Biological indicators in relation to coastal pollution along Karnataka coast, India

Marine pollutants in relation to planktonic and benthic organisms were examined at two locations along Karnataka coast, one at Kulai (74 degrees 47.74'E and 12 degrees 55.16'N) receiving huge amount of industrial effluents from fertilizer, petroleum and chemical plants along with the sewage discharges. The other site Padubidri (74 degrees 45'E and 13 degrees 10'N) is located 20 km away, which is a typically agricultural and fishing village having no stress of industrial discharges. Although the concentrations of dissolved oxygen (DO), nutrients and trace metals in water and sediment showed marginal differences at these two locations, the concentration of petroleum hydrocarbon (PHC) remained exceptionally high with a maximum of 1523 microg/l at Kulai which is 10 times higher than that at Padubidri (144 microg/l). Biomass and population of phytoplankton and zooplankton showed that the seasonal differences were more conspicuous rather than the regional changes. Macro and meiobenthic population remained high at both the locations during the two seasons. Phytoplankton species indicated that centric diatoms such as Rhizosolenia, Leptocylindricus, Chaetoceros, Thalassiosira and Coscinodiscus contributed to > 90% of population in May and > 70% in January at Kulai. While mixed population of centric, pennate, cyanophycean and dinoflagellates prevailed at Padubidri in January. Lower species diversity and richness accompanied with dominance of fast growing centric diatoms over pennates observed at Kulai act as an index for detection of organic pollution and nutrient enrichment. Similarly, proliferation of benthic bivalves > 54% at Kulai relative to Padubidri suggests that these organisms could sustain organic and industrial pollutants. The results suggest that although Kulai receives large quantities of industrial and sewage effluents responsible for alteration of the ecosystem structure, the excellent wind-driven mixing and tidal flushing keep the waters well aerated thus reducing the severe pollution stress by dispersing the organic and other pollutants. Direct relationship of PHC with Cd and Pb as contaminants, NO3 and PO4 as oxidants of excess PHC and species diversity as promoters of phytoplankton (centric diatoms) and benthic bivalves shown by multiple regression analysis further suggest that these biological parameters could serve as indicators for detecting moderately high environmental stress at Kulai, compared to Padubidri.     

Relationship between F-specific RNA phage genogroups, faecal pollution indicators and human adenoviruses in river water

Recent studies have shown the increasing interest of F-specific RNA phage genotyping to identify major sources of faecal contamination in waters. This study, conducted in a river located in an urbanized watershed with recognized anthropogenic influences, was aimed at evaluating the relevance of direct phage genotyping by real-time RT-PCR. One hundred percent of positive results were obtained with a 5 mL aliquot of river water (n = 31). Phage distribution was modified after cultivation, since the ratio of the two most abundant genogroups (II and I) reached 1.51 log₁₀ by direct RT-PCR-based method versus 0.30 log₁₀ after cultivation (n = 8). For the first time, positive correlations between the concentrations of genogroup II, bacterial indicators and human adenoviruses were observed, which may indicate a human faecal pollution. No correlation between genogroups II and I has been revealed. The concentration of genogroup I was only correlated with water turbidity, suggesting an animal pollution coming from upstream after rainfall events. Among the microbiological parameters studied, only genogroup II/genogroup I ratio shows variations occurring in the major sources of faecal pollution.     

Sustainable reduction in the flux of microbial compliance parameters from urban and arable land use to coastal bathing waters by a wetland ecosystem produced by a marine flood defence structure

'Natural' treatment systems such as wetlands and reed beds have been proposed as sustainable means of reducing fluxes of faecal indicator organisms (FIOs) to recreational and shellfish harvesting waters. This is because FIO fluxes to coastal waters from both point (effluent) and diffuse (catchment) sources can cause non-compliance with microbiological standards for bathing and shellfish harvesting waters. The Water Framework Directive requires competent authorities in the member states to manage both point and diffuse sources of FIOs in an integrated manner to achieve compliance with 'good' water quality as defined in a series of daughter Directives. This study was undertaken to investigate the relative sources of FIOs to the popular bathing waters around Clacton, UK. In this predominantly arable (mainly cereal cropping) farming area, the principal land use predictor, explaining 76% of the variance in geometric mean presumptive Escherichia coli concentration at sub-catchment outlets during the bathing season, was the proportion of built-up (i.e. urbanised) land in each sub-catchment. This new finding contrasts with earlier studies in livestock farming regions where the proportion of improved grassland has proven to be the strongest predictor of microbial concentration. Also novel in this investigation, a flood defence wall has been built creating a wetland area which discharges every tidal cycle. The wetland produces over 97% reduction in the flux and concentrations of FIOs to the marine recreational waters. Also, FIO concentrations in water draining through the wetland to the sea were similar to concentrations measured in six UK sewage treatment plant effluents subject to secondary (biological) treatment followed by UV disinfection.     

