Removal And Influential Mechanisms Of Typical Endocrine Disrupting Chemicals By Algae And Algal-based Materials

Endocrine disrupting chemicals?EDCs?are a class of emerging pollutants with relative higher detection frequency in coastal waters of China.EDCs can compete with the normal hormones in body to bind to the receptors after they enter the target cells,thus forming a hormone-receptor complex which interferes with the endogenous hormone levels of humans and animals as well as having many effects on the growth and development of body,the nervous system and the immune system.Importantly,these EDCs can disturb the function of the endocrine system even at very low doses.Increasing inputs from anthropogenic activities,industrial development and natural disasters are exacerbating the potential threat of EDCs to the coastal environments.This study investigated the removal and influential mechanisms of typical endocrine disrupting chemicals by algae and algal-based materials.The spatial distribution,sources and potential risks of EDCs in coastal waters along coastline of China were evaluated.The removal of typical EDCs by harmful green algae and important intertidal algae was investigated,and the influence of different environmental factors on their removal was also evaluated.Additionally,the adsorption-desorption processes of EDCs and corresponding influential factors in the presence of algal detritus deposited in the coastal environment during the outbreak of the green tide were studied through laboratory experiments.A series of algal biomass materials were prepared for the pollution control of EDCs.?1?The pollution of polycyclic aromatic hydrocarbons?PAHs?,phenolic and steroid endocrine disruptors has become a crucial stress affecting the sustainable development of coastal regions.Concentrations of PAHs,phenolic and steroid endocrine disruptors in coastal waters were obtained.Approximately 84%of sampling sites were determined at moderate PAH pollution level and PAHs exerted high cancer risks for children at 31%of sampling sites.Analysis of estrogenic activity of phenolic and steroid endocrine disruptors indicated that the estradiol equivalent?EEQ?,ranging from 9 to 278 ng L^-1,was much higher than that of the relevant ecological safety standards of the European Union(1 ng L^-1).It might have adverse effect on the endocrine disruption of aquatic organisms in the receiving water.?2?The phycoremediation by U.prolifera is an important new natural remediation process for coastal waters contaminated with endocrine disrupting chemicals during green tide blooming.The removal efficiency of three pollutants by green tide algae was NP?97.4%?>BAP?94.3%?>Phe?92.0%?,and the removal process included several mechanisms depending on different pollutants.The removal of Phe and NP was mainly involved in abiotic factors such as algae absorption,algae adsorption,microbial degradation and abiotic factors,while the removal of BPA was mainly involved in the combination of algae absorption and microbial degradation.The differences in their degradation mechanisms were mainly related to the physical and chemical properties of the pollutants.The concentration of target pollutants in the green tide blooming zone was much lower than that in the adjacent zone without green tide.?3?As the typical intertidal algae,Ulva pertusa was of great importance in the coastal zone for BPA and NP phytoremediation,and the removal efficiency of NP?97.4%?was higher than BAP?94.3%?.Although the removal efficiency by Ulva pertusa is lower than that of green tide algae,its contribution to pollutants removal is still of great importance.The removal mechanisms of NP and BPA were mainly involved in abiotic factors,algae surface adsorption,algae absorption and microbial action.?4?Batch experiments showed that algal induced photolysis process and algal-bacterial processes were two important mechanisms for the removal of EDCs by algae.In the algal induced photolysis process,the light could enhance the removal efficiency of BPA by 46%and lead to the formation of two photolysis products.In the algal-bacterial system,the epiphytic bacteria on the surface of the algae were successfully isolated.OTU cluster analysis and species taxonomic analysis showed that the epiphytic bacteria were mainly compromised by Bacillus,Exiguobacterium,Fictibacillus and Brevibacillus.Moreover,the Bacillus was the most abundant among the epiphytic bacteria.The Bacillus bacteria were well kown for EDCs removal,which confirmed the engagement of both the algae and the epiphytic bacteria in algal-bacterial system.?5?The decomposition of harmful green tide algae could provide a new natural remediation approach for PAHs in the coastal environment through the adsorptive removal by the detritus of green tidal algae deposited in the coastal environment.The presence of algal detritus deposited in the coastal environment during the outbreak of the green tide showed fast adsorption removal efficiency for naphthene?Naph?,phenanthrene?Phe?and benzo[a]pyrene?Ba P?,and the removal efficiency increased with the ring numbers of PAHs.Simultaneously,lipid was confirmed to be one of the important factors for PAHs adsoptive removal by detritus.A good linear relationship?R²?0.99?between the removal efficiency of PAHs and the initial concentration of PAHs was observed.Slow desorption kinetics and low desorption rate?<16%?indicated that the adsorptive PAHs were trapped tightly on the detritus.?6?Two novel methods were develpted to achieve high value utilization of algal biomass.The Ulva prolifera-based biochar?AC?with N content of 2.6%and the sulfide-modified biochar supported zero-valent iron?S-n ZVI/AC?were synthesized through a rapid hydrothermal carbonization process and characterized by scanning electron microscopy-energy spectroscopy?SEM-EDS?and infrared spectroscopy?FT-IR?.The Ulva prolifera-based biochar?AC?was applied to the adsorptive removal of bisphenol A?BPA?.More than 90%of BPA was removed within 4 hours,and the adsorption process followed the pseudo second-order kinetic model.The sulfide-modified biochar supported zero-valent iron was applied to the removal of tetrabromobisphenol A?TBBPA?.It was found that the removal efficiencu of TBBPA in S-n ZVI/AC system was 84%within 24 h,while in the AC system was just 58%,confirming that the sulfide-modified algae-based biochar is a novel material for TBBPA removal.Additionally,four TBBPA reduction products including tribromobisphenol A,dibromobisphenol A,monobromobisphenol A and bisphenol A were detected in the S-n ZVI/AC system,indicating in-situ TBBPA degradation on S-n ZVI/AC.Combined with the results of the cycle experiment,the sulfide-modified biochar supported zero-valent iron material exhibited better removal performance than Ulva prolifera-based biochar materials,and possessed broad application prospects for the pollution control of EDCs.The innovative points of this dissertation were shown as follows:?1?The removal of typical EDCs by macroalgae was studied,and its potential for removing pollutants in large-scale area was confirmed.The attenuation process of EDCs in the coastal waters under the conditions of algae expansion was found as a new drive mechanism.Additionaly,the in-situ enhanced removal mechanism of this type of pollutants by macroalgae in coastal and near coastal ecological restoration projects was clarified.The results can provide a theoretical basis and technical support for understanding the attenuation process and remediation of EDCs in coastal waters.?2?The N-doped carbon adsorbent and the sulfide-modified biochar supported zero-valent iron composites were prepared by the rapid hydrothermal carbonization process and the‘one-pot synthesis method',respectively.The results could provide high value-added reutilization approaches for waste biomass materials.