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PubMed2004

Defining river types in a Mediterranean area: a methodology for the implementation of the EU Water Framework Directive.

The Water Framework Directive (WFD), approved at the end of 2000 by the European Union, proposes the characterization of river types through two classification systems (A and B) (Annex II of the WFD), thereby obtaining comparable reference sites and improving the management of aquatic systems. System A uses fixed categories of three parameters to classify rivers: three altitude ranges, four basin size ranges, and three geological categories. In the other hand, System B proposes to establish river types analyzing different factors considered as obligatory and optional. Here, we tested Systems A and B in the Catalan River Basin District (NE Spain). The application of System A results in 26 river types: 8 in the Pyrenees and 18 in the Iberic-Macaronesian ecoregions. This number would require the establishment of a complex management system and control of the ecological status in a relatively small river basin district. We propose a multivariant system to synthesize the environmental descriptors and to define river types using System B. We use five hydrological, seven morphological, five geological, and two climatic variables to discriminate among river types. This method results in fewer river type categories than System A but is expected to achieve the same degree of differentiation because of the large number of descriptors considered. Two levels are defined in our classification method using System B. Five "river types," defined at large scale (1:1,000,000), are mainly discriminated by annual runoff coefficient, air temperature, and discharge. This level is useful and could facilitate comparisons of results among European river basin districts. The second level defines 10 "subtypes of river management," mainly discriminated by geology in the basin and flow regime. This level is more adequate at local scale (1:250,000) and provides a useful tool for management purposes in relatively small and heterogeneous river basin districts.

Environment↗

PubMed2006

Characterization of benthic communities and physical habitat in the Stanislaus, Tuolumne, and Merced Rivers, California.

The primary goal of this study was to characterize physical habitat and benthic communities (macroinvertebrates) in the Stanislaus, Tuolumne and Merced Rivers in California's San Joaquin Valley in 2003. These rivers have been listed as impaired water bodies (303 (d) list) by the State of California due to the presence of organophosphate (OP) insecticides chlorpyrifos and diazinon, Group A pesticides (i.e., organochlorine pesticides), mercury, or unknown toxicity. Based on 10 instream and riparian physical habitat metrics, total physical habitat scores in the Stanislaus River ranged from 124 to 188 (maximum possible total score is 200). The highest total habitat score was reported at the upstream site. Tuolumne River physical habitat scores ranged from 86 to 167. Various Tuolumne River physical habitat metrics, including total habitat score, increased from downstream to upstream in this river. Merced River physical habitat scores ranged from 121 to 170 with a significant increase in various physical habitat metrics, including total habitat score, reported from downstream to upstream. Channel flow (an instream metric) and bank stability (a riparian metric) were the most important physical habitat metrics influencing the various benthic metrics for all three rivers. Abundance measures of benthic macroinvertebrates (5,100 to 5,400 individuals) were similar among the three rivers in the San Joaquin watershed. Benthic communities in all three rivers were generally dominated by: (1) Baetidae species (mayflies) which are a component of EPT taxa generally considered sensitive to environmental degradation; (2) Chironomidae (midges) which can be either tolerant or sensitive to environmental stressors depending on the species; (3) Ephemerellidae (mayflies) which are considered sensitive to pollution stress; and (4) Naididae (aquatic worms) which are generally considered tolerant to environmental stressors. The presence of 117 taxa in the Stanislaus River, 114 taxa in the Tuolumne River and 96 taxa in the Merced River implies that the benthic communities in these streams are fairly diverse but without a clear definition of benthic community expectations it is unknown if these water bodies are actually impaired.

Animals↗

PubMed2006

Distribution of PAEs in the middle and lower reaches of the Yellow River, China.

