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Wenlin W.,Nanjing Normal University | Wenlin W.,Nanjing Institute of Environmental Sciences | Ruiming H.,Nanjing Normal University | Yinjing W.,Jiangsu Environmental Engineering Consulting Center | And 5 more authors.
PLoS ONE | Year: 2014

Rhizosphere oxygen profiles are the key to understanding the role of wetland plants in ecological remediation. Though in situ determination of the rhizosphere oxygen profiles has been performed occasionally at certain growing stages within days, comprehensive study on individual roots during weeks is still missing. Seedlings of Acorus calamus, a wetland monocot, were cultivated in silty sediment and the rhizosphere oxygen profiles were characterized at regular intervals, using micro-optodes to examine the same root at four positions along the root axis. The rhizosphere oxygen saturation culminated at 42.9% around the middle part of the root and was at its lowest level, 3.3%, at the basal part of the root near the aboveground portion. As the plant grew, the oxygen saturation at the four positions remained nearly constant until shoot height reached 15 cm. When shoot height reached 60 cm, oxygen saturation was greatest at the point halfway along the root, followed by the point three-quarters of the way down the root, the tip of the root, and the point one-quarter of the way down. Both the internal and rhizosphere oxygen saturation steadily increased, as did the thickness of stably oxidized microzones, which ranged from 20 mm in younger seedlings to a maximum of 320 mm in older seedlings. The spatial patterns of rhizosphere oxygen profiles in sediment contrast with those from previous studies on radial oxygen loss in A. calamus that used conventional approaches. Rhizosphere oxygen saturation peaked around the middle part of roots and the thickness of stably oxidized zones increased as the roots grew. © 2014 Wenlin et al. Source


Tu Y.,Jiangsu Academy of Environmental Sciences | Zhang Y.,Jiangsu Academy of Environmental Sciences | Xu J.,Jiangsu Academy of Environmental Sciences | Tang M.,Jiangsu Academy of Environmental Sciences | And 3 more authors.
Chinese Journal of Environmental Engineering | Year: 2015

The effect of ozonation on a typical effluent in a sewage plant of a chemical industry park was studied. Molecular weight distribution (MWD), hydrophilicity and hydrophobic separation, fourier transform infrared spectrometry were used to analyze water quality before and after ozonation. The removal rates of COD and UV254 were 37.9% and 55%, respectively with an ozone duration of 60 min. Partially hydrophobic substances were oxidized the hydrophilic small organic molecules after the ozonation, and the removal efficiency of the hydrophobic substance in water was higher than the hydrophilic substance. Ozonation changed the MWD of the wastewater, increasing the percentage of small-molecular-weight organics (<1×103 kDa) from 56.3% to 69.4%, and decreasing the percentage of big-molecular-weight organics (>1×105 kDa) from 24.2% to 9.6%. The results of the FT-IR spectra demonstrated that ozone oxidizes organic pollutants selectively. The ozonation can significantly remove the organic compounds containing unsaturated bond, phenols, alcohols, etc. in the water, but it almost has no degradation reacting with saturated alkanes. © 2015, Science Press. All right reserved. Source


Wang W.,Nanjing Normal University | Wang W.,Nanjing Institute of Environmental Sciences | Wang G.,Nanjing Normal University | Wan Y.,Jiangsu Environmental Engineering Consulting Center | And 5 more authors.
Shengtai Xuebao/ Acta Ecologica Sinica | Year: 2013

