The photo shows a typical village
well. About 11 million Ukrainian people drink water
from such wells.Only 9 %
of those villages have a canalisation. For the cities, this figure
is 91 %. Clean water however can only be expected if the
area around
(mainly groundwater upstream)
is unused,
not cultivated
or
otherwise contaminated. About
consequences for human health and animals see
NO3-article. Polluted wells can
quickly be detected through electrochemical measurements.
For more explanations see
here, write
e-mail or read
publications 22, 25 and smaller
articles! About methods - view
overview!
1.
Introduction
In villages and sometimes in
smaller towns as well, people are dependent on water from
shallow wells. These wells, as shown on the
photos, can be found in streets and gardens. They
contain water from the groundwater surface about < 1 m to >10 m
below the soil surface. In most cases, the water is clear and tasty.
Sometimes the population can get water from a deep well through a
new distribution system, but it is possible that they refuse it
because it is less tasty. The reason for this can be a
higher concentration of iron.
Usually, people are not aware of
the risk connected to the quality of their well water. First of all,
babies are endangered because high nitrate concentrations are
frequent. They lead to high nitrite levels that inhibit the oxygen
transport in the blood. This is known as "blue-baby syndrome" and
was reported to occur in the Poltava region; (10-15 cases according
to official statistics, citied in /1/). Only if humans or animals
die because of a high contaminant level, people start caring about.
The main contaminants of
village well water are nitrate, pesticides,
microbiological contamination and radon. Microbiological
contamination is controlled by the Sanitary-Epidemiological Service
(SES) and if necessary it is reduced by high doses of inorganic chlorine.
In these cases, usually organic matter is also present in higher
concentrations leading to the formation of dangerous chlororganic
compounds.
Other types of pollution are
mostly of local importance. To understand where the contaminants
come from, what the reasons are and what can be changed, it is
necessary to know the flow direction of the groundwater as shown in
fig. 1.
Fig. 1:
Simplified scheme showing the pathway of water from the soil surface
through the aquifer into the next river. Abbreviations: A1 and B1
are places where pollutants are deposed off or digged in the
underground; A2 is a village well reaching the groundwater surface,
B2 is another type of well as often found in private gardens. Water
tubes usually reach deeper layers.
2. Origin
of contaminants
Groundwater resources are
refilled from rain water and smelting snow. It lasts several years
until water from the soil surface reaches the groundwater surface.
The time depends from the rain quantity, evapotranspiration, water
level distance and soil characteristics. Then the water moves
towards the deepest point of the groundwater table. This is usually
the direction towards the next river that drains the river catchment
area. On its way through the soil and the aquifer, clean water can
solve natural compounds (as carbonates, fulvic acids) and
anthropogenic contaminants (as organic pollutants, nitrate,
pesticides). Water that humans have contaminated with organic
matter can be cleaned through filtration, biodegradation etc. A
scheme of bacterial degradation is shown in figure 2. In reality,
much more physical, chemical and biological reactions, influencing
each other, participate in this process. One of the end-products of
this self-purification process is nitrate. Nitrate can only be built
in the presence of oxygen. Bacteria use oxygen for nitrification of
ammonia, which is a degradation product of amino-acids.
Fig. 2.
Biodegradation of organic matter depending on the presence of oxygen
and the degradation end products; at the left hand side (circle)
typical anions in well water.
If the organic mater (in
water or soil) is not depleted, degradation can go on nevertheless
because bacteria can use oxygen bound in anions as nitrate. For this
purpose nitrate and other compounds can be reduced: nitrate is
reduced mainly to N2, iron III to iron II, sulphate to H2S, CO2 to CH4 and so on. Water containing high nitrate concentrations
has only low amounts of iron and is therefore more tasty than water
free of nitrate with high amounts of iron that makes water brownish
and its taste strong. These facts and observations are only very
shortly explained here for water users who are not yet familiar with
them.
3.
Investigation results
Village wells have been
investigated in several regions of the central part of North Ukraine
(Kiev Oblast, Chernigov Oblast: map, fig. 3).
Fig. 3: Map showing roughly the main locations of
sampling points (and results of measurements)
In more than half of the
samples the Ukrainian standard for drinking water (45 mg/L = 10 mg/L
N) is exceeded. Fig. 4 shows a comparison with other water types
as small streams , tap water, artesian wells in Kiev and source
water. Maximum values reach several hundred mg/L NO3 (up to 800 mg/L
was measured and several thousand was orally reported from other
sources but not yet verified).
