Ecophysiological Studies of the Adriatic Seaweed, Fucus virsoides

Abstract. The Adriatic brown macroalga Fucus virsoides (DON.) J. Ac (Fucales, Phaeophyceae) was investigated with particular respect to basic physiological features such as photosynthesis, dark carbon fixation, and respiration. Values obtained are expressed in various reference systems. Chemical composition of the fronds and physiological activity (photosynthesis/dark fixation along with the respective carboxytating enzymes (ribulose-1,5-bisphophate carboxylase and phosphoenol-pyruvate carboxykinase) show longitudinal profiles. Temperature characteristics of photosynthesis in long-term adapted specimens indicate reduced productivity at temperatures exceeding 20 °C. Photosynthesis during atmospheric exposure is markedly increased under moderate desiccation. Photosynthetic rates steadily decline under reduced salinity of the incubation medium, while respiration is stimulated. Net primary productivity of a F. virsoides stand at 15 °C ambient average temperature, tidal exposure for maximally 2–3 hours and light-dark regime = 12: 12 is calculated as 4.8-5.4 g C m^-2d-1. Culture experiments with polluted incubation media provide evidence that excessive nutrients including nitrate and phosphate as well as high concentrations of heavy metals (Zn, Co, Mn) cause severe growth-rate reduction which may account for the steady decrease of F. virsoides in its natural habitat. The results are discussed with emphasis on the autecology of F. virsoides and its relationships to Atlantic representatives of the genus.     

Trends of trace metal (Mn, Fe, Co, Ni, Cu, Zn, Cd and Pb) distributions at the oxic-anoxic interface and in sulfidic water of the Drammensfjord

Anoxic sulfidic waters provide important media for studying the effect of reducing conditions on the cycling of trace metals. In 1987–1988, dissolved and particulate trace metal (Mn, Fe, Co, Ni, Cu, Zn, Cd and Pb) concentrations were determined in the water column of the anoxic Drammensfjord basins, southeastern Norway. The iminodiacetic acid type chelating resin (Chelex 100) was used for the preconcentration of trace metals. The trace metal concentrations were determined using atomic absorption spectrophotometry (AAS), differential pulse polarography (DPP), and differential pulse-anodic stripping voltammetry (DP-ASV).It was observed that the trace metals Mn and Fe were actively involved in the processes of redox cycling (oxidationreduction and precipitation-dissolution) at the O₂/H₂S interface. The dissolved concentrations of Mn, Fe and Co showed maxima just below the O₂/H₂S interface. The seasonal enhancement in the maxima of both dissolved and particulate Mn and Fe at the redox cline is mainly governed by the downward movement of water which carries oxygen. An association of Co with the Mn cycle was observed, while the total dissolved Ni was decreased by only 10–35% in the anoxic waters. The dissolved concentrations of Cu, Zn, Pb and, to a lesser extent, Cd decreased in the anoxic zone.     

长江口最大浑浊带潮周期内悬浮物中的重金属

In order to discuss the content distributions and fluxes of heavy metals in suspended matters during a tidal cycle in the turbidity maximum around the Changjiang(Yangtze) Estuary,the contents of heavy metals(Zn,Pb,Cd,Co and Ni) have been analyzed.During a tidal cycle,the average contents of heavy metals are in the order of ZnNiPbCo àCd.The average contents in ebb tide are generally higher than that in flood tide.However,at the inshore Sta.11,influenced by the contamination from the nearby waste treatment plant,the average contents of Zn and Ni in flood tide are higher than those in ebb tide and at the offshore Sta.10,the content of Cd in flood tide higher than that in ebb tide due to marine-derived materials.The five heavy metals,mainly terrigenous,are transported towards east-northeast,and settle down with suspended matters in the area between Sta.11 and Sta.10.Influenced by marine-derived materials,the flux value of Cd does not alter significantly with obviously changing in flux direction towards northwest.The source of heavy metals,the salinity of water and the concentration of suspended matters are the main factors controlling the content distributions of heavy metals during a tidal cycle.There is a positive correlation between the contents of heavy metals(Zn,Pb,Co and Ni) and the salinity of water,while the opposite correlation between the contents and the concentrations of suspended matters.Because of marine-derived materials,the content of Cd is not correlated with the concentration of suspended matters and the salinity of water.     

