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1.
Reimer Herrmann 《CATENA》1981,8(2):171-189
The load of 3.4-benzopyrene in storm drains of an urban watershed is linked to the load of suspended sediments because of the high partition coefficient. The strong influence of the antecedant weather conditions on 3.4-benzopyrene washoff indicates a 'supply limiting watershed' (SUTHERLAND 1978). After strong antecedant rainfall and low flow rates of the storm under consideration the concentrations of 3.4-benzopyrene in rainfall and storm run-off are not significantly different from each other. Compared with a wateshed with an old combined sewer system, which can be described as ‘transport limiting’, a higher washoff intensity is needed to result in the same 3.4-benzopyrene load.  相似文献   

2.
Sediment transport in the Ribera Salada stream was estimated from continuous suspended and bedload monitoring between 2005 and 2008. The Ribera Salada basin is a mountainous perennial river in the Southern Pyrenees and is representative of the extensive forestry land use in this upland region. Water and sediment fluxes have been analysed with the aim of determining the thresholds, duration, ranges and relative contributions of the two sediment transport modes (suspended and bedload), and their variability in relation to the basin's annual hydrology. The stream's hydrology in the first two sampling years was average in the context of a 10-yr series of the basin, while 2007–2008 can be classified as a wet year. The specific total sediment load during the study period amounted to 12 t km−2y−1, a low value compared with similar Mediterranean counterparts. The maximum load (31.5 t km−2y−1) was observed during the wettest year of the monitoring programme. During average years most of the total load (> 90%) was transported in suspension; consequently, suspended sediment transport is more frequent through time. In contrast, bedload occurs sporadically during floods that exceed certain hydraulic thresholds, corresponding to a flow equalled or exceeded 4% of the time, that yields an average shear stress of ∼ 35 N m−2. Under such conditions bedload transport becomes relevant and, if the threshold is frequently exceeded as in relatively wet years such as 2007–2008, may constitute the majority of the total sediment load (74%). This paper provides new evidence of the distinct role of sediment transport modes in stable fluvial environments where only sporadic inputs of surplus energy (flow discharge) determine the dominant mode, magnitude and duration of their respective contribution.  相似文献   

3.
以长江干流寸滩水文站以上流域为研究对象,基于1953-2018年的实测水沙资料,采用线性回归、Mann-Kendall趋势检验和水沙关系曲线分析径流、输沙的时间趋势及其关系变化,并采用双累积曲线法分析水沙变化的驱动因素。结果表明:寸滩站以上流域多年平均径流量为3425亿m^3,多年平均输沙量为3.61亿t;多年平均月径流量为294.8亿m^3,多年平均月输沙量为3013万t,且主要分布在6-10月,分别占年径流泥沙总量的70%和95%以上。趋势分析显示,流域年降雨量和径流量变化趋势不明显,年输沙量呈极显著减小趋势;月径流量在1-4月显著增加,其他月份变化不显著,而各月输沙量均呈显著减少趋势。水沙关系曲线均可用幂函数拟合,拟合参数受时间尺度影响,统计检验显示悬移质输沙量实测值与水沙关系曲线的估算值差异不显著。双累积曲线分析发现水利工程建设和水土保持等人类活动是寸滩水文站输沙减少的主要原因,其作用占69%~93%,其中2000年以来人类活动的贡献超过90%。  相似文献   

4.
The distribution of Polycyclic Aromatic Hydrocarbons (PAHs) was investigated in surface runoff and sediments of Lagos, Osogbo and Ile-Ife Western areas of Nigeria. Method for the analysis of PAHs was based on Liquid-Liquid extraction of the runoff and a soxhlet extraction of the sediments followed by a clean up adsorption procedure. The PAHs were separated and quantified by Gas Chromatography-Mass spectrometry (GC-MS) technique. A blank experiment was done using triply distilled water and following the same procedure for the samples to establish blank levels. In both street runoff and sediments 13 PAHs were identified and quantified. At Osogbo and Ile-Ife areas, the mean levels of PAHs in surface runoff ranged between 0.10–15.81 mg L-1 while in the Lagos area the levels were between 0.1–73.72 mg L-1. Generally, the PAH levels in surface runoff of Lagos constitute 53.03 mg L-1 average ∑ PAH detected in the study area compared to 31.96 mg L-1 average ∑ PAH contribution made by samples from Osogbo and Ile-Ife. The levels of PAHs in sediments are relatively higher compared to those of the street runoff in the study area. PAHs in sediment of Lagos contribute an average of 228.57 mg kg-1 ∑ PAH to the total sediment PAH burden compared to Osogbo and Ile-Ife areas that contribute only 91.13 mg kg-1 average ∑ PAH to the total PAH burden of the study area. The relatively higher average ∑ PAHs reported for Lagos area compared with those of Osogbo and Ile-Ife, is consistent with higher industrial activities and traffic density of the former (1000–10000 vehicles/hr) than the later (450–1500 vehicles/hr).  相似文献   

