Krzysztof KORZENIEWSKI THE PROBLEM OF THE THREAT TO

Krzysztof KORZENIEW SKI
U niversity of Education in Słupsk
THE PROBLEM OF THE THREAT TO THE MARINE
ENVIRONM ENT FROM H EAVY M ETALS
C o n t e n t s : 1. Introduction, 2. Mercury, 3. Lead, 4. Copper, 5. Zinc, 6. Cadmium;
Streszczenie; R eferences
1. INTRO DUC TIO N
The th rea t to th e n atu ral environm ent, including th a t of th e sea, byheavy m etals provides one of the most difficult and urg en t sozological
problem s of p resent day society. The long delay betw een stim ulation
of the environm ent w ith an atom or ion of a m etal and th e response in
the ecosystem hinders the assessm ent of cause and effect and to u n d er­
take preventive m easures to protect the ecosystem.
About one-third of the ninety elem ents occurring on the E arth have
been found to be essential for the grow th and developm ent of bacteria,
plants and animals. Some of the elem ents occur and are consumed in
large quantities as nutrients, w hile other, so-called trace elem ents, can
be detected only by highly sensitive analytical procedures. We cannot
be quite sure th a t certain organisms do not req u ire m inute am ounts
of other elem ents h ith erto considered as unnecessary.
Some of th e trace elem ents m ay become toxic w hen th eir levels
become higher th an th e metabolic and physiological requirem ents. On the
other hand, m any plants and anim als can tolerate excessive physiologi­
cal levels of trace m etals and by th eir accum ulation they provide a se­
rious th re a t to higher links in th e trophic chain.
At present, heavy m etals are considered as stim ulants or re ta r­
dants of vital processes, depending on th eir concentration, oxidation
states and form s of occurrence. A part from a straightforw ard action,
heavy m etals m ay accum ulate in different organs of anim als in th e form
of compounds tem porarily innoxious, from which th ey can pass to the
Oceanologia nr 13(1980)
blood stream owing to rapid metabolic transform ations, and to poison the
whole organism.
The pollution of surface w aters and soil w ith heavy m etals is in ­
creasing and provides a serious problem , even in our country, p articu ­
larly in the vicinity of industrial regions.
The paper presents th e effect of heavy m etals on the m arine eco­
system, m arine fauna and hum an health.
2. M ERCURY
M ercury occurs in the environm ent highly dispersed in the upper layers
of the ea rth ’s crust as HgS, its content am ounting on average to 50 ng/g.
The upper layer of the soil contains 50 to 510 ng/g and this level may
rise locally up to 1000 ng/g due to the use of organom ercurials in agri­
cu ltu ral operations. Table 1 lists the contents of m ercury in th e envi­
ronm ent after various authors.
Table 1. Mercury levels in the natural environm ent after various authors
Tab. 1. Zawartość rtęci w środowisku przyrodniczym w edług różnych autorów
Environm ent
Środowisko
V olcanic em issions
W yziew y w ulkaniczne
Earth’s crust
Skorupa ziem ska
Soil (Europe)
Gleba (Europa)
Atm osphere — Atm osfera
P recipitation — Opady
Concentration
Stężenie
uip to 20 000 ng/m s
R eference
Literatura
34
50— 100ng/g
14, 21, 27
50—510 ng/g
21
0,1—20 ng/m*
5—120 ng/dm 1
9
Arctic glacier
Lodow iec arktyczny
30—70 ng/dm 5
V, 14
33, 34
Spring w ater
Woda źródlana
10—50 ng/dm 3
14
Inland w aters
Wody śródlądow e
Sea waiters
Wody m orskie
Ocean
Deeip oceanic w aters
G łębokie wody oceaniczne
M inam ata Bay
Zatoka M inam ata
10—500 ng/drnJ
8
10—30 ng/dm s
15
3—30 ng/dm s
8, 11, 15
15
3—5 ng/dm*
1600—3600 ng/dm»
10, 17
In the aqueous environm ent both th e m etallic m ercury and its com­
pounds undergo various chem ical and biological transform ations illu stra­
ted by the following scheme:
C ,H 5H g+
¿V
A r H g ----- > H ga+
CH 2H g+
(CH3)2Hg
tiv
C H sO(CH2)Hg
The m ethylation reaction (I) occurs in bottom sedim ents owing to
the activity of the C lostridium bacteria (particularly Cl. cochlearium ) and
to processes prom oted by aerobic m ethanogenic fungi (e.g. N eurospora
crassa) and bacteria belonging to th e genus Pseudom onas [13].
