Water contamination issues in Estonia : a review

This article deals with the analytical results of environmental monitoring and screening performed on the identification and sources of hazardous substances in the Estonian aquatic environment. The concentrations of hazardous substances have been studied at different sampling sites and matrices. A total of 130 hazardous substances from 12 groups of substances were investigated in the framework of the BaltActHaz project. The findings suggest that the status of the majority of Estonian surface water bodies is good: the concentrations of hazardous substances measured remained below the analytical detection limit in most of the samples analysed. The contents of only some phthalates, e.g. diisobutylphthalate, di-(2-ethylhexyl)-phthalate, and dimethylphtalate, exceeded the analytical detection limit. Monoand dibutyltin and benzene were found from some water samples in rivers. However, the content of some heavy metals as well as monoand dibasic phenols in the surface water/wastewater can still reach delicate levels, in particular in the Estonian oil shale region. The concentrations of organotin compounds are high in the areas of ports and shipyards. The assessment of the water contamination by hazardous substances indicates the relevance of the continuation of the monitoring due to its crucial role for an appropriate decision-making in the protection of the aquatic environment of Estonia. Continued monitoring is necessary to mitigate the exposure and to protect the living resources.


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There is a need for general and simultaneous action by the Member States of the European Union (EU) to protect the aquatic environment from pollution, particularly that caused by certain persistent, toxic, and bio-accumulative substances.The Republic of Estonia is one of the smallest countries in the EU.Estonia joined the EU in 2004 [ The environmental monitoring of hazardous substances originating in the Estonian environment was conducted as part of the Estonian National Environmental Monitoring Programme (NEMP) [3].It was recommended that among the priority hazardous substances in Estonia, the substances that need more attention and periodic monitoring should include monobasic phenols (sum of p-, m-, o-cresols; 3,4-, 3,5-, 2,3-, 2,6-dimethyl phenols, and phenol), dibasic phenols (sum of resorcinol, 2,5-dimethyl resorcinol, and 5-methyl resorcinol), some heavy metals [4,5] and, for geological reasons, barium [6].The NEMP includes inland, marine, and groundwater sub-programmes, but does not embrace all water environments and substances; impacts of pesticides in the intensive agricultural areas, effluent and sewage sludge are not surveyed in the framework of the NEMP.
In recent years the monitoring of hazardous substances has become more exhaustive as new substances have been included in the survey because of new requirements by the EU.Therefore, the Estonian priority substance list is not final.The objective of this article is to provide an overview of hazardous substances contaminating Estonia's aquatic environment.Upon receipt of new information, additional hazardous substances should be included in the list.Alternatively, if it can be shown that a listed substance poses no risk, the compound may be removed from the list [7][8][9][10][11][12][13]. Revised environmental quality standards (EQS) for existing priority substances could be taken into account for the first time in river basin management plans covering the period 2015-2021.The newly identified priority substances and their EQS should be taken into account in the establishment of supplementary monitoring programmes and in preliminary programmes of measures to be submitted by the end of 2018 [14].

Selection of hazardous substances and sampling matrices
The results were obtained during the course of international and national monitoring projects coordinated by the Estonian Ministry of the Environment.The concentrations of hazardous substances were studied at different Estonian sampling sites and matrices (Table 1).
The analytes, 130 hazardous substances from 12 groups (Table 1), were chosen from the list of LIFE07ENV/EE/ 000122 BaltActHaz (Baltic Actions for Reduction of Pollution of the Baltic Sea from Priority Hazardous Substances) Project.Many of these substances have not been investigated in Estonia previously.For the selection of sampling matrices, three main criteria were taken into account: solubility of substances in water, potential for bio-concentration, and persistence in the environment [7][8][9][10][15][16][17][18]20].The sampling matrices were chosen based on guidance documents on chemical monitoring of sediment and biota under the WFD [21,22].The matrices are classified as preferred, optional, and not recommended. Preferred: monitoring should be performed in this matrix. Optional: monitoring can be performed in this matrix, but also in other compartments/matrices; the choice will also be made on the basis of the degree of contamination of a particular matrix. Not recommended: monitoring in this matrix is not recommended unless there is evidence of the possibility of accumulation of the compound in this matrix [21].
Based on the aforementioned criteria and considering the potential occurrence of various substances in certain parts of the environments, the analyses of hazardous substances were carried out in the following matrices:  surface water  effluent (treated wastewater)  bottom sediment of surface waters  sewage sludge.

