Cd In Surface Waters Research Articles

Microcystis-dominated paddy crusts enhancing the cadmium accumulation in rice plant (Oryza sativa L.)

Paddy crusts (PCs) influence seriously on the heavy metal migration and transformation in the paddy field system. However, their quantitative effect on heavy metal accumulation in rice plant has been rarely reported. In this study, the influence of microcystis-dominated PCs on Cd content and physicochemical properties of the surface soil, water and rice plants (Oryza sativa L.) during PCs' overall life cycle was investigated. During the PC growth period (0–15 d), the Cd content in the surface soil (0–10 cm) and water decreased by 10–20% due to the accumulation effect. However, during the perish period (15–35 d), the Cd content in the surface soil and water increased by 20–30%, as Cd stored in the PCs was re-released. Moreover, the decomposition of PCs produced a large amount of low-molecular-weight organic substances (<500 Da), significantly increasing the bioavailable acid-soluble Cd in the surface soil. Finally, the PCs increase 25–80% and 60–85% Cd content in rice root and shoot, respectively. A structural equation model demonstrated that the contribution to the Cd in rice roots in the sequence: Cd in surface water > PC > surface soil. Potted experiments using sandy, clay, sandy loam soil containing 0.8–3.5 mg/kg of Cd collected from six provinces’ paddy field in southern China confirmed that PCs increased the Cd accumulation in rice plants by as much as 25–80%. Consequently, the presence of PCs can enhance the Cd concentration in rice plants, and the removing PCs could be a potential effectively approach to reducing Cd content in rice plants.

Environmental Radioactivity, Ecotoxicology (238U, 232Th and 40K) and Potentially Toxic Elements in Water and Sediments from North Africa Dams

The natural radioactivity of 238U, 232Th and 40K was measured in water and sediment samples collected from Sidi Salem dam (Tunisia) and Aïn Dalia dam (Algeria) in the Tuniso-Algerian transboundary basin. The samples were measured using a TERRA detector of gamma, beta, and alpha rays, and atomic absorption and gamma-ray spectrometry were used to analyze the levels of radionuclides and toxic elements, respectively. Potentially toxic elements (Fe, Pb, Zn, Ni, Cr, Cu and Cd) and associated health risks in surface water and sediment of dams were investigated in this present study. The concentrations of Fe, Pb, Zn, Ni, Cr, Cu and Cd in surface water ranged from 5.430 to 9.700 mg·L−1, 0.022 to 0.168, 0.018 to 0.142, 0.065 to 0.366, BDL to 0.0351, BDL to 0.071 and BDL to 0.048 mg·L−1, respectively. In the sediments, the concentrations of Fe, Pb, Zn, Cu, Ni, Cd and Cr were of the order of 136.7, 3.41, 3.22, 0.213, 0.182, 0.15 mg·L−1 and BDL, respectively. The mean radioactivity rates in the water samples were 1.72, 0.068 and 94.6 Bq·L−1 for 238U, 232Th and 40K, respectively (Tunisia dam), and were 1.9, 0.09 and 131.43 Bq·L−1 for 238U, 232Th and 40K, respectively (Algeria dam). The mean 238U, 232Th and 40K radioactivity concentrations measured in the sediment samples were 2.67, 0.18 and 197.87 Bq·kg−1, respectively (Tunisian dam), and were 4.34, 0.27 and 287.61 Bq·kg−1, respectively (Algeria dam). The activity concentration of 40K was higher than that of 238U and 232Th for the water and sediment samples. The activity concentrations follow the order 40K &gt; 238U &gt; 232Th. The cumulative impact of these radio-geochemical elements can cause immediate serious problems in the ecosystem due to their high potential toxicity to the environment and human health in this study area and can be transposable to any other similar region. A good knowledge of monitoring quality and quantity for transboundary water resources and international collaborations are essential to safeguard human health (women’s breast cancer, thyroid cancer, neurological impact) and avoid conflicts, especially during climatic upheavals of drought.

