Urban Stream Sediments Research Articles

Unraveling the interplay between seasonal variations in macroinvertebrates and microplastics in urban stream sediments

Unraveling the interplay between seasonal variations in macroinvertebrates and microplastics in urban stream sediments

Heavy metal pollution and phytotoxicity of small urban stream sediments

Heavy metal pollution and phytotoxicity of small urban stream sediments

Experiments and simulation of adsorption characteristics of typical neonicotinoids in urban stream sediments.

Sediment adsorption is one of the main environmental fates of neonicotinoids (NEOs) in aquatic environments. Little information is available on for the adsorption characteristics of NEOs on urban stream sediments. In this study, urban tidal stream sediments were collected to determine the adsorption properties of four selected NEOs. The influence of environmental factors on NEO adsorption was determined by the RSM-CCD method. The NEO adsorption rates on sediments were established by multiple regression equations. As a result, the adsorption of four NEOs onto sediments fitted a linear isotherm model. The adsorption amounts of thiacloprid (THA), clothianidin (CLO), acetamiprid (ACE), and imidacloprid (IMI) were 1.68 to 2.24, 1.71 to 2.89, 1.88 to 3.07, and 2.23 to 3.16mg/kg, respectively. The adsorption processes of four NEOs on urban sediments were favorable. Moreover, adsorption behaviors of NEOs were typical physical adsorption and readily adsorbed onto urban sediments. The adsorption processes of NEOs were exothermic reactions, and their adsorption rates decreased with increasing pH. Flow rates and organic matter contents could promote the adsorption ratios of typical NEOs. Multiple linear regression was used to assess the relationships between the adsorption rates of NEOs and environmental factors. The p-values of the fitting equations of adsorption rates were all less than 0.05. Within the ranges of concentration of the investigated factors, the multiple regression equations were able to reasonably model and predict the sorption of typical NEOs onto urban stream sediments. Therefore, the adsorption rate equations effectively predicted the NEO adsorption performance of urban streams and were helpful for controlling risk assessment of NEOs.

Concentrations, Sources and Ecological Risk of Organochlorine Pesticides in Urban Stream Sediments of Suzhou Industrial Park, China

ABSTRACT The concentrations, potential sources, and ecological risk of fifteen organochlorine pesticides (OCPs) in urban stream sediments of a Chinese national demonstration eco-industrial park, the Suzhou Industrial Park (SIP), were investigated. ∑OCPs in the sediments were 1.0– 23 ng g−1 (mean = 9.9 ± 5.0 ng g−1). Generally, HCHs and DDTs were the predominant OCPs and contributed 81% of ∑OCPs. Influenced by the difference in hydrological conditions and OCP use history, levels of OCPs in the sediments of the central area of SIP were lower than those of the outer region. Based on the source analysis, HCHs in the sediments were primarily influenced by the historical usage of technical HCH, and DDTs in the sediments were largely influenced by decayed technical DDT and dicofol. Endosulfans and chlordanes in the sediments were largely influenced by weathered sources. Ecological risk analysis suggested OCPs in sediments of most sampling sites would lead to a moderate toxic effect on sediment-dwelling organisms.

Polycyclic aromatic hydrocarbons (PAHs) in urban stream sediments of Suzhou Industrial Park, an emerging eco-industrial park in China: Occurrence, sources and potential risk

In this study, urban stream sediment samples were collected in the Suzhou Industrial Park (SIP), one of the earliest national demonstration eco-industrial parks of China. PAHs were analyzed in these sediments, and concentrations of total PAHs were 180–81,000 ng g−1 (5700 ± 14,000 ng g−1). Medium molecular weight (4- ring) PAHs were predominant (42 ± 12%), followed by high molecular weight (5- and 6- ring) PAHs (31 ± 10%). No correlation was found between concentrations of PAHs and land uses of SIP in this study. Diagnostic ratios and a positive matrix factorization (PMF) model indicated that coal/biomass combustion might be the primary PAH source (61%), followed by non-combustion sources (21%) and vehicular emission (18%). According to the spatial analysis, PAHs in the sediments of SIP might be mainly associated with the coal/biomass combustion in the northeast industrial zone. Residential & commercial activities seem not to be the major causes of PAH contamination. Total PAH toxic equivalent concentrations, effect range low/effect range median values, and mean effects range–median quotient all showed that PAHs were present at a low toxicity risk level in most regions of the SIP. However, vigilance is required at some sampling sites with extremely high PAH concentrations or high mean effects range–median quotient.

