Rural River Research Articles

Accumulation and risk assessment of heavy metals in water, sediments, and aquatic organisms in rural rivers in the Taihu Lake region, China.

Concentrations of heavy metals (Cd, Cr, Cu, Ni, Pb, and Zn) were measured in water, sediments, Ceratophyllum (hornwort), and Bellamya sp. (edible snail) from residential, mixed (industrial and commercial), and agricultural areas with rural rivers in the Taihu Lake region, China. Zn concentrations were the highest, whereas Cd concentrations were the lowest among the six metals in water, sediments, and aquatic organisms. Cd was mainly present in the acid-soluble fraction, Cr in the residual fraction, and Pb in the reducible fraction of sediments. Heavy metal concentrations in water, sediments, and aquatic organisms in the three areas followed the order of the mixed area > residential area > agricultural area. Heavy metal concentrations in aquatic organisms were not only related to total metal concentrations in water and sediments but also to metal speciation concentrations in sediments. In addition, the bio-concentration factor (BCF) values of Cr, Cu, Pb, and Zn for Bellamya sp. were higher than those for Ceratophyllum, whereas the BCF values of Cd and Ni for Bellamya sp. were lower than those for Ceratophyllum. An ecological risk assessment of heavy metals in sediments showed that Cd posed the highest ecological risk to the environment. A health risk assessment showed that consuming Bellamya sp. from the mixed area could cause a potential health risk.

Heavy Metal Speciation in Sediments and the Associated Ecological Risks in Rural Rivers in Southern Jiangsu Province, China

Heavy metal speciation and the associated ecological risks were investigated, using a European Community Bureau of Reference sequential extraction procedure, in sediments from the residential, mixed (residential and industrial), and agricultural areas of rural rivers in southern Jiangsu Province, China. Compared with the background values in Jiangsu Province soils, Cd was the metal with the highest contamination level, especially in the mixed area, followed by Cu and Zn. In the sediment samples from the agricultural area, the heavy metal concentrations were no more than two times greater than the background values. There were higher proportions of Cd in the acid-soluble fraction, Cr in the residual fraction, and Pb in the reducible fraction in the three areas. The heavy metal mobility was mainly controlled by the acid-soluble and reducible fractions. Cd could pose extremely high risks to the environment. In addition, the risks of heavy metal to the environment in the three areas followed the order: mixed area > residential area > agricultural area. Furthermore, a risk assessment code analysis showed that most of the sediment samples were classified as being of high to very high risk in the residential and mixed areas because of their Cd, Ni, and Zn concentrations. Heavy metal pollution in the residential and mixed areas is generally serious, and immediate remediation measures need to be taken.

Hydrological Effects on Relationships Between δ15N of River Nitrate and Land Use in a Rural River Basin, Western Japan

AbstractThis study aimed to examine how the relationship between δ15N of nitrate (δ15NNO3) in rivers and land use within a river basin changes with varying hydrological conditions. This information would aid in identifying the dominant source contributing to increased nitrate concentrations in rural rivers. For this, δ15NNO3 in river water was investigated monthly in the five subbasins of the Hii River basin (area: 911 km2), western Japan, for 1 year and 3 months. There were significant correlations (p < 0.05) between δ15NNO3 and the land‐use ratio (i.e. ratios of forested, agricultural and residential areas in a subbasin) for the majority of the observation days, indicating that δ15NNO3 reflected land use within the basin. δ15NNO3 ranged from +1.4‰ to +8.5‰ and was lower in a subbasin with a higher forested area ratio. We found that the absolute value of the regression slope of the relationship between δ15NNO3 and the land‐use ratio decreased with increasing river discharge. This finding demonstrates that differences in δ15NNO3 among subbasins with different land‐use compositions became smaller under higher flow conditions. Because δ15NNO3 decreased with increasing river discharge, the small absolute value of the regression slope under high flow conditions indicates that forested areas could be the dominant source of river nitrate during high flows in all subbasins investigated regardless of land‐use composition. The results suggest that forested areas make a large contribution to the increase in nitrate concentration in downstream rivers during high flows, because the nitrate concentration increased with increasing river discharge. Copyright © 2014 John Wiley & Sons, Ltd.