Samples of water, sediment and suspended particulates were collected from 13 sites in the middle and lower reaches of the Yellow River in China. Phthalic acid esters (PAEs) concentrations in different phases of each sample were determined by Gas Chromatogram GC-FID. The results are shown as follows: (1) In the Xiao Langdi-Dongming Bridge section, PAEs concentrations in water phase from the main river ranged from 3.99 x 10(-3) to 45.45 x 10(-3) mg/L, which were similar to those from other rivers in the world. The PAEs levels in the tributaries of the Yellow River were much higher than those of the main river. (2) In the studied branches, the concentration of PAEs in sediment for Luoyang Petrochemical Channel (331.70 mg/Kg) was the highest. The concentrations of PAEs in sediment phase of the main river were 30.52 to 85.16 mg/Kg, which were much higher than those from other rivers in the world. In the main river, the concentration level of PAEs on suspended solid phases reached 94.22 mg/Kg, and it reached 691.23 mg/Kg in the Yiluo River - one tributary of the Yellow River. (3) Whether in the sediment or on the suspended solid phases, there was no significant correlation between the contents of PAEs and TOC or particle size of the solid phase; and the calculated Koc of Di (2-Ethylhexyl) Phthalate (DEHP) in the river were much less than the theoretical value, which inferred that PAEs were not on the equilibrium between water and suspended solid phases/sediment. (4) Among the measured PAEs compounds, the proportions of DEHP and di-n-butyl phthalate (DBP) were much higher than the others. The concentrations of DEHP exceeded the Quality Standard in all the main river and tributary stations except those in the Mengjin and Jiaogong Bridge of the main river. This indicates that more attention should be paid to pollution control and further assessment in understanding risks associated with human health.

China↗

PubMed2006

Nitrate concentrations in river waters of the upper Thames and its tributaries.

The spatial and temporal patterns of in-stream nitrate concentrations for the upper Thames and selected tributaries are described in relation to point and diffuse sources for these rural catchments. The rivers associated with catchments dominated by permeable (Cretaceous Chalk) bedrock show a smaller range in nitrate concentrations than those associated with clay and mixed sedimentary bedrock of lower permeability. The differences reflect the contrasting nature of water storage within the catchments and the influence of point and diffuse sources of nitrate. Nitrate concentrations often increase in a gradual way as a function of flow for the rivers draining the permeable catchments, although there is usually a minor dip in nitrate concentrations at low to intermediate flow due to (1) within-river uptake of nitrate during the spring and the summer when biological activity is particularly high and (2) a seasonal fall in the water table and a change in preferential flow-pathway in the Chalk. There is also a decrease in the average nitrate concentration downstream for the Kennet where average concentrations decrease from around 35 to 25 mg NO(3) l(-1). For the lower permeability catchments, when point source inputs are not of major significance, nitrate concentrations in the rivers increase strongly with increasing flow and level off and in some cases then decline at higher flows. When point source inputs are important, the initial increase in nitrate concentrations do not always occur and there can even be an initial dilution, since the dilution of point sources of nitrate will be lowest under low-flow conditions. For the only two tributaries of the Thames which we have monitored for over 5 years (the Pang and the Kennet), nitrate concentrations have increased over time. For the main stem of the Thames, which was also monitored for over 5 years, there is no clear increase over time. As the Pang and the Kennet river water is mainly supplied from the Chalk, the increasing nitrate concentrations over time clearly reflect increasing nitrate concentrations within the groundwater. It primarily reflects long-term trends for agricultural fertilizer inputs and significant aquifer storage and long water residence times. The results are discussed in terms of hydrogeochemical processes and the Water Framework Directive and are compared with data from other eastern UK rivers. The importance of diffuse sources of nitrate contamination is highlighted. On a flow weighted basis, the average diffuse component of nitrate is around 95% for the Thames Basin rivers draining Chalk and for the corresponding rivers draining less permeable strata, there is a more significant but not major point source component (at least in terms of flux); the average diffuse component is 79% in this case. These data fit well with earlier assessments of agricultural sources to UK surface waters. Under baseflow conditions the diffuse sources remain dominant for the Chalk fed Thames Basin rivers, but point sources can be dominant for the low permeability cases. On a proportionate basis, the Thames Basin rivers are similar to the rural rivers of the Tweed and Humber Basins in terms of percentage diffuse components although the lower intensity agriculture occurring for the rivers monitored means that the average nitrate concentrations are lower for the rural rivers of central and northern England and the borders with Scotland: the Humber and Tweed.

