A study of air pollution with heavy metals in Thessaloniki city (Greece) using trees as biological indicators

The air pollution of the city of Thessaloniki was studied, using park trees as biomonitors. The species analyzed were Ligustrum japonicum, Nerium oleander, Olea europea, Pinus brutia, Platanus orientalis, Populus alba, Populus nigra, and Robinia pseudoacacia. Acid digestion of leaf tissues and subsequent use of atomic absorption spectrometry was the analytical methodology used for the determination of heavy metals (Cu, Zn, and Pb). The concentration of heavy metals in the tree leaves depended on the metal species as well as on the position of the tree in the city. The mean concentrations of Cu ranged between 5 and 10 mg kg^–1 dry weight, of Zn between 19 and 85 mg kg^–1 DW and of Pb between <1.5 and 4.5 mg kg^–1 DW. In some cases, the effect of road junctions proved more significant than the traffic load for the contamination of leaves. Some differentiation was also observed between tree species. Old leaves collected during the fall were more contaminated than young leaves collected during the spring. The roughness of the outer surface leaves contributed to the trapping and retention of air particles. The results were compared with corresponding results from lichens and mosses which were also collected for a similar study.     

Variations of heavy metals and arsenic in fish and other organisms from the Calcasieu River and Lake,Louisiana

The edible parts of several species of fish and other marine organisms inhabiting the Calcasieu River/Lake, Louisiana were analyzed for Cd, Cr, Cu, Pb, Hg, Ag, Zn, and As. Concentrations of all metals measured in both intra and interspecies showed no significant variation with sample location. Differences in elemental concentrations were related to organism mobility and not to site-specific variations in metal loadings. Different species of finfish contained only trace amounts of Cd (0.02-0.08), Ag (<0.01–0.3), Pb (<0.2–0.5), and As (<0.1–0.3) mg kg^–1. Concentrations of Cu and Cr were highly variable, in contrast to Zn, which was present in relatively constant amounts across all species (28 ± 7 mg kg^–1). Sessile organisms such as oysters had the highest concentrations of heavy metals, including Cd. Periphyton and Zooplankton were the only groups that showed differences in metal concentrations with sampling location.     

Effects of oxygen concentrations on release of mercury from sediments and accumulation byCeratophyllum demersum andAnodonta grandis

The effects of different oxygen concentrations on the release of mercury from sediments and its subsequent accumulation by the plant,Ceratophyllum demersum, and the clam,Anodonta grandis, were investigated. Clams and plants were subjected to three treatments which were designated as control, treatment 1 and treatment 2. Two of the control replicates had normal oxygen concentrations (x=6.4–6.6 mg.L^–1) while the third had reduced concentration (x=1.8 mg.L^–1)- Oxygen concentrations in treatment 1 were reduced (¯x 1.3–2.0 mg.L^–1) for all three replicates. The three replicates in treatment 2 had normal oxygen concentrations (x=6.7–7.2 mg.L^–1). Mercury was added to the sediments in treatments 1 and 2. The resulting measured mean total mercury concentrations ((g.g^–1 dry weight) in the sediments of the replicates were 0.05–0.09 (controls), 4.42–7.28 (treatment 1) and 3.92–5.90 (treatment 2). The mercury concentration in water ranged between 0.10 g.L^–1 to 0.20 g.L^–1 for the six week period that the clams and plants were exposed to one of the three treatments. The total mercury concentrations in water were significantly lower in controls than in treatment 2. In plants, the mercury concentration was significantly higher in deoxygenated treatment 1 as compared to oxygenated treatment 2 and in controls. No significant difference in mercury concentration occurred between control and treatment 2 plants. Clams in treatments 1 and 2 contained significantly more mercury compared to the controls. Mercury concentrations in treatment 1 clams were also significantly higher than in treatment 2 clams. The mercury concentration in water, plants and clams was not significantly different in oxygenated and deoxygenated controls.     