Optimizing spatial interpolation method and sampling number for predicting cadmium distribution in the largest shallow lake of North China

Cadmium (Cd) pollution has been widely recognized in lake ecosystems. Although the accurate prediction of the spatial distributions of Cd in lakes is important for controlling Cd pollution, the traditional monitoring methods of setting discrete and limited sampling points cannot actually reflect the continuous spatial distribution characteristics of Cd. In this study, we set up 93 sampling points in Baiyangdian Lake (BYDL), and collected surface water, overlying water and sediment samples from each sampling point. Cd contents were measured to predict their spatial distributions in different environmental components by three interpolation methods, inverse distance weighted (IDW), radial basis function (RBF) and ordinary kriging (OK), and the effects of different sampling numbers on the interpolation accuracy were also assessed to optimize the interpolation method and sampling number. The results showed that the interpolation accuracy of IDW decreased with increasing power values. The best basis function for RBF was IMQ, and the best semivariogram models for OK were the spherical model and stable model. The best interpolation method for the waters and sediments was RBF-IMQ compared with OK and IDW. Within the sampling number range of 50–93, the interpolation accuracy for Cd in surface water increased with the increase in sampling number. Comparatively, the interpolation accuracy was the highest for overlying water and sediments when the sampling number was 60. The findings of this work provide a combined sampling and spatial interpolation method for monitoring the spatial distribution and pollution levels of Cd in the waters and sediments of shallow lakes.

Multiphase Spatial Distribution Characteristics of Cd Morphology in Typical Intertidal Zones in the Guangdong-Hong Kong-Macao Greater Bay Area and Its Influencing Factors

Simultaneous sampling and observation were conducted at 14 stations in typical intertidal zones of the Guangdong-Hong Kong-Macao greater bay area. The spatial distribution characteristics of Cd morphology in surface water, pore water, suspended matters, and sediments at each sampling site were analyzed, and the influencing factors of Cd morphology changes in each medium were discussed using statistical analyses based on environmental factors. The results showed that the total contents of Cd in surface water, pore water, suspended matters, and sediments in each intertidal zone ranged from 0.41-15.03 μg·L-1, 0.41-27.54 μg·L-1, 0.41-4.88 mg·kg-1, and 0.20-5.30 mg·kg-1, respectively. The contents of Cd in Shajiao Bay were significantly higher than those in other sampling sites, which should be related to the developed electronics and manufacturing industries in Dongguan. The concentration of Cd in surface water was slightly lower than that in pore water, whereas the content of Cd in suspended matter was comparable to that in sediment at the same sampling site. The results of morphological analysis showed that the ionic-state Cd was dominant in both surface water and pore water, accounting for 67.23%-97.56% and 33.33%-97.16%, respectively. In suspended matter and sediment, Cd was mainly in the residual state, accounting for 45.45%-96.36% and 45.80%-97.27%, respectively. Pearson correlation analysis showed that the complex-state Cd in the aqueous phase was negatively correlated with oxidation reduction potential (ORP) and pH and positively correlated with total organic carbon. The bioavailable Cd in solid sediment was significantly positively correlated with the proportion of clay, ORP, and solid organic carbon and significantly negatively correlated with pH. The single factor linear regression analysis showed that ORP had the greatest effect on the complex-state Cd in the aqueous phase, with regression coefficients of 0.864 and 0.824, respectively. The bioavailable Cd in solid sediment at different depths was significantly affected by the proportion of clay, and the regression coefficients were 0.968, 0.980, 0.977, and 0.877, respectively. The above results indicate that the distribution of total Cd content in the typical intertidal environment of the Greater Bay Area was affected by the characteristics of urban economic development, whereas the allocation of Cd morphology was closely related to environmental factors.

Hydrochemical characteristics, trace element sources, and health risk assessment of surface waters in the Amu Darya Basin of Uzbekistan, arid Central Asia.