M icroorganisms, in p articu lar bacteria, participate in the following
transform ations:
(i) reduction of phenyl-, eth y l- and m ethylm ercury to elem ental
m ercury;
(ii) aerobic conversion of phenylm ercury acetate (PMA) to diphenylm ercury and elem ental m ercury;
(iii) reduction of the Hg2+ ion to m ercury (Pseudomonas, Enterobacteriaceae, Staphylococcus aureus).
In an acidic medium, m ethylm ercury rem ains in w ater, w hereas in
a w eakly basic m edium it is converted to d im ethyhnercury (II).
Both m ethylm ercury and dim ethylm ercury are easily assim ilable
by low er aquatic anim als providing the first links of the trophic chain.
U nder specific conditions of the m arine environm ent, ph en y lm er­
cury [111], alkoxym ethylm ercury [IV] and alkylm ercury [V] can be con­
verted to an inorganic form of m ercury. U nder anaerobic conditions the
m ercuric ion may react w ith hydrogen sulphide deposited on the bottom
to form sparingly soluble HgS.
It is w orth noting th a t transform ations of m any more complex m er­
cury compounds in the m arine environm ent have not been described so
far.
The level of m ercury in predatory fish is usually by 3 — 4 orders of
m agnitude higher than in the surrounding sea w ater [ l l . The relation
betw een the m ercury level in fish and in the surrounding w ater can be
calculated from the following em pirical equation
[11]:
y — 0.031x — 0.179
w here x is the m ercury level in w ater in ng d m '3 and y is the m ercury
level in fish tissue in ppm of w et weight.
Ingestion in branchial anim als occurs m ainly directly from th e sea
w ater through the body surface and gills. It m ay also occur through the
alim entary tract. Almost 100 per cent of m ercury in fish and some other
branchial anim als occurs as m ethylm ercury, a lower percentage being
found in some molluscs.
M ethylm ercury is accum ulated m ostly in the m uscles of fish and
the half period of excretion am ounts on average to about 2 years depen­
ding on the species [28].
The cum ulation factor for th e system fish •— fish-eating birds
am ounts to about 10. In th e Baltic Sea area, the critical organisms con­
stitu te birds, sea m am m als and m an who assim ilate all the m ercury from
food. In hum ans, about 15 per cent of cationic (Hg2+) m ercury ingested
w ith food is assim ilated and as m uch as 94 per cent of m ethylm ercury,
CH3H g+ [22], The half-period of excretion of Hg2+ and CH3Hg+ in man is
42 ± 3 days and 76 ± 3 days respectively.
The potential th re a t from environm ental pollution w ith m ercury
compounds can be estim ated from the following expression [8]:
1 = 0.1 - i .
C
w here I is the im pact index, Pff is th e overall production of m ercury and
c is its concentration in the environm ent.
A m ore accurate estim ate can be obtained by using the index of
local impact, I£•
P l
So
I = I—
— ——
L
Pa
S
w here I is the im pact index from the preceding equation, P, an d P g are
the local and overall annual production of m ercury respectively, S G and
S L are the total and local area of a p articu lar region respectively.
According to FAQ data, th e annual production of m ercury in the
w orld am ounts to approx. 9 000 tons. A bout 5 000 tons of this reaches the
seas and oceans. It is estim ated th a t th e w aters of th e W orld Ocean have
accum ulated 136 million tons of m ercury and th e atm osphere surrounding
the Globe, to w hich it is em itted during the burning of coal, about
22,700 tons [5].
The main sources of pollution of the atm osphere are th e paper in­
du stry in which m ercury compounds are used for preservation of the
groundwood and wood pulp, th e plastics industry w here the compounds
are used as catalysts, chlor-alkali production using m ercury electrodes
und agriculture w here m ercury fungicides are used.
