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261.
Water Security in Uzbekistan: Implication of Return Waters on the Amu Darya Water Quality 总被引:1,自引:0,他引:1
Crosa G Stefani F Bianchi C Fumagalli A 《Environmental science and pollution research international》2006,13(1):37-42
- DOI: http://dx.doi.org/10.1065/espr2006.01.007
Goal, Scope and Background Amu Darya river, one of the main water resources of Uzbekistan, shows a relevant longitudinal enrichment of soluble contents
which strongly limits the human uses of its waters. Because of the low natural run-off processes, salts and pollutants are
mainly driven to the river by the return waters used for washing and irrigating the surrounding lands. The influence of return
waters on stream quality is dramatically relevant in the lower reaches of the river where almost all the flowing waters have
been previously used for the agriculture practises. To provide analytical evidence on the potential effects of return waters
on the quality of the Amu Darya river, the paper reports and comments data on salinity and metals contents of the waters flowing
in the artificial channel network of Bukhara and in the Amu Darya river, from Bukhara up to the dam forming the Tuyamuyn Hydro
Complex (THC).
Methods A total of 15 sampling sites were selected for the analytical survey: Two sites were located on the Amu Darya river downstream
from the inflow of the return waters from Bukhara, two in the river entering in the THC, and three downstream from the dam
forming the reservoir complex. The waters entering and leaving the Bukhara agricultural area were sampled in two main collectors,
while the waters flowing in the channel system were sampled in six distinct collectors. The following parameters were considered
in the survey: pH, Oxygen, Hardness, Salinity, Conductivity, P-PO4 3–, P tot, N tot, N-NO3 2–, N-NO2 –, COD, Ca2+, Mg2+, Fe,
Mn, Zn, Cr, Cu, Ni, Cd, Pb.
Results and Discussion Salt concentrations below 1000 mg/l were measured in the Amu Darya waters upstream to Bukhara. In the drainage system, salinity
exceeds the palatability limit and reaches the maximum peak of 3200 mg/l in the outflow collector. Due to dilution effects,
salinity returns to lower values (400–700 mg/l) along the Amu Darya river downstream from Bukhara; calcium and magnesium resulted
the major constituents of the overall salinity. No serious metal contaminations were detected in the waters entering and leaving
the examined channel system. Differently, the Amu Darya waters upstream to the THC showed a relevant metal contamination,
with Cr, Ni, Fe concentrations exceeding the limits for human consumption. In the downstream sites, located in the Tuyamuyn
Hydro Complex and in the Amu Darya river flowing out from this reservoir, excluding Fe, all the examined metals showed lover
concentrations and values below the normative limits.
Conclusion The direct human consumption of the lower Amu Darya waters is strongly limited by salinity and by metal contamination. Although
the salinity of the return waters from the Bukhara drainage system results in above normal limits, no corresponding increases
were measured in the Amu Darya river downstream from the return water inflow at the time of the survey. As for the metal contamination
of the Amu Darya river, the survey revealed the presence of relevant sources of metal contamination downstream from Bukhara
external to the agricultural drainage system. This contamination resulted in reduced sedimentation processes taking place
in the limnetic zones of the Amu Darya river upstream to the dam forming the Tuyamuyn Hydro Complex.
Recommendation and Outlook To fully understand the longitudinal increase of Amu Darya salinity, an evaluation of the cumulative effects of the loads
from the main agricultural areas is required, also by using mass-balance models. As for the metals, an investigation should
be addressed to identify the anthropogenic sources of contaminations present in the lower Amu Darya region and the metal loads
should be diverted. 相似文献
262.
Giuseppe Forlani Michele Bertazzini Samuele Giberti Dorota Wieczorek Paweł Kafarski Jacek Lipok 《Environmental science and pollution research international》2013,20(5):3263-3270
As a consequence of increasing industrial applications, thousand tons of polyphosphonates are introduced every year into the environment. The inherent stability of the C–P bond results in a prolonged half-life. Moreover, low uptake rates limit further their microbial metabolization. To assess whether low detergent concentrations were able to increase polyphosphonate utilization by the cyanobacterium Spirulina platensis, tolerance limits to the exposure to various detergents were determined by measuring the growth rate in the presence of graded levels below the critical micellar concentration. Then, the amount of hexamethylenediamine-N,N,N′,N′-tetrakis(methylphosphonic acid) that is metabolized in the absence or in the presence of sublethal detergent concentrations was quantified by 31P NMR analysis on either P-starved or P-fed cyanobacterial cultures. The strain tolerated the presence of detergents in the order: nonionic > anionic > cationic. When added to the culture medium at the highest concentrations showing no detrimental effects upon cell viability, detergents either improved or decreased polyphosphonate utilization, the anionic sodium dodecyl sulfate being the most beneficial. Metabolization was not lower in P-fed cells—a result that strengthens the possibility of using, in the future, this strain for bioremediation purposes. 相似文献