Chemical analyses
The analyses of samples were performed using appropriate quality assurance and quality control protocols.As the Estonian Environmental Research Centre (EERC) or any other national laboratory was not capable or certified to analyse all listed substances in Estonia, analyses were subcontracted to laboratories in Germany.The chemical analyses were carried out in two German laboratories: GALAB Laboratories GmbH and Gesellschaft für Bioanalytik Hamburg GmbH.The activity of German laboratories has been declared to be in conformity with the requirements of the standard EN ISO/IEC 17025.

Sampling sites
Within the BaltActHaz project, samples were collected from Estonian inland surface waters (SW), from surface waters along coastal areas (SW), from the bottom sediment (BS), and from effluents (treated wastewater, E), and sewage sludge of wastewater treatment plants (wastewater sludge, WS).Sampling was performed all over Estonia in May and September 2010.Sampling points and the respective matrices where samples were taken are shown in Fig. 1 and Appendix 1.
The samples were transported to the laboratory in thermo boxes with cold batteries and were placed in the refrigerator immediately after arrival.All samples were taken as two replicates, in case during transportation to Germany one of the sample bottles or jars should break.The samples were packed by the chemists of the EERC, who have previous experience in such activity.

Levels of hazardous substances in surface waters
At the beginning of the 2000s the list of priority substances included first-rate heavy metals and phenols (monobasic and dibasic phenols) [5].
In 2008, within the framework of the international project 'EU Wide Monitoring Survey of Polar Persistent Pollutants in European River Waters', 122 water samples from 27 European Union Member States were studied [12,13].Three rivers from Estonia were included in the project: the Narva, Purtse, and Emajõgi.The Narva River on the Estonian-Russian border has the largest catchment area -56 225 km 2 -in the Estonian territory; its area is 17 145 km 2 , and the mean flow rate at the river mouth is 380-400 m 3 /s.The Purtse River in the oil-shale region has a catchment area of 784 km 2 and the mean flow rate 6.7 m 3 /s.The catchment area of the Emajõgi (together with the catchment area of Lake Võrtsjärv and the catchment in Latvian territory) is 9740 km 2 , and its mean flow rate is 70 m 3 /s.
A first EU-wide data set has been created on the occurrence of polar persistent pollutants in river surface waters to be used for continental-scale risk assessment and related decisions.The level of contamination of a total of 100 European rivers and other similar bodies of flowing water were tested for 35 selected polar persistent organic compounds (POS).These included pharmaceuticals (e.g.carbamazepine, diclophenac), antibiotics (sulphamethoxazole), pesticides (e.g.2,4-D, mecoprop, bentazone, terbutylazine), perfluorinated compounds (PFCs, e.g.perfluorooctane sulphonate (PFOS), perfluorooctanoic acid (PFOA)), benzotriazoles (corrosion inhibitors), hormones (estrone, estradiol), and alkylphenolics (bisphenol A, nonylphenol).Only dissolved (liquid) in the water phase, and not suspended, material was investigated.The content of the majority of substances in three Estonian rivers included in the international project remained below the LOD (Table 2).
The fact that hazardous substances are transported to the Baltic Sea from the whole catchment area was taken into account.Within the BaltActHaz project, the samples were collected from Estonian inland surface waters and from surface waters along coastal areas, from the bottom sediment, and from effluents and sewage sludge of WWTPs.In the first round (21 Apr.-3 May 2010) all chosen substances were analysed, and in the second (13-14 Sep.2010) and third (May 2011) rounds only those substances were analysed that had very high values in the first round or for which the results were questionable for some reason.Special attention was paid to rivers with valuable food fishes (Fig. 2).The Vasalemma River (food fishes salmon and trout), which had previously not been a part of the national environmental monitoring programme, was added (Table 3).
In most cases, the concentrations of hazardous substances remained below the LOD [16] and did not exceed the environmental quality limit values [14].The concentrations of the substances that exceeded the LOD but remained below the Estonian EQS are presented in Table 4.However, the oil shale mining region continues to be problematic in terms of the concentrations of hazardous substances.