In Poland, of th e 335 tons of m ercury consumed annually by the
national economy, 140 tons find th eir w ay to the environm ent, i.e. 42 per
cent. A bout 25 tons, i.e. 7 p er cent [4], are utilized in the production of
pesticides.
A fter Somer [31], about 4 ton of m ercury is discharged annually w ith
m unicipal sewage to th e Baltic Sea and about 20 tons w ith industrial
effluents (Table 2). Rivers supply about 6 tons and th e atm osphere about
4 tons annually. Of th e to tal am ount of about 34 to n s /y r. as m uch as
29 to n s/y r. is deposited in coastal regions and about 3 to n s/y r. leaves
the Baltic through th e straits. As a result, com paratively low elevels of
m ercury (7—9 ng dm-3) are observed in the open-sea w aters, com parable
w ith those noted in the distant A tlantic w aters [26],
Polish studies on m ercury levels in fish [2, 20, 24], taken in southern
regions of the Baltic Sea and in the P om eranian and G dańsk Bays,
showed them to range betw een 0.10 and 0.15 mg k g '1.
To protect m an — the fish consum er — several governm ents of
Baltic states issued a ban on the sale of fish containing m ore th an
1 mg Hg per kg w et mass. This applies especially to fish taken in Oresund,
the Gavle region, the G ulf of Bothnia and in the coastal regions of th e
G ulf of Finland [23],
3. L EA D
A t the beginning of 1970 the global output of lead am ounted
to approx. 4 milion tons, 40 per cent of this am ount being con­
sumed in th e production of batteries and various oxides, and 25 per
cent in the production of cables and pipelines. Of th e m ore
im portant lead compounds, P b C 0 3 was used as a com ponent of a w hite
pigm ent, P b C r0 4 as a yellow pigm ent, P b30 4 as the protective pigm ent,
so-called minium, Ca2P b 0 4 as a corrosion inhibitor for iron and steel,
P b (S i0 3)2 for dyeing earthenw are, (C2H 5)4Pb and (CH3)4Pb as fuel ad­
ditives increasing th e octane num ber.
Lead used by m an has been dispersed in the environm ent in various
forms over the ages, and is now adays considered to be th e main pollu­
tant. Its high toxicity and continuous cum ulation in higher organism s
has lead to its critical level in th e hum an organism.
The lead content of th e atm osphere varies substantially from 0.0002
to 71 |xg m '3, th e la tte r value being recorded during th e peak traffic
period in Los Angeles. A tm ospheric lead is produced m ostly by com­
bustion of fuel containing alkyl lead compounds [13]. The concentration
of lead in A m erican gasoline am ounts to 2.6 g per US gallon ( = 3.785
litre) on average.
U npolluted A ntarctic soil contained sm all quantities of lead ave­
raging 10 ppm. This value has been assumed to be th e n atu ral level of
the elem ent in th e soil. In urb an and industrialized regions the level of
lead in the soil is alm ost ten tim es higher, particu larly along roads and
highways.
N atural sources of lead contam inate w ater reservoirs to a sm all
extent only, owing to th e poor solubility of the elem ent and form ation
of deposits. In clean reservoirs of surface w aters th e m ean level of lead
was 0.5 ug dm '3, w hereas in distant ocean w aters it was less than
0.1 [ig dm '3. During the past 50 years, however, the level of lead in the
W orld Ocean increased rapidly. Ice sam ples taken in G reenland revealed
an increase in the level of lead from 0.0005 to m ore than 0.2 ¡.»g k g '1
from 800 B.C. to 1965 [3].
The toxic effect of lead on m icroorganisms can be explained in term s
of displacing essential elem ents such as Mg, Fe and Mn from the -SH,
-NH2 and = N H groups of enzym es by the P b 2+ ions. However, no u n ­
tow ard effect of lead has been noted on plants. M any species of plants
tolerate high levels of lead in th e soil and tend to tran sp o rt it from
the surface to deeper layers of soil by means of the root system. Grass
has been reported to grow w ell over a lead mine area w here the level of
lead in the tissue ranged from 200 to 9 645 ppm [13], P articu larly insi­
stent to lead w ere Plantago lanceolata, Agrostis stalonifera and Festuca
rubra.
