Kouli_etal_2008_Groundwater modelling_BOOK.pdf - Pantelis ...

Distribution and Source of Nitrogen Compounds in the Groundwater of Kuwait 387
Overall Conclusions
In general, the nitrate concentration is higher in the Kuwait Group aquifer than that in the
Dammam Formation aquifer. In fact, a decreasing trend of nitrate concentration with depth,
from the Upper Kuwait Group aquifer through the Lower Kuwait Group aquifer to the
Dammam Formation is discernible from the available data. The nitrate-nitrogen
concentration in the Kuwait Group aquifer varies in the range of 0 to 163 mg/L with an
overall decreasing trend from the southwest to the east and the northeast.
Based on the available evidence, it is proposed that the source of high nitrate
concentration in the Kuwait Group aquifer in the southwestern parts of Kuwait, that include
the Umm Gudair well field and the Al-Mutla area, could be from the dissolution of minerals
such as soda and potassium niters in the aquifer zones where nitrate is concentrated. The
nitrate minerals in the aquifer may be derived either from atmospheric precipitation or from
the erosional products from the highlands of Saudi Arabia. The nitrate salts in this area
represent the majority of the nitrate mass in the groundwater of Kuwait. However, the
increased levels of nitrate concentrations in the Al-Abdally area are suspected to have been
created from the application of fertilizers in the farms of that area.
For the major part of the area covered by the State of Kuwait, the anthropogenic sources
such as fertilizer applications or dumping of wastes were ruled out as a major contributor of
nitrates to the aquifer due to (1) absence of correlation between areas of fertilizers and waste
applications and zones of high nitrate concentrations, and (2) absence of isotopic signature of
enrichment in N 15 over N 14 in the limited number of samples of groundwater collected both
from the urban and agricultural areas and away from them. Migration of anthropogenic nitrate
across the border with Saudi Arabia was not thought to be a source for nitrate contamination
in Kuwait for the reasons mentioned above, and due to the fact that the transported nitrate
would require thousands of years to arrive in Kuwait from its suspected sources. Organic
material as a significant source was also excluded because of only a feeble correlation
between the groundwater carbon and organic matter content and nitrate concentration and
also due to the presence of minor amount of organic nitrogen relative to the total nitrogen in a
few of the samples analyzed for these parameters.
The low nitrate concentration (< 10 mg/L) in the uppermost saturated section of the
Kuwait Group aquifer in the Al-Raudhatain area of northern Kuwait for most of the samples
conforms well to the general acceptance of the fact that the shallow freshwater lenses in this
area have been formed by the infiltration of rainfall run-off accumulated in the depressions.
As regards the ammonia concentration, all of the collected groundwater samples showed
levels that were below the permissible limits of ammonia in drinking water (1.5 mg/L) as set
by the World Health Organization (WHO) of the United Nations.
The nitrate concentrations in the Dammam Formation aquifer is significantly lower than
that in the Kuwait Group aquifer, being in the range of 0 – 127 mg/L. A general decrease in
the nitrate-nitrogen concentration towards the east and the southeast is indicated for this
aquifer also, though in details, there are some irregularities in its distribution. The lower
nitrate content of the Dammam Formation aquifer points towards ancient recharge from
precipitation in the highlands of Saudi Arabia.
To verify the proposed conceptual model for the origin of high nitrate in the groundwater
of Kuwait, it is important to collect core samples of both the aquifers from areas with high