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WATER ANALYSIS / Seawater – Inorganic Compounds 283
Marine Chemistry (1993) vol. 41, Special Issue containing
reports from the HSF-NOAA-DOE sponsored Workshop
on Measurements of Dissolved Organic Carbon and
Nitrogen in Natural Waters.
Sharp JH, Carlson CA, Peltzer ET, et al. (2002) Final dissolved organic carbon broad community intercalibration
and preliminary use of DOC reference materials. Marine
Chemistry 77(4): 239–253.
Sugimura Y and Suzuki Y (1988) A high temperature catalytic oxidation method for the determination of non-volatile
dissolved organic carbon in seawater by direct injection
of a liquid sample. Marine Chemistry 24: 105–131.
Seawater – Inorganic Compounds
T D Jickells and A R Baker, University of East Anglia,
Norwich, UK
& 2005, Elsevier Ltd. All Rights Reserved.
Introduction
The oceans cover about two-thirds of the globe and
represent most of the the biggest water reservoirs on
earth. However, because humans live only on the
fringes of the oceans, they are less studied, less well
understood, and less perturbed from their pristine
state than the terrestrial environment. The chemical
analysis of the seawater itself represents a major analytical challenge that for many elements is only now
beginning to be successfully accomplished. These
problems are in part oceanographic, reflecting the
size and complexity of the ocean system, and in part
chemical, and these latter are the focus of this brief
article. This article covers the inorganic analysis of
seawater, excluding radioactive species, in both deepsea and coastal waters and excludes consideration of
gaseous species.
The dissolved ion chemistry of seawater is dominated by eight ions all present at millimolar concentrations or more, with sodium and chloride as the
overwhelmingly dominant ions (Table 1). The ratio
of these eight ions one to another is very constant in
ocean waters because the long residence time of these
ions (B106 years) allows for complete mixing of
the waters at fast rates compared to internal mixing,
Table 1 Major ion composition of seawater
Ion
Concentration (10 3 mol kg 1)
at salinity of 35
Sodium
Magnesium
Calcium
Potassium
Chloride
Sulfate
Hydrogencarbonate
Bromide
470
53
10.3
10.2
550
28
2.3
0.84
input, and removal processes. Seawater is also
strongly buffered by the hydrogencarbonate–carbonate–carbon dioxide system at about pH 8. In addition to these dissolved ions, seawater contains both
biological and abiological particulate matter, dissolved gases, and dissolved organic matter. The analysis of these phases is the subject of separate articles.
While these so-called major ions of seawater are
present at concentrations of 10 3 mol l 1 or greater,
every stable element in the periodic table is probably
present, though at much lower concentrations ranging from 10 6 down to 10 12 mol l 1 or possibly
lower still. Many of these ions display important
variations of concentrations in space and time that
are of great interest to marine scientists both in terms
of understanding the chemistry of the oceans and in
terms of monitoring environmental quality. The
challenge for chemical analysis of seawater is therefore to often measure the concentrations of ions (or
complexes) present at submicromolar concentrations
in the presence of millimolar concentrations of the
major ions.
Sampling
The first task is to collect a water sample that represents the area from which it was collected. There
are numerous problems of collecting representative
samples associated with the heterogeneity of the
biogeochemical processes in the oceans. For the analyst the concerns are related to sample integrity. The
collection of surface water samples from a small boat
can be relatively straightforward, with the sample
storage bottle being opened under water and filled by
someone leaning over the front of the boat, taking
great care to avoid contaminating the sample with
surface films on the water or emissions from the
boat. On larger vessels, devices capable of continuously pumping uncontaminated surface water samples into the ship’s laboratories are now available.
The task is more difficult when considering the collection of samples from water depths of several
kilometers. Many early sampling campaigns used
inappropriate collection systems, resulting in the
284 WATER ANALYSIS / Seawater – Inorganic Compounds
reporting of erroneously high concentrations owing
to contamination of the samples. Since the mid1970s, sampling systems based on nonmetallic or
high-grade stainless-steel cables and all-plastic water
samplers designed to open below the surface of the
water and to then be closed on command at depth in
the ocean have become the norm, particularly for the
measurement of trace metals at nanomolar concentrations. In deep ocean environments requirements
for strength may demand the use of metal sampling
frames to support plastic sampling bottles and these
may be either of high-grade stainless steel or possibly
of a more expensive metal that is less likely to corrode, such as titanium. This has the additional
advantage that titanium is not usually an analyte
of great interest whereas iron is, so the possibility
of contamination from a titanium frame is of less
importance than from a stainless steel one.