The ability of plants to accum ulate lead has been used to retrieve
its levels in the past. In p articular periods th e following levels of lead
w ere found in the veins of a tree growing 50 m off a m oderately crowded
street:
1865—1879
1900— 1912
1940— 1947
1956— 1959
1960
0.16
0.12
0.33
0.74
3.90
ppm
ppm
ppm
ppm
ppm
Pb
Pb
Pb
Pb
Pb
All analyses w ere perform ed using the same technique sim ultaneously.
If one assumes th a t lead was adsorbed in the annual grow th rings of
a tree, an alarm ing and dram atic factor of environm ental pollution w ithin
the past 100 years is provided.
Animals take in lead w ith w ater and food (and accum ulate approx.
10 per cent of th a t amount), also breething it in w ith air (and accum ulate
approx. 50 per cent of th a t amount). Inorganic form s of lead (Pb2+) pro­
vide the main poison of metabolic processes and accum ulate in e ry th ro ­
cytes, the liver and kidneys. It inhibits the enzym atic activity of dehy­
drogenase of 5-aminolevulinic acid (ALA) which is essential for produ­
cing hem s — dyes form ing haem oglobin w ith proteins in the bone m ar­
row. Children are m ore sensitive to lead poisoning than adults, toxic
blood levels of lead am ounting to 0.25 and 0.8 pig d m '3, respectively.
An estim ate of the balance of lead in the Baltic Sea w aters is shown
in Table 2. The following conclusions can be draw n from these data: (i)
the atm osphere provides the main source of lead in w ater; (ii) the r e ­
moval of lead by sedim entation provides a very effective process both
in the coastal zone and in the open sea; (iii) the total content of lead in
w ater is low.
Sea water — woda
morska,
small
ton/yr — t/rok
Total
tons
— Ton
razem
małe
140
7 x 10-5
29
2
ton/yr — ton/rok
iton/yr — t/rok
7 x 10-3
3 (netto)
0.5
4
' 1 5 x l0 - 3
6
20?
20 x 10~3
4
0.2
ton/ikm3
ton/yr — t/rok
conc. ¡j.g/g
stęż. |j,g/g
g/person/yr
g/osoba/rok
ton/yr — t/rok
ton /k m 3
ton/yr — t/rck
ton/yr — t/rok
ton/k m 5
ton/yr — t/rck
ton/k m 5
ton/yr — t/rok
conc. in u.g/1 = ton/km-s
stężenie w ¡xg/ł = t /k m 3
0.1 mm/rak 40°/» suchej masy,
gęstość 2,5 g/cm 3
Sedimentation in the coastal zone
Sedymetnacja w strefie przybrzeżnej
Fish catches — Połowy ryb
in the open sea
w morzu otwartym
40 per cent dry
2.5 g/cm3)
— Odpływ
Sedimentation
Sedymentacja
(o. 1 mm/yr of
matter, density
Outflow
Przemysł — Industry
Atmosphere — Atmosfera
Sedimentation — Osadzanie się
Inflow — Napływ
Rivers — Rzeki
Municipal pollution
Zanieczyszczenia komunalne
103
?
?
103 +
industry
przemysł
103—10*
?
10 — 100
?
200
?
103
?
?
103—104
?
?
10
Table 2. Concentration and material balance of heavy metals in the Baltic Sea (after ICES
Tab. 2. Koncentracja i bilans metali ciężkich w Morzu Bałtyckim (wg ICES 1977)
i
Pb
Hg
10*
5
?
?
2000
5
2000
40
200
10
4000
?
3
600
?
?
10
Cu
1977)
2 x 105
10
?
?
5000
10
4000
120
1000
10
4000
?
20
4000
?
?
