Nitrogen Concentrations In Groundwater Research Articles

Groundwater nitrogen concentration changes in an urbanized area of Indonesia over ten years period

Nitrogen in groundwater poses environmental concerns in Bandung Region, Indonesia, due to natural and anthropogenic factors. The predominant component of the region’s aquifer is high-hydraulic-conductivity volcanic rock, one of the natural vital factors that make the aquifer vulnerable to contamination. Another factor is urbanization which has been reported to be an adverse effect of high nitrogen levels in the groundwater, particularly the unconfined system. This study’s objective was to evaluate urbanization’s impact on dissolved inorganic nitrogen concentrations over a 10-year period, which had not been explained by previous research. The evaluation focused on land-use changes in the southern part of the Bandung Region and their relation to dissolved inorganic nitrogen (DIN) in unconfined groundwater. A total of 88 samples were collected in 2009, 2015, and 2018 from three types of land-use: residential, plantations, and paddy fields. From 2009 to 2018, land use changes were visible, with an 8% and 6% increase in urban settlements and rice fields, respectively, and a 15% reduction in plantations. Furthermore, over a decade, agricultural and rice fields substantially impacted the NO3 − levels, contributing approximately 13.2 mg/L and 9.9 mg/L, respectively. In the meantime, the settlement area significantly contributed to the 3.25 mg/L increase in the NH4 + levels.

Imputation of Ammonium Nitrogen Concentration in Groundwater Based on a Machine Learning Method

Ammonium is one of the main inorganic pollutants in groundwater, mainly due to agricultural, industrial and domestic pollution. Excessive ammonium can cause human health risks and environmental consequences. Its temporal and spatial distribution is affected by factors such as meteorology, hydrology, hydrogeology and land use type. Thus, a groundwater ammonium analysis based on limited sampling points produces large uncertainties. In this study, organic matter content, groundwater depth, clay thickness, total nitrogen content (TN), cation exchange capacity (CEC), pH and land-use type were selected as potential contributing factors to establish a machine learning model for fitting the ammonium concentration. The Shapley Additive exPlanations (SHAP) method, which explains the machine learning model, was applied to identify the more significant influencing factors. Finally, the machine learning model established according to the more significant influencing factors was used to impute point data in the study area. From the results, the soil organic matter feature was found to have a substantial impact on the concentration of ammonium in the model, followed by soil pH, clay thickness and groundwater depth. The ammonium concentration generally decreased from northwest to southeast. The highest values were concentrated in the northwest and northeast. The lowest values were concentrated in the southeast, southwest and parts of the east and north. The spatial interpolation based on the machine learning imputation model established according to the influencing factors provides a reliable groundwater quality assessment and was not limited by the number and the geographical location of samplings.

Coastal Tourism and Its Influence on Wastewater Nitrogen Loading: A Barrier Island Case Study.

Package treatment plants (PTPs) are facilities designed to treat onsite wastewater for small communities, commercial, and residential developments. PTPs are being utilized in a growing number of coastal communities. This study estimated the effects of coastal tourism on onsite wastewater nitrogen (N) inputs to a barrier island surficial aquifer (Bogue Banks, NC). The N-removal effectiveness was assessed for seven PTPs that treated wastewater from vacation properties using a range of technologies: extended aeration; sequencing batch reactor; and advanced media filtration. Influent and effluent wastewater samples were collected monthly from Feb. 2014 to Jan. 2015 and analyzed for particulate and dissolved N. Increased summer visitation associated with coastal tourism resulted in an increase in water use, wastewater inputs, and PTP N loading to the surficial aquifer. However, extended aeration systems did not have significantly elevated TN loads during the summer months because their treatment efficiency increased. N inputs associated with coastal tourism made up approximately 51% of the annual wastewater-related N load to the surficial aquifer. Onsite wastewater N-loading to the surficial aquifer (6.7 kg-N/ha/yr) appeared to be the dominant source of N loading on the island. Water quality data indicated that these N inputs have resulted in increased groundwater NO3 concentrations in the surficial aquifer. Overall, wastewater inputs added approximately 4.6 cm of groundwater recharge annually to the island. Coastal tourism can result in measurable increases in wastewater N loading, groundwater nitrogen concentrations, and groundwater recharge.

