Beiyun River Research Articles

Spatial distribution of trace elements associated with organic carbon along the Beiyun River basin, Beijing, China

Pollution resulting from terrestrial and aquatic trace elements has become a severe problem across the world. Organic carbon (OC) content has a high affinity for metallic contaminants and it acts as a significant sink for trace elements. The decomposition of OC content directly influences the bioavailability of trace elements. The decomposition of OC content and OC distribution vary spatially, these processes affect the release of trace elements and need further research. In the current study, sediment samples from the surface sediment along Beiyun River (Section 1 to Section 4 from upper to lower reaches), which is situated in the rapidly urbanized Beijing metropolis, were measured for OC, moisture, hardness, and trace elements. The OC contents were found to have a substantial difference among all four river sections along the urbanized river gradient. Whereas the higher OC contents were found in Sections 2 (Urbanized uplands) and 3 (farmland) compared to those in Sections 1 (forest) and 4 (farmland and part of constructed areas). On the other hand, the highest value of the correlation coefficient was found among the different values of trace elements and OC content in the riverine zone of the Beiyun River basin. OC contents play a vital role in the transformation and origin of trace elements in the surface sediment of the Beiyun River basin. The One-way Analysis of Variance (ANOVA) was applied to compare the means of OC and trace elements at different sections indicating no significant difference. However, source identification of trace elements indicated that a geogenic source was responsible for higher contents of As and (69.95%). Simultaneously, the natural OC, agricultural activities, and industrial waste contributed about (21.10%) towards the Cd and Zn, and about 10% for Cr and Cu. The current study concludes that the absolute principle component analysis–multiple linear regression (APCA-MLR) method can be successfully used to investigate the trace elements (Zn, Ni, Pb, Mn, Cd, Cu, and As) interactions through OC content resulting in determination of the various sources of contamination to cause negative environmental impacts on the ecosystem and human health. So, the current study provides a baseline for a quantitative evaluation of trace elements under different sediment of OC contents.

Contribution of nitrogen sources to streams in mixed-use watershed varies seasonally in a temperate region.

The Beiyun river flows through a hot spot region of Beijing-Tianjin-Hebei in China that serves a majority of occupants. However, the region experiences severe nitrate pollution, posing a threat to human health due to inadequate self-purification capacity. In that context, there is an urgent need to assess nitrate levels in this region. Herein, we used δ15N-NO3, δ18O-NO3 isotopes analysis, and stable isotope analysis model to evaluate the nitrate source apportionment in the Beiyun river. A meta-analysis was then used to compare the potential similarity of nitrate sources among the Beiyun riverine watershed and other watersheds. Results of nitrate source apportionment revealed that nitrate originated from the manure and sewage (contribution rate: 89.6%), soil nitrogen (5.9%), and nitrogen fertilizer (3.9%) in the wet season. While in the dry season, nitrate mainly originated from manure and sewage (91.6%). Furthermore, different land-use types exhibited distinct nitrate compositions. Nitrate in urban and suburban areas mostly was traced from manure and sewage (90.5% and 78.8%, respectively). Notably, the different nitrate contribution in the rural-urban fringe and plant-covered areas were manure and sewage (44.3% and 32.8%), soil nitrogen (26.9% and 35.7%), nitrogen fertilizer (23.5% and 29.4%), and atmospheric deposition (5.3% and 2.0%). Through a meta-analysis, we found nitrogen fertilizer, soil nitrogen, and manure and sewage as the main nitrate sources in the Beiyun riverine watershed or the other similar complexed watersheds in the temperate regions. Thus, this study provides a scientific basis for nitrate source apportionment and nitrate pollution preventive management in watersheds with complexed land-use types in temperate regions.

