Landscape ecological risk assessment and its driving factors in the Weihe River basin,China

Weihe River basin is of great significance to analyze the changes of land use pattern and landscape ecological risk and to improve the ecological basis of regional development.Based on land use data of the Weihe River basin in 2000,2010,and 2020,with the support of Aeronautical Reconnaissance Coverage Geographic Information System(ArcGIS),GeoDa,and other technologies,this study analyzed the spatial-temporal characteristics and driving factors of land use pattern and landscape ecological risk.Results showed that land use structure of the Weihe River basin has changed significantly,with the decrease of cropland and the increase of forest land and construction land.In the past 20 a,cropland has decreased by 7347.70 km2,and cropland was mainly converted into forest land,grassland,and construction land.The fragmentation and dispersion of ecological landscape pattern in the Weihe River basin were improved,and land use pattern became more concentrated.Meanwhile,landscape ecological risk of the Weihe River basin has been improved.Severe landscape ecological risk area decreased by 19,177.87 km2,high landscape ecological risk area decreased by 3904.35 km2,and moderate and low landscape ecological risk areas continued to increase.It is worth noting that landscape ecological risks in the upper reaches of the Weihe River basin are still relatively serious,especially in the contiguous areas of high ecological risk,such as Tianshui,Pingliang,Dingxi areas and some areas of Ningxia Hui Autonomous Region.Landscape ecological risk showed obvious spatial dependence,and high ecological risk area was concentrated.Among the driving factors,population density,precipitation,normalized difference vegetation index(NDVI),and their interactions are the most important factors affecting the landscape ecological risk of the Weihe River basin.The findings significantly contribute to our understanding of the ecological dynamics in the Weihe River basin,providing crucial insights for sustainable management in the region.

A novel framework of ecological risk management for urban development in ecologically fragile regions: A case study of Turpan City, China

Assessing and managing ecological risks in ecologically fragile areas remain challenging at present.To get to know the ecological risk situation in Turpan City,China,this study constructed an ecological risk evaluation system to obtain the ecological risk level(ERL)and ecological risk index(ERI)based on the multi-objective linear programming-patch generation land use simulation(MOP-PLUS)model,analyzed the changes in land use and ecological risk in Turpan City from 2000 to 2020,and predicted the land use and ecological risk in 2030 under four different scenarios(business as usual(BAU),rapid economic development(RED),ecological protection priority(EPP),and eco-economic equilibrium,(EEB)).The results showed that the conversion of land use from 2000 to 2030 was mainly between unused land and the other land use types.The ERL of unused land was the highest among all the land use types.The ecological risk increased sharply from 2000 to 2010 and then decreased from 2010 to 2020.According to the value of ERI,we divided the ecological risk into seven levels by natural breakpoint method;the higher the level,the higher the ecological risk.For the four scenarios in 2030,under the EPP scenario,the area at VII level was zero,while the area at VII level reached the largest under the RED scenario.Comparing with 2020,the areas at I and II levels increased under the BAU,EPP,and EEB scenarios,while decreased under the RED scenario.The spatial distributions of ecological risk of BAU and EEB scenarios were similar,but the areas at I and II levels were larger and the areas at V and VI levels were smaller under the EEB scenario than under the BAU scenario.Therefore,the EEB scenario was the optimal development route for Turpan City.In addition,the results of spatial autocorrelation showed that the large area of unused land was the main reason affecting the spatial pattern of ecological risk under different scenarios.According to Geodetector,the dominant driving factors of ecological risk were gross domestic product rating(GDPR),soil type,population,temperature,and distance from riverbed(DFRD).The interaction between driving factor pairs amplified their influence on ecological risk.This research would help explore the low ecological risk development path for urban construction in the future.