5.
为了明确极端暴雨下不同尺度流域的产流产沙特征,为应对极端暴雨事件提供技术支撑。基于2019年9号台风“利奇马”导致的暴雨洪水事件,采用暴雨中心的辛庄控制站和弥河干流黄山水文站的水文数据,分析了本次暴雨中两个不同尺度流域的径流、泥沙总量及过程特征。结果表明:2019年8月10—17日,辛庄观测站次洪水径流总量为123万m3,实测洪峰为40.96 m3/s,洪水泥沙总量为4600 t,产沙模数为1285 t/km2。黄山水文站实测洪峰流量为2210 m3/s,是自1988年建站以来的最大流量,重现期为33.3年一遇。黄山水文站输沙量为36.23万t,输沙模数为966 t/km2。本次暴雨洪水的输沙量是多年平均输沙量(19.50万t)的1.65倍,与2018年夏季汛期洪水泥沙过程的水沙关系曲线相关性较好。综上,基于水沙关系的黄山水文站流域场次洪水输沙量预测方法是准确的,说明在极端暴雨事件中采用历史洪水泥沙关系预测输沙量是可行的。  相似文献   

6.
The impact of storm water runoff on a small urban stream   总被引：2，自引：0，他引：2  
Background, aim, and scope  In urban areas, storm water runoff often transports various pollutants, some of which settle and form sediments. In order to have the comprehensive view of the ecological state of storm water runoff recipients, both water and sediments of the stream must be assessed. In the Baltic Sea Area, the Water Framework Directive & HELCOM Recommendations aim to prevent or minimise pollution caused by harmful substances arising from storm water runoff, in order to promote the ecological restoration of the Baltic Sea—one of the most vulnerable seas. The aim of the study was to investigate the toxicity of bottom sediments of a small storm water runoff recipient focusing on the potential impact of successive discharges of urban storm water. Some storm water runoff quality parameters and the toxicity of bottom sediments of recipients was studied in this research. Materials and methods  During 9 years, at four discharge points, minimum four grab samples per year at each discharge point were taken for chemical characterisation. General parameters (pH, SS, BOD7, CODCr and TPH) in liquid phase samples were analysed according to standard methods. Annual limit values were taken from the Lithuanian EPA requirements for the management of storm water runoff with a focus on prevention and control of contamination. Eleven composite samples of stream bottom sediments, each consisting of ten sub-samples, were collected in 2006. Toxicity screening from sediments was performed using the plant Lepidium sativum according to modified I. Magone’s methodology (Magone I, Bioindication of phytotoxicity of transport emission. In: Kachalova O-L, Zinatne (eds) Bioindication of toxicity of transport emissions in the impact of highway emissions on natural environment. Riga, pp 108–116, 1989). The level of toxic impact of Lepidium sativum (compared to control) was assessed according to the modified method of Wang (Rev Environ Contam Toxicol 126:88–127, 1992). Results  The mean pH of urban storm water runoff does not vary much from neutral, but range values are quite different, from 4.0 up to 8.7. The highest concentration of SS reached 800 mg L−1, TPH—2.4 mg L−1, BOD7—300 mg O2 L−1 and CODCr—1,400 mg L−1. The SS was above the limit in 64% of total amount of grab samples, TPH—37%, BOD7—41% and CODCr—55%. The toxicity analysis of the bottom sediments showed varying toxicity of bottom sediments along the stream. From nine analysed samples of bottom sediments, 30% had weak toxicity, 30% medium and 30% strong toxicity on the test organism plant L. sativum. There was one single sample with no toxic effects, so that the results showed that urban storm water has an unacceptable environmental impact on recipients. It was also indicated that storm water runoff discharge alone is not the potential source of toxicity of bottom sediments. The litter demonstrated a weak toxicity of bottom sediments as well. Discussion  Most local authorities do not consider storm water runoff discharges to be a matter of great concern because they believe that surface runoff arising from rainfall is still relatively clean. The study showed that the current method of monitoring storm water runoff quality by chemical analyses is not the best tool for environmental impact assessment and must be combined with toxicity tests of bottom sediments of recipients. Recommendations and perspectives  To avoid the environmental impact of storm water runoff more attention should be paid to the development and implementation of storm water runoff pollution prevention measures. The study implies that future research concerning the relationships between storm water runoff deposit characteristics and biological activities must be developed to evaluate the contamination potential of stream sediment deposits for local aquatic ecosystems. Further studies should be developed to characterise the activities of the microbial community of storm water runoff sediments, and to monitor bioremediation in situ.  相似文献   