The Nitrate Nitrogen in Groundwater of Intensive Agricultural Region in Pinggu District by Sampling and Monitoring for 12 Years

The nitrate nitrogen of groundwater samples which sampled 24 times from 2006 to 2017 in the intensive agricultural region of Pinggu district in Beijing were analyzed in this study, in order to investigate its dynamic change and important influence factors of this region. The results indicated that the mean value of nitrate nitrogen in groundwater of this region was 6.23 mg/L, which had reached the third level of the national groundwater quality standard, and the annual nitrate nitrogen concentration in groundwater of the region tended to increase. The significant positive correlations between the annual average concentrations of nitrate nitrogen in groundwater and the statistical data of livestock and poultry products from 2006 to 2015 implied that the impact of livestock and poultry industry on the nitrate in groundwater should not be ignored in the region. The increase of precipitation has a trend of increasing the difference of nitrate in groundwater in Pinggu district. The nitrate nitrogen in groundwater sampled from orchard was markedly higher than which from grain field and vegetable field. Samples from deeper well (WD3) always locatd in mountainous area, their nitrate nitrogen was significantly higher than which from spring well (WD1) and well with 30 to 100 m depth (WD2).

The impact of an underground cut-off wall on nutrient dynamics in groundwater in the lower Wang River watershed, China

ABSTRACTUnderground cut-off walls in coastal regions are mainly used to prevent saltwater intrusion, but their impact on nutrient dynamics in groundwater is not clear. In this study, a combined analysis of multiple isotopes () and nitrogen and phosphorus concentrations is used in order to assess the impact of the underground cut-off walls on the nutrient dynamics in groundwater in the lower Wang River watershed, China. Compared with the nitrogen and phosphorus concentrations in groundwater downstream of the underground cut-off walls, high and total dissolved nitrogen concentrations and similar concentration levels of and total dissolved phosphorus are found in groundwater upstream of the underground cut-off walls. The isotopic data indicated the probable occurrence of denitrification and nitrification processes in groundwater upstream, whereas the fingerprint of these processes was not shown in groundwater downstream. The management of fertilizer application is critical to control nitrogen concentrations in groundwater restricted by the underground cut-off walls.

Impact of agriculture and land use on nitrate contamination in groundwater and running waters in central-west Poland.

Protected areas due to their long-term protection are expected to be characterized by good water quality. However, in catchments where arable fields dominate, the impact of agriculture on water pollution is still problematic. In Poland, recently, the fertilization level has decreased, mostly for economic reasons. However, this applies primarily to phosphorus and potassium. In order to evaluate the impact of agriculture on water quality in a protected area with a high proportion of arable fields in the aspect of level and type of fertilization, complex monitoring has been applied. The present study was carried out in Wielkopolska National Park and its buffer zone, which are protected under Natura 2000 as Special Areas of Conservation and Special Protection Areas. The aim of the study were (1) to assess the impact of agriculture, with special attention on fertilization, on groundwater, and running water quality and (2) to designate priority areas for implementing nitrogen reduction measures in special attention on protected areas. In our study, high nitrogen concentrations in groundwater and surface waters were detected in the agricultural catchments. The results demonstrate that in the watersheds dominated by arable fields, high nitrogen concentrations in groundwater were measured in comparison to forestry catchments, where high ammonium concentrations were observed. The highest nitrogen concentrations were noted in spring after winter freezing, with a small cover of vegetation, and in the areas with a high level of nitrogen application. In the studied areas, both in the park and its buffer zone, unfavorable N:P and N:K ratios in supplied nutrients were detected. Severe shortage of phosphorus and potassium in applied fertilizers is one of the major factors causing leaching of nitrogen due to limited possibilities of its consumption by plants.

