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Nitrate Pollution In Groundwater-Gaza Strip

Maarten Gischler magisch at netvision.net.il
Thu Apr 10 12:37:11 EST 1997

> From: Mohammad R. Alagha <mralagha at iugaza.edu>
> Cc: 'ECOLOGY {List}' <ecolog-l at umdd.umd.edu>; 'ENVINF-L {List}'
<GROUNDWATER at ias.champlain.edu>; 'INFOTERRA {List}'
<infoterra at cedar.univie.ac.at>; 'RESTORATION {List}'
<resto-eco at macc.wisc.edu>; 'SOIL-CHEM {List}' <SOIL-CHEM at SOILS.UMN.EDU>;
'SOILS {List}' <soils-l at unl.edu>; 'TOXLIST {List}'
<ToxList at esc_server.syrres.com>; 'BIOREMEDIATION {List}'
<bioremediation at gzea.com>; 'toxicology {List}' <toxicol at dl.ac.uk>
In 1995 a very interesting study on nitrate pollution in Gaza's groundwater
was completed by the Environmental Planning Directorate (EPD) in the
Ministry of Planning in Gaza. The study resulted in an action plan, that is
currently being implemented. Copies of the report are available in the
library of EPD.

Main causes of high nitrate in groundwater are: infiltration of untreated
wastewater in cess pits and excess fertilization. The problem is
particularly serious in public water supply wells as these are mainly
located (unsewered) urban areas. Basically it is a not so elegant system of
recycling: wastewater infiltrates in the soil, it is treated to some extent
in soil and aquifer and it is pumped again as "drinking water".

We were lucky to have an excellent set of data. Not only on nitrate
concentration in groundwater but also on fertilisation practices,
population densities and so forth.

We followed an approach of nitrogen balances. In urban areas we calculated
an N-load per ha based on: population density, a per capita N-production
per day, % of population sewered and assuming a certain removal coefficient
to account for volatalisation (NH3), ammonium adsorption, etc. Having
calculated this load for each town and village, we "dissolved" the N-load
in an amount of recharge, percolating to the groundwater. We compared this
with nitrogen concentration and found a remarkable correlation.

In agricultural areas we followed a similar approach and we found that
nitrogen applied through fertilisers is in some crops more than ten times
the potential plant uptake. As a result, nitrate concentrations have jumped
over the last years and we concluded that in some agricultural areas the
nitrogen dissolved in the groundwater is more than enough to cater for the
N-needs of the plants and that any N-fertilisation is a waste of money.
"Dissolving" the N-load in the amount of recharge did not give a very good
correlation with nitrate concentrations found in the groundwater.
Apparently we did not understand and describe the N-removal mechanisms well

EPD started last year with some pilot projects among farmers, in order to
reduce N-input. 

Good luck with further research

Maarten Gischler
IWACO, Consultants for Water and Environment

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