The Water Quality of the River Enborne, UK: Observations from High-Frequency Monitoring in a Rural, Lowland River System

This paper reports the results of a 2-year study of water quality in the River Enborne, a rural river in lowland England. Concentrations of nitrogen and phosphorus species and other chemical determinands were monitored both at high-frequency (hourly), using automated in situ instrumentation, and by manual weekly sampling and laboratory analysis. The catchment land use is largely agricultural, with a population density of 123 persons km−2. The river water is largely derived from calcareous groundwater, and there are high nitrogen and phosphorus concentrations. Agricultural fertiliser is the dominant source of annual loads of both nitrogen and phosphorus. However, the data show that sewage effluent discharges have a disproportionate effect on the river nitrogen and phosphorus dynamics. At least 38% of the catchment population use septic tank systems, but the effects are hard to quantify as only 6% are officially registered, and the characteristics of the others are unknown. Only 4% of the phosphorus input and 9% of the nitrogen input is exported from the catchment by the river, highlighting the importance of catchment process understanding in predicting nutrient concentrations. High-frequency monitoring will be a key to developing this vital process understanding.

Evaluating the Relationship between Phosphorus Bioavailability and Phosphorus Speciation in Sediments from Rural Rivers in the Taihu Lake Area, China

The concentrations of different phosphorus (P) species and four kinds of bioavailable P (algae-available P, AAP; Olsen P, OLP; water-soluble P, WSP; and readily desorbable P, RDP) were determined to investigate the relationship between phosphorus bioavailability and phosphorus speciation in sediments from rural rivers in Taihu Lake area, China, using a European Commission “Standards Measurements and Testing Program” protocol and four chemical extraction techniques. The total P and inorganic P concentrations in the sediments were 179-2,293 mg/kg and 137-1,857 mg/kg, respectively. The concentrations of the P species in the sediments followed the order NaOH- extractable P > HCl-extractable P > organic P. The bioavailable P concentrations followed the order AAP (340 mg/kg) > OLP (38.7 mg/kg) > WSP (1.8 mg/kg) > RDP (0.3 mg/kg). Regression analyses showed that there were good correlations between the P species concentrations and the bioavailable P concentrations measured using the four different methods, except for between WSP and the HCl-extractable P concentrations. The OLP concentrations had highly significant correlations with AAP, WSP, RDP and the P species concentrations. The OLP method was found to be most suitable for determining the bioavailability of P species under the prevalent geochemical conditions in the rural river sediments that were analyzed.

Assessment of Potential Risk to Aquatic Organisms by Zinc Originating from Swine Farm Effluent in a Rural Area of Japan

Commercial swine production can cause local water pollution if effluent water containing high levels of nitrogen (N), phosphorus (P), pathogen and heavy metals is discharged, but the actual status remains poorly documented. We thus selected zinc metal (Zn) as a tracer and conducted water quality observations in a rural river of Japan to reveal the significance of mid-sized swine farms on Zn pollution there. Results showed that one farm was the major contributor of Zn load in watershed, corresponding to 82% of total Zn load at a normal stage of water, which was apparently attributable to insufficient wastewater treatment at the farm. Consequently, the Zn concentration at the outlet was estimated at 37 μg L –1 , revealing a significant ecological risk at 9.1% to aquatic organisms. We then analyzed the effectiveness of improved wastewater treatment of the farm and found that it had a plausible capacity to keep Zn concentration at the outlet below the environmental quality standard level (30 μg-Zn L –1 ) and the ecological risk at a safety level (<5%) as well. Based on these results, we concluded that since a swine farm could be a significant source of pollutants in rural areas, appropriate treatment of wastewater would be essential to sustain the potential pollution by Zn.

