Yangtze River Watershed Research Articles

Legacy phosphorus delays the accomplishment of expected phosphorus management object

Legacy phosphorus (P) in watersheds continuously affects the water quality. The time lag between anthropogenic P input and algal bloom has made P dynamics prediction in aquatic ecosystems more challenging. Whether the legacy P in the Yangtze River Watershed (YRW) exceeds its storage threshold remains unknown, and the continuous impact of legacy P on the water quality has not been analyzed. This study aimed to evaluate variation trends (1970–2018) and influencing factors for accumulated P in the YRW under different economic development periods, quantitatively identify the watershed P storage threshold based on the two split line models and estimate the time required for the return of legacy P to the baseline level using an exponential decay process. The results showed that the P storage threshold of the YRW was surpassed due to intense anthropogenic activities, and the residual P still had an impact on aquatic ecosystems for a long time. The dissolved total P loadings may become the top priority to achieve better P management goals. The time lags for the legacy P restoration would require for about 1000 years to be exhausted. The legacy P in the YRW would continuously undermine the restoration efforts of the water quality. The combined effects of watershed P surplus reductions and depletion of residual P may become essential to better manage P in the future. We still need to strengthen our efforts to make soil legacy P more absorbed by crops and improve sewage treatment capacity to achieve sustainable development of YRW.

Non-native species in Poyang Lake Basin: status, threats and management

Poyang Lake is the largest freshwater lake in China and sustains a high level of biodiversity in the mid-reach area of the Yangtze River watershed. Poyang Lake is also one of the most important aquaculture regions in China, and a great number of non-native species have been introduced into it. We present a current and well-documented list of the non-native species of plants, molluscs, crustaceans, fishes, reptiles, and amphibians currently found in Lake. We found that there are 103 non-native species (83 vascular plants, 12 fishes, three crustacea, two molluscs, two reptiles and one amphibian) that have invaded Poyang Lake Basin, of which 96 non-native species were introduced after 2000. The invasion rate of non-native species reached 4.36 species year-1, which is the highest invasion rate recorded in freshwater ecosystems. The primary pathways of introduction are through the ornamental trade and unintentional escapes (30 species each, respectively), followed by food (19), aquaculture (15), forage grass (four), medicinal and oil (two, respectively), and biocontrol (one). The origins of non-native species are North America (29.12%), Asia (25.24%), South America (20.38%), Africa (18.44%), Europe (5.82%) and Oceania (0.97%). Many non-native species provide significant support for the rapid development of the local economy (such as aquaculture). However, many non-native species pose a great threat to local biodiversity and societal development. More studies that include monitoring and the development of strategies for managing and eliminating non-native species in Poyang Lake are needed.

Nitrate sources and transformations along the Yangtze river and its changes after strict environmental regulation

The exploration of the sources and fate of nitrate in surface waters along with the evaluation of the implementation of environmental regulations is essential for preventing and remediating the serious problem of nitrate pollution. However, the nitrate sources and transformations in the Yangtze River and its changes after strict environmental regulation remain unclear. In this pursuit, the present study investigated the spatiotemporal variations of the nitrate source and transformations in the Yangtze River by determining the nitrate isotopic compositions (δ15N-NO3− and δ18O-NO3−) and water chemistry during the wet and dry seasons. Furthermore, the current measurements of the nitrate sources and transformations after the environmental regulations were compared to the historical records in 2006. The results showed that the NO3−-N concentration gradually increased along the river, similar to that in 2006. However, the spatial pattern of δ15N and δ18O of NO3− values obviously changed after the environmental regulations. It was found that the δ15N-NO3− values increased from the headwater to the lower stream, which can be due to assimilation of phytoplankton. The δ18O-NO3− values showed a gradual decrease in the headwater area, an increase at the upper stream, and stabilized in the middle and lower stream. In addition, the δ18O-NO3− value was significantly higher during the wet season than in the dry season (P < 0.05). However, there was no significant seasonal difference in NO3−-N concentrations, δ15N-NO3− value, and nitrate source and transformations. The results of source apportionment indicated that the dominated nitrate source changed from the manure and sewage to soil N after the implementation of the environmental regulations. However, the major nitrate transformations were not affected by the environmental regulations and nitrification was still prevalent in the Yangtze River watershed. The change of the dominated nitrate source validated the effectiveness of the environmental regulation; however, the increase in the nitrate concentration reflected the heavy inputs of residual nitrate from the watershed. This study identified the nitrate sources and transformation processes and its changes after strict environmental regulations, and provided significant information for adjusting and formulating new policies to further control the nitrate pollution.

