Journal of Water Resource and Protection, 2013, 5, 40-48 Published Online April 2013 (
Advances in Water Quality Monitoring of Inorganics:
Current Trends
Florence Bullough1, Cecilia Fenech2, Helen Bridle3
1Department of Earth Science and Engineering, Royal School of Mines, Imperial College London, London, UK
2School of Biotechnology, Dublin City University, Dublin, UK
3Institute for Biological Chemistry, Biophysics and Bioengineering, Heriot-Watt University, Edinburgh, UK
Received February 8, 2013; revised March 9, 2013; accepted March 22, 2013
Copyright © 2013 Florence Bullough et al. This is an open access article distributed under the Creative Commons Attribution Li-
cense, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
New methods of analysis for water quality monitoring to detect inorganic substances are required to meet the demands
of determining concentration, particularly at low detection limits, analysing speciation and even identifying the pollu-
tion source. Such information is essential to inform public health decisions and to comply with more stringent legisla-
tion. This paper concentrates on two case studies, reviewing the development in monitoring methods, and predicting
future trends. Arsenic and nitrates detection was selected as these pollutants are particularly problematic from a human
health perspective. Additionally, the challenges faced in developing monitoring methods for these chemicals are rele-
vant to a wide range of other inorganics. The current state of the art in detection approaches for these chemicals are
discussed along with recommendations for future research to further improve the methods.
Keywords: Water Quality; Monitoring; Detection Methods; Arsenic; Nitrates; Speciation; Source Tracking
1. Introduction
In water quality monitoring simply determining the pre-
sence of pollutants is often insufficient. Accurate deter-
mination of concentrations, speciation or sources can all
be critical information to determine, for example, drink-
ing water safety or identify the origin of pollution. Pol-
lutants include pathogens, organics and inorganics.
Pathogen monitoring has been a recent subject of fo-
cus with a large EU grant recently awarded to develop
new microbial methods of detection. This has been
driven by the onset of molecular methods and the grow-
ing realisation that faecal indicator monitoring is insuffi-
ciently well-correlated with the presence of certain patho-
gens [1]. At the same time concern regarding emerging
pollutants, many of which are trace level organics have
been mounting worldwide [2,3]. These chemicals are
extremely challenging to detect at environmentally rele-
vant ng/L, and extraction and concentration methods are
a key part of addressing this problem.
However, inorganics are another major class of water-
borne pollutants, many of which have long-term chronic
impacts upon human health [4]. The aim of this paper is
to review the challenges facing monitoring for inorganic
compounds in water by focusing on two key case stud-
ies. Arsenic has been selected due to the widespread na-
ture, and huge scale, of the issue. This example describes
the challenges of meeting low detection limits, especially
for field instruments, and the issues relating to speciation.
This is a common problem for the detection, and analysis,
of inorganic waterborne contaminants. Speciation can
impact upon the fate and transport of an inorganic in the
environment as well as be a key determinant in the health
risk. Nitrates have been selected as this chemical repre-
sents one the few short-term acute exposure risks. This
example also highlights the challenges of environment
forensics in identifying the source of pollution to meet
ever-increasing legislation.
2. The Problems of Arsenic Concentration
and Speciation Detection
Arsenic contamination of drinking water, which leads to
chronic poisoning, affects more than 140 million people
across 70 countries in all six continents and is considered
as the most challenging water pollutant on a global scale
[5]. Arsenic in groundwater is a widespread contaminant
in South East Asia affecting the quality of drinking water
in Bangladesh, India [6] and Cambodia [7] and is also
present to a lesser degree in the USA [8] and in parts of
opyright © 2013 SciRes. JWARP
the UK. In Bangladesh, where the contamination is most
acute, tube-wells were dug to access shallow aquifers
with the aim of providing a microbial-free source of
drinking water. However, the groundwater has high lev-
els of arsenic; over 45% of these wells exceed the World
Health Organisation (WHO) recommendation of 10 μg/l
and 27% exceed the 50 μg/l limit set by the Bangladeshi
authorities [5]. The high concentrations of arsenic in the
main drinking water source for over 50 million people in
Bangladesh has been referred to as the largest manmade
environmental disaster in the world and “the largest mass
poisoning of a population in history” [5]. Recent studies
have estimated that arsenic groundwater contamination
in Bangladesh causes 1 in 5 deaths in the country and a
Lancet study by Argos et al. showed that those in the top
quartile of exposure suffered a 70 percent higher mortal-
ity rate than would be expected in the population as a
whole [9]. Furthermore, it has been estimated that mor-
bidity from polluted water consumption reduces the la-
bour supply by 8% [10].