Experimental shifts of hydrologic residence time in a sandy urban stream sediment–water interface alter nitrate removal and nitrous oxide fluxes

The sediment–water interfaces (SWI) of streams serve as important biogeochemical hotspots in watersheds and contribute to whole-catchment reactive nitrogen budgets and water-quality conditions. Recently, the SWI has been identified as an important source of nitrous oxide (N2O) produced in streams, with SWI residence time among the principal controls on its production. Here, we conducted a series of controlled manipulations of SWI exchange in an urban stream that has high dissolved N2O concentrations and where we concurrently evaluated less-mobile porosity dynamics. Our experiments took place within isolated portions of two sediment types: a coarse sandy stream bed resulting from excess road-sand application in the watershed, and a coarse sand mixed with clay and organic particles. In these manipulation experiments we systematically varied SWI vertical-flux rates and residence times to evaluate their effect on the fate of nitrate and production rates of N2O. Our experiments demonstrate that the fate and transport of nitrate and N2O production are influenced by hydrologic flux rates through SWI sediments and associated residence times. Specifically, we show that manipulations of hydrologic flux systematically shifted the depth of the bulk oxic–anoxic interface in the sediments, and that nitrate removal increased with residence time. Our results also support the emerging hypothesis of a ‘Goldilocks’ timescale for the production of nitrous oxide, when transport and reaction timescales favor incomplete denitrification. Areal N2O production rates were up to threefold higher during an intermediate residence-time experiment, compared to shorter or longer residence times. In our companion study we documented that the studied sediments were dominated by a long-residence-time less-mobile porosity domain, which could explain why we observed N2O production even in bulk-oxic sediments. Overall, we have experimentally demonstrated that changes to SWI hydrologic residence times and SWI substrate associated with urbanization can change the biogeochemical function of the river corridor.

The effects of heavy metals on the incidence of morphological deformities in Chironomidae (Diptera)

Streams in urban areas are strongly impacted by the input of organic matter and metals, for instance copper (Cu) and zinc (Zn). These metals are essential for the aquatic biota, but when absorbed in excess they are toxic. In Chironomidae larvae, the deleterious effects of heavy metals can be ascertained by analyzing the morphological deformities of the larval mentum, a structure of the oral cavity. In this study, we evaluated I) the bioavailability of Cu and Zn in urban stream sediments and II) the relationship between Cu and Zn concentrations and the incidence of deformities in the mentum of Chironomus larvae. Chironomid flies were collected from four locations in two streams at an urban area in southern Brazil. They were identified and the incidence of deformities in the mentum was quantified. Sediment samples were collected at the same locations where larvae were collected, to quantify the bioavailable fractions of Cu and Zn. The concentrations of Cu in the sediment were similar between the collection sites. However, Zn concentrations varied among sites, being greater in the stretch directly influenced by the input of the organic waste. In total, 2,895 Chironomid larvae were collected. The incidence of deformities in the mentum was above 30% and was correlated with the concentrations of Cu (r = 0.68) and Zn (r = 0.87). This correlation indicates that the municipal waste that is thrown into the city’s streams has influenced the occurrence of deformities.

Nitrogen-fixation activity and the abundance and taxonomy of nifH genes in agricultural, pristine, and urban prairie stream sediments chronically exposed to different levels of nitrogen loading.

Small streams exert great influences on the retention and attenuation of nitrogen (N) within stream networks. Human land use can lead to increased transport of dissolved inorganic N compounds and downstream eutrophication. Microbial activity in streams is important for maintaining an actively functioning N cycle. Chronically high N loading in streams affects the rates of the central processes of the N cycle by increasing rates of nitrification and denitrification, with biota exhibiting decreased efficiency of N use. The LINXII project measured N-cycle parameters in small streams using 15NO3- tracer release experiments. We concurrently measured N2 fixation rates in six streams of three types (agricultural, pristine, and urban prairie streams) as part of this broader study of major N-cycle processes. Nitrogen fixation in streams was significantly negatively correlated with nitrate levels, dissolved inorganic N levels, and denitrification rates. Algal mat and leaf litter samples generally exhibited the highest rates of N2 fixation. The abundance of nifH genes, as measured by real-time PCR, was marginally correlated with N2-fixation rates, but not to other N-cycle processes or stream characteristics. The nifH sequences observed were assigned to cyanobacteria, Deltaproteobacteria, Methylococcus, and Rhizobia. Seasonal changes, disturbances, and varying inputs may encourage a diverse, flexible, stable N2-fixing guild. Patchiness in the streams should be considered when assessing the overall impact of N2 fixation, since algal biomass exhibited high rates of N2 fixation.