Optimization of management by analyzing ecosystem service value variations in different watersheds in the Three-River Headwaters Basin

Variation analysis of ecosystem services (ESs) is an important means of regional watershed management, especially for the ecologically fragile Three-River Headwaters Basin (TRHB), which is an important part of the national ecological security barrier. In this study, meteorological data, remote sensing images and land use data from 2000 to 2020 in the TRHB were collected. Based on the estimation of ecosystem service values (ESVs), the spatial-temporal variations of ESVs in the three watersheds were analyzed via spatial autocorrelation analysis, one-way analysis of variance (ANOVA), and correspondence analysis. The study indicates that for the 20-year changes in the TRHB, the provisioning service (PS) and regulating service (RS) increased in most areas except for a small decrease in the northwest, while the supporting service (SS) value in most areas in the southwest showed a decreasing trend. Through the difference results of different watersheds, it can be seen that the differences in the PS and RS values among the three watersheds became increasingly more significant with the passage of time. Moreover, a significant correspondence was identified between each watershed and each ESV level, whereby the highest ESV levels (SS-VI, RS-VI, and PS-VI) mainly corresponded to the Yellow River watershed, the high values (SS-V, RS-V, PS-V, SS-IV, RS-IV, and PS-IV) mainly corresponded to the Lancang River watershed, and the low values (SS-I, RS-I, and PS-I) corresponded to the Yangtze River watershed. Our analysis shows the variation characteristics of ESVs to provide a guiding basis for ensuring the precise implementation of the management and protection of watersheds in the TRHB or similar areas.

Spatiotemporal variation and hotspots of climate change in the Yangtze River Watershed during 1958–2017

Spatiotemporal variation and hotspots of climate change in the Yangtze River Watershed during 1958–2017

Legacy Phosphorus Delay the Accomplishment of Expected Phosphorus Management Object in the Yangtze River Watershed

Legacy Phosphorus Delay the Accomplishment of Expected Phosphorus Management Object in the Yangtze River Watershed

A Statistical Hydrological Model for Yangtze River Watershed Based on Stepwise Cluster Analysis

Streamflow prediction is one of the most important topics in operational hydrology. The responses of runoffs are different among watersheds due to the diversity of climatic conditions as well as watershed characteristics. In this study, a stepwise cluster analysis hydrological (SCAH) model is developed to reveal the nonlinear and dynamic rainfall-runoff relationship. The proposed approach is applied to predict the runoffs with regional climatic conditions in Yichang station, Hankou station, and Datong station over the Yangtze River Watershed, China. The main conclusions are: 1) the performances of SCAH in both deterministic and probabilistic modeling are notable.; 2) the SCAH is insensitive to the parameter p in SCAH with robust cluster-tree structure; 3) in terms of the case study in the Yangtze River watershed, it can be inferred that the water resource in the lower reaches of the Yangtze River is seriously affected by incoming water from the upper reaches according to the strong correlations. This study has indicated that the developed statistical hydrological model SCAH approach can characterize such hydrological processes complicated with nonlinear and dynamic relationships, and provide satisfactory predictions. Flexible data requirements, quick calibration, and reliable performances make SCAH an appealing tool in revealing rainfall-runoff relationships.

Bentazone in water and human urine in Wuhan, central China: exposure assessment.

