Contribution Of Spray Irrigation Of Wastewater To Groundwater Contamination In The Karst Of Southeastern Minnesota,USA

A vegetable- and meat-canning facility located in the karst of southeastern Minnesota disposes ≈2.85×10⁵ m³ yr^?1 of wastewater by spray irrigation of an 83.7-ha field located atop the local groundwater divide. Cannery effluent contains high levels of chloride and nitrogen (organic and ammonia), in excess of 7000 mg/l and 400 mg/l, respectively. Nitrate-nitrogen concentrations are generally < 5 mg/l. Agricultural, domestic, and municipal sources of chloride and nitrate are common in the region, and water supplies frequently exceed the drinking-water limit for nitrate-nitrogen of 10 mg/l. Fifty-two area wells and thirteen surface-water locations were sampled and analyzed for five ionic species, including: chloride (Cl), nitrate-nitrogen (NO₃-N), sulfate (SO₄), nitrite-nitrogen (NO₂-N), and phosphate (PO₄). Two distinct chloride plumes flowing outward from the groundwater divide were identified, and 65% of the wells sampled had nitrate-nitrogen concentrations in excess of 10 mg/l. The data were divided into two groups: one group of samples from wells located near the canning facility and another group from outside that area. A correlation coefficient of R²= 0.004 for Cl vs. NO₃-N in the vicinity of the irrigation fields indicates essentially no relationship between the source of Cl and NO₃. In areas of agricultural and domestic activities located away from the cannery, an R² of 0.54 suggests that Cl and NO₃ have common sources in these areas.     

Impacts of land use change and groundwater management on long-term nitrate-nitrogen and chloride trends in groundwater of Jeju Island,Korea

Impacts of land use changes and groundwater management actions on groundwater quality were evaluated at the island scale with spatiotemporal trends of NO₃-N and Cl concentrations in groundwater of Jeju Island, Korea. The temporal trends from 1993 to 2012 in the concentrations of NO₃-N and Cl from more than 3900 wells were estimated using the Mann–Kendall trend test and Sen’s slope analysis and compared with the land use change trend for the period 1995–2009. The results indicate that the upward trends in NO₃-N were associated with the expansion of agricultural lands, whereas Cl trends were considered to be affected by other factors in addition to the land use changes. In the mid-mountainous region, the deterioration in the groundwater quality by the both NO₃-N and Cl was expected due to the continuous expansion of agricultural lands. In the lowland area, the NO₃-N and Cl components showed different trends depending on the regions. In the eastern area, increasing trends in NO₃-N were observed due to the development of new agricultural areas, while the Cl concentration was observed to decrease as a result of the regulation on groundwater extraction to reduce seawater intrusion. Our study highlights that a comprehensive interpretation of trends in NO₃-N and Cl and land use changes for long-term periods can provide useful insights to prepare for suitable groundwater management plans in the whole island perspective.     

Effects of Torul dam on water quality in the stream Harşit,NE Turkey

This paper evaluates the effects of Torul dam on the stream Harşit water quality in terms of 13 physico-chemical parameters in the Gümüşhane Province, Eastern Black Sea Basin, Turkey. For this purpose, a study was fortnightly conducted during the four seasons between March 2009 and February 2010. In two monitoring stations selected in the upstream and downstream of the Torul dam, T, pH, DO and EC were determined in situ, and collected water samples were analyzed for TH, COD, NH₄ ⁺-N, NO₂ ⁻-N, NO₃ ⁻-N, TN, TKN, PO₄ ³⁻-P and MBAS. According to the Turkish Water Pollution Control Regulation (TWPCR), the stream Harşit was classified, and the obtained results were evaluated for the values proposed by Turkish Standard (TS) 266 and World Health Organization (WHO) guidelines. The results showed that the stream Harşit has high-quality water in terms of, T, pH, DO, COD, NH₄ ⁺-N and NO₃ ⁻-N, but slightly polluted water in terms of NO₂ ⁻-N, TKN and PO₄ ³⁻-P, and polluted for MBAS. It was concluded that Torul dam has a positive effect on the stream water quality in terms of decrease in the annual average concentration values. The percent decreases for TH, COD, NH₄ ⁺-N, NO₂ ⁻-N, NO₃ ⁻-N, TN, TKN, PO₄ ³⁻-P and MBAS were 17.1, 20.3, 56.2, 62.6, 11.7, 11.9, 11.4, 17.8 and 71.4, respectively. The reason for these decreases is probably due to the Torul dam reservoir where the water has a hydraulic residence time and the exposure to chemicals by aquatic organisms or populations that ingest the water. Also, statistical analysis shows that there are significant correlations among the studied parameters.     

