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Tracking micropollutants along pathways throughout a large
river basin - lessons learned from a Danube basin-wide
monitoring project
M.K. Kardos*, S. Kittlaus**, Zs. Jolánkai*, O. Szomolányi*, N. Weber**, O. Zoboli**,
A. Fekete***, R. Tonev****, O. Gabriel*****, M. B. Broer*****, R. Milacic******, K.
Marković******, A. Muntean***, S. Kulcsar*****, G. Bordós*******, M. Zessner**,
A. Clement*
* Department of Sanitary and Environmental Engineering, Budapest University of Technology and Economics,
Műegyetem rkp. 3. H-1111 Budapest, Hungary (E-mail: kardos.mate@emk.bme.hu, Tel.: +36 1 463 2955)
** Institute for Water Quality and Resource Management, TU Wien, Karlsplatz 13, 1040 Vienna, Austria
*** National Administration “Romanian Waters”, Str. Edgar Quinet nr. 6, Sector 1, 010018, Bucureşti, Romania
**** Bulgarian Water Association, Hristo Smirnenski Blvd. 1, 1046 Sofia, Bulgaria
***** Environment Agency Austria, Spittelauer Lände 5, 1090 Vienna, Austria
****** Department of Environmental Sciences, Jožef Stefan Institute, Jamova 39, 1000 Ljubljana, Slovenia
******* WESSLING Hungary Ltd, Anonymus u. 6, 1045 Budapest, Hungary
Abstract
Organic and inorganic substances have been emitted into the environment for many decades;
however, the interest in their fate and behavior has grown mainly in recent years. Due partly to the
meager amount they are present in environmental compartments such as rainwater, river water, or
waste waters, substantial resources are needed to detect their occurrence and quantify their
concentration. Mapping these substances with satisfying reliability would require unaffordable
costs for a large river basin such as the Danube River Basin, shared by 19 countries of very
different social, economic, and geographical characteristics.
In this paper, a resources-effective yet representative monitoring approach is presented, capable of
providing a detailed description of micropollutant concentration in different environmental
compartments, especially river water. The first results of applying the approach in 7
subcatchments of the Danube River Basin are presented.
Keywords
Danube River Basin; Inventory; Micropollutants; Monitoring; Multi-nationality;
INTRODUCTION
Organic and inorganic micropollutants have not been of broader interest except for the last few
decades. They are present in many environmental matrices but only in low concentrations. While
the sampling process is generally the same independently of the determinant, special and costly lab
resources are needed to quantify the amount of trace elements in environmental compartments.
Even qualified and well-equipped laboratories might face difficulties when measuring elements
present in concentrations down to or even below ng/l. At the same time, both inorganic and organic
elements might undergo physical and chemical transformation processes when stored for longer
time – in case of very low concentrations, this might have a strong influence on the measured
values. In a large river basin such as the Danube River Basin, shared by 19 countries of very
different social, economic, and geographical characteristics, emission and transport processes as
well as micropollutant regulations (policies) are very diverse.
Our goal is to present a resources-effective yet representative monitoring approach capable of
providing a detailed description of the occurrence of micropollutants in the environment. The
quantification of the pollutants supports the emission modelling of these substances on
subcatchment and also on river basin level. This paper focuses on the monitoring of river waters,
but also of other compartments important to assess the major emission pathways. The presented
approach is applied in the ongoing Interreg project Danube Hazard m3c. This paper especially
focuses on the monitoring concept and on the lessons learned related to the challenge of developing
a consistent and harmonized inventory of micropollutant concentration levels across a wide basin
with limited resources available and with the technical and logistic implications. The results of this
monitoring campaign are presented in the paper submitted in parallel by Kittlaus et al.
MATERIAL AND METHODS
The method discussed herein consists of four equally important steps to be carried out sequentially
in order to optimize the resources invested in the monitoring campaign.
As a first step, the long list of micropollutants was subdivided into groups of substances that are
expected to have common sources and undergo similar processes when released to the environment.
From each group, a restricted number (2-6) of representatives were selected as indicator substances.
It is expected that other members of the group will behave similarly in the environment to the
indicator substances.
Secondly, the possible pollution sources (in fact, the emissions) were listed along with the possible
pathways according to the EU WFD’s Common Implementation Strategy, Guidance Document Nr.
28.
Thirdly, a restricted number of pilot catchments was marked out. The diversity of the pilot
catchments shall be representative of large parts of the river basin.
The fourth step consists of the design and implementation of this monitoring program to quantify
micropollutant concentrations in the pilot catchment’s rivers throughout all the conditions that
might occur in a typical hydrological year.
RESULTS
Indicator substances and pilot catchments
Being relevant in the Danube River Basin, and representative for different pollution sources, the
following substances were selected . The heavy metals cadmium, copper, chromium, lead, mercury,
nickel, zinc; the fungicide Tebuconazole; the herbicide Metolachlor along with its metabolites
Metolachlor-ESA and Metolachlor-OA; the industrial chemicals PFOS, PFOA, along with three
phenols: Bisphenol-A, tert-Octylphenol, Nonylphenol; the 16 PAHs from the US-EPA list and the
pharmaceuticals Diclofenac and Carbamazepine. Each of these substances is expected to be
representative of their group.
In the Danube River Basin, seven pilot catchments (subbasins of the Danube River) were selected,
their area varying between 375 – 2236 km² (Table 1). Each pilot catchment was subdivided into 2
to 4 subcatchments. River sampling stations are located at the outflow point of each subcatchment
as well as the outflow point of the pilot catchment.
In each pilot region, the very same monitoring protocol is applied throughout one year.
