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Groundwater pollution by Nitrate transport through soil column at Hada Asham region, Saudi Arabia Khaled S. Balkhair Water Resources Research King Abdulaziz.

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Presentation on theme: "Groundwater pollution by Nitrate transport through soil column at Hada Asham region, Saudi Arabia Khaled S. Balkhair Water Resources Research King Abdulaziz."— Presentation transcript:

1 Groundwater pollution by Nitrate transport through soil column at Hada Asham region, Saudi Arabia Khaled S. Balkhair Water Resources Research King Abdulaziz University Saudi Arabia

2 Contents 1 Mathematical models Objective of the study Study area Application Results & Conclusions

3 Objective of the study Experimentally monitor and numerically model the transport of nitrate in a real soil column of Hada Asham (western region of Saudi Arabia) to predict its leach to the groundwater table

4 4

5 Algae Bloom Tiny water plants capture the sun’s energy and support the food web. Dissolved nitrogen can lead to sudden overabundance, which blocks sunlight to water, kills fish by using the water’s oxygen, produces scum or odor, and in some cases, produces toxins. Powdered formula mixed with tap water could contain nitrate. Blue Baby Syndrome An illness that occurs when a child drinks water containing a large amount of nitrates. The body’s digestive system converts these to nitrites, changing oxyhemoglobin to metheglobin, which cannot carry oxygen. Mucous membranes turn blue, impairing functions. methemoglobinemia Nitrogen in our environment

6 Young Animal Illness High levels of nitrate in water lead to increased livestock and wildlife stillbirth rates, low birth weight, slow weight gain, and reduced vitality. Agricultural Fertilizer Living organisms use nitrogen to build proteins, enzymes, DNA, RNA, vitamins, and hormones. Most animals derive their nitrogen from plants, which convert simple compounds to more complex ones. Adding simple nitrogen compounds to soil increases plant growth. Nitrogen in our environment

7 Sterile Food Packing Cream Whipper Chargers Oxygen allows bacterial growth and chemical breakdown of foods. Food is often vacuum-packed to remove oxygen or packed with nitrogen. N 2 O is soluble in fats and used as a propellant for canned whipped cream. Sewers and Septic Tanks Human urine contains a large amount of ammonia. Soil bacteria oxidize ammonia to form nitrates. Leaking septic tanks or sewer systems release the wastes into the soil, groundwater, and surface water systems. Nitrogen in our environment

8 Dentistry/Medicine Nitrous oxide (N 2 O), also known as “laughing gas,” is a mild anesthetic used in dentistry. Nitric oxide (NO) is a short-lived gas that acts as a signaling molecule in the body for blood pressure. “Nitro” drugs like nitroglycerin lower blood pressure by increasing NO. Meat Preservative Sodium nitrite is a salt that prevents bacterial growth and botulism. When added to meat, the nitrite turns to nitric oxide and combines with myoglobin, the red pigment in meat, turning it the pink color of ham and hotdogs. Nitrogen in our environment

9 Lightning Strikes The high temperatures and pressures that surround electric storms form nitric oxide (NO) and nitrogen dioxide (NO 2 ), which reacts with rain to form nitric acid (HNO 3 ). Nitrates formed by the interaction of nitric acid and soil provide nitrates for plant growth. Soil Bacteria Microbes in the ground conduct denitrification, a process that converts nitrates back to nitrogen gas. This process also produces nitrous oxide, which is a greenhouse gas contributing to global warming. Nitrogen in our environment

10 The pulp and paper industry processes wood with heat, pressure and caustic solutions. Possible polluting byproducts include methanol, NOx and carbon dioxide emissions, and ammonia and nitrates releases in sludge or wastewater. Paper Industry Farm Animal Waste Barnyards, dairies, and feedlots produce a lot of animal waste. Bacteria convert the ammonia in this waste to nitrates that enter the ground or surface water systems. Bacteria from animal waste is also a contaminant. Nitrogen in our environment

11 Is N Toxic? Spinach is one of the largest accumulators of nitrate Nitrite and N-nitrous compounds found in numerous animal studies to be carcinogenic (U.S. Dept. of Health and Human Services 1998). nitrate exposure ► methemoglobinemia (blue baby syndrome) in infants Associations between nitrate in drinking water and chronic health problems: hyperthyroidism (goiter) linked to exposure to nitrate in drinking water (Seffner 1995; VanMaanen et al. 1994); An increased risk for central nervous system malformations in newborns whose mothers had consumed private well water equal to or greater than 26 ppm NO 3 -N (Arbuckle et al. 1988);

12 Genotoxic effects at the chromosomal level reported in persons consuming water with very high nitrate levels (Van Maanen et al. 1996; Tsezou et al. 1996) Elevated mortality rates of stomach cancer associated with high levels of nitrate in water supplies (Morales-Suarez et al. 1995); A positive correlation between mortality rates of bladder cancer and nitrate levels in drinking water (Morales-Suarez et al. 1993);

13 Groundwater Pollution by Nitrate

14 Mathematical model Water flow equation PDE – 1D – WF – Richard’s Eq. Or θ =θ(h) is the volumetric water content, h = h(z, t) is the matric potential, z is the position coordinate in the direction of flow; K(h) is the hydraulic conductivity of the soil at matric potential C(h) is the specific water capacity.