Distribution and pollution, toxicity and risk assessment of heavy metals in sediments from urban and rural rivers of the Pearl River delta in southern China

Sediments were collected from the upper, middle and lower reaches of both urban and rural rivers in a typical urbanization zone of the Pearl River delta. Six heavy metals (Cd, Cr, Cu, Ni, Pb and Zn) were analyzed in all sediment samples, and their spatial distribution, pollution levels, toxicity and ecological risk levels were evaluated to compare the characteristics of heavy metal pollution between the two rivers. Our results indicated that the total contents of the six metals in all samples exceeded the soil background value in Guangdong province. Based on the soil quality thresholds of the China SEPA, Cd levels at all sites exceeded class III criteria, and other metals exhibited pollution levels exceeding class II or III criteria at both river sites. According to the sediment quality guidelines of the US EPA, all samples were moderately to heavily polluted by Cr, Cu, Ni, Pb and Zn. Compared to rural river sites, urban river sites exhibited heavier pollution. Almost all sediment samples from both rivers exhibited moderate to serious toxicity to the environment, with higher contributions from Cr and Ni. A "hot area" of heavy metal pollution being observed in the upper and middle reaches of the urban river area, whereas a "hot spot" was identified at a specific site in the middle reach of the rural river. Contrary metal distribution patterns were also observed along typical sediment profiles from urban and rural rivers. However, the potential ecological risk indices of rural river sediments in this study were equal to those of urban river sediments, implying that the ecological health issues of the rivers in the undeveloped rural area should also be addressed. Sediment organic matter and grain size might be important factors influencing the distribution profiles of these heavy metals.

印旛沼流入河川における地下水起源の窒素負荷に関する検討

Nitrogen contamination in rural rivers may be caused due to pollutant load from plowed fields with excessive fertilization through groundwater. However there has been little information for discharge and pollutant load of groundwater into rivers. In the present study, we conducted field measurements to clarify the discharge and nitrogen flux of groundwater into the Takasakigawa River, flowing into Lake Inba-numa, with nitrogen contamination. The results indicated that: 1) nitrate concentration of groundwater was mostly higher than that of river water, and 2) discharge and nitrate flux of groundwater into the river were 73~92%, and 81~95%, respectively in the observed reach with 1.4 km in length. The source of the groundwater flowing into the Takasakigawa River were discussed using water quality data of groundwater in its watershed.

Correlations between aesthetic preferences of river and landscape characters

Abstract Some landscape characters put great influences on the aesthetic preferences of a river. Finding out these characters will provide for river landscape design and management with explicit keystones. In this paper, 23 sample areas of rivers were selected in Xuzhou, China, and 15 landscape characters of rivers were identified. The photos taken at the sample areas were as stimuli, and undergraduate students were respondents. The results demonstrate that the aesthetic preferences of photos judged one-by-one and judged together receive similar results; the preference scores of deflective views are significantly higher than the ones of opposite views; for urban rivers, “river accessibility” and “number of colours” are reliably positive predictors to aesthetic preferences, “wood diversity index” and “plants on water” are negative ones; for rural rivers, “coverage of riparian vegetation”, “perspective” and “wood diversity index” are reliably positive predictors to aesthetic preferences.

Hydrochemical processes in lowland rivers: insights from in situ, high-resolution monitoring