Once the samples are returned to the sampling
platform it is necessary to minimize the risk of contamination from the atmosphere on the research
boat. While careful discharge of the samples into
sample storage bottles on deck is often satisfactory,
the ideal strategy is to carry out all sample handling
(at least for trace metals) in specially designed laboratories with positive pressure of filtered air to minimize the risk of contamination. The extent to which
these precautions are necessary varies depending on
the analyte of interest, its contamination potential,
and its ambient concentration. Furthermore, the procedures for one analyte may be incompatible with
another, and careful planning and preparation are
essential prerequisites for successful sampling. Some
marine waters are devoid of oxygen (e.g., deeper
parts of the Black Sea) and particular care is necessary in order to sample such waters without introducing oxidation artifacts. In such cases it is
usually necessary to conduct all sample processing
prior to sample stabilization under an inert (nitrogen) atmosphere (see Figure 1).
Sample Treatment and Storage
In deep ocean waters particulate matter concentrations are very small and it is usually unnecessary to
filter samples. However, in surface waters and coastal
areas, particulate matter concentrations are much
higher and filtration to remove particulate matter is
usually needed. This ideally serves four purposes:
(1) To remove living organisms whose subsequent
growth or death may compromise the sample
integrity.
(2) To remove particulate matter that may interfere
with the storage or subsequent analysis of the
sample.
Figure 1 Rossette sampling system containing niskin bottles
for water column sampling. (Photograph: Chris Lowe.)
(3) To allow a rigorous definition of solid and dissolved phases.
(4) To allow separate analysis of the particulate
phase to provide additional geochemical data for research and environmental monitoring.
Unfortunately, no simple filtration procedure can
unambiguously achieve all these results and it is
therefore normal practice to filter samples through
0.45 mm pore-size filters and define everything in the
filtrate as dissolved, although it is recognized that
this will include colloidal material. The role of colloids is an important area of current geochemical
research and the separate analysis of this phase is
therefore sometimes considered. Many analyses cannot be conducted at sea since they require complex
instrumentation, and storage is therefore necessary.
After filtration further measures to stabilize samples
for storage to avoid changes in concentrations as a
result of biological processes or adsorption/desorption processes on the sample container walls are
needed. As with sampling, careful planning and evaluation are necessary to ensure satisfactory storage,
since a suitable storage procedure for one analyte
may not be appropriate for another. There are a
WATER ANALYSIS / Seawater – Inorganic Compounds 285
number of strategies available to try to stabilize the
samples depending on the most likely storage problems. Thus, for metal analysis, adsorption to the
walls is of particular concern and samples are routinely acidified to pH –2, which serves to saturate
potential adsorption sites on the container and stabilize ions in solution. However, such acidification
will inevitably perturb the chemical speciation of the
ions if this is of interest. In the case of nutrient ions
(see later), biological processes are of primary concern and two strategies are routinely used: (1) deep
freezing the samples to slow all reactions and prevent
migration, (2) adding a poison such as mercury(II)
chloride to prevent biological activity. In some cases
a combination of these approaches is used. However,
storage of samples for nutrient analysis from surface
waters where concentrations are extremely low and
biological cycling is particularly intense is plagued
with difficulties and no universally accepted storage
procedure is available.
The last point to be noted under sample storage is
that it is essential that sample storage be done in
containers that have been rigorously precleaned to
avoid the leaching of ions from the walls contaminating the samples. This is particularly of concern for
trace metals and rigorous acid cleaning of sample
bottles is usually necessary. For most analytes, plastic
containers (e.g., polytetrafluoroethylene (PTFE),
low-density polyethylene (LPDE)) are preferred,
but, for mercury in particular, glass is preferred to
avoid the possible loss of volatile species.