Identification of river water pollution characteristics based on projection pursuit and factor analysis

Human activities contribute different pollutants to receiving waters, often with significant variations in time and space. Therefore, integrating multiple parameters of water quality and their spatiotemporal variations is necessary to identify the pollution characteristics. Based on the water quality monitoring data with 12 parameters for 2 years at 22 sampling sites in the Cao-E River system, eastern China, the projection pursuit method was used to project all parameters and their temporal variations into a one-dimensional vector through two projections. Accordingly, we could easily assess the comprehensive water quality in different sampling sites and then classify their water pollution features. Factor analysis was then used to identify the pollution characteristics and potential sources. Results showed that all sampling sites for the river system could be classified into four groups: headwater sites (HS), agricultural nonpoint sources pollution sites (ANPS), point sources pollution sites (PSPS), and mixed sources pollution sites. Water quality in HS was good, containing only a few nutrients from the woodland runoff and soil erosion. For ANPS, the main pollutants were dissolved phosphorus, total P, and nitrate nitrogen (NO₃ ^?-N), mainly from farming land. For PSPS, ammonium nitrogen (NH₄ ⁺-N) and organic pollutants originated from industrial and municipal sewage. In HS and ANPS, NO₃ ^?-N was the main form of nitrogen, and a high ratio of NO₃ ^?-N/NH₄ ⁺-N was a remarkable characteristic, whereas NH₄ ⁺-N was the main form of nitrogen in PSPS. Except in HS, water quality in the other groups could not meet the local water quality control standard. Finally, suggestions were proposed for water pollution control for the different groups.     

Water and sediment quality assessment in the mid-Black Sea coast of Turkey using multivariate statistical techniques

The aim of this study was to investigate the water and sediment quality in the mid-Black Sea coast of Turkey. The samples were collected from six stations during 2007. Investigated parameters were total carbon (TC), total inorganic carbon (TIC), total organic carbon (TOC), ammonium-nitrogen (NH₄-N), nitrate-nitrogen (NO₃-N), nitrite-nitrogen (NO₂-N), total phosphorus (TP), sulphate, total hardness, methylene blue active substances (MBAS), phenol, adsorbable organic halogens (AOX), dissolved oxygen (DO), pH and electrical conductivity (EC) in water samples and TC, TIC, TOC, TP, pH, electrical conductivity (EC), redox potential (Eh) and water content (WC) in sediment samples. Different multivariate statistical techniques were used to evaluate variations in surface water and sediment quality. Principal component analysis helped in identifying the factors or sources responsible for water and sediment quality variations. Five factors were found responsible for 87.63% of the total variance in the surface waters. In sediments, three factors explained 84.73% of the observed total variance. Cluster analysis classified the monitoring sites into two groups based on similarities of water and sediment quality characteristics.     

N-15 Identification of nonpoint sources of nitrate contamination beneath cropland in the Nebraska Panhandle: two case studies

Monitoring of municipal wells near the town of Sidney and domestic wells near Oshkosh in Nebraska's Panhandle indicated the nitrate-nitrogen (NO₃-N) levels were increasing and exceeded the maximum contaminant level of 10 mg/l NO₃-N in several wells. Both areas are located in narrow stream valleys that are characterized by well-drained soils, highly permeable intermediate vadose zones, shallow depths to groundwater, and intensive irrigated corn production. Both areas also have a large confined cattle feeding operation near the suspected contamination and potentially could be contaminated by more than on nitrate source.At Sidney NO₃-N concentrations were measured in 13 monitoring wells installed along an east-west transect im the direction of groundwater flow, 26 private wells, and eight municipal wells. Nitrate-nitrogen concentrations were homogeneous beneath a 5 km by 1.2 km area and averaged 11.3 ± 1.8 mg/l NO₃-N. The δ¹⁵N-NO₃ values in the monitoring and municipal wells had a narrow range from +5.8 to +8.8%. The isotopic ratios are indicative of a mixed source of nitrate contamination, which originates from agronomic (commercial fertilizer N and mineralized N) N and animal waste. Both commercial fertilizer N and animal wastes are applied to the irrigated fields.Nitrate-nitrogen concentrations in two multilevel samplers installed downgradient from irrigated cornfields at the Oshkosh site averaged 20.1 ± 13.3 mg/l NO₃-N and 37.3 ± 8.2 mg/l NO₃-N. The δ¹⁵N-NO₃ values spanned a narrow range from +3.5 to +5.9% and averaged +4.0 ± 0.5% and +5.0 ± 0.6%. These low values are indicative of leachates from commercial fertilizer applied to the irrigated fields.     