Impact of land use on nitrogen concentration in groundwater and river water

The aim of this study was to evaluate the impact of land use on nitrate nitrogen (NO3-N) in shallow groundwater (G-N) and total nitrogen (N) in river water (R-N). The study area consisted of 26 watersheds (1342 km2) covering 72% of Kagawa Prefecture in Japan. We estimated G-N specific concentrations, which showed the magnitude of the upland fields, paddy fields, forests and urban land-use contributions to watershed-mean G-N. G-N specific concentrations were gained as partial regression coefficients using a multiple regression analysis of the watershed-mean G-N concentrations and the land-use ratios in each of the 26 watersheds. The results showed that the G-N specific concentration, which was gained as the partial regression coefficient for the multiple regression analysis, was 15.2 mg L−1, 10.3 mg L−1, 2.3 mg L−1 and 2.5 mg L−1 for the upland fields, paddy fields, forests and urban land-use types, respectively. R-N pollution load runoff to the river mouth was calculated by multiplying R-N specific concentration (previously reported) by river flow at the river mouth. Similarly, G-N pollution load arrival to groundwater was calculated by multiplying G-N specific concentration by the groundwater flow. The R-N pollution load runoff was 19.3 kg ha−1 y−1, 7.7 kg ha−1 y−1, 1.7 kg ha−1 y−1 and 7.6 kg ha−1 y−1, while the G-N pollution load arrival was 7.3 kg ha−1 y−1, 5.0 kg ha−1 y−1, 1.1 kg ha−1 y−1 and 1.2 kg ha−1 y−1, for upland fields, paddy fields, forests and urban areas, respectively. These results showed that the N in river water and groundwater was derived mainly from runoff and leaching from croplands. Therefore, the relationships between watershed-mean non-absorbed, applied nitrogen (NAA-N: nitrogen applied to cropland via fertilizer and manure without being absorbed by crops), R-N concentration and watershed-mean G-N concentration were investigated. A curvilinear correlation was observed between NAA-N and R-N concentrations (r2 = 0.68) except for one small, high-density, urban watershed, and a weak linear correlation was observed between NAA-N and G-N concentrations (r2 = 0.42).

Wastewater Nitrogen Contributions to Coastal Plain Watersheds, NC, USA

Nitrogen inputs to coastal watersheds have been linked to eutrophication. However, the role that domestic sources of wastewater play in contributing nitrogen to coastal watersheds is not well known in the southeastern USA. In a yearlong study (2011–2012), nitrogen concentrations were compared in watersheds served by septic systems and a centralized sewer system in the Coastal Plain of North Carolina. Surface and groundwater samples from septic systems and sewer watersheds were analyzed for total dissolved nitrogen (TDN), total nitrogen, and nitrogen and oxygen isotopes in nitrate. Groundwater beneath the drainfield and adjacent to streams had median concentrations of TDN at 5.9 and 4.4 mg/L, respectively. Additionally, median groundwater-transported loads of TDN to the stream from septic systems sites (0.6 kg-TDN/year) were significantly greater than sites in sewer watersheds (0.2 kg-TDN/year). Isotopic analyses revealed that effluent from septic systems was the primary source of nitrate in watersheds served by septic systems, while fertilizer and/or soil organic matter were dominant sources of nitrate in sewer watersheds. Nitrogen exported from septic systems contributed to elevated nitrogen concentrations in groundwater and streams throughout the watershed, whereas nitrogen exports from sewers were focused at a single point source and affected surface water concentrations. Based on watershed TDN exports from septic systems minus TDN exports from sewers watersheds, it was estimated that septic systems contributed 1.6 kg TDN/ha/year to watershed exports of TDN. Overall, septic systems and sewers contributed to elevated nitrogen loading and should be considered in nutrient-sensitive watershed management.

Satellite and in situ derived corn and soybean biomass and leaf area index: Response to controlled tile drainage under varying weather conditions

Controlled tile drainage (CTD) has environmental and crop production benefits, but the effects of CTD on crop growth under varying weather conditions is not well-documented. This study evaluates the responsiveness of field-scale corn and soybean growth from CTD and uncontrolled tile drainage (UCTD) under varying seasonal temperature and rainfall in eastern Ontario, Canada. Leaf area index (LAI) and total above-ground dry biomass were used as crop growth indicators and were estimated from in situ data and satellite imagery between 2005 to 2013. Corn LAI from CTD fields was maintained or significantly higher relative to the LAI from UCTD fields, in 92% of all site-years; corn biomass from CTD fields was also maintained or significantly higher in all site-years of the study in which it was determined. For soybean, LAI from CTD fields was maintained or significantly higher in 67% of the site-years; biomass from CTD fields was maintained in all site years in which it was determined. Higher water tables and soil water contents, and slightly higher groundwater nitrogen concentrations in CTD fields, may explain these responses. Cohen’s d effect size of satellite derived LAI ([Mean CTD LAI−mean UCTD LAI]/pooled standard deviation) for corn was negatively related to total May–August precipitation indicating a stronger CTD effect with a decrease in precipitation. In contrast to the corn results, Cohen’s d of satellite-derived LAI for soybeans was positively related to total May–August (and especially May–July) precipitation, indicating a stronger CTD effect with an increase in precipitation. Results herein could be used to help inform how to optimize the use of growing season CTD for different crops in order to enhance crop growth properties.