Major Ions
Since the major ions are present in seawater at constant ratios to one another, it is normally not necessary to measure the concentrations of all the ions
since the concentration of one will allow the prediction of the others. Thus, chloride has traditionally
been measured using a silver nitrate titration, and
from this the salinity (i.e., total dissolved salt concentrations) can be derived. Now, however, conductivity is the routinely measured parameter and
this is converted to salinity by a relationship agreed
internationally with interlaboratory agreement ensured by the distribution of standard seawater samples for instrumental calibration. The use of modern
inductively coupled conductivity measurements with
careful temperature controls allows salinities to be
determined with accuracy and precisions of the order
of 70.01% or better.
If the measurement of individual major ions is required, the metals can readily be determined by
atomic absorption spectrometry (AAS) or inductively
coupled plasma-atomic emission spectrometry
(ICP-AES) after suitable dilution and with appropriate matrix matching and background correction. It is
possible to determine chloride and bromide by classic
silver nitrate titration and sulfate by barium chloride
precipitation, but the analytical method of choice
would now probably be ion chromatography with
careful control of eluent concentrations and instrument sensitivity to avoid the very large chloride peak
overlapping with the other anions of interest. Ion
chromatography can also be used to measure fluoride, iodate, and iodide, though electrochemical and
spectrophotometric techniques are more generally
used. Hydrogencarbonate (bicarbonate) is rarely determined exclusively; rather the alkalinity is measured traditionally by titration with acid to pH 4,
thus determining the sum of the bicarbonate, carbonate, and the small amounts of borate and phosphate present. The alkalinity of the surface ocean
and related components of the CO2–HCO3 –CO23 system in the ocean vary with space and time. Current concerns over the rate of carbon dioxide uptake
by the oceans as a factor in the greenhouse effect
have led to the development of extremely accurate
and precise measurements of the various components
of the carbon dioxide system.
Nutrients
Many of the ions in seawater are essential for the
growth of phytoplankton, the microscopic floating
photosynthetic algae that form the base of the marine
food web. However, many of these ions are present in
relatively high concentrations (e.g., CO23 , SO24 ,
K þ , Mg2 þ ) or in the case of some metals are required only in very small amounts. Thus, it has traditionally been accepted that only the elements
nitrogen, phosphorus, and silicon are required in
relatively large amounts and yet they are present
at rather low concentrations and hence may limit
the rates of phytoplankton growth in seawater.
This view is now being challenged and it may be
that some trace metals can also limit algal growth;
nevertheless, the traditional view of the importance
of these elements coupled with concern over eutrophication problems in coastal waters, arising from
excessive inputs of these elements, justifies a separate
treatment for them. Their biochemical roles are
rather different from one another, with nitrogen
and phosphorus being used for organic matter and
silicon being used for skeleton construction by
some species of algae, but all are generally called
nutrients.
Dissolved inorganic phosphorus (DIP) is present in
seawater as the various dissociation products of
286 WATER ANALYSIS / Seawater – Inorganic Compounds
phosphoric acid, and silicon is present mainly as the
undissociated silicic acid, though the analytical methods in routine use for these ions measure all the
inorganic forms of the elements. Nitrogen gas in
seawater is unavailable to most, but not all marine
algae, so the inorganic species of interest are nitrate
(the thermodynamically stable form under oxygenated conditions), nitrite, and ammonium. In addition
to the inorganic forms of these nutrients, organic
nitrogen and phosphorus species are known to occur
in seawater. The analyses of the individual organic
compounds are discussed elsewhere, but it is common practice in some laboratories to determine total
dissolved organic nitrogen and phosphorus by measuring the concentrations of DIP, nitrate, ammonium,
and nitrite before and after strong chemical or photochemical oxidation and considering the differences
between the two measurements to represent organic
phosphorus and nitrogen. The efficiency of these oxidation procedures has recently been evaluated and
there is now no doubt that there are significant levels
of dissolved organic nitrogen and phosphorus in surface water.