Detrimental effects arising from chronic exposure to
low doses of arsenic have been demonstrated in epidemi-
ological studies, and include an array of health problems
such as skin lesions, skin, bladder, kidney and lung can-
cer, neurological disorders and cardiovascular disease [5].
Furthermore, such health problems generate many issues
both at an individual level (e.g. social stigma, loss of
income, lowered educational attendance) and at a na-
tional level (e.g. reduced labour supply, decreased pro-
ductivity, rising healthcare costs) [10,11]. Thus, provi-
sion of potable water is an essential component of pov-
erty alleviation and sustainable growth.
The release of arsenic into the environment is con-
trolled by both natural and anthropogenic processes. Ar-
senic is commonly found as part of sulphur or organic
compounds in nature and can be unleashed in a number
of ways, the mechanisms of which can be contentious.
The most commonly espoused mechanism in Bangladesh
is that of geogenic reduction of deep aquifer rocks, which
releases the arsenic into the groundwater [12]. Arsenic
compounds can be mobilised by a variety of processes
including mining runoff [13], weathering interactions,
biological activity, geochemical reactions, volcanic emis-
sions and anthropogenic processes [1], with erosion and
leaching being the largest contributing processes at 612 ×
108 and 2380 × 108 g/year respectively [14]. Arsenic is
most commonly found in the +3 and +5 oxidation states
while 3 and 0 contribute a smaller amount of the natu-
rally occurring species [14]. Adsorption onto metal ox-
ides is the most common arsenic remediation technol-
ogy as it is both cheap and effective. For a full review of
the performance of adsorbent materials see Mohan and
Pittman [12].
Arsenic is sensitive to mobilisation across the pH range
of groundwater (pH 6.5 to 8.5) [14] and under both oxi-
dising and reducing conditions. The speciation of arsenic
in natural waters is controlled by redox potential and pH,
as seen in Figure 1, with As (III) being the dominant
species in reducing conditions, such as groundwater, and
As (V) more prevalent in oxidising conditions such as
surface water. Trivalent arsenic is typically found as
As(OH)3, 4
, AsO2OH2 and 3
, while
pentavalent arsenic typically forms 4,
AsO 2
and 24
[1] as described in Figure 1.
The dominance of the uncharged As(III) species
H3AsO3 across pH 0 to ~pH 9 compared to the domi-
nance of the charged As(V) species 24
provides a significant problem for the removal
of toxic arsenic species from drinking water through ad-
sorption. Negatively charged As(V) has a preferred af-
filiation for positively charged iron oxide, a common
adsorbent material, compared to the uncharged H3AsO3
As(III) molecule. As(III) is the dominant oxidation state
in relatively reducing groundwater, is known to be 60
times more toxic than As(V) as well as more mobile [15].
Arsenic is therefore of significant concern for countries
which obtain the majority of their drinking water at depth
through tube wells that sample groundwater [16].