Assessment of urban stream sediment pollutants entering estuaries using chemical analysis and multiple bioassays to characterise biological activities

Stormwater contaminants are a major source of often neglected environmental stressors because of the emphasis placed on the management of municipal and industrial wastewaters. Stormwater-derived pollutants in sediments from two New Zealand estuaries was characterised by analytical chemistry and bioassays. Contaminants were extracted from sediment using accelerated solvent extraction (ASE), recovered and concentrated by solid phase extraction (SPE), and analysed for polycyclic aromatic hydrocarbons (PAHs), selected metals, and musk fragrances. The concentrations of PAHs were below the ANZECC Interim Sediment Quality Guideline values while those of lead and zinc exceeded them in some samples. The sediment extracts containing organic contaminants exhibited acute toxicity in the zebrafish fish embryo toxicity (FET) and teratogenicity, induction of biotransformation (EROD activity), and genotoxicity (comet assay) in zebrafish. The potential of the extracts to interact with endocrine signalling processes was assessed by GeneBLAzer reporter gene bioassays and they exhibited estrogenic, androgenic, and anti-progestagenic activities.

Geochemical investigations of potentially toxic trace elements in urban sediments of Idrija

Urban areas and associated human activities (industry, traffic, processes of mining and ore extracting, etc.) have induced anthropogenic emissions of potentially toxic trace elements (PTTE), which can present risk to living organisms and ecosystems in case of enriched levels. An example of such area in Slovenia is the Idrija town, the central part of the second largest Hg mining district in the world, which is heavily contaminated with Hg in all environmental compartments. The knowledge about levels and distribution of other PTTE in Idrija is very limited due to the outstanding Hg related problems. In this study the geochemical investigation of PTTE (As, Cd, Co, Cr, Cu, Mo, Ni, Pb and Zn) was performed in urban stream and road sediments of Idrija town for the first time. In addition, solid phases of PTTE were observed using SEM/EDS and their potential sources were assessed. The results show that the levels of PTTE in urban stream and road sediments are mostly below international guidelines, except for Cu some high values were measured in road sediments. The highest Cu level was determined in the vicinity of a commutator production industry. The associations of Cu with other elements in solid phases are very diverse, which is why the analyses could not reveal the specific source of high Cu levels.

Metal contamination assessment in the urban stream sediments and tributaries of coastal area southwest Nigeria

A geochemical assessment of the fifty surface stream sediments from Ikorodu Southwest Nigeria was carried out to determine the level of contamination. The sediments were dried, disaggregated and sieved to Al > Ca > Na > Mg > K > P > Ti and were below the average shale concentration, except for Na in one sample. Results from factor and correlation analyses showed two groups of trace elements Ni, Co, Mn, U, Th, Sr, V, La, Cr, Ba, Sc, Ga, Cs, Nb, Rb, Y,Ce and Mo, Pb, Zn, As, Cd, Sb, Sn, Zr, which were from geogenic and anthropogenic sources, respectively. The enrichment factor showed that Cd, Bi, Pt, Mo and Ag were, for all samples, within background concentrations, except those of the Ogun River and the Owode Onirin, which showed significant enrichment of Cd, Zn, Cu, Pb and Ag, depletion to minimal enrichment for Bi, Mo and moderate enrichment for Pt. The contamination degree ranged between 1.25 and 143.79. The highest value was found at Owode Onirin and the lowest, at Igbonla 7. The geo-accumulation index showed that all the stream sediments ranged between practically uncontaminated to moderately to highly contaminated—with Pb, Sn, Zn, Cd, Cu, Cr, Zr and Ba. The potential ecological risk factor and environmental risk index (IER) showed that all of the samples were within the class of low to medium contamination risk, except samples from the Owode Onirin, which fell within the class of very high risk to extremely high risk respectively.