Soils, slopes and source rocks: Application of a soil chemistry model to nutrient delivery to rift lakes

The topographic evolution of rift basins may be critical to the deposition of lacustrine source rocks such as the organic-rich Lower Cretaceous shales of the South Atlantic margin. Soils have been proposed as a key link between topography and source rock deposition by providing nutrients for the algae growth in rift lakes. Decreasing topographic relief from active rift to late rift has several effects on soils: soils become thicker and finer, erosion of dead surface and soil organic matter decreases, and the fractionation of precipitation between runoff and infiltration may favor increased infiltration.This hypothesis is tested by application of CENTURY, a complex box model that simulates transfer of nutrients within soil pools. The model is first applied to a rainforest soil, with several parameters individually varied. Infiltration experiments show that the concentrations of C, N and P in groundwater decrease rapidly as infiltration decreases, whether due to increased slope or to decreased precipitation. Increased erosion of surface plant litter and topsoil results in substantially decreased nutrient concentrations in groundwater. Increased sand content in soil causes an increase in nutrient concentration.We integrate these variables in analyzing topographic swathes from the Rio Grande Rift, comparing the southern part of the rift, where topography is relatively old and reduced, to the northern rift. C and P concentrations in groundwater increase as slope gradient decreases, resulting in substantially larger C and P concentrations in groundwater in the southern rift than the northern rift. Nitrogen concentrations in groundwater depends on whether infiltration varies as a function of slope gradient; in experiments where the fraction of infiltrated precipitation decreased with increasing slope, N concentrations was also substantially higher in the southern rift; but in experiments where that fraction was held constant, N concentrations was lower in the southern rift. These simulations demonstrate that evolving topography during rift development can significantly influence nutrient concentrations in groundwater and, if these nutrients flow into rift lakes and stimulate organic productivity, account for the deposition of rich oil-prone source rocks in late rift stages.

Investigation of the Nitrogen Concentration in Groundwater and River Water and Nitrogen Loads to the Environment in Yanbian, Jilin, China

Investigation of the Nitrogen Concentration in Groundwater and River Water and Nitrogen Loads to the Environment in Yanbian, Jilin, China