Colorimetric methods for the determination of
DIP, nitrate, nitrite, ammonium, and silicate are
well established, with both manual and automatic
procedures well understood and able to provide
adequate sensitivity for most purposes. These methods can readily be used at sea and in the future
probably in situ. International intercalibration exercises have shown that many laboratories now
have the analytical expertise to measure nutrient
concentrations at ambient levels, but this is not true
of all laboratories and the analysis still requires careful analytical procedures that recognize the importance of contamination control, blank correction,
and the complications arising from the saltwater
matrix. Although there have been a number of such
intercalibration studies, there is no widely available
standard reference material for nutrient analysis at
present.
In surface waters nutrient concentrations are
often depleted below the detection limits of the routine colorimetric methods even when using the
longest-pathlength spectrophotometer cells routinely
available (10 cm). The accurate measurement of
concentrations of these nutrients at nanomolar concentrations is now an important analytical goal. Therefore, in recent years, new methods for the analysis of
nitrate and ammonium with lower detection limits
have been developed based on chemiluminescence for
nitrate, fluorescence or concentration of the standard
colorimetric complex for ammonium, and preconcentration for DIP. Recently, the development of wave
guides has opened up the possibility of using cell
lengths of a meter or more which allow great improvements in the sensitivity of nutrient methods
using conventional colorimetric procedures.
Trace Metals
Over recent years the main analytical challenge in
inorganic marine chemistry has been the measurement of the trace metals, i.e., metals and metalloids
other than those major ions in seawater. The concentrations of trace metals are universally low
(10 9 mol l 1 or less) and their determination in a
seawater matrix represents a major challenge.
However, as noted earlier, it was the collection of
samples without contamination that prevented,
until recently, the generation of oceanic profiles of
trace metals that could be readily interpreted in terms
of well-understood oceanographic processes. Standard reference materials have now been prepared
to improve interlaboratory comparability, and a
number of international intercomparison exercises
have demonstrated good agreement between experienced laboratories. Furthermore, it has become clear
that in deep ocean waters, trace metal concentrations
show little short-term variation and show variation
in concentration with depth and between ocean basins that can be explained by well-understand
biogeochemical and oceanographic processes. This
allows repeat sampling at locations to be used as
a rigorous test of sampling and analytical procedures. Indeed, the International Oceanographic
Commission (IOC) has begun a process of establishing the baseline concentrations of some trace
metals in the major ocean basins of the world. Once
the extremely rigorous protocols necessary for such
sampling were put into force, it became possible
to focus on the chemical analysis of these low concentrations.
A wide variety of different methods of analysis
have been applied to different trace metals in seawater. All these documents are beyond the scope of
this article and the reader is referred to Further Reading. In general, the methods fall into two groups:
those that can be used without preconcentration and
those that do require such a procedure. In the first
group are spectrophotometric, chemiluminescence,
and fluorimetric procedures, electrochemical methods, and some ICP-AES and inductively coupled plasma mass spectrometry (ICP-MS) methods. In the latter
group, involving preconcentration, a variety of
concentration methods have been used followed by
AAS, gas chromatography, mass spectrometry, and
neutron activation methods, or indeed any of the
direct analysis procedures. These methods will now
be briefly discussed.
WATER ANALYSIS / Seawater – Inorganic Compounds 287
Techniques
Electrochemical Methods
Anodic stripping voltammetry has been widely used
as an analytical procedure because it has the sensitivity to measure a number of metals of interest
(zinc, cadmium, copper, and lead) directly in seawater.
Furthermore, the method can be sensitive to the
chemical speciation of the metal. Thus, if the metals
are present as strong and stable organic complexes,
as is now known to be the case, for example, for a
number of metals including copper, the labile
(weakly complexed) metal can be determined directly
and the total metal after suitable pretreatment.
Recent advances mean that stability constants can
also be determined for these strong complexes. The
instrumentation for these analyses is portable and
robust, thus allowing determinations to be made at
sea, minimizing storage artifacts. In the future in situ
electrochemical methods will become practical. The
applicability of electrochemical methods has been
limited to a few metals of appropriate reduction
potentials, but more recently techniques involving
cornplexation of a metal and the electroplating
of this complex using cathodic stripping voltammetry have extended the range of metals that can be
measured and the sensitivity of analysis for other
metals.