Abstract. This paper introduces new insights into the hydrochemical functioning of lowland river systems using field-based spectrophotometric and electrode technologies. The streamwater concentrations of nitrogen species and phosphorus fractions were measured at hourly intervals on a continuous basis at two contrasting sites on tributaries of the River Thames – one draining a rural catchment, the River Enborne, and one draining a more urban system, The Cut. The measurements complement those from an existing network of multi-parameter water quality sondes maintained across the Thames catchment and weekly monitoring based on grab samples. The results of the sub-daily monitoring show that streamwater phosphorus concentrations display highly complex dynamics under storm conditions dependent on the antecedent catchment wetness, and that diurnal phosphorus and nitrogen cycles occur under low flow conditions. The diurnal patterns highlight the dominance of sewage inputs in controlling the streamwater phosphorus and nitrogen concentrations at low flows, even at a distance of 7 km from the nearest sewage treatment works in the rural River Enborne. The time of sample collection is important when judging water quality against ecological thresholds or standards. An exhaustion of the supply of phosphorus from diffuse and multiple septic tank sources during storm events was evident and load estimation was not improved by sub-daily monitoring beyond that achieved by daily sampling because of the eventual reduction in the phosphorus mass entering the stream during events. The results highlight the utility of sub-daily water quality measurements and the discussion considers the practicalities and challenges of in situ, sub-daily monitoring.

Towards understanding links between rural land management and the catchment flood hydrograph

AbstractThe nature of causal links between land management in rural river catchments and the flood hydrograph is investigated. A catchment can be represented as a mosaic of tiles with different land use, land management, and soils. Over the mosaic, the causal links vary with the physical properties of the land and channel drainage network, and with the management practices and space–time variations in rainfall and evaporation. The river Hodder catchment in northwest England is represented using a custom‐designed semi‐distributed rainfall‐runoff model. An adjoint, reverse algorithmic differentiation, version of the model is then used to find the sensitivity of the peak flow rate at the catchment outlet to the model parameters controlling runoff generation. Using this novel approach, the links between changes in land management and the impact on the peak flow rate are investigated by decomposing the impact in space to give maps that show the sources of impact, tile by tile. The method works quite well for the Hodder catchment, especially for rainfall events in the autumn and winter. Its strengths and weaknesses are discussed. Copyright © 2012 Royal Meteorological Society

Environmental fragility evaluation and guidelines for environmental zoning: a study case on Ibiuna (the Southeastern Brazilian region)

Environmental fragility models are important decision tools for policy makers as they help quantify environmental sensitivity and understand the relationship between human activities and environmental quality. The objective of this study was to evaluate three different environmental fragility models within the Brazilian rainforest region and to use the results to develop environmental zone classes. Two rural river basins located in Ibiuna, Sao Paulo state, Brazil, were studied. Input variables, including slope class, relief dissection rate, soil class, lithology, land cover, and climate data, were used to compute environmental fragility classes using three standard models. The model outputs were evaluated on their ability to accurately predict the most sensitive and least sensitive areas. The best models for each region were used to derive environmental zoning maps, including restoration priorities, best regions for agriculture, and areas with high needs for soil management. These maps will help support land use strategies for environmental restoration. This study provides insight into territorial ordering and management of environmental services with a regional perspective.

Numerical Analysis of Sludge Pump with Recessed Centrifugal Impeller

The sedimentation in rural rivers of China are threatening the drinking water safety of rural population, affecting their living environment, and weakening their comprehensive agricultural productivity. In this paper the internal flow patterns of a sludge pump with three different recessed centrifugal impellers were analyzed based on CFD by using the turbulence model to close the time-averaged Navier-Stokes equations. On the basis of computed results their energy performances were compared that the pump with backward bent blades gets highest hydraulic efficiency and the one with forward bent blades obtains lowest hydraulic efficiency while the one with straight blades goes intermedium.

Modeling riverine pathogen fate and transport in Mexican rural communities and associated public health implications