Agriculture↗

PubMed2004

Spatial variation in hepatic levels and patterns of PCBs and PCDD/Fs among young-of-the-year and adult Atlantic tomcod (Microgadus tomcod) in the Hudson River estuary.

Full congener-specific polychorinated biphenyl (PCB) and partial-congener-specific polychorinated dibenzo-p-dioxin/furan (PCDD/F) analyses were performed on livers from young-of-the-year (YOY) and adult Atlantic tomcod from the Hudson River estuary including multiple sites along the main-stem Hudson River and Newark Bay/Hackensack River, NJ, and from a reference river, the Miramichi River, NB. Highest hepatic burdens of PCBs were found in fish collected in the main-stem Hudson River between river miles (RM) 37 and 50 and in Newark Bay/Hackensack River. By far, the highest concentrations of PCDD/Fs were seen in fish from Newark Bay/Hackensack River. The di- to tetrachlorinated biphenyls dominated the PCB composition in YOY tomcod, whereas the penta- to nonachlorinated biphenyls predominated in adults with particular prevalence of the 2,4,5-substituted diortho congeners. Overall, using a direct mixing model an aroclor composition of approximate 1:1:1, A1242:A1254:A1260, was calculated from the hepatic PCB profiles in YOY tomcod. A linear increase in A1242 characteristics with river mile was seen in YOY collected between RM 0 and RM 80, which was likely due to the well-characterized A1242 source from the former capacitor manufacturing plants located upriver. However, tomcod caught upstream of RM 80 exhibited a PCB pattern with decreasing A1242 characteristics, and it was hypothesized that this was due to the increased depuration or decreased uptake of low chlorinated (log K(OW) < 6) congeners upon entry of the fish into freshwater from brackish water. The most abundant tetra-octa PCDD/F chlorohomologue in tomcod collected from the main stem of the Hudson River was TCDF, whereas 2,3,7,8-TCDD was the major congener detected in tomcod from Newark Bay/Hackensack River, which showed elevated total PCDD/F levels compared to tomcod from the main-stem Hudson River.

Animals↗

PubMedDate not supplied

River-aquifer interactions, geologic heterogeneity, and low-flow management.

Low river flows are commonly controlled by river-aquifer exchange, the magnitude of which is governed by hydraulic properties of both aquifer and aquitard materials beneath the river. Low flows are often important ecologically. Numerical simulations were used to assess how textural heterogeneity of an alluvial system influences river seepage and low flows. The Cosumnes River in California was used as a test case. Declining fall flows in the Cosumnes River have threatened Chinook salmon runs. A ground water-surface water model for the lower river basin was developed, which incorporates detailed geostatistical simulations of aquifer heterogeneity. Six different realizations of heterogeneity and a homogenous model were run for a 3-year period. Net annual seepage from the river was found to be similar among the models. However, spatial distribution of seepage along the channel, water table configuration and the level of local connection, and disconnection between the river and aquifer showed strong variations among the different heterogeneous models. Most importantly, the heterogeneous models suggest that river seepage losses can be reduced by local reconnections, even when the regional water table remains well below the riverbed. The percentage of river channel responsible for 50% of total river seepage ranged from 10% to 26% in the heterogeneous models as opposed to 23% in the homogeneous model. Differences in seepage between the models resulted in up to 13 d difference in the number of days the river was open for salmon migration during the critical fall months in one given year.

Calibration↗

PubMed2006

Changes in biomass, chemical composition and nutritive value of Spartina alterniflora due to organic pollution in the Itanhaém River Basin (SP, Brazil).