Development of microbial and chemical MST tools to identify the origin of the faecal pollution in bathing and shellfish harvesting waters in France

The microbiological quality of coastal or river waters can be affected by faecal pollution from human or animal sources. An efficient MST (Microbial Source Tracking) toolbox consisting of several host-specific markers would therefore be valuable for identifying the origin of the faecal pollution in the environment and thus for effective resource management and remediation. In this multidisciplinary study, after having tested some MST markers on faecal samples, we compared a selection of 17 parameters corresponding to chemical (steroid ratios, caffeine, and synthetic compounds), bacterial (host-specific Bacteroidales, Lactobacillus amylovorus and Bifidobacterium adolescentis) and viral (genotypes I-IV of F-specific bacteriophages, FRNAPH) markers on environmental water samples (n = 33; wastewater, runoff and river waters) with variable Escherichia coli concentrations. Eleven microbial and chemical parameters were finally chosen for our MST toolbox, based on their specificity for particular pollution sources represented by our samples and their detection in river waters impacted by human or animal pollution; these were: the human-specific chemical compounds caffeine, TCEP (tri(2-chloroethyl)phosphate) and benzophenone; the ratios of sitostanol/coprostanol and coprostanol/(coprostanol+24-ethylcopstanol); real-time PCR (Polymerase Chain Reaction) human-specific (HF183 and B. adolescentis), pig-specific (Pig-2-Bac and L. amylovorus) and ruminant-specific (Rum-2-Bac) markers; and human FRNAPH genogroup II.     

Using faecal sterols from humans and animals to distinguish faecal pollution in receiving waters

The sterol content of faeces from humans and 14 species of animals common to rural or urban environments were examined. The major human faecal sterol was the 5β-stanol, coprostanol which constituted ≈ 60% of the total sterols found in human faeces. The sterol profiles of herbivores were dominated by C₂₉ sterols and 5β-stanols were generally in equal or greater abundance than 5-stanols. The principal faecal biomarker of herbivores was 24-ethylcoprostanol. The sterol content of bird faeces was extremely variable and largely dependent on the animals diet. Both 5β and 5 stanols were in very low abundance in birds and dogs faeces from this study presumably due to the absence or low activity of the necessary anaerobic biota required to reduce Δ⁵- or Δ^5,22-sterols to stanols. Cats and pigs were the only animals that had similar faecal sterol profiles to humans. However, the concentration of the principal human biomarker coprostanol was some 10 times more abundant on a dry weight basis in the faeces of humans than in those of cats and pigs. The source specificity of faecal sterol biomarkers is a combination of sterol intake, metabolic production of sterols and the biota resident within the animal's digestive tract. The “sterol fingerprints” of the faeces of humans and animals are sufficiently distinctive to be of diagnostic value in determining whether faecal pollution in water samples are of human or animal origin.     

Occurrence and levels of indicator bacteriophages in bathing waters throughout Europe

Somatic coliphages, F-specific RNA bacteriophages, bacteriophages infecting Bacteroides fragilis, Escherichia coli and enterococci were counted in bathing waters in the late spring and summer. We tested fresh and marine bathing waters from North, South, East and West Europe expected to contain between 100 and 500 E. coli per 100 ml, although wider ranges were sometimes found. Bacteriophages were counted after concentration, since a preliminary study proved that this step was necessary to obtain positive counts. During monitoring, a first-line quality control with reference materials for bacteria and bacteriophages was performed by all the laboratories participating in the study. The same microbes were also counted in raw sewage samples from various areas in Europe, where the bacterial indicators and the three groups of bacteriophages were detected in roughly the same numbers. All groups of bacteriophages were detected in both fresh and marine bathing waters throughout Europe. Reliable and complete results from 147 samples showed that for log-transformed values, E. coli and bacteriophages were slightly correlated. However, the slope of the regression line changed according to E. coli concentration and the correlation diminished when this concentration was close to zero per 100 ml. The ratios between E. coli and phages in bathing waters differed significantly from those in sewage. The relative amounts of bacteriophages, mainly somatic coliphages and phages infecting Bact. fragilis RYC2056, increased in bathing waters with low E. coli concentration, especially in seawater samples containing <100 E. coli per 100 ml. The relationship of bacteriophages with respect to enterococci paralleled that of bacteriophages with respect to E. coli. Somatic coliphages and bacteriophages infecting Bact. fragilis are useful to predict the presence of some pathogens with the same origin as present bacterial indicators but with higher survival rates.     