Influence of land use type and urbanization level on the distribution of pharmaceuticals and personal care products and risk assessment in Beiyun River, China

Influence of land use type and urbanization level on the distribution of pharmaceuticals and personal care products (PPCPs) from the developed regions of Beijing-Tianjin-Hebei in the northern China was evaluated. The seasonal and spatial variations of the 22 target PPCPs were analyzed in the 63 sampling sites along the whole Beiyun River Basin. Results showed that the total PPCPs concentration had a wide variation range, from 132 ng L−1 to 25474 ng L−1. Spatial interpolation analysis showed that agricultural land presented higher PPCPs contamination level than build-up land (p < 0.05) and the concentration was negatively correlated with urbanization level. Source apportionment showed the untreated sewage source contributed to 34%–53% of the PPCPs burden in the Beiyun River. Risk assessment indicated that diethyltoluamide, carbamazepine, octocrylene, gemfibrozil and triclocarban had high risks (RQ > 1), and small tributaries had the highest mixed risk (MRQ = 34). Species sensitivity distribution combined with the safety threshold method showed that PPCPs would have potential risk on aquatic organisms even at very low concentrations and triclocarban posed the highest risk in the Beiyun River.

Analysis of Spatial-Temporal Variation Characteristics of Potential Non-point Source Pollution Risks in the Upper Beiyun River Basin Using Different Weighting Methods

Non-point source pollution has become an important factor affecting the aquatic ecological environment and human health, and the analysis of spatial-temporal variations in non-point source pollution risks is an important prerequisite for pollution control. Based on land-use and land-cover data from 1980 to 2020, the potential non-point source pollution index (PNPI) model was applied in the upper Beiyun River Basin using different weighting methods. The results showed that:① The potential risk of non-point source pollution is high in the southeast and low in the northwest of the basin. Between 1980 and 2020, the total area of extremely high-risk and high-risk non-point source pollution regions showed a decreasing trend, and the main types of land use for extremely high-risk and high-risk regions gradually evolved from paddy fields, drylands, and orchards to urban and rural residential land; ② The weighting of the land use index determined by the mean-square deviation decision, entropy, coefficient of variation, and expert scoring methods was largest among the three PNPI indices, with average weightings of 0.46, 0.53, 0.45, and 0.48, respectively. However, the weightings for runoff and distance indices determined by different weighting methods were notably different, and the proportions of regions with different levels of non-point source pollution risk also varied; ③ The exponential function method, which describes the relationship between source factors and transport factors by constructing the exponential functions of land use, runoff, and distance indices, provided results that are more consistent with the spatial distribution characteristics of non-point source pollution risk in the basin. The proportions of extremely low-risk and extremely high-risk regions are 54.22% and 6.23%, respectively. These results provide scientific reference for risk analysis and the control of non-point source pollution in this basin.

Sources, transformations of suspended particulate organic matter and their linkage with landscape patterns in the urbanized Beiyun river Watershed of Beijing, China

This study explored the sources, transformations of suspended particulate organic matter (POM), and the influence of landscape patterns on POM within the Beiyun River Watershed by applying the stable carbon and nitrogen isotope technique combined with multiple statistical analyses. The POM variables showed great spatial fluctuations under different urban development gradients. Analysis of multiple isotopes revealed that assimilation of phytoplankton might exist in the rainy season, while nitrification occurs in the dry season. SIAR modeling results indicated that the sewage debris and phytoplankton were the main sources of POM in both seasons, accounting for 52.58% and 38.39% in the rainy season, 33.17% and 31.95% in the dry season, respectively. Spatiotemporal variations of POM sources existed in the study watershed, probably due to urbanization and human disturbance. The multiple linear stepwise regression and redundant analysis results indicated that landscape metrics reflecting contagion and fragmentation at the class level correlated well with the POM variables over seasons. Interspersion and juxtaposition indices of grassland and water were negatively related to POM variables in the rainy season, whereas the landscape division index of buildup land showed negative correlations with POM parameters in the dry season. Increasing the adjacency of grassland and water to other land uses, while reducing the aggregation of buildup lands would be an efficient way for urban river water quality improvement.