A large part of the arsenic problem is characterised by
the presence of both As(III) and As(V) at concentrations
exceeding the national and WHO threshold limits. The
two species behave very differently, in terms of adsorp-
tion behaviour which is the dominant removal technol-
ogy whilst As(III) is very difficult to remove through
adsorption but also difficult to detect. Discrete measure-
ment of As(III) and As(V) is not facile. Standard arsenic
analysis techniques such as atomic absorption spectro-
Figure 1. The redox potential-pH plot for Arsenic at 25˚ and
101.3 Pa [14]. Red lines delineate the typical pH of ground-
Copyright © 2013 SciRes. JWARP
metry (AAS); atomic fluorescence spectrometry (AFS);
atomic emission spectrometry (AES); differential pulse
polarography (DPP); electrothermal atomic absorption
spectrometry (ETAAS) and mass spectrometry (ICP-MS)
[17] do not measure individual species and much be used
with front-end separation techniques, such as high pres-
sure liquid chromatography (HPLC), to separate the As(III)
and As(V) oxidation states.
Following the recent reduction in threshold limit from
50 µg/L to 10 µg/L, the need for cheap and accurate spe-
cies determination of arsenic has become intensified. The
presence of As(III) at toxic levels in parts of Bangladesh
[18] has created a greater need for discrete analysis as
opposed to total arsenic. Many of the existing technolo-
gies, including Gutzeit method and the aforementioned
method are either unable to provide this distinction or
complex and expensive. Due to the nature of much of
arsenic contamination being in areas of the world with
poor infrastructure and funds for remediation technology,
arsenic analysis techniques need to be cheap, reliable,
portable as much as possible and with a very low detec-
tion limit, below 10 µg/L.
One method that has been proposed to deliver field-
tests of the bioavailable arsenic is that of genetically
modified whole-cell biosensors [19,20]. In this approach
bacteria are engineered such that a reporter gene, which
generates a signal, is paired with a contaminant sensing
component. In the presence of arsenic, the biosensors
emit a signal, which could be emission of visible light or
a pH change of the water sample. pH changes can also be
easily visualised using an indicator dye [21]. Modified
cells can be grown and then freeze dried to facilitate
transportation. Reconstitution in the field, followed by
over-night incubation (at ambient temperature), revives
the cells and activates the biosensor. Such sensors are
cheap and easy to use; however, there are challenges in
achieving low detection limits as well as the issue of
permissions for field use of genetically modified organ-
Alternatively, low detection limits can be achieved by
the voltammetric analytical technique which has been
found to accurately detect As(III) and As(V) discretely at
sub 10 µg/L concentrations [22].
Voltammetry, as a form of elemental analysis, has
been known to chemists for over 50 years [16]. It has re-
ceived more attention in recent years, particularly in the
analysis of arsenic, due to its sensitivity, low cost, reli-
ability, relatively short analysis time [17] and its unique
sensitivity for As(III) [16]. It has become particularly
useful in the area of water contamination and remedia-
tion because of its portability, which allows sample
analysis to take place at, or close to the sampling point
[16]. This avoids the issue of sample preservation be-
tween sample taking and measurement in a laboratory. In
addition to its selectivity for arsenic oxidation states, the
development of voltammetry for stand-alone field use is
of particular interest for the detection of arsenic in
groundwater [16]. This is highly significant for measur-
ing samples in situ without issues of preservation or al-
teration of the arsenic in the sample vessel.
Stripping Voltammetry exploits the electrochemically
active nature of certain metal species to determine con-
centrations. It involves the electrochemical deposition,
on application of a current, through reduction of the ele-
ment of interest on an electrode, for a given deposition
time. The element is then oxidised back into the solution
by a reverse potential scan [16]. During the deposition
time the arsenic is pre-concentrated at the electrode
which accounts for the sensitivity of the method [23].
The oxidation current which causes the stripping of the
arsenic from the electrode back into solution is recorded
and plotted against scan potential [16] to give an analyti-
cal signal.