Occurrence of filamentous fungi and yeasts in three different drinking water sources

In order to determine the occurrence of fungi in different drinking water sources and capture variability in terms of matrix composition and seasonal effects, surface water, spring water, and groundwater samples were collected in numerous sampling events. The occurrence and significance of fungi detected in the different water sources are reported and discussed in terms of colony-forming units per millilitre and by the identification of the most frequently detected isolates, at the species level, based on morphology and other phenotypic characters. All the samples were also analyzed in terms of total coliforms and Escherichia coli that are widely monitored bacteria considered as microbiology indicators of water quality. All the groundwater samples showed significantly lower levels of total coliforms, E. coli, and fungi compared to the surface and spring water samples. No significant correlations were found between the levels of fungi detected in all the matrices and the physico-chemical parameters and bacteria regularly monitored by drinking water utilities. Fifty-two fungi isolates were identified in this study, most of which have never been described to occur in water sources. The results obtained show that fungi occur widely in drinking water sources and that further studies should be conducted to address their biodegradation potential as well as if the drinking water treatment processes currently used are effective in removing these organisms and the potential secondary metabolites produced.     

Sourcing faecal pollution: a combination of library-dependent and library-independent methods to identify human faecal pollution in non-sewered catchments

Library-dependent (LD) (biochemical fingerprinting of Escherichia coli and enterococci) and library-independent (LI) (PCR detection of human-specific biomarkers) methods were used to detect human faecal pollution in three non-sewered catchments. In all, 550 E. coli isolates and 700 enterococci isolates were biochemically fingerprinted from 18 water samples and compared with metabolic fingerprint libraries of 4508 E. coli and 4833 enterococci isolates. E. coli fingerprints identified human unique biochemical phenotypes (BPTs) in nine out of 18 water samples; similarly, enterococci fingerprints identified human faecal pollution in 10 water samples. Seven samples were tested by PCR for the detection of biomarkers. Human-specific HF134 Bacteroides and enterococci surface protein (esp) biomarkers were detected in five samples. Four samples were also positive for HF183 Bacteroides biomarker. The combination of biomarkers detected human faecal pollution in six out of seven water samples. Of the seven samples analysed for both the indicators/markers, at least one indicator/marker was detected in every sample. Four of the seven PCR-positive samples were also positive for one of the human-specific E. coli or enterococci BPTs. The results indicated human faecal pollution in the studied sub-catchments after storm events. LD and LI methods used in this study complimented each other and provided additional information regarding the polluting sources when one method failed to detect human faecal pollution. Therefore, it is recommended that a combination of methods should be used to identify the source(s) of faecal pollution where possible.     

Past and future trends in nutrients export by rivers to the coastal waters of China

We analyzed the past and future trends in river export of dissolved and particulate nitrogen (N), phosphorus (P) and carbon (C) to the coastal waters of China, for sixteen rivers, as calculated by the Global NEWS models (Nutrient Export from WaterSheds). Between 1970 and 2000, the dissolved N and P export increased significantly, while export of other nutrients changed less. We analyzed the future trends (2000-2050) for the Millennium Ecosystem Assessment (MEA) scenarios. In general, the largest increases of dissolved nutrients export are projected for the Global Orchestration scenario, assuming a globalized world and a reactive approach toward environmental management. Future trends in river export of nutrients vary largely among basins, nutrient forms and scenarios. We calculate both increasing and decreasing trends between 2000 and 2050. We also identify the sources contributing to the nutrient export. For selected river basins we present results for alternative scenarios, which are based on the Global Orchestration scenario, but assume more environmental management. This illustrates how the NEWS models can be useful in regional analyses for decision making.     