Bioconcentration and Biomagnification of Mercury and Methylmercury in North Sea and Scheldt Estuary Fish

Total Hg and MMHg concentrations were assessed in more than 350 fish and shellfish samples. Hg concentrations in Greater North Sea fish of prey range from 0.039 mg kg^–1 wet weight (ww; for ray) to 0.61 mg kg^–1 ww (for dogfish) and for all other fish species, from 0.045 mg kg^–1 ww (for plaice) to 0.33 mg kg^–1 ww (for sand sole), with 95 ± 2% of the Hg content in the MMHg form. In Belgian coastal zone, fish concentrations range from 0.063 mg kg^–1 ww for plaice to 0.13 mg kg^–1 ww for flounder, with 82–87% of the Hg content in the MMHg form. In fish of the Scheldt, which is a very polluted estuary, Hg levels, as well as the percent MMHg of the total Hg, were lower than in the two zones previously mentioned. The intraspecies variability is of the order of 50% in each of the three zones. In liver tissue, a much larger variability was observed than in muscle tissue, except for fish species of the Scheldt. In most cases, the MMHg fraction in a particular fish species is inversely related to the intraspecies variability. Bioconcentration and biomagnification factors (BCF and BMF, respectively) were assessed. MMHg-BMFs were a few orders of magnitude higher than Hg(inorganic)-BMFs, and for the same species were always highest in the Greater North Sea and lowest in the Scheldt. For each of the Belgian coastal zone four species, a weak positive correlation between Hg content and fish length was found; however, the larger the size-range, the better the correlation.Taking fish length into account, a statistically significant difference in contamination level was observed for species sampled from the different geographical zones.     

Monitoring of Antifouling Booster Biocides in Water and Sedimentfrom the Port of Osaka, Japan

Concentrations of booster antifouling compounds in the port of Osaka, Japan were assessed. Concentrations of Sea-Nine 211 (4,5-dichloro-2-n-octyl-3-isothiazolone), thiabendazole (2-(4-thiazolyl)-benzimidazole), IPBC (3-iodo-2-propynyl butylcarbamate), Diuron (3,4-dichlorophenyl-N, N-dimethylurea), Irgarol 1051 (2-methylthio-4-t-butylamino-6-cyclopropylamino-s-triazine), and M1 (2-methylthio-4-t-butylamino-6-amino-s-triazine) in port water samples were in the range of <0.003–0.004 g L^–1, <0.0008–0.020 g L^–1, <0.0007–1.54 g L^–1, <0.0008–0.267 g L^–1, and <0.0019–0.167 g L^–1, respectively. IPBC was not detected in the water samples, but the concentration of Diuron was higher than any previously reported. The concentrations of Sea-Nine 211, thiabendazole, Diuron, Irgarol 1051, and M1 in sediment samples were in the range of <0.04–2.4 g kg^–1 dry, <0.08–1.2 g kg^–1 dry, <0.64–1350 g kg^–1 dry, <0.08–8.2 g kg^–1 dry, and <0.18–2.9 g kg^–1 dry, respectively. IPBC was again not detected. The levels of Sea-Nine 211, Diuron, and Irgarol 1051 in water and sediment samples were high in a poorly flushed mooring area for small and medium-hull vessels. Levels of Diuron and Irgarol 1051 were highest in summer. The concentration of Sea-Nine 211 in water increased between August and October 2002. Except for M1, increases in the levels of booster biocides in sediment were observed during the study period. The sediment–water partition (Kd) was calculated by dividing the concentrations in sediment by the concentrations in water. The Kd values for Sea-Nine 211, thiabendazole, Diuron, Irgarol 1051, and M1 were 690, 180, 2700, 300, and 870. The Kd value for these alternative compounds was lower than for TBT.     

