DETECTION OF THE NITRATE POLLUTION SOURCES IN SHALLOW AQUIFER , USING INT E GRATION OF RS & GIS WITH STABLE ISOTOPES TECHNOLOGIES

Geographical information system (GIS) and remote sensing technique is a tool which is used for acquiring data from space, storing, analyzing and displaying spatial data, also can use for investigating source of environmental pollution which is affect health. Sudan landsat mosaic image which acquired in 2013 was used in this study to develop land use and land cover maps for tow selected study area, Khartoum urban area, and Bara locality in North kordofan state western Sudan. The main objective to assess the source of Nitrate pollution in shallow aquifer. ERDAS software was used to create land cover-land use maps for the study areas. For Khartoum town we used land sat mosaic image which acquire in 2013, and used supervised classification which more closely controlled than unsupervised. In this process, we select pixel that represent patterns you recognized or can identify with help from knowledge of the data, the classes desired, and the algorithm to be used is required. In this paper we integrated the (GIS&RS), and stable isotopes methods for fingerprinting Nitrate sources in shallow boreholes. The global positioning system (GPS), used in the field to identify the shallow boreholes location in a three dimensional coordinate (Latitude, longitude, and altitude), Water samples were collected from 19 shallow boreholes in the study areas according to the standard sampling method send to laboratory to measure stable nitrogen (δ15Nnitrate), and Nitrate-oxygen (δ18Onitrate) isotopes. Analysis were conducted by using isotope ratio mass spectrometry (IRMS). We can conclude that, special distribution and integration of GIs & RS help to identify the source of nitrate pollution.


INTRODUCTION
Contamination of shallow ground water by nitrate (NO3-) from various sources continues to be a problem through much of the Bara area, most nitrate contamination sources are easily defined, particularly if there is a single known source such as a cattle feed lot and small farms, but in some areasparticularly rural locations that have been urbanized, distinguishing between human (anthropogenic) and natural (geogenic) sources is somewhat more complicated.The main concern with high levels of nitrate in groundwater is the increased incidence of methemoglobinemia, known as blue-baby disease; it causes the child to develop a bluish or grayish tint around the extremities.If left untreated the baby will not receive enough oxygen through the blood and could die.This problem arises primarily in rural areas.How can one distinguish between anthropogenic and geogenic nitrate?Conventional nitrate analysis only gives quantitative data and does not discriminate between sources.However, if one examines the stable isotopes of nitrate, unique fingerprints for different sources can be obtained.Where nitrate levels are not well monitored.
The nitrate exported from surface watersheds is typically a mixture of nitrate from two sources: (1) Atmospheric deposition (atmospheric nitrate) (2) Nitrification in soils (microbial nitrate) Stable nitrogen and oxygen isotopes are useful in indicating sources when nitrate is present in surface or groundwater.Delta nitrate-nitrogen (δ15Nnitrate) and nitrate-oxygen (δ18Onitrate) isotope ratios in water can be used to identify nitrate sources and its fate in shallow groundwater.Nitrogen has two stable isotopes: 14N, with a natural abundance of 99.63% and 15N, with a natural abundance of 0.37%.The wide difference in the isotopic abundance allows for the determination of distinctive isotopic signatures to define specific natural and anthropogenic sources.
In analyzed samples, the ratio of 15N/14N is compared with a standard (atmospheric nitrogen) to provide δ15N * .The abundance of 15N in the atmosphere remains relatively constant because of the inert character of atmospheric nitrogen resulting in a δ15N of zero.

Objectives
To assess the source of Nitrate pollution in shallow aquifer in urban and rural area.
Using remote sensing and GIS For Acquire data and displaying spatial data for investigating environmental pollution hazard.

Site description and methods
Sudan land cover image and landsat mosaic image which acquired in 2013 with resolution 30 meter, and projected: WGS_1984_UTM_Zone_36N.This image was classified to create land use and land cover maps for tow selected study area, Khartoum state with population more than 5 million, and Bara locality as rural area with small population their livelihood mainly from small farms (vegetables and fruits), and livestock .They used shallow boreholes for irrigation and drinking water supply.

Special analysis using interpolation method
Inverse distance weighting (IDW):-In interpolation with IDW method, a weight is attributed to the point to be measured.The amount of this weight is dependent on the distance of the point to another unknown point the distance between the points count, so the points of equal distance have equal weights.The weight factor is calculated with the use of the following formula:   The classification process used by sorting pixels into a finite number of individual classes, if a pixel satisfies a certain set of (1) criteria, then the pixel is assigned to the class that corresponds to those criteria.
ERDAS software has two ways to classify pixels into different categories, supervised and unsupervised.
Study area land use created using supervised classification which more closely controlled than unsupervised .In this process, we select pixel that represent patterns you recognize or can identify with help from knowledge of the data, the classes desired, and the algorithm to be used is required.
By identifying patterns in the imagery, we can train the computer system to identify pixels with similar as they are assigned to a class value.If the classification is accurate, then each resulting class corresponds to a pattern that we originally identified.Result of _nitrate isotopes analysis for sample collected from shallow aquifer in Khartoum indicated the source of nitrate contamination was from anthropogenic source and mainly from animal or human waste and organic nitrogen in soil.If we compare the result with special analysis result and land cover/ land use map for Khartoum area, the population increase which lead to increase in human waste water with low facilities for treatment .alsonitrate contamination increase in shallow aquifer during rainfall season by percolation into the soil to ground water .
For Bara area were samples collected from 11 shallow Boreholes, the result of analysis indicated that the nitrogen sources mainly from organic nitrogen in soil and commercial fertilizer, which agree with special analysis and land cover map the 90% land use area farms planted with vegetables and fruit, and they used intensive fertilizers see appendix (1) (Table 3).animal and human waste, while in Bara basin shallow boreholes, the nitrate contamination source mainly organic nitrogen in soil, like fertilizers in agriculture farm, and few contaminated by livestock area and urban area mainly human waste.Most nitrate contamination sources are easily defined, particularly there is single known source such as a cattle feed lot, but in some areas particularly rural locations that have been urbanized, distinguishing between human (anthropogenic) and natural (geogenic) sources is somewhat more complicated Analysis of nitrogen-oxygen isotopes of dissolved nitrate provides an excellent technique for Fingerprinting nitrate sources, however, as in any forensic investigation it is important to have more than one line of evidence and the technique combined with a complete understanding of the local environment or land use history and hydrogeology including groundwater geochemistry.

Fig 1 .
Fig 1. Diagrammatic representation of the major Components of the Nitrogen cycle the weight of the point Di -Distance between point I and unknown point ɑ -The power ten of weight.

Fig 2 .
Fig 2. Sudan hydro Geological map show, Khartoum and N. Kordofan state

Table 2 .
Vienna Standard Mean Ocean Water (VSMOW) standards for δ15N and δ18O

Table ( 3
) Stable Isotopes Result and Source of pollution