基于ArcGIS的下辽河平原地下水脆弱性评价及空间结构分析

PDF HTML阅读 XML下载 导出引用 引用提醒 基于ArcGIS的下辽河平原地下水脆弱性评价及空间结构分析 DOI: 10.5846/stxb201403280580 作者: 作者单位: 辽宁师范大学城市与环境学院,辽宁师范大学城市与环境学院 作者简介: 通讯作者: 中图分类号: 基金项目: 教育部高等学校博士点基金(2012123611000);国家自然科学基金(40501013) An ArcGIS-based analysis of groundwater spatial structure and groundwater vulnerability in the lower reaches of the Liaohe River Plain Author: Affiliation: College of Urban and Environment,Liaoning Normal University,College of Urban and Environment,Liaoning Normal University Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:以下辽河平原为研究区,通过选取1991、2000和2010年3个代表年的相关参数,在DRASTIC模型基础上构建评价指标体系进行地下水脆弱性评价,并以地下水中氮元素浓度为响应指标通过显著性检验,在此基础上借助GS+、ArcGIS和Geoda095i等软件的制图功能和空间统计分析功能,对下辽河平原地下水脆弱性的空间分布特征、变异规律以及空间关联格局进行研究分析,结果表明:①1991-2010年下辽河平原地下水脆弱性总体上呈先增后减趋势,空间分布上以沈阳市为中心的地下水高脆弱区向南部沿海方向扩散;②1991-2010年研究区地下水脆弱性Moran's I表现为较强正相关现象,且关联程度呈略微下降趋势;③1991-2010年研究区地下水脆弱性局部空间自相关和显著性水平均发生了明显的变化;④研究区内地下水脆弱性受结构性因素和随机性因素共同作用,且随机性因素在3个时期内有逐步上升趋势。研究成果反映了研究区地下水脆弱性空间结构的变异规律及驱动机制,为决策者在未来地下水污染防治方面提供相关参考依据。 Abstract:High-quality groundwater bodies with relatively stable water volumes, good water quality, and a high resistance to pollution are widely distributed throughout the world. They play an important role in, among other things, the domestic water supply, economic development, and maintaining the integrity of the geological environment and ecological balance. However, with rapid socio-economic development, increasing human demand for water has resulted in increasing pressure on, and unreasonable use of, groundwater bodies. Consequently, groundwater systems throughout the world are subject to varying degrees of pollution and destruction, one result of which is an increasing disequilibrium between the supply of and demand for water resources.The field of international hydrogeology is concerned with evaluation of groundwater vulnerability, which is considered a basic task in the development and protection of groundwater resources. Currently, groundwater vulnerability is thought to result from characteristics of the groundwater system itself and anthropogenic factors; research into groundwater vulnerability can support groundwater protection. GIS, together with the contraposed index method, is the most popular tool for calculating groundwater vulnerability indices. Because the hydrogeological environment is not under the complete control of human activities, a thorough understanding of groundwater vulnerability and the causes of its variation is necessary for environmental managers to enact preventive and pollution control measures.This study was based on the DRASTIC model. Groundwater parameters for 3 years (1991, 2000, and 2010) were used to calculate the distribution of groundwater vulnerability in the lower reaches of the plain of the Liaohe River, using ArcGIS. Groundwater nitrogen concentration was used as a response index to test the reliability of results. Using the mapping and spatial statistical analysis functions in GS+, ArcGIS, and Geoda095i, we evaluated and analyzed the spatial distribution, variation, and spatial correlation patterns of groundwater vulnerability in the tested area. Results showed that:1) Overall groundwater vulnerability initially decreased but then showed a trend of increase from 1991 to 2010, and high-vulnerability areas were distributed from the regions around Shenyang to the south coast. 2) From 1991 to 2010, groundwater vulnerability showed a strong positive autocorrelation (Moran's I), the degree of which showed a slight downward trend. 3) Over the study period, marked changes have occurred in local spatial autocorrelation of groundwater vulnerability and its significance levels. 4) Groundwater vulnerability in the study area was influenced by a combination of structural and random factors. While the random factors have gradually increased over time, structural factors remain important. This study highlights the causes of variation in groundwater vulnerability and the mechanisms that drive its spatial structure in the study area and can provide a reference for policy makers to support development of groundwater pollution control and protection plans. 参考文献 相似文献 引证文献

Removal of NO3– from groundwater by PP-g-AA-Am non-woven fabric using fixed-bed column reactors

This study investigated the effect of PP-g-AA-AM non-woven fabric on the removal of nitrate nitrogen from groundwater. The breakthrough time was 1.5–2.6, 2.5–5.5, and 6.2–12.2 h for a superficial velocity of 2.0, 1.0, and 0.5 cm/s, respectively, for the nitrate nitrogen concentration in groundwater to satisfy the safe standard for drinking of 10 mg/L (as per the Ministry of Environment in Korea's 2011 Management of Drinking Water Act); the slower the superficial velocity, the longer is the breakthrough time. The ion exchange amount was a maximum of 28.37 mg/g for a superficial velocity of 2.0 cm/s, and the ion exchange amount decreased with slower or faster superficial velocities. The ratio of adsorbent used shows a linear relationship with the column diameter to length ratio and an inverse one with the superficial velocity. It is a maximum of 79% for a superficial velocity of 0.5 cm/s and a column diameter to length ratio of 1:10. Multiple regression analysis with the superficial velocity, nitrate nitrogen concentration in groundwater, and column diameter to length ratio showed that the initial nitrate nitrogen concentration has the strongest influence on the ion exchange amount. A 10% NaCl regenerant solution of 20 times the reactor volume is required to accomplish >99% of ion exchange bed regeneration in a groundwater treatment facility when applied to a packed column filled with PP-g-AA-Am.

