الفهرس 
Material and methodsOnly 14 pages are availabe for public view
 |  | from | 189 |  |  |
| | | from | 189 | | |
Abstract
The aim of this investigation was to study (i) the effect of using
sewage eflluents and industrial waste water in irrigation on the physical and
chemical properties of soil and its content of Cu, Zn, Pb, Cd, Ni and Co, (ii)
the effect of industry fall-out derived from some chemical plants and smelters
on the status of the tested heavy metals in the neighboring soils, (iii) the effect
of motor vehicle exhausts on the total and forms of heavy metals in the
roadside soils, and (iv) the contamination of plants with the above mentioned
heavy metals.
To achieve the first objective, three locations in El-Gabal El-Asfar
represent soils irrigated with sewage eflluents for 0, 20 and 60 years and
another two locations at Bahteem representing soils irrigated with indu~trial
waste water were selected. Soil samples from five different depths from each
profile namely, 0-5, 5-10, 10-25,25-60 and 60-100 em and correspondence
plant samples were collected.
To accomplish the second objective, five different chemical plants and
smelters were selected and two profiles were dug around the source, the first
one was on a 5m away and the second was 100m away from the source of
pollution. Soil samples were taken from the different depthes as mintioned
above and samples from the plants grown on the different locations were
collected.
The third objective was fulfilled through collecting soil and plant
•samples from six locations differing in their distance and direction from the
motor way.
The physical and chemical properties of selected soils were
determined. The total content, DTPA-extractable and fractions of Cu, Zn, Pb,
Cd, Ni and Co in soil samples were measured. The fourth objective was
largely met through the determination of heavy metals in plant samples. The
obtained results could be summarized as follows:
The effect of using sewage effiuentes and industrial waste water in
irrigation on the physical and chemical properties of soils was obvious and the
most affected soil properties were soil organic matter, soil pH, CEC,
exchangeable cations and total soluble salts, wherase the other properties were
less affected. With increasing the peroid of irrigation, soil organic matter was
increased, but soil pH and total soluble salts were decreased.
l-Copper
soil content of copper was relatively high in soils received sewage
water for 60 years and ranged from I to 475 mglkg soils, DTPA-extractable
Cu varied from 0.1, to 24.4 mglkg soil, while the distribution of Cu among
various fractions followed the following order:
Residual > organically bound (Cu~PYR> Occluded on Fe, AI and Mn Oxides
(Cu-Ox + Cu-meA + Cu-HAH) > specifically adsorbed (Cu-AC» soluble +
exchangeable (Cu-CA).
Copper in soils exceeded the maximum tolerable level in site 3
irrigated with sewage water for 60 years, as well as in sites 4 and 5 irrigated
with industrial waste water. However, in soils around smelters, the content of
Cu was comparable with that of the maximum tolerable level. The
concentration of Cu in the correspondence plants grown on soils irrigatedfor
60 .years, soils around smelters and soils adjacent to the highway tended to be
toxic.
2-ZinCi
The content of zinc in soils was generally high easpecially in soils of
El-Gabal El-Asfar. Total Zn ranges from 11to 1075mg/kgsoil, while DTPAextractable
Zn being from 0.22-5000 mg/kg soil. The distribution of Zn
among the chemical fractions was followed this order: Residual> Organically
bound> Occluded on Fe, AI and Mn Oxides> specifically adsorbed> soluble
+ exchangeable.
Total Zn in soils surpassed the maximum tolerable level in profile 3
(soils irrigated with sewage effiuents for 60 years), while around the smelters
(profiles 12,13), the concentration of Zn was relatively high and beyond the
maximum level (30 mg/kg). Zn concentration in the growing plants was within
the permissible level with a slight increase in those grown on soils irrigated
for 60 years.
3-Leadi
Total Pb in soils and DTPA-extractable Pb ranged from 13 to 226 and
from 0.02 to 19.0 mg/kg, respectively. The distribution ofPb among the
different chemical forms followed this order, Residual > PYR > specific
adsorbed> Occluded on Fe, AI and Mn oxides> soluble + exchangeable.
