Groundwater pollution by Nitrate transport through soil column

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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 University Saudi Arabia
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Contents
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Objective of the study
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Mathematical models
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Study area
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Application
Results Conclusions
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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
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Nitrogen in our environment
Blue Baby Syndrome
Algae Bloom
methemoglobinemia
An illness that occurs when a child drinks water
containing a large amount of nitrates. The bodys
digestive system converts these to nitrites,
changing oxyhemoglobin to metheglobin, which
cannot carry oxygen. Mucous membranes turn blue,
impairing functions.
Tiny water plants capture the suns energy and
support the food web. Dissolved nitrogen can lead
to sudden overabundance, which blocks sunlight to
water, kills fish by using the waters oxygen,
produces scum or odor, and in some cases,
produces toxins.
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Nitrogen in our environment
Agricultural Fertilizer
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.
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.
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Nitrogen in our environment
Sewers and Septic Tanks
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. N2O is
soluble in fats and used as a propellant for
canned whipped cream.
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.
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Nitrogen in our environment
Dentistry/Medicine
Meat Preservative
Nitrous oxide (N2O), 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.
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.
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Nitrogen in our environment
Lightning Strikes
Soil Bacteria
The high temperatures and pressures that
surround electric storms form nitric oxide (NO)
and nitrogen dioxide (NO2), which reacts with
rain to form nitric acid (HNO3). Nitrates formed
by the interaction of nitric acid and soil
provide nitrates for plant growth.
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.
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Nitrogen in our environment
Farm Animal Waste
Paper Industry
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.
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.
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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 NO3-N (Arbuckle et al. 1988)

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• 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)
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Groundwater Pollution by Nitrate
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Mathematical model
Water flow equation
PDE 1D WF Richards Eq.
Or
? ?(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.
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PDE solution
Requirements ?(h) and K(h)
Solution h(z , t).
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Soil water proprieties
Empirical relationship Van Genuchten (1980)
?(h) f(?s , ?r, ?, n, m)
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Computer codes
1. RETC
M. Th. van Genuchten, F. J. Leij and S. R. Yates,
1991
For Quantifying the Hydraulic Functions of
Unsaturated Soils
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Governing Partial Differential Equation for
Chemical Movement
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Numerical solution Finite Difference Scheme
Water flow equations
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Chemical Transport
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Study Area
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Jeddah
Makkah
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Experiments and Data Analysis
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Experiments
Constant head permemeter ? Ks 13.6 cm/hr
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Soil moisture retention
Pressure plate apparatus
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Soil water content at applied pressure (bar) Soil water content at applied pressure (bar) Soil water content at applied pressure (bar) Soil water content at applied pressure (bar) Soil water content at applied pressure (bar) Soil water content at applied pressure (bar) Soil water content at applied pressure (bar) Soil water content at applied pressure (bar) Soil water content at applied pressure (bar) Soil water content at applied pressure (bar)
0.1 0.2 0.3 0.5 0.75 1 1.5 2 2.5 3
  cm of water 101.6 203.2 304.8 508 762 1016 1524 2032 2540 3048
Sample ID Saturation
U-1 0.3481 0.31 0.22 0.165 0.121 0.0821 0.064 0.058 0.052 0.05 0.04
U-2 0.335 0.29 0.14 0.12 0.1 0.075 0.068 0.06 0.053 0.053 0.05
U-3 0.318 0.3 0.231 0.142 0.114 0.084 0.071 0.06 0.05 0.05 0.045
U-4 0.324 0.28 0.2 0.11 0.1 0.07 0.06 0.05 0.05 0.04 0.03
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Experimental soil moisture retention curve
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Fitting equation to data
RETC code Van Genuchten (1991)
n 2.037 ? 0.0221 cm-1
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BTC
q 10.03 cm/hr Co 50 mg/l
D 2.3 cm2/hr
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21X Campbell scientific datalogge
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Experiment 1 Flow in initially dry soil
Initial h -500 cm Constant q 10.03
cm/hr Duration 3.3 hrs
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Experiment 2 NO3 leach
Initial condition Depth (cm) Matric potential
(cm) 0 -7 10 -13 40 -65
70 -88 100 -114 140 -201
Flux 5 cm/hr Co 50 mg/l Duration 1 hr
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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
Constant percolation 0.08 cm/hr
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Water content distribution
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Simulated NO3 concentrations
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Simulated ? for 17 days
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Simulated NO3 concentrations for 5 months
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Conclusions
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Conclusions
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Recommendations
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Recommendations
Cont
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Thank You