Optimization of Sample Pretreatment for Determination of Polycyclic Aromatic Hydrocarbons in Estuarine Sediments by Gas Chromatography

This study examined levels of polycyclic aromatic hydrocarbons (PAHs) in estuarine sediments in Licun (Qingdao, China) by gas chromatography under optimized conditions for sample pretreatment via ultrasonic extraction, column chromatography, and thin layer chromatography. Methanol and dichloromethane (DCM)/methanol (2:1, v/v) were used in ultrasonic extraction, and DCM was used as eluate for column chromatography. The developing system consisted of n-hexane and DCM at a ratio of 9:1 (v/v), with DCM as the extraction solvent for PAHs-containing silica gel scraped off the plate. When the spiking level is 100 ng, total recoveries of spiked matrices for four target PAHs (phenanthrene, anthracene, pyrene and chrysene) were 83.7%, 76.4%, 85.8%, and 88.7%, respectively, with relative standard deviation (RSD) between 5.0% and 6.5% (n = 4). When the spiking level is 1000 ng, associated total recoveries were 78.6%, 72.7%, 82.7% and 85.3%, respectively, with RSD between 4.4% and 5.3% (n = 4). The opti-mized method was advantageous for determination of PAHs in complex matrix due to its effective sample purification.

Impact of Phenanthrene on Denitrification Activity and Transcription of Related Functional Genes in Estuarine and Marine Sediments

The effects of phenanthrene(Phe)on the denitrification activity and denitrifying genes(narG,nirS and nosZ)were evaluated by dose-response experiments in sediments of Dagu River Estuary(DRE)and Jiaozhou Bay(JZB).The results showed that potential denitrification activity(PDA),N2O,NO3−and NO2−reduction rates of both areas were inhibited with an increase of Phe concentrations.The PDA,N2O,NO3−and NO2−reduction rates of both areas was highest and lowest in the control(DRE:0.453,0.427,7.439 and 3.222mgNkg−1 h−1,JZB:0.592,0.555,8.470 and 3.793mgNkg−1 h−1)and highest Phe amended treatments(DRE:0.069,0.001,4.486,and 1.563 mgNkg−1 h−1;JZB:0.114,0.024,5.527 and 2.200 mgNkg−1 h−1).The inhibition rate of PDA was highest,follow by NO2−reduction and then NO3−reduction.Moreover,with the increasing of Phe concentrations,total bacteria count and the abundance of denitrifying genes were decreased.And N2O accumulation was promoted with the addition of Phe for both areas.Based on the comparison of EC50 values,denitrifiers harboring three genes were more sensitive to Phe than PDA,and denitrifiers harboring nirS gene were more sensitive,followed by nosZ gene,and then narG gene.Furthermore,according to correlation analysis,the relative abundance of denitrifying genes was much more positively correlated with PDA,NO3−and NO2−reduction than total bacteria count.In addition,the denitrification activity and total bacteria count in JZB were more inhibited than that of DRE.This study is useful for understanding the impact of Phe pollution on denitrification in estuary and marine sediments,with profound implications for the management of aquatic ecosystems regarding eutrophication(N-removal)and greenhouse effect.

Suspended sediment concentration mapping based on the MODIS satellite imagery in the East China inland, estuarine, and coastal waters

The purpose of this research is to improve the retrieval accuracy for the suspended sediment concentration(SSC) from in situ and satellite remote sensing measurements in turbid East China estuarine and coastal waters. For this aim, three important tasks are formulated and solved: 1) an estimation of remote-sensing reflectance spectra R_(rs)(λ) after atmospheric correction; 2) an estimation of R_(rs)(λ) from the radiometric signals above the air-water surface; and 3) an estimation of SSC from R_(rs)(λ). Six different models for radiometric R_(rs)(λ) determination and 28 models for SSC versus R_(rs)(λ) are analyzed based on the field observations made in the Changjiang River estuary and its adjacent coastal area. The SSC images based on the above-mentioned analysis are generated for the area.

Effects of Silver Nanoparticles on Denitrification and Associated N_(2)O Release in Estuarine and Marine Sediments

Silver nanoparticles(AgNPs)have been widely used in medicine and consumer products.And it enters the river in dif-ferent ways,then finally converges to the ocean through the estuary.AgNPs polution can affect NO_(2)−and N_(2)O production by denitri-fiers in aquatic system.The effects of AgNPs on denitrification activity,nitrogen transformation and nitrous oxide(N_(2)O)emission were investigated in Dagu River Estuary(DRE)and Jiaozhou Bay(JZB).The results showed that the potential denitrification activity(PDA),NO_(3)−and NO_(2)−reduction rates decreased with an increase of AgNPs concentration in DRE and JZB.However,the N_(2)O ac-cumulation was significantly increased at AgNPs concentrations above 5 mg kg^(−1)in both areas,and the accumulation rate was greater in estuary than in bay(P<0.05).Moreover,the total bacterial count showed a slightly increasing trend with an increase of AgNPs concentration(P>0.05)in DRE and JZB.Importantly,the relative abundance of narG,nirS and nosZ gene in two areas decreased with the increase of AgNPs concentration,and the negative effect of AgNPs varied in order:nosZ>nirS>narG,inferring that the expression of denitrifying related genes could be significantly and differently inhibited by AgNPs addition.Thus,this study demon-strated that the inhibitory effect of AgNPs on different denitrification process,which may lead to the increase of inorganic nitrogen accumulation and N_(2)O realease.This study provides a scientific basis for the further studies of AgNPs on the ecological impact mechanism and environmental effects of offshore sedimentary environment.