The concentrations of hazardous substances in the rivers in most cases did not exceed the established environmental quality standards and were prevailingly below the LOQ.Only the contents of a few phthalates, e.g.diisobutylphthalate, di-(2-ethylhexyl)-phthalate, and dimethylphtalate, exceeded the LOQ but still remained below the environmental quality standard.However, high concentrations of monobasic phenols were found in the water samples taken from the Kohtla, Vasalemma, Narva, and Keila rivers.Mono-and dibutyltin were found in samples from the Narva, Keila, and Kasari rivers.A high content of benzene was measured in the water of the Kunda and Pühajõgi rivers.The concentrations    --------a Keskkonnaregister -http://register.keskkonnainfo.ee/envreg/main?list=VEE&mount=view of hazardous substances in the bottom sediment of rivers were in most cases below the LOQ.However, heavy metals, such as nickel, chromium, zinc, and copper, were found in sediment from the Narva River, and high concentrations of 2.5-dimethylresorcinol were found in the sediments of the Keila, Narva, and Pühajõgi rivers [15,16].
During 2008, as an assignment from the Helsinki Commission (HELCOM), a screening study was performed in the eastern Baltic Sea environment on the occurrence of eight substances/substance groups (organotin compounds (OT), polybrominated diphenyl ethers (PBDE), hexabromocyclododecane (HBCDD), perfluorinated substances (PFAS), chlorinated paraffins, endosulphan, and phenolic substances) identified as priority hazardous substances under the Baltic Sea Action Plan.The project was funded by the Nordic Council of Ministers.Estonian coastal waters were sampled at four places: eastern (Narva Bay near Sillamäe) and western (near Dirhami) parts of the Gulf of Finland, western coast of Saaremaa Island, and Pärnu Bay [24].
In all Estonian coastal water samples analysed, PFAS (PFOS, PFOA, etc.), phenolic substances (nonylphenols and nonylphenol ethoxylates, octylphenols and octylphenol ethoxylates), bisphenol A, and triclosan were below the LOQ.From phenolic substances only 4-NP was detected above the LOQ (< 10 ng/L) in some Estonian coastal water samples (from < 10 ng/L to 66 ng/L in the coastal area near Sillamäe).Based on the results, it can be concluded that the concentrations found for different substances in the coastal waters of Table 4. List of the sampling points/monitoring stations (site numbers correspond to Fig. 1) of the rivers and Lake Peipsi where the concentrations of hazardous compounds are above the limit of detection but below the annual average value of the environmental quality standard of inland surface waters [15,16,23 Estonia were low.A single sampling and analysis of a single random sample at different sampling dates for coastal water does not enable to draw essential conclusions about the state of Estonian coastal waters [24].
In a previous study [11], the maximum concentrations of nickel and iso-nonylphenol in a water sample taken in September 2010 from coastal waters of Pärnu Bay were 0.66 μg/L and 0.39 μg/L, respectively.However, other analytes such as cadmium, lead, octylphenol, chloroform, (aminomethyl)phosphoric acid (AMPA), glyphosate, and pyrene were below the LOQs [11].
The concentrations of organotin compounds are high in the harbour areas (sampling point 20 -Sillamäe Bay) and shipyards (sampling points 21-24): EQS for tributyltin compounds is 0.0002 μg/L, but its maximum measured concentration in water samples was 0.06 μg/L.Water samples taken from Tallinn Bay in the coastal area adjacent to the Baltic Ship Repair Company contained very high concentrations of organotin compounds.Additional studies are required to check the occurrence of these substances in the Estonian aquatic environment.
Organochlorine pesticides (OCPs) have never been produced in Estonia and their import was banned in Estonia beginning in October 1967 [2,25].Under the BaltActHaz project, there were seven sampling points (Nos 27-33) in intensive agricultural regions at which pesticides were determined.Samples were taken in spring, from the end of April to the beginning of May 2010.All together 23 pesticides (among them endosulfan, chlorfenvinphos, alachlor, atrazine, isoproturon, chlorpyriphos, trifluralin, simazine, glyphosate, AMPA and MCPP and some chlorinated pesticides such as aldrin, dieldrin, endrin, isodrin, hexachlorocyclo-hexanes, etc.) were investigated.The concentrations of all these compounds were below the LOQs [15,16].
The highest concentrations of AMPA and glyphosate were found in the Räpu River in September 2010: 0.93 μg/L and 0.29 μg/L, respectively [11].However, in most cases the concentrations of pesticides were below the LOQs.These findings suggest that the status of the majority of Estonian surface water bodies is good with respect to pesticides.