We compared the values of the biomass, chemical composition and nutritive value of the emergent aquatic macrophyte S. alterniflora in a river affected by the discharge of domestic sewage (Guaú River) and in an unpolluted river (Itanhaém River). S. alterniflora, water and sediment samples were obtained in the two rivers in November, 2001. The Guaú River presented the highest levels of Total-N and Total-P in the water (415 and 674 microg.L(-1), respectively) and in the sediment (0.25 e 0.20% of the Dry Mass, respectively), when compared to the water (TN = 105 microg.L(-1); TP = 20 microg.L(-1)) and the sediment (NT = 0.12% DM; PT = 0.05% DM) of the Itanhaém River. Aerial (316 g DM.m(-2)) and subterraneous (425 g DM.m(-2)) biomass of S. alterniflora were significantly higher in the Guaú River than in the Itanhaém River (146 and 115 g DM.m(-2), respectively). In addition, the values of TN, protein, TP, lipids and soluble carbohydrates were significantly higher in S. alterniflora biomass from the Guaú River. On the other hand, the values of the polyphenols and the cell wall fraction were significantly higher in the biomass of S. alterniflora from the Itanhaém River. We concluded that domestic sewage discharge in water bodies may increase the biomass and change the chemical composition of S. alterniflora. The high N and P availability in the water of the Guaú River is probably the cause of the higher biomass, TN, TP, protein, lipids and soluble carbohydrates measured in S. alterniflora in this river.

Biomass↗

PubMed1990

Trace elements in Corbicula fluminea from the San Joaquin River, California.

(i) Trace element concentrations in soft tissue of the benthic bivalve, Corbicula fluminea, from the San Joaquin River and its major tributaries were examined during the primary irrigation season in relation to the spatial variation in concentrations of major, minor and trace constituents in riverwater and sediments. (ii) Selenium concentrations in Corbicula from perennial flow reaches of the San Joaquin River and its major tributaries varied directly with the solute (less than or equal to 0.45 microns) Se concentrations of riverwater. Elevated concentrations occurred in clams from sites with substantial discharge originating as subsurface drainage and irrigation return flows. Both tissue and solute Se concentrations declined from June through the end of the primary irrigation season. (iii) Arsenic concentrations in Corbicula from perennial flow reaches of the San Joaquin River varied directly with the HNO3-extractable (pH 2) As:Fe ratio of suspended matter, providing evidence that sorption to oxyhydroxide surfaces is an important control on the biological availability of As. However, Corbicula from several tributaries draining alluvium derived from the Sierra Nevada had lower As concentrations than would be predicted by the relation developed for perennial flow sites of the San Joaquin River. Arsenic concentrations in Corbicula from the Tuolumne and Merced Rivers and upstream reaches of the San Joaquin River were higher than in clams from the downstream perennial flow reaches of the San Joaquin River. Concentrations of As in clams from downstream perennial flow reaches of the San Joaquin River increased from June through the end of the primary irrigation season. (iv) Mercury concentrations in Corbicula were elevated in upstream reaches of the San Joaquin River, in the Merced and Tuolumne Rivers, and in tributaries draining the Coast Ranges. Mean Cd and Cu concentrations in Corbicula were elevated in the Merced and Tuolumne Rivers, Orestimba Creek and a perennial flow reach of the San Joaquin River which receives water directly from the Delta Mendota Canal. Concentrations of Ni in clams from the San Joaquin River decreased downstream of the Delta Mendota Pool. (v) Boron and Mo were not accumulated by Corbicula despite high solute concentrations (means as high as 2960 micrograms Bl-1 and 9 micrograms Mol-1) in riverwater during the primary irrigation season. This bivalve may not be an appropriate bioindicator of B and Mo enrichment. Concentrations of Cr, Pb, Ag, V and Zn in Corbicula exhibited little geographic variability in the drainage. (vi) Regression analysis revealed no clear evidence of synergistic or antagonistic interactions among As, Cd, Cu, Hg, Ni and Se in their uptake by Corbicula.

Animals↗

PubMed2003

Analysis of photosynthetic activity in the most polluted stretch of river Ganga.