Bentazone is a widely used post-emergence herbicide, while no data was available on its concentrations in tap water from China and in urine among the general population. It was determined in the source (Wuhan section of the Yangtze River watershed), treated, and tap water (n = 20, 20, and 170, respectively) in different seasons (2019) in Wuhan, central China. Also, urine samples (n = 38) collected from healthy adults in Wuhan (September 2020) were analyzed to characterize its urinary concentration. Bentazone was detected in all the source and treated water samples. Its concentrations in the source water in July were higher than those in February (median: 17.9 ng/L vs. 2.86 ng/L) (p < 0.05). It cannot be removed efficiently (27.8-27.9%) by conventional drinking water treatment using NaClO, but it can be efficiently removed by using chlorine dioxide or ozone combined with activated carbon. Bentazone was frequently detected (detection frequency: 96.3%) in 160 tap water samples (underwent conventional treatment) (median: 1.95 ng/L, range: <0.02-47.0 ng/L), while it was not detectable in tap water samples that underwent ozone combined with activated carbon. Seasonal variations were found, with the lowest median concentration (ng/L) in April (0.46) and the highest in July (17.6). In addition, bentazone was frequently (92.1%) detected in human urine samples (median: 0.02 ng/mL; range: <0.01-0.11 ng/mL). The estimated daily intake of bentazone based on its median concentration in tap water (0.04 ng/kg-body weight [bw]/day) accounted for approximately 8% of that based on the median urinary concentration (0.48 ng/kg-bw/day). This is the first time to characterize its occurrence in drinking water from China and its occurrence in the urine of the general population.

Geochemistry of Dissolved Heavy Metals in Upper Reaches of the Three Gorges Reservoir of Yangtze River Watershed during the Flood Season

Dissolved heavy metals (HMs), derived from natural and anthropogenic sources, are an important part of aquatic environment research and gain more international concern due to their acute toxicity. In this study, the geochemistry of dissolved HMs was analyzed in the upper Three Gorges Reservoir (TGR) of the Yangtze River (YZR) watershed to explore their distribution, status, and sources and further evaluate the water quality and HM-related risks. In total, 57 water samples were collected from the main channel and tributaries of the upper TGR. The concentrations of eight HMs, namely V, Ni, Cu, Zn, As, Mo, Cd, and Pb, were measured by ICP-MS. The mean concentrations (in μg/L) of eight HMs decreased in the order: As (1.46), V (1.44), Ni (1.40), Mo (0.94), Cu (0.86), Zn (0.63), Pb (0.03), and Cd (0.01). The concentrations of most HMs were 1.4~8.1 times higher than that in the source area of the YZR, indicating a potential anthropogenic intervention in the upper TGR. Spatially, the concentrations of V, Cu, As, and Pb along the main channel gradually decreased, while the others were relatively stable (except for Cd). The different degrees of variations in HM concentrations were also found in tributaries. According to the correlation analysis and principal component (PC) analysis, three PCs were identified and explained 75.1% of the total variances. combined with the concentrations of each metal, PC1 with high loadings of V, Ni, As, and Mo was considered as the main contribution of human inputs, PC2 (Cu and Pb) was primarily attributed to the contribution of mixed sources of human emissions and natural processes, and Zn and Cd in PC3 were controlled by natural sources. Water quality assessment suggested the good water quality (meeting the requirements for drinking purposes) with WQI values of 14.1 ± 3.4 and 11.6 ± 3.6 in the main channel and tributaries, respectively. Exposure risk assessment denoted that the health effects of selected HMs on the human body were limited (hazard index, HI &lt; 1), but the potential risks of V and As with HI &gt; 0.1 were non-negligible, especially for children. These findings provide scientific support for the environmental management of the upper TGR region and the metal cycle in aquatic systems.

Sedimentary record of nutrients and sources of organic matter in the Shuanglong reservoir, Dianchi watershed, China.

In the last few decades, the eutrophication of lakes has been a serious issue in the middle and lower reaches of the Yangtze River watershed. To explore the relationship between lake systems and anthropogenic activities, sediments were collected from the Shuanglong reservoir in the Dianchi watershed in Southwest China. Total nitrogen (TN), total phosphorus (TP), total organic carbon (TOC), and the carbon isotopic ratio (δ13C) were analyzed in sediment cores to reconstruct the effects of natural succession and human activities on the past lacustrine environmental conditions. A reliable chronology of the sediment core was established by using the 210Pb dating technique, which indicated that the age span of the 70-cm sediment core is from the years 1871 to 2011. Above - 31 cm depth in the core, TN, TP, TOC, C/N, and δ13C increased significantly, indicating that eutrophication has occurred since the 1980s. By combining the indicators of δ13C and C/N, it was shown that terrestrial and lacustrine components were the main sources of organic matter (OM) in the reservoir, which was mostly controlled by terrestrial C3 plants and algae. Since the 1980s, increased sewage discharge, fish aquaculture, fertilizer application, population, and economic strength have sped up the eutrophication process, and the eutrophication was further intensified in 2001.