Pharmaceuticals and organochlorine pesticides in sediments of an urban river in Florida, USA

Sediments from a rural to urban gradient along the Alafia River in Florida, USA, were collected to determine the risk of environmental contamination with legacy (organochlorine pesticides (OCPs)) and new contaminants (pharmaceuticals). Bed sediments (0–10 cm) collected from rural and urban sub-basins of the Alafia River were analyzed for OCPs and pharmaceuticals using standard gas chromatography and liquid chromatography-mass spectrometry techniques. Three most frequently detected pharmaceuticals in sediments were carbamazepine (100 % of samples), trimethoprim (89 % of samples), and pseudoephedrine (63 % of samples). While acetaminophen, diphenhydramine, lidocaine, and nicotine were detected in <30 % of samples. The detection of caffeine in all sediment samples suggests that domestic wastewater from wastewater treatment plants and/or septic systems may be a contributing source at all the sites. Among the OCPs, endosulfan I was most frequently detected (37 % of samples), followed by δ-hexachlorocyclohexane (15 % of samples), γ-chlordane and endosulfan II (both in 11 % of samples), and dichlorodiphenyldichloroethylene and methoxychlor (both in 7 % of samples). The lower concentrations of OCPs (sum 0–16.1 ng g−1) than pharmaceuticals (sum 0.5–61.9 ng g−1) in sediments are probably due to the historic use of OCPs since these were banned for use in the USA in the 1970s, while pharmaceuticals are still used. The variability in detection and concentrations of legacy and new compounds in rural and urban stream sediments is likely due to the different magnitude of input sources, site characteristics, and chemical properties of individual compounds. Significant positive correlations between OCPs and sediment properties (organic matter, silt, and clay) suggest that sediments are a major sink of various contaminants in the Alafia River. We conclude that the concentrations of both pharmaceuticals and OCPs in sediments of this urban river are relatively lower than existing literature; however, these can still be of environmental concern to aquatic organisms.

Sediment–water distribution of contaminants of emerging concern in a mixed use watershed

This study evaluated the occurrence and distribution of 15 contaminants of emerging concern (CECs) in stream water and sediments in the Zumbro River watershed in Minnesota and compared these with sub-watershed land uses. Sixty pairs of sediment and water samples were collected across all seasons from four stream sites for over two years and analyzed for selected personal care products, pesticides, human and veterinary medications, and phytoestrogens. Spatial and temporal analyses indicate that pharmaceuticals and personal care products (urban/residential CECs) are significantly elevated in water and/or sediment at sites with greater population density (>100people/km2) and percentage of developed land use (>8% of subwatershed area) than those with less population density and land area under development. Significant spatial variations of agricultural pesticides in water and sediment were detectable, even though all sites had a high percentage of agricultural land use. Seasonality in CEC concentration was observed in water but not in sediment, although sediment concentrations of three CECs did vary between years. Average measured non-equilibrium distribution coefficients exceeded equilibrium hydrophobic partitioning-based predictions for 5 of the 7 detected CECs by at least an order of magnitude. Agreement of measured and predicted distribution coefficients improved with increasing hydrophobicity and in-stream persistence. The more polar and degradable CECs showed greater variability in measured distributions across different sampling events. Our results confirm that CECs are present in urban and agricultural stream sediments, including those CECs that would typically be thought of as non-sorptive based on their log Kow values. These results and the observed patterns of sediment and water distributions augment existing information to improve prediction of CEC fate and transport, leading to more accurate assessments of exposure and risk to surface water ecosystems.

Coal-tar-based sealcoated pavement: A major PAH source to urban stream sediments

We used land-use analysis, PAH concentrations and assemblages, and multivariate statistics to identify sediment PAH sources in a small (∼1303 km2) urbanizing watershed located in South-Central, Pennsylvania, USA. A geographic information system (GIS) was employed to quantify land-use features that may serve as PAH sources. Urban PAH concentrations were three times higher than rural levels, and were significantly and highly correlated with combined residential/commercial/industrial land use. Principal components analysis (PCA) was used to group sediments with similar PAH assemblages, and correlation analysis compared PAH sediment assemblages to common PAH sources. The strongest correlations were observed between rural sediments (n = 7) and coke-oven emissions sources (r = 0.69–0.78, n = 5), and between urban sediments (n = 22) and coal-tar-based sealcoat dust (r = 0.94, n = 47) suggesting that coal-tar-based sealcoat is an important urban PAH source in this watershed linked to residential and commercial/industrial land use.