Health risk assessment based on source identification of heavy metals: A case study of Beiyun River, China

Long-term retention and accumulation of heavy metals in rivers pose a great threat to the stability of ecosystems and human health. In this study, Beiyun River was taken as the example to quantitatively identify pollution sources and assess the pollution source-oriented health risk. A total of 8 heavy metals (Mn, Ni, Pb, Zn, As, Cr, Cd, and Cu) in Beiyun River were measured. Ordinary kriging (OK) and inverse distance weight (IDW) methods were used to predict the distribution of heavy metals. The results showed that the OK method is more accurate, and heavy metal pollution in the midstream and downstream is much more serious than that in the upstream. Principal component analysis-multiple linear regressions (PCA-MLR) and positive matrix factorization (PMF) methods were used to quantitatively identify pollution sources. The coefficient of determination (R2) of PMF is closer to 1, and the analyzed pollution source is more refined. Furthermore, the result of source identification was imported into the health risk assessment to calculate the hazard index (HI) and carcinogenic risk (CR) of various pollution sources. The results showed that the HI and CR of As and Ni to local residents were serious in the Beiyun River. Industrial activities (23.0%) are considered to be the largest contribution of heavy metals in Beiyun River, followed by traffic source (17%), agricultural source (16%), and atmospheric deposition (16%). The source-oriented risk assessment indicated that the largest contribution of HI and CR is agricultural source in the Beiyun River, followed by industrial activities. This study provides a "target" for the precise control of pollution sources, which is of great significance for improving the fine management of the water environment in the basin.

Components and structural characteristics of dissolved organic matter in the overlying water of the Beiyun River

The components and structural characteristics of dissolved organic matter (DOM) in the overlying water were studied using various spectroscopy in Beiyun River. The relationship between the DOM composition and water quality was discussed. The result declared that the overall pollution of the Beiyun River was serious, and that the DOM content of the overlying water was between 9.60 and 28.70 mg/L. The DOM was mainly composed of humic-like substances (72.83%), proteins (9.49%), and microbial metabolites (17.68%). Furthermore, the structure and composition of DOM affected the nutrition level of river and reflected the water quality to some extent. Especially, the humification degree (SUVA254) of DOM can indirectly reflect the content of different types of nitrogen in the overlying water. Thus, some preliminary advice has been proposed to improve water quality by analyzing the content, composition and structural characteristics of DOM in the overlying water. These results offer novel ideas for the management of the Beiyun River.

Dissolved organic nitrogen structural and component changes in overlying water along urban river at molecular and material levels — Beiyun basin case study

The properties of dissolved organic nitrogen (DON) affect its stability in river ecosystems. This study is the first to evaluate DON by assessing its stability in the overlying water of an urban river. The results showed that CHON was the largest contributor (87.5%) to the DON, with the largest portion being molecules with one nitrogen atom. The DON in the overlying water of the Beiyun River is mainly composed of lignin (70.43%), following by protein (14.02%), carbohydrates (5.28%), and condensed aromatic (3.74%). Compared with other urban rivers, the higher protein content and lower lignin content of the Beiyun River increase the lability of the DON. From upstream to downstream, 53% of molecules are always stable in the river, most of them are lignin with highly oxidized functional groups. The comparison of stable and unstable components shows lipids and condensed aromatics are unstable and susceptible to degradation as compared with lignin. Molecules with a high H/C, low O/C, and double bond equivalent (DBE) were removed the fastest, while those with higher O/C and O/N were relatively stable. Flowing along the river, biological processes have contributed to the transformation of DON molecules from high-N into low-N molecules. Correlation analysis suggests that cutting off external pollutants can be helpful to control the nitrogen pollution of the Beiyun River.

Study on the Spatial and Temporal Distribution and Risk Assessment of PAHs between River and Groundwater - Take the Typical Section of Beijing North Canal as an Example

Pan, Z.H.; Li, B.H.; Yang, J.; Zhang, D.S.; Yang, Y., and Zhang, S.W., 2020. Study on the spatial and temporal distribution and risk assessment of PAHs between river and groundwater - Take the typical section of Beijing north canal as an example. In: Bai, X. and Zhou, H. (eds.), Advances in Water Resources, Environmental Protection, and Sustainable Development. Journal of Coastal Research, Special Issue No. 115, pp. 361-366. Coconut Creek (Florida), ISSN 0749-0208.Understanding the interaction of polycyclic aromatic hydrocarbons (PAHs) in river and groundwater is of great significance to the prevention and control of their pollution and to the protection of water resources. In order to study the interaction of PAHs in rivers and groundwater of different aquifers in Beiyun River Basin, here water samples were collected from rivers and groundwater in different periods, and the composition, content, temporal and spatial distribution characteristics of PAHs in rivers and groundwater were analyzed by correlation and difference analysis method. In addition, risk assessment was done by using risk entropy method. The results showed that the detection rate of 16 kinds of PAHs were about 100%, except benzo [a] pyrene and dibenzo [a, H] anthracene. Naphthalene was the main component, which was 1587.42ng/l, accounting for 85.6% of the total amount. In spring, the concentrations of PAHs were significantly lower than those in summer, and the concentration of 2-3-PAHs was higher than that of 4-PAHs. In general, the concentration of PAHs in the phreatic aquifer of the downstream reaches in the Beiyun River was higher than that in the upper reaches. According to the risk assessment data, the ecological risk of the study area was relatively low in different seasons and geographical conditions.