Comparative Toxicity of Glyphosate-Based Herbicides: Aqueous and Sediment Porewater Exposures

Glyphosate-based herbicides are widely used for aquatic weed control. However, their aquatic toxicity data, especially those on sediment, are relatively scarce. In this study, the water-only acute toxicity of three formulations based on glyphosate (Rodeo, Roundup Biactive, and Roundup) were compared using a water-column organism (cladoceran: Ceriodaphnia dubia) and a benthic organism (amphipod: Hyalella azteca). In addition, Roundup Biactive and Roundup were spiked into a clean sediment which was amended with appropriate amounts of peat moss to study the effect of different organic carbon levels (0, 0.4, 1.2, and 2.1%) on their sediment toxicity, with C. dubia exposed to overlying water or porewater prepared from the contaminated sediments. Results showed that the toxicity based on 48-h LC50s for the three herbicides in the water-only tests was Roundup (1.5–5.7 mg L^-1) > Roundup Biactive (82–120 mg L^-1) > Rodeo (225–415 mg L^-1), and H. azteca was generally more sensitive than C. dubia to these herbicides. Toxicity differences between formulations were due to the different surfactant components in these herbicides. From the porewater toxicity tests, Roundup Biactive (340 mg kg^-1) and Roundup (244 mg kg^-1) were similarly toxic in the sediment tests at 0% organic carbon, indicating that the surfactants in Roundup were considerably more adsorptive than those in Roundup Biactive to the sediment of the same organic carbon. Also, an increase in organic carbon significantly decreased the toxicity of Roundup in sediment, but not for Roundup Biactive. Sediment–porewater partitioning of glyphosate was found to be influenced by sediment organic carbon (i.e., glyphosate adsorption increased with sediment organic carbon).     

A plant life-cycle bioassay for contaminated soil,with comparison to other bioassays: Mercury and zinc

Bioassays using rapid-cycling plants allow measurement of multiple endpoints and assessment of impacts on both growth and reproduction. Selections of Brassica rapa develop rapidly in a broad range of soils and are very consistent in production of flower and seed. Their sensitivity to variation in growth conditions was investigated to define the variables that most affect performance. Yield differences between soils were substantial, indicating the need for careful selection and use of control treatments. The sensitivity to contaminants was investigated with applications of mercury (Hg) and zinc (Zn) to three soils. In a sand soil, bloom initiation was slowed by <10 mg Hg kg^–1 soil and <50 mg Zn kg^–1 soil. In contrast, lettuce emergence and earthworm survival were less sensitive to these metals in this soil. Survival of Daphnia magna and the Microtox^® assay in soil extracts were more sensitive to Hg than bloom initiation, but less sensitive to Zn. A similar relationship among the bioassays was observed for two finer-textured soils, although for these, effects were usually apparent only at soil metal concentrations >200 mg kg^–1. Enzyme assays were included for comparison, but were not sensitive to Hg contamination. Rapid-cycling B. rapa selections are suitable for routine bioassays, and are representative of several widely distributed and utilized species.     

Natural and anthropogenic radioactivity levels and the associated radiation hazard in the soil of Oodalia Tea Estate in the hilly region of Fatickchari in Chittagong,Bangladesh

Radioactivity in the soil of a tea garden in the Fatickchari area in Chittagong, Bangladesh, was measured using a high-resolution HPGe detector. The soil samples were collected from depths of up to 20 cm beneath the soil surface. The activity concentrations of naturally occurring ²³⁸U and ²³²Th were observed to be in the range of 27 ± 7 to 53 ± 8 Bq kg⁻¹ and 36 ± 11 to 72 ± 11 Bq kg⁻¹, respectively. The activity concentration of ⁴⁰K ranged from 201 ± 78 to 672 ± 81 Bq kg⁻¹, and the highest activity of fallout ¹³⁷Cs observed was 10 ± 1 Bq kg⁻¹. The average activity concentration observed for ²³⁸U was 39 ± 8 Bq kg⁻¹, for ²³²Th was 57 ± 11 Bq kg⁻¹, for ⁴⁰K was 384 ± 79 Bq kg⁻¹ and for ¹³⁷Cs was 5 ± 0.5 Bq kg⁻¹. The radiological hazard parameters (representative level index, radium equivalent activity, outdoor and indoor dose rates, outdoor and indoor annual effective dose equivalents, and radiation hazard index) were calculated from the radioactivity in the soil.     