Phosphorus and metals bound to organic matter in coastal sediments - An investigation of complexes of P,Cu, Zn,Fe, Mn,Ni, Co and Ti by inductively coupled plasma-atomic emission spectrometry with sephadex gel chromatography

Phosphorus and metals bound to organic matter were separated from coastal sediments of Harima Sound in Seto Inland Sea, Japan by extraction with NaOH and fractionated by Sephadex G-25 chromatography. Phosphorus and metals were determined in the eluates by a multi-channel, inductively coupled plasma-atomic emission spectrometer. Phosphorus and Cu, Zn, Fe, Mn, Ni, Cr, Co and Ti bound to organic matter with high molecular weights (OMHMW) (MW ? 5000) were found to be present in the sediments, but no Mo or V were found. The technique provides minimum estimates of the amounts of P and metals bound to organic matter. These organic complexes show surface enrichment in a sediment core (0–20 cm) and their contents decrease with depth. Also, the amounts of eighteen elements, namely: P, Fe, Mn, Zn, Cu, Si, Al, Ti, Pb, Co, Ni, Cr, Mo, V, Na, K, Ca and Mg, in H₂O, ammonium acetate at pH 7 and 5, hydrogen peroxide, hydroxylamine hydrochloride and hydrogen fluoric acid soluble fractions have been determined with a selective chemical leaching technique for the ²¹⁰Pb-dated sediment core sample. Considerable amounts of P (6–19%) and Cu (5–21%) were associated with organic matter, in contrast to other metals such as Fe, Mn, Zn, Ni, Cr, Co and Ti which were associated with sulfide and silicate.     

Diagnosis of trace metal contamination in sediments: the example of Ensenada and El Sauzal, two harbors in Baja California, Mexico

Total metal concentrations in sediments from within Ensenada and El Sauzal Harbors are generally higher than at the mouths. Grain-size analyses suggested that this enrichment could be due to the presence of fine-grained sediments in the inner part of the harbors rather than to anthropogenic perturbations. The (Me/Al)(sample) ratios for Pb, Co, Ni and Fe were significantly higher for Ensenada Harbor relative to El Sauzal Harbor, whereas the ratios for Cd, Mn, Zn and Cu were statistically equivalent for both harbors. Calculated enrichment factors [EF(Me)=(Me/Al)(sample)/(Me/Al)(shale)] indicated that the metals showing slight enrichment were those associated with anthropogenic contamination (Pb, Zn), or probably related to primary productivity in the water column (Cd, Co). The levels of most of the metals were not greatly enriched, a consideration that is of the utmost importance when contamination issues are at stake.     

Metal sources to the Baltic clam Macoma balthica (Mollusca: Bivalvia) in the southern Baltic Sea (the Gulf of Gdansk)

Metal concentrations of Cu, Fe, Mn, Ni, Pb and Zn in an infaunal facultative deposit-feeding bivalve, the Baltic clam Macoma balthica, in the Gulf of Gdansk (southern Baltic Sea) were assessed and compared to selected concentrations of metals in the environment. Between October 1996 and September 1997, dissolved and easy extractable (by 1M HCl) metal fractions of total suspended particulate matter (TPM) in the overlying water and of surficial sediments (<63 microm) were measured monthly at five sublittoral sites in the Gulf of Gdansk, and accumulated tissue metal concentrations in M. balthica were determined simultaneously. The study highlights the importance of sediment geochemistry as a factor modifying ambient trace metal bioavailabilities. Surficial sediments appeared to contribute most to the accumulation of Cu and Pb in M. balthica, reflecting the high metal availability in the Gulf. Assimilation of Cu from sediments is controlled by Mn components possibly through an inhibitory effect of Mn oxyhydroxides, while Pb accumulation from sediments depends on the organic content of the sediment. A dual metal uptake pathway, with a suspended particulate-bound fraction and surficial sediments, was apparent for Mn and Zn. Partitioning of Mn in sediments was related to the concentration of labile Fe, with increased levels of Fe tending to inhibit the accumulation of Mn by the clam. Tissue accumulated Zn might have been altered by the clam's internal regulation, making Zn tissue concentrations, to some degree, independent of its environmental level. The principal source of Ni accumulated by the clams exists in the soluble phase.     