As a result of the increasing anthropogenic activities in the gangetic plain, Ganga water quantity as well as quality has declined over the years. A major effort to clean Ganga, named Ganga Action Plan (GAP) was instituted by the Government of India in 1984. The emphasis in GAP was on the reduction of organic load on the river through interception, diversion and treatment of wastewater reaching the river, thus maintaining the biochemical oxygen demand (BOD) and dissolved oxygen (DO) levels of river within the acceptable limits. A major criticism of GAP is that the significance of river ecology has not been addressed adequately during its conception and implementation. One of the important aspects from this perspective is the photosynthetic activity in the river Ganga. It has been postulated that photosynthetic activity plays an important role in maintaining high levels of DO in Ganga, and as a result the river can assimilate high organic loads without appreciable depletion in dissolved oxygen levels. Objective of the present study was to assess the photosynthetic activity and oxygen production rates in the river and correlate these values with various water quality parameters. Most polluted stretch of Ganga, which is known as the Kannauj-Kanpur stretch was chosen for this study. Based on the results of the study, it was concluded that despite implementation of phase I of GAP, and consequent diversion and reduction of organic loading to the river, both BOD and DO levels in the river has increased in the entire Kannauj-Kanpur stretch, except at Jajmau, where anaerobically treated effluent is discharged to the river. The nitrogen levels have also increased in the entire Kannauj-Kanpur stretch. Dissolved oxygen (DO) and alkalinity in the river water vary diurnally at all sites. Chlorophyll-a levels and oxygen production rates due to photosynthesis appear to be positively influenced by phosphate levels in the river water. Chlorophyll-a levels appear to be negatively correlated to the Ammonical and total Total Kjeldahl Nitrogen (TKN) content in the river water, suggesting the possibility of release of nutrients due to algal death and decomposition under certain circumstances.

Chlorophyll↗

PubMed2006

Northern Rivers Ecosystem Initiative: nutrients and dissolved oxygen - issues and impacts.

Anthropogenic inputs of nitrogen (N), phosphorus (P) and oxygen-consuming material to aquatic ecosystems can change nutrient dynamics, deplete oxygen, and change abundance and diversity of aquatic plants and animals. The Northern Rivers Ecosystem Initiative required a research and assessment program to establish the contribution of pulp mill and sewage discharges to eutrophication and depressions in dissolved oxygen (DO) in the Athabasca and Wapiti rivers of northern Alberta, Canada and examine the adequacy of existing guidelines for protecting these systems. Analysis of long-term data showed that total N (TN) and total P (TP) concentrations in exposed river reaches exceeded concentrations in reference reaches by < or = 2 times for the Athabasca River, and by 9.6 (TP) and 2.6 (TN) times for the Wapiti River. Results from nutrient limitation experiments conducted in situ and in mesocosms showed that benthic algal production was nutrient sufficient downstream of pulp mill discharges but constrained in upper river reaches by insufficient P (Athabasca River) or N + P (Wapiti River). Dissolved oxygen (DO) concentrations in both rivers declined during winter such that median concentrations in the Athabasca River 945 km downstream of the headwaters were approximately 8 mg L(-1) in mid-February. Although water column DO rarely approached the guideline of 6.5 mg L(-1), DO studies undertaken in the Wapiti River showed that pore water DO often failed to meet this guideline and could not be predicted from water column DO. Results from this integrated program of monitoring and experimentation have improved understanding of the interactions between nutrients, DO and aquatic ecosystem productivity and resulted in recommendations for revisions to nutrient and DO guidelines for these northern rivers.

Alberta↗

PubMed2006

Evidence of spatially extensive resistance to PCBs in an anadromous fish of the Hudson River.

Populations of organisms that are chronically exposed to high levels of chemical contaminants may not suffer the same sublethal or lethal effects as naive populations, a phenomenon called resistance. Atlantic tomcod (Microgadus tomcod) from the Hudson River, New York, are exposed to high concentrations of polycyclic aromatic hydrocarbons (PAHs) and bioaccumulate polychlorinated biphenyls (PCBs), polychlorinated dibenzo-p-dioxins (PCDDs), and polychlorinated dibenzofurans (PCDFs). They have developed resistance to PCBs and PCDDs but not to PAHs. Resistance is largely heritable and manifests at early-life-stage toxic end points and in inducibility of cytochrome P4501A (CYP1A) mRNA expression. Because CYP1A induction is activated by the aryl hydrocarbon receptor (AHR) pathway, as are most toxic responses to these compounds, we sought to determine the geographic extent of resistance to CYP1A mRNA induction by PCBs in the Hudson River tomcod population. Samples of young-of-the-year tomcod were collected from seven locales in the Hudson River, extending from the Battery at river mile 1 (RM 1) to RM 90, and from the Miramichi River, New Brunswick, Canada. Laboratory-reared offspring of tomcod adults from Newark Bay, in the western portion of the Hudson River estuary, were also used in this study. Fish were partially depurated in clean water and intraperitoneally injected with 10 ppm coplanar PCB-77, 10 ppm benzo[a]pyrene (BaP), or corn oil vehicle, and levels of CYP1A mRNA were determined. CYP1A was significantly inducible by treatment with BaP in tomcod from the Miramichi River, from laboratory-spawned offspring of Newark Bay origin, and from all Hudson River sites spanning 90 miles of river. In contrast, only tomcod from the Miramichi River displayed significantly induced CYP1A mRNA expression when treated with PCB-77. Our results suggest that the population of tomcod from throughout the Hudson River estuary has developed resistance to CYP1A inducibility and probably other toxicities mediated by the AHR pathway. Tomcod from the Hudson River may represent the most geographically expansive population of vertebrates with resistance to chemical pollutants that has been characterized.