Potential nitrogen fixation changes under different land uses as influenced by seasons and biochar amendments

Soil nutrient dynamics, potential biological nitrogen fixation (BNF) changes, and their relations were studied using four land use types. Further, we investigated BNF changes in the presence of biochar in soils. Soil samples were collected from arable, vineyard, grassland, and forest soils during four seasons, and analyzed for abiotic contents of total nitrogen, NH₄⁺-N, NO₃^?-N, ammonium lactate (AL)-soluble K₂O, P₂O₅, and soil organic carbon (SOC) concentrations. Potential N₂ fixation was measured as ethylene (C₂H₄) production from acetylene (C₂H₂) reduction (ARA). The study focused on the changes in ARA when different types of biochars (T600, T650, and T700) were applied to soil samples in different amounts (0, 0.5, 2.5, and 5.0% wt wt^?1) under laboratory conditions. We found strong correlations between soil chemical parameters and ARA values, especially in the case of soil pH, total N, SOC, and P₂O₅ contents. In the case of arable soil, the ARA measurements were up to 227 times higher compared to grassland and forest samples. Biochar application affected N₂-fixing microbial responses among land use types, most notably decreases in arable lands and forest soils. We found that a high amount of biochar added to the soils can greatly suppress N₂-fixing activities. Our results highlight the strong relationship between soil nutrient changes and the intensity of anthropogenic influence.     

Effects of sediment texture on in-stream nitrogen uptake

A comparative experiment was conducted in two cross sections with sandy and sandy loam sediment textures along an agricultural drainage stream in eastern China to address the effects of sediment texture on in-stream nitrogen uptake efficiency. Using dimerous chambers for in situ incubations, NO₃-N and NH₄-N uptake metrics (i.e., areal uptake rate and uptake velocity) and associated hydrochemical variables in the enclosed sediment–water column system were measured for 8 days and two nights across April–July in 2011 and March–June in 2012. For the investigated sites, in-stream uptake accounted for 2–45 and 9–36 % of the initial NH₄-N and NO₃-N within the enclosed water column, respectively. Although similar daytime, diel and day-to-day (daytime) variation patterns of NO₃-N or NH₄-N uptake metrics were observed for the two sites, the sandy loam sediments had average net NO₃-N and NH₄-N uptake efficiency ~50 % higher and ~40 % lower than for the sandy sediments, respectively. As NO₃-N was the dominant nitrogen form in the studied water columns (typical of agricultural drainage rivers), the sandy loam sediment site had an average of about 47 % higher net uptake efficiency for dissolved inorganic nitrogen (i.e., NO₃-N + NH₄-N). This study demonstrates that sediment texture has a considerable effect on spatial variation of nitrogen uptake along the river system. Changing sediment texture due to anthropogenic modifications on catchment land use and stream channels has the potential to change stream nitrogen cycling as well as altering nitrogen inputs and forms to downstream aquatic ecosystems.     