The analysis of As(III) and As(V) is controlled
through the potential at which the solution is held prior to
stripping, where the potential is low enough to reduce the
analyte and deposit it at the electrode [16]. In our system
the As(III) determination is held at a potential 0.2 V and
total arsenic (As(III) + As(V)) determination is held at
1.2 V. In both cases the arsenic is reduced to As(0)
when it is deposited at the electrode at ~0.1 V. The dif-
ferential pulse anodic stripping voltammetric system
(DPASV), used in the work by Alves et al. and also
Saluan et al. [24] uses a three electrode system, a work-
ing electrode, on to which the element of interest is de-
posited, a reference electrode and an auxiliary electrode
all of which vary depending on the type of determination
being carried out [16]. The system is calibrated through
standard addition [18] whereby once the sample has been
analysed, an aliquot of a known stock solution of known
concentration is added to the voltammetric cell: the re-
sultant concentration is measured twice and then the
process is repeated again. The benefit of the standard
addition calibration is that each sample is calibrated indi-
vidually at the time of analysis as opposed to a calibra-
tion line which can incur more drift. This means that
some of the differences in relative conditioning of the
electrode should be removed through the standard addi-
tion method.
Electrode conditioning is a potential issue with the re-
producibility of voltammetric determinations. When not
being used, the reproducibility of data using solid elec-
trodes can be impeded due to the formation of a surface
oxide on the electrode surface, which limits sensitivity
[25]. This can cause sensitivity issues both within runs
and over the long term [16]. Electrodes are conditioned
by either immersing the electrode in an appropriate acid
or base over a period of time or electrochemically by
Copyright © 2013 SciRes. JWARP
running voltammetric cycles in a pre-determined solution.
No standard electrode pre-treatment has been established
with many researcher using acids or bases with variations
in the strength of the conditioning solution [16]. All
voltammetric techniques require efficient mass transfer
of ions in the cell so that the working electrode can ef-
fectively pre-concentrate the analyte of interest. This is
primarily achieved by a magnetic stirrer or a rotating
electrode. This local motion enhances metal deposition
[25] and can also minimise the H2 bubble formation at
the working electrode, resulting in reduced noise and
increased signal [26].
Much research has gone into optimising many parts of
the process including the material the electrode is made
from. Most commonly an Au electrode is used due to its
stability and sensitivity. In recent publications, particu-
larly from Salaun et al. they have tested an alternative Au
microwire electrode. These studies found that As(III)
could be determined in freshwaters and seawaters at any
pH, thus excluding the addition of corrosive acids as
electrolytes [27]. Optimum conditions included a deposi-
tion potential of 1.0 kv for As(III) and As(V) and 30 s
deposition time. They reported the use of 0.01 M HCl as
an electrolyte with limits of detection of 14.98 ng·L1 for
As(III) and 22.47 ng/L for As(V) [27]. Later work de-
veloped the use of cathodic stripping voltammetry (CSV)
at a vibrating gold microwire electrode, where arsenite
determination was possible with no pre-treatment of the
sample at its original pH and open to ambient air [22].
This means that this method is suitable for on-site analy-
sis. Total arsenic is then determined through the addition
of acid to pH 1. The data compared well (within 10%)
with the ASV method. To highlight the issue of sample
preservation, a study in West Bengal waters showed that
if analysed immediately then As(III) was the dominant
species, however, upon storage there was significant ox-
idation to As(V) and adsorption on particulate matter in
the solution [22]. Immediate analysis of the arsenic sam-
ples without the need for pre-treatment or expensive lab
techniques for countries such as Bangladesh would be an
important contribution to the ongoing effort to provide
safe drinking water.
3. The Challenge of Nitrate Source
Nitrate (3) occurs naturally within the environment.
However, concern regarding its ever-increasing entry
into the natural environment as a result of various an-
thropogenic sources, such as inorganic fertilisers and
effluents from wastewater treatment plants, have led to it
being considered a contaminant of concern. This is
largely as it has been linked to various environmental and
health concerns. High nitrate concentrations within water
bodies have been linked to such occurrences as eutro-
phication [28,29]. High nitrate concentrations within drink-
ing water have also been linked to methemoglobinemia
in children (blue-baby disease) [30] and cancer [31]
amongst other diseases. However, the presence of a di-
rect link is still a factor for debate [32]. These factors
have led to increasing interest in the development of en-
vironmental forensics techniques for nitrate source de-
termination, largely in relation to legislative requirements
related to the Water Framework (2000/60/EC) and Ni-
trates Directives (91/676/EEC).
