Characterization of dissolved organic matter in submarine groundwater from a salt marsh in Chongming Island,China

Salt marshes are research hotspots of the carbon cycle in coastal zones because large amounts of atmospheric carbon dioxide is fi xed by salt marshes vegetation and stored in its biomass and soil.Dissolved organic carbon(DOC)in submarine groundwater(well water and pore water)in salt marshes plays an important role in advective exchange between the salt marshes and coastal waters.However,the molecular characteristics of DOC in salt marsh groundwater are poorly understood because of the complex DOC structures and hydrodynamic process.In this study,fl uorescent components and refractory DOC(RDOC)in submarine groundwater from a salt marsh(Chongming Island,China)and adjacent coastal water were characterized by fl uorescence spectroscopy and nuclear magnetic resonance spectroscopy.The fl uorescent components identifi ed by parallel factor analysis indicated that humic-like substances dominated the chromophoric dissolved organic matter in the submarine groundwater.The chromophoric dissolved organic matter and dissolved organic matter in the submarine groundwater had non-conservative behaviors because of additions from terrestrial humic substances.The nuclear magnetic resonance spectra indicated that bioactive substances(carbohydrates)contributed only 13.2%-14.8%of the dissolved organic matter in the submarine groundwater but carboxyl-rich alicyclic molecules(CRAMs),the main components of RDOC,contributed 64.5%of the dissolved organic matter.Carbohydrates and CRAMs contributed 16.4%and 61.7%of the dissolved organic matter in the coastal water,similar to the contributions for submarine groundwater.The DOC concentration in submarine groundwater was 386±294μmol/L,which was signifi cantly higher than that in coastal water(91±19μmol/L).The high DOC concentrations and>60%relative RDOC content suggested that submarine groundwater may be an important source of RDOC to coastal seawater.This information will be helpful for estimating the climate eff ects of salt marsh blue carbon.

On eco-planning for an eco-demonstration park (EDP) and sustainability-Case study of the Luhua EDP in the Chongming Island of Shanghai,China

Thebackground,concept,connotation,principles,andmethodsofeco-planningforanEco-Demonstration Park(EDP)and sustainability were examined based on a case study of the Luhua EDP in the Chongming Island of Shanghai,China,which is an important part of Shanghai Eco-city planning and construction in the 21st century.By analyzing natural,social and economic conditions,calculating population using the land capacity eco-model,eco-function zoning,and eco-construction,an innovative eco-industrial structure and technical chain were formulated.A comprehensive eco-planning scheme for the EDP was proposed,including planning and management strategies for subsystems of efficient industry,good quality human settlement,high standard eco-construction and eco-tourism as well as effective environmental protection and attractive landscape.The EDP should be an area with coordinated and sustainable economic,social and environmental subsystems.Eco-planning for the EDP should be a very important part of eco-city planning and sustainability.The paper aims to set up a theoretical framework and practical basis for eco-planning and promoting harmony between human and nature.

Spatial and seasonal pattern of macrozoobenthic assemblages and the congruence in water quality bioassessment using different taxa in artificial Mingzhu Lake in Shanghai

The spatial and seasonal pattern of macrozoobenthic structure and its relationship with environmental factors were studied from July 2006 to April 2008 in Mingzhu Lake,Chongming Island,Shanghai at the Changjiang River mouth.The congruences in water quality bioassessment based on diversity and biotic indices and using different taxonomic categories were also explored to find the best assessment method of water quality for the lake.All major structural characteristics of macrozoobenthic community,including species composition,abundance,biomass and four biomass-based diversity indices(Shannon's diversity,Simpson's diversity,Pielou's evenness and Simpson's evenness index) fluctuated significantly in season but in space.The above four abundance-based diversity indices plus abundance-based Margalef's richness index did not display significant spatial variations;and significant seasonal differences were found in three indices only.Water temperature was the key environmental factor responsible for macrozoobenthic spatio-temporal distribution patterns.Water quality assessed by Shannon's index(H_a') and biological pollution index(BPI) rather than the other four biotic indices were consistent with those by trophic state index(TSI).Results from chironomids and oligochaetes did not always agree to those from the whole community when H_a' or Hilsenhoff biotic index was applied to bioassessment.Therefore,combining multiple indices and avoiding a single taxonomic category to assess water quality are strongly recommended and in Mingzhu Lake using a mixture of H_a' and BPI will ensure the most effective investigation of water quality.Our results also show that the main structural characteristics of macrozoobenthic communities in the small lake may display consistent spatial patterns.

Changes in soil carbon sequestration and soil respiration following afforestation on paddy fields in north subtropical China

Aims Although many studies have reported net gains of soil organic carbon(SOC)after afforestation on croplands,this is uncertain for Chinese paddy rice croplands.Here,we aimed to evaluate the effects of affores-tation of paddy rice croplands on SOC sequestration and soil respiration(R).Such knowledge would improve our understanding of the efctive-ness of various land use options on greenhouse gas mitigation in China.Methods The investigation was conducted on the Chongming Island,north subtropical China.Field sites were reclaimed from coastal salt marshes in the 1960s,and soils were homogeneous with simple land use:histories.SOC stocks and R,levels were monitored over one year in a paddy rice cropland,an evergreen and a deciduous broad-leaved plantation established on previous paddy fields and a reference fal-low land site never cultivated.Laboratory incubation of soil under fast-changing temperatures was used to compare the temperature sensitivity(Q10)of SOC decomposition across land uses.Important Findings After 15-20 years of afforestation on paddy fields,SOC concentra-tion only slightly increased at the depth of 0--5 cm but decreased in deeper layers,which resulted in a net loss of SOC stock in the top 40cm.Seasonal increase of sOC was observed during the rice-growing period in croplands but not in afforested soils,suggest-ing a stronger SOC sequestration by paddy rice cropping.However,SOC sequestered under cropping was more labile,as indicated by its higher contents of dissolved organic carbon and microbial bio-mass.Also,paddy soils had higher annual R,than afforested soils;R,abruptly increased after paddy fields were drained and plowed and remained distinctively high throughout the dry farming period.Laboratory incubation revealed that paddy soils had a much higher Q10 of SOC decomposition than afforested soils.Given that tem-perature was the primary controller of R,in this region,it was con-cluded that despite the stronger SOC sequestration by paddy rice cropping,its SOC was less stable than in afforested systems and might be more easily released into the atmosphere under global warming.