The assessment of the influence of urban surface runoff on the quality of river water in the city of Brest was made. Surface runoff was studied in two phases (winter and summer) for the following parameters: pH, total suspended solids (TSS), concentration of chloride, nitrate, phosphate and ammonium ions, total oils. The results show that urban surface runoff is an important source of pollution for river waters. The components of primary concern were TSS, chloride, phosphate and ammonium ions during the winter period; phosphate and ammonium ions and oils during the summer period.

INTRODUCTION

Brest is a city in the South-West of Belarus, the regional centre with a population over 300,000 people. The city is situated on the River Mukhavets, the main stream of Brest Polesye, an important factor in the socio-economic development of the region. The Mukhavets River provides water supply, shipping, fishing and recreation for the population of the towns situated on it. The river is also the main recipient of wastewaters (Volchek et al. 2005). The Mukhavets River is the tributary of the trans-boundary Western Bug River belonging to the Baltic Sea catchment. This means that the contaminants found in the Mukhavets River contribute to the trans-boundary element transport and thus the total amount of pollutants carried by the Baltic Sea river system.

Since the middle of the twentieth century, a common practice was to discharge the runoff directly to the water streams, as for a long time the urban surface runoff was considered harmless for the aquatic environment. National regulations for surface runoff from urban territories in Belarus limits only a few parameters – total suspended solids (TSS), total oils and pH (Technical code 2012a). At the same time researchers all over the world state that surface runoff from city territories in the contemporary world is heavily polluted (Gnecco et al. 2005; Chouli et al. 2007; Göbel et al. 2007; Nevzorova 2011). Storm runoff discharges from urban areas can be the reason for various adverse effects on receiving water quality: increased toxicity due to emission from the traffic and industry (Roger et al. 1998; Han et al. 2006), nutrient pollution and eutrophication (Marsalek 2003; Bartlett et al. 2012), and deposition of the contaminated sediments (Marsalek et al. 2005). In countries with moderate climate, surface runoff in the summer period differs from the runoff in the winter period, because the runoff is formed by rain stormwater in summer and by snowmelt in winter. In the city of Brest, as well as in many other places in Belarus, the surface runoff from the majority of drainage collectors is discharged directly to the recipient river. Never the less the pollution of surface runoff is rather poorly studied.

The aim of this paper is to assess the constituents of snowmelt and rain surface runoff on the urbanized territories and to point out the pollutants that present a threat for the aquatic environment. According to this, the concentrations of inorganic ions such as chlorides, phosphates, nitrates, and ammonium, as well as TSS, pH and total content of oils were measured in the samples of atmospheric precipitation (snow and rain) and surface runoff obtained during December 2012–March 2014. The named parameters were chosen for this study because excess concentrations of nutrients have been for several years found in Mukhavets River, and chloride ions, TSS and oils are the most widespread pollutants washed with surface runoff from road surfaces.

To evaluate the impact for the surface waters the results of runoff analyses were compared to the national regulation for surface waters – the maximum permissible concentration (MPC) for the fish breeding waters (Regulation No. 43/42) and for household drinking and cultural community waters (Hygiene norms 2003). TSS, ammonium ions and oils concentrations were compared to the national regulation for the urban surface runoff discharges (Technical code 2012a). Also, samples of water from Mukhavets River upstream and downstream from the city were analysed to evaluate the input of the city surface runoff to the pollution of the river, as the surface runoff is the only type of waste discharged to the Mukhavets River from the city territory.

MATERIALS AND METHODS

Sampling

The drainage system of the city of Brest has several big collectors, which carry the storm and snowmelt surface runoff directly to the Mukhavets River. Only some of them are equipped with treatment facilities. For this study, four drainage collectors were chosen (see Figure 1).

Figure 1

General scheme of the sample points on the territory of Brest (dots show the sample points of runoff, which are the points of discharge of surface runoff to the river (collectors 1, 2, 3 and 4 chosen for the study); tetragons – the points of sampling of river water; triangle – the point of sampling of atmospheric precipitation).

Figure 1

General scheme of the sample points on the territory of Brest (dots show the sample points of runoff, which are the points of discharge of surface runoff to the river (collectors 1, 2, 3 and 4 chosen for the study); tetragons – the points of sampling of river water; triangle – the point of sampling of atmospheric precipitation).

