilizer application. Although the pattern of nitrate leaching suggested that by‐passing occurred in the movement of water down the soil profile, it was not possible to confirm this using simulation models of leaching. Possible reasons for this, including the occurrence of rapid water flow down gravitationally drained macropores, are discussed.

Statistical analysis of nitrate concentrations from the River Frome (Dorset) for the period 1965–76

SUMMARY. Statistical analysis has been carried out on 11 years (1965–75) weekly data of nitrate concentrations and discharge values from the R. Frome (Dorset). The results have shown a trend over the 11‐year period with nitrate concentrations increasing by 0.11 mg NO3‐N 1−1 per year. A predictive model for nitrate concentrations for 1976 was made and even though discharge conditions were extreme, the mean predicted nitrate concentration of 3.37 ± 0.136 mgNO3‐N1−1 was very close to the observed mean nitrate concentration of 3.44mgN03‐N1−1.

NITRATE REDUCTASE ACTIVITY IN WHEAT (TRITICUM AESTIVUM L.) II. THE CORRELATION WITH YIELD

SummaryChanges in nitrate reductase activity in response to nitrogen treatment were measured in vivo in the basipetal part of the youngest ligule emergent leaf of wheat plants during early development. The relationship between these measurements and grain yield is reported for some spring wheats grown in a growth room and some field‐grown winter wheats. In both situations the c correlation of a linear regression of yield parameters and single measurements of nitrate reductase was found to be significant. Where split dressings of nitrogen were applied the seasonal mean nitrate reductase activity correlated well with yield.

Interference effects in sampling particulate nitrate in ambient air

A laboratory and field study was conducted to evaluate artifact nitrate formation on filter media. The filter media evaluated included a cellulose acetate, a Teflon, a cellulose and five types of glass fiber filters covering a pH range from 4.6 to 9.4. Field studies employed simultaneous sampling using five high volume samplers and a low volume sampler system providing both a respirable (i.e. < 3.5 μm) fraction and a sample without size segregation. Laboratory studies evaluated interaction of clean filters with nitrogen dioxide and nitric acid as possible sources of artifact nitrate. The influences of temperature, relative humidity, sampling time, NH 3, ozone and SO 2 were determined. In 24-h field sampling in San José and Los Alamitos, California, mean nitrate values obtained with the filters studied differed by as much as a factor of 2.4. Of the filters studied only the Teflon filter (Fluoropore) provided collection of nitrate with negligible error due to interaction of the filter with the gaseous pollutants studied. A pH9.3 high volume glass fiber filter collected, on average, about 10 μg m −3 artifact nitrate compared with 8.5 μg m −3 of true particulate nitrate in 24h sampling. Laboratory studies suggest that collection of gaseous nitric acid is the dominant source of artifact nitrate. Nitrogen dioxide only became a substantial source of artifact nitrate in the presence of relatively high concentrations of ozone.

Composition of aerosols over Los Angeles freeways

In October of 1976 aerosol particles were collected while driving on Los Angeles freeways and were analyzed for sulfate, nitrate, and elemental composition. The measurements indicate that neither nitrate nor sulfate concentrations increased significantly in the roadway. The mean nitrate concentration in the fine particle fraction was 0.2 μg m −3 and was not above the mean background value. The mean background sulfate concentration was 7.9 μg m −3, and the in-roadway sulfate increment was less than 1.5 μg m −3. However, the mean in-roadway lead concentration of 10.9 μg m −3 exceeded the mean background value by a factor of more than 6. The optical attenuation of the collected aerosol deposits was measured; the mean in-roadway value exceeded the background value by a factor of 4.

Groundwater quality along the eastern shores of Lake Taupo, 1975–76

Abstract To investigate the extent of spatial and temporal variation in groundwater quality along the eastern shores of Lake Taupo, New Zealand, data were collected from May 1975 to March 1976 from 14 boreholes sited to represent a variety of land use and human population density. Physical parameters investigated were water level, temperature, and electrical conductivity; the chemical constituents monitored were soluble reactive phosphorus, total dissolved phosphorus, nitrate and nitrite nitrogen (combined), ammonium nitrogen, total soluble iron, major cations and anions, and pH. The results show that groundwater quality can vary greatly over time and space. For example, spatial variation in mean soluble reactive phosphorus levels was 1–340 mg.m−3, in mean nitrate and nitrite nitrogen (combined) 3–13 930 mg.m−3, and in ammonium nitrogen from 5–633 mg.m−3. The most extreme variation with time concerned nitrate nitrogen at a site in Taupo township, where the concentration dropped from 16 430 mg.m−3 in early June 1975 to 1170 mg.m−3 in March 1976. Sometimes temporal variation was relatively small: at Motutere nitrate nitrogen stayed within the range 131–202 mg.m−3 during the study period. Generally, a few infrequently monitored boreholes should not be relied on to describe variations in groundwater quality.