7.
Suspended sediment load was analyzed in a small, high-gradient stream of the Eastern Italian Alps which was instrumented to measure discharge and sediment transport. The ratio of suspended to total sediment yield and the relations between sediment concentration and water discharge were analyzed for seven floods which occurred from 1991 to 1996 in summer and autumn (from June to October). Different patterns of hysteresis in the relation between suspended sediment and discharge were related to types and locations of active sediment sources. The within-storm variation of particle size of suspended sediment during a major flood indicates a coarsening of transported material for increasing discharge. An analysis of grain size has shown that erosion areas on hillslopes were the main sources of suspended load.  相似文献   

8.
This paper examines whether multiple regression analysis and neural network models can be applied successfully for the indirect prediction of the runoff treatment performance with water quality indicator variables in an experimental storm water detention system rig. Five biologically mature experimental storm water detention systems with different designs treating concentrated gully pot liquor (spiked with dog droppings) were assessed. The systems were located on The King’s Buildings campus at The University of Edinburgh and were monitored for a period of 18 months. Multiple regression analyses indicated a relatively successful prediction of the biochemical oxygen demand and total suspended solids for most systems, but due to a relatively weak correlation between the predictors and both microbial indicators, multiple regression analyses were not applied for the prediction of intestinal enterococci and total coliform colony-forming units. However, artificial neural network models predicted microbial counts relatively well for most detention systems.  相似文献   

9.
Storm event and annual export of suspended sediment (SS) and particulate phosphorus (PP) was measured during three hydrological years (June 1993 to May 1996) in Gelbæk stream, a Danish lowland stream draining a 11.6 km2 arable catchment area. The contribution of subsurface drainage water, surface runoff and stream bank and bed erosion to catchment SS and PP losses was estimated using three different strategies: 1) Simultaneous and comparative monitoring of subsurface water. 2) A mass-balance and budget approach dividing the Gelbæk catchment into two subcatchments. 3) Application of the fingerprinting technique to single storm events. Subsurface drainage water proved to be a significant SS and PP source. Subsurface drainage water from half of the catchment area accounted for 9.8–15% of the total annual SS loss from the Gelbæ catchment and 9.6–18.2%, of the annual PP loss. The mass-balance and budget approach showed stream bank and bed erosion to be the major source of SS and PP in this channelized and highly managed lowland stream. These findings were consistent with the fact that the annual loss of SS and PP from an upper culverted stream sub-catchment was significantly lower than that estimated from a mass-balance for a lower sub-catchment with an open stream channel. Comparison of the tracer content (e.g.117Cs) of SS collected during four storm events with that of topsoil and subsoil using a simple mixing model revealed subsoil to be a major source of SS.  相似文献   

10.
Purpose

Rain storm events mobilise large proportions of fine sediments in catchment systems. Sediments from agricultural catchments are often adsorbed by nutrients, heavy metals and other (in)organic pollutants that may impact downstream environments. To mitigate erosion, sediment transport and associated pollutant transport, it is crucial to know the origin of the sediment that is found in the drainage system, and therefore, it is important to understand catchment sediment dynamics throughout the continuity of runoff events.

Materials and methods

To assess the impact of the state of a catchment on the transport of fine suspended sediment to catchment outlets, an algorithm has been developed which classifies rain storm events into simple (clockwise, counter-clockwise) and compound (figure-of-eight; complex) events. This algorithm is the first tool that uses all available discharge and suspended sediment data and analyses these data automatically. A total of 797 runoff events from three experimental watersheds in Navarre (Spain) were analysed with the help of long-term, high-resolution discharge and sediment data that was collected between 2000 and 2014.

