Impact of Simulated Irrigation with Treated Wastewater and Saline-Sodic Solutions on Soil Hydraulic Conductivity, Pores Distribution and Fractal Dimension
Résumé
Irrigation with treated wastewater which has the characteristics of
higher salt content, larger sodium adsorption ratio (SAR), and more
organic matter and suspended particles can cause the deterioration of
the soil environment. Ordinary water, treated wastewater, and
saline-sodic solutions with SAR = 3, 10 and 20
(mmolc·L− 1)0.5,
respectively, were used as five irrigation water types, and the changes
of soil saturated hydraulic conductivity (Ks), soil pores distribution, and
soil pores single fractal dimension (Dm) were studied after simulated
irrigation for 1 and 2 years with simulated irrigation systems, which
consisted of soil bins and simulated evaporation systems. The results
showed that soil Ks in the following descending
order: CK > SAR3 > WW > SAR10 > SAR20, and the adverse
effects on soil Ks caused by suspended solid
particles and dissolved organic matter might play a more significant
role than sodium in treated wastewater. The 0-5 cm soils had a smaller
single soil pore area but larger pores quantity after simulated
irrigation, the distribution of soil pores which was irrigated with
treated wastewater had a smaller change compared with saline-sodic
solutions treatments, and it showed the soil pores structure binary
image was an effective method to analysis soil pores distribution. Soil
Dm
increased after simulated irrigation, and the smallest was the soil
simulated irrigation with treated wastewater for 1 year, because the
plugging and filling of suspended particles and dissolved organic matter
in treated wastewater made the soil pores well distributed, but the soil
Dm did not
increase with increasing of SAR levels in irrigation waters. The
relative SAR levels irrigation to soils and soil Ks had a good linear correlation
relationship, while the relationship between soil Dm and the relative
SAR levels irrigation to soils was very complicated. The soil Dm which calculated
from soil binary images could not well reflect the hydraulic
conductivity of saturated soil. Irrigation with treated wastewater had a
greater effect on soil Ks than soil Dm, comparing with
saline-sodic solutions which had the similar SAR value. It was suggested
that the future research should consider both the horizontal and
vertical directions of soil Dm to well reflect the soil
Ks.
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