The discharge of untreated or poorly treated wastewater to river systems remains a major problem affecting public and environmental health, particularly in rural communities of less developed countries. One of the primary goals in setting policies for wastewater management is to reduce risks to human health associated with microbial contamination of receiving water. In this study, we apply a surface water quality model to develop an Escherichia coli based indicator that reflects the quality of surface water and the potential impact to recreational users in a large, rural river in northwest Mexico (upper Sonora River). The model assesses the relative importance of streamflow variations and the uncertainty in E. coli removal coefficient parameters for the predictions of E. coli concentrations in the river. Given the sparse information on streamflow, we use a physically-based, distributed hydrologic model to generate tributary contributions to the river. We determined the best estimate and uncertainty of E. coli removal rates to explore the impacts of parameter uncertainty on the transport of E. coli downstream from two wastewater discharge zones. Our results depict the regions in the river that are in noncompliance with fresh water pathogen norms. The impact of streamflow variability and uncertainty in the removal rates of pathogen indicators was used to derive a range of river distances in noncompliance. The comparison between two sites with different streamflow behaviors was used to illustrate the impacts of streamflow spatiotemporal variability on pathogen indicators. We derive a simple relationship that can be used to assess the relative importance of dilution (ratio of wastewater discharge to river discharge) and pathogen removal (ratio of residence time to reaction time).

Genetic diversity and molecular characterization of enteroviruses from sewage-polluted urban and rural rivers in the Philippines

Despite the vast distribution and expansive diversity of enteroviruses reported globally, indicators defining a complete view of the epidemiology of enteroviruses in tropical countries such as the Philippines are yet to be established. Detection of enteroviruses in the environment has been one of the markers of circulating viruses in a community. This study aimed to bridge the gap in the epidemiology of enteroviruses in the Philippines by providing an overview of the occurrence of enteroviruses in both urban and rural rivers. Molecular detection directed at the VP1 region of the enterovirus genome was performed on 44 grab river water samples collected from April to December 2009. The majority of the enterovirus serotypes detected were clustered with human enterovirus C species (HEV-C; 21/42), followed by HEV-B (12/42) and HEV-A (9/42). Porcine enterovirus 9 was also found in 12 out of 44 water samples. Phylogenetic analysis indicated that the viruses detected were closely related, if not all forming a monophyletic clade, with those enteroviruses detected previously from acute flaccid paralysis cases in the country. The clustering of environmental and human enterovirus strains implies that the circulation of these strains were associated with river contamination. This study gives further evidence of the environmental persistence of enteroviruses once they are shed in feces and likewise, provides additional data which may help in understanding the epidemiology of enteroviruses in humans, highlighting the need for more studies on the potential public health risks linked with enteroviruses found in the environment and their eventual clinical consequences in the country.Electronic supplementary materialThe online version of this article (doi:10.1007/s11262-012-0776-z) contains supplementary material, which is available to authorized users.

Identifying Cultural Service Values of a Small River in the Agricultural Landscape of Canterbury, New Zealand, Using Combined Methods

Intensification of agricultural production involving groundwater irrigation is increasingly significant in many countries but can have negative impacts upon the ecosystem cultural services of rural streams and rivers. These are difficult to value, particularly in contested situations. Using a case study in Canterbury, New Zealand, a combination of Q method and a choice experiment is presented as a robust and transparent way to identify important cultural services of streams and rivers, and to assess their relative values. Empirical insights are offered, methodological issues discussed, and management implications identified.

Spatial and temporal patterns of surface water quality and ichthyotoxicity in urban and rural river basins in Texas

The Double Mountain Fork Brazos River (Texas, USA) consists of North (NF) and South Forks (SF). The NF receives urban runoff and twice-reclaimed wastewater effluent, whereas the SF flows through primarily rural areas. The objective of this study was to determine and compare associations between standard water quality variables and ichthyotoxicity at a landscape scale that included urban (NF) and rural (SF) sites. Five NF and three SF sites were sampled quarterly from March 2008 to March 2009 for specific conductance, salinity, hardness, pH, temperature, and turbidity; and a zebrafish (Danio rerio) embryo bioassay was used to determine ichthyotoxicity. Metal and nutrient concentrations at all sites were also measured in addition to standard water quality variables in spring 2009. Principal component analyses identified hardness, specific conductance, and salinity as the water variables that best differentiate the urban NF (higher levels) from rural SF habitat. Nutrient levels were also higher in the NF, but no landscape scale patterns in metal concentrations were observed. Ichthyotoxicity was generally higher in NF water especially in winter, and multiple regression analyses suggested a positive association between water hardness and ichthyotoxicity. To test for the potential influence of the toxic golden alga (Prymnesium parvum) on overall ichthyotoxicity, a cofactor known to enhance golden alga toxin activity was used in the bioassays. Golden alga ichthyotoxicity was detected in the NF but not the SF, suggesting golden alga may have contributed to overall ichthyotoxicity in the urban but not in the rural system. In conclusion, the physicochemistry of the urban-influenced NF water was conducive to the expression of ichthyotoxicity and also point to water hardness as a novel factor influencing golden alga ichthyotoxicity in surface waters.