Under light or dark conditions, the change of the radial oxygen loss at the points of 1/4, 1/2 and 3/4 far from root stem base (root 1/4, 1/2, 3/4) and root tip (root 1) and its micro-interface were measured in-situ by soluble oxygen microelectrode for A. calamus seedlings and adult A. calamus plants in a typical wetland. Sediment from natural lakes was used as experimental substrates and a micro motor was used to control the soluble oxygen microelectrode to verify the accuracy of the vertical micro position. The result showed that: there was always an oxygen diffusion layer with an increasing gradient of oxygen saturation from the root surface to the anaerobic layer of sediment in the A. calamus roots in light or dark conditions. Oxygen diffusion layer thickness was 0. 18-0. 68 mm and maximum oxygen saturation was 42. 9% under light condition and oxygen diffusion layer thickness was 0. 22-0. 38mm and maximum oxygen saturation was 21. 5% under dark condition. The oxygen diffusion capacity of root points at 1/2, 3/4, 1 of adult plants was significantly higher than those of the seedlings but was insignificant at the point of 1/4, oxygen diffusion layer thickness increased from 0. 40, 0. 32, 0. 26mm to 0. 68, 0. 52, 0. 46mm and maximum oxygen saturation increased from 6. 4%, 3. 6%, 4. 1% to 42. 9%, 22. 5%, 10. 2% under light condition. Oxygen diffusion layer thickness increased from 0. 30, 0. 28, 0. 24mm to 0. 38, 0. 34, 0. 36mm and maximum oxygen saturation increased from 3. 5%, 4. 0%, 3. 1% to 21. 5%, 12. 5%, 11. 6% under dark condition. The influence of light on oxygen diffusion capacity of different root part at different plant growth stages were different. Light had significant influence on root 1/2 of seedlings and root 1/2, 3/4 of adult plant (light treatment exceeded dark treatment significantly, P<0. 01), but had no significant influence on root 1/4, 3/4, 1 of seedlings and root 1/4, 1 of adult plant (P>0. 05). As to the spatial variation of root oxygen release, it showed a tendency of root 1/2> root 3/4, root 1, root 1/4(P<0. 01,P>0. 05)and root 1/2> root 3/4> root 1> root 1/4(P<0. 01)respectively for seedlings and adult plants under light condition. It showed a tendency of no significant difference among root 1/2, 3/4, 1, 1/4 and root 1/2> root 3/4, 1> root 1/4(P<0. 01)respectively for seedlings and adult plants under dark condition. The phenomenon of minimum oxygen diffusion capacity at root 1/4 was mainly induced by the oxygen diffusion barrier in root stem base. Spatial difference of the oxygen diffusion capacity of root 1/2, 3/4, 1 were mainly affected by internal oxygen diffusion capacity and root biomass differences. The stronger the internal oxygen diffusion capacity, the more significant influence on spatial difference of the root oxygen diffusion capacity induced by root biomass differences. On the contrary, root biomass difference would not lead to spatial difference of the root oxygen diffusion capacity. For example, the oxygen diffusion capacity of the seedlings had no significant difference among root 1/2, 3/4, 1 under dark condition. Source


Wang W.,Nanjing Normal University | Wang W.,Nanjing Institute of Environmental Sciences | Wan Y.,Jiangsu Environmental Engineering Consulting Center | Liu B.,Nanjing Normal University | And 6 more authors.
Shengtai Xuebao/ Acta Ecologica Sinica | Year: 2013