Spatial distribution and potential ecological and health risks associated with heavy metals in the Ijero-Ekiti mining site,Nigeria

Artisanal gold mining,a labor-intensive and antiquated technique,is a growing industry and the source of income for rural communities all over the world.However,artisanal gold mining has potential negative and long-term effects on economy,environment,and society.This study collected soil samples from 16 sample points including a control point to examine the pollution degrees and spatial distribution of heavy metals,as well as ecological and health risks associated with heavy metal pollution in the Ijero-Ekiti mining site,Nigeria.Geographical Information System(GIS)and remote sensing technologies were used to identify regions with high concentrations of heavy metals and assess the environmental impact of gold mining activities.The results show that the mean heavy metal concentrations of 16 soil pointa are 8.94(±5.97)mg/kg for As,0.18(±0.54)mg/kg for Cd,0.11(±1.06)mg/kg for Co,14.32(±3.43)mg/kg for Cr,6.89(±0.64)mg/kg for Cu,48.92(±11.77)mg/kg for Fe,135.81(±30.75)mg/kg for Mn,5.92(±0.96)mg/kg for Ni,5.72(±1.66)mg/kg for Pb,and 13.94(±1.38)mg/kg for Zn.The study reveals that heavy metal concentration in soils follows the order of Mn>Fe>Cr>Zn>As>Cu>Ni>Pb>Co>Cd.An analysis of soil samples indicates that 3 principal components(PCs)account for 70.008%of the total variance and there are strong positive correlations between various pairs of heavy metals.The total potential ecological risk index(309.599)in the study area is high.Non-carcinogenic risk suggests that there may be long-term health impacts on people who work in the mining areas due to chronic exposure to the environment.Based on the study,the hazard index of carcinogenic health risks associated with heavy metals through ingestion is 520.00×10^(–4).Dermal contact from As and Cr also increases the risk of cancer,with the highest hazard index value of 18.40×10^(–4).The lowest exposure pathway,with the hazard index value of 0.68×10^(–4),indicates that the inhalation of heavy metals has a comparatively low risk of cancer.This study recommends the formulation of policies to monitor the Ijero-Ekiti mining site and other regions in Nigeria where indiscriminate artisanal gold mining activities exist.

Spatio-temporal Evolution and Optimization of Landscape Ecological Risk in Karst Mountainous Areas

[Objective]The ecological vulnerability and landscape ecological risk of karst mountainous areas have increased as a result of enhanced disturbance of natural resources by human activities.This paper aimed to explore the characteristics of ecological risk evolution under different landscape patterns in the region,with a view to providing reference for land classification protection,sustainable use of resources and regional ecological risk optimization in karst mountainous areas.[Method]Taking Huangping County,a typical karst mountainous area,as an example,eight evaluation factors of natural and landscape patterns were selected to construct a landscape ecological risk evaluation model,to quantitatively explore the spatio-temporal evolution of landscape ecological risk and the trend of risk level transfer in the study area from^(2)010-2018,and to reveal the complex relationship between ecological risk and topography in karst mountainous areas.[Result]①From 2010 to 2018,land use types changed to different degrees,with the most amount of woodland transferred out(1627.37 hm^(2))and the most amount of construction land transferred in(1303.93 hm^(2));a total of 3552.31 hm^(2) of land was transferred,with a change ratio of 2.13%,and there was a significant conversion between construction land,arable land,and woodland.②From 2010 to 2018,the landscape ecological risk in the study area changed significantly,and the landscape ecological risk index decreased from 0.3441 to 0.1733,showing an upward and then downward trend;the landscape ecological risk of the whole region was dominated by low-risk and lower-risk zones,and the ecological risk level generally shifted from a high level to a low level,and the ecological environment was improved.③There was a negative correlation between ecological risk and topographic position,and high-risk zones were mainly distributed among low topographic zones;with the change of time,the advantage of risk level for the selection of topography was gradually weakened,and the influence of anthropogenic factors on the ecological risk of the landscape was becoming more and more prominent.[Conclusion]This paper can provide theoretical basis for land use optimization and ecological protection in karst mountainous areas.