Animals↗

PubMed2005

[Modelling pollutant loads and management alternatives in Jiulong River watershed with AnnAGNPS].

The modelling package Annualized Agricultural Nonpoint Source Model (AnnAGNPS) was used to predict pollutant loads, and simulate catchment processes and management practices in Jiulong River watershed, a medium-sized mountainous watershed in southeast of China. Four typical sub-watersheds were primarily chosen to calibrate AnnAGNPS model by data collected from storm events during the period of April to September, 2003. The model was further validated in the two biggest branches of Jiulong River watershed, i.e. West river and North river by the data regarding climate, and land using condition in 2002 - 2003. The simulation results show that annual total nitrogen load was 24.76kg/(hm2 x a) and 10.28kg/(hm2 x a) in the West river and North river, respectively, and annual total phosphorus load was 0.67 kg/(hm2 x a) and 0.40 kg/(hm2 x a) in the West river and North river, respectively. With the support of AnnAGNPS model, several management alternatives were separately simulated in the typical sub-watersheds, West river and North river. In the specific cell with cell-ID of 92 in Tianbao and Xiandu sub-watershed, after reforesting in sloping field, runoff surface, sediment yield, total nitrogen load and total phosphorus load cut down with 21.6%, 25.9%, 96% and 79.2%, respectively. In West river, with the cultivation plant changing from banana into rice, the total nitrogen, dissolved nitrogen, total phosphorus and dissolved phosphorus cut down with 23.83%, 25.44%, 9.08% and 19.84%, respectively. In North river, when removing all the hoggerys, nitrogen and dissolved nitrogen cut down with 63.54% and 76.92% , respectively.

China↗

PubMed2002

River systems as providers of goods and services: a basis for comparing desired and undesired effects of large dam projects.

In developing countries, large dam projects continue to be launched, primarily to secure a time-stable fresh-water supply and to generate hydropower. Meanwhile, calls for environmentally sustainable development put pressure on the dam-building industry to integrate ecological concerns in project planning and decision-making. Such integration requires environmental impact statements (EISs) that can communicate the societal implications of the ecological effects in terms that are understandable and useful to planners and decision-makers. The purpose of this study is to develop a basic framework for assessing the societal implications of the river ecological effects expected of a proposed large dam project. The aim is to facilitate a comparison of desired and potential undesired effects on-site and downstream. The study involves two main tasks: to identify key river goods and services that a river system may provide, and to analyze how the implementation of a large dam project may alter the on-site capacity and downstream potentials to derive river goods and services from the river system. Three river goods and six river services are identified. River goods are defined as extractable partly man-made products and river services as naturally sustained processes. By four main types of flow manipulations, a large dam project improves the on-site capacity to derive desired river goods, but simultaneously threatens the provision of desirable river goods and services downstream. However, by adjusting the site, design, and operational schedule of the proposed dam project, undesirable effects on river goods and services can be minimized.

Conservation of Natural Resources↗

PubMed1997

The geochemistry of river particulates from the continental USA: major elements.