To date, various approaches have been adopted in an
effort to distinguish between different sources of nitrate.
The use of nitrate stable isotope compositions has been
one of the most successful in this regard [33]. The dual
isotope approach is the most successful approach for
identifying the various sources of nitrate contamination,
where isotopic fractionation for both the nitrogen (δ15N)
and oxygen (δ18O) atoms within the nitrate ion is consid-
ered (Figure 2) e.g. [33-37].
In particular, the dual isotope approach has been useful
for the identification of hydrologic pathways [38-41].
The isotopic composition of a particular water body does
not only reflect the composition of the original source or
of mixed sources having different compositions but can
also be influenced by isotopic fractionation during the
transport and chemical transformation of the compounds
[42,43]. Therefore, it allows for the source of contamina-
tion and the pathways undertaken to be identified. How-
ever, this method is not suitable for differentiating
closely related sources of contamination, such as sewage
and manure [44]. This is because both sewage and ma-
nure undergo similar isotopic fractionation processes
leading to overlapping isotopic compositions (as seen in
Figure 2 where these elements cannot be distinguished)
A range of approaches has been utilised for specifi-
cally achieving faecal source tracking. The use of faecal
indicator bacteria (FIB) represents the most commonly
Figure 2. A general depiction of the normal range of δ18O
and δ15N values for the dominant sources of nitrate [45].
Copyright © 2013 SciRes. JWARP
adopted faecal contamination markers of water bodies.
However, whilst it is useful for the detection of faecal
contamination, it is currently not possible to distinguish
between microbial pathogens arising from human (sew-
age) or animal (manure) sources on this basis. This is
because FIB such as Escherichia coli and enterococci,
which represent the commonly used FIB, do not dis-
criminate between human and animal faecal matter
sources [46]. The ratio of faecal coliforms (FC) to faecal
streptococci (FS) was also proposed as a way to differen-
tiate sewage and manure [47]. However, as a result of
variable survival rates of the bacterial species and the
differences in FC-FS ratios within different animals, the
use of these ratios is no longer considered to be suitable
[46]. For this reason, other tracers must be used to
achieve this differentiation.
The use of molecular techniques for Microbial Source
Tracking (MST) through a variety of library dependent
and library independent methods has also been investi-
gated [48]. These include antibiotic resistance, bio-
chemical fingerprinting, DNA fingerprinting, bacterio-
phage occurrence and the use of genetic markers. How-
ever, the application of MST for achieving faecal source
tracking has met a number of challenges. Host specificity
is one of the major challenges in the development of
MST techniques. This is because, whilst it is commonly
the case that differential distribution of the particular
source identifier is present within the various sources,
such that it is found at a higher frequency or density
within certain hosts [49], it is known that a significant
level of cosmopolitan strains (strain sharing) is present,
such that incorrect source attribution might result [50,
Furthermore, particular molecular source identifiers
often also vary on temporal and spatial scales. Differ-
ences in dietary regimes are amongst the major contribu-
tors to this variability. This is because different dietary
regimes would include the presence and levels of bacte-
rial groups within the intestinal tract [49]. Hence, source
identifiers that would be relevant within a specific tem-
poral period and geographical area might not be relevant
in a different scenario [49,50]. The environmental per-
sistence of the various source identifiers selected is an-
other consideration. This is because the clonal composi-
tion of the species commonly differs between the envi-
ronmental samples and the host populations [49,52].
Lastly, practical considerations, in particular related to
the method’s transferability and applications must be
taken into account. These include factors such as the
technique’s availability and complexity, the cost of
analysis and the level of expertise required for successful
data interpretation [46].