Results and discussion

Morphological complexity and in-stream vegetation structures acted as disconnecting landscape features which caused storage of sediment along the transport cascade. The occurrence of sediment storage along transport paths was therefore responsible for clockwise hysteresis due to the availability of in-stream sediment which could cause the “first flush” affect. Conversely, the catchment with steeper channel gradients and a lower stream density showed much more counter-clockwise hysteresis due to better downstream and lateral surface hydrological connectivity. In this research, hydrological connectivity is defined as the actual and potential transfer paths in a catchment. The classification of event SSC-Q hysteresis provided a seasonal benchmark value to which catchment managers can compare runoff events in order to understand the origin and locations of suspended sediment in the catchment.

Conclusions

A new algorithm uses all available discharge and suspended sediment data to assess catchment sediment dynamics. From these analyses, the catchment connectivity can be assessed which is useful to develop catchment land management.

  相似文献   

11.
以长江干流寸滩水文站以上流域为研究对象,基于1953-2018年的实测水沙资料,采用线性回归、Mann-Kendall趋势检验和水沙关系曲线分析径流、输沙的时间趋势及其关系变化,并采用双累积曲线法分析水沙变化的驱动因素。结果表明：寸滩站以上流域多年平均径流量为3 425亿m3,多年平均输沙量为3.61亿t;多年平均月径流量为294.8亿m3,多年平均月输沙量为3 013万t,且主要分布在6-10月,分别占年径流泥沙总量的70%和95%以上。趋势分析显示,流域年降雨量和径流量变化趋势不明显,年输沙量呈极显著减小趋势;月径流量在1-4月显著增加,其他月份变化不显著,而各月输沙量均呈显著减少趋势。水沙关系曲线均可用幂函数拟合,拟合参数受时间尺度影响,统计检验显示悬移质输沙量实测值与水沙关系曲线的估算值差异不显著。双累积曲线分析发现水利工程建设和水土保持等人类活动是寸滩水文站输沙减少的主要原因,其作用占69%~93%,其中2000年以来人类活动的贡献超过90%。  相似文献   

12.
Nonpoint stormwater runoff remains a major threat to surface water quality in the USA. More effective stormwater control measures can be designed by understanding patterns in pollutant export with respect to the runoff hydrograph. In particular, nutrient concentrations in urban stormwater can cause deleterious effects in sensitive watersheds in the Southeast and Mid-Atlantic USA. A year-long study captured stormwater samples from 36 storm events at two catchments (one primarily impermeable and the other substantially wooded) and analyzed for total suspended solids and various nutrient species. Using these data, the first flush effect (the assumption that the initial portion of a rainfall-runoff event is more polluted than the later portions) was evaluated based on several published methods and definitions. Based on an analysis of multiple methodologies, the ranking of first flush strength among the pollutants was total suspended solids (TSS) > ammonia (NH3) > total Kjeldahl nitrogen > NO2-NO3 > total phosphorus > orthophosphate (O-PO4). Nitrogen species generally displayed a stronger first flush than phosphorus species, with O-PO4 showing the weakest first flush effect. Various relationships ° climate, land use, and the first flush strength were also explored. Of the rainfall characteristics analyzed, total rainfall and runoff volume each inversely affected the first flush strength of TSS on the more impervious catchment. Although orthophosphate did not have a strong first flush effect, the relative first flush strength for O-PO4 increased with increasing rainfall or runoff. Land use did not influence the first flush strength of the pollutants. On average, most pollutants exhibited a slight first flush effect, but substantial pollutant loading still occurred in the latter portion of the storm??s total runoff volume. Thus, treating the majority of a storm??s total pollutant load requires capturing a commensurate fraction of runoff volume.  相似文献   

13.
Pinpointing erosional ‘hot spots’ or sediment source areas within a watershed can be difficult because of the highly non-linear and episodic nature of effective runoff and sediment transport. Continuous monitoring of stream networks can provide insight into sediment source areas not possible from routine sampling by capturing episodic events and integrating entire storm events. This paper presents the results of a three-year study of spring snowmelt runoff in watersheds of Lake Tahoe, California, USA, using a network of nine nephelometric turbidometers. We estimate that montane badlands, comprising 1.2% of the Ward Creek watershed (25 km2), contributed 10–39% of snowmelt-derived suspended sediment load. The badlands are comprised of poorly-vegetated and deeply-incised gullies formed in parent material of Miocene volcanic mudflow breccia. The larger (29.5 km2) Blackwood Creek watershed also showed high relative erosion rates from volcanic terrain. Tributaries draining forested granitic and metasedimentary headwater regions had minimal sediment loads. Monitoring networks indicated that temporary main channel storage regulated release of fine sediment eroded from steep headwater slopes. This lag between erosion and delivery may lead to underestimation of gully erosion contribution to sediment budgets.  相似文献   