Fig. 4: Nitrate (NO3-N)
concentrations (median on y-axis) in various types of water in and
around Kiev: I = small rivers in Kiev, II = Kiev tap water, III =
artesian wells in Kiev, IV = natural sources of small streams in and
around Kiev, used for drinking water, V = village wells in northern
Ukraine ;
limit for drinking water ~ 10 mg/L (N).
The next figure (5) gives an
overview on other relevant parameters (el. conductivity, organics and
chlororganics.). High AOX
values are probably the consequence of disinfecting.
Fig. 5: Minimum, maximum, 25 %, 75 % and median value
of el. conductivity (EC in mS/m), nitrate (NO3-N in mg/L N), organic
compounds (SAC_254 in 1/m) und sum of chlororganics (AOX in ug/L).
Further
investigations have been started to find out if soils near the well
(in the upstream direction of ground water flow) are significantly
polluted in case of high nitrate concentrations in the well water.
This was obvious in a few cases of extreme pollution (dung heap,
hotbed, pig breeding). In most other cases this was not visible, but
the comparison of results from soil and water analyses point in this
direction. Fig. 6 and 7 show results. Organic pollution is difficult
to quantify and to distinguish from natural humus. It is assumed
that anthropogenic organic matter has a higher oxygen demand than
humus. Therefore, in a 1st approach, pollution has been quantified
by measurements of the biochemical oxygen demand of 1 g sample
per 1 day (BOD1) and alternatively by BOD1/IL. IL is the loss of
weight after heating the sample at 550 oC for several hours.
Fig. 6and 7: Influence of anthropogenic soil
pollution on nitrate level in the well water.
4.
Consequences
High nitrate
concentration in village wells are not a consequence of
industrialised high intensity agriculture as is the case in Western
Europe. The reason is soil contamination nearby the wells itself.
Main contamination sources are
spreading of waste
water in gardens (if canalisation is lacking) and toilets
use of fertilisers in
private gardens
livestock breeding
Considering the enormous
amount of contaminated wells and huge number of people using its
water, counter measures should have highest priority. It is
recommended to
identify those wells ASAP, inform the population
about health hazards and to
organise counter measures as far as possible. The focus should be on
the areas nearby, upstream the (shallow) wells as shown in fig.8.
Fig. 8: Areas (A 1, B 1) where well water (A 2, B 2)
infiltrated the underground as explained in fig. 1.
Abbr.: A 2 = shallow village well, B 2 deeper well .
The relevant places should be controlled, cleaned and kept
clean as far as possible. Otherwise the use of the well for taking
drinking water should be given up.
The relevant soil area for
deep wells is more difficult to find needing further investigation
or information. In general, the place of contamination is at a
bigger distance upstream from the well and thus, filter distance and
time to reach the well are bigger.
But how to control thousands of
village wells?
Almost always, polluted
wells can be identified within seconds by measuring the electrical
conductivity (EC) on-site. In those cases, the concentrations of
chloride and sulfate are increased leading to a good correlation
with EC:
r_Cl = 0,85 and
r_SO4 = 0,91; (p<0,01 in both cases).
Nitrate too correlates
with EC (r_NO3-N = 0,55; p<0,01) and even AOX (r_AOX = 0,71;
p<0,05). The EC can therefore be used as an indicator for
ground water pollution. If EC is higher than 50 mS/m (500 microS/cm),
pollution should be expected and people should be informed about
this. To minimise the amount of analytical work later in the
laboratory, it is recommended to take a sample and to analyse the
pollution with nitrate and the organic load using the known
ultraviolet absorption methods (see also extract from method data bank).
Which other analyses are necessary to perform should be decided by
the responsible water expert!!! Unfortunately, there is one
obstacle. The 2 mentioned express methods (EC and UV
determination of nitrate) are not certified in Ukraine, but they are
recommended here as necessity indicators for further "official"
measurements.
Two more graphics show
the correlation between nitrate and
electrical conductivity based on two investigation series
in different regions, Zhytomir, 140 km west of Kiev and data from
the 2nd graphic (below) are from Sokolovka, about 100 km north of
Kiev.
Another factor
influencing the EC is related to the soil type and the geological
background. Examples show that this background has to be taken
into account to reach a better prognosis security. The relationship
between organic soil load and nitrate in the groundwater are
highlighted here.
Literatur:
/1/ TSVETKOVA, A.
(2002): Drinking Water in Ukraine: Communication and Empowerment for
Local and International Action - Mama 86 (edit.), Kiev, 42 p.
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