Reduce Nitrate Concentrations Research Articles

Fertilizer standards for controlling groundwater nitrate pollution from agriculture: El Salobral-Los Llanos case study, Spain

Summary Although the legislation on groundwater quality targets pollutant concentration, the effects of measures on non-point source pollution control are often evaluated in terms of their emission reduction potential at the source, not on their capacity of reducing the pollutant concentration in groundwater. This paper applies a hydro-economic modelling framework to an aquifer, El Salobral-Los Llanos aquifer (Mancha Oriental, Spain), where nitrate concentrations higher than those allowed by the EU Water Framework Directive and Groundwater Directive are locally found due to the intense fertilizer use in irrigated crops. The approach allows defining the economically optimal allocation of spatially variable fertilizer standards in agricultural basins using a hydro-economic model that links the fertilizer application with groundwater nitrate concentration at different control sites while maximizing net economic benefits. The methodology incorporates results from agronomic simulations, groundwater flow and transport into a management framework that yields the fertilizer allocation that maximizes benefits in agriculture while meeting the environmental standards. The cost of applying fertilizer standards was estimated as the difference between the private net revenues from actual application and the scenarios generated considering the application of the standards. Furthermore, the cost of applying fertilizer standards was compared with the cost of taxing nitrogen fertilizers in order to reduce the fertilizer use to a level that the nitrate concentration in groundwater was below the limit. The results show the required reduction of fertilizer application in the different crop areas depending on its location with regards to the control sites, crop types and soil–plant conditions, groundwater flow and transport processes, time horizon for meeting the standards, and the cost of implementing such a policy (as forgone benefits). According to the results, a high fertilizer price would be required to reduce nitrate concentrations in groundwater below the standard of 50 mg/l. In this particular case, it is more cost-efficient to apply standards to fertilizer use than taxes, although the instrument of fertilizer standards is more difficult to implement and control.

The potential to improve water quality in the middle Rio Grande through effective wetland restoration

The Rio Grande, which forms the United States-Mexico border for much of its course, receives diverse pollutants from both urban and agricultural areas, most notably in the sister cities of El Paso (TX, USA)-Ciudad Juárez (CHI, Mexico). This study aimed to describe regional trends in water quality in waters near the El Paso-Ciudad Juárez metroplex and to examine the potential for water quality improvement through the use of a created wetland. Very few differences in nutrient chemistry were found among drains, canals and the Rio Grande, with the exception of elevated chloride and lower phosphorus levels found in the drains. Overall, chloride concentrations increased with distance downstream, likely due to concentration of salts via evaporation from irrigated agriculture. A wastewater treatment plant (WWTP) contributed substantially to total phosphorus and nitrate levels, which, together with ammonia, tended to exceed state criteria for water quality downstream of the WWTP outflow. The created Rio Bosque wetlands reduced nitrate concentrations in the water, possibly via denitrification enhanced by algae; algae increased in biomass as water flowed through the wetlands. However, the diversion of water for irrigated agriculture, resulting in the absence of water, and thus aquatic plants, in the wetland in the summer has limited the ability of this wetland to improve regional water quality.

An investigation of nitrate and iron concentrations and their relationship in shallow groundwater systems of Kathmandu

Groundwater is vulnerable to contamination by chemicals, including nitrate, which can pass through soil to the shallow groundwater systems. Nitrate-N is commonly used as an environmental indicator to trace the impact of anthropogenic activities on groundwater. An understanding of the fate of nitrate in groundwater is vital for managing risks associated with nitrate pollution to safeguard groundwater supplies. Hence, groundwater samples were collected in ninety wells of shallow groundwater systems of Kathmandu, Nepal including shallow tube wells, dug wells and stone spouts (locally called Dhunge Dharas). The samples were analyzed for nitrate-nitrogen (NO3-N), iron (Fe) along with pH and temperature. The nitrate-nitrogen and iron (Fe) concentrations ranged from 0.0 to 26.4 and 0.0 to 5.24 mg/L, respectively. An understanding of the relationship between nitrate and iron in groundwater is crucial to explore the mechanism of natural denitrification and its ability to reduce nitrate concentrations. In general, elevated nitrate concentrations were not found in sampled groundwater sources in study area where elevated iron concentrations were common. The observed negative correlations between nitrate and iron suggest that the nitrate in shallow groundwater is being consumed. Moreover, this study highlights the current status and trends of the nitrate and iron in shallow groundwater systems and their relationship to water depth and well types.