Evaluation of a Denitrification Wall to Reduce Surface Water Nitrogen Loads

Denitrification walls have significantly reduced nitrogen concentrations in groundwater for at least 15 yr. This has spurred interest in developing methods to efficiently increase capture volume to reduce N loads in larger watersheds. The objective of this study was to maximize treatment volume by locating a wall where a large groundwatershed was funneled toward seepage slope headwaters. Nitrogen concentration and load were measured before and after wall installation in paired treatment and control streams. Beginning 2 d after installation, nitrogen concentration in the treatment stream declined from 6.7 ± 1.2 to 3.9 ± 0.78 mg L and total N loading rate declined by 65% (391 kg yr) with no corresponding decline in the control watershed. This wall, which only comprised 10 to 11% of the edge of field area that contributed to the treatment watershed, treated approximately 60% of the stream discharge, which confirmed the targeted approach. The total load reduction measured in the stream 155 m downstream from the wall (340 kg yr) was higher than that found in another study that measured load reductions in groundwater wells immediately around the wall (228 kg yr). This indicated the possibility of an extended impact on denitrification from carbon exported beyond the wall. This extended impact was inauspiciously confirmed when oxygen levels at the stream headwaters temporarily declined for 50 d. This research indicates that targeting walls adjacent to streams can effectively reduce N loading in receiving waters, although with a potentially short-term impact on water quality.

Spatial variation in the trophic base of the trichopteran filter feeder Stenopsyche marmorata in an intermittent river in Japan

Carbon and nitrogen stable isotope analyses were used to determine how a trichopteran filter feeder Stenopsyche marmorata Navas (Stenopsychidae) reflects shifts in food sources (sus- pended particulate organic matter (SPOM), benthic particulate organic matter (BPOM), and periphy- ton) in response to channel drying in the alluvial soils of the Inukami River in Japan. The δ 13 C and δ 15 N values of consumers shifted to a pattern similar to that of BPOM in an intermittent river, which sug- gests that particulate organic matter at each station may play an important role as a food source. More- over, analysis of the upper reaches of the dry channel revealed that both consumers and food sources have enriched δ 13 C values due to physicochemical characteristics in the channel such as a high water temperatures and stagnant water. Conversely, the lower reaches showed more negative δ 13 C values, suggesting either a lack of carbon or a reduced supply of terrestrial dissolved carbon, both caused by channel drying, and higher δ 15 N values, suggesting a high dissolved inorganic nitrogen concentration in groundwater. Our study showed that a dry channel may influence the flow of energy between consumers and their food sources and the flow of nutrients from the upper to the lower reaches.

Seasonal changes in the concentrations of nitrogen and phosphorus in farmland drainage and groundwater of the Taihu Lake region of China

To reduce the harmful effects of irrigated agriculture on the environment, the evaluation of alternative irrigation water management practices is essential. The contents of total-phosphorus, nitrate nitrogen, and ammonium nitrogen in rural aquatic bodies typical of the Taihu Lake region (Yixing, Wangzhuang, and Xinzhuang) were determined during 2 years. The results showed that the concentrations of nitrogen and phosphorus during the rainy season were higher than in other months. The concentration of ammonium nitrogen in farmland drainage was higher than that of nitrate nitrogen. Ammonium nitrogen and nitrate nitrogen were the main pollution sources in rural groundwater. However, the pollution by ammonium nitrogen was worse than nitrate nitrogen. The annual average values of ammonium nitrogen in Yixing and Wangzhuang were 1.596 and 2.103 mg L(-1); with maximum values of 5.782 and 5.441 mg L(-1), respectively, exceeding the lower limit for type V water quality by a factor of 10. Concentrations of nitrate nitrogen in groundwater in Xinzhuang from May to September exceeded the limit value (10 mg L(-1)) for drinking water prescribed by the World Health Organization. Therefore, this groundwater was not suitable to drink. In Taihu Lake, the average concentration of phosphorus over 2 years was 0.492 mg L(-1) and pollution by phosphorus in Taihu Lake was worse than other farmland drainage because of the trend of total-phosphorus accumulation. In addition, the average concentrations of nitrate nitrogen and ammonium nitrogen in Taihu Lake were 2.152 and 2.885 mg L(-1), respectively over 2 years, indicating that the water in the Taihu Lake is constantly in danger of eutrophication. Because of the transformation of ammonium nitrogen to nitrate nitrogen, there was a connection between the concentrations of ammonium nitrogen in farmland drainage and nitrate nitrogen in groundwater. There was also a significant positive linear correlation between the concentrations of ammonium nitrogen in farmland drainage and in shallow groundwater.