Evaluation of human adenovirus and human polyomavirus as indicators of human sewage contamination in the aquatic environment

Discharge of inadequately treated human wastewater into surface waters used for recreation, drinking water, irrigation and shellfish cultivation may present a public health hazard due to the potential shedding of high concentrations of pathogenic viruses from the human gastrointestinal tract. Human adenovirus (HAdV) and human polyomavirus (HPyV) are ubiquitous in humans and have excellent survival characteristics in the environment, so are potential candidates for indicators of human sewage contamination. Using qPCR assays, the prevalence and quantity of HAdV and HPyV JC and BK were determined in influent and effluent wastewater and receiving waters (river, urban stream, estuarine), then compared with norovirus (NoV) presence, a significant human pathogen which is not necessarily ubiquitously excreted into the environment. HAdV and HPyV were frequently detected in high concentrations in wastewater and wastewater-contaminated waters confirming their use as potential indicators for the presence of human sewage. Overall, there was a correlation between the presence of HAdV and HPyV with NoV but there were some notable exceptions including the higher frequency of NoV compared to HAdV and HPyV in estuarine waters impacted by wastewater overflows. We found that HAdV and HPyV detection by qPCR was a suitable tool for evaluating water quality and that their detection can aid in determining pollution sources, thus providing useful information for health risk assessments.     

Coliphages as an indicator of faecal pollution in water. Its relationship with indicator and pathogenic microorganisms

The study was designed to test the proposal that Escherichia coli specific bacteriophages might serve as universal faecal pollution indicators in water. A highly specific, sensitive and rapid technique for the detection and quantification of these virus particles was developed. The numerical relationship between E. coli and its parasitic phages was investigated in three different aqueous ecosystems such as sea water in the vicinity of sewage outfalls, river water contaminated by domestic and industrial sewage discharges, and estuarine waters, and found to be very close. In addition, the results obtained indicate that the coliphages are good indicators of the presence of the pathogenic microorganisms studied. In nearly all the water samples tested, the results suggest that coliphages are better indicators of faecal pollution than the classical indicator systems currently employed.     

Occurrence of enteric viruses and faecal indicators in submarine groundwater discharges in the coastal environment of the Mexican Caribbean

The occurrence of faecal microorganisms such as total coliforms (TCs), Escherichia coli (E. coli), coliphages (somatic and F+ specific) and the genomes of faecal viruses: human adenovirus (HAdV), norovirus (NoV) genogroup I (GI) and II (GII), enterovirus (EV), aichi virus (AiV) and Pepper mild mottle virus (PMMoV), was explored in submarine groundwater discharges (SGDs) in the Mexican Caribbean. Ultra-filtrated water samples were subjected to nucleic acid extraction and real-time quantitative polymerase chain reaction (PCR). Results showed the presence of TC bacteria at all sites, whereas the detection of E. coli occurred only during the dry season. Coliphages occurred during the rainy and dry seasons, with concentrations ranging from 10 to 2560 plaque forming units (PFU/100 ml). HAdV and AiV were detected in 50% and 41% of the samples, at concentrations ranging from 10² to 10⁴ genome copies per litre (GC/L) and from 10² to 10⁶ GC/L, respectively. NoV GI and II were detected in 25% and 16% of the samples, at concentrations of 10¹ GC/L and 10²–10³ GC/L, respectively. PMMoV was detected in 50% of the samples at concentrations ranging from 10¹ to 10³ GC/L. The EV genomes were not detected. These findings demonstrate that faecal microorganisms can be transported through SGDs in the Mexican Caribbean, potentially contributing to human health risks for recreation.     

Decay of intestinal enterococci concentrations in high-energy estuarine and coastal waters: towards real-time T90 values for modelling faecal indicators in recreational waters

Intestinal enterococci are the principal 'health-evidence-based' parameter recommended by WHO for the assessment of marine recreational water compliance. Understanding the survival characteristics of these organisms in nearshore waters is central to public health protection using robust modelling to effect real-time prediction of water quality at recreation sites as recently suggested by WHO and the Commission of the European Communities Previous models have more often focused on the coliform parameters and assumed two static day-time and night-time T90 values to characterise the decay process. The principal driver for enterococci survival is the received dose of irradiance from sunlight. In the water column, transmission of irradiance is determined by turbidity produced by suspended material. This paper reports the results of irradiated microcosm experiments using simulated sunlight to investigate the decay of intestinal enterococci in relatively turbid estuarine and coastal waters collected from the Severn Estuary and Bristol Channel, UK. High-turbidity estuarine waters produced a T90 value of 39.5 h. Low-turbidity coastal waters produced a much shorter T90 value of 6.6 h. In experiments receiving no irradiation, high-turbidity estuarine waters also produced a longer T90 of 65.1 h compared with corresponding low-turbidity coastal waters, T90 24.8 h. Irradiated T90 values were correlated with salinity, turbidity and suspended solids (r>0.8, p<0.001). The results suggest that enterococci decay in irradiated experiments with turbidity >200 NTU is similar to decay observed under dark conditions. Most significantly, these results suggest that modelling turbidity and or suspended solids offers a potential means of predicting T90 values in 'real-time' for discrete cells of a hydrodynamic model.     