Treatment of hypertension by paramedical personnel using a step-care approach: Diane C. Davies, Institutes of Medical Sciences, San Francisco, California; Richard D. Cohen

The objectives of this paper are to document and evaluate regional long-term trends and occurrences of nitrate in the ground water of agricultural watersheds. In Whatcom County, Washington, elevated nitrate concentrations in ground water are of great concern. Whatcom County is recognized by heavy agricultural activities, especially an intensive dairy farm industry. Historical nitrate concentration data from 1990 to 2000 were compiled from different agencies and assembled into a single composite database. A geographic information system was used to assess the spatial and temporal variability of nitrogen data. The analysis was conducted for the whole area as well as for individual watersheds and for different land use classes. In addition, nitrate concentration variability with descriptive parameters such as sampling depth, ground water recharge, dissolved oxygen, and on-ground nitrogen loadings was also investigated. The analysis showed that the areas with nitrate concentrations above the maximum contaminant level are areas characterized by heavy agricultural activities. The shallow surficial aquifers of the study area were found to contain high mean nitrate concentrations when compared to non-surficial aquifers. The analysis showed that high nitrate presence corresponds to areas with both high ground water recharge and high on-ground nitrogen loadings. In addition, the nitrate concentration decreased with increasing sampling depth. In general, the trend of long-term nitrate concentration remained elevated in shallow aquifers due to the persistent on-ground nitrogen loadings produced by agriculture-related land use practices. Finally, the watersheds were prioritized for management intervention, alternatives, and data monitoring based on a number of decision variables.

Metabolic Fate of the Precursors of N-Nitroso Compounds (III)

Urinary excretion rate of nitrate in man was studied by determining the amount of nitrate ingested with foods and beverages and that excreted into urine for 24hr and 48hr.The mean nitrate concentration ±S. D. in the urine (n=33) which were collected from 11 subjects at random was 74.4±42.5ppm. The excretion amounts of nitrate in the 24hr urine obtained from 9 subjects who ingested conventional diet containing from 44.1 to 864.2mg of nitrate was from 45.6 to 236.9mg, indicating a remarkable and individual differences of urinary excretion rate of nitrate (27.4 to 133.8%). The excretion amount of urinary nitrate every 2hr in two subjects was less than 10mg when only the low-nitrate diet containing a small amount of nitrate was ingested, but increased more than 25mg every 2hr by the ingestion of 200mg of sodium nitrate or 100g of salted Chinese cabbage, containing 75.1mg of nitrate, with the low-nitrate diet. The range of the urinary excretion rates of nitrate for 48hr was from 78.2 to 86.2% (n=3). No nitrite was detected in any urine specimens, and neither nitrate nor nitrite was detected in any feces (n=6).

Nitrate nitrogen levels in drinking water of urban areas with high- and low-risk populations for stomach cancer: an environmental epidemiology study

A correlation study between mean nitrate nitrogen levels (ppm) in drinking water samples (N = 1389) of Chilean urban areas and age-adjusted death rates per 100 000 population from stomach cancer, by province or region and sex, was made. Drinking water samples from all provinces (N = 25) had a weighed mean of 1.446 ppm (S.E.M. 0.068) with a range of 0.00--30.00 ppm. Nitrate nigrogen levels showed a positive but not significant association with male death rates. The correlation coefficient was +0.0335. Similarly, such levels did exhibit a positive but not significant correlation with female death rates (r = +0.0486). When NO3-N levels and male (r = +0.1367) or female (r = +0.1143) death rates were studied, by region, positive but insignificant correlations were detected. Using Cochran's approximation, mean nitrate nitrogen levels in drinking water samples from six provinces with 50% of the Chilean population (period 1953--55 versus 1973--75), showed a decrease from 1.835 to 1.291 ppm, but there was no significant difference (t = 1.32) between the two values, except in samples from Santiago Province (t = 2.11, P less than 0.05). Provinces (south central area) showing the highest gastric cancer mortality rates in the world for females (up to 40.8/100,000), and ranking second for males (up to 84.1/100,000), exhibited a very low mean level (0.825 ppm).