Levels of hazardous substances in the effluents of wastewater treatment plants
The NEMP does not include effluents from WWTPs and sewage sludge.The results of industrial and domestic wastewater analysis were compared to the limit values for the content of hazardous substances in the effluents discharged into the public sewerage system, laid down with the 16 October 2003 Regulation No. 75 of the Minister of the Environment 'Establishing of requirements for the discharge of hazardous substances into a public sewerage system'.In regard to the content of heavy metals, the effluents of all WWTPs (Fig. 1, sampling points 1-8) were in compliance with the requirements (Table 5).However, the contents of some heavy metals were still high (Fig. 3).
In the second sampling round, in September 2010, the contents of arsenic (5.3 μg/L), lead (1.2 μg/L), nickel (6.7 μg/L), zinc (33.9 μg/L), and copper (59.4 μg/L) were the highest in the effluent of the Kohtla-Järve WWTP and the content of chromium (16.3 μg/L) in the effluent of the Keila WWTP.The content of mercury remained below the LOQ (0.05 μg/L) in all effluent samples and that of cadmium below the LOQ (0.02 μg/L) in the majority of the effluent samples (Fig. 3b).
In the COHIBA project only mercury and cadmium were measured in the effluent samples from the WWTPs.The mercury concentrations in the effluents were equal to or lower than the LOQ (0.05 μg/L).For cadmium, the highest detected concentration from effluents was 0.15 μg/L [19].The effluent samples collected in September 2010 from WWTP No. 1 (Kohtla-Järve WWTP) contained 0.63-21 μg/L of nickel and < 0.5-2 μg/L of lead.Cadmium remained below the LOQ [19].

Levels of hazardous substances in the mining and oil shale region
The north-east Estonian environmental problems are directly related to the mining and processing of oil shale in the region.The concentrations of hazardous substances still cause problems in that region.The largest industrial and energy enterprises are located there (Baltic and Estonian thermal power plants, Kunda Nordic Cement, Viru Keemia Grupp AS, Kiviõli Chemical Plant, etc.) [20,[25][26][27][28][29][30][31].
Ida-Viru county in NE Estonia was chosen as the place for carrying out the monitoring of sources of hazardous substances in May 2011 [17,18].Ida-  [15,16]).
Viru county is characterized by long-term industrial traditions and an array of manufacturing enterprises.The Kohtla-Järve WWTP (Järve Biopuhastus OÜ) participated in the monitoring as most of the enterprises in the area send their wastewater for treatment to this plant.The type of treatment on Kohtla-Järve WWTP was mechanical + biological + biological nitrogen and phosphorus + chemical phosphorus separation.In addition to effluent from industrial enterprises, the Kohtla-Järve WWTP also treats household effluents (domestic wastewater) from the towns of Jõhvi, Kiviõli, Kohtla-Järve, and Püssi, the municipality of Kohtla-Nõmme, and the village of Kukruse.
During the survey, wastewaters from four participating industrial plants (three chemical industries and one timber industry), leachate from semi-coke and ash deposits, and domestic wastewaters from the towns of Jõhvi, Kiviõli, Kohtla-Järve, and Püssi, Kohtla-Nõmme municipality, and Kukruse village were analysed (Table 6).In NE Estonia, mining and processing of oil shale are considered to be the major sources of hazardous substance contamination to surface water.Additional studies are required to verify the occurrence of the substances identified by the survey in the Estonian aquatic environment.