Characteristics and significance of dissolved organic matter in river sediments of extremely water-deficient basins: A Beiyun River case study

The characteristics of dissolved organic matter in river sediments, affected by microorganisms, are of great significance to water management strategies. Based on three-dimensional excitation and emission matrix fluorescence, ultraviolet–visible spectroscopy, and high-throughput sequencing technology, this study jointly analyzed the composition and transformation mechanisms of dissolved organic matter as well as the microbial community structure in sediments of the Beiyun River, the main river within a basin with extreme water shortages. Moreover, we evaluated N and P contents in sediments to identify parameters to reflect potential eutrophication risks. Our results demonstrated that the content of dissolved organic matter in sediments was between 30.2 and 49.9 g/kg in the Tongzhou area of the Beiyun River. Humic substances were the largest components of dissolved organic matter in the sediments, followed by protein-like substances and soluble microbial byproducts. Furthermore, the proportion of humic matter decreased from upstream to downstream. The proportion of carbonyl, carboxyl, hydroxyl, and ester substituents on the aromatic structures of dissolved organic matter was significantly higher in the upstream, whereas the proportion of substances with aliphatic chain substituents on their aromatic structures was relatively low. The variation in downstream sediment microbial communities was much greater than that in the upstream (analyzed at the phylum level). Proteobacteria was the most abundant phylum (47.97%), which was closely related to the aromaticity of the dissolved organic matter in sediments. The N and P contents in the sediments of the Beiyun River were high and exhibited active transformation. The maximum fluorescence intensity of fulvic-acid-like components in the sediments [Fmax(C4)] can indirectly reflect the potential risk of eutrophication in the Beiyun River. Therefore, our results provide a theoretical basis for the assessment of water quality and pollution control in the Beiyun River and other water-deficient regions worldwide.

Phosphorus transport in riverbed sediments and related adsorption and desorption characteristics in the Beiyun River, China

Riverbed sediments are the interface layer in riverine ecosystems connecting the overlying medium of water and the vadose zone. The transport behavior of phosphorus (P), which has been recognized as the primary cause of freshwater eutrophication, in riverbed sediments remains unclear. Understanding the impact of riverbed sediments on P transport is a necessary prerequisite for the development of appropriate strategies to reduce potential groundwater pollution. In this study, riverbed sediments were collected from the upstream, midstream, and downstream sections of the Beiyun River, China, and packed into vertical soil columns to perform leaching experiments to quantify P transport characteristics. In addition, the impact mechanisms were further explored by conducting laboratory batch tests of P adsorption and desorption. The results demonstrated that approximately 80% of P can be adsorbed by riverbed sediments in soil column leaching experiment, and a tailing phenomenon was observed in its desorption. The hydraulic conductivity properties of riverbed sediments were evaluated by the advection-dispersion equation, showing a gradually decreasing adsorption capacity for P from upstream to downstream sections, which was supported by the results obtained from adsorption–desorption thermodynamic and kinetic batch tests. The estimated annual leaching masses of P increased from 60.72 g/(m2 a) in the upstream section to 132.31 g/(m2 a) in the downstream section. The role of riverbed sediments as a source or sink of P is possibly determined by their coarse sand particles content, and the mean equilibrium P concentration (EPC0). The competitive relationship between P and other forms of nutrients also has an important influence on its source-sink role. These findings suggest that the prevention of the potential P leaching is most needed in the downstream sections of Beiyun River, and corresponding control strategies should be developed to avoid groundwater pollution.