Metabolic Fate of the Precursors of N-Nitroso Compounds (I)

Urinary excretion rate of nitrate in man was studied by determining the amount of nitrate ingested with foods and beverages and that excreted into urine for 24hr and 48hr.The mean nitrate concentration ±S. D. in the urine (n=33) which were collected from 11 subjects at random was 74.4±42.5ppm. The excretion amounts of nitrate in the 24hr urine obtained from 9 subjects who ingested conventional diet containing from 44.1 to 864.2mg of nitrate was from 45.6 to 236.9mg, indicating a remarkable and individual differences of urinary excretion rate of nitrate (27.4 to 133.8%). The excretion amount of urinary nitrate every 2hr in two subjects was less than 10mg when only the low-nitrate diet containing a small amount of nitrate was ingested, but increased more than 25mg every 2hr by the ingestion of 200mg of sodium nitrate or 100g of salted Chinese cabbage, containing 75.1mg of nitrate, with the low-nitrate diet. The range of the urinary excretion rates of nitrate for 48hr was from 78.2 to 86.2% (n=3). No nitrite was detected in any urine specimens, and neither nitrate nor nitrite was detected in any feces (n=6).

Nitrate pollution of groundwater from nitrogen fertilizers and animal wastes in the Punjab, India

Fifty-seven water samples were obtained from wells situated on cultivated farms and near village settlements in the Ludhiana and Hoshiarpur districts of Punjab (India). Water samples collected in June and September, 1975 were analysed for nitrate. Probability plots indicated that 90% of the well-water samples may contain less than 45 mg NO 3 −/l, the upper safe limit. The nitrate content of well water near villages was significantly higher than in the cultivated area. Animal wastes appear to be the major contributor in the village environment. The nitrate concentration of well water decreased significantly with depth to water table, but correlated positively with amount of nitrogenous fertilizers added per unit area per year. Soil profile samples taken in June, 1975 from farms in the immediate vicinity of the sampled wells were analysed for nitrate and water content. The amount of NO 3 − contained in the soil profile down to 2.10 m depth correlated significantly with the nitrate concentration of well water in September, thus confirming that nitrates tend to reach the water table during the rainy season (July–September). The projected geometric mean nitrate concentration of ground water (computed on the expectation that the nitrate content of the saturated zone would equal that of the 1.50−2.10 m soil layer) was found to be 35.6 mg NO 3 −/l, many times higher than the observed mean of 1.88 mg NO 3 −1/l.

Seasonal and Canopy Variation in Nitrate Reductase Activity of Soybean (Glycine max L. Merr.) Varieties1

An in vivo assay was used to determine if differences existed in nitrate reductase activity among 16 soybean (Glycine max L. Merr.) varieties within four maturity groups. Canopy and seasonal profiles of nitrate reductase activity were determined. All varieties exhibited highest nitrate reductase activity per leaf ✕ nr in upper leaves of the plant canopy during growth stages up to mid pod fill. Activity levels were similar throughout the plant leal canopy following mid pod fill. Nitrate reductase activity per leaf × hr at a given node was generally highest the initial date at which the leaf was sampled and activity declined with leaf age. Mean nitrate reductase activity (µmoles NO‐2 formed per g fresh wt × hr) for the entire leaf canopy was highest in the seedling stage for all maturity groups and declined as the plants matured. Activity of the total plant (µmoles NO‐2 formed per plant × hr) was maximal at approximately the full bloom stage with all maturity groups, irrespective of the calendar date at which the maturity groups attained full bloom. Thus, enzyme activity appeared to be closely associated with physiological growth stage. Genetic variation (up to 1.8 fold) in enzyme activity (seasonal means of µmoles NO‐2 formed per plant × hr) was found within maturity groups II, III, and IV. However, enzyme activity did not correlate with either seed yield or seed protein content.

Some Effects of Nitrogen Fertilizer, Maturity, and Light on the Composition of Orchardgrass1

SynopsisNitrogen‐fertilized orchardgrass forage contained more crude protein, nitrate, and water than control forage. The effects were less marked with advancing maturity but continued through the seed stage. Fertilized forage contained less sugar previous to flowering. Composition changes were greater when fertilized plants were shaded. The highest mean nitrate level observed was 2.4%.