In the process of soil gradual drought, the growth of typical wetland plant Acorus calamus in dry condition and control condition were investigated. The soil water contents of dry group were about 55% (0th day), 40% (3th day), 30% (6th day), 20% (9th day), 10% (11th day) and 5% (12th day) and average soil water content of the control group was (53.49±0.6)% during the experiment period. Meanwhile, Photosystem II (PSII) photochemical efficiency (Fv/Fm), quantum yield (Yield), photochemical quenching (qP), non-photochemical quenching (qN) were also measured by a submersible, pulse-amplitude modulated (PAM) fluorometer: Diving-PAM.The results showed that the decline of soil water content in a short term (soil water content declined from 53.86% to 42.6%, on the 0th-3th day) was beneficial to the growth of dry group Acorus calamus. Fv/Fm, Yield, qP were much high than those of the control group (P<0.05), while qN was lower than control group. Compared with control group, average plant height, leaf width and leaf biomass, root biomass of dry group increased by 4.35%, 3.13%, 12.50%, 17.82%, respectively. With soil becoming drought gradually (soil water content declined from 42.6% to 18.02%, on the 3th-9th day), the growth of drought group Acorus calamus was restrained gradually and yield and qP value began to decrease. The qN value rose from 0 to 0.403 quickly and was much higher than those of control group (P<0.05). The dry group plant began to suffer from soil drought stress and presented low photo-inhibition phenomenon. High qN value detected in the study demonstrated that they could protect PSII by increasing heat dissipating. At the same time, there was no significant difference of Fv/Fm between drought group and control group, which also indicated that photosynthesis structure of PSII was unspoiled. At the same time,Acorus calamus plant reduced water transpiration and promoted water absorption to protect itself from soil drought pressure by reducing leaf area, leaf water content and root water content. On the 9th day, the leaf width, leaf water content and root water content of dry group declined to 89.1%, 92.5% and 95.8% of control group respectively.With more serious soil drought degree(soil water content declined from 18.02% to 4.5%, on the 9th-12th day), the growth of dry group plant was significantly restrained. The yield and qP value decreased quickly and were much lower than those of the control group. The photosynthetic efficiency decreased significantly. Meanwhile, Fv/Fm value began to be much less than that of the control group and qN value reduced to 0, which indicated that photosynthesis structure of PSII has begun to be destroyed and the capacity of dissipating heat has disappeared. On the 11th and 12th day, leaf water content of dry group declined to 75.79% and 68.78% respectively. The small leaf began to wither and decline, followed by the big leaf. The above phenomenon indicated that high plant biomass was weak to keep plant water content in the process of soil gradual drought, 80% of leaf water content was the critical value to maintain Acorus calamus plant survival. Source


Yin-Jing W.,Jiangsu Environmental Engineering Consulting Center | Wen-Lin W.,Nanjing Institute of Environmental Sciences | Wen-Lin W.,Nanjing Normal University | Feng Z.,Nanjing Normal University | And 5 more authors.
Journal of Ecology and Rural Environment | Year: 2013

Samples of surface soils near the outlets of farmer household septic tanks and samples of the effluents from the tanks were collected in a plain river network region typical of the Taihu Lake Basin for use in an in-laboratory experiment with simulated rainfall (for summer, 30 mm per event and for winter 5 mm per event, typical of the region) controlled temperature (27 °C for summer and 5 °C for winter, typical of the region) and simulated pollutant load [TN: (2. 35± 0. 06) g · m-2 · d-1, NH4 + -N: (2.08±0.04) g · m-2 · d-1, TP: (0. 21±0.01) g · m-2 · d-1, COD: (11. 14±0. 59) g.m -2 · d-1] to estimate pollutants abatement rate in the polluted surface soils and to explore rules of the abatement as affected by seasons (summer and winter) and synoptic process (before the rain, during the rain, after the rain). Results show that TN abatement rates, no matter whether before the rain, in the rain, or after the rain, all showed a tendency of summer < winter (P<0. 05 or P<0.001), and on the contrary, NH4 + -N abatement rates all showed a reverse trend of summer > winter (P<0. 01). TP abatement rates showed a tendency of summer > winter (P<0. 001) before the rain and after the rain, but COD abatement rates did not differ much between summer and winter. TP and COD abatement rates in the rain both showed a tendency of summer < winter (P<0. 01 or P<0. 001). As to difference between weather processes, TN abatement rates in summer showed a tendency of after the rain > before the rain> in the rainy days (P<0. 01), TP and COD abatement rates in summer showed a tendency of before the rain~ after the rain> in the rainy days (P>0. 05, P< 0. 01), whereas, NH4 + -N abatement rates in summer did not differ much between synoptic processes and TN, NH4 + -N, TP and COD abatement rates in winter did not either (P>0. 05). So, the TN abatement rate before the rain, in the rainy days, after the rain in summer and in winter was 38. 5%, -25. 0%, 46. 0% and 50. 4%, respectively. The NH4 + -N abatement rate in summer and in winter averaged 91. 5% and 85. 5%, respectively. The TP abatement rate in the rainy days in summer, in the rest of summer and in winter averaged 63. 3%, 93. 1% and 82. 7%, respectively. The COD abatement rate in the rainy days in summer and in the rest of the year was 8. 2% and 66. 2%, respectively, on average. Source

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