Spatial-temporal Variations and the Regulators of Nitrate Status in Shallow Groundwater of the Typical Mountainous Agricultural Watershed in the Upper Reaches of the Yangtze River

Shallow groundwater is the main drinking water supply for the mountainous area in the upper reaches of the Yangtze River, while its quality is often degraded by nitrate (NO3--N) pollution due to intensive agricultural production activities. In the present study, we selected a mountainous agricultural watershed in the upper reaches of the Yangtze River to investigate the land use, management, and hydrogeological conditions, aiming to clarify the spatial-temporal variations in NO3--N concentration of shallow groundwater, thereby exploring the key regulators. The results showed that the NO3--N concentrations of the groundwater ranged from 0.40 to 12.51 mg ·L-1in the study area, and the exceeding ratio was nearly 30%. On an average, NO3--N concentrations for the wet season were higher than that for the dry season, indicating great variations in NO3--N concentration across different seasons. In addition, the spatial variations of NO3--N concentration in groundwater were also significant among different sub-catchment, which was mainly due to variations in the groundwater table depth and land uses. Furthermore, the significant correlations between the NO3--N concentrations and concentrations of Cl-, NH4+-N, DOC, and SO42- in the shallow groundwater were also explored in this study, suggesting that the NO3--N concentrations were likely to depend on the chemical factors of the shallow groundwater in the study area. Overall, our current study highlights that the characterization of spatial-temporal variations of NO3--N status in shallow groundwater and illustration of key regulators are essential to mitigate NO3--N pollution and prevent quality degradation of shallow groundwater in mountainous rural areas of the upper Yangtze River watershed.

The Fate and Transport of Nutrient and Algal Contaminants in Xiangxi Bay of the Three Gorges Reservoir

Water quality in the Three Gorges Reservoir and all its tributaries is of critical significance for the ecological and economic development of the middle and lower Yangtze River watershed. The construction of the reservoir impoundment has caused higher water surface elevation, slower current velocity, and even backflow in its main tributaries, including the Xiangxi River. More nutrient species related to nitrogen and phosphorous are being conveyed to the water body and retained in the river's bay region much longer than previously, leading to more frequent eutrophic events such as algal blooms, and significantly threatening the downstream water quality. This study focuses on the nutrient species levels, statistically analyzing the available data to determine the effect of backflow and estimate the variation in algal levels, developing mass balances for the water budget and important contaminants, and calculating the ratio of total nitrogen to total phosphorus. Based on the data from the eutrophication processes happened in the Xiangxi River during the period from January to November 2010, total nitrogen is the limiting factor. The amount of water accumulated in the Xiangxi River was 1.108×1010 m3, and the water level rose by 5.78 m from January to November 2010. Most of the phosphorus and ammonia in the river came from non-point source pollution. The results will be used to help verify and calibrate variations in the water flow rate and the associated point source and non-point source pollution. Since the Xiangxi River is a representative tributary of the Three Gorges Reservoir, the research method developed and conclusions drawn will provide a valuable reference for eutrophication investigations of other tributaries.

Numerical Study of Remote Sensed Dredging Impacts on the Suspended Sediment Transport in China’s Largest Freshwater Lake

As the largest freshwater lake in China, Poyang Lake plays an important role in the ecosystem of the Yangtze River watershed. The high suspended sediment concentration (SSC) has been an increasingly significant problem under the influence of extensive sand dredging. In this study, a hydrodynamic model integrated with the two-dimensional sediment transport model was built for Poyang Lake, considering sand dredging activities detected from satellite images. The sediment transport model was set with point sources of sand dredging, and fully calibrated and validated by observed hydrological data and remote sensing results. Simulations under different dredging intensities were implemented to investigate the impacts of the spatiotemporal variation of the SSC. The results indicated that areas significantly affected by sand dredging were located in the north of the lake and along the waterway, with a total affected area of about 730 km2, and this was one of the main factors causing high turbidity in the northern part of the lake. The SSC in the northern area increased, showing a spatial pattern in which the SSC varied from high to low from south to north along the main channel, which indicated close agreement with the results captured by remote sensing. In summary, this study quantified the influence of human induced activities on sediment transport for the lake aquatic ecosystem, which could help us to better understand the water quality and manage water resources.