Influencing Factors and Prediction of Risk of Returning to Ecological Poverty in Liupan Mountain Region,China

China has resolved its overall regional poverty in 2020 by attaining moderate societal prosperity.The country has entered a new development stage designed to achieve its second centenary goal.However,ecological fragility and risk susceptibility have increased the risk of returning to ecological poverty.In this paper,the Liupan Mountain Region of China was used as a case study,and the counties were used as the scale to reveal the spatiotempora differentiation and influcing factors of the risk of returning to poverty in study area.The indicator data for returning to ecological poverty from 2011-2020 were collected and summarized in three dimensions:ecological,economic and social.The autoregressive integrated moving average model(ARIMA)time series and exponential smoothing method(ES)were used to predict the multidimensional indicators of returning to ecological poverty for 61 counties(districts)in the Liupan Mountain Region for 2021-2030.The back propagation neural network(BPNN)and geographic information system(GIS)were used to generate the spatial distribution and time variation for the index of the risk of returning to ecological poverty(RREP index).The results show that 1)ecological factors were the main factors in the risk of returning to ecological poverty in Liupan Mountain Region.2)The RREP index for the 61 counties(districts)exhibited a downward trend from 2021-2030.The RREP index declined more in medium-and high-risk areas than in low-risk areas.From 2021 to 2025,the RREP index exhibited a slight downward trend.From 2026 to2030,the RREP index was expected to decline faster,especially from 2029-2030.3)Based on the RREP index,it can be roughly divided into three types,namely,the high-risk areas,the medium-risk areas,and the low-risk areas.The natural resource conditions in lowrisk areas of returning to ecological poverty,were better than those in medium-and high-risk areas.

Ecological risk assessment and early warning of heavy metal cumulation in the soils near the Luanchuan molybdenum polymetallic mine concentration area,Henan Province,central China

The Luanchuan molybdenum polymetallic mine concentration area is rich in mineral resources and has a long history of mining.The environmental impact of long-term mining activities cannot be ignored.It is of great significance to study the ecological risk and the accumulation trends of heavy metals in the soil of mining areas for scientific prevention and control of heavy metal pollution.Taking the Taowanbeigou River Basin in the mine concentration area as the research object,the ecological pollution risk and cumulative effect of heavy metals in the soil of the basin were studied by using the comprehensive pollution index method,potential ecological risk assessment method and geoaccumulation index method.On this basis,the cumulative exceeding years of specific heavy metals were predicted by using the early warning model.The comprehensive potential ecological risk of heavy metals in the soil near the Luanchuan mine concentration area is moderate,and the single element Cd is the main ecological risk factor,with a contribution rate of 53.6%.The overall cumulative degrees of Cu and Pb in the soil are“none-moderate”,Zn and Cd are moderate,Mo has reached an extremely strong cumulative level,Hg,As and Cr risks are not obvious,and the overall cumulative risks order is Mo>Cd>Zn>Cu>Pb>Hg.According to the current accumulation rate and taking the risk screening values for soil contamination of agricultural land as the reference standard,the locations over standard rates of Cu,Zn and Cd will exceed 78%in 90years,and the over standard rate of Pb will reach approximately 57%in 200 years.The cumulative exceeding standard periods of As,Cr and Hg are generally long,which basically indicates that these elements do not pose a significant potential threat to the ecological environment.Mining activities will accelerate the accumulation of heavy metals in soil.With the continuous development of mining activities,the potential pollution risk of heavy metals in the soil of mining areas will also increase.