Reciprocal influence of Kürtün Dam and wastewaters from the settlements on water quality in the stream Harşit,NE Turkey

This paper aims to reveal the reciprocal influence of Kürtün Dam and wastewaters from the settlements on the water quality in the stream Har?it, NE Turkey. Several key water-quality indicators were measured: water temperature (T), pH, dissolved oxygen (DO), electrical conductivity, water hardness, chemical oxygen demand (COD), ammonium nitrogen (NH₄ ⁺–N), nitrite nitrogen (NO₂ ^?–N), nitrate nitrogen (NO₃ ^?–N), total Kjeldahl nitrogen (TKN), total nitrogen (TN), orthophosphate phosphorus (PO₄ ^3?–P), and methylene blue active substances (MBAS). The monitoring and sampling studies were conducted every 15 days from March 2009 to February 2010 at two stations selected in the upstream and downstream of the Kürtün Dam. It was concluded that the Kürtün Dam Lake had a high-quality water in terms of T, pH, DO, COD, NH₄ ⁺–N, NO₂ ^?–N and NO₃ ^?–N values, but slightly polluted water with respect to TKN, PO₄ ^3?–P, and MBAS according to the Turkish Water Pollution Control Regulation. The dam improved the stream water quality by increasing the DO concentration, and decreasing the NO₂ ^?–N and PO₄ ^3?–P concentrations thanks to its hydraulic residence time despite the wastewater discharge by the nearby settlements. However, the wastewater discharge deteriorated the stream water quality increasing the COD, NH₄ ⁺–N, NO₃ ^––N, and TN concentrations.     

Microbial nitrogen removal in a developing suburban estuary along the South Carolina coast

The conversion of undisturbed coastal regions to commercial and suburban developments may pose a threat to surface and groundwater quality by introducing nitrate-nitrogen (NO₃ ^?-N) from runoff of land-applied wastewater and fertilizers. Microbial denitrification is an important NO₃ ^?-N removal mechanism in coastal sediments. The objective of this study was to compare denitrification and nitrate conversion rates in coastal sediments from a golf course, suburban site, undeveloped marsh, and nonmarsh area near rapidly developing Hilton Head Island, South Carolina. Nitrous oxide was measured using gas chromatography and nitrate and ammonium concentrations were measured using a flow injection autoanalyzer in microcosms spiked, with 50 μg NO₃ ^?-N gdw^?1. The two marsh sites had the greatest ammonium production, which was correlated with fine sediment particle size and higher background sediment nitrate and surface water sulfate concentrations. The golf course swale had greatest denitrification rates, which were correlated with higher total carbon and organic nitrogen in sediments. Nitrate was consumed in golf course sediments to a greater extent than in the undeveloped marsh and upland freshwater sites, suggesting that the undeveloped sites and receiving estuaries may be more susceptible to nitrate contamination than the golf course swale and marsh under nonstorm conditions. Construction of swales and vegetated buffers using sediments with high organic carbon content as best management practices may aid in removing nitrate and other contaminants from runoff prior to its transport to the receiving marsh and estuary.     

The contribution of rain-on-snow events to annual NO3-N export from a forested catchment in south-central Ontario,Canada

The contribution of rain-on-snow (ROS) events to NO₃-N levels in stream water has received relatively little research attention. However, individual ROS events during January and February contributed up to 40% of annual NO₃-N export from a forested catchment in south-central Ontario between 1980 and 2000, but comprised less than 10% of annual precipitation. Nitrate-N concentrations in stream water increased rapidly following ROS events, and were similar to the concentrations in incident rainfall and the accumulated snow pack, likely due to limited contact of runoff with mineral soil under snow cover and low winter biological activity. Increased NO₃-N associated with ROS events resulted in substantial depressions in stream pH and alkalinity, which may delay the biological recovery from acidification. The contribution of ROS events to annual or winter NO₃-N export has been generally greater in recent years, although there is a considerable year-to-year variation. As a result, ROS events contribute to inter-annual variability in stream NO₃-N concentrations and will have a strong effect on apparent temporal trends. The contribution of ROS events to annual NO₃-N export should be considered when assessing surface water recovery from acidification and the N-status of forests, particularly if climate change projections for winter warming result in a greater proportion of winter precipitation occurring as rain.     