Molecular identification of Azolla in the Yangtze River Watershed, China

Seven samples were collected broadly from the Yangtze River watershed of China during a search for Azolla pinnata asiatica, intended as molecular references to identify the subspecies of a new exotic congener in Florida. Molecular taxonomic analysis was carried out using chloroplast trnG-trnR and trnL-trnF, in addition to nuclear ITS1 sequences, which when referenced against NCBI yielded the unexpected result of Azolla caroliniana for all seven samples. In four of five provinces sampled, cold-tolerant A. filiculoides and A. caroliniana would be expected to outcompete A. pinnata due to biological advantages during over-wintering and early spring growth. However, A. caroliniana’s predominance over A. filiculoides in this limited sampling taken widely from the Yangtze watershed was unexpected given the historical predominance of Azolla filiculoides introduction in the literature. The explanation may be A. caroliniana’s use in early rice systems, its intermediate tolerance to heat and cold, and its high biomass production. Azolla caroliniana’s hybrid status is further characterized here using NCBI ITS1 Blasts of an SLA Illumina 2000 dataset.

Significant trade-off for the impact of Grain-for-Green Programme on ecosystem services in North-western Yunnan, China

Ecological restoration can mitigate human disturbance to the natural environment and restore ecosystem functions. China's Grain-for-Green Programme (GFGP) has been widely adopted in the last 15years and exerted significant impact on land-use and ecosystem services. North-western Yunnan is one of the key areas of GFGP implementation in the upper Yangtze River. Promotion of ecosystem services in this region is of great importance to the ecological sustainability of Yangtze River watershed. In this study, remote sensing and modelling techniques are applied to analyse the impact of GFGP on ecosystem services. Results show that the transformation from non-irrigated farmland to forestland could potentially improve soil conservation by 24.89%. Soil conservation of restored forest was 78.17% of retained forest while net primary production (NPP) already reached 88.65%, which suggested different recovery rates of NPP and soil conservation. Increasing extent of GFGP implementation improved soil conservation but decreased NPP and water yield at sub-watershed scale, which revealed trade-offs between ecosystem services under ecological restoration. Future ecosystem management and GFGP policy-making should consider trade-offs of ecosystem services in order to achieve sustainable provision of ecosystem services.

Efficient estimation of flood forecast prediction intervals via single‐ and multi‐objective versions of the LUBE method

AbstractPrediction intervals (PIs) are commonly used to quantify the accuracy and precision of a forecast. However, traditional ways to construct PIs typically require strong assumptions about data distribution and involve a large computational burden. Here, we improve upon the recent proposed Lower Upper Bound Estimation method and extend it to a multi‐objective framework. The proposed methods are demonstrated using a real‐world flood forecasting case study for the upper Yangtze River Watershed. Results indicate that the proposed methods are able to efficiently construct appropriate PIs, while outperforming other methods including the widely used Generalized Likelihood Uncertainty Estimation approach. Copyright © 2016 John Wiley &amp; Sons, Ltd.

Lower Upper Bound Estimation Method Considering Symmetry for Construction of Prediction Intervals in Flood Forecasting

It is widely accepted that Prediction Interval (PI) can provide more accurate and precise information than deterministic forecast when the uncertainty level increases in flood forecasting. Coverage probability and PI width are two main criteria used to assess the constructed PI, rarely has there been an index to quantify the symmetry between target value and PI. This study extends a newly proposed PI estimation method called Lower Upper Bound Estimation (LUBE) method, which adopts an Artificial Neural Network (ANN) with two outputs to directly generate the upper and lower bounds of PI without making any assumption about the data distribution. A new Prediction Interval Symmetry (PIS) index is introduced and a new objective function is developed for the comprehensive evaluation of PI considering their coverage probability, width and symmetry. Furthermore, Shuffled Complex Evolution algorithm (SCE-UA) is used to minimize the objective function and optimize ANN parameters in the LUBE method. The proposed method is applied to a real world flood forecasting case study of the upper Yangtze River Watershed. The result shows that the SCE-UA based LUBE method with new objective function is very efficient, meanwhile, the midpoint forecasting of the PI obtains excellent performance by evidently improving the symmetry of PI.

