96
Marine Sediments
Rickely and Kittrick [282] used sequential extraction to investigate the chemical
partitioning of cadmium, copper, nickel, and zinc in marine sediments.
Belhomme et al. [274] have carried out a comparative study of methods for digesting a number of metals in marine sediments prior to their determination. The
metals were those usually found in sediments - aluminium, iron, manganese, titanium, and some which occur less frequently and at very low concentrations - zinc,
copper, lead, cadmium, chromium, and arsenic. The analytical methods used were
visible spectrometry for aluminium and titanium, flame atomic absorption spectrometry for iron, manganese, and zinc and the graphite furnace for the other metals.
Digestion techniques investigated were acid digestion in hydrochloric, nitric, hydrofluoric and perchloric acids, and a dry technique involving calcining the sediments
and taking up the ashes in nitric acid. The results show that the selection of a
particular digestion technique is dependent on the particular metal to be analysed, but
it is indicated, in general terms, that the simplest, most rapid, most free from contamination and most effective is digestion with nitric acid, in a bomb, at 150°C.
Microwave digestion techniques have also been used in the sequential extraction of
calcium, iron, chromium, manganese, lead, and zinc in sediments [275]. The extraction rates of metals in each of the five binding fractions of marine sediments (metal
exchangeable, carbonate bound, iron-manganese oxide bound, organic bound, and
residual) were determined for both conventional and microwave heating techniques.
Microwave digested sediment samples (20 ml) were centrifuged at 10000 rpm for
30 min. Metals were determined by flame atomic absorption spectrometry. To prepare material for the determination of extraction rates for one particular fraction, a
quantity of material was taken through the conventional sequence of steps up to the
fraction for which the rate was determined. Sequential microwave extraction procedures were then established from the results of the rate experiments. Recoveries of
total metals from standard sediment samples were comparable for both conventional
and microwave techniques except for iron (62 % by microwave and 76 % by conventional method).
Inductively Coupled Plasma Atomic Emission Spectrometry. McLaren et al. [276]
have described a procedure which permits the simultaneous determination of six
major and minor elements (aluminium, iron, calcium, magnesium, sodium, and
phosphorus) and eight trace elements (beryllium, cobalt, copper, manganese, nickel,
lead, vanadium, and zinc) in near shore marine sediments by inductively coupled
plasma atomic emission spectrometry. Dissolution of the samples is achieved with a
mixture of nitric, perchloric, and hydrofluoric acids in sealed Teflon vessels. Accurate
calibration for all elements can be achieved with simple aqueous standards, provided
that proper correction for various spectroscopic interferences is made. The method
was not suitable for determination of arsenic, cadmium, and molybdenum in these
materials because of inadequate sensitivity nor for chromium and thallium because of
incomplete dissolution. Detection limits varied from 0.5 mg kg-l (beryllium) to 5 mg
kg-l (arsenic).
Sediment samples (0.5 g) were placed in Teflon pressure decomposition vessels and
to each were added 3 ml of concentrated nitric acid, 1 ml of concentrated perchloric
acid, and 3 ml of concentrated hydrofluoric acid. The sealed vessels were completely
Marine Sediments
Rickely and Kittrick [282] used sequential extraction to investigate the chemical
partitioning of cadmium, copper, nickel, and zinc in marine sediments.
Belhomme et al. [274] have carried out a comparative study of methods for digesting a number of metals in marine sediments prior to their determination. The
metals were those usually found in sediments - aluminium, iron, manganese, titanium, and some which occur less frequently and at very low concentrations - zinc,
copper, lead, cadmium, chromium, and arsenic. The analytical methods used were
visible spectrometry for aluminium and titanium, flame atomic absorption spectrometry for iron, manganese, and zinc and the graphite furnace for the other metals.
Digestion techniques investigated were acid digestion in hydrochloric, nitric, hydrofluoric and perchloric acids, and a dry technique involving calcining the sediments
and taking up the ashes in nitric acid. The results show that the selection of a
particular digestion technique is dependent on the particular metal to be analysed, but
it is indicated, in general terms, that the simplest, most rapid, most free from contamination and most effective is digestion with nitric acid, in a bomb, at 150°C.
Microwave digestion techniques have also been used in the sequential extraction of
calcium, iron, chromium, manganese, lead, and zinc in sediments [275]. The extraction rates of metals in each of the five binding fractions of marine sediments (metal
exchangeable, carbonate bound, iron-manganese oxide bound, organic bound, and
residual) were determined for both conventional and microwave heating techniques.
Microwave digested sediment samples (20 ml) were centrifuged at 10000 rpm for
30 min. Metals were determined by flame atomic absorption spectrometry. To prepare material for the determination of extraction rates for one particular fraction, a
quantity of material was taken through the conventional sequence of steps up to the
fraction for which the rate was determined. Sequential microwave extraction procedures were then established from the results of the rate experiments. Recoveries of
total metals from standard sediment samples were comparable for both conventional
and microwave techniques except for iron (62 % by microwave and 76 % by conventional method).
Inductively Coupled Plasma Atomic Emission Spectrometry. McLaren et al. [276]
have described a procedure which permits the simultaneous determination of six
major and minor elements (aluminium, iron, calcium, magnesium, sodium, and
phosphorus) and eight trace elements (beryllium, cobalt, copper, manganese, nickel,
lead, vanadium, and zinc) in near shore marine sediments by inductively coupled
plasma atomic emission spectrometry. Dissolution of the samples is achieved with a
mixture of nitric, perchloric, and hydrofluoric acids in sealed Teflon vessels. Accurate
calibration for all elements can be achieved with simple aqueous standards, provided
that proper correction for various spectroscopic interferences is made. The method
was not suitable for determination of arsenic, cadmium, and molybdenum in these
materials because of inadequate sensitivity nor for chromium and thallium because of
incomplete dissolution. Detection limits varied from 0.5 mg kg-l (beryllium) to 5 mg
kg-l (arsenic).
Sediment samples (0.5 g) were placed in Teflon pressure decomposition vessels and
to each were added 3 ml of concentrated nitric acid, 1 ml of concentrated perchloric
acid, and 3 ml of concentrated hydrofluoric acid. The sealed vessels were completely