CONCLUSIONS AND RECOMMENDATIONS
Recent environmental monitoring and screening of the Estonian aquatic environment shows that the concentrations of hazardous substances in surface water are, in most cases, below the LOD and rarely exceed the EQS.However, the concentrations of some heavy metals and monobasic phenols (especially phenols and p-and mcresols) and dibasic phenols in some surface waters and effluents may be of concern.Further, concentrations of organotin compounds are high in ports and shipyards.The concentrations of only some phthalates, e.g.diisobutylphthalate, di-(2-ethylhexyl)-phthalate, and dimethylphtalate, exceeded the LOQ, but were below the EQS.Mono-and dibutyltin and benzene were found in some rivers.
Contamination with hazardous substances from the oil shale industry continues to be a concern in NE Estonia.In this area, surface waters are contaminated with mono-and dibasic phenols, pentachlorophenol, polycyclic aromatic hydrocarbons, organotin compounds, and phthalates.Considering the relatively high quantities of hazardous substances in the wastewater, the Kohtla-Järve WWTP copes relatively well.Even though the influent contains industrial and domestic wastewater as well as leachate from semi-coke and ash deposits, the effluent meets the environmental quality requirements of Estonian legislation.Additional studies are required to verify the occurrence of hazardous substances in the Estonian aquatic environment.The priority substances list is not final.Upon receipt of new information, hazardous substances should be added to the list.Compounds may also be removed from the list if environmental monitoring and risk assessment shows that the risk is limited.When monitoring hazardous substances in water bodies, consideration should be given to future emissions, and attention should be paid to improved conditions to minimize unwanted production and transport of hazardous substances.Care must also be taken for proper incineration of disposal of hazardous wastes.Sustainable environmental strategies for the aquatic environment should be developed as well to mitigate exposure to hazardous substances to protect living resources.
In recent years, the monitoring of hazardous substances has become more exhaustive as new substances have been included in the surveys based on requirements by the European Union.The EU Commission has conducted a review of the list of priority substances and has come to the conclusion that it is appropriate to amend the list of priority substances by identifying new substances for priority action at Union level, setting Environmental Quality Standards (EQS) for those newly identified substances, revising the EQS for some existing substances in line with scientific progress and setting biota EQS for some existing and newly identified priority substances.The revised EQS for existing priority substances should be taken into account for the first time in river basin management plans covering the period 2015 to 2021 (Directive 2013/39/EU).

ACKNOWLEDGEMENTS
This study was financed by the Estonian Ministry of the Environment under the Estonian National Water Monitoring Programme, by the Ministry of the Agriculture under the Estonian Food Safety Monitoring Programme, and by the international projects LIFE07ENV/EE/000122 'Baltic Actions for Reduction of Pollution of the Baltic Sea from Priority Hazardous Substances -BaltActHaz' and 'Control of Hazardous Substances in the Baltic Sea Region -COHIBA'.
The publication costs of this article were covered by the Estonian Academy of Sciences.APPENDIX 1 1].With the Water Framework Directive (WFD; Directive 2000/60/EC of the European Parliament and of the Council of 23 October 2000) a framework for Community action in the field of water policy was established.Directive 2008/105/EC of the European Parliament and of the Council of 16 December 2008 sets the environmental quality standards of priority

17 .
Vasalemma (the mouth of the river) -SW, BS 18. Kasari state monitoring station No. 49 -SW, BS 19.Pärnu state monitoring station No. 52 -SW, BS.Coastal waters: 20.Coast of Sillamäe Bay (eastern part of the Gulf of Finland) -SW, BS 21.BLRT Grupp AS (Baltic Ship Repair Company), Tallinn, effluents flow into Tallinn Bay -E 22. BLRT Grupp AS Company Baltic Premator dock No. 2, effluents flow into Tallinn Bay -E, WS 23.BLRT Grupp AS Company Baltic Premator dock No. 34, effluents flow into Tallinn Bay -E 24.BLRT Grupp AS Company Baltic Premator dock No. 3, effluents flow into Tallinn Bay -as dock No. 3 was not open during the time of planning sampling, it was not possible to take effluent samples from there.

Fig. 2 .
Fig.2.Contents of heavy metals in river water in the first sampling round (based on[15,16]).

Fig. 3 .
Fig. 3. Contents of heavy metals in the effluents of wastewater treatment plants (a) in the first sampling round and (b) in the second sampling round (based on[15,16]).

Table 1 .
Substances and groups of substances analysed in the water monitoring and screening projects in Estonian aquatic environment a Baltic Actions for Reduction of Pollution of the Baltic Sea from Priority Hazardous Substances.b Control of Hazardous Substances in the Baltic Sea Region.

Table 2 .
Concentrations (ng/L) of priority substances and certain other pollutants in Estonia's rivers and comparison with other European Union rivers[12,13] * LOD -limit of detection; n.a.-not applicable.

Table 5 .
Limits for the discharge of heavy metals into the public sewage system

Table 1A .
List of sampling points/monitoring stations a The numbers correspond to Fig. 1. b Monitoring station numbers of the Estonian National Environmental Monitoring Programme (NEMP).