Geochemical and geo-statistical assessment of heavy metal concentration in the sediments of different coastal ecosystems of Andaman Islands,India

Spatial distribution of metal concentrations in the surface sediment samples collected from 16 marine locations covering different coastal ecosystems such as mangroves, seagrasses, dead coral and sandy beaches of the Andaman islands, India was studied. pH, EC, sediment grain size and heavy metal (Al, Cd, Co, Cr, Cu, Fe, Mg, Mn, Ni, Pb and Zn) concentrations were determined and contamination factor (CF) and geo-accumulation index (I_geo) were calculated to understand the pollution status of the study area based on the background values. CF of different heavy metals has revealed that different metals have different levels of accumulation viz. Al: 0.01–0.22, Mg: 0.38–1.85, Fe: 0.06–0.74, Mn: 0.04–1.18, Cu: 0.18–2.93, Cr: 0.52–12.6, Zn: 0.3–1.39, Ni: 0.06–0.89, Pb: BDL–0.74, Co: 0.1–0.35 and Cd: 2.3–12.9. In general the metal concentration was less in these ecosystems when compared to similar ecosystems of mainland of India. Concentration of some metals like Cr and Cd was comparatively higher than the background values which is an important issue of concern to the coastal managers of the region. Spatial data on heavy metals, collected now, would help the coastal zone managers to identify the vulnerable sites and take remedial actions.     

Effects of salinity, temperature and food type on the uptake and elimination rates of cd, cr, and zn in the asiatic clamcorbicula fluminea

Laboratory radiotracer experiments were conducted to determine assimilation efficiencies (AE) from ingested algal food and oxic sediment particles, uptake rates from the dissolved phase, and the efflux rates of Cd, Cr and Zn in the Asiatic clamCorbicula fluminea. Among three elements, AE from both algal and sediment food was greatest for Cd, followed by Zn and Cr. The AEs of tested elements from algal food(Phaeodactylum tricornutum) were consistently higher than those from sediments at a given salinity and temperature. The influence of salinity (0, 4 and 8 psu) and temperature (5, 13 and 21¼) on the metal AEs was not evident for most tested elements, except Cd AEs from sediment. The rate constant of metal uptake from the dissolved phase (k _u was greatest for Cd, followed by Zn and Cr in freshwater media. However, in saline water, thek _u of Zn were greater than those of Cd. The influx rate of all tested metals increased with temperature. The efflux rate constant was greatest for Cr (0.02 d^-1), followed by Zn (0.010~0.017 d^-1) and Cd (0.006 d^-1). The efflux rate constant for Zn in clam tissues depurated in 0 psu (0.017 d^-1) was faster than that in 8 psu (0.010 d^-1). Overall results showed that the variation of salinity and temperature in estuarine systems can considerably influence the metal bioaccumulation potential in the estuarine clamC. fluminea. The relatively high Cd accumulation capacity ofC. fluminea characterized by the high AE, high dissolved influx rate and low efflux rate, suggested that this clam species can be used as an efficient biomonitor for the Cd contamination in freshwater and estuarine environments.     

Some peculiarities of the trace-metal distribution in Baltic waters and sediments

Between 1980 and 1984 extensive studies were carried out in the Baltic Sea on trace metals (Cd, Co, Cu, Fe, Hg, Mn, Ni, Pb and Zn) in water, suspended matter and sediments. The results enabled the influence of different factors on metal distribution patterns to be considered. The vertical profiles of dissolved and particulate metals in waters of the central deep basins reflect influences caused by oxygen deficiency and anoxic conditions in near-bottom water layers. Peculiarities at Station BY15 in the Gotland Deep included high dissolved Fe, Mn and Co concentrations and remarkable enrichment of Zn (0.64%), Cd (51 μg g⁻¹) and Cu (0.15%) in particulate matter from the anoxic zone. Manganese-rich particles were accumulated above this layer.In fine-grained soft sediments below anoxic deep waters, maximum contents of Cd, Cu and Zn were observed, relative to other coring sites, between Bothnian Bay and Lübeck Bight. The Hg content in sediments probably reflects the joint flocculation with organic matter. Land-based sources seem to play the leading part for maximum lead contents.     

Distribution and Enrichment of Heavy Metals in Recent Sediments of Safaga Bay,Egypt

The present study was undertaken for assessing the level of heavy metals such as iron, manganese, zinc, copper, nickel, cadmium, lead, and cobalt in recent sediment samples of Safaga Bay, Egypt. Concentration of heavy metals in sediments shows significant variability and ranges from 863.37 to 1144.93 ppm for Fe, 64.29–586.8 ppm for Mn, 2.7–12.68 ppm for Zn, 3.01–7.2 ppm for Pb, 1.53–3.29 ppm for Ni, 0.55–1.57 ppm for Co, 0.16–1.37 ppm for Cu, and 0.22–0.4 ppm for Cd.

