Seasonal Variations In Nitrate Concentrations Research Articles

Assessment of nitrate contamination in a transnational groundwater basin: a case study in the Ceylanpinar Plain, Turkey

A study was undertaken to determine seasonal variations in nitrate concentrations in a transnational groundwater resource beneath the Ceylanpinar Plain near the border between Turkey and Syria. Spatial distribution maps of nitrate pollution for groundwater in the study area were created using a geographical information system (GIS), and the potential for contamination in the entire plain was determined. Seasonal variations of nitrate concentrations in groundwater were assessed by sampling during spring, summer, autumn, and winter in the period April 2012 to January 2013. The groundwater samples were analyzed for nitrate (NO3). The results obtained were evaluated using a number of national and international standards and classifications. Seasonal average concentration distribution maps were established for nitrate to determine the extent and severity of contamination by this parameter in groundwater in the region. The monitoring indicated that nitrate concentrations in only two wells exceeded the recommended drinking water limit and that groundwater beneath the basin is currently suitable for irrigation.

A critical re-evaluation of controls on spatial and seasonal variations in nitrate concentrations in river waters throughout the River Derwent catchment in North Yorkshire, UK.

Since mean nitrate concentration along single river channels increases significantly with percent arable land use upstream of sampling points and autumn/early winter flushes in nitrate concentration are widespread, it is generally concluded that farmers contribute most of the nitrate. For the River Derwent in North Yorkshire, the correlation between nitrate concentration and percent arable land use is much poorer when tributary data are included in the equation, because of greater variations in dilution by water draining upland areas and in other N input sources. For the whole river system therefore, percent upland moorland/rough grazing land cover is an appreciably better predictor than percent arable land use for nitrate concentration. Upland land use encompasses the higher precipitation and runoff in such areas, and the subsequent greater dilution downstream of both arable land runoff and effluent from treatment works, as well as an inverse correlation to percent arable land use. This is strongly supported by the observation that, for the Derwent, Meteorological Office rainfall data alone proved even better than percent moorland rough grazing for predicting nitrate concentration. The dilution effect is therefore substantial but highly seasonal; lower runoff and dilution in summer offset the lower leaching losses from arable land, and higher dilution and runoff in winter offset greater nitrate leaching losses from arable soils. Because of this, coupled to improved efficiency of nitrogen fertilizer use, seasonality trends in nitrate concentrations that were pronounced a decade ago now have all but disappeared in the catchment.

Nitrogen dynamics in large shallow eutrophic Lake Chaohu, China

Temporal and spatial dynamics of nitrogen in lake and interstitial water were studied monthly in a large shallow, eutrophic lake in subtropical China from October 2002 to September 2003. The distribution of nitrogen was consistent with the idea that high nitrogen concentrations in the western part of the lake resulted from high levels of the nutrients from the surrounding cities through sewage-drainage systems. Nitrate was the predominant form of nitrogen in the overlying water, while ammonium was predominant in the interstitial water, indicating that strong oxidative nutrient regeneration occurred near the sediment-water interface. Nitrate could be an important dissolved inorganic matter source for phytoplankton, which in turn influenced the seasonal variations of nitrate concentrations in lake water. Significant positive correlation between ammonium fluxes and water temperature was observed and could probably be attributed to the intensified ammonification and nitrate reduction with increased temperature. Positive correlation between ammonium fluxes and algae biomass and Chl a concentrations may indicate that phytoplankton was an important factor driving ammonium fluxes in our study lake, and vice versa that higher fluxes of ammonium supported a higher biomass of the phytoplankton.

Seasonal and interannual variations of nitrate and chloride in stream waters related to spatial and temporal patterns of groundwater concentrations in agricultural catchments

AbstractNitrate concentrations in streamwater of agricultural catchments often exhibit interannual variations, which are supposed to result from land‐use changes, as well as seasonal variations mainly explained by the effect of hydrological and biogeochemical cycles. In catchments on impervious bedrock, seasonal variations of nitrate concentrations in streamwater are usually characterized by higher nitrate concentrations in winter than in summer. However, intermediate or inverse cycles with higher concentrations in summer are sometimes observed. An experimental study was carried out to assess the mechanisms that determine the seasonal cycles of streamwater nitrate concentrations in intensive agricultural catchments. Temporal and spatial patterns of groundwater concentrations were investigated in two adjacent catchments located in south‐western Brittany (France), characterized by different seasonal variations of streamwater nitrate concentrations. Wells were drilled across the hillslope at depths ranging from 1·5 to 20 m. Dynamics of the water table were monitored and the groundwater nitrate and chloride concentrations were measured weekly over 2 years. Results highlighted that groundwater was partitioned into downslope domains, where denitrification induced lower nitrate concentrations than into mid‐slope and upslope domains. For one catchment, high subsurface flow with high nitrate concentrations during high water periods and active denitrification during low water periods explained the higher streamwater nitrate concentrations in winter than in summer. For the other catchment, the high contribution of groundwater with high nitrate concentrations smoothed or inverted this trend. Increasing bromide/chloride ratio and nitrate concentrations with depth argued for an effect of past agricultural pressure on this catchment. The relative contribution of flows in time and correlatively the spatial origin of waters, function of the depth and the location on the hillslope, and their chemical characteristics control seasonal cycles of streamwater nitrate concentrations and can influence their interannual trends. Copyright © 2004 John Wiley & Sons, Ltd.