The influence of topography and land use on water quality of Xiangxi River in Three Gorges Reservoir region

A self-organizing map (SOM) was used to cluster the water quality data of Xiangxi River in the Three Gorges Reservoir region. The results showed that 81 sampling sites could be divided into several groups representing different land use types. The forest dominated region had low concentrations of most nutrient variables except COD, whereas the agricultural region had high concentrations of NO₃N, TN, Alkalinity, and Hardness. The sites downstream of an urban area were high in NH₃N, NO₂N, PO₄P and TP. Redundancy analysis was used to identify the individual effects of topography and land use on river water quality. The results revealed that the watershed factors accounted for 61.7% variations of water quality in the Xiangxi River. Specifically, topographical characteristics explained 26.0% variations of water quality, land use explained 10.2%, and topography and land use together explained 25.5%. More than 50% of the variation in most water quality variables was explained by watershed characteristics. However, water quality variables which are strongly influenced by urban and industrial point source pollution (NH₃N, NO₂N, PO₄P and TP) were not as well correlated with watershed characteristics.     

Effects of land use on spatial patterns of soil properties in a rocky mountain area of Northern China

In the rocky mountain area of North China, soil fertility has decreased with severe soil and water losses under various land uses. Land use has been proven to affect soil fertility spatial distribution patterns at larger scales. However, less information is available about these effects in field scale plots. Soil samples were collected at 2-m intervals by grid sampling from an area (18?×?18 m) within three land use types (poplar woodland, rotation cropland with peanut and sweet potato, and peach orchard). Soil properties including soil particle composition, soil organic matter, total nitrogen (TN), nitrate nitrogen (NO₃ ^?-N), total phosphorus (TP), and available phosphorus (AP) were measured for each sample. The spatial variability and spatial pattern of the soil properties were assessed for the three contrasting land use types. NH₄ ⁺-N, NO₃ ^?-N, and AP in the peach orchard and NO₃ ^?-N in the poplar woodland exhibited strong variation (coefficient of variance >100 %). Other properties showed moderate variations. With annual plowing and fertilization, soil properties in the rotation cropland had less variability and greater spatial autocorrelated ranges. The spatial dependences of sand content, TN, NO₃ ^?-N, and SWC in both the peach orchard and the rotation cropland were weaker than those in the poplar woodland, but the spatial dependences of TP and AP in the peach orchard were stronger than those in either the rotation cropland or the poplar woodland. Human activities such as plowing, fertilization, and harvesting had obvious effects on the spatial variability and spatial pattern of soil properties.     

Identification of water quality and zooplankton characteristics in Daya Bay, China, from 2001 to 2004

Data collected from 12 marine monitoring stations in Daya Bay from 2001 to 2004 reveal a substantial change in ecological environment in this region. Cluster analysis based on water quality and zooplankton results divided stations into three clusters: Cluster I consisted of stations S1, S2 and S6 in the south part of Daya Bay; Cluster II consisted of stations S3, S8 and S11 in the cage culture areas in the southwest part, the northwest part near Aotou harbor and the northeast part near the Fanhe harbor of Daya Bay; Cluster III consisted of stations S4, S5, S7, S9, S10 and S12 that were in southwest, the middle and northeast parts of Daya Bay. Bivariate correlations between zooplankton biomass and the major physical and nutrient variables were evaluated for all stations. The zooplankton biomass in all stations correlated positively with salinity, pH, secchi, NO₃-N, NH₄-N, TIN/PO₄-P and SiO₃-Si/PO₄-P, and negatively correlated with temperature, DO, COD, NO₂-N and TIN, PO₄-P, SiO₃-Si and BOD₅. Factors analysis shows high positive loading salinity, secchi and NH₄-N of three clusters, which indicates that all stations of the three clusters were primarily grouped according to their respective nutrient conditions. The results of multivariate statistical analysis revealed that temperature, DO, TIN and BOD₅ could also play an important role in determining the biomass of the zooplankton in Daya Bay, especially in the stations near the nuclear power plants and in the cage culture areas.     