River particulates have been collected from twenty-three rivers from throughout the continental USA. The rivers drain mostly large basins (basin areas range from 2.1 x 10(3) to 2970 x 10(3) km2) composed of mixed lithologies, and spanning a wide range of climatic conditions as evidenced by a large variation in air and ground water temperatures, precipitation, and runoff. Suspended particulates have been analyzed for organic and inorganic carbon, as well as the major elements Al, Fe, Mn, K, Si, Ca, Mg, and Na. Also determined were suspended sediment loads at the time of sampling, particle surface areas, and grain size distributions. Five-year average river water chemistry and suspended sediment concentrations, obtained from USGS water supply reports, are also included as supporting information. Particle chemistry systematically varies with rates of runoff, with high runoff rivers transporting the most heavily altered particulates and low runoff rivers carrying the least altered. Degrees of alteration are indicated by the extent to which the refractory, nonmobile elements Al and Fe are concentrated into the particulates and the extent to which the most easily weathered elements Na, Ca, and Mg have been leached. Overall, the susceptibility of elements towards leaching is consistent with numerous previous descriptions of element mobility on weathering. A simple predictive model has been developed to explore and explain the observed trends between particle composition and river runoff. Thus, the elemental composition of riverine particulates may be given by the expression PCOi = [(Propi)TM-DCOi]/SS, where PCOi is the concentration of element i (as the oxide) in a riverine particulate, Propi is the proportion of i (as the oxide) in unweathered rock, DCOi is the dissolved concentration of i (as the equivalent oxide), TM is the total rock derived mass dissolved in river water, and SS is suspended sediment concentration. To utilize this equation, a model was first developed to predict the concentration of river solutes with the input of temperature, precipitation, and a limited number of weathering parameters. Combining this solute model with the above predictive equation for particle composition, it was discovered that the observed trends between particle composition and runoff require the special circumstance of decreasing SS with increasing runoff. Hence, the composition of river particulates depends both on the climate parameters of runoff and temperature (as they control dissolved river chemistry) and the nonclimate parameters including elevation, relief, tectonics, and basin area that control the SS load of rivers.

Climate↗

PubMed2002

Distribution and fate of organochlorine pesticide residues in sediments from the selected rivers in Taiwan.

The contamination of organochlorine pesticides (OCPs) in sediments from selected rivers in Taiwan was investigated to evaluate the pollution potentials and hazard in river sediments. Da-han River and Erh-jen River were selected as the target rivers due to their serious pollution. A total of 40 surface sediment samples were collected at five sampling stations along the rivers. Results showed that the concentrations of various pesticides in sediments were in the range of 0.57-14.1 ng/g for sigmaHCH, 0.05-0.15 ng/g for aldrin, 0.12-5.8 ng/g for dieldrin, 0.22-0.64 for endrin, 0.24-6.37 ng/g for endosulfan and 0.21-8.81 ng/g for EDDT (p,p'-DDD, p,p'-DDE, p,p'-DDT). Among the OCPs, sigmaHCH, endosulfan and sigmaDDT were the most dominant compounds in the river sediments. Endosulfan sulfate was the most frequent detected compound in the sediments from the selected rivers. Also, sigmaDDT, dieldrin and beta-HCH were in abundance. Different contamination patterns between the selected river sediments were also observed. Da-han River was mainly contaminated with endosulfan sulfate and sigmaDDT. Whereas the main pesticides in Erh-jen River were beta-HCH and sigmaDDT. Among the cyclodiene compounds, dieldrin was in abundance in most of the sediments. Moreover, the frequencies of detection of the metabolites were higher than those of parent compounds, depicting that the sediments have contaminated for a long time. The results obtained in this study showed that there still exist a variety of OCP residues in the river sediments in Taiwan.

Environmental Monitoring↗

PubMed2003

Methylmercury in rivers draining cultivated watersheds.