Evaluating surface water quality using water quality index in Beiyun River, China.

The Beijing-Tianjin-Hebei urban agglomeration is one of the most water-scarce regions in China, because of the frequent human activities. Water scarcity and pollution have weakened the service functions of water ecosystems and hindered the regional economic development. As the "lifeline" of the economic development of Beijing-Tianjin-Hebei region, the water quality of Beiyun River has been widely concerned. River water quality assessment is one of the most important aspects to enhance water resources management plans. Water quality index (WQI), as one of the most frequently used evaluation tools, was used to comprehensively analyze the water quality in the Beiyun River. Between January 2017 and October 2018, we collected samples from 16 typical sampling sites along the main rivers of the watershed, covering four seasons. Seventeen water quality parameters, including temperature, pH, conductivity, dissolved oxygen (DO), chemical oxygen demand (COD), biochemical oxygen demand (BOD5), ammonia nitrogen (NH3-N), total phosphorus (TP), oil, volatile phenol (VP), fluoride, sulfide, surfactant, lead (Pb), copper (Cu), zinc (Zn), and arsenic (As), were used to calculate WQI. The average WQI values of Beiyun River in winter, spring, summer, and autumn were 88.15, 71.70, 78.92, and 90.12, respectively, explaining the water quality was "good" generally. There were significant differences in the spatial distribution of WQI values from Beiyun River, and water quality of upstream and downstream was better than that of midstream. In addition, correlation analysis was applied to explore the correlation between land use types and water quality. Water quality was significant negatively correlated with agriculture land and rural residential land, and a positive relationship between urban land and water quality. Generally, we believe that people's related activities on different land use are major elements impacting the water quality. Water environment improvement ought to increase the wastewater collection rate and sewage treatment capacity in rural areas, especially in the midstream of the Beiyun River. Graphical abstract.

Spatiotemporal variability and key influencing factors of river fecal coliform within a typical complex watershed

Fecal coliform bacteria are a key indicator of human health risks; however, the spatiotemporal variability and key influencing factors of river fecal coliform have yet to be explored in a rural-suburban-urban watershed with multiple land uses. In this study, the fecal coliform concentrations in 21 river sections were monitored for 20 months, and 441 samples were analyzed. Multivariable regressions were used to evaluate the spatiotemporal dynamics of fecal coliform. The results showed that spatial differences were mainly dominated by urbanization level, and environmental factors could explain the temporal dynamics of fecal coliform in different urban patterns except in areas with high urbanization levels. Reducing suspended solids is a direct way to manage fecal coliform in the Beiyun River when the natural factors are difficulty to change, such as temperature and solar radiation. The export of fecal coliform from urban areas showed a quick and sensitive response to rainfall events and increased dozens of times in the short term. Landscape patterns, such as the fragmentation of impervious surfaces and the overall landscape, were identified as key factors influencing urban non-point source bacteria. The results obtained from this study will provide insight into the management of river fecal pollution.

Calculation of ecological water requirements of urban rivers using a hydrological model: A case study of Beiyun River

The impacts of human activity lead to uncertainty and ambiguity when ecological water requirements (EWRs) are calculated based entirely on the current hydrological conditions of urban rivers, and the requirements for meeting the rivers’ function will also be uncertain. Human activity and river function goals are important factors affecting EWRs. This paper discusses the definition of urban river EWRs and the uncertainties in the results of the calculation, and proposes a calculation method for urban river EWRs that is independent of human activity. The Beiyun River Basin, China, was selected for a case study. The EWRs of the Beiyun River were calculated by combining a precipitation frequency curve with a distributed hydrological model. The rationality of the calculated results was verified using the Tennant method and an evaporation plus seepage calculation for the river. The results of the calculation for the urban river EWRs method proposed in this paper are unique, and the total amount is not affected by human activities. With respect to wet, normal, and dry precipitation frequencies, the minimum, suitable, and ideal EWRs of the Beiyun River are 1.48 × 108 m3, 2.79 × 108 m3, and 3.57 × 108 m3, respectively. The research conclusions are of great significance for the objective determination of the EWRs of urban rivers, and for promoting the appropriate planning and development of urban water.