農村河川における生活排水起因の医薬品濃度の実態と特徴

15 kinds of pharmaceuticals were measured for 8 sampling points in the rural rivers. It was clarified that all of the sampling points was contaminated with various pharmaceuticals. Ultraviolet absorber, insect repellents, and anti-inflammatory analgesic antipyretic were detected in higher concentration in the all sampling points than in the urban river. Ketoprofen (anti-inflammatory analgesic antipyretic for mainly internal use) was estimated as the highest risk contaminants in the measured contaminants in this research for aquatic ecosystem. Ketoprofen was only detected in the river having many Gappei-shori johkasou. These results indicated the potential significance of measures to pharmaceuticals pollution in rural area.

Nationwide monitoring of selected antibiotics: Distribution and sources of sulfonamides, trimethoprim, and macrolides in Japanese rivers

We report the results of a nationwide survey of commonly used human and veterinary antibiotics (7 sulfonamides, trimethoprim, and 4 macrolides) in 37 Japanese rivers. Concentrations of the sum of the 12 target antibiotics ranged from undetectable to 626ng/L, with a median of 7.3ng/L for the 37 rivers. Antibiotics concentrations were higher in urban rivers than in rural rivers and were correlated with those of molecular markers of sewage (crotamiton and carbamazepine). Macrolides were dominant over sulfonamides in urban rivers. Sulfonamides, especially sulfamethazine (used in animals), were dominant in a few rivers in whose catchment animal husbandry is active. However, these signals of veterinary antibiotics were overwhelmed by those of human antibiotics in lower reaches of most rivers. The analysis of the antibiotics in all 88 samples showed that the target antibiotics in Japanese rivers are derived mainly from urban sewage, even though larger amounts of antibiotics are used in livestock. Most of the livestock waste-derived antibiotics are unlikely to be readily discharged to surface waters.

An investigation of the composition of the urban riparian soil propagule bank along the River Brent, Greater London, UK, in comparison with previous propagule bank studies in rural areas

Most propagule bank research has been conducted in rural areas and has emphasised agricultural soils, although research on rural riparian propagule banks has expanded rapidly over the last decade. This paper presents observations of the species abundance of plant propagules in urban riparian soils along the River Brent, Greater London, UK. The data are analysed to explore changes in species abundance of the propagule bank with depth (0–5 cm compared with 5–10 cm soil layer), with distance from the river (0–1 m, 1–2 m, 2–3 m), and at different locations on the river network. No significant differences were found in propagule abundance with soil depth or distance from the river’s edge, but significantly more species were found in the propagule bank close to the river’s edge. The species composition of the Brent’s propagule bank is then compared with riparian propagule banks from the rural rivers Dove, Frome and Tern, UK. Species richness of the Brent propagule bank samples was generally lower than was found in the three rural rivers and, in total, 21%, 4%, 5% and 4% of observed species were aliens in the Brent, Dove, Frome and Tern soil samples, respectively. When the species present in the Brent’s propagule bank were compared with published data on urban garden soils in another UK city, the latter were found to support a higher number of alien species, suggesting that other propagule sources to urban river systems support lower numbers of alien species in riparian zones than domestic gardens.