Table 1. Characteristics of the pilot catchments.
name of the pilot catchment with
oulow point
Koppány (HU)
Tamási
Someșul Mic
(RO) Apahida
Vișeu (RO)
Moisei
Vit (BG)
Disevitza
Wulka (AT)
Schützen/Geb.
Ybbs (AT)
Greimpersdorf
Zagyva (HU)
Hatvan
Share of di-erent land uses
name of the pilot catchment with
oulow point
Koppány (HU)
Tamási
Someșul Mic
(RO) Apahida
Vișeu (RO)
Moisei
Vit (BG)
Disevitza
Wulka (AT)
Schützen/Geb.
Ybbs (AT)
Greimpersdorf
Zagyva (HU)
Hatvan
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Climate & Topography
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Hydrology
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Point sources in1uence
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Sampling of rivers
Throughout the year, six low-flow composite samples are generated as follows. Each gauge is
visited weekly, and a grab sample is taken in the case of low to midflow conditions are found on
site. In a local lab, a small portion of the grabbed sample is added to make composite samples
representative for the low- to midflow conditions of a 2-month period. Depending on the
determinant, samples are stored at very low (near 0 °C) temperatures or even frozen (for heavy
metals).
Besides the weekly grab samples, autosamplers are deployed at each gauge. The instruments are set
up to collect flow-proportional samples (or a series of samples, mixed later in the local lab flow-
proportionally) from high-flow events (above 10% - 30% durability, see Fig. 1.) Ideally, six high
flow events should be sampled throughout the year; however, this number strongly depends on
stochastic circumstances. This number is enough to indicate the variance between the events.
Figure 1. Concept of river low flow and high flow monitoring.
Continuous monitoring in rivers
At each gauge, water flow (or water level) and turbidity probes are set up, recording water level and
turbidity values every 2 to 15 Minutes. Their role is to support the decision if a particular grab
sample has to be mixed to the low- to midflow composite.
Regular cleaning and maintenance of the probes is ensured. In most locations, there is an online
transfer of data from the probes. In order to set up a robust turbidity-suspended solids functional
relationship, a sufficient number of regular and event-based grab samples is collected and analyzed
for suspended solids.
The continuous flow- and turbidity measurements, the setup of the turbidity – SS relationship,
along with the detected concentration range of micropollutants under low vs. high flow conditions,
in dissolved vs. particulate phases enables a preferably accurate determination of the annual load of
these compounds. Thus, a mass balance can be set up for each micropollutant in each pilot
catchment.
Other compartments
Besides river water, three of the most important sources is monitored to quantify their contribution
to the total loads.
Atmospheric deposition passive samplers are deployed at 2 locations in each pilot catchment; one
month (or longer, depending on the amount of rain) composite samples are collected from each
season (i.e., four samples throughout the year). Samples are immediately poured to a cooled glass
sample container after each rain event to keep it away from light and prevent decomposition.
Soil monitoring is carried out with the stratified random sampling method. In each pilot, ten strata
are defined based on land use and soil properties. In each stratum, 20 random locations are sampled
(collected from 3 to 5 subsamples) and composed to create one composite sample.
In each pilot catchment, 2 – 6 point source emitters such as urban waste water treatment plants
(monitored for both raw and treated waste water), direct industrial dischargers, and mining sites are
monitored. One-week flow proportional composite samples are created three times throughout the
sampling period.
Laboratory analysis of samples
The lab analyses are split between three laboratories – however, the work is split by determinants
rather than geographical locations. Each laboratory has made available bottles and containers
required for sampling and storage of the samples. In all compartments, total concentrations are
analysed. In river samples, dissolved concentrations of metals are also determined.
Preliminary results show that – as expected – high flow samples can be characterized by
concentrations elevated by 0 to 1 order of magnitude for both total and dissolved samples.
However, there is a substantial difference between the individual substances. In some cases, the
difference between high flow and midflow samples is more marked for total concentrations (Cr,
Hg, Ni, Pb), in others for the dissolved ones (Cd, Cu). The difference is statistically significant for
total Hg and dissolved Cu values only (see Fig. 2.).
Figure 2. Range of total (left) and dissolved (right) heavy metals concentration for high flow and
low- to midflow conditions.
CONCLUSIONS
The implementation of the monitoring program has provided many useful lessons. Although sample
collection, storage and analysis requirements are well-defined in European and international norms,
for the special circumstances determined by the composite sampling, several undefined issues were
faced. Instead of freezing the samples in glass bottles, conservation substances had to be added with
each small portion (each grab sample). Material of the sampling equipment, as well as the time of
filtration, had a substantial influence on the concentrations measured.
The well designed monitoring program, distinguishing between particulate and dissolved forms of
most determinants, between the characterisitc river flow conditions, mapping the most important
sources and pathways enables us to set up preferably accurate mass fluxes from each relevant
source or pathway. These further enables the calibration and validation of mass balance based fate
and transport models to simulate possible environmental, economical and policy scenarios along
with their evaluation.
REFERENCES
Brack, W. et al. 2017 Towards the review of the European Union Water Framework Directive: Recommendations for more efficient
assessment and management of chemical contamination in European surface water resources. Science of The Total Environment
576, 720-737. doi.org/10.1016/j.scitotenv.2016.10.104
Rügner et al. (2019): Particle bound pollutants in rivers: Results from suspended sediment sampling in Globaqua River Basins.
Science of The Total Environment 647, 645-652. doi.org/10.1016/j.scitotenv.2018.08.027
Zoboli, O. et al. (2019): Occurrence and levels of micropollutants across environmental and engineered compartments in Austria.
Journal of Environmental Management 232, 636-653. doi.org/10.1016/j.jenvman.2018.10.074