Effects of historical and projected land use/cover change on runoff and sediment yield in the Netravati river basin,Western Ghats,India

In this study, the effects of changes in historical and projected land use land cover (LULC) on monthly streamflow and sediment yield for the Netravati river basin in the Western Ghats of India are explored using land use maps from six time periods (1972, 1979, 1991, 2000, 2012, and 2030) and the soil and water assessment tool (SWAT). The LULC for 2030 is projected using the land change modeller with the assumption of normal growth. The sensitivity analysis, model calibration, and validation indicated that the SWAT model could reasonably simulate streamflow and sediment yield in the river basin. The results showed that the spatial extent of the LULC classes of urban (1.80–9.96%), agriculture (31.38–55.75%), and water bodies (1.48–2.66%) increased, whereas that of forest (53.04–27.03%), grassland (11.17–4.41%), and bare land (1.09–0.16%) decreased from 1972 to 2030. The streamflow increased steadily (7.88%) with changes in LULC, whereas the average annual sediment yield decreased (0.028%) between 1972 and 1991 and increased later (0.029%) until 2012. However, it may increase by 0.43% from 2012 to 2030. The results indicate that LULC changes in urbanization and agricultural intensification have contributed to the increase in runoff, amounting to 428.65 and 58.67 mm, respectively, and sediment yield, amounting to 348 and 43 ton/km², respectively, in the catchment area from 1972 to 2030. The proposed methodology can be applied to other river basins for which temporal digital LULC maps are available for better water resource management plans.     

Sizing first flush pollutant loading of stormwater runoff in tropical urban catchments

This study aimed at investigating the first flush phenomenon from residential, commercial and industrial catchments. Stormwater was grab sampled and the flow rate was measured during 52 storm events. The dimensionless cumulative pollutant mass and runoff volume were used to determine the runoff volume needed to transport 50 and 80 % of total pollutant mass. Almost all the constituents did not satisfy this first flush definition except for total suspended solids (TSS) in the commercial catchment. The averages first runoff volume required to remove 50 and 80 % of the total pollutant mass were 37 and 67, 35 and 65, and 36 and 64 % for the residential, commercial and industrial catchments, respectively. It seemed that less runoff is required to transport the same amount of pollutant loadings in tropical urban catchments than in temperate regions. BOD, COD, NH₃-N, SRP and TP consistently showed strong first flush effects in all catchments. The first flush strengths of TSS, BOD, COD, NH₃-N and TP in the commercial catchment were strongly correlated with total rainfall, rainfall duration, max 5 min intensity, runoff volume and peak flow, but not with antecedent dry days. Management of the first 10 mm runoff depth would be able to capture about half of the total pollutant mass in stormwater runoff that would otherwise goes to drains.     

Relations of hydrogeologic factors, groundwater reduction-oxidation conditions, and temporal and spatial distributions of nitrate, Central-Eastside San Joaquin Valley, California, USA

In a 2,700-km² area in the eastern San Joaquin Valley, California (USA), data from multiple sources were used to determine interrelations among hydrogeologic factors, reduction-oxidation (redox) conditions, and temporal and spatial distributions of nitrate (NO₃), a widely detected groundwater contaminant. Groundwater is predominantly modern, or mixtures of modern water, with detectable NO₃ and oxic redox conditions, but some zones have anoxic or mixed redox conditions. Anoxic conditions were associated with long residence times that occurred near the valley trough and in areas of historical groundwater discharge with shallow depth to water. Anoxic conditions also were associated with interactions of shallow, modern groundwater with soils. NO₃ concentrations were significantly lower in anoxic than oxic or mixed redox groundwater, primarily because residence times of anoxic waters exceed the duration of increased pumping and fertilizer use associated with modern agriculture. Effects of redox reactions on NO₃ concentrations were relatively minor. Dissolved N₂ gas data indicated that denitrification has eliminated >5 mg/L NO₃–N in about 10% of 39 wells. Increasing NO₃ concentrations over time were slightly less prevalent in anoxic than oxic or mixed redox groundwater. Spatial and temporal trends of NO₃ are primarily controlled by water and NO₃ fluxes of modern land use.     

Distribution of nitrate in groundwater affected by the presence of an aquitard at an agricultural area in Chiba, Japan