Effects of Groundwater‐Flow Paths On Nitrate Concentrations Across Two Riparian Forest Corridors1

Speiran, Gary K., 2010. Effects of Groundwater‐Flow Paths on Nitrate Concentrations Across Two Riparian Forest Corridors. Journal of the American Water Resources Association (JAWRA) 46(2):246‐260. DOI: 10.1111/j.1752‐1688.2010.00427.xAbstract: Groundwater levels, apparent age, and chemistry from field sites and groundwater‐flow modeling of hypothetical aquifers collectively indicate that groundwater‐flow paths contribute to differences in nitrate concentrations across riparian corridors. At sites in Virginia (one coastal and one Piedmont), lowland forested wetlands separate upland fields from nearby surface waters (an estuary and a stream). At the coastal site, nitrate concentrations near the water table decreased from more than 10 mg/l beneath fields to 2 mg/l beneath a riparian forest buffer because recharge through the buffer forced water with concentrations greater than 5 mg/l to flow deeper beneath the buffer. Diurnal changes in groundwater levels up to 0.25 meters at the coastal site reflect flow from the water table into unsaturated soil where roots remove water and nitrate dissolved in it. Decreases in aquifer thickness caused by declines in the water table and decreases in horizontal hydraulic gradients from the uplands to the wetlands indicate that more than 95% of the groundwater discharged to the wetlands. Such discharge through organic soil can reduce nitrate concentrations by denitrification. Model simulations are consistent with field results, showing downward flow approaching toe slopes and surface waters to which groundwater discharges. These effects show the importance of buffer placement over use of fixed‐width, streamside buffers to control nitrate concentrations.

AN ATTEMPT FOR REDUCING MINERAL FERTILIZATION IN LETTUCE PRODUCTION BY USING BIO-ORGANIC FARMING SYSTEM

ISHS IV International Symposium on Ecologically Sound Fertilization Strategies for Field Vegetable Production AN ATTEMPT FOR REDUCING MINERAL FERTILIZATION IN LETTUCE PRODUCTION BY USING BIO-ORGANIC FARMING SYSTEM

Decrease in Nitrate Concentration in Leafy Vegetables Under a Solid-state Illuminator

We report on a substantial reduction of nitrate concentration in leafy vegetables that were subjected to short-term preharvest treatment by narrow-bandwidth red light of high photosynthetic photon flux density generated by a solid-state illuminator. Lettuce (Lactuca sativa cv. Grand rapids), marjoram (Majorana hortensis, Moench.), and green onions (Allium cepa, L. cv. Lietuvos didieji) were grown to harvest time within a greenhouse under daylight with supplementary lighting provided by standard high-pressure sodium lamps (130 μmol·m−2·s−1). A subsequent 3-day treatment within a phytotron under 638-nm light-emitting diodes (500 μmol·m−2·s−1) resulted in the reduction of nitrate concentration by 44% to 65%. The reduction of nitrates was accompanied by an increased concentration of nutritionally valuable carbohydrates, which is also in line with stimulation of expression of nitrate reductase by photosynthetic metabolites. Another indicator of nutritional quality, the content of vitamin C, exhibited some variation that was not directly correlated with the nitrate reduction rate that may be attributed to carbohydrate content variation and leaf tissue aging.