Human and bovine adenoviruses for the detection of source-specific fecal pollution in coastal waters in Australia

In this study, the host-specificity and -sensitivity of human- and bovine-specific adenoviruses (HS-AVs and BS-AVs) were evaluated by testing wastewater/fecal samples from various animal species in Southeast, Queensland, Australia. The overall specificity and sensitivity of the HS-AVs marker were 1.0 and 0.78, respectively. These figures for the BS-AVs were 1.0 and 0.73, respectively. Twenty environmental water samples were collected during wet conditions and 20 samples were colleted during dry conditions from the Maroochy Coastal River and tested for the presence of fecal indicator bacteria (FIB), host-specific viral markers, zoonotic bacterial and protozoan pathogens using PCR/qPCR. The concentrations of FIB in water samples collected after wet conditions were generally higher compared to dry conditions. HS-AVs was detected in 20% water samples collected during wet conditions and whereas BS-AVs was detected in both wet (i.e., 10%) and dry (i.e., 10%) conditions. Both Campylobacter jejuni mapA and Salmonella invA genes detected in 10% samples collected during dry conditions. The concentrations of Salmonella invA ranged between 3.5 × 10² and 4.3 × 10² genomic copies per 500 ml of water Giardia lamblia β-giardin gene was detected only in one sample (5%) collected during the dry conditions. Weak or significant correlations were observed between FIB with viral markers and zoonotic pathogens. However, during dry conditions, no significant correlations were observed between FIB concentrations with viral markers and zoonotic pathogens. The prevalence of HS-AVs in samples collected from the study river suggests that the quality of water is affected by human fecal pollution and as well as bovine fecal pollution. The results suggest that HS-AVs and BS-AVs detection using PCR could be a useful tool for the identification of human sourced fecal pollution in coastal waters.     

Removal of bacterial fecal indicators, coliphages and enteric adenoviruses from waters with high fecal pollution by slow sand filtration

The aim of the present study was to estimate the performance of slow sand filtration (SSF) facilities, including the time needed for reaching stabilization (maturation), operated with surface water bearing high fecal contamination, representing realistic conditions of rivers in many emerging countries. Surface water spiked with wastewater was infiltrated at different pore water velocities (PWV) and samples were collected at different migration distances. The samples were analyzed for phages and to a lesser extent for fecal bacteria and enteric adenoviruses. At the PWV of 50 cm/d, at which somatic phages showed highest removal, their mean log₁₀ removal after 90 cm migration was 3.2. No substantial differences of removal rates were observed at PWVs between 100 and 900 cm/d (2.3 log₁₀ mean removal). The log₁₀ mean removal of somatic phages was less than the observed for fecal bacteria and tended more towards that of enteric adenoviruses This makes somatic phages a potentially better process indicator than Escherichia coli for the removal of viruses in SSF. We conclude that SSF, and by inference in larger scale river bank filtration (RBF), is an excellent option as a component in multi-barrier systems for drinking water treatment also in areas where the sources of raw water are considerably fecally polluted, as often found in many emerging countries.     

Levels and long-term trends of polychlorinated biphenyls and DDT''s in mussels collected from the Eastern Adriatic coastal waters