Marine ecological risk assessment for the herbicide sulfometuron-methyl based on species sensitivity distribution approach

In recent years,herbicide sulfometuron-methyl(SM)has been used to kill the invasive plant Spartina alterniflora in some coastal areas of China,which may lead to the toxic effects on non-target marine organisms.The 96-h median effective concentrations(96-h EC50)of SM on six species of marine microalgae were measured in growth inhibition tests,and were then compared with other published toxicity data,based on which a method of species sensitivity distribution(SSD)was built to estimate the hazardous concentration of SM for 5%of species(HC5)and potentially affected fraction(PAF)for a certain concentration.Results indicate that SM exhibited a high toxicity to two species of green algae(Chlorella pacifica and Dunaliella salina)with a 96-h EC50 of 0.11 and 0.13 mg/L respectively,had a medium toxicity to two species of golden algae(Diacronema viridis and Isochrysis galbana)with a 96-h EC50 of 14.24 and 21.48 mg/L respectively,and showed a low toxicity to two species of diatoms(Skeletonema costatum and Phaeodactylum tricornutum)with a 96-h EC50 of 148.99 and>100 mg/L,respectively.The estimated values of HC5 and the predicted no-effect concentrations(PNEC)for SM were 0.077 and 0.015 mg/L,respectively.According to the current dosage for killing S.alterniflora in tidal flats in Fujian Province,China,SM entering the sea by spraying might cause the acute injury or death of 14%of marine species.This hazard could last for about a month for those sensitive species.Therefore,on the premise of inhibiting the growth of this invasive plant,the dosage of SM should be reduced as much as possible to avoid severe damage to the marine ecosystem.The results provide a valuable information for marine ecological risk assessment on SM and for marine environmental management.

Spatial distribution and ecological risk of heavy metals and their source apportionment in soils from a typical mining area, Inner Mongolia, China

Determining the distributions and sources of heavy metals in soils and assessing ecological risks are fundamental tasks in the control and management of pollution in mining areas.In this study,we selected 244 sampling sites around a typical lead(Pb)and zinc(Zn)mining area in eastern Inner Mongolia Autonomous Region of China and measured the content of six heavy metals,including cuprum(Cu),Zn,Pb,arsenic(As),cadmium(Cd),and chromium(Cr).The ecological risk of heavy metals was comprehensively evaluated using the Geo-accumulation index,Nemerow general pollution index,and potential ecological risk index.The heavy metals were traced using correlation analysis and principal component analysis.The results showed that the highest content of heavy metals was found in 0–5 cm soil layer in the study area.The average content of Zn,As,Pb,Cu,Cr,and Cd was 670,424,235,162,94,and 4 mg/kg,respectively,all exceeding the risk screening value of agricultural soil in China.The areas with high content of soil heavy metals were mainly distributed near the tailings pond.The study area was affected by a combination of multiple heavy metals,with Cd and As reaching severe pollution levels.The three pathways of exposure for carcinogenic and noncarcinogenic risks were ranked as inhalation>oral ingestion>dermal absorption.The heavy metals in the study area posed certain hazards to human health.Specifically,oral ingestion of these heavy metals carried carcinogenic risks for both children and adults,as well as noncarcinogenic risks for children.There were differences in the sources of different heavy metals.The tailings pond had a large impact on the accumulation of Cd,Zn,and Pb.The source of Cr was the soil parent material,the source of As was mainly the soil matrix,and the source of Cu was mainly the nearby Cu ore.The purpose of this study is to more accurately understand the extent,scope,and source of heavy metals pollution near a typical mining area,providing effective help to solve the problem of heavy metals pollution.

Ecological Risk Assessment of Heavy Metals Pollution in Soil and Lotus Seeds in Xiangtan Lotus Planting Area

In order to study the pollution characteristics and potential ecological risks of heavy metals in soil of Xiangtan lotus planting area,the contents of Mn,Cu,As,Cd,Pb and Cr in soil and lotus seeds were analyzed in six main lotus planting areas.The comprehensive potential ecological risks of heavy metals in soil were evaluated by the potential ecological hazard index.The results showed that Cd concentration(mean value)was higher than the risk screening value and lower than the risk control value,and other heavy metals were lower or close to the risk screening value.The ecological risks of each element from large to small were Cd,Pb,As,Cu,Cr and Mn.The average value of the comprehensive ecological hazard index of the six sites was 224.7,which was a medium level of pollution risk.The lotus seeds corresponding to each site were also polluted by heavy metals to a certain extent,and Cd and Pb in the seeds exceeded the standard.Through the above analysis,the heavy metals in the soil of the lotus planting area presented a medium ecological risk.In order to ensure the safety of lotus production,it is necessary to strengthen the soil testing and management in the lotus planting area.