Effect of operating parameters on denitrification in an anoxic rotating biological contactor

The presence of nitrate in water and wastewater is a serious environmental problem. Anoxic rotating biological contactors (RBC) are a promising novel technology for nitrate removal. In this study the effect of two carbon/nitrogen (C/N) molar ratios (1.5 and 3.0) on denitrification, using acetate as a carbon source, were investigated in an anoxic bench‐scale RBC, treating synthetic wastewater. The effect of different hydraulic retention times (HRTs) and different nitrogen and carbon influent concentrations on the reactor performance, at constant C/N, were also analysed. The average removal efficiency in terms of nitrogen‐nitrate was about 90.4% at C/N = 1.5, lowering to 73.7% at C/N = 3.0. Considering carbon‐acetate removal, overall efficiencies of 82.0% and 63.6% were attained at C/N ratios of 1.5 and 3.0, respectively. The increase in nitrogen‐nitrate (from 50 to 100 mg N‐NO3 − L−1) and carbon‐acetate influent concentrations and the decrease in HRT, keeping C/N constant, had a slight negative effect in terms of substrate removal. It was found that, for the tested conditions, the use of C/N = 1.5 is advantageous to denitrification. The anoxic RBC was significantly effective at reducing nitrate concentrations within a relatively short HRT. These reactors may be a feasible option for the treatment of nitrate‐rich wastewaters.

Sulfur fertilization and light exposure during storage are critical determinants of the nutritional value of ready‐to‐eat friariello campano (Brassica rapa L. subsp. sylvestris)

AbstractBACKGROUND: The nutritional value of fresh vegetables can be affected at different steps within the field‐to‐market pipeline. Both pre‐ and post‐harvest factors should be considered in order to increase the produce quality and to preserve it until final consumption. In this study the effects of sulfur nutrition during plant growth and light exposure during storage on the nutritional value of ready‐to‐eat friariello campano (Brassica rapa L. subsp. sylvestris L. Janch. var. esculenta Hort.) were studied.RESULTS: Fresh weight loss was higher in light‐storage treatment. During storage, light exposure reduced leaf nitrate content, although no effect could be attributed to sulfur nutrition. Sulfur increased both lipophilic and hydrophilic antioxidant activity. The hydrophilic antioxidant activity linearly decreased during storage, whereas the lipophilic activity increased over time. However, no differences could be attributed to light exposure during storage for this parameter. Results on colorimetric indexes and their relation with the chlorophyll content are also reported.CONCLUSIONS: Ready‐to‐eat friariello quality may be improved with an enhanced antioxidant activity and reduced nitrate content by combining, respectively, increased sulfur availability during plant growth and exposure to light during storage. On the other hand, light exposure caused a more rapid decline in produce fresh weight during storage. Copyright © 2009 Society of Chemical Industry

Time-series modeling of reservoir effects on river nitrate concentrations

Saylorville Reservoir is a 24.1 km 2 impoundment of the Des Moines River located approximately 10 km north of the City of Des Moines, Iowa, USA. Surface water from the Des Moines River used for drinking water supply is impaired for nitrate–nitrogen. Monthly mean nitrate concentration data collected upstream and downstream of the reservoir for a 30-year period (1977–2006) were selected for time-series analysis. Our objectives were to (1) develop a model describing nitrate concentrations downstream of the reservoir as a function of the concentrations entering the reservoir and (2) use the model to provide a 1-month ahead forecast for downstream water quality. Results indicated that downstream nitrate can be effectively modeled using a transfer function approach that utilized inflow concentrations during the current and previous month as input variables. Inflow concentrations were modeled using an AR(20) model, with the higher order model consistent with temporal correlation noted by others. The transfer function model suggested that the reservoir is reducing nitrate concentrations by 22 ± 6%, a reduction that greatly exceeds previous estimates. Monthly nitrate forecasted with the model were nearly all within a 95% prediction interval of their actual measured values and did not appear greatly affected by flow variations.