14.
There are few studies that relate the timing and amounts of pesticide washoff from plant foliage during rainfall to runoff losses at the edge of the field. We hypothesized that foliar deposits, if washed onto the soil slowly during rainfall, may then undergo less leaching during the period of infiltration that occurs prior to soil saturation and runoff, thus exhibiting larger runoff losses than pesticides on/in the soil at the beginning of rain. We measured the runoff of ethalfluralin, metolachlor, chlorothalonil, and rhodamine WT dye using simulated rainfall on 450 m2 mesoplots planted in peanut. Ethalfluralin was applied preplant incorporated, and metolachlor was applied preemergence on bare soil. Chlorothalonil and rhodamine WT were applied to the peanut canopy at maturity. Rainfall was simulated 24 h after each chemical application (in May and July, 1998, and May and August, 1999) using raindrop sprinklers, applying 5.5 +/- 0.5 cm over a 2 h period to create reasonable worst-case conditions; between 3 and 9 mm of runoff was generated. Volume-weighted average concentrations of chemicals in runoff were 7, 104, 163, and 179 ug L(-1) for ethalfluralin, metolachlor, chlorothalonil, and rhodamine WT, respectively. The total amounts of chemicals lost in the runoff events were 0.04 +/- 0.01, 0.2 +/- 0.1, 0.6 +/- 0.5, and 0.2 +/- 0.1, as percents of amounts applied, respectively. Rhodamine WT formed a vivid red solution on wetting and provided visual clues to the dynamics of chemical washoff/runoff. The washoff from rain-exposed peanut foliage appeared to be complete within a few minutes of the beginning of rainfall, and disappearance of dye from rain-exposed soil surface occurred within the first 10 min of rainfall. However, dye was present in runoff water at near-constant concentrations throughout the 2 h runoff event, indicating that near-constant amounts of chemical remained in the soil extraction zone. These results confirm earlier studies showing that soil incorporation at application significantly reduces runoff losses and that a majority of foliar residues can be washable if rainfall occurs within a few days after application. Runoff losses of foliar-applied pesticides were small relative to washoff amounts but were sensitive to runoff timing relative to washoff.  相似文献   

15.
Data pertaining to the transport of fluvial sediment sampled in detail during a five hour long event in a small upland stream channel in the extremely arid Southern Negev are presented. Considerations based on comparative evaluations of water discharge, stream power, total and fractional sediment concentration, and total and fractional sediment discharge suggest that bedload transport in channels of even very small upland catchments practically devoid of continuous alluvial cover takes place in waves, which are not a priori related to any water discharge characteristic, but rather reflect some intrinsic feature of watershed dynamics, such as slope-channel topographic contrasts or fluvial bifurcation. The regular spacing of pools and riffles and of gravel bars in the more alluvial reaches downstream may therefore be initiated from upstream.  相似文献   

16.
《CATENA》1999,36(3):171-190
  相似文献   

17.
The amounts of P forms transported in surface, accelerated subsurface, and subsurface runoff, and the stream draining a 20 ha area of a pasture watershed were measured for 3 yr. Stream-bank erosion and resuspension of stream sediment contributed the major proportion of the particulate P (PP), total P, and sediment transported annually in stream flow (86, 77, and 74%, respectively, in 1977). In addition, 29% of the annual dissolved inorganic P (DIP) loading of the stream in 1977 was attributed to the release of P from suspended in situ particulate material. Remarkably similar proportions of water, P forms, and sediment were contributed by the runoff types in each of the 3 yr of study. Subsurface runoff contributed the major proportion (67% in 1977) of stream flow. Although surface runoff contributed only a minor proportion of stream flow (11% in 1977), it contributed the major proportion of both DIP (32% in 1977) and PP loading (90% in 1977) compared with the other runoff types. Differences in the amounts of P forms transported in the three runoff types can be attributed to several factors, one of the most important being the time of contact between soluble P in runoff waters and soil components.  相似文献   

