Yajun Qiao

Phytoremediation potential of Acorus calamus in soils co-contaminated with cadmium and polycyclic aromatic hydrocarbons

Phytoremediation is a promising technology for the remediation of sites co-contaminated with inorganic (heavy metal) and organic pollutants. A greenhouse experiment was conducted to investigate the independent and interactive effects of cadmium (Cd) and polycyclic aromatic hydrocarbons (PAHs) on the growth of the wetland plant Acorus calamus and its ability to uptake, accumulate, and remove pollutants from soils. Our results showed that growth and biomass of A. calamus were significantly influenced by the interaction of Cd and PAHs after 60 days of growth. The combined treatment of low Cd and low PAHs increased plant biomass and Cd accumulation in plant tissues, thus enhancing Cd removal. Dissipation of PAHs from soils was not significantly influenced by Cd addition or by the presence of plants. Correlation analysis also indicated a positive relationship between residual concentrations of phenantherene and pyrene (PAHs), whereas enzyme activities (dehydrogenase and polyphenol oxidase) were negatively correlated with each other. Cluster analysis was used to evaluate the similarity between different treatments during phytoremediation of Cd and PAHs. Our results suggest that A. calamus might be useful for phytoremediation of co-contaminated soil.

Effects of reclamation on heavy metal pollution in a coastal wetland reserve

Owing to accelerating reclamation activities in the coastal wetland reserves, it is of great importance to analyze the effects of wetland reclamation on heavy metal pollution in these areas. Soil samples were collected from reclamation and natural habitats in Yancheng National Nature Reserve for Coastal Rare Birds in Jiangsu, China to investigate the effects of reclamation on the total amounts, availability, and vertical distribution of seven elemental heavy-metal pollutants. In general, the total amount and availability each element were relatively low in the two habitats and were classified as “no pollution”. Reclamation was found to significantly increase the total amount of As, Cu, and Zn as well as the pollution degrees of As, Cr, and Zn. The availability of Cu, Pb, Cd, and Cr can also be significantly affected by reclamation. Furthermore, surface-accumulation patterns of the total amounts of these heavy metals could be observed in both habitats, and the availabilities of these elements were higher in deeper soils. Reclamation also had significant impacts on the vertical distribution of Cu, Pb, Cd, and Zn. It is essential to properly monitor nearby aquacultural activities, freshwater irrigation, and traffic pollution during plant harvest to alleviate the negative effects of these human activities.

Performance of a large-scale wetland treatment system in treating tailwater from a sewage treatment plant

Water quality standards pertaining to effluent from sewage treatment plants (STPs) in China have become more stringent, requiring upgrading of STPs and entailing huge capital expenditure. Wetland treatment systems (WTSs) are a low-cost and highly efficient approach for deep purification of tailwater from STPs. The Hongze WTS (HZ-WTS), a large-scale surface-flow constructed wetland, with a total area of 55.58ha and a treatment capacity of 4×104m3day–1, was built for the disposal of tailwater from STPs. The aim of the present study was to evaluate the performance of HZ-WTP with regard to seasonal variations and to compare treatment costs with those of other STPs. The performance of the HZ-WTS was evaluated in 2013 using online monitoring. HZ-WTS exhibited significant removal efficiency of ammonia nitrogen (NH4+-N), chemical oxygen demand and total phosphorus (mean±s.d., percentage removal efficiency 56.33±70.44, 55.64±18.58 and 88.44±22.71% respectively), whereas there was significant seasonal variation in the efficiency of NH4+-N removal. In addition, the average treatment cost was ¥0.17m–3, significantly lower than the corresponding value for other STPs. Therefore, WTSs are recommended for use with STPs in order to improve waste water quality in a cost-effective manner.

Elevated salinity inhibits nitrogen removal by changing the microbial community composition in constructed wetlands during the cold season

In the present study we investigated whether subsurface flow constructed wetlands (SSF-CWs) can remove nitrogen from saline waste water and whether salinity affects nitrogen removal during the cold season (mean water temperature <10°C). Eight Iris pseudacorus-planted SSF-CWs were fed with normal (salinity 1.3–1.5‰; CWP) or saline (salinity 6.3–6.5‰; CWP+) waste water; similarly, eight unplanted SSF-CWs were fed with normal (CWU) or saline waste water (CWU+). The systems were run continuously at a hydraulic loading rate of 187.5mmday–1 and a hydraulic retention time of 4 days. Nitrogen removal efficiency, plant parameters and bacterial abundance and community composition were measured. In CWP, 80% of NH4+-N and 52% of total nitrogen (TN) were removed. In contrast, the removal rates of NH4+-N and TN in CWP+ were reduced by 27 and 37% respectively. In the presence of higher salinity, not only were there decreases in plant biomass (32.1%) and nitrogen uptake (50.1%), but the growth, activity and oxygen release of roots were also reduced (by 37.8, 68.0 and 62.9% respectively). Bacterial community composition also differed under conditions of elevated salinity. Elevated salinity is associated with lower nitrogen removal in SSF-CWs, which we speculate is a result of suppressed wetland macrophyte growth and activity, as well as changes in microbial community composition.

