In response to issues such as low reduction rate(70％-80％)and poor linearity of the standard curve in the traditional zinc-cadmium reduction method for determining nitrate in seawater,this study investigated the effects of key conditions including electrolyte(CdCl2)concentration,vortex shaking frequency,shaking time,and post-reaction standing time on the reduction rate.The results show that as the concentration of CdCl2 electrolyte increases,the nitrate reduction rate follows a parabolic trend,A concentration of 4 g/L CdCl2 electrolyte served as the turning point for nitrate reduction,achieving a reduction efficiency exceeding 90％.When the CdCl2 concentration exceeded 4 g/L,the nitrate reduction product nitrite can be further reduced to lower-valence compounds,leading to loss.The highest and most stable nitrate reduction efficiency is achieved under the following conditions:shaking frequency of 1400 r/min,shaking time of 13 min,post-shaking standing time≤5 min,and salinity>5 g/L.The improved method demonstrates a detection limit of 0.023 μmol/L,a relative standard deviation(RSD)<5％,and a spike recovery rate ranging from 95.9％to 103.6％.Comparative analysis shows that the vortex shaking method significantly outperforms the traditional method in terms of linearity,sensitivity,and reduction rate.Accordingly,this study establishes an optimized detection protocol,providing reliable technical support for seawater nitrate determination and offering significant application value for marine environmental monitoring.
Climate policies play a pivotal role in climate change mitigation and adaptation.However,policy formulation and implementation face structural constraints such as administrative jurisdictional barriers and conflicting sectoral interests,while existing evaluation systems exhibit deficiencies including insufficient model precision and limited practical guidance.Targeting Zhejiang Province's marine carbon sink policies—a model integrating economic vitality with ecological leadership,this study employs the S-CAD policy evaluation framework to systematically assess the attainability of core policy propositions and their implementation performance.The study finds that while the policy demonstrates a clear core stance and high implementation efficiency,there is room for optimization in the transmission and synergy mechanisms of its policy chain.Four multidimensional optimization pathways are proposed:establishing nonlinear policy mechanisms with precision-tailored interventions,synchronizing conceptual elevation with institutional breakthroughs,consolidating policy elements to reduce implementation deviations,and enhancing policy resilience across extended temporal and broad spatial scales.The findings provide theoretical references for climate policy formulation at all governmental levels in China,while contributing management paradigms and scientific underpinnings to global efforts toward achieving the UN Sustainable Development Goals.
Polycyclic aromatic hydrocarbons and their derivatives are typical persistent toxic substances.Learning their occurrence,seasonal and diurnal variation of gas-particle partitioning can provide a more comprehensive understanding of their environmental behavior and inhalation risk.In this work,parent polycyclic aromatic hydrocarbons(P-PAHs),alkylated PAHs(A-PAHs)and nitrated PAHs(N-PAHs)in the atmosphere of typical coastal city in northern China were collected,and occurrence,pollution sources,gas-particle partitioning and inhalation risk assessment were systematically carried out.The results showed that the three types of PAHs concentrations present a trend of P-PAHs>A-PAHs>N-PAHs overall.The particle concentrations in summer(6.44 ng/m3,1.61 ng/m3 and 0.17 ng/m3,respectively)were significantly lower than those in winter(44.06 ng/m3,26.41 ng/m3 and 2.79 ng/m3,respectively).There was a significant seasonal variation of three types of PAHs in gas phase.The P-PAHs concentrations in summer were higher than those of A-PAHs and N-PAHs,whereas the A-PAHs and N-PAHs in gas phase were significantly higher than those of P-PAHs in winter.The diurnal comparison of three types PAHs showed that the gaseous concentrations of N-PAHs during the daytime in summer were significantly higher than those at night,while the particle concentrations of A-PAHs and N-PAHs at night in winter were slightly higher than those during the daytime.The source analysis between summer and winter showed that the contribution of oil source at night(48.20％)was significantly higher than that at daytime(36.98％)in summer due to the influence of temperature and port operations.Similarly,the proportion of biomass source at night(36.69％)was significantly higher than that at daytime(28.13％)in summer due to the influence of barbecue behaviors.The gas-particle partitioning results indicated that the fittings of the J-P model and the H-B model for PAHs and their derivatives were more suitable than that of the L-M-Y model,and the slopes of the J-P and H-B models in winter were significantly higher than those in summer.However,the diurnal variation of three models were not obvious.The results of the inhalation health risk assessment indicated that the lifetime carcinogenic risk in the Dalian area showed no significant diurnal variation.whereas the seasonal fluctuation was considerable.The probabilistic cancer risk during winter exceeded the acceptable threshold set by the U.S.Environmental Protection Agency.