Coal-tar pavement sealant use and polycyclic aromatic hydrocarbon contamination in urban stream sediments

Polycyclic aromatic hydrocarbons (PAHs) can occur at levels of environmental concern in stream sediments from urban and industrial watersheds. Recent studies indicate that coal-tar sealant use on parking lots may have been the major source of PAHs to urban streams in the eastern US over the past 40 years. This study evaluates the spatial distribution of PAHs in urban stream and pond sediments in Galloway Creek in Springfield, Missouri by focusing specifically on parking lots with and without coal-tar sealants as contamination source areas. Multiple-linear regression analysis is used to evaluate the spatial connectivity of contaminated sediment to potential source areas and compare the relative influence of watershed source factors and reach sediment variability on sediment PAH levels. Sediments from coal-tar sealed parking lots and the streams that drain them are enriched in PAHs at concentrations considered toxic to aquatic life, with concentrations that are, on average, 35 and 480 times greater than those of unsealed asphalt and concrete lots, respectively. Moreover, sediment PAH concentrations are strongly correlated with the percentage of sealed parking lot area within the upstream drainage area of the sampling site, in contrast to total parking lot area or sediment composition. Metal and nutrient contaminants are poorly correlated with sealed lot area indicating a wider range of urban source inputs. Finally, parking lots with coal-tar coatings contribute >80% of the total PAH concentration in urban stream and pond sediments in Galloway Creek. If coal-tar sealant use ended, sediment PAH concentrations would probably decrease over time to levels not harmful to sediment-dwelling organisms.

Physico-chemical characteristics of urban sediments and factors influencing ultimate methane yields

The main objective of this study was to analyze sediments in 14 urban streams in the city of Busan, South Korea, and to evaluate their biochemical methane potentials (BMP) by use of conventional BMP tests. Then chemical oxygen demand (COD), proximate analysis, volatile solids (VS), organic carbon content and elemental analysis were conducted to determine sediment characteristics. The results showed that COD, VS and organic carbon contents were 15.2 ∼ 75.1 mg/g, 2.3 ∼ 11.5% and 1.3 ∼ 34.2%, respectively. From BMP tests, the ultimate methane and carbon dioxide yield (mL/g VS) and biodegradability (%) were determined to be 10.1 ∼ 179.4, 10.3 ∼ 34.4, and 4.0 ∼ 30.1, respectively. To determine the correlations between ultimate methane yield, C/N ratio, COD, and VS and organic carbon content, a linear model was fitted to the data using a least-squares algorithm. Except for COD (r = 0.7586) and VS (r = 0.7876), the linear model was well fitted to each data point with good correlation coefficient values (r = 0.9795 ∼0.9858). A multivariate regression analysis was also performed to find multiple effects of factors on the ultimate methane yield. From these findings, empirical equations are provided that contain C/N or VS ratios for the prediction of ultimate methane yields from urban stream sediments in Busan. Key words: Sediments, urban streams, C/N ratio, chemical oxygen demand (COD) , biochemical methane potentials (BMP) test, volatile solids.

Simultaneous determination of fluoroquinolone and tetracycline antibacterials in sewage sludge using ultrasonic-assisted extraction and HPLC-MS/MS

A reliable method was proposed for the simultaneous determination of five fluoroquinolones (FQs) and two tetracyclines (TCs) in sewage sludge using ultrasonic-assisted extraction (USE) followed by SPE cleanup and high-performance liquid chromatography-mass spectrometry (HPLC-MS)/MS analysis with electrospray ionisation (ESI) in a positive mode. The USE conditions (e.g. extraction solvent, pH, and extraction cycles) and high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) parameters were optimised. Quantification was performed by internal standard calibration in multiple reaction monitoring mode. Recoveries of the antibacterials ranged from 41 to 123%, with relative standard deviations within 17%. The sample-based limits of quantification were 10–63 ng g−1 dry weight (dw) for FQs (ciprofloxacin, enrofloxacin, lomefloxacin, norfloxacin, and ofloxacin) and 250–500 ng g−1 dw for TCs (tetracycline and oxytetracycline). The method was applied to determine the antibacterials in sewage sludge and sediment samples were collected from the Pearl River Delta, China. Ciprofloxacin, norfloxacin, and ofloxacin were frequently detected, ranging from 1052 to 17740 ng g−1 dw in dewatered sludge samples, 585–3545 ng g−1 dw in untreated solids, and 98–258 ng g−1 dw in an urban stream sediment sample, respectively. Lomefloxacin and enrofloxacin were also occasionally detected.