Thorough knowledge of hydrochemical characteristics and trace element concentrations in surface waters is crucial for protection of this resource, especially in arid regions. Uzbekistan lies in central, arid Central Asia, and is experiencing severe water scarcity as a consequence of warming climate and accelerated human impacts. Fifty-five surface water samples were collected from the Amu Darya Basin of Uzbekistan (ADBU) and measured for relevant variables, to determine hydrochemical characteristics and evaluate water quality. River water samples from the middle reach and Amu Darya Delta (ADD) were dominantly HCO3-Ca and SO4-Ca·Mg types, respectively, whereas water samples collected near the former shoreline and sewage outlets in the ADD were predominantly Cl-Ca·Mg and Cl-Na types, consistent with the distribution of sites that display high concentrations of trace elements and are seriously affected by human activities. Principal component analysis indicated that Pb and Cd in surface waters of the ADBU had industrial origins. Local agricultural activities are thought to have contributed to the concentrations of NO3, Zn, Ni, Hg, and Mn, through pesticide and fertilizer applications, and concentrations of Cu, Cr, As, and Co are controlled by mixed natural and anthropogenic sources. Water quality and health risk assessments indicated that unsuitable drinking waters are distributed mainly near the former shoreline and sewage outlets in the ADD, making human health risks in these areas high.

Spatial variations and periodic changes in heavy metals in surface water and sediments of the Three Gorges Reservoir, China

Substantial changes have occurred in hydrological situation of the Three Gorges Reservoir (TGR) after the operation of the Three Gorges project, as have the heavy metals (HMs) pollution characteristics. In this study, concentrations of Cu, Zn, Pb, Cr, and Cd in surface water and sediments of the TGR were determined during the water impoundment period (December 2015) and water drawdown period (June 2016). The index of geoaccumulation, principal component analysis (PCA), and correlation analysis were used to analyze HMs pollution characteristics. Results showed that HMs concentrations in surface water were much lower than the quality standards for drinking water and surface water of China. The pollution levels of HMs in sediments were nonpolluted for Cr, nonpolluted to moderately polluted for Cu, Zn, Pb, and moderately polluted for Cd. In the fluctuating backflow zone, HMs concentrations in sediments during the water drawdown period were lower than those during the water impoundment period, which was attributed to that faster flow velocity during the water drawdown period resulted in less deposition of suspended solids and faster release of HMs pollutants from sediments to water. HMs concentrations of sediments at sites M14 and M17 showed similar periodic changes to those at the fluctuating backflow zone, which might be attributed to the density-stratified flow in the adjacent upstream tributaries (Meixi River and Qinggan River, respectively). Correlation analysis and PCA analysis results showed that for the sediments, Cr came from natural sources, while Cu, Zn, Pb, and Cd mainly came from anthropogenic sources.

The relationship between cadmium and phosphate in the Atlantic Ocean unravelled

Cadmium (Cd) is not generally considered a nutrient element, but behaves like a nutrient in the oceans and might play an important role in ocean biology after all. The relationship between Cd and the nutrient phosphate (PO4) has been studied for over 40 yrs, but the debate on the driving mechanism and reason behind the ‘kink’, a change in the steepness of the slope is ongoing. Using new data of high accuracy and spatial resolution covering the West-Atlantic Ocean from north to south, in combination with a robust extended optimum multiparameter (eOMP) water mass model, we show that mixing between different water masses is the dominant factor explaining the observed correlation and its kink. Regeneration of Cd via remineralisation explains the smaller scale variability, notably in the surface ocean. Observations imply the availability of Cd in surface waters determines the Cd-uptake and thus the Cd:PO4 remineralisation ratio. This ratio is variable between different ocean regions, notably between the northern and southern high latitude oceans. Due to their role in deep water formation, both the northern and southern high latitude oceans are a driving factor in the Atlantic and global Cd and PO4 relation. Outside the Atlantic Ocean, the classical kink is not expected, but the relationship is by no means linear. Most likely, this is due to the interaction between low latitude surface waters and subsurface waters from high latitude origin, but more data are required to assess this in detail.

Multi-Elements in Source Water (Drinking and Surface Water) within Five Cities from the Semi-Arid and Arid Region, NW China: Occurrence, Spatial Distribution and Risk Assessment.