Sediment pollution assessments were carried out using an enrichment factor and geoaccumulation index. The calculation of enrichment factor showed that Cd is enriched by 4.1 due to phosphate sources in Safaga Bay. The Geoaccumulation index results revealed that there are positive and negative correlations between Fe, Zn, Mn, Pb, Ni, Cu, Co, and Cd indicating that these metals have complicated geochemical behaviors.     

碱蓬（Suaeda salsa）对胶州湾滨海湿地重金属的富集与迁移作用

通过对胶州湾东北部滨海湿地5个采样点生长的碱蓬中10种重金属Cu、Zn、Pb、Cd、As、Cr、Co、Ni、V、Mo的系统研究,发现碱蓬对Cu,Zn的吸收明显高于其它重金属,这可能与Cu和Zn是植物生长发育必需的微量元素有关,碱蓬体内Cr、Pb、V和Ni的含量也相对较高。碱蓬对Mo的富集效果最为显著,对Cu、Zn、Cd...     

Simplified synthesis of an 8-hydroxyquinoline chelating resin and a study of trace metal profiles from Jellyfish Lake, Palau

We report a simplified synthesis, and some performance characteristics, for 8-hydroxyquinoline (8-HOQ) covalently bonded to a chemically resistant TosoHaas TSK vinyl polymer resin. The resin was used to concentrate trace metals from stored, acidified seawater samples collected from Jellyfish Lake, an anoxic marine lake in the Palau Islands. The Mn, Fe, and Zn profiles determined from the 8-HOQ resin extraction were similar to those determined using Chelex-100 resin. The Zn and Cd profiles did not exhibit removal by sulfide “stripping” in contrast to other anoxic marine basins. The profiles of Co and Ni also exhibited elevated concentrations in the anoxic hypolimnion. The solution speciation and saturation states for the metals were calculated using revised metal-bisulfide stability constants. The calculations suggest that the MS(HS)⁻ species dominates the solution speciation for Mn, Co, Ni, Zn, Cd, and Pb. Cu(I) is modeled as the CuS⁻ or Cu(HS)₂⁻ species, while Fe(II) behaves as the free Fe²⁺ cation. The Mn, Co, Ni, Cu and Cd concentrations appeared to be at least 10-fold undersaturated, while the Fe(II), Zn, and Pb concentrations were close to saturation with respect to their metal sulfides.     

盐城海岸带表层土壤重金属的空间分布及其影响因素研究

以盐城海岸带为研究对象,分析了Cr,Cu,Fe,Mn,Ni,V,Zn,Co,Cd 9种重金属元素在二维空间分布的异质性,以及沿着经纬度方向的梯度变化,并通过主成分分析和元素区域背景值的分析,探讨重金属元素的可能来源.结果表明:自陆向海存在着逐渐减少的格局梯度,而在区域的北部分布着重金属元素的峰值;二维分析的结果表明,重...     

厦金海域珊瑚体内重金属水平和分布特征

采用电感耦合等离子体质谱仪测定了厦金海域8种珊瑚中Cr、Mn、Co、Ni、Cu、Zn、As、Cd、Sn、Sb、Pb重金属的含量,通过数据处理、主成分分析方法,分析了重金属分布特征和其主要来源。采用单因子污染指数法对珊瑚重金属的污染水平进行了评价。结果表明,其平均浓度水平从大到小依次为:ZnMnSnCrCuAsNiPbSbCdCo。在8种珊瑚中,星柳珊瑚(Astrogrogia sp.)、等柳珊瑚(Paris fruticosa)、Paraplexaura sp.的重金属含量较高,花柳珊瑚(Anthogorgia sp.)和Guaiagorgia anas的含量较低。台湾海域珊瑚中Cu、Zn、Pb、Ni的含量、委内瑞拉海域珊瑚中Zn、Pb、Ni的含量远高于厦金海域珊瑚体内相同重金属含量,大堡礁珊瑚中Cu含量较厦金海域的略高。通过相关性分析发现,Cr、Co、Ni、Zn和Sn的种间差异较为显著。根据主成分分析,厦金海域珊瑚体内重金属元素可能的污染来源有:农业污染、港口生活污水和工业污水的排放、船舶油漆、涂料侵蚀、电镀工业。单因子污染指数法评价结果表明,6种重金属元素中,大佰屿、白哈礁和角屿的主要污染物是Mn。白哈礁、大佰屿站位的珊瑚体内重金属Mn处于重度污染水平,角屿站位的处于中度污染水平。     