Occurrence and Potential Sources of Pyrethroid Insecticides in Stream Sediments from Seven U.S. Metropolitan Areas

A nationally consistent approach was used to assess the occurrence and potential sources of pyrethroid insecticides in stream bed sediments from seven metropolitan areas across the United States. One or more pyrethroids were detected in almost half of the samples, with bifenthrin detected the most frequently (41%) and in each metropolitan area. Cyhalothrin, cypermethrin, permethrin, and resmethrin were detected much less frequently. Pyrethroid concentrations and Hyalella azteca mortality in 28-d tests were lower than in most urban stream studies. Log-transformed total pyrethroid toxic units (TUs) were significantly correlated with survival and bifenthrin was likely responsible for the majority of the observed toxicity. Sampling sites spanned a wide range of urbanization and log-transformed total pyrethroid concentrations were significantly correlated with urban land use. Dallas/Fort Worth had the highest pyrethroid detection frequency (89%), the greatest number of pyrethroids (4), and some of the highest concentrations. Salt Lake City had a similar percentage of detections but only bifenthrin was detected and at lower concentrations. The variation in pyrethroid concentrations among metropolitan areas suggests regional differences in pyrethroid use and transport processes. This study shows that pyrethroids commonly occur in urban stream sediments and may be contributing to sediment toxicity across the country.

Environmental fate of pyrethroids in urban and suburban stream sediments and the appropriateness of Hyalella azteca model in determining ecological risk

According to several recent studies using standard acute Hyalella azteca sediment bioassays, increased pyrethroid use in urban and suburban regions in California has resulted in the accumulation of toxic concentrations of pyrethroids in sediments of area streams and estuaries. However, a critical review of the literature indicates that this is likely an overestimation of environmental risk. Hyalella azteca is consistently the most susceptible organism to both aqueous and sediment-associated pyrethroid exposures when compared to a suite of other aquatic taxa. In some cases, H. azteca LC50 values are less than the community HC10 values, suggesting that the amphipod is an overly conservative model for community- or ecosystem-level impacts of sediment-associated pyrethroids. Further, as a model for responses of field populations of H. azteca, the laboratory bioassays considerably overestimate exposure, because the amphipod is more appropriately characterized as an epibenthic organism, not a true sediment dweller; H. azteca preferentially inhabit aquatic macrophytes, periphyton mats, and leaf litter, which drastically reduces their exposure to contaminated sediments. Sediment-bound pyrethroids are transported via downstream washing of fine particulates resulting in longer range transport but also more efficient sequestration of the chemical. In addition, site-specific variables such as sediment organic carbon content, grain size, temperature, and microbial activity alter pyrethroid bioavailability, degradation, and toxicity on a microhabitat scale. The type and source of the carbon in particular, influences the pyrethroid sequestering ability of sediments. The resulting irregular distribution of pyrethroids in stream sediments suggests that sufficient nonimpacted habitat may exist as refugia for resident sediment-dwelling organisms for rapid recolonization to occur. Given these factors, we argue that the amphipod model provides, at best, a screening level assessment of pyrethroid impacts and can correctly identify those sediments not toxic to benthic organisms but cannot accurately predict where sediments will be toxic.

Assessment of heavy metal pollution in the urban stream sediments and its tributaries

Globally, aquatic ecosystems are highly polluted with heavy metals arising from anthropogenic and terrigenous sources. The objective of this study was to investigate the pollution of stream sediments and possible sources of pollutants in Nakivubo Channel Kampala, Uganda. Stream sediments were collected and analysed for heavy metal concentration using flame atomic absorption spectrophotometer. The degree of pollution in Nakivubo channelized stream sediments for lead, cadmium, copper, zinc, manganese and iron was assessed using enrichment factor, geo-accumulation index and pollution load index. The results indicated that (1) the sediments have been polluted with lead, cadmium and zinc and have high anthropogenic influences; (2) the calculation of geo-accumulation index suggest that Nakivubo stream sediments have background concentration for copper, manganese and Fe (I geo ≤ 0); (3) factor analysis results reveal three sources of pollutants as explained by three factors (75.0 %); (i) mixed origin or retention phenomena of industrial and vehicular emissions; (ii) terrigenous and (iii) dual origin of zinc (vehicular and industrial). In conclusion, the co-precipitation (inclusion, occlusion and adsorption) of lead, cadmium and zinc with manganese and iron hydroxides, scavenging ability of other metals, very low dissolved oxygen and slightly acidic to slightly alkaline pH in stream water could account for the active accumulation of heavy metals in Nakivubo stream sediments. These phenomena may pose a risk of secondary water pollution under sediment disturbance and/or changes in the geo-chemistry of sediments.