Quantitative assessment of groundwater pollution risk in reclaimed water irrigation areas of northern China

The application of reclaimed water for agricultural irrigation can effectively reduce the use of freshwater resources including groundwater, addressing the increasingly severe challenge of water shortage. However, reclaimed water irrigation will cause potential pollution risks to groundwater, which needs to be further studied to ensure the safety of reclaimed water irrigation. An integrated quantitative assessment system including the modified DRASTIC model was developed to evaluate the pollution risks caused by reclaimed water irrigation and scientific strategies were offered for the development of reclaimed water irrigation in water shortage areas to avoid groundwater pollution. The groundwater intrinsic vulnerability index, the hazards of the characteristic pollutants, and the groundwater values were quantified to obtain the pollution risks distribution map. In the Beijing plain of north China, the low groundwater pollution risk areas were located in the midstream of Chaobai river baisin, Beiyun river basin, and Yongding river basin, accounting for 48.3% of the total study area. These areas in low pollution risk can be considered as safety areas for reclaimed water irrigation. The moderate groundwater pollution risk areas accounting for 46.9% of the total study area were suggested to apply water-saving irrigation measures for preventing groundwater pollution. The reclaimed water irrigation should be prohibited in the high groundwater pollution risk areas, which accounted for 4.8% of the total study area. This study highlights the reasonable strategy for the development of reclaimed water irrigation in water shortage areas and lay a foundation for finding alternative water sources for agricultural irrigation.

Distribution and ecological risk of substituted and parent polycyclic aromatic hydrocarbons in surface waters of the Bai, Chao, and Chaobai rivers in northern China

Like their parent polycyclic aromatic hydrocarbons (PAHs), substituted polycyclic aromatic hydrocarbons (SPAHs), including methyl PAHs (MPAHs), oxygenated PAHs (OPAHs), and chlorinated PAHs (ClPAHs), exist ubiquitously in urban and agricultural rivers. Although laboratory studies have found the biological toxicities of certain SPAHs to be higher than that of their parent PAHs, the ecological risk of SPAHs in rivers has been largely ignored. Here, we studied the distribution, source and transport of PAHs and SPAHs as well as ecological risks in the Chaobai River System, which experiences a high level of anthropogenic activity. The results show that the concentration of ΣOPAHs (321 ± 651 ng/L) was higher than that of ΣPAHs (158 ± 105 ng/L), ΣMPAHs (28 ± 22 ng/L), and ΣClPAHs (30 ± 12 ng/L). We also found that (S)PAHs in Chaobai River mainly originated from Beiyun River (53%–65%), which receives considerable municipal wastewater treatment plant effluent from Beijing. The major transport pathway of (S)PAHs from Chaobai River was likely for irrigation (83%–86%) and transportation into Yongdingxin River (13%–16%), which finally merged into the Bohai Sea. The mixed chronic risk of (S)PAHs (risk quotient = 45 ± 53) was higher than the mixed acute risk (risk quotient = 1.9 ± 1.4), with all sites facing chronic risk and 90% of sites experiencing acute risk. Although the chronic and acute risks of (S)PAHs to plants, invertebrates, and vertebrates were mainly from PAHs (97.5% to chronic risk and 96.5% to acute), SPAHs still posed a chronic risk to invertebrates and vertebrates (risk quotient > 1). Accordingly, the ecological risk of (S)PAHs in Chaobai River should be taken into consideration for ecosystem protection. The transmission of PAHs and SPAHs from Chaobai River may also pose potential risks to farmland through irrigation, as well as to the Bohai Sea via river water discharge.