NITRATE IN RIVER AND SUBSURFACE DRAINAGE FLOWS FROM AN EAST CENTRAL ILLINOIS WATERSHED

The objective of this study was to quantify the effects of crop management systems on the movement of nitrate to a drinking water reservoir in a watershed with intensive row-crop agriculture and sub-surface drainage in eastern Illinois (USA). Nitrate concentrations and sub-surface tile flow were monitored for six years at fields with various tillage and cropping management practices; the eight tile systems drained areas varying from 3 to 21 ha. Nitrate concentrations were also determined at various locations along the main stream of the watershed at locations that defined watershed sizes from 6910 to 48 900 ha. Concentrations of nitrate-N in the river followed a pronounced seasonal cycle, with maximum concentrations between 10 and 15 mg/L occurring in the spring and minimum concentrations of 0 to 5 mg/L occurring in the autumn. There were no significant differences in nitrate concentrations among specific sampling locations along the river, suggesting that the entire watershed is contributing more or less equally to the nitrate load. Nitrate-N concentrations from the tile drains varied from 0 to 39 mg/L and differed among field and cropping management systems used. Seasonal variations of nitrate concentrations in tile drain effluent were not as well defined as observed in the river. Nitrate-N concentrations in tile drain effluent were higher from fields where greater amounts of nitrogen fertilizer were applied, particularly when the fertilizer was applied prior to planting. Pre-plant application systems with average nitrogen application of 107 kg-N/ha/yr yielded a mean concentration of nitrate-N of 16.8 mg/L in the tile drain outflow which was significantly greater than the mean concentration of nitrate-N of 10.2 mg/L from the side dress and manure application systems that had received an average nitrogen application of 93 kg-N/ha/yr. The mean concentration of nitrate-N in tile drain discharge from continuous grass was 1.0 mg/L. Nitrate-N losses from cropped fields ranged from 14 to 35 kg/ha/yr depending upon the management system, which were 14 to 36% of the nitrogen applied. Losses from the grassed system were 3.8 kg/ha/yr and at the most upstream river station were 11 kg/ha/yr of nitrate-N.

Monitoring shallow groundwater quality in agricultural watersheds in Denmark

Monitoring of shallow groundwater quality is part of the Danish Agricultural Watershed Monitoring Programme. The monitoring program provides fast and field-related information on impacts of changes in agricultural practices on a watershed scale. The monitoring concept described is carried out in six well-defined hydrological basins and includes new types of groundwater nests and soil water stations. Results from the first three years are presented through examples from the clayey till watershed Lillebaek and the sandy watershed Barslund Baek. By averaging concentrations of solutes in groundwater sampled at the same depth on a monthly basis, it is possible to evaluate trends in the overall impact of climate and different agricultural practices in a watershed on the groundwater quality. Characteristic seasonal variations in nitrate concentrations related to water level fluctuations was observed. The monitoring has demonstrated significantly higher nitrate concentrations in groundwater sampled downgradient of fields receiving manure than in groundwater sampled downgradient of fertilized fields. Significant vertical nitrate reduction downgradient of manured fields was observed in both the sandy and the clayey watershed though above the redoxcline. In the clayey till watershed fast vertical transport and insignificant nitrate reduction was observed downgradient of fertilized fields probably due to fracture and macro-pore flow.

Application of the model niccce to the Solling spruce site

A model for turnover of C and N in coniferous ecosystems has been applied to the long-term data set available for the Solling spruce site in Germany. The model ( niccce; NItrogen Isotopes and Carbon Cycling in Coniferous Ecosystems) simulates water and heat transport, primary production, and turnover of C and N for coniferous forest on a multi-layer soil profile. Application of the model to the Solling site involved calibration to the specific soil conditions and tree species present at this site. Observed amounts of throughfall, pressure heads of soil water, and chloride concentrations at various depths were satisfactory reproduced by the model, as well as concentrations and fluxes of C and N in various tree compartments. Leaching of nitrate below the rooting zone, amounting to 18 kmol ha −1 over a 17-year period, was simulated well, but some annual and seasonal variations of nitrate concentrations could not be reproduced by the model. In particular the large annual variations in nitrate concentrations observed below the litter layer were not satisfactory reproduced.

Phytoplankton Dynamics in Three Rocky Mountain Lakes, Colorado, U.S.A.

In 1984 and 1985 seasonal changes in phytoplankton were studied in a system of three lakes in Loch Vale, Rocky Mountain National Park, Colorado. Three periods were evident: (1) A spring bloom, during snowmelt, of the planktonic diatom Asterionellaformosa, (2) a midsummer period of minimal algal abundance, and (3) a fall bloom of the blue-green alga Oscillatoria limnetica. Seasonal phytoplankton dynamics in these lakes are controlled partially by the rapid flushing rate during snowmelt and the transport of phytoplankton from the highest lake to the lower lakes by the stream, Icy Brook. During snowmelt, the A. formosa population in the most downstream lake has a net rate of increase of 0.34 d-l, which is calculated from the flushing rate and from the A. formosa abundance in the inflow from the upstream lake and in the downstream lake. Measurement of photosynthetic rates at different depths during the three periods confirmed the rapid growth of A. formosa during the spring. The decline in A. formosa after snowmelt may be related to grazing by developing zooplankton populations. The possible importance of the seasonal variations in nitrate concentrations were evaluated in situ enrichment experiments. For A. formosa and 0. limnetica populations, growth stimulation resulted from 8- or 16-micromolar amendments of calcium nitrate and sulfuric acid, but the reason for this stimulation could not be determined from these experiments.