The purpose of this study was to identify the concentration of multi-elements (MEs) in source water (surface and drinking water) and assess their quality for sustainability. A total of 161 water samples including 88 tap drinking waters (DW) and 73 surface waters (SW) were collected from five cities in Xi’an, Yan’an, Xining, Lanzhou, and Urumqi in northwestern China. Eighteen parameters including pH, electrical conductivity (EC), total organic carbon (TOC) total nitrogen (TN), chemical compositions of anions (F−, Cl−, NO3−, HCO3−, SO42−), cations (NH4+, K+, Na+, Ca2+, Mg2+), and metals (lead (Pb), chromium (Cr), cadmium (Cd), copper (Cu)) were analyzed in the first time at the five cities . The results showed that pH values and concentrations of Cl−, SO42−, Na+, K+, Ca2+, Mg2+ and Cd, Cr, Cu in DW were within the permissible limits of the Chinese Drinking Water Quality Criteria, whereas the concentrations of other ions (F−, NO3−, NH4+ and Pb) exceeded their permissible values. In terms of the SW, the concentrations of F−, Cl−, NO3−, SO42− were over the third range threshold i.e., water suitable for fishing and swimming of the Surface Water Quality Standards in China. The spatial distributions of most MEs in source water are similar, and there was no clear variation for all ions and metals. The metals in DW may be caused by water pipes, faucets and their fittings. The noncarcinogenic risk of metals in DW for local children are in decreasing order Cr > Cd > Pb > Cu. The carcinogenic risk from Cr exposure was at the acceptable level according to threshold of USEPA. Although the comprehensive index of potential ecological assessment of Cr, Cd, Pb and Cu in SW ranked at low risk level and was in the order of Huang River in Xining > Peaceful Canal in Urumqi > Yan River in Yan’an > Yellow River in Lanzhou, their adverse effects to ecology and human health at a low concentration in local semi-arid and arid areas should not be ignored in the long run.

Does soil water saturation mobilize metals from riparian soils to adjacent surface water? A field monitoring study in a metal contaminated region

In the Noorderkempen (NW Belgium), a large area (about 280 km(2)) is contaminated with cadmium (Cd) and zinc (Zn) due to historical pollution by the Zn smelters. Direct aquatic emissions of metals have diminished over time, however the surface water metal concentration largely exceeds quality standards, mainly during winter periods. Monitoring data were analyzed to reveal whether these fluctuations are related to seasonal redox reactions in associated contaminated riparian soils that drain into the rivers. A field survey was set up with soil pore-water and groundwater monitored for three years in transects of soil monitoring points perpendicular to rivers at contaminated and non-contaminated sites. Site averaged surface water concentrations of a 15 year dataset exceeded local quality standards 4 to 200-fold. Winter averaged metal concentrations significantly exceeded the corresponding summer values 1.3-1.8 (Zn) and 1.5-2.4 fold (Cd). Zinc and Cd concentrations in water were positively related to Fe and Mn but not to Ca, K or Na suggesting that redox reactions and not dilution processes are involved. In ground- and pore-water of the associated riparian soils, the concentrations of Zn fluctuate by the same order of magnitude as in surface water but were generally smaller than in the corresponding contaminated rivers. In addition, correlations of dissolved Zn with Fe and Mn were lacking. This analysis suggests that redox reactions in streams, and not in riparian soils, explain the seasonal trends of Zn and Cd in surface water. Hence, river sediments and not riparian soils may be the cause of the winter peaks of Zn and Cd in these rivers.

The isotopic composition of Cadmium in the water column of the South China Sea

We determined the Cd isotopic composition of seawater and sinking particles collected in the deep basin of the northern South China Sea (SCS) to investigate the controlling mechanisms on the Cd isotopic composition in the water column. The isotopic composition in the water column decreased with depth, with ε114/110Cd values (ε114/110Cd=[(114Cd/110Cd)sample/(114Cd/110Cd)JMC Cd Münster−1]×104) ranging from +8.7 to +9.9 in the top 80m, from +4.6 to +5.5 between 100 and 150m, decreasing from +5.5 to +3.6 at depths from 150 to 1000m, and remaining at +3.4±0.5 from 1000 to 3500m. The isotopic composition and concentrations of Cd observed in the deep waters of the SCS are similar to the values that were previously reported in the North Pacific Ocean. In the thermocline, the variations in the Cd isotopic composition and concentrations were consistent with the relative volumetric percentages of the subsurface water, the intermediate water, and the deep water in the water column, indicating that water mixing is the dominant process determining the isotopic composition in the thermocline. Comparable to the isotopic composition value in the seawater of the mixed layer, the ε114/110Cd in the sinking particles collected at 30m was +9.3±0.9. Because our previous studies demonstrated that the particulate Cd was predominantly biogenic organic matter, the comparable isotopic composition between the surface seawater and the sinking particles indicates that net biological isotopic fractionation on Cd in the surface water was insignificant. The result indicates that phytoplankton do not necessarily take up relatively light Cd in the oceanic surface waters. It is necessary to directly and systematically investigate how marine phytoplankton fractionate Cd isotopes.