60
Zn
i
1
— Zrzuly
Discharges
t
Removal
- U suw anie
Load
It is likely th a t lead does not accum ulate from food to any noti­
ceable extent. W hile its level in M ytilus edulis, w hich feeds on suspen­
ded m atter is low, Macoma baltica, w hich feeds on deposited m atter con­
tains higher levels of lead. In seals the lead content is low [3],
4. CO PPER
The main sources of copper penetration to the environm ent are the m i­
ning industry and m etallurgy. As a m atter of fact, a deficiency of copper
in the environm ent m ay provide a lim iting factor in the production of
biomass, how ever an increased level inhibits p rim ary production.
An im portant featu re of copper is its capacity to form very stable
complex compounds w ith com plexing and chelating n atu ra l compounds
present in sea w ater. The copper complexes are m any tim es more stable
than those form ed by other m etals [6],
A high accum ulation factor of copper has been found in phytoplank­
ton and in m acrophytes. P articu larly high copper levels w ere found in
the crustaceans M esidothea entom on caught in the G ulf of Bothnia and
in the G ulf of Finland [16], w here th ey provide an im portant component
in food for seals. No reports have as yet been subm itted on the copper
levels in seal meat.
The copper level in fish- is fairly low, th a t in th e liver being about
30 tim es as high as in the m uscular tissue. The copper level in the liver
of eel caught in copper-polluted areas was about 40 mg k g '1 w et mass,
w hereas in unpolluted areas the level was half of this [35].
In aquarium experim ents w ith fresh w ater, sm all quantities of cop­
p er (30—60 fig d m '3) w ere associated w ith the initiation of a lethal a t­
tack of a virus disease evoked by Vibrio anguillarum in eel.
D espite of the fact th a t th e balance of copper in the Baltic Sea is
far from com plete (Table 2), the level of the m etal in this basin can be
estim ated as being high.
5. ZINC
The main industrial sources of environm ental pollution w ith zinc are the
nonferrous mining industry, m etal refining works and electroplating
works. Zinc is much m ore volatile than copper, hence its higher con­
centration in th e atm osphere (Table 2). In m unicipal sewage the m ajor
p a rt of zinc is released from zinc-plated pipelines and objects made from
zinc-plated m etal sheets.
Zinc has been found to be m arkedly accum ulated by phytoplankton.
Fish from coastal regions have higher levels of zinc than those from the
open sea (contrary to copper) [16]. It is estim ated th a t half the total zinc
in the Baltic Sea (Table 2) is from the atm osphere, the rest being from
m unicipal and industrial sewage.j
6. CADM IUM
Cadm ium has a high lethal toxicity. The highest admissible level (NDS
according to the G overnm ent R egulations and Legal G azette of the
Polish People’s Republic, No. 13, 1976) for an 8-hour w orking post is 0.1
mg per dm 3 of air. L ethal intoxication in man at .a cadm ium concentra­
tion in air of 10 mg per dm 3 occur after 5 hours [25, 29].
In 1946, D r Hagino of Japan discovered and described an unknow n
disease and called it „itai-itai” . It was first noted in 1920 in Fuchu, Toya­
ma region, b u t it spread particu larly after W orld W ar II causing h u n ­
dreds of deaths. Autopsy revealed high cadm ium levels in th e corpses.
The direct cause of th e poisoning was the Kam ioka mine which dischar­
ged considerable am ounts of Cu, Pb, Zn and Cd to the Jinzu river. The
w ater from the riv er was used for drinking by the population and for
irrigation of th e rice fields. As late as 1968 over 100 people in this region
w ere still ill.
N um erous fatal cases of cadm ium poisoning w ere recorded in the
U.S.A. and in Europe (in France 300 persons died in 1948 after drinking
wine stored in cadm ium vessels), which resulted in the WHO u n d erta­
king of com plex studies on th e m etabolism of cadm ium and on its con­
te n t in the biosphere, in 1973— 1977. Cadm ium was found to be absent
in children, but in 45-year-old adults the total am ount was 30—40 mg,
i.e. the m ean annual accum ulation am ounts to 0.67— 1.3 mg (= 1 .8 — 3.6 ng
per 24 hrs.) [18].
Cadm ium and its compounds are used in electroplating, th e produc­
tion of low -m elting alloys, stable enam el pigm ents, alkaline accum ula­
tors, plastics, as w ell as in nuclear reactor, rad ar and television techno­
logy.