Supplements of Nickel Affect Yield, Quality, and Nitrogen Metabolism When Urea or Nitrate is the Sole Nitrogen Source for Cucumber

ABSTRACT Influences of nickel (Ni) concentrations in the nutrient solution on yield, quality, and nitrogen (N) metabolism of cucumber plants (Cucumis sativus cv ‘RS189’ and ‘Vikima’) were evaluated when plants were grown either with urea or nitrate as the sole N source. The cucumber plants were treated with two N sources, urea and nitrate as sodium nitrate (NaNO3) at 200 mg L−1, and three concentrations of Ni as nickel sulfate (NiSO4·6H2O; 0, 0.5, and 1 mg L−1). Treatments were arranged in a randomized block design with six replicates. The highest concentration of Ni in the leaves (1.2 mg kg−1 Dwt) was observed in the urea-fed plants at 1 mg L−1 Ni concentration. Additions of Ni up to 0.5 mg L−1 had no effect on the fruit Ni concentration in the both urea and nitrate-fed plants. Yield significantly (p < 0.05) increased with the Ni supplements from 0 to 0.5 mg L−1 (10 and 15% in ‘RS189’ and ‘Vikima’, respectively), but decreased when 1 mg L−1 Ni applied to the solutions in urea-fed plants. Nitrate-fed plants had a higher percentage of total soluble solids compare to those urea-fed plants. Nitrate concentrations of the fruits in urea-fed plants in both cultivars were reduced by approximately 50% compared to those nitrate-fed plants. The reduction of nitrate concentration in the fruits became more pronounced as the Ni concentration increased in the solution. The rate of photosynthesis (Pn) increased with the increase of the Ni concentration in the solution with urea-fed plants. Both N concentration and nitrate reductase (NR) activity of young leaves were higher in urea-fed plants at 0.5 mg l−1 Ni concentration. Ni supplements enhanced the growth and yield of urea-fed plants by increasing Pn, N concentration and NR activity. It can be concluded that Ni supplements (0.5 mg l−1) improve yield, quality, and NR activity in urea-fed cucumber plants.

FERTILIZATION MANAGEMENT TO REDUCING NITRATE ACCUMULATION IN SOME LETTUCE VARIETIES (Lactuca sativa L.) GROWN IN SANDY CALCAREOUS SOILS

The present investigation was conducted during the two seasons of 2005/2006 and 2006/2007 at the Desert experimental Farm of Assiut Agric. Res. Station to study the effect of five levels of N-fertilizer (0, 30, 60, 90 and 120 kg N/fed.) and three levels of composted waste farm (Control (zero), Compost (3 ton/fed.) and bio-compost (3 ton /fed. compost with Biogen). Tow varieties were used in this investigation (Latoga and Balady). These varieties were grown in sandy calcareous soil under drip irrigation system. The interaction between the two fertilizer sources was studied. The results indicated that there were significant differences among the five levels of N fertilizer in all studied characters. Increased for both mineral and organic fertilizer were obtained of both lettuce varieties on yield and its components. Meanwhile, application of composted waste farm at a rate of 3 ton/fed in combination with Biogen reduced the application of mineral N to 50% and reduced nitrate concentration in leaves of both lettuce varieties. Compost and bio-compost as organic and bio fertilizers play an important role in maintaining soil fertility with releasing nutrients in the soil. The most increase in soil N and P content was observed with compost and bio-compost application. The increase percentage in P content over the control was 10.12 and 38.38 in 2006 and 25.58 and 19.08 % in 2007, respectively.