Soil nitrogen transport and transformation of reclaimed water irrigated summer-maize under different groundwater levels

通过再生水灌溉田间试验，探讨了不同潜水埋深条件下（2 m、3 m、4 m），再生水灌溉对土壤中NO₃^--N、NH₄⁺-N及地下水中NO₃^--N的影响。试验结果表明：再生水灌溉后，土壤中NO₃^--N含量均显著增加；不同潜水埋深再生水灌溉对土壤中NH₄⁺-N含量影响不明显。灌水水平为900 m³·hm^-2,不同潜水埋深（2 m、3 m、4 m）地下水NO₃^--N浓度分别增加34.67%、24.94%、20.88%，灌水水平为1 200 m³·hm^-2不同潜水埋深地下水NO₃^--N浓度分别增加58.42%、38.98%、27.21%，潜水埋深越深地下水硝态氮浓度增加越小。表明潜水埋深越浅因淋溶和硝化作用产生的NO₃^--N造成浅层地下水污染的风险越大。

Predicting Nitrogen Concentration in Groundwater Beneath Unsewered Areas: Case Study of Liman Region in Antalya, Turkey

A simple approach to predict nitrogen concentration in groundwater beneath unsewered areas was developed and applied to the Liman region in Antalya, Turkey. The approach was also applied to predict the population density that was expected to increase groundwater nitrogen concentrations beyond 5.65 mg/L, which is the maximum value allowable by Turkish drinking water standards. The approach evaluated nitrogen and water budgets that included septic tanks, rainfall, and groundwater entering the upgradient boundary. The approach was shown to be sensitive to hydraulic conductivity, hydraulic gradient, denitrification rate in sewage, population density, and domestic water consumption. Predictions and field measurements of nitrogen concentration in groundwater showed good agreement in the Liman region. Moreover, the study illustrated the significant impact of groundwater entering the aquifer upgradient of the Liman region on nitrogen levels. The developed and tested approach is helpful and easy for planners and decision-makers to use in similar areas.

酸素同位体比による三浦半島南部地域河川水への生活排水の影響

The nitrogen concentration in groundwater and stream water exceeds environmental standards at some location in the southern region of the Miura Peninsula. In this region, the influence of fertilizer and domestic wastewater is indicated as a cause of the groundwater and stream water contamination.In this study, to clarify the influence of domestic wastewater, the contribution rate of tap water to river water was calculated using stable oxygen isotopes.In stream water and tap water in Miura City, a difference was seen in the stable isotope ratio of oxygen because of a difference in mean elevation of the watersheds. The domestic wastewater contribution rate calculated from stable oxygen isotopes in deep groundwater and tap water ranged from 6 to 30 %.

Complex hydrological controls on wet dune slacks: The importance of local variability

Dune slacks are a species-rich habitat controlled largely by water chemistry and fluctuations in groundwater. Changes in water chemistry and water table level were analysed in 8 piezometers and 15 ephemeral surface water locations at a large UK dune system over a 12-month period. Total nitrogen concentrations in groundwater varied from 0.27-8.21 mg N L(-1), where dissolved organic nitrogen was dominant at the low nitrogen locations and nitrate was dominant at the high nitrogen locations. Principal components analysis of the water chemistry suggests at least four chemically distinct groundwater signatures. Water levels showed strong temporal heterogeneity. Comparisons of water levels with antecedent rainfall identified a component of year-round groundwater feed and differing seasonal responses overlain by a complex series of lags. In summer, there were lags of four, six and seven months with an additional rapid peaky response to daily rainfall with a one-day lag. In winter, water levels were strongly influenced by exogenous groundwater supply, but again exhibited multiple lags. This study shows that local variations in water chemistry and in hydrological regime can be more complicated than previously thought, with clear implications for optimum management of these high priority habitats for conservation.