18.
珠海城区暴雨径流污染负荷估算及其评价   总被引：9，自引：0，他引：9       下载免费PDF全文
基于对广东珠海城区暴雨径流污染的监测,引用SCS模型对城区暴雨径流污染负荷进行估算并分析评价。结果表明,珠海城区暴雨产流年平均1529.2mm,其中以交通主干道和商业区径流量最大。暴雨径流污染物浓度水平较高,T—N,T—P,COD_(Cr)和BOD_5负荷总量分别为765.27,74.06,11 958.94和1104.71t,其中COD_(Cr)负荷为工业点源污染的72.32％,占珠海非点源污染总负荷的24.69％。暴雨径流在雨后短时间内会使受纳水体的水质迅速恶化。因此,珠海城区暴雨径流对水环境的威胁较大。  相似文献   

19.
Purpose

The purpose of this study was to evaluate the influence of suspended particulates on P loading captured during a single storm event. The Everglades Agricultural Area of Florida comprises 280,000 ha of organic soil farmland artificially drained by ditches, canals, and pumps. Phosphorus (P)-enriched suspended particulates in canals are susceptible to transport and can contribute significantly to the overall P loads in drainage water.

Materials and methods

A settling tank experiment was conducted to capture suspended particulates during tropical storm Isaac in 2012 from three farms approximately 2.4 to 3.6 km2 in size. Farm canal discharge water was collected in a series of two 200-L settling tanks over a 7-day drainage period, during tropical storm Isaac. Water from the settling tanks was siphoned through Imhoff settling cones, where the suspended particulates were allowed to settle and collected for P fractionation analyses, and compared to intact sediment cores collected from the canals.

Results and discussion

The discharged suspended particulates contained higher organic matter content, total P, and labile P fractions compared to the drainage canal sediments. Based on the equilibrium P concentrations, drainage canal sediments behave as a source of P to the water column. A 7-day continuous drainage event exported 4.7 to 11.1 t of suspended solids per farm, corresponding to 32 to 63 kg of particulate P being lost to downstream ecosystems. Drainage associated to this single 7-day storm event exported up to 61 % of the total annual farm P load.

Conclusions

It is evident from this study that short-term, high-intensity storm events can skew annual P loads due to the export of significantly higher suspended particulate matter from farm canals. Exported particulates rich in P, if captured and replenished back on farmlands, would be a sustainable farming practice that can provide a supplemental source of nutrients.

  相似文献   

20.
Nutrient (C, N and P) and metal (Cr, Cu, Ni, Pb and Zn) content and dynamics of suspended and channel bed sediments were analysed within the rural Attert River basin (Luxembourg). This basin is representative of the main physiographic characteristics of the country, where there is currently little information available on the composition and dynamics of fluvial sediment. Stream bed fine-grained sediment samples (n?=?139) collected during low flow conditions and time-integrated suspended sediment samples (n?=?183) collected during storm runoff events (October 2005 to April 2008) in seven nested basins ranging from 0.45 to 247?km2 were analysed. Nutrient and metal spatial patterns, temporal trends and the relationship between their content and storm runoff characteristics (e.g. maximum discharge and sediment concentration) were assessed. Results showed a high spatial and temporal variability, mainly associated with basin characteristics and local inputs. Higher values of total C were measured in the highly forested basins located in the northern part of the Attert River basin, whereas the highest values of total P were mainly associated with material coming from grassland and with the inflow of wastewater treatment plants (i.e. higher values of total P were measured in the southern part of the basin). The abundance of metals, not only in suspended but also in channel bed sediments, was generally as follows: Zn > Cr > Ni > Pb > Cu. Both nutrient and metal concentrations were at a maximum at the beginning of the wet season, after having been accumulated during the summer. These values tended to decrease during autumn and winter due to sediment mobilisation, and a higher flow capacity to transport coarser particle fractions from the sources. In general, concentrations of nutrients and metals on suspended sediment were negatively correlated with antecedent precipitation, total precipitation, total specific discharge and maximum discharge, which has been previously associated to a ??dilution?? effect during storm runoff events. Results show that both sediment sources and hydrologic events play an important role on the spatial and temporal variability of sediment-associated nutrient and metal contents.  相似文献   

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