15 PDE solution Initial condition Specified head Uniform or non-uniform matric potential Uniform or non-uniform water content Boundary conditions Specified at both ends of domain Matric potential Flux Rainfall Ponding Requirements: θ(h) and K(h) Solution: h(z, t).

16 Soil water proprieties Empirical relationship : Van Genuchten (1980)  (h) = f(  s,  r, , n, m)

17 Computer codes 1. RETC 2. CHEMFLO Interactive Software for Simulating Water and Chemical Movement in Unsaturated Soils Water flow: Richards equation (Richards, 1931) Chemical flow: convection-dispersion equation Solution method: Finite difference By: D.L. Nofziger and Jinquan Wu, 2000 For Quantifying the Hydraulic Functions of Unsaturated Soils M. Th. van Genuchten, F. J. Leij and S. R. Yates, 1991

18 Governing Partial Differential Equation for Chemical Movement c = c(x,t): is the concentration of chemical in the liquid phase S=S(x,t): is the concentration of chemical in the solid phase D=D(x,t): is the dispersion coefficient q = q(x,t): is the flux of water ρ = ρ(x): is the soil bulk density α,β : Degradation rates γ : Production rate convection-dispersion equation

19 Water flow equations Numerical solution Finite Difference Scheme

20 Chemical Transport

21 Study Area

22 Jeddah Makkah


24 Experimental Farm




28 28









37 Experiments and Data Analysis

38 Experiments Constant head permemeter  K s = 13.6 cm/hr

39 Soil moisture retention Pressure plate apparatus

40 Soil water content at applied pressure (bar) cm of water Sample IDSaturation U U U U

41 Experimental soil moisture retention curve

42 RETC code: Van Genuchten (1991) Fitting equation to data n =  = cm -1

43 BTC q = cm/hrC o = 50 mg/l D = 2.3 cm 2 /hr

44 21X Campbell scientific datalogge


46 Experiment 1: Flow in initially dry soil Initial h = -500 cm Constant q = cm/hr Duration = 3.3 hrs

47 Experiment 2: NO 3 leach Initial condition: Depth (cm)Matric potential (cm) Flux = 5 cm/hr C o = 50 mg/l Duration = 1 hr Breakthrough curves of NO 3 - at sensor locations Nitrate concentration along soil column at different times

48 Experiment 3: Nitrate leach to groundwater table Field: Hada Asham Crop: Alfalfa Area: 3.46 ha Irrigation schedule: 8 hr/day Duration: each day another Fertilizer: Urea + Potassium sulphate Groundwater table: 20 – 25 m Irrigation scheme and rainfall events used in the simulation Constant percolation = 0.08 cm/hr

49 Water content distribution

50 Simulated NO 3 concentrations

51 Simulated Ө for 17 days

52 Simulated NO 3 concentrations for 5 months

53 Conclusions الخصائص الهيدروليكية لطبقات تربة هدا الشام الاربعة متشابهة وهذا يدعم جواز اعتبار التربة متجانسة The four observed layers of Hada Asham soil show approximately similar hydraulic properties during soil moisture retention experiment, this would justify treating the soil column as homogeneous with an average moisture retention relationship. 1 2 Convection-dispersion equation is a good representative for solute transport in this study since it show an excellent fit to the observed breakthrough curves. معادلة حركة الملوث المستخدمة تعتبر نموذجية في هذه الدراسة لما اظهرته من نتائج متوافقة مع التجارب العملية 3 NO 3 anion can be considered as a conservative solute in Hada Asham soil, Since inflowing mass was conserved in the effluent during experiments. ايون النترات يعتبر ملوث محافظ في تربة هدا الشام

54 Rainfall events are found to be the main controlling factors of nitrate leach. 4 تؤثر الامطار بشكل مباشر وسريع على حركة النترات 5 Hada Asham soil field is over irrigated causing a potential for nitrate leach. تربة هدا الشام تروى بمعدل زائد عن الحاجة مما يتسبب في تسريع تسرب النترات الى اسفل Conclusions …

55 Recommendations Periodical monitoring of NO 3 - in GW allocated for domestic water supply المراقبة المستمرة للنترات في المياه الجوفية المُعدة للاستعمال المنزلي Continuous monitoring of nitrate in GW after rainfall events المراقبة المستمرة للنترات في المياه الجوفية بعد هطول الامطار Irrigation rate should be equivalent to exact crop water requirement يجب أن يكون معدل الري مساو لاحتياج النبات الفعلي من الماء Study the effect of fertilizer application schedule on nitrate leach for Optimum Fertilization scheme determination دراسة تأثير جدولة تسميد الارض على حركة النترات لتحديد طريقة التسميد المثلى

56 Cont … Environmental impact assessment for cultivated areas subject to GW nitrate contamination تقييم التأثير البيئي للمناطق الزراعية والمياه الجوفية المُعرّضة للتلوث بالنترات Recommendations Agriculture drainage system is recommended for areas of shallow water table يفضل عمل نظام صرف لمياه الري في المناطق ذات مناسيب مياه جوفية ضحلة إدارة الري والتسميد في مواسم الامطار لتجنب مزيد من التلوث Irrigation and fertilization management during rainy seasons to prevent further pollution

57 شكرا لحسن استماعكم Thank You

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