Assessment of nitrate contamination of groundwater using lumped-parameter models

In this paper, lumped-parameter models (LPMs) were developed and utilized to simulate nitrate concentration in the groundwater of Gaza City and Jabalia Camp (GCJC) in the Gaza Coastal Aquifer (GCA) in Palestine. In the GCJC area, nitrate levels exceed the maximum contaminant level (MCL) of 10 mg/L NO 3-N (45 mg/L NO 3) in many wells. Elevated nitrate concentrations in the groundwater of GCJC area are due to the disposal of untreated wastewater, the existence of heavy agriculture in the surrounding areas, and the use of cesspits for wastewater disposal. The developed LPMs utilize monthly time steps and take into consideration all the sources and sinks of water and nitrate in the study area. The main outcomes of the LPMs are the average temporal water table elevation and nitrate concentration. In order to demonstrate LPMs usability, a set of management options to reduce nitrate concentration in the groundwater of the study area were proposed and evaluated using the developed LPMs. Four broad management options were considered where these options tackle the reduction of nitrate concentration in the lateral inflow, rehabilitation of the wastewater collection system, reduction in cesspit usage, and the restriction on the use of nitrogen-based fertilizers. In addition, management options that encompass different combinations of the single management options were taken into account. Different scenarios that correspond to the different management options were investigated. It was found based on the LPMs that individual management options were not effective in meeting the MCL of nitrate. However, the combination of the four single management options with full rehabilitation and coverage of the wastewater collection network along with at least 60% reduction in both nitrate concentration in the lateral inflow and the use of nitrogen-based fertilizers would meet the MCL constraint by the end of the management period.

Spatialization of denitrification by river corridors in regional-scale watersheds: Case study of the Seine river basin

Numerous studies have shown that riparian wetlands are able to reduce nitrate concentration both by plant uptake and by denitrification. Although this function of nitrate removal by riparian wetlands is well established, it remains difficult to quantify, especially at the catchment scale. This paper discusses the nitrate budget approach used to estimate nitrate retention in the riparian zones and related streams. The method is applied in sub-catchments of the Seine basin using data sets available at this scale. As a result, retention rates were computed in 174 embedded catchments, each catchment being defined downstream by a well monitored measurement station of riverine nitrate concentration. Catchments receiving more than the equivalent of 20 hab/km 2 in point source pollution were excluded. The mean of retention rates computed over these 174 catchments is equal to 35%, a value that is in the range of retention rates previously estimated in the Seine river basin. Interpolations of nitrate fluxes are an important source of retention rate estimate uncertainty. To assess the significance level of our results, we changed the input parameters by ±10%. These 10% variations result in an uncertainty range of ±18% of the original rate. The statistical analysis conducted on retention rate confirmed the importance of land cover of the river corridor in the denitrification process, which is favoured by the presence of water and forest. The spatial distribution of retention rates shows a reduction of the retention variability in the most downstream catchments, which is likely linked to the nesting of the catchments. This calls for the separation of nested catchments into independent zones, which should also increase the signal to noise ratio in the variability of the retention rates estimates.

Nitrogen Nutrition Effects on Nitrate Accumulation of Soil‐Grown Greenhouse Butterhead Lettuce

Leafy vegetables are the major source of dietary nitrate intake of humans. Nitrates can have many detrimental effects on human health besides some beneficial effects. A further reduction in nitrate concentration thus can represent added value for vegetable products rich in carotenoids, vitamins C and E, selenium, dietary fiber, plant sterols, and so on. Though nitrate accumulation is governed by a plenitude of factors (i.e., genetic setup, environmental conditions and nutrients), the factor most readily controllable is nitrogen nutrition. This study examined the dependence of butterhead lettuce crops' nitrate concentration on soil mineral nitrogen (N) content. It was shown that the effect of the soil's mineral N content at harvest was strongly associated with the nitrate concentration of lettuce at a low to intermediate mineral N content (<100 kg N ha−1). This demonstrates the importance of N‐fertilization practices. Results of 24 comparative experiments, based on two different N‐fertilization recommendation procedures, did show that an N application difference at the start of the growing period has an effect on the nitrate concentration at harvest. A lower N application at either recommendation resulted in 71% of the experiments (17/24) having a lower leaf nitrate concentration. The head weight was negatively affected in only 2 of these 17 experiments. Minimizing the N input and hence lowering the soil N content at harvest points to the possibility of further reducing the nitrate concentration level in greenhouse lettuce, while having no significant negative effect on economic yield.