Geological and geographical parameters including land use, stratigraphic structure, groundwater quality, and N- and O-isotopic compositions of nitrate in groundwater were investigated to elucidate the mechanism of groundwater pollution by NO₃ ^? in the agricultural area of Katori, Chiba, Japan. An aquitard distributed in the western part of the study area has produced two unconfined aquifers. The average concentrations of NO₃ ^? and dissolved oxygen (DO) were high in the aquifer above the aquitard (7.5 and 7.6 mg/L, respectively) and in the aquifer of the eastern part of the study area that was not influenced by the aquitard (11.9 and 7.8 mg/L, respectively); however, the levels in the aquifer under the aquitard were relatively low (2.2 and 3.7 mg/L, respectively). The δ¹⁵N and δ¹⁸O values of NO₃ ^? generally increased exponentially in the groundwater that flowed into the aquifer under the aquitard as the concentration of NO₃ ^? decreased, although this decrease in NO₃ ^? also occasionally occurred without isotopic changes. These results indicated that the aquitard prevented the penetration of NO₃ ^?, DO, and gaseous O₂. Under the aquitard, denitrification and dilution with unpolluted water that entered from natural forested areas reduced the NO₃ ^? concentrations in the groundwater. The major sources of NO₃ ^? in groundwater in the study area were estimated to be NH₄-chemical fertilizer, livestock waste, and manure.     

Surface water chemistry and nitrate pollution in Shimabara,Nagasaki, Japan

Groundwater is a finite resource that is threatened by pollution all over the world. Shimabara City, Nagasaki, Japan, uses groundwater for its main water supply. During recent years, the city has experienced severe nitrate pollution in its groundwater. For better understanding of origin and impact of the pollution, chemical effects and surface–groundwater interactions need to be examined. For this purpose, we developed a methodology that builds on joint geochemical analyses and advanced statistical treatment. Water samples were collected at 42 sampling points in Shimabara including a part of Unzen City. Spatial distribution of water chemistry constituents was assessed by describing Stiff and Piper diagrams using major ions concentrations. The nitrate (NO₃?+?NO₂–N) concentration in 45% of water samples exceeded permissible Japanese drinking level of 10 mg L^??1. Most of the samples showed Ca–HCO₃ or Ca–(NO₃?+?SO₄) water types. Some samples were classified into characteristic water types such as Na–Cl, (Na?+?K)–HCO₃, (Na?+?K)–(SO₄?+?NO₃), and Ca–Cl. Thus, results indicated salt water intrusion from the sea and anthropogenic pollution. At the upstream of Nishi River, although water chemistry was characterized as Ca–HCO₃, ion concentrations were higher than those of other rivers. This is probably an effect of disinfection in livestock farming using slaked lime. Positive correlation between NO₃^? and SO₄^2?, Mg²⁺, Ca²⁺, Na⁺, K⁺, and Cl^? (r?=?0.32–0.64) is evidence that nitrate pollution sources are chemical fertilizers and livestock waste. Principal component analysis showed that chemistry of water samples can be explained by three main components (PCs). PC1 depicts general ion concentration. PC2 and PC3 share influence from chemical fertilizer and livestock waste. Cluster analyses grouped water samples into four main clusters. One of these is the general river chemistry mainly affected by PC1. The others reflect anthropogenic activities and are identified by the combination of the three PCs.     

Assessment of LULC and climate change on the hydrology of Ashti Catchment,India using VIC model

The assessment of land use land cover (LULC) and climate change over the hydrology of a catchment has become inevitable and is an essential aspect to understand the water resources-related problems within the catchment. For large catchments, mesoscale models such as variable infiltration capacity (VIC) model are required for appropriate hydrological assessment. In this study, Ashti Catchment (sub-catchment of Godavari Basin in India) is considered as a case study to evaluate the impacts of LULC changes and rainfall trends on the hydrological variables using VIC model. The land cover data and rainfall trends for 40 years (1971–2010) were used as driving input parameters to simulate the hydrological changes over the Ashti Catchment and the results are compared with observed runoff. The good agreement between observed and simulated streamflows emphasises that the VIC model is able to evaluate the hydrological changes within the major catchment, satisfactorily. Further, the study shows that evapotranspiration is predominantly governed by the vegetation classes. Evapotranspiration is higher for the forest cover as compared to the evapotranspiration for shrubland/grassland, as the trees with deeper roots draws the soil moisture from the deeper soil layers. The results show that the spatial extent of change in rainfall trends is small as compared to the total catchment. The hydrological response of the catchment shows that small changes in monsoon rainfall predominantly contribute to runoff, which results in higher changes in runoff as the potential evapotranspiration within the catchments is achieved. The study also emphasises that the hydrological implications of climate change are not very significant on the Ashti Catchment, during the last 40 years (1971–2010).