The sampling period was from December 2012 to March 2014. The sampling was accomplished in two phases: winter period (November–March) when samples of snow and snowmelt were collected, and summer period (April–October) when samples of rain and rain surface runoff were collected.

Figure 1 presents the general scheme of the sample points. Samples of precipitation were taken during a 12 hour period, which covered the whole precipitation event for most of the samples, excluding a few cases when precipitation was longer than 12 hours. One individual sample with a total volume of 1.5 L was taken during each precipitation event. The snow samples were taken during every snow fall, which was intensive enough to give a sufficient amount of snow for analyses. Plastic sample vessels for snow were placed in a green area in the centre of the city during snow falls to prevent any accidental contamination of the samples (e.g. traffic, rubbish or pets). After the samples of snow were taken to the laboratory, they were melted at room temperature and analysed within 24 hours. The rain samples were taken during every rainfall that was able to give a sufficient amount of water for analysis (approximately 1.5 L, plastic vessels) at the same point, where the snow samples were taken. Samples were analysed within 24 hours.

The winter in Belarus is characterized by successive periods of cold and warm weather. During the winter, thaws warm enough to create the runoff (including the final snow melt in spring) occur several times. For the study, each time the thaw occurred, the runoff was sampled and analysed. The samples of the snowmelt surface runoff were taken at the ends of drainage pipes that carry effluent to the Mukhavets River in clean plastic vessels (individual samples of 1.5 L volume) and analysed within 24 hours. In the same way, samples of the rain surface runoff were taken during the summer period each time the rain was heavy enough to create an appropriate amount of runoff.

River water was sampled upstream and downstream of the city (approximately 500 m higher than the first drainage collector discharge point, and 500 m downstream from the last drainage collector discharge point) during the precipitation event in clean plastic vessels placed under the surface of the water (volume 1.5 L). Samples were analysed within 24 hours.

The total amount of snow samples was 18, the total amount of rain samples was 12, and the total amount of runoff samples was 33 during the winter period and 19 during the summer period.

Analysis

The pollutants were measured by Standard Methods (APHA 1992; Aleshka 1997). Each parameter was analysed in two parallel measurements.

TSS were measured by a gravimetric method. The paper filters with pore size 2–3 μm were weighed in weighing bottles. Then 100 mL of the sample (or a lesser volume diluted to 100 mL) was filtered through the paper filter, the filter in the same weighing bottle was dried at 105 °C, cooled to room temperature and weighed again until a constant mass value was obtained. The content of TSS was calculated as a difference between two weights.

The concentration of chloride ions was measured by a titrimetric method against silver nitrate and potassium chromate as an indicator. The concentrations of nitrate, phosphate, and ammonium ions were measured by a photometric method on a MS-122 PROSCAN Special Instruments (2010) spectrophotometer. The concentration of oils was measured by fluorimetric method on a Fluorat−02.3 M Lumex liquid analyzer (2005).

The total relative analytical errors were as follows: pH 0.2; TSS 10%; phosphate 7.85%; nitrate 9.74%; ammonium 8.73%; chloride 5%, oils 5%.

RESULTS AND DISCUSSION

The results of the analysis of precipitation are presented in Table 1; results of analysis of surface runoff are presented in Tables 2 and 3 (mean value for all parameters was calculated for each collector and on the basis of it the total mean value). Concentrations of all tested pollutants became higher in runoff compared to precipitation (see Figure 2), which indicates that pollutants were accumulated in runoff during its formation and precipitation was not the exclusive source of impurities in runoff, with the exception of phosphate and ammonium ions, a significant portion of which arise from precipitation. The pollutants in the atmospheric precipitation in Belarus have a trans-boundary origin, except reduced nitrogen, which has mainly a local origin (Struk et al. 2002).

Table 1

Results of snow and rain samples analysis

Mean value of the parameter
TSS, mg/LpHCl, mg/LNO3, mg/LPO43−, mg/LNH4+, mg/LOils, mg/L
Snow 9.5 6.45 1.5 1.45 1.78 0.6 
Rain 6.79 2.45 2.03 0.94 0.02 
MPC FB* – 6.5–8.5 300 40 0.066 0.05 – 
MPC DR** – – 350 45 3.5 2.42 – 
MPC SR*** 20 6.5–8.5 – – – 2.57 0.3 
Mean value of the parameter
TSS, mg/LpHCl, mg/LNO3, mg/LPO43−, mg/LNH4+, mg/LOils, mg/L
Snow 9.5 6.45 1.5 1.45 1.78 0.6 
Rain 6.79 2.45 2.03 0.94 0.02 
MPC FB* – 6.5–8.5 300 40 0.066 0.05 – 
MPC DR** – – 350 45 3.5 2.42 – 
MPC SR*** 20 6.5–8.5 – – – 2.57 0.3 

*MPCs and recommended pH for fish breeding waters.