Estimating surface water area changes using time-series Landsat data in the Qingjiang River Basin, China

The Qingjiang River Basin, which is 423 km long in the Hubei province, China, is the first large tributary of the Yangtze River below the Three Gorges. The Qingjiang River Basin surface water area monitoring plays an important role in the water resource management strategy and regular monitoring management of the Yangtze River watershed. Hydropower cascade exploitation, which started in 1987, has formed three reservoirs including the Geheyan reservoir, the Gaobazhou reservoir, and the Shuibuya reservoir in the midstream and downstream of the Qingjiang River Basin. They have made a great impact on surface water area changes of the Qingjiang River Basin and need to be taken into account. We monitor the Qingjiang River Basin surface water area changes from 1973 to 2010. Ten scenes from the Multispectral Scanner System (MSS), seven scenes from the Thematic Mapper (TM), and two scenes from the Enhanced Thematic Mapper Plus (ETMþ) remote sensing data of Landsat satellites, the normal- ized different water index (NDWI), the modified NDWI (MNDWI), and Otsu image segmenta- tion method were employed to quantitatively estimate the Qingjiang River Basin surface water area in the 1970s, 1980s, 1990s, and 2000s, respectively. The results indicate that the surface water area of the Qingjiang River Basin shows a growing trend with the hydropower cascade development from the 1980s to the first decade of the 21st century. The study concluded the significance of human activities impact on surface water spatiotemporal distribution. Surface water accretion is significant in most parts of the Qingjiang River Basin and might be related to the constructed cascade hydropower dams. © 2012 Society of Photo-Optical Instrumentation Engineers (SPIE). (DOI: 10.1117/1.JRS.6.063609)

Nine years of water resources monitoring over the middle reaches of the Yangtze River, with ENVISAT, MODIS, Beijing‐1 time series, Altimetric data and field measurements

AbstractPoyang and Dongting Lakes, major water resources and key elements for natural flood control and reduction within the Yangtze River middle basin, were monitored from 2000 to 2008, with a re‐visiting period of 10 days, using ENVISAT ASAR, and completed by MODIS data, validated by Beijing 1 time series. GPCP and TRMM time series were utilized to derive regional meteorological indicators. At the lake scale as well as their subdivisions ones, results allowed the characterization of lake behaviors. Even if the Dongting and Poyang lakes mechanisms are substantially different, their water surface areas and water level variations exhibit a good similarity, including the same year of major flooding (2002) and the same year of lowest extent of inundation (2001). Both lakes present astonishingly low water levels and low surface areas in summer of 2006, being associated with a very early draw‐off. Few reasons could explained it: (i) a rainfall deficit at the sub‐watershed level; (ii) a hydrological event in the upper stream part, namely a possible closure of the Three Gorges Dam (TGD) gates; or (iii) a global climate change effect at the regional scale. The reasons for the dramatic water dropdown are neither a local rain deficit nor a change in the TGD management. The smallest water extent for wet season observed in 2006, appeared to be linked with a severe drought within the upper stream part of the Yangtze River basin. In addition, an impressive decreasing tendency of water surface and level is observed in the middle reaches of the Yangtze River, linked with relatively constant decreasing precipitations over the last decade. This synergistic utilization of data from earth observation systems and in situ data provide valuable information on water resource management at the scale of the middle Yangtze River watershed.

Lead (Pb) isotopes as a tracer of Pb origin in Yangtze River intertidal zone

In order to investigate the source of Pb within the Yangtze River intertidal zone, studying Pb isotope ratios is a likely approach because the ratios of these Pb isotopes can be used to identify the natural or anthropogenic origin of Pb. In this study, a total of 59 surface sediment samples (< 5 cm) were collected during 2004 and 2005 from 26 sites in the Yangtze River intertidal zone. We measured the total Pb concentrations and Pb isotopes ( 204Pb, 206Pb, 207Pb and 208Pb) and found that the total Pb concentrations varied from 18.3 to 44.1 mg kg − 1 with an average concentration of 27.3 mg kg − 1 . The observed Pb isotope ratios, excluding one station near Shanghai Pudong Airport which is significantly influenced by anthropogenic sources, varied from 18.459 to 18.750 for 206Pb/ 204Pb, 15.628 to 15.728 for 207Pb/ 204Pb, and 38.715 to 39.213 for 208Pb/ 204Pb. This study shows that Pb found within the Yangtze River intertidal zone sediments was mainly from the catchment in the Yangtze River watershed. Significant Pb pollution was not discerned in the Yangtze River intertidal zone. However, Pb contamination in some localized areas was suggested by Pb enrichment factor (EF).