Effect of zinc on regeneration in the fiddler crab Uca pugilator and its interactions with methylmercury and cadmium

After multiple autotomy (one chela and six walking legs) fiddler crabs (Uca pugilator) were exposed to zinc chloride, cadmium chloride, methylmercuric chloride or combinations of these metals. Zinc at 1, 3 and 5 ppm had a retarding effect on limb regeneration, which was amplified in water of reduced salinity. Methylmercury at 0·5 ppm and cadmium at 1·0 ppm have previously been found to retard regeneration. When crabs were exposed to meHg and Zn the effects were additive, both in sea water (30% salinity) and in water of reduced salinity (7–8%). However, when crabs were exposed to combinations of Zn and Cd the effects were antagonistic and the rate of regeneration was almost that of controls. In water of 7–8% salinity the Cd effect was greatly intensified and growth was almost totally prevented. The presence of Zn counteracted this and allowed growth and ecdysis to occur.     

Toxicity,growth and accumulation relationships of copper,lead and zinc in the grey mangrove Avicennia marina (Forsk.) Vierh

The effects of three heavy metals Copper (Cu), lead (Pb) and zinc (Zn), and the interaction of an essential (Zn) and non-essential (Pb) metal on germination, growth, and accumulation of metals in the grey mangrove, Avicennia marina (Forsk.) Vierh var. australasica (Walp.) Moldenke, were studied under laboratory conditions. Avicennia marina was found to be highly tolerant to the metals applied. Copper was accumulated in root tissue in a linear relationship at lower sediment concentrations, but at concentrations of 200 microg/g and higher, no further increases in root Cu levels occurred. Translocation of Cu from the root to leaf tissue was low, yet revealed similar accumulation patterns as root tissue. Significant reductions in seedling height leaf number and area were found with significant increases in Cu concentrations in tissues at 100 microg/g sediment Cu. At Cu sediment levels of 400 microg/g, a decrease in total biomass and root growth inhibition was observed. Emergence was retarded with increasing copper concentration, with 800 microg/g sediment Cu resulting in a total inhibition of emergence. The LC50 for emergence and EC50 for biomass was 566 and 380 microg/g Cu respectively. Lead accumulation in root tissue was lower that other metals, yet increased in a dose dependant fashion across the sediment Pb concentration range examined. Lead was excluded from leaf tissue at Pb sediment concentrations up to 400 microg/g, above which limited transport of Pb occurred. Little negative effects on growth were observed due to the low accumulation of Pb. Zinc uptake was high, and was accumulated in a linear fashion in root tissue across the sediment Zn concentration range applied. Zinc translocation to leaf tissue exhibited a dose dependant relationship with both root and sediment Zn levels. Emergence decreased with increasing sediment Zn concentrations, with 1000 microg/g sediment Zn showing 100% mortality. Significant reductions in seedling height, leaf number, area, biomass and root growth inhibition were found at concentrations of 500 microg/g sediment Zn. The LC50 for emergence and EC50 for biomass was 580 and 392 microg/g Zn respectively. Lead and Zn in combination resulted in an increased accumulation of both metals in leaf tissue and increased toxicity than individual metals alone, and is the first noted occurrence of a Pb and Zn additive response in angiosperms. Possible mechanisms of accumulation and toxicity are discussed.     