Controlling nitrate pollution: An integrated approach

The introduction of the EU Water Framework Directive requires policy to address non-point source pollution as part of an overall integrated strategy to improve the ecological status of water bodies. In this paper, we combine an economic optimisation framework with a dynamic simulation model of N transport in the Kennet Catchment to link decisions taken at the farm level to reductions in nitrate concentrations in the River Kennet. We examine a variety of policies targeted at reducing fertiliser use and changing the way in which farm land is used. We find that a tax on nitrogen emerges as the best policy both in terms of cost- and environmental effectiveness. Such a policy involves a considerable reduction in fertiliser use, as well as, a restructuring of land-use away from arable towards increased use of set-aside. Budgetary implications of such a radical move towards set-aside would be huge and hence unlikely to be politically palatable given the objective of reducing the EU budgetary allocation to agriculture. Additionally, the current rise in world demand for food may also mitigate calls for increasing the proportion of land taken out of agricultural production. Although the study succeeds in establishing a link between actions on the farm and nitrate concentrations in the stream water, further work is required to explore the effect of the retention of nitrates in the unsaturated zone and groundwater on this link.

Estimating the Range of Impacts Arising from Nitrate Leaching Reduction Policies Using Farm Accounts

Declining agricultural incomes, increasing concern over rural poverty and sporadic crises such as those of BSE and Foot and Mouth Disease mean that the imposition of additional costs on UK agriculture are likely to be politically and socially sensitive. Such additional costs are however on the agenda with the implementation of the Water Framework Directive (European Commission, 2000). Like the Nitrates Directive (European Commission, 1991) before it, the WFD aims to, inter alia, reduce nitrate leaching from agriculture. The benefits of reduced nitrate concentrations in rivers and lakes will come at some cost to farms. In this study we assess four possible WFD measures proposed to Defra: reduced inorganic fertiliser application, conversion of arable land to un-grazed grassland, reduced livestock stocking rates and reduced livestock dietary N intakes. For each measure, changes in farm gross margins are estimated using a panel dataset of over 3000 farms. In contrast to previous analyses which have focussed upon mean responses at stylised farms, our approach allows analysis of the range of impacts across a wide variety of real-world farms and farm types. Findings reveal high variability in impacts and cost-effectiveness analysis indicates that, on average, cropping farms seems capable of reducing nitrate leaching in a more cost-efficient way than livestock or dairy enterprises.

Characterization of a Corynebacterium Strain That Can Grow in Medium Containing up to 2 M Nitrate

ABSTRACT A gram-positive bacterium, identified as Corynebacterium K37, was isolated from the waste effluent of a dairy farm. The bacterium thrived and expressed nitrate-reducing activity at nitrate concentrations of up to 2 M, and reduced nitrate concentration from 0.4 M to 11.4 mM and also from 0.4 M to 23.4 mM in aerobic and anaerobic fed-batch cultures, respectively. Cells of K37 were able to utilize a variety of carbon sources for nitrate reduction with little or no accumulation of nitrite. In aerobic cultures, the residual nitrite was minimal and it was completely reduced after prolonged incubation. Growth on acetate or pyruvate in anaerobic cultures resulted in lower nitrite reductase activities and concomitant higher residual nitrite concentrations than did growth on ethanol or glucose, suggesting that diminished electron availability was a factor in the accumulation of residual nitrite. The bacterium also survived in 2 M concentrations of NaCl, KCl, and CaCl2. Corynebacterium sp. K37 may be useful in bioremediation of high nitrate pollution in contaminated soils and water.