Rapid detection and risk assessment of soil contamination at lead smelting site based on machine learning

A general prediction model for seven heavy metals was established using the heavy metal contents of 207soil samples measured by a portable X-ray fluorescence spectrometer(XRF)and six environmental factors as model correction coefficients.The eXtreme Gradient Boosting(XGBoost)model was used to fit the relationship between the content of heavy metals and environment characteristics to evaluate the soil ecological risk of the smelting site.The results demonstrated that the generalized prediction model developed for Pb,Cd,and As was highly accurate with fitted coefficients(R^(2))values of 0.911,0.950,and 0.835,respectively.Topsoil presented the highest ecological risk,and there existed high potential ecological risk at some positions with different depths due to high mobility of Cd.Generally,the application of machine learning significantly increased the accuracy of pXRF measurements,and identified key environmental factors.The adapted potential ecological risk assessment emphasized the need to focus on Pb,Cd,and As in future site remediation efforts.

Distribution, Mobility, and Health Risks Assessment of Trace Metals in River Sediments from Intense Agricultural Activity Areas in West Africa

The economy of West African countries is mainly based on agriculture. However, the trace metal(loid)s contamination status in rivers is relatively unknown in the region. In this work, 45 surface sediments collected from the Bandama, Comoé, and Bia Rivers in south and south eastern Côte d’Ivoire (West Africa), were analyzed for total metal concentrations and chemical speciation. The results showed that the river sediments were considerably contaminated by Cd and moderately contaminated by As, Cu, Pb, and Zn. Significant spatial variations were observed among the stations but not between the rivers. Metals Cd and Cu were likely to cause more ecological risks. The speciation analysis unravelled that the metal(loid)s partitioned mainly in the residual fraction, with the potential mobile fraction varying from 14% to 28%. The study calls for establishment of strict policies relative to the application of fertilizers and agrochemicals and mining activities to protect the environment and human health risks.

Ecological risk assessment of heavy metals in sediments of Xiawan Port based on modified potential ecological risk index

Modified potential ecological risk index （MRI） was proposed based on the potential ecological risk index （RI） and risk assessment code （RAC） by modifying an index. The modified index was relevant to the chemical speciation of heavy metals. Xiawan Port, a typical region contaminated by industrial production, was selected as a case study area. The total concentrations and chemical speciation of heavy metals in sediments of Xiawan Port were analyzed. The experimental data indicate that Xiawan Port is seriously polluted by heavy metals, especially by Cd. The risks of heavy metals are evaluated by RI, RAC and MRI, respectively. The resluts of MRI show that the risks of heavy metals are in the decreasing order of Cd〉Pb〉Cu〉Zn. Comparison of results by different methods reveals that MRI integrates the characters of RI and RAC. MRI is recognized to be useful for risk managemnt of heavy metals in sediments.

Environmental availability and ecological risk assessment of heavy metals in zinc leaching residue

Four different methods,namely mineralogical analysis,three-stage BCR sequential extraction procedure,dynamic leaching test and Hakanson Potential Ecological Risk Index Method were used to access the environmental activity and potential ecological risks of heavy metals in zinc leaching residue.The results demonstrate that the environmental activity of heavy metals declines in the following order：CdZnCuAsPb.Potential ecological risk indices for single heavy metal are CdZnCuAsPb.Cd has serious potential ecological risk to the ecological environment and contributes most to the potential toxicity response indices for various heavy metals in the residue.