The morphological evolution of Nanhui tidal flat and main driving factors has been analyzed with the Landsat-8/9 and Sentinel-2 Satellites the Digital Elevation Models(DEMs)data from 2017 to 2022.The eastern Nanhui tidal flat is silting flat with its area increasing by 66.96%(from 64.67 km2 to 107.97 km2)in five years and the largest seaward extend rate is about 521.11 m/a due to the dike project.The southern Nanhui tidal flat shows coastline retreat and bed erosion pattern with its area decreasing by 22.06%(from 2.04 km2 to 1.59 km2).Seasonal variability of the eastern Nanhui tidal flat is characterized as significantly retreated and seaward extend of shorelines driven by typhoon in summer and autumn,and seaward extension of shoreline inside the embanked area caused by weak hydrodynamic conditions driven the coast transport and accumulation of sand during winter and spring.This study provided evidences for understanding tidal-flat evolution driven by the combined effects of climate change and human activities.
In October 2021,a survey was conducted at 12 subtidal stations and 3 intertidal stations in the Minjiang Estuary.The results indicated that:(1)17 macrobenthic species were collected in the subtidal zone,with polychaetes(10 species)as the dominant group.The average density was 60.0 ind./m2 and the average biomass was 1.12 g/m2.Byblis sp.,Heteromastus filiformis,and Sigambra bassi were dominant species commonly found in both nearshore and offshore subtidal areas.(2)22 macrobenthic species were collected in the intertidal zone,dominated by crustaceans(12 species).The average density was 59.5 ind./m2 and the average biomass was 17.49 g/m2.Uca arcuata was a dominant species across the high,middle,and low tide zones.(3)The C2 station might be moderately disturbed,while the remaining stations appeared undisturbed.(4)In the subtidal zone,polychaetes were influenced by Hg and carbon content,while crustaceans were affected by Cd,Cr,and oil pollutants.Among water quality parameters,NO3-,TSS,and NO2-,and among sedimentary parameters,Zn,As,and Pb were identified as key factors influencing community metrics.The subtidal sediments were predominantly sandy,and macrobenthic organisms exhibited a trend toward smaller body sizes.In the intertidal zone,diversity was higher in the middle and high tide zones than in the low tide zone.The heterogeneity of sediment composition due to differences in grain size may be a primary factor affecting the distribution of macrobenthic fauna in this region.
Oil spill poses a severe threat to the health of marine environments and ecosystems.Efficient monitoring technologies are crucial for mitigating the impacts of oil spill accidents and formulating emergency response strategies.Addressing the issue of traditional marine radar monitoring methods being susceptible to noise interference,this study proposes a monitoring method that integrates a hybrid strategy of multi-dimensional feature clustering and an improved mantis shrimp optimization algorithm(MShOA).This method achieves efficient oil slick segmentation through the generation of multi-dimensional features,K-Means clustering,and MShOA intelligent optimization search.The improved MShOA introduces dynamic inertia weights and a Gaussian perturbation mechanism to enhance its optimization search capabilities.Experimental results demonstrated that this method exhibited strong robustness in marine radar oil spill detection,providing a reliable solution for offshore oil spill monitoring.
Based on the field survey in the Hangzhou Bay-Yangtze Estuary in September 2022,dissolved methane concentration and its sea-to-air flux and related dominant factors were studied.Results showed that dissolved methane concentration ranged from 6.89 to 43.41 nmol/L with an average of(18.58±8.88)nmol/L in surface seawater,and from 8.88 to 36.15 nmol/L with an average of(8.25±89.34)nmol/L in bottom seawater,respectively.Dissolved methane concentration was higher in the Yangtze Estuary and Hangzhou Bay than in the offshore area,indicating that freshwater input from local sediment played an important role in methane sources.The average saturation of dissolved methane in surface seawater and its sea-to-air flux was(275.10±6.70)％and(157.40±145.68)μmol/(m2·d),respectively,suggesting the survey area was a net source of atmospheric methane.Annual methane of emission was estimated to be approximately 1.78×109 mol,accounting for about 0.16％of the global annual oceanic methane emission,which caused an average elevation of 3.2 nmol/mol methane in the boundary air of survey area.
With the increasing utilization of nuclear energy,potential risks of nuclear accidents,and discharges of radioactive waste,marine radiological monitoring and anomaly identification have become crucial tasks for nuclear safety assurance and ecological environmental protection.This paper systematically reviews the criteria,technical methodologies,and practical cases for identifying anomalies in the marine radiological environment.It focuses on threshold setting,data analysis techniques,and assessment procedures under relevant international and domestic standards.In the context of insufficiently established standards and criteria for anomaly identification,the Background Range Method,Spatio-Temporal Trend Analysis,and Isotopic Fingerprint/Ratio Method have emerged as the primary technical guidelines for current anomaly detection.Applications are illustrated through monitoring and evaluation practices in the waters near Fukushima and Daya Bay,highlighting the differences in anomaly characteristics,identification techniques,and management responses under both nuclear accident conditions and normal operation of nuclear facilities.Furthermore,the paper proposes recommendations for advancing marine radiological monitoring and anomaly identification,aiming to provide a theoretical foundation for the formulation and revision of national standards and industrial guidelines,to provide a scientific basis for safeguarding marine nuclear safety and managing radiological risks in the marine environment.