Spatiotemporal Dynamics of Water Yield Service and Its Response to Urbanisation in the Beiyun River Basin, Beijing

Water-related ecosystem services are vitally important for growing mega-cities. However, accelerating urbanisation has brought many associated issues, such as rapid population growth, extensive land occupation and landscape pattern changes, which affect both the functions and services of regional ecosystems. To achieve sustainable urban ecological development, it is necessary to determine the impacts of urbanisation on water yield. In this study, the water yield ecosystem service of the Beiyun River Basin in Beijing was simulated by the Integrated Valuation of Ecosystem Services and Trade-offs (InVEST) model and the Geographical Detector method (Geo-detector) was applied to obtain the contributions and temporal regularity of urbanisation impacts on water yield. The results indicated the following: (1) the water yield of the Beiyun River Basin increased from 9.52 × 108 m3 in 2000 to 12.84 × 108 m3 in 2010, with a growth rate of 34.9%; (2) the urbanisation level of the Beiyun River Basin increased from 2000 to 2010, and the selected five landscape indexes varied greatly with the continuously increasing patch density (PD), splitting index (SPLIT) and Shannon’s diversity index (SHDI); (3) during this decade, patch richness density (PRD), SHDI, aggregation index (AI), portion of construction land (CL) and average annual precipitation (AP) were the influencing factors that continuously contributed more than 30% of the spatial variability of water yield in the Beiyun River Basin; and (4) the explanatory power of the interaction between any two driving forces was greater than any single factor. Our results could provide scientific references and constructive advice for city water resource operation from a landscape perspective.

Risk assessment of soil heavy metals associated with land use variations in the riparian zones of a typical urban river gradient

Urbanization-induced land use changes in riparian area alter soil and water regimes in complex ways, which may also affect the migration and transformation of soil heavy metals and increase the risk of release. In this study, soil samples from the riparian zone of Beiyun River, which located in the rapidly urbanized Beijing metropolis, were collected and analyzed for heavy metals (As, Cd, Cr, Cu, Mn, Ni, Pb, and Zn). Then their zoning distribution pattern along river (section 1 to section 4 from upper to low reaches) and the correlation of heavy metals between riparian soils and riverine sediments were investigated. Results showed that the average soil heavy metal concentrations of Cd, Cr, Cu and Zn in riparian zone were approximately 2.2, 1.7, 1.9 and 2.0 times higher than the background values. Sectionally, the concentrations of Cd, Ni, Pb and Zn displayed a decreasing order with section 2 > section 3 > section 4 > section 1, while the highest values of Cr and Cu were found in section 3. The concentrations of all heavy metals except Cr in artificial garden land were higher than those in other land use types, and the concentrations of Cr among five land use types were in the order of grass land > farmland > artificial garden land > forest land > forest-grass land. Generally, most of the heavy metals in the riverine sediments had higher contents than those in riparian zones, especially Cu and Zn. There was a decreasing order for the average geo-accumulation index (Igeo) of measured heavy metals in the soils of riparian zone: Zn (0.15) > Cr (0.08) > Cu (0.07) > Cd (−0.08) > As (−0.57) > Pb (−0.67) > Mn (−0.75) > Ni (−0.86), whereas they had different “high-low” orders in different land use types. The Igeo index indicated most regions of riparian zone were moderately polluted with Cd, Cr, Cu and Zn, especially in grass land and forest land. Also, Cd, Cr and Zn in riparian zone have positive relationships with the concentrations in riverine sediments. Health risk assessment showed that the contribution of ingestion HQ to HI was the highest among the three exposure pathways (ingestion, inhalation and dermal contact), and children had higher non-carcinogenic risk and carcinogenic risk index than adult. Our findings suggest that land use and soil in riparian zone should be protected and managed scientifically to control the riverine pollution and ensure human health.

Pollution Characteristics and Health Risk Assessment of Microorganism Pollutions in the Beiyun River

Microorganism pollution in rivers is of great importance to the protection of watershed water quality and public health management. As a typical watershed of the Haihe River watershed, the Beiyun River was chosen as the study area, and the characteristics and health risk of microorganism pollution were assessed from a comprehensive perspective. The results showed that the microbial contamination of the fecal sources was serious during the wet season, and the microbial amount at most river sections was more than 105 MPN·L-1. During the normal season and dry season, the microbial amount was approximately 103-105 MPN·L-1. Therefore, no obvious change could be observed. The fecal pollution in the agricultural river sections was the most severe, and the water quality of over 60% of these river sections was below the state Grade V level. The fecal microbial biomass of some urban river sections increased from 103 MPN·L-1 to 106MPN·L-1 after the rainfall event, indicating an obvious change of fecal microbial pollution during the rainfall process. For the Beiyun River, the exposure risk of the fecal microbial biomass was mainly between 0.015-0.035, while the Lianhua River, Macao River, lower reaches of Qinghe River, and lower reaches of Wenyu River were hotspots for contamination. Greater attention should be paid to these areas.