Total Pb in soils around the chemical plants and in those adjacent to
the highway is still within the permissible level. However, in soils irrigated
with sewage effiuents for 60 years (profile 3), Pbhas exceeded the threshold
value of 100 mg/kg soil.
Soils of profiles 4 and 5 irrigated with industrial waste waters contain high
amount ofPb comparable to that reported as threshold value (100 mglkg soil).
The concentrations of Pb in plants grown on soils irrigated with sewage
effiuents were highly polluted especially in profile (3). Plants grown on soils
adjacent to the highway contained higher amounts of Pb and there is a
tendency to reach the higher level of the critical toxicity range (10-20 ug/g).
4-Cadmium:
Cadmium content in soils was generally high in all investigated soils.
Total Cd content ranged between 3.0 to 13 mglkg soil, while DTPAextractable
Cd varies from 0.01 to 1.4 mg/kg soil.
Total Cd in the investigated soils was surpassed the limited reported to
be maximum tolerable level (5 Ilg/g)·
The occurrence of Cd in the different chemical fractions followed this
order: Residual> soluble + exchangeable> organically bound> Occluded on
Fe, Al and Mn oxides. > specifically adsorbed, which means that Cd is more
leachable and mobile than the other elements.
Concerning the concentration of Cd in plants grown on soils irrigated
with sewage effiuents for 60 years (profile 3), it was increased lind tended to
reach the toxic level. Plants grown on soils irrigated with industrial waste
water contain high Cd concentration very close to levels of the toxicity range.
However, those grown on the other locations contain high concentration of Cd
located within the critical toxicity range (5-10 Ilg/g)·
5-Nickel:
The content of Ni in soils ranges between 4.4 and 16~ mg/kg soil,
while DTPA-extractable Ni varied from 0,01 to 1.4 mglkg.
The distribution of Ni among the fractions followed the order of:
Residual> specifically adsorbed> occluded on crystalline Fe and AI oxides
organically bound> soluble + exchangeable> Occluded on amorphous Fe and
AI oxides.
The threshold value (100 mglkg) was exceeded by the total Ni in soils
irrigated with industrial waste water (profiles 4,5) and in soils around smelters
(profiles 12,13). Total Ni content in profiles (16 and 17) located on the east
side of the road as well as in profiles 19 and 20 located on the waste side
surpassed the thresold value.
The concentration of Ni in plants grown on the soils irrigated with
sewage and industrial waste water was high, but still less than the level of
toxicity. The Ni contents in plants grown on soils around the chemical
factories or on soils adjacent to the highway are not harmful to animals.
6-CQbalt:
Total Co content in soils ranges from 19 to 59 mglkg soil, and the
DTPA-extractable Co varies from 0.16 to 1.43 mglkg soil.
The distribution of Co among the fractions was followed this order:
Residual> organically bound> Occluded on Fe and AI, oxides> specifically
adsorbed> soluble + exchangeable.
Total Co content in soils was affected by sewage and industrial waste .
water, industry fallout and the motor vehicle exhaust fums.
Plants grown on soils irrigated with sewage etnuents for 60 years
contain high level of Co comparable to that of critical toxicity range. On the
other hand, those grown on soils around chemical plants and smelters, or
grown on soils adjacent to the highway contained less Co and their contents
did not exceed that of the toxicity level.
The following remarks could be eeneludede
1- Soils irrigated with sewage effluents are seriausly contaminated with Cu,
Zn, Pb and Cd. Generally these heavy metals in addition to Ni and Co
were increased with increasing the period of irrigation with sewage
etnuents and tended to decrease with soil profile depth.
2- The heavy metals were relatively high in soils around the chemical plants
and smelters. Moreover, the content of Cu, Pb, Zn, Cd, Ni was high and
exceeded the permissible level only in soils around smelters..
3- Soils adjacent to the highway contain relatively high concentrations of
heavy metals which exceeded the permissible levels in some locations.
Generally, the concentration of heavy metals decreased with increasing
both of distance from the road and profile depth.