Therefore, whilst the use of molecular techniques for
MST allows for highly specific information on the pres-
ence of faecal indicators, a number of challenges have
been identified. In fact, although multiple LDMs and
LIMs are currently available, many have not yet been
fully tested and validated to the stage of application in
field studies [48,49] and no specific method has been
shown to be superior enough to be adopted as a standard
[46]. In fact, a number of studies carried out by the US
Geological Survey project to assess available techniques
concluded that none of the methods investigated were
ready for field application [51,53]. An additional consid-
eration of using molecular techniques, is that they can
only function in the identification of the host from which
the source of nitrate (or faecal) contamination is initiated.
Therefore, using such techniques it would not be possible
to differentiate between raw and treated sources of con-
A review of recent literature has identified the use of a
suite of chemical markers, namely pharmaceuticals and
related compounds such as caffeine, as providing the
greatest potential in this regards [45]. The use of phar-
maceuticals and related compounds, such as food addi-
tives, as chemical markers of co-occurring discriminators
of sewage and manure is believed to provide the greatest
potential in this regards. They are ideal for such an ap-
plication as they are generally relatively water soluble
and non-volatile, and their natural background levels are
low. The adoption of such an approach also renders in-
creased temporal and spatial stability of the source iden-
tifiers, as opposed to the use of molecular markers, since
consumption of pharmaceuticals and related compounds
such as food additives is largely stable, at least within the
developed world.
Furthermore, due to the wide variety of such com-
pounds available, through an understanding of the che-
mical marker’s environmental persistence, biodegrada-
tion and environmental fate, it would be possible to se-
lect the most appropriate suite of chemical markers for
achieving identification of the required input. To date,
most such environmental forensics studies have focussed
on a single tracer approach. Caffeine has been one of the
most studied chemical tracers of sewage to date [54,55].
However, it is only through the use of a suite of chemical
markers, that it would be possible to achieve further
characterisation of the sewage or manure input. For ex-
ample, indicating the effectivity and the level of treat-
ment being undergone within the DWWTS.
The use of immunoassays for chemical marker detec-
tion is an emerging technique for this purpose. Immuno-
assays have been widely applied in other areas of science,
in particular clinical analyses [56]. However, despite the
first studies on using immunoassays to detect pharma-
ceutical in surface waters showing up around 10 years
ago [57] for the detection on Diclofenac, they have re-
ceived limited further attention [58-60]. This may be due
Copyright © 2013 SciRes. JWARP
to the limited availability of antibodies showing reactiv-
ity to e.g. pharmaceuticals, as well as the skills set of
environmental scientists.
However, the use of immunoassays renders a number
of advantages. Since the antibody-antigen complexes
form through relatively weak interactions, which func-
tion over short distances, a close antibody-antigen fit is
required for complex formation [61]. This confers a high
degree of specificity to antibody-antigen binding. There-
fore, they have the capability of measuring antigens
within complex matrices, with limited or no pre-treat-
ment, extraction, purification or concentration, due to the
potential for low detection limits being achieved [56].
Furthermore, they have the potential for high-throughput
analysis [56]. This is particularly related to the use of 96
(and less commonly 384) well-plates for analysis and
multi-channel pipettes, which greatly facilitate reagent
and sample handling [62]. Combined with this are mul-
tichannel-spectrophotometers, which allow for the com-
plete sample plates to be read within a few seconds [62].
As with all analytical techniques, the use of immuno-
assay techniques has a number of limitations, which need
to be considered. One of the main limitations is the po-
tential for cross-reactivity or interference within immu-
noassay analyses. Therefore, factors such as the unique-
ness of the epitope used are critical, as they determine
antibody-antigen selectivity. Furthermore, the level of
confirmatory detail on the presence of a particular ana-
lyte within a sample is reduced as compared to that ob-
tained through mass spectrometric analyses. This is es-
pecially true when considering the potential variability in
surface water matrices. However, the use of immunoas-
says has wide potential as a fast-screening method for
sample analysis, allowing for samples requiring chroma-
tographic analysis to be decreased. This is particularly
true, with the advent of multiplex screening which is a
recent development and the potential for incorporation in
lab-on-a-chip systems [63] augurs for high potential for
such screening techniques.