Spectrophotometry, Chemiluminescence, and
Fluorescence Methods
There are a number of colorimetric methods available for the measurement of trace metals in seawater,
though, in general, few have the sensitivity to measure the low ambient concentrations. However, in
some environments the ferrozine method for iron and
the formaldoxine method for manganese have been
used successfully. Recently, these methods have been
adapted to allow in situ measurements of iron and
manganese in hydrothermal plumes at mid-ocean
ridges.
Fluorimetry, in principle, offers improved sensitivity, but rather few methods have been developed
using this approach, with the notable exception of
the lumogallion method for aluminum, which has
been widely adopted with considerable success.
Chemiluminescence methods have also been described for some metals, most notably for iron, a
species of great current interest. Chemiluminescence
methods have now been used on remotely operated
vehicles operating in the deep sea. At ambient concentrations chemiluminescent measurement of iron
requires a preconcentration step which can be setup
inline for automatic operation.
Inductively Coupled Plasma Methods and
Electrothermal Atomic Absorption Spectrometry
A disadvantage of direct measurements of trace metals in seawater by atomic spectrometric methods is
the very large interferences arising from the major
ion matrix. The very high temperatures of plasma
systems can act to reduce these interferences and, for
barium at least, direct measurement of seawater concentrations by ICP-AES has been reported even at
open-ocean concentrations. ICP-AES lacks the sensitivity to measure most other trace metals directly at
oceanic concentrations, but may offer possibilities
for contaminated estuarine waters. ICP-MS offers
much greater sensitivity, though various interference
problems limit the range of metals to which this
technique can be applied. However, direct measurements of uranium and barium have now been reported using ICP-MS after dilution to minimize
matrix effects. The speed and multielement capability
of ICP-MS obviously offers real advantages coupled to
the possibility of measuring isotopic ratios. Against
these advantages must be set the disadvantages of cost,
complexity, and the fact that the systems cannot be
used at sea.
Direct measurements of several trace metals by electrothermal atomic absorption spectrometry (ETAAS)
have been reported. In general, sensitivities are inadequate for open-ocean waters, though in more
metal-enriched environments (e.g., coastal waters
and sediment pore waters) such analysis is possible;
careful corrections for the large and complex salt effects are necessary. The interferences can be minimized by the use of appropriate chemical modifiers,
platforms in the graphite tubes, and sophisticated
background correction schemes such as Zeeman.
Preconcentration Procedures
Probably the most widely used procedure for trace
metal analysis of seawater over the last 20 years has
been preconcentration followed by ETAAS because
of the wide availability, good sensitivity, and large
range of elements that can be measured by this
method. Preconcentration procedures have in general
been one of three types. First, co-precipitation, with
iron(III) ‘hydroxide’ or cobalt pyrrolidinedithiocarbamate, being the most widely used co-precipitants. Second, complexation followed by solvent
extraction with a number of different complexants,
of which dithiocarbamates, 8-quinolinol, and dithizone are particularly popular, and with extraction
into a range of solvents. The third approach is
extraction on to a chelating column (usually
Chelex-100 but recently also other complexants such
288 WATER ANALYSIS / Seawater – Inorganic Compounds
as ethylenediaminetetraacetic acid or 8-quinolinol
immobilized on a silica gel). These approaches all
effect a substantial concentration (10–1000–fold),
and separate the metals of interest from the bulk
matrix, allowing measurement by ETAAS with minimal interferences. The extraction methods are generally efficient, but extraction is pH dependent and
careful validation of a technique is always necessary
prior to its use. Most methods will extract several
metals. In some instances, the extraction techniques
can be used to estimate the speciation of metals in
seawater by analyzing samples directly without acidification and after acidification. The difference between the results of the two approaches yields a
metal fraction only available after acidification has
destroyed complexes. While ETAAS has proved a
popular method for analysis of these metals, other
techniques have been used for quantification including instrumental neutron activation, thermal ionization mass spectrometry, ICP-AES, and ICP-MS. The
mass spectrometric techniques offer the advantage of
measuring different isotopes of the metal, a property
that has been effectively exploited for lead. The ICP
techniques offer the option of simultaneous multielement analysis of a sample with real advantages in
rates of sample analysis. Measurement of iron in
seawater by isotope dilution ICP-MS with
co-precipitation preconcentration has recently been
reported in which the coprecipitant is magnesium
hydroxide from seawater itself, offering a simple,
low blank procedure.