**MPCs for household drinking and cultural community waters.

***MPCs and recommended pH for the urban surface runoff discharges.

Table 2

Results of snowmelt surface runoff analysis

Mean value of the parameter
TSS, mg/LpHCl, mg/LNO3, mg/LPO43−, mg/LNH4+, mg/LOils, mg/L
Collector 1 365.8 7.87 5047.8 4.46 4.96 1.63 0.16 
Collector 2 283.2 7.81 2409.2 7.52 3.03 2.57 0.11 
Collector 3 120.5 7.56 1406.5 5.7 2.53 1.31 0.14 
Collector 4 84 7.37 1864.1 8.65 4.07 0.47 0.18 
Overall mean 213.4 7.65 2681.9 6.58 3.65 1.5 0.15 
MPC FB* – 6.5–8.5 300 40 0.066 0.05 – 
MPC DR** – – 350 45 3.5 2.42 – 
MPC SR*** 20 6.5–8.5 – – – 2.57 0.3 
Mean value of the parameter
TSS, mg/LpHCl, mg/LNO3, mg/LPO43−, mg/LNH4+, mg/LOils, mg/L
Collector 1 365.8 7.87 5047.8 4.46 4.96 1.63 0.16 
Collector 2 283.2 7.81 2409.2 7.52 3.03 2.57 0.11 
Collector 3 120.5 7.56 1406.5 5.7 2.53 1.31 0.14 
Collector 4 84 7.37 1864.1 8.65 4.07 0.47 0.18 
Overall mean 213.4 7.65 2681.9 6.58 3.65 1.5 0.15 
MPC FB* – 6.5–8.5 300 40 0.066 0.05 – 
MPC DR** – – 350 45 3.5 2.42 – 
MPC SR*** 20 6.5–8.5 – – – 2.57 0.3 

*MPCs and recommended pH for fish breeding waters.

**MPCs for household drinking and cultural community waters.

***MPCs and recommended pH for the urban surface runoff discharges.

Table 3

Results of rain surface runoff analysis

Mean value of the parameter
TSS, mg/LpHCl, mg/LNO3, mg/LPO43−, mg/LNH4+, mg/LOils, mg/L
Collector 1 176.3 7.73 68.92 1.53 2.92 0.55 
Collector 2 266.5 7.96 70.81 2.79 4.06 0.81 0.18 
Collector 3 104.5 7.68 146.69 16.11 0.62 0.74 0.16 
Collector 4 8.03 52.49 7.9 2.59 0.09 0.27 
Overall mean 136.83 7.85 84.73 7.08 2.55 0.55 0.4 
MPC FB* – 6.5–8.5 300 40 0.066 0.05 – 
MPC DR** – – 350 45 3.5 2.42 – 
MPC SR*** 20 6.5–8.5 – – – 2.57 0.3 
Mean value of the parameter
TSS, mg/LpHCl, mg/LNO3, mg/LPO43−, mg/LNH4+, mg/LOils, mg/L
Collector 1 176.3 7.73 68.92 1.53 2.92 0.55 
Collector 2 266.5 7.96 70.81 2.79 4.06 0.81 0.18 
Collector 3 104.5 7.68 146.69 16.11 0.62 0.74 0.16 
Collector 4 8.03 52.49 7.9 2.59 0.09 0.27 
Overall mean 136.83 7.85 84.73 7.08 2.55 0.55 0.4 
MPC FB* – 6.5–8.5 300 40 0.066 0.05 – 
MPC DR** – – 350 45 3.5 2.42 – 
MPC SR*** 20 6.5–8.5 – – – 2.57 0.3 

*MPCs and recommended pH for fish breeding waters.