4. Conclusions and Future Outlook
As our two case studies illustrate, new methods of analy-
sis for inorganics in water samples are required. While
existing techniques can successfully detect the presence
of compounds, new approaches are needed to meet the
demands of determining concentration, particularly at
low detection limits, analysing speciation and even iden-
tifying the pollution source. This information is essential
to inform public health decisions and to comply with
more stringent legislation. Our first case study, arsenic
detection, illustrated the first two challenges of low de-
tection limit analysis in addition to the need to obtain
species information. Our second case study, nitrate
source determination, discussed how chemical markers
can be applied to identify the origin of pollution. In addi-
tion to these factors, new detection approaches also have
to be cheap, reliable and ideally portable. Portability en-
ables detection in the field negating the challenges of
sample processing and transportation.
This paper concentrated on two case studies and re-
viewed the challenges as well as the existing state-of-
the-art in detection technologies. For arsenic we have
seen that detection at low concentration along with spe-
ciation were key challenges, essential to appropriate risk
assessments and public health interventions. From a re-
view of the literature we found that voltammetry is one
of the most promising potential solutions to this chal-
lenge as it offers many advantages including sensitivity,
ability to speciate, low-cost and short analysis times.
Whole-cell biosensors are also interesting from the per-
spective of field testing instrument.
This paper summarised many of the recent develop-
ments to optimise the voltammetric detection approach
for arsenic. The current state of this technology still re-
quires significant research and testing to move towards
analysis with less pre-treatment of samples so as to im-
prove detection in real sea-water and terrestrial water
samples. In order to deliver field-ready instrumentation,
the stability of the samples and equipment in field sce-
narios needs to be tested as well as the reproducibility of
concentrations in complex real water samples.
For nitrate, we have seen that new environmental fo-
rensics methods are required to meet recent legislation
and enable tracing of sources of pollution. Our literature
review revealed that various methods are available in-
cluding isotope approaches, molecular methods and de-
tection of a range of chemical markers. Overall, it is ex-
pected that no single method would allow for complete
source characterisation. The most appropriate approach
largely depends upon the specific scenario and the con-
text of the study. The use of chemical markers is a rela-
tively recent development. Its use for such studies is par-
ticularly promising as it allows for the entry pathway to
be identified, such as the differentiation of raw and
treated sewage inputs. At present this approach has been
applied to a number of small scale studies and would
benefit from further research into field testing and vali-
dation of alternative analytical techniques, such as im-
munoassay analyses, to replace costly and time-intensive
chromatographic and mass spectrometric analysis, which
would facilitate catchment scale studies.
In conclusion, it is clear from this review of water-
borne inorganics detection that current approaches are
moving towards more detailed analysis and this demand
for improved information raises significant challenges
for detection technologies. However, for all the case
studies discussed here, progress is being made towards
this goal. Further research developing, characterising and
Copyright © 2013 SciRes. JWARP
validating such new techniques, for these case studies as
well as other inorganic substances, should be a priority.
5. Acknowledgements
All authors would like to acknowledge the European
Science Foundation and thank them for the organization
and invitation to the Junior Summit on Water: Unite and
Divide. FB would like to acknowledge the Department of
Earth Science and Engineering for financial support of
her PhD. CF would like to acknowledge the financial
support of the Marie Curie Initial Training Network
funded by the EU FP7 People Programme, ATWARM
(Advanced Technologies for Water Resource Manage-
ment, ITN No. 238273) HB would like to acknowledge
the Royal Academy of Engineering/EPSRC for her re-
search fellowship.
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