Dynamics and quantification of dissolved heavy metals in the Mahanadi river estuarine system, India

Dynamics of heavy metals such as Fe, Mn, Zn, Cr, Cu, Co, Ni, Pb, and Cd in surface water of Mahanadi River estuarine systems were studied taking 31 different stations and three different seasons. This study demonstrates that the elemental concentrations are extremely variable and most of them are higher than the World river average. Among the heavy metals, iron is present at highest concentration while cadmium is at the least. The spatial pattern of heavy metals suggests that their anthropogenic sources are possibly from two major fertilizer plants and municipal sewage from three major towns as well as agricultural runoff. The temporal variations for metals like Fe, Cu, and Pb exhibit higher values during the monsoon season, which are related to agricultural runoff. Concentrations of Ni, Pb, and Cd exceed the maximum permissible limits of surface water quality in some polluted stations and pose health risks. Dissolved heavy metals like Fe, Mn, Cr, Ni, and Pb exhibit a non-conservative behavior during estuarine mixing, while Zn, Cu, and Co distribution is conservative. Distribution of cadmium in the estuarine region indicates some mobilization which may be due to desorption. The enrichment ratio data suggest that various industrial wastes and municipal wastes contribute most of the dissolved metals in the Mahanadi River. The Mahanadi River transports 18.216 × 10(3) t of total heavy metals into the Bay of Bengal and the calculated rate of erosion in the basin is 128.645 kg km(-2) year(-1).

Inter-annual trends of heavy metals in marine resources from the Nigerian territorial waters

In an attempt to monitor and assess the pollution status of marine resources in the Nigerian territorial waters, this study was carried out to reveal the levels and inter-annual trend of heavy metals in marine resources from the Lagos lagoon marine ecosystem. Studies were carried out annually in the month of July between 2007 and 2009; and the observed levels and trends are herein reported and discussed. Drastic shoot up was observed in year 2009 at all locations in the levels of Fe, Zn, Cu, Cr, Pb, and Cd in surface water, with maximum values of 0.62, 1.14, 0.07, 0.06, 0.08, and 0.09 mg/L, respectively reported at the near shore locations. The maximum values recorded in year 2007 for Fe, Zn, Cu, Cr, Pb, and Cd in bottom sediments were 11533, 76.57, 16.23, 38.3, 41.29, and 0.94 mg/kg respectively. This study revealed a general inter-annual trends of 2009 > 2008 > 2007. This trend is alarming and it is of great concern considering the associated health and economic implications.

Anthropogenic sources and environmentally relevant concentrations of heavy metals in surface water of a mining district in Ghana: a multivariate statistical approach