Comprehensive ecological risk assessment for heavy metal pollutions in three phases in rivers

Literature lacked in providing a comprehensive research on heavy metal detection in aquatic, biological and sedimentary states of rivers. The present study was imparted with all these three components of the river. Heavy metal toxicity or pollution index was used as a tool for ecological risk assessment by considering the single state studies conducted by many researchers. An intensive ecological risk assessment model was constructed and heavy metals were indicated as a serious threat to the environment. The model was applied to determining five toxic heavy metals in three states of the Songhua River. According to the ecological risk index, heavy metal pollution in three phases was categorized as aquatic〉biological〉sedimentary, while the overall descending order of heavy metal ecological risk index was as Cd〉Hg〉As〉Pb〉Cr. Cd and Hg were selected as the priority pollutants of Songhua River.

Source analysis and ecological risk assessment for heavy metals in the sediments of the Yangshan Deepwater Harbor in autumn and winter

Temporal and spatial variations of concentrations of heavy metals including mercury （Hg）, zinc （Zn）, lead （Pb）, arsenic （As）, copper （Cu）, and cadmium （Cd） in the sediments of the Yangshan Deepwater Harbor were determined based on 6 cruises in autumn and winter, respectively, from 2010 to 2013. The results demonstrated that the overall concentrations of heavy metals were low and distributed in uniform patterns. The concentrations of Hg, Zn, Pb, and Cd in autumn were significantly higher than those in winter with small fluctuations for As and Cu in terms of seasonal variations. Results of factor analysis showed that Pb, Cd, and Zn were derived from inland industrial and shipping discharges as well as the degradation of organic pollutants in marine environment. While agricultural pollutions, cargo shifting and construction debris from reclamation projects contributed to the sources of Cu, As, and Hg. Ecological risk assessment by Mean Sediment Quality Guideline Quotient （SQG-Q） revealed that the degree for eco-risk of the sediments was low-and-moderate in autumn, higher than that in winter. Hg and Cu were the dominant eco-risk factors. The results of Index of geoaccumulation （Igeo） showed that the whole sites of the sea area were barely influenced by Hg, As, Zn, and Pb, and the extents of Cd and Cu contaminations were in low grade. Contamination degree of all the six heavy metals could be ranked as the following： Cd〉Pb〉Zn〉Hg〉As. According to the results of integrated score of factor analysis, the contamination degree for heavy metals in sediments of the Yangshan Deepwater Harbor was low, despite sites No.5, No.4 and No.3, which were heavily contaminated compared with others.

Distribution Characteristic and Potential Ecological Risk Assessment of Heavy Metals in Latosol in the Western Area of Hainan Island

[Objective] The paper was to carry out ecological geochemical survey and ecological risk assessment on the heavy metals in latosol in western area of Hainan Island.[Method] The contents of six heavy metals including Cr,Cu,Zn,As,Cd and Pb in latosol in western area of Hainan Island were analyzed.Single-factor index method and Hakanson ecological risk index method were used to evaluate the integrated pollution effect of heavy metals in latosol.[Result] The average contents of Cr,Cu,Zn,As,Cd and Pb in latosol in western area of Hainan Island were 65.57,35.16,93.56,8.50,0.24 and 79.29 mg/kg,respectively.The major pollution factor of heavy metal was Pb.The sequence of influence factors of various heavy metals was PbCu = ZnCrAsCd.The potential ecological risk coefficient of various heavy metals was PbCdCuAsCrZn.The average value of potential ecological risk index（RI）was 45.14,belonging to low ecological risk range.[Conclusion] The heavy metal pollution in latosol in western area of Hainan Island belongs to slight pollution.