Total mercury (THg) concentrations in streams draining cultivated watersheds in Minnesota, USA are strongly correlated with total suspended sediment (TSS) concentrations, varying widely in response to precipitation-driven inputs of soil-derived suspended sediments. Methylmercury (MeHg) concentrations in these waterways have not been studied, and little is known about mercury uptake mechanisms in resident fish populations. To begin to identify factors influencing MeHg concentrations and loadings in these streams, we measured THg and MeHg concentrations in unfiltered whole water samples from the Minnesota River and two of its major tributaries, the Blue Earth and Le Sueur Rivers. Land use in the watersheds of these rivers is over 90% row-crop agriculture, and extensive artificial drainage systems deliver runoff and associated solids quickly to local streams and rivers. THg concentrations were elevated (>10 ng/l) during much of Spring 2000 and part of the summer when runoff from precipitation events increased stream discharge and carried soil materials into the streams. Reduced precipitation resulted in low flow conditions from August through October, and THg concentrations decreased to <4.0 ng/l in all three rivers. MeHg concentrations in the Le Sueur River ranged from 0.07 to 0.42 ng/l between June and December. Higher MeHg concentrations (>0.2 ng/l) were measured during summer months when THg and TSS concentrations were high after precipitation events. Elevated MeHg concentrations were also observed in late October after leaf litter inputs. Conditions on the Blue Earth River were different, with elevated MeHg concentrations (>0.5 ng/l) observed during low flow in August and September. These higher concentrations coincided with a period of enhanced microbial growth stimulated by high late-summer temperatures. A late-October increase in MeHg concentration attributed to leaf litter inputs was also observed in this river. MeHg concentration trends in the Minnesota River were similar to those in the Blue Earth River. Indicators of biological productivity (chlorophyll a, volatile suspended solids, and total Kjeldahl nitrogen) were higher in the Blue Earth and Minnesota Rivers compared to the Le Sueur River, which may signal a connection between higher biological activity and increased MeHg concentrations.

Agriculture↗

PubMed2000

Attributes of an alluvial river and their relation to water policy and management.

Rivers around the world are being regulated by dams to accommodate the needs of a rapidly growing global population. These regulatory efforts usually oppose the natural tendency of rivers to flood, move sediment, and migrate. Although an economic benefit, river regulation has come at unforeseen and unevaluated cumulative ecological costs. Historic and contemporary approaches to remedy environmental losses have largely ignored hydrologic, geomorphic, and biotic processes that form and maintain healthy alluvial river ecosystems. Several commonly known concepts that govern how alluvial channels work have been compiled into a set of "attributes" for alluvial river integrity. These attributes provide a minimum checklist of critical geomorphic and ecological processes derived from field observation and experimentation, a set of hypotheses to chart and evaluate strategies for restoring and preserving alluvial river ecosystems. They can guide how to (i) restore alluvial processes below an existing dam without necessarily resorting to extreme measures such as demolishing one, and (ii) preserve alluvial river integrity below proposed dams. Once altered by dam construction, a regulated alluvial river will never function as before. But a scaled-down morphology could retain much of a river's original integrity if key processes addressed in the attributes are explicitly provided. Although such a restoration strategy is an experiment, it may be the most practical solution for recovering regulated alluvial river ecosystems and the species that inhabit them. Preservation or restoration of the alluvial river attributes is a logical policy direction for river management in the future.

Journal Article↗

PubMed2002

Heavy metals in water bodies purified by suspended substrate of rivers.

The equations, which are used to describe the relationships of adsorption quantity (s), adsorption percent (Pa), aqueous equilibrium concentration(c) of heavy metal on river suspended substrates and the ratio of adsorbent to water(j), are developed when heavy metal adsorption on river suspended substrate satisfies with linear adsorption equation. The results, according to the simulation from heavy metal adsorption on suspended substrates of several main Chinese rivers from a previous research report, indicated that these developed equations could describe the linear adsorption processes in practice very well, meanwhile, the adsorption equilibrium constant of adsorbent for heavy metal was an intensity factor regardless of ratio of suspended substrates to water but strongly depended on media's pH. Furthermore, the suspended substrates of Yellow River gave stronger purification ability for Pb than for Cd and Cu. When Cd was purified by different river suspended substrates, it exhibited that the order of their purification ability for Cd was that of Songhuajiang River > Zhujiang Pearl River > Yellow River, which was consistent with their contents of cation exchange capacity(CEC). In addition, we estimated and compared the purification ability of river suspended substrates for cadmium, and the resulting purification percent was 37.64%, 64.58% and 50.98% for Songhuajiang River, Yangtze River and Zhujiang River, respectively.

Adsorption↗