The levels of heavy metals in surface water and their potential origin (natural and anthropogenic) were respectively determined and analysed for the Obuasi mining area in Ghana. Using Hawth's tool an extension in ArcGIS 9.2 software, a total of 48 water sample points in Obuasi and its environs were randomly selected for study. The magnitude of As, Cu, Mn, Fe, Pb, Hg, Zn and Cd in surface water from the sampling sites were measured by flame Atomic Absorption Spectrophotometry (AAS). Water quality parameters including conductivity, pH, total dissolved solids and turbidity were also evaluated. Principal component analysis and cluster analysis, coupled with correlation coefficient analysis, were used to identify possible sources of these heavy metals. Pearson correlation coefficients among total metal concentrations and selected water properties showed a number of strong associations. The results indicate that apart from tap water, surface water in Obuasi has elevated heavy metal concentrations, especially Hg, Pb, As, Cu and Cd, which are above the Ghana Environmental Protection Agency (GEPA) and World Health Organisation (WHO) permissible levels; clearly demonstrating anthropogenic impact. The mean heavy metal concentrations in surface water divided by the corresponding background values of surface water in Obuasi decrease in the order of Cd > Cu > As > Pb > Hg > Zn > Mn > Fe. The results also showed that Cu, Mn, Cd and Fe are largely responsible for the variations in the data, explaining 72% of total variance; while Pb, As and Hg explain only 18.7% of total variance. Three main sources of these heavy metals were identified. As originates from nature (oxidation of sulphide minerals particularly arsenopyrite-FeAsS). Pb derives from water carrying drainage from towns and mine machinery maintenance yards. Cd, Zn, Fe and Mn mainly emanate from industry sources. Hg mainly originates from artisanal small-scale mining. It cannot be said that the difference in concentration of heavy metals might be attributed to difference in proximity to mining-related activities because this is inconsistent with the cluster analysis. Based on cluster analysis SN32, SN42 and SN43 all belong to group one and are spatially similar. But the maximum Cu concentration was found in SN32 while the minimum Cu concentration was found in SN42 and SN43.

Estival Distribution of Dissolved Metal Concentrations in Liaodong Bay

The temporal and spatial distributions of Cu, Pb, Zn, and Cd in surface water of the Liaodong Bay were studied based on samples collected at 16 sites in June and August from 2001 to 2005. The temporal distribution showed decreasing trends. The concentrations of dissolved metals in the Liaodong Bay were 4.34, 3.21, 31.54, and 0.995 mug/L for Cu, Pb, Zn, and Cd, respectively. Cu and Pb were scattered near the estuaries, and Zn and Cd were mainly found near the Wuli River. Rivers were the main metals pollution sources in the Bay.

Source identification and spatial variability of nitrogen, phosphorus, and selected heavy metals in surface water and sediment in the riverine systems of a peri-urban interface

This study was conducted, using an elaborate sampling activity of surface water and sediment within an industrially developed peri-urban interface with a riverine system in Wuxi, Taihu Lake area, China, to address the following objectives: (i) to identify possible sources of selected nutrients such as N and P, and heavy metals such as Cu, Zn, Pb, Cr, and Cd in surface water and sediments, and (ii) to determine the spatial variability of these elements around the source areas. The results showed that concentrations of N and P in the surface water and Cu, Zn, Cr, and Pb in most of sediments had exceeded trigger levels established by the nation, while all metal concentrations in surface water were still below the levels. The source identification of these pollutants in water and sediments in terms of their spatial distribution pattern and principal component analysis showed that: (i) Pb, N and organic carbon (OC) were closely related to the influence of urban runoff and domestic wastewater; (ii) Cu and Cr were related to the influence of industries; and (iii) P and Zn were related to the effect of both urban and industries. The results of this study showed that urbanization is the main contributor for N and P in the peri-urban interface instead of agricultural sources. The concentrations of N, P, Cu, Zn, Pb, and Cr in the sediment along the main river decreased with the distance away from the source area. The concentrations of these elements decreased to the background levels at about 4.5–5.5 km downstream of the source of origin.

Environmental impact of metalliferous black shales at Talvivaara in Finland, with indication of lake acidification 9000 years ago

Environmental impact of metalliferous black shales was studied in the Talvivaara area in eastern Finland with 194 lake sediment and 48 organic stream sediment samples and 57 surface water and 9 ground water samples. The samples were analysed using a combination of ICP–MS and ICP–AES methods. Continuous undisturbed lake sediment cores were obtained from seven lakes. Cores from three of the lakes penetrated through the sediment column into the underlying clay, which was deposited in a late glacial ice-dammed lake between 12,000 and 9000 years ago. The concentrations of Ni, Zn, and Cd in surface water and organic stream and lake sediments were significantly greater if the bedrock of the catchment area consisted of black shales than if it consisted of gneiss granite or quartzite. It appeared that this was also the case in the past. The influence of bedrock chemistry is particularly pronounced in the Lake Härkälampi profile at a depth of 358 cm, which records the abrupt isolation of the lake from the Sotkamo ice-dammed lake 9000 years ago. At this time, the metalliferous black shales of the catchment area were exposed to prolonged wave action and erosion, and pH dropped to as low as 3.8. Following isolation of the lake the organic content of the sediment steadily increased, attaining a maximum value of 13% at a depth of 310 cm. Maximum Ni (0.1%), Cu (0.03%), Zn (0.5%), and Al (3.4%) concentrations are recorded shortly after isolation, when the proportion of organic material was still as low as 2.7%. Evidently vegetation effectively reduces bedrock weathering even in cool climate, since Ni, Cu, Zn, and Al concentrations decreased and pH increased in Lake Härkälampi due to colonization of tundra vegetation.