**MPCs for household drinking and cultural community waters.

***MPCs and recommended pH for the urban surface runoff discharges.

Figure 2

Comparison of the extent of the pollution (%) of snow and snowmelt runoff (a) and rain and rain surface runoff (b).

Figure 2

Comparison of the extent of the pollution (%) of snow and snowmelt runoff (a) and rain and rain surface runoff (b).

The pH of precipitation was slightly acidic, which is typical for precipitation in Belarus (Struk et al. 2002). The pH of surface runoff of both the summer and winter period was higher, than the pH of the corresponding precipitation. This increase can be explained by the accumulation of alkaline impurities (e.g. ammonium ions) and contact with alkaline compounds of the underlying surfaces.

The runoff of the winter period was much more heavily polluted, than the runoff of the summer period. This is typical for countries with a cold climate. Up to 60% of the annual loads of pollutants related to the surface runoff originate from the winter period (Marsalek 2003). The biggest input for winter was found for concentrations of chloride ions and TSS and for overall mean values was 97% and 64% respectively.

TSS and chloride ions were the primary pollutants in winter runoff because their concentration, were several times higher than national regulation levels, both for fish breeding and household drinking waters (Table 2). High concentrations of phosphate and ammonium ions (higher than national regulation levels for fish breeding waters) in snowmelt runoff also present a threat for the aquatic environment because of their potential eutrophication effects. Concentrations of TSS, oils, phosphate and ammonium ions are higher than national regulation levels in summer surface runoff (TSS and oil content higher than MPC for urban surface runoff discharge, phosphate and ammonium – than MPS for fish breeding waters).

Elevated levels of chloride ions and TSS in winter runoff originate from de-icing composites used during the winter period. Discharge of runoff with elevated levels of TSS can be the reason for several adverse effects: increased turbidity, depletion of dissolved oxygen, impairment of photosynthesis and also can be a source of secondary pollution, because the suspended particles adsorb impurities on their surface, and can release them after getting to the watercourse (Marsalek et al. 2005; Sujkova et al. 2012). Pollutants, accumulated on suspended solids, can also cause toxic effects at sites where sediments become accumulated (Karlavičienė et al. 2009).

Chloride ions are found in all types of surface waters, but the discharges of waters with high content of chloride ions pose a threat for aquatic ecosystems (Perera et al. 2013). Discharge of wastes with high levels of chloride ions can be the cause of secondary salinization of rivers (Cañedo-Argüelles et al. 2013): elevation of chloride levels can make river waters unsuitable for many freshwater limnetic organisms and unusable for potable supply. Chloride ions can also be the reason for discharge of elevated levels of metals with surface runoff, because chloride ions alter the equilibrium between adsorbed and dissolved metals in snowmelt (Bäckström et al. 2004).

On the basis of overall mean concentrations of chloride ions found in surface runoff, the total amount of chlorides discharged during the winter and summer period were calculated, and they were 90,301 tons and 656 tons respectively. These amounts are comparable to amounts of chlorides discharged annually with household waste-waters (approximately 70,000 tons) in the Republic of Belarus (National Report 2010), thus the surface runoff is the important source of pollution of water bodies with chloride ions.

The concentrations of nutrients are well known to play a key role in determining the ecological status of aquatic systems (Jarvie et al. 1998). Excess concentrations of nutrients in water bodies can lead to diverse problems such as toxic algal blooms, loss of oxygen, fish kills, loss of biodiversity, loss of aquatic plant beds, etc. Nutrient enrichment not only seriously degrades aquatic ecosystems, but impairs the use of water for drinking, industry, agriculture, recreation and other purposes (Carpenter et al. 1998; Voutsa et al. 2001). Because nitrate ion is a transformation product, it shows a reversed behaviour and increases in concentration as ammonium concentration decreases (Göbel et al. 2007), which explains why concentration of ammonium in rain is higher than in runoff (Tables 1 and 3). There are several typical sources of pollution of surface runoff with nutrients in the city territory: fertilizers from flowerbeds and lawns, plant residues and bird excrements. Yet in this study the key role of one of these or any other factors in nutrient pollution of surface runoff was not proved.

The mean concentration of oils in surface runoff was higher during the summer period than during the winter period, which is most probably explained by the specifics of the weather conditions: precipitation in summer is usually more frequent and more intense, thus more favourable conditions for accumulation and rapid wash of the oils are created. Furthermore, traffic during summer time is more intensive.