Biological denitrification by Pseudomonas stutzeri immobilized on microbial cellulose

This study demonstrated the feasibility of a biological denitrification process using immobilized Pseudomonas stutzeri. The microbial cellulose (MC) from Acetobacter xylinum was used as the support material for immobilization of the bacterium. Nitrate removal took place mainly in the anoxic system. The effects of various operating conditions such as the initial nitrate concentration, pH, and carbon source on biological denitrification were demonstrated experimentally. The system demonstrated a high capacity for reducing nitrate concentrations under optimum conditions. The denitrification rate increased up to a maximal value of 1.6 kg NO3-N m−3 day−1 with increasing nitrate loading rate. Because of its porosity and purity, MC may be considered as appropriate supports for adsorbed immobilized cells. The simplicity of immobilization and high efficiency in operation are the main advantages of such systems. To date, the immobilization of microorganisms onto MC has not been carried out. The results of this research shows that a pilot bioreactor containing P. stutzeri immobilized on MC exhibited efficient denitrification with a relatively low retention time.

The Effects of Subsurface Drainage Depth and Intensity on Nitrate Loads in the Northern Cornbelt

Nitrate loads to surface waters from croplands in the Mississippi River basin are considered a leading cause of hypoxia in the Gulf of Mexico. Subsurface (tile) drainage systems exacerbate nitrate loads to surface waters by providing a pathway for the transport of soluble compounds from the crop rooting zone. This work investigated the role of subsurface drainage depth and drainage intensity (theoretical drainage rate) on nitrate loads to subsurface drains through field experimentation over a five-year period (2001-2005). Subsurface drainage plots were installed on nine subfield-sized plots ranging in size from 0.8 to 2.5 ha. The nine plots comprised two drainage depths (90 and 120 cm) and two drainage intensities: a conventional intensity of 13 mm d-1 design drainage rate and a high intensity of 51 mm d-1, obtained by using one-half the drain spacing of the conventional system. Subsurface drainage volume and nitrate loads in subsurface drainage outflows were monitored with automated equipment over the five-year period. Reductions in annual drainage volume and nitrate loads were observed with shallow and less intense drainage as compared to conventional depth and more intense drainage, respectively, in every year of the study. However, annual differences among treatments were not statistically significant due to variability among the nine plots. An analysis of aggregated data across the five study years of data showed statistically significant reductions in both drainage volume and nitrate loads of 20% and 18%, respectively, for drains placed 30 cm shallower than the 120 cm conventional depth drains. Reductions in nitrate loads were attributed primarily to reductions in annual drainage volume rather than reductions in nitrate concentrations. Subsurface drains placed at shallower depths, without reducing design drainage rates, may provide environmental benefits compared to conventionally designed, deeper drainage systems.

Changes of nutrient concentrations in water sensitive to nitrate pollution from agricultural sources in the Samica Stęszewska river catchment

Changes of nutrient concentrations in water sensitive to nitrate pollution from agricultural sources in the Samica Steszewska river catchment. The aim of this study was to evaluate the surface water quality during the fi rst period of measures undertaken to reduce nitrate concentrations in the nitrate vulnerable zone. The study was carried out in the upper part of the Samica Steszewska catchment, located in the Wielkopolska region (western Poland), designated by the nitrate directive as a nitrate vulnerable zone (Nitrate Directive 91/676/EC). Water samples were taken at nine control points from February 2003 to December 2007. The results indicate that nitrate pollution reduction measures taken in the nitrate vulnerable zones were ineffective in reducing this type of pollution. Water quality was poor at almost all of the monitoring points, and based on nitrate concentrations, water quality was classifi ed in classes IV or V. The only exception was in the outfl ow from Lake Niepruszewskie, where water quality was classifi ed as either class I, II or III. Also water quality in Lake Niepruszewskie was extremely eutrophic. Our results indicated a role of Lake Niepruszewskie as a nutrient sink reducing pollution from the