Cadmium, copper, lead and zinc on transects through Arctic and Eastern Atlantic surface and deep waters

A total of 230 surface and 70 deep water samples was collected during several transects in the European Arctic and the East Atlantic. The distribution of Cd in surface waters of the Arctic is associated with the nutrient regime and the primary production. In the euphotic zone about 80% of dissolved Cd is eliminated by phytoplankton corresponding to a ΔCd: ΔPO 4 ratio of 1.7 × 10 −4. In addition, there is a reverse linear relationship with Chlorophyll a. Regional fluctuations could be demonstrated: the highest Cd concentrations (0.25 nmol·kg −1) were on the East Greenand shelf, by a factor of 3–4 lower values in the frontal systems, and medium levels (0.1 nmol·kg −1) were observed in the mixing waters of the Greenland Sea gyre. Eastern Atlantic Cd concentrations are sometimes near the detection limit (<0.02 nmol·kg −1) and 5–20 times lower in surface waters than in the Arctic study areas. In contrast Atlantic deep water values at the nutrient maxima were 2–3 times higher than in the Arctic study areas. Good correlations between Cd/Phosphate with a mean slope of 1.2 × 10 −4 were found for the deep water stations in the East Atlantic Basins. Lead showed the lowest dissolved concentrations in waters of the ice covered region of the East Greenland shelf (0.02 nmol·kg −1) and in the South Atlantic (0.05 nmol·kg −1), with increases by 10–20 times in the region of the Greenland Sea gyre and 3–5 times in the region of the westerlies. Concentrations in sea ice were 70 times higher than in the surrounding water masses. Regional averages of the Cu concentrations in Arctic areas fluctuate between 4 nmol·kg −1 on the East Greenland shelf and 1 nmol·kg −1 in the mixing waters of the Greenland Sea gyre. Interannual Cu distribution was rather constant in Arctic and Atlantic surface waters. Seven vertical profiles in Eastern Atlantic basins showed a strong correlation between Cu/SiO 2 with a slope of 0.028 nM/μM. Zn concentrations in surface waters of the Arctic region may have one source in the atmospheric input, as shown by high Zn concentrations of sea ice (1–13 nmol·kg −1) from the ice covered region. Lowest values (0.3–0.8 nmol·kg −1) were determined in 1989 between 35°S and 25°N in East Atlantic surface waters. The data for the trace metals are discussed in the context of the hydrography and the nutrient situation of the two areas under investigation.

The determination of heavy metals in the ligurian sea. I, the distribution of Cu, Co, Ni and Cd in surface waters

Determinations of Cu, Co, Ni and Cd were carried out on 39 samples of surface seawaters from the Ligurian Sea, nearshore and offshore, between the Isola Capraia and Imperia. The concentrations of trace elements have been established employing the analytical method suggested by Le Meur and Courtot-Coupez (1973), by means of concentration of the sample by chelating resin, solvent extraction of the eluate and then by quantitative determination by AAS. The results obtained with this technique probably refer to ionic forms of the elements only. The Co concentration was lower than 0.15 μg 1 −1 in 32 samples, with an average of 0.49 μg 1 −1 for the others. For Cd, the greater number of samples had a content lower than 0.05 μg 1 −1 . For the others the mean concentration was 0.13 μg 1 −1 . The Ni had a mean concentration of 0.93 μg 1 −1 and the average Cu content was 1.43 μg 1 −1 . Our data are in agreement with the values published by authors who have employed the same analytical technique. We observed that the offshore samples present a concentration lower than that in the nearshore samples.