The results of the river water analysis are presented in Table 4. Impurities found in river waters downstream of the city of Brest had higher concentrations than upstream from the city, for most of the parameters. This indicates that surface runoff influences the river water quality, because the surface runoff is the only kind of waste that is discharged from the territory of the city to the Mukhavets River.

Table 4

Results of river water analysis upstream and downstream from city drainage collectors

Mean value of the parameter
pHCl, mg/LNO3, mg/LPO43−, mg/LNH4+, mg/LOils, mg/L
Upstream 8.16 21.73 2.72 2.97 0.54 0.14 
Downstream 7.94 30.94 2.85 3.1 0.63 0.16 
Difference in % −2.70 29.77 4.56 4.19 14.29 12.50 
Mean value of the parameter
pHCl, mg/LNO3, mg/LPO43−, mg/LNH4+, mg/LOils, mg/L
Upstream 8.16 21.73 2.72 2.97 0.54 0.14 
Downstream 7.94 30.94 2.85 3.1 0.63 0.16 
Difference in % −2.70 29.77 4.56 4.19 14.29 12.50 

On the basis of overall mean concentrations obtained in the study, normal amounts of precipitation for each month and typical runoff coefficients for urban territories, the total amounts of nutrients that are discharged with surface runoff during the winter period (November–March) and during the summer period (April–October) were calculated (Technical code 2012b). These amounts were compared to total amount of nutrients found in Mukhavets River in Brest for the same periods (Volchek et al. 2005; National Report 2010). For the calculation, typical concentrations of nutrients (average for 2005–2010) were used. The results are presented in Table 5.

Table 5

Total amounts of nutrients found in Mukhavets River and discharged with surface runoff

Volume, m3Amount of nutrients
NO3PO43−NH4+
Winter period RR 3.26 × 108 tons 7027.12 86.27 154.11 
SR 3.36 × 106 tons 22.16 10.57 5.03 
% of RR 0.32 12.25 3.26 
Summer period RR 4.62 × 108 tons 9958.96 122.26 218.41 
SR 7.74 × 106 tons 54.78 19.73 4.26 
% of RR 0.55 16.14 1.95 
Volume, m3Amount of nutrients
NO3PO43−NH4+
Winter period RR 3.26 × 108 tons 7027.12 86.27 154.11 
SR 3.36 × 106 tons 22.16 10.57 5.03 
% of RR 0.32 12.25 3.26 
Summer period RR 4.62 × 108 tons 9958.96 122.26 218.41 
SR 7.74 × 106 tons 54.78 19.73 4.26 
% of RR 0.55 16.14 1.95 

RR – River runoff, SR – Surface runoff from the Brest city territory.

As is seen from Table 5, the total amount of nitrate ions released with surface runoff was negligible both during the summer and the winter period. The total amount of ammonium ions was also quite small, but the amount of phosphate ions was significant (12.25 and 16.14% of the amount of phosphate ions found in river waters for the winter and the summer period respectively). Although it is commonly considered that the biggest portion of nutrients in water bodies arises from agriculture, from this very simple calculation it can be proved that surface runoff from the city territory quite significantly contributed to the pollution of Mukhavets River, and thus to pollution of Western Bug River and trans-boundary element transport, because the mouth of the River Mukhavets is very close to the city.

Appropriate treatment of the surface runoff can be a successful step to lowering the total amount of nutrients in rivers, and thus of meeting the Baltic Marine Environment Protection Commission recommendations for the river system of Baltic Sea catchment. The cumulative effect of the pollutants should be also considered when assessing the impact of urban surface runoff on river water quality, because the influence of effluent on living organisms can differ strongly from that expected on the basis of individual concentration of each pollutant.

CONCLUSIONS

In this study, assessment of the impact of urban surface runoff from the territory of the city of Brest was made. The results, presented in this paper, show that surface runoff from the territory of the city of Brest is an important source of pollution in the Mukhavets River both during the winter (November–March) and summer (April–October) periods. Surface runoff during the winter period was more heavily polluted, than surface runoff during the summer period. The components of primary concern were TSS, chloride, phosphate and ammonium ions during the winter period; phosphate ions, ammonium ions and oils during the summer period. This issue requires further research, but it is obvious, that new policy making and treatment technologies implementation are required to minimize the influence of surface runoff on the river water quality.

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