九龙江口和厦门西港海域若干重金属元素的生物地球化学特性

根据１９８７年３月至１９８８年１２月九龙江口，厦门西港海域的调查资料，初步探讨该海域Ｆｅ，Ｍｎ，Ｃｕ，Ｚｎ，Ｎｉ，Ｃｏ，Ｐｂ，Ｃｄ等重金属元素的生物地球化学特性，及其与磷的生物地球化学的关系。结果表明该海域重金属元素的分布主要受九龙江径流的影响。在河水与海水混合过程中，悬浮颗粒态重金属元素发生明显转移，Ｆｅ，Ｍｎ，Ｃｏ，Ｚｎ等元素自悬浮颗粒物上解吸，Ｃｕ可能被吸附，颗粒态重金属元素与颗粒态磷呈良好     

Ecotoxicological approach for assessing the contamination of a Hawaiian coral reef ecosystem (Honolua Bay, Maui) by metals and a metalloid

The goal of this study was to assess the contamination of Honolua Bay using an ecotoxicological approach. First, the concentrations of 9 contaminants (metals and metalloid) were assessed in sediments and tropical marine organisms (alga Halimeda kanaloana, goatfish Parupeneus multifasciatus and urchin Tripneustes gratilla) sampled from Honolua and surrounding Bays. Then, the ecological parameters characterizing coral health (e.g. coral cover) were evaluated in Honolua Bay in the context of these contaminants. High concentrations of Co, Cr, Mn, Ni, and V in sediments from Honolua and Honokohau Bay were measured, but these concentrations were not mirrored in the organisms examined, except for Mn, suggesting that the metals are generally bound in chemically inert forms in these sediments. Moreover, few anthropogenic activities impact these bays and so the elevated Co, Cr, Mn, Ni and V concentrations in sediments appear to stem from their high natural background in Honolua and Honokohau watersheds. An analysis of the relationship between the ecological parameters and metal concentrations in Honolua Bay revealed a significant correlation between coral cover and Co, Cr, Mn, Ni, V, Zn concentrations in sediments, with coral cover decreasing with increasing metal concentration. Collectively, however, the data suggest that a complex mixture of land-based stressors (e.g. sediment, metals, nutrients) affect the coral health in Honolua Bay, rather than metal stress alone.     

Effects of temperature on scope for growth and accumulation of Cd, Co, Cu and Pb by the marine bivalve Mytilus edulis

In many aquatic organisms including Mytilus edulis, the role of temperature on bioaccumulation of metals is still not clearly understood. In this study, uptake and accumulation of Cu, Co, Cd and Pb in mussels were investigated at different temperatures (6-26 degrees C). Results from exposure of isolated gills showed a positive relationship between temperature and metal uptake. But in whole organism experiments, only the accumulations of non-essential metals (Cd, Pb) showed a similar trend while the two essential metals Co and Cu were independent and inversely related to temperature, respectively. With exception of Cu, elimination process appeared to be independent of temperature. The study also showed that neither changes in scope for growth (SFG) of mussels nor chemical speciation could fully account for the observed temperature-effects. Overall, these results suggest that fundamentally (i.e. at epithelial membranes), temperature-effects on uptake are largely due to changes in solution chemistry and physical kinetics, which favours higher uptake at high temperature. But at whole organism level, complex physiological responses appears to mask the relationship, particularly for biologically essential metals like copper.     

Vertical physicochemical parameter distributions and health risk assessment for trace metals in water columns in eastern Lake Tanganyika,Tanzania

The vertical distributions of trace metals and physicochemical parameters in water columns in Kigoma Bay and Kungwe Bay in eastern Lake Tanganyika, Tanzania, were studied. The Al, Ba, Ca, Co,K, Mg, Mn, Mo, Na, Sn, Sr, and V concentrations were low and varied very little with depth. The toxic heavy metal(As, Cr, Cu, Ni, Pb, and Zn) concentrations were relatively high in the surface water, and the Cu, Ni, Pb, and Zn concentrations decreased with depth. Principal component and cluster analyses indicated that the metals in the lake had three main sources. Al, Ba, Ca, Co, Cu, Cr, Mn, Sr, Sn, and V were found to be geogenic; As, Cr, Cu, Mo, Ni, Pb, Sn and Zn anthropogenic; and As, Ca, Co, Mg, and Na biogenic.Human health risk assessments were performed, and it was found that trace metals in the water at most of the sampling sites would cause no potential adverse ef fects or non-carcinogenic health risks through dermal contact or ingestion. However, trace metals in surface water in Kungwe Bay could have certain adverse ef fects on human health through the ingestion pathway(the total hazard quotient for ingestion(ΣHQi ng)was 1.75(a value >1 was de?ned as possibly indicating adverse ef fects). The Pb HQi ng for surface water in Kungwe Bay was 1.50 and contributed >80% of the ΣHQ_(ing_, implying that Pb pollution is a water quality and safety problem that needs to be carefully monitored and the potential sources identi?ed.