Analysis on Ecological Risk in Northwest China

Based on scenario analysis method, assuming different economic develop- ment policies, and AHP method, the ecological indicators and risk prediction models were established. The trends of ecological risk in the northwest region were ana- lyzed. The results showed that： in the northwest, the potential ecological risks of the population economy, water resources, and land resources and natural disasters still existed. However, the environment and respond to ecological risks were decreasing. Therefore, a regional balanced development measures had been taken to curb the western trend of ecological deterioration. So that socio-economic development, re- sources, environment, and economy were expected to a virtuous cycle, and the eco- logical risks would be reduced. This study provides the basis for land and water use planning and environmental protection of government decision-making and management.

Evaluation of ecological risk and primary empirical research on heavy metals in polluted soil over Xiaoqinling gold mining region,Shaanxi,China

Soil,crop and residents'hair over Xiaoqinling gold mining region,China,which was selected as a case study,were sampled and analyzed for Hg,Cd,Pb,Cu,Cr,As and Zn concentrations.The concentrations of heavy metals in soil or crop and hair samples were used to assess their potential ecological risks,or to find the responses to these metals as evidences to prove the potential risk was coming down to observed harm,respectively.The results showed that,these metals in soil were ranked by severity of ecological risk as Hg>Cd>Pb>Cu>Cr>As>Zn,based on their single-element indexes.In the view of the potential ecological risk indexes,of all soil samples,about half had significantly high or high potential ecological risk,which covered more than 74%of the studied region.Most of the risks were 97.41%from Hg,Pb and Cd,especially,84.37%from Hg.Both the single-element and potential ecological risk indexes indicated that,the ecological risk grades had a special spatial characteristic,and increased from northwest to southeast generally.This was agreed with the spatial distribution of the strength in gold mining activities over the studied region.The concentrations of Hg and Pb were higher than their relative backgrounds in the corps,and were even 9.48 and 25.09 times higher than their relative backgrounds in residents'hair,respectively.All these showed that the heavy metals in the soil had a high potential ecological risk,especially,had been affecting these crops'growing and yield,and even the residents'health through food strains.Obviously,these metals'potential ecological harm had been coming down to observed harm to the ecology.

Soil Contamination by Heavy Metals and Evaluations on Potential Ecological Risks in an Antimony Mine

To study the status of soil quality in an antimony mine, soil samples were collected from different regions and the elements＇ contents of Sb, Cd, Cr, Cu, Zn, Pb, Hg, Ni and As were analyzed using single factor pollution index, Nemerow index and potential ecological risk index. The heavy metal contamination of soils were evaluated. The results showed that Nemerow index for each sampled point was less than 0.7, meaning a clean state. When potential ecological risk assessment was conducted, the sampled point was less than 150, belonging to light pollution.

Speciation, distribution, and potential ecological risk assessment of heavy metals in Xiamen Bay surface sediment

Based on the survey of surface sediment in Xiamen Bay in October 2011, the speciation, distribution, and potential ecological risk assessment of heavy metals （Cu, Pb, Zn, Cd, and Cr） in this area were studied us-ing the sequential extraction method and ecological risk assessment method. The results indicated：（1） the total concentrations of these heavy metals were influenced by runoff, industrial wastewater, and sewage, and were all higher in the coastal area than the offshore area while the highest area of Pb was a little far-ther away from the coastal water due to atmosphere deposition;（2） sequential extractions suggested that Cu was mainly composed with residual and Fe/Mn-oxide bound fractions, Pb was bound to Fe/Mn-oxide, Zn and Cr were dominated by residual, and Cd bound to exchangeable and carbonate fractions; （3） the order of migration and transformation sequence was Cd＆gt;Pb＆gt;Cu＆gt;Zn＆gt;Cr and the degree of pollution was Cd＆gt;Pb＆gt;Cu＆gt;Zn＆gt;Cr;and （4） the ratios of the secondary and primary phases showed that Zn and Cr were both clean, Cu may be polluted, Pb was moderately polluted, while Cd was heavily polluted.