It is well documented that synthetic chlorinated hydrocarbon residues are widespread through the oceanic ecosystem. The Adriatic Sea, as a semi-enclosed body of water, is of special interest for an evaluation of the entry, extent and fate of the pollution by chlorinated hydrocarbons. An investigation of levels of chlorinated hydrocarbons in mussels in the eastern Adriatic coastal waters, off Croatia was performed. Samples were collected between 1972 and 1992 at a large number of stations. All these samples were analyzed by a single analytical group (mostly by the same analyst), using a uniform methodology which inter calibrated during seven international inter-calibration exercises. Mass fractions of chlorinated insecticides and polychlorinated biphenyls in mussels ranged from ND (<0.1) to 107.3 for DDT's and from ND (<0.5) to 1072 × 10⁹ wet weight for PCBs and from 19 to 35,600 for DDT's and from 52 to 103.000 × 10⁹ on an extracted organic matter basis. Averages and ranges of chlorinated hydrocarbons mass fractions in mussels from the Adriatic are compared with the data of mussels obtained in other Mediterranean areas. In all four investigated areas of the Mediterranean (II, IV, VI, and VIII) DDT total mass fractions in mussel are higher than those for the Adriatic. In areas (II, IV, and VIII) the PCB values are higher compared to the Adriatic. Linear regression analysis of pollutant mass fractions in the mussel samples from the eastern Adriatic coastal waters collected during the 20-year period with the years of collection show that a statistically significant negative correlation coefficient is obtained by comparing the values of total DDT mass fractions. For PCBs, a slight negative correlation coefficient is obtained but it is not statistically significant. In the Pula area this correlation coefficient is positive, but it is also statistically non-significant.     

Occurrence of bromate, chlorite and chlorate in drinking waters disinfected with hypochlorite reagents. Tracing their origins

Bromate was first reported as a disinfection by-product from ozonated waters, but more recently it has been reported also as a result of treatment using hypochlorite solutions worldwide. The aim of this study was to study the scope of this phenomenon in the drinking waters (n = 509) of Castilla y León, Spain, and in the hypochlorite disinfectant reagents. Two thirds of the treated waters monitored were found to have bromate concentrations higher than 1 µg/l, and of them a median value of 8 µg/l and a maximum of 49 µg/l. These concentrations are higher than those reported so far, however, a great variability can be found. Median values for chlorite were of 5 µg/l, and of 119 µg/l for chlorate. Only 7 out of 40 hypochlorite feedstock solutions were negative for bromate, the rest showing a median of 1022 mg/l; and 4 out of 14 calcium hypochlorite pellets were also negative, the rest with a median of 240 mg/kg. Although bromate is cited as potentially added to water from calcium hypochlorite pellets, no reference is found in scientific literature regarding its real content. Chlorite (median 2646 mg/l) and chlorate (median 20,462 mg/l) and chlorite (median 695 mg/kg) and chlorate (median 9516 mg/kg) were also monitored, respectively, in sodium hypochlorite solutions and calcium hypochlorite pellets. The levels of chlorite and chlorate in water are considered satisfactory, but not those of bromate, undoubtedly owing to the high content of bromide in the raw brines employed by the chlor-alkali manufacturers. Depending on the manufacturer, the bromate concentrations in the treated waters may be very heterogeneous owing to the lack of specification for this contaminant in the disinfectant reagents —the European Norms EN 900 and 901 do not mention it.     

Spatial variations of storm runoff pollution and their correlation with land-use in a rapidly urbanizing catchment in China

The composition of land use for a rapidly urbanizing catchment is usually heterogeneous, and this may result in significant spatial variations of storm runoff pollution and increase the difficulties of water quality management. The Shiyan Reservoir catchment, a typical rapidly urbanizing area in China, is chosen as a study area, and temporary monitoring sites were set at the downstream of its 6 sub-catchments to synchronously measure rainfall, runoff and water quality during 4 storm events in 2007 and 2009. Due to relatively low frequency monitoring, the IHACRES and exponential pollutant wash-off simulation models are used to interpolate the measured data to compensate for data insufficiency. Three indicators, event pollutant loads per unit area (EPL), event mean concentration (EMC) and pollutant loads transported by the first 50% of runoff volume (FF50), were used to describe the runoff pollution for different pollutants in each sub-catchment during the storm events, and the correlations between runoff pollution spatial variations and land-use patterns were tested by Spearman's rank correlation analysis. The results indicated that similar spatial variation trends were found for different pollutants (EPL or EMC) in light storm events, which strongly correlate with the proportion of residential land use; however, they have different trends in heavy storm events, which correlate with not only the residential land use, but also agricultural and bare land use. And some pairs of pollutants (such as COD/BOD, NH₃-N/TN) might have the similar source because they have strong or moderate positive spatial correlation. Moreover, the first flush intensity (FF50) varies with impervious land areas and different interception ratio of initial storm runoff volume should be adopted in different sub-catchments.