How Spartina alterniflora adapts to a new environment created by embankment reclamation through C-N-P stoichiometry in the coastal wetlands of eastern China

Although embankment reclamation is a recurring activity in the coastal wetlands of China, the effect of embankment construction on plant growth has attracted little attention. Leaf carbon, nitrogen and phosphorus stoichiometry (C-N-P stoichiometry) of a plant can be used to reflect plant adaptation to new environments created by reclamation. In the present study we investigated the biomass and leaf C-N-P stoichiometry of Spartina alterniflora Loisel., soil C-N-P stoichiometry and soil moisture, salinity, bulk density and pH in both embankment-reclaimed and natural S. alterniflora salt marshes in eastern China. Plant biomass, leaf P content, soil salinity and soil moisture were significantly lower in the reclaimed compared with natural marsh. The decrease in leaf P content is possibly attributed to changes in soil salinity, soil moisture and soil organic C and N content in the reclaimed marsh. The results of the present study indicate that the decreased aboveground biomass in the reclaimed marsh is likely to be correlated with an increase in the leaf N:P ratio, in accordance with the ‘growth rate hypothesis’. However, previously published threshold values of the N:P ratio as indicators of N or P limitation of plant growth may not be applicable to S. alterniflora at our study site.

Individual and combined effects of cadmium and polycyclic aromatic hydrocarbons on the phytoremediation potential of Xanthium sibiricum in co-contaminated soil

ABSTRACT Soil contamination with heavy metals and organic pollutants continues to cause major ecological damage and human health problems. Phytoremediation offers a highly promising technology for the recovery of sites contaminated with mixed pollutants. In this study, we performed a greenhouse experiment to investigate the individual and combined effects of cadmium (Cd) and polycyclic aromatic hydrocarbon (PAH) contamination on the growth of Xanthium sibiricum, and also the ability of this species to accumulate and remove Cd and to reduce PAHs over a period of 75 days. Our results demonstrated that individual or combined contamination by Cd and PAHs showed no significant differences to the control treatment except in the high Cd treatment. The reduction of PAH concentration in the soil with the passage of time was similar in the presence or absence of plants. At higher levels of Cd, the removal of pyrene decreased in both planted and non-planted soils; however, this effect might be due to the higher Cd content. Soil dehydrogenase and polyphenol oxidase activities showed that soil contamination did not have a significant effect on the removal of PAHs. Overall, our results suggest that X. sibiricum might be a suitable species for use in the phytoremediation of contaminated soils.

Effects of multiple dams on the metacommunity structure of stream macroinvertebrates

Dams and floodgates have been established to mitigate flood hazards and to satisfy the growing demand for water resources; however, the excessive presence of dams in river ecosystems causes a series of ecological problems. Most previous studies regarding the effects of dams on aquatic community structure have focused on the effects of individual dams on river ecosystems on a local scale, whereas few studies have investigated the combined effects of multiple dams at the basin scale. In the present study we explored the combined effects of multiple dams on macroinvertebrate metacommunity structure and quantified these effects using variation partitioning and asymmetric eigenvector map analysis. We found that the combined effects of multiple dams on macroinvertebrate metacommunity structure are significant, and that the direct effects of dams that limit dispersal were greater than the indirect effects of changing environmental conditions. We also found that spatial variables at medium and fine scales captured more variation in macroinvertebrate metacommunity structure than broad-scale partitioning. Because broad-scale spatial variations are primarily attributed to environmental spatial structuring, and medium- and fine-scale spatial community structures are likely related to neutral processes, it was inferred that the direct effects of dams were greater than the indirect effects.

Effects of long-term coastal reclamation on suitable habitat and wintering population size of the endangered Red-crowned Crane, Grus japonensis

Exploring how suitable habitat and population size of Red-crowned crane Grus japonensis respond to long-term coastal reclamation plays an important role in species conservation and in related coastal management. Here, we combined field data for suitable habitats and wintering population size of G. japonensis with GIS-based information to elucidate the influence of long-term coastal reclamation on this species and related conservation efforts. During 1975–2013, the intensity and spatial extent of coastal reclamation exhibited a temporal change, increasing dramatically in 1975–2000 and lessening considerably in 2000–2013. Under the pressure of long-term coastal reclamation, the decline of suitable habitat of G. japonensis was affected by increasing levels of human disturbance and decreasing availability of natural habitat. Moreover, the wintering population size of G. japonensis exhibited a decreasing trend during 1975–2013 as a result of the decreasing availability of fish ponds, bare tidal flats, and increasing spatial extent of residential areas and P. australis habitat, which were indirectly affected by long-term reclamation. Our results highlight the importance of considering the long-term effects of coastal reclamation on both populations and suitable habitat of G. japonensis, which should be considered in future plans for coastal management and conservation.