For some metals including arsenic, selenium, and
tin, hydride-generation techniques coupled to atomic
absorption instrumentation offer sensitive methods
with minimum interference from seawater. Similarly
for mercury, cold vapor techniques, usually coupled
to gold amalgam as a preconcentration stage, offer
suitable sensitivity for measurements in seawater. For
all of these metalloids strong organic complexes can
be formed in seawater, of which methylmercury and
tributyltin complexes have received particular attention because of their high toxicity and tendency to
bioaccumulation. While these organic complexes can
be estimated by measurements before and after destruction of the organic complexes, such difference
techniques are of very limited application if the
organic complex forms only a small component of
the total element pool. Direct methods of measuring
both methylmercury and tributyltin have therefore
been developed based on selective volatilization and
detection of the organic species.
One last group of techniques that have been
developed for trace metals involves complexation
of the metal by compounds containing halogens,
with subsequent extraction and analysis of these
complexes by electron-capture gas chromatography.
The excellent sensitivity of this detection system
makes these methods suitable for determination of
several trace metals in seawater, limited only by the
availability of suitable complexing agents that are
element specific or can be separated out by chromatography. These methods can be made species
specific, for example, allowing selenium(IV) and (VI)
species to be analyzed separately. A further advantage is that gas chromatography is usually sufficiently
robust to be used at sea.
See also: Atomic Absorption Spectrometry: Electrothermal; Vapor Generation. Atomic Emission Spectrometry: Inductively Coupled Plasma. Chemiluminescence:
Liquid-Phase. Fluorescence: Quantitative Analysis. Ion
Exchange: Ion Chromatography Applications. Nitrogen.
Quality Assurance: Reference Materials. Sampling:
Theory; Practice. Spectrophotometry: Inorganic
Compounds. Voltammetry: Anodic Stripping; Cathodic
Stripping.
Further Reading
Berman SS, Sturgeon RE, Desaulniers JAH, and Mykyfluk
AP (1983) Preparation of the sea water references material, NASS-1. Marine Pollution Bulletin 14: 69–73.
Danielsson L-Q, Magnusson B, Westerlund S, and Zhang V
(1982) Trace metal determinations in estuarine waters by
electrothermal atomic absorption spectrometry after extraction of dithiocarbonate complexes into freon. Analytica Chimica Acta 144: 183–188.
Dehairs F, Neybergh H, and Hoenig M (1989) Direct
determination of dissolved barium in seawater by inductively coupled plasma atomic emission spectrometry.
Analytica Chimica Acta 222: 55–61.
Howard AG and Statham PJ (1993) Inorganic Trace Analysis, Philosophy and Practice. Chichester: Wiley.
Hydes DJ and Liss PS (1976) Fluorimetric method for
the determination of low concentrations of dissolved
aluminium in natural waters. Analyst 101: 922–931.
Jones RD (1991) An improved fluorescence method for the
determination of nanomolar concentrations of ammonium in natural waters. Limnology and Oceanography 36:
814–819.
Kirkwood D, Aminot A, and Perttila M (1990) ICES
(fourth) intercomparison exercise for nutrients in
seawater. Marine Chemistry Working Group. ICES
Cooperative Research Report No. 174. Copenhagen:
International Council for the Exploration of the Sea.
Matthias CL, Bellama JM, Olson GJ, and Brinckkman FE
(1986) Comprehensive method for the determination of
aquatic butyl tin and butylmethyl tin species at ultratrace
levels using simultaneous hybridization/extraction with
gas chromatography-flame photometric detection. Environmental Science and Technology 20: 609–615.