The global production of cadm ium in 1970 am ounted to 15000 tons
and increased at a rate of 14 per cent annually. Since cadm ium -rich
m inerals (grenokite, CdS, containing 77.6 per cent Cd and otavite C dC 03,
containing 61.5 per cent Cd) are m eagrely distributed, th e main source
of cadm ium is provided by zinc ores containing 0.01— 0.5 per cent Cd.
Zinc sm elting w orks in Poland, together w ith those in the U.S.A. are
the biggest suppliers of cadm ium and, at th e same time, they are the
biggest producers of cadm ium -containing effluents [12].
The concentration of cadm ium in the air over th e A tlantic Ocean is
very low, ranging from 0.03 to 0.62 ng m '3. O ver uncultivated regions the
concentration ranges from 0.001 to 0.005 fig m"3, and over Polish tow ns it
2 — O ceanologia
ranged from 0.002 ¡xg m '3 in Gdańsk, to 0.051 fig n r 3 in Katowice, in 196rr
[19]. In m any countries concentrations as high as 0.6 |xg m '3 w ere found in
the air around industrial plants.
In Sweden th e degree of contam ination of atm ospheric air w ith cad­
m ium was determ ined indirectly by assaying the Cd content in the
mass of Hylocomium splendens. By using this m ethod it was found th at
in southern Scandinavia th e cadm ium content exceeded 1 ¡xg/g d ry m at­
ter, w hereas in th e n o rth it did not reach 0.1 jxg/g dry m atter [32],
A comparison of th e cadm ium levels w ith those found in specimens sto­
red in herbaria revealed a tw o-fold increase in the cadm ium concentra­
tion in the air over the past 50 years.
In soil the C d /Z n ratio oscillates betw een 1:500 and 1:5000, w hereas
in sea w ater it am ounts to 1:168 [19].
The cadm ium level of the sea w ater is approx. 0.1 ng d m '3, but
in unpolluted inland w aters it reaches 1 ¡xg d m '3. In highly populated in­
dustrialized countries the cadm ium level in rivers and lakes increases up
to 10 |xg dm '3.
In the distant Baltic Sea w aters the cadm ium level is 0.1—0.5 ¡xg dm"3,
but in the region of discharge of sewage into th e G ulf of Bothnia it jum ps
up to 10.2 (xg d m '3 [18, 30],
The polluted air and w ater contributed to an increase in th e cad­
m ium levels in soil, which ranges w idely from 1 mg k g '1 on u ninhabit­
ed barren land to 100 mg k g '1 in industrialized regions.
K rzysztof KORZENIEWSKI
Wyższa Szkoła Pedagogiczna w Słupsku
PRO BLEM ZA G R O ŻE N IA ŚR O D O W ISK A M ORSKIEGO
M ETALAM I CIĘŻKIM I
Streszczenie
Przedstawiono źródła, drogi przenikania, w pływ i efek ty działania m etali ciężkich
na ekosystem m orski, na żyw e zasoby morza i zdrowie człow ieka. Zebrano najnow ­
sze dane dotyczące przenikania rtęci, ołowiu, m iedzi, cynku i kadmu do powietrza,
wód powierzchniowych i gleby, na tle ich produkcji w P olsce i na św iecie.
Wykazano, że długi okres, jaki upływ a od wprow adzenia do środowiska pierw iaska m etalicznego do uzyskania odpowiedzi ekosystem u, utrudnia ustalenie zależ­
ności przyczynow o-skutkow ej i ochronę ekosystem u.
Podano w ażniejsze chem iczne i biologiczne przekształcenia pierw iastków m e­
talicznych oraz ich organicznych i nieorganicznych połączeń na różnych poziomach
troficznych w środowisku morskim .
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Rev., 1970, 8, p. 203.
2. C h o d y n i e c k i A., P r o t a s o w i c k i M.. O c i e p c A.„ J u r a n J., Bada­
nia nad stopn iem zanieczyszczenia rtęcią ry b Z atoki P om orskiej i Dolnej Odry,
Studia i Mat Oceanol. KBM PA N, 1976, 15 p. 31
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m istry in Britain, 1971, 7, p. 54.
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