COD&lt;sub&gt;Cr&lt;/sub&gt; degradation coefficient of urban river recharged with reclaimed water and its impacting factors

化学需氧量（COD）是影响地表水体水质的主要污染指标.明确地表水中COD的降解系数，可为把握有机物污染过程变化以及有效控制污染提供科学依据.北运河是城市再生水河流，COD污染严重.以北运河从上游至下游的5个典型断面（马坊桥、火沙路、东关大桥、榆林庄桥、杨洼闸）为例，通过室内模拟实验，估算了不同断面COD_Cr降解系数，并对COD_Cr降解系数进行校正；测定了颗粒物沉降速率、复氧系数，评估了水体自净能力；分析了不同环境条件（温度、溶解氧、流速）对COD_Cr的降解影响.结论如下：北运河水体自净能力较差，颗粒物沉降速率范围为1.09~3.22 m/d，杨洼闸断面颗粒物沉降速率最低为1.09 m/d，其复氧系数偏低，为0.016 d^-1.北运河水体COD_Cr降解系数符合一级动力学方程；经水力、温度经验公式校正后，COD_Cr降解系数范围为0.0184~0.0883 d^-1，低于我国其他平原地区河流.北运河COD_Cr降解系数存在明显的空间差异性，上游断面的降解系数高于下游断面，不过下游北京界最后出水断面杨洼闸表现出闸坝特殊性，降解系数最高（0.0416~0.0883 d^-1）.水质参数中温度、溶解氧、氧化还原电位、营养盐以及总有机碳是COD_Cr降解系数的主要影响因子.COD_Cr降解系数随着温度、溶解氧、外源动力增加而增大；COD_Cr降解系数与营养盐、TOC呈显著正相关，与氧化还原电位呈显著负相关.研究结果可为我国相关城市再生水体水质改善和城市黑臭水体治理提供科学依据.;Chemical oxygen demand (COD) is one of the major indicators of surface water pollution in China. Degradation coefficient of pollutant may provide scientific basis for understanding the process of organic polluter change and effective pollution control. As a typical urban river recharged with reclaimed water, Beiyun River is at very serious state of COD pollution. In this research, five typical sections from upstream to downstream (Mafang Bridge, Huosha Road, Dongguan Bridge, Yulinzhuang Bridge and Yangwa Sluice) on Beiyun River were selected for estimating COD_Cr degradation coefficients and calibration by laboratory simulation experiments. Taking the section of Yangwa sluice as a typical example, the sedimentation rate and reoxygenation coefficient were measured on site to evaluate water self-purification ability. Then the impacts of different environmental factors (temperature, dissolved oxygen and flow rate) on COD_Cr degradation were discussed based on laboratory simulation experiments. The conclusions were summarized as follows:The water purifying ability of Beiyun River was very low. The sedimentation rates ranged from 1.59 to 3.22 m/d, among which, the lowest rate was in Yangwa Sluice with a reoxygenation coefficient of 0.016 d^-1. The variation of COD_Cr degradation coefficients conformed to the first-order kinetic equation, ranging from 0.0184 d^-1 to 0.0883 d^-1 corrected by the hydraulic and temperature condition. The COD_Cr degradation coefficients showed significant spatial variation. The degradation coefficients of upstream sections was higher than that of downstream sections, except Yangwa Sluice (last section of Beijing at downstream) as the highest (0.0416-0.0883 d^-1), showing the characteristics of the sluice. Water quality parameters such as temperature, dissolved oxygen, redox potential (ORP), nutrients, and total organic carbon (TOC) were the main influence factors. The COD_Cr degradation coefficients increased with the temperature, dissolved oxygen and flow rate. In addition, COD_Cr degradation coefficient was positively related to nutrients and TOC, but negatively to ORP. The results of this study can provide a scientific reference for urban river improvement and pollution control.