Phytotechnology was applied to assess the capacity of microphytes (algae) and macrophytes (duckweed) to remediate pollutant from Tanjaro River water based on irrigation standards. The results showed clear differences between the untreated and treated polluted Tanjaro River water samples. Untreated and treated water sample were analyses for some physiochemical measurements include; temperature, pH, dissolved oxygen, biological oxygen demand, total dissolved salts, electrical conductivity, turbidity and Chlorophyll a, NO3-, PO43-, SO42-, HCO3-, CO32-, Cl-, Ca2+, Mg2+, Na+, K+, Fe, Co, Cd, Pb, Cr, Cu, As, Zn and Mn. Fifty liter of water sample from Tanjaro River water treated by open pond ex-situ system of algae and duckweed, declines in those values, except for dissolved oxygen and Chlorophyll a. Nutrient removing efficiencies of the algae and duckweed indicate the ability to remove 100% of the Fe, Cd, Pb, Cr and As in the studied water sample, although algae showed a higher efficiency to remove Co, Cu, Zn and Mn in comparison with duckweed; duckweed showed efficiency to remove PO43-, Cl-, HCO3-, CO32-. The calculated value of irrigation water quality index (IWQI) is 12 of the untreated water (low suitability for irrigation) improved after treatment with algae and duckweed to 13 and 14, respectively. Irrigation water quality index (IWQI) improved the suitability for irrigation 8 and 17 % by duckweed and algae, respectively.
The results of irrigation water sampling from the polluted Tanjaro River that used for irrigation frequency, during the special sorghum soil pot experiment (August 1, 2018 to October 1, 2018) concluded the water sampling from the Tanjaro River water showed variation in values of all the measurements and water quality index during the irrigation period in (August 1, 2018 to October 1, 2018), this variation is due to the sewage composition from Sulaymaniyah city.
The results of the sorghum soil pot experiment and irrigation frequency (1-time/week, 2-times/ week, and 3-times/ week) of soil showed a significant difference between irrigation frequency and their effects on soil chemistry. There are positive increases in ratio of metals and nutrients discharging from soil pots during the sorghum experiment. The results showed that irrigation frequency have an effect on the levels of the following metals (Fe, Co, Cd, Pb, Cr, As, Cu, Zn and Mn) mg L-1 discharging through the soil during the time. Also, using the long-term of polluted water from Tanjaro River for irrigation affects the groundwater. However, the results of cations (Ca2+, Mg2+, K+ and Na+ mg L-1) and anions (HCO3-, CO32-, NO3-, PO43- and SO42-) that are concentrated in the discharged water showed that the irrigation frequencies have a positive effect on the cations and anions discharging from soil especially by using the Tanjaro River for irrigation. The results indicated that the ions can reach ground-water through the soil by repeating the polluted water in the long-term of irrigation. These results confirmed that by increasing the irrigation period the values of (DO, pH, EC, TDS, and T) decrease in the discharged water from the soil, except turbidity, as it increases and this result was expected gevin the soil mechanisms working as a filter.
The results of polluted water irrigation effects on the soil chemistry showed a negative relation between irrigation frequency and total heavy metals with non-significant differences between times of irrigation during 2 months of the experiment, except Pb which shows a significant difference with irrigation frequency. The heavy metals’ total concentration was decreased in the soil during the experiment, as they are up taken by sorghum and discharged from the soil. Also, the cations (Ca2+ and Mg2+) showed similar trends in the soil where the concentration decreased in the soil during the experiment and the irrigation frequency showed non-significant differences for Ca2+ and Mg2+ concentrations. On the other hand, K+ and Na+ showed effects by irrigation frequency, where in the 1 and 2-time irrigation/week, the concentration increased in the soil and the 3-time irrigation/week decreased. Results of total P concentration affected by irrigation frequency was increased in the soil under 1 and 2-time irrigation/week and decreased under 3-time irrigation/weeks. Total percentage of nitrogen decreased in the soil, the total percentage of carbon increased in the soil during sorghum pots experiment, and there was a significant difference between irrigation frequency for both (% Nitrogen and % Carbon).
Sorghum has the ability to uptake metals and nutrients in their roots more than in their shoot system, except K+, N, and C as they were observed in higher concentrations in the sorghum shoots. Also, there were significant differences between irrigation frequency in metals and nutrient concentrations in the roots except for Cd, Pb, Cu and K as no significant differences were observed for them. On the other hand, the concentrations of metals and nutrients in the shoots showed low significant differences between irrigation frequencies during the experiment.
The results of increased of metal percentage in the soil after use the Tanjaro River water for irrigation during the sorghum soil pot experiment was also observed in the soil without sorghum (control). The order of the increase was Mn> As> Cu> Cd >Cr > Pb except for Fe, Co and Zn in comparison with the metal content in the initial soil, in conclusion when the soil is irrigated by polluted water from the Tanjaro River the metals accumulated in the soil.
The decision about (algae, duckweed ) ability for metals remediation was evaluated by the biological accumulation coefficient (BAC) these results showed that algae are able to phycoremediate metals Fe, Mn, Cu, Cr, Co and Zn. Duckweed has the ability to phytoremediate metals Fe, Cu, Mn, Cr, Co and Zn. Sorghum can phytoremediate metals Fe, Co, Cr, Pb, Cu, As, Zn and Mn except Cd where BAC>1, and translocate the metals Co, Cr, As, Cu, Zn and Mn to the shoots of sorghum, cannot translocate and accumulate Fe, Cd, and pb in there shoot system, on the other hand have ability to phytostablization of metals Fe, Co, Cr, Cd, Pb, As, Cu, Zn, and Mn). Algae, duckweed, and sorghum cannot accumulate the metals Pb and Cd since the BAC <1, the duckweed showed capacity for heavy metals extraction more than algae and sorghum.
The results of present study showed that algae and duckweed can be used in bioremediation for the Tanjaro River water before using the water body as a source of irrigation. In addition, direct use of polluted water as an irrigation source for those types of plant cannot be used as daily sources for human consumptions. However, potentially using the Tanjaro River water for irrigation has harmful effects on soil, plants and ground-water. This require annual research and monitoring in the future. These findings show the potential of phytotechnology for environmental remediation in an agriculturally important region of Iraq.
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