Measures CI, Grant B, Khadem M, Lee DS, and Edmond
JM (1984) Distribution of Be, Al, Se and Bi in the surface
WATER ANALYSIS / Industrial Effluents 289
waters of the western North Atlantic and Caribbean.
Earth and Planetary Science Letters 71: 1–12.
Obata H, Karatani H, and Nakayama E (1993) Automated
determination of iron in seawater by chelating resin concentration and chemiluminescence detection. Analytical
Chemistry 65: 1524–1528.
Okamura K, et al. (2001) Development of a deep-sea in
situ Mn analyser and application for hydrothermal
plume observations. Marine Chemistry 76: 17–26.
Parsons TR, Maita Y, and Lalli CM (1984) A Manual of
Chemical and Biological Methods for Seawater Analysis.
London: Pergamon.
Robinson C and Williams PJ, leB, (1991) Development and
assessment of an analytical system for the accurate and
continual measurements of total dissolved inorganic carbon. Marine Chemistry 34: 157–175.
Sharp JH, et al. (2002) A preliminary methods comparison
for measurements of dissolved organic nitrogen is seawater. Marine Chemistry 78: 171–184.
Sturgeon RE, Berman SS, Desaulniers JAH, et al. (1980)
Comparison of methods for the determination of trace
elements in seawater. Analytical Chemistry 52:
1585–1588.
van den Berg CMG (1989) Adsorptive cathodic stripping voltometry of trace elements. Analyst 114: 1527–
1530.
Vink S, Boyle EA, Measures CI, and Yuan J (2000) Automated high resolution determination of the trace elements iron and aluminium in the surface ocean using
a towed Fish coupled to flow injection analysis. Deep-Sea
Research I 47: 1141–1156.
Wu JF, Sunda W, Boyle EA, and Karl DM (2000) Phosphate
depletion in the western North Atlantic Ocean. Science
289: 759–762.
Zhang JZ and Chi J (2002) Automated analysis of nanomolar concentrations of phosphate in natural waters
with liquid waveguide. Environmental Science and Technology 36: 1048–1053.
Industrial Effluents
R Guerra, University of Bologna, Ravenna, Italy
& 2005, Elsevier Ltd. All Rights Reserved.
Introduction
Industrial effluents result from various types of industrial processes and disposal practices, and may
contain pollutants at levels that could affect the
quality of receiving waters, as well as the aquatic
ecosystem (Table 1). The emission of industrial pollutants in liquid effluents has to comply with
stringent regulatory requirements and guidelines, in
which chemicals listed should not exceed a given
concentration. On the other hand, a chemical company
may release a large number of different chemicals,
which are not considered by regulatory requirements
Table 1 General types of water pollutants
Class of pollutant
Significance
Heavy metals
Organically bound metals and
metalloids
Inorganic species
Health, toxicity, aquatic biota
Toxicity, aquatic biota
Trace organic pollutants
Polychlorinated biphenyls
Pesticides
Detergents
Chemical carcinogens
Water quality, toxicity, aquatic
biota
Toxicity
Toxicity, aquatic biota, wildlife
Toxicity, aquatic biota, wildlife
Toxicity, aquatic biota
Incidence of cancer
and in many cases are unknown. These compounds
may be the final products, precursors, or intermediates of the process, or impurities and by-products.
One of the distinguishing characteristics of effluents
of industrial origin, as compared to municipal wastewaters, is that often they may contain a mixture of
different and very toxic substances. Approved
analytical methods exist for compliance monitoring
of conventional pollutants in industrial effluents;
however, because of the complexity of the sample
matrix, several analytical methods are required to
determine polar and nonpolar organic compounds
and new emerging pollutants that may impact water
quality. As a consequence, modifications in instrumentation, sampling, and sample preparation techniques have become essential to comply with the
regulatory water standards, as well as to achieve a
faster speed of analysis.
General Chemical Analysis of
Industrial Effluents
This section provides a brief overview of some of the
most important tests that are performed on wastewaters.
pH, Hardness, Alkalinity, and Conductivity
General measures of the ionic characteristics of water
are pH, hardness, alkalinity, and conductivity. There
are several others that could be added to this group,
such as redox potential and salinity; however, these