Biogenic silica in intertidal marsh plants and associated sediments of the Yangtze Estuary

Biogenic silica （BSi） contents in the marsh plants （Phragmites australis, Scirpus mariqueter and Spartina alterniflora） and associated sediments in Chongming Island eastern intertidal flat of the Yangtze Estuary were determined. The BSi contents in P. australis, S. mariqueter and S. alterniflora varied from 25.78–42.74 mg/g, 5.71–19.53 mg/g and 6.71–8.92 mg/g, respectively. Over the entire growth season, P. australis and S. mariqueter were characterized by linear accumulation patterns of BSi. The aboveground biomass （leaves and culms） of the marsh plants generally contained more BSi than underground biomass （roots）. BSi contents were relatively higher in dead plant tissues than in live tissues which was probably due to the decomposition and the leaching of labile components of plant tissues such as organic carbon and nitrogen. Comparing with the habitats of S. mariqueter and S. alterniflora, the highest BSi content was recorded in sediments inhabited by P. australis, with an annual average of 15.69 mg/g. Overall, the intertidal marshes in the Yangtze Estuary may act as a net sink of BSi via plant uptake and sedimentary burial.

黄河口几种盐沼植物对滨海湿地净化作用的研究(英文)

The paper compared the differences between above ground and underground biomass of four types of plants.The heavy metals(Cu,Zn,Cd,Cr,Pb,As,Hg)and nutrients(TN,TP)content in tissues of four maturity plants were detected,and their enrichment coefficient and transfer coefficient were calculated.The results showed that Suaeda salsa had the largest concentrated capacity on Cu,Zn,Pb,As and Phragmites australis was larger on the Cd,Hg than other plants.Considering the purification of four plants,the effect on the restoration of heavy metal pollution was better if we harvested Phragmites australis and Suaeda salsa.Four plants had a larger difference in absorption capacity of nitrogen and smaller absorption of phosphorus.Phosphorus uptake was significantly smaller than nitrogen.Harvesting Phragmites australis and Suaeda salsa can reduce total nitrogen and phosphorus content of the wetland,while harvesting Spartina alterniflora and Typha orientalis can reduce total phosphorus content.

Performance of a subsurface-flow constructed wetland in Southern China

The operational performance of a full scale subsurface flow constructed wetland, which treated the mixed industrial and domestic wastewater with BOD 5/COD mean ratio of 0 33 at Shatian, Shenzhen City was studied. The constructed wetland system consists of screens, sump, pumping station, and primary settling basin, facultative pond, first stage wetland and secondary stage wetland. The designed treatment capacity is 5000 m 3/d, and the actual influent flow is in the range of <2000 to >10000 m 3/d. Under normal operational conditions, the final effluent quality well met the National Integrated Wastewater Discharge Standard(GB 8978\_1996), with the following parameters(mean values): COD 33 90 mg/L, BOD 5 7.65 mg/L, TSS 7.92 mg/L, TN 9.11 mg/L and TP 0 56 mg/L. Seven species of plants were selected to grow in the wetland: Reed, Sweetcane flower Silvergrass, Great Bulrush, Powdery Thalia and Canna of three colours. The growing season is a whole year round. The seasonal discrepancy could be observed and the plants growing in the wetland are vulnerable to lower temperature in winter. The recycling of the effluent in the first stage of the wetland system is an effective measure to improve the performance of the wetland system. The insufficient DO value in the wetland system not only had significant effect on pollutants removal in the wetland, but also was unfavourable to plant growth. The recycling of effluent to the inlet of wetland system and artificial pond to increase DO value of influent to the wetland is key to operate the subsurface constructed wetland steadily and effectively.

Invasive Spartina alterniflora accelerates the increase in microbial nitrogen fixation over nitrogen removal in coastal wetlands of China

Salt marsh plants play a vital role in mediating nitrogen(N)biogeochemical cycle in estuarine and coastal ecosystems.However,the effects of invasive Spartina alterniflora on N fixation and removal,as well as how these two processes balance to determine the N budget,remain unclear.Here,simultaneous quantifications of N fixation and removal via^(15)N tracing experiment with native Phragmites australis,invasive S.alterniflora,and bare flats as well as corresponding functional gene abundance by qPCR were carried out to explore the response of N dynamics to S.alterniflora invasion.Our results showed that N fixation and removal rates ranged from 0.77±0.08 to 16.12±1.13 nmol/(g·h)and from 1.42±0.14 to 16.35±1.10 nmol/(g·h),respectively,and invasive S.alterniflora generally facilitated the two processes rates.Based on the difference between N removal and fixation rates,net N_(2)fluxes were estimated in the range of-0.39±0.14 to 8.24±2.23 nmol/(g·h).Estimated net N_(2)fluxes in S.alterniflora stands were lower than those in bare flats and P.australis stands,indicating that the increase in N removal caused by S.alterniflora invasion may be more than offset by N fixation process.Random forest analysis revealed that functional microorganisms were the most important factor associated with the corresponding N transformation process.Overall,our results highlight the importance of N fixation in evaluating N budget of estuarine and coastal wetlands,providing valuable insights into the ecological effect of S.alterniflora invasion.