The effect of calcium on cadmium toxicity in the freshwater amphipod,Gammarus pulex (L.)

Adult intermoltGammarus pulex were exposed to a range of cadmium concentrations in an artificial stream water containing 20 mg calcium l^–1. 96 hr and 48 hr LC-50 values obtained were 0.12 and 0.68 mg Cd l^–1, respectively.The influence of external calcium level on cadmium toxicity was investigated at a cadmium concentration of 0.5 mg l^–1. Calcium had an antagonistic effect on cadmium toxicity, and at a calcium concentration of 200 mg l^–1 experimental animals failed to reach 50% mortality after a period of 120 hr. Over a 48 hr period of Cd uptake a solution containing 5 mg Cd l^–1, animals in 200 mg calcium l^–1 accumulated only half as much cadmium as animals in 20 mg calcium l^–1.Post-molt animals were very much more sensitive to cadmium than intermolt specimens. Exposure to 0.1 mg Cd l^–1 resulted in death in approximately 24 hr and the mean mortality time for animals in 0.01 mg Cd l^–1 was 45 hr. These data are likely to be explained in terms of competition between cadmium and calcium for binding sites associated with key physiological processes. The results place these animals among the most sensitive organisms yet studied with regard to cadmium toxicity, and emphasize the importance of the molt in assessing toxic effects on crustaceans.Contribution No. 1020, Center for Environmental and Estuarine Studies of the University of Maryland.     

Copper, Zinc and Lead Bioaccumulation in Marine Snail, Strombus gigas, from Guacanayabo Gulf, Cuba

Levels of copper, zinc and lead were determined in sediments and edible muscle of marine snail Strombus gigas collected from Guacanayabo Gulf, Cuba. The concentration range of each metal in marine snail muscle on mg kg⁻¹ wet weight varied as follows: Cu = 6.4–32.6, Zn = 20.4–31.1 and Pb = 0.2–2.3; and in corresponding sediments (on mg kg⁻¹ dry weight) as: Cu = 157–186, Zn = 56–94 and Pb = 20–37. The average biota-sediment accumulation factors (BSAFs) obtained for studied metals are less than unity in all cases, indicating that only a little fraction of metal content in the sediments is bioavailable, independently of their possible enrichments in the sediments. The concentrations of copper and lead in some of the marine snails are above typical public health recommended limits.     

Changes in metal speciation and pH in olive processing waste and sulphur-treated contaminated soil

Degradation of organic matter from olive mill waste and changes in the heavy metal fractionation of a metal-contaminated calcareous soil were studied in a laboratory experiment, in which the olive mill waste was mixed with the soil and then incubated under aerobic conditions. The soil was calcareous (15% CaCO₃) with high Zn and Pb concentrations (2058 and 2947 mg kg⁻¹, respectively). The organic amendment was applied at a rate equivalent to 20 g kg⁻¹ soil, and unamended soil was run as a control. To discern if changes in metal solubility were due to the acidic character of the waste, elemental sulphur was applied to soil as a non-organic acidifying material. The S⁰ rates used were 3.14, 4.71 and 6.28 g kg⁻¹. The mineralisation of total organic-C (TOC) from the waste reached 14.8% of the original TOC concentration after 56 days of incubation. The CO₂–C produced from S⁰-treated soils showed the carbonate destruction by the H₂SO₄ formed through S⁰ oxidation. The organic waste increased EDTA-extractable Zn and Pb concentrations and CaCl₂-extractable Mn levels in soil after two days of incubation. The changes in metal availability with time indicated that the oxidation of phenols from the waste reduced Mn (IV) oxides, releasing Zn and Pb associated with this mineral phase. Organic waste addition did not decrease soil pH; the acidifying effect of S⁰ did not change metal fractionation in the soil.     

Daily Dietary Selenium Intake in a High Selenium Area of Enshi,China

Enshi is a high selenium (Se) region in Hubei, China, where human selenosis was observed between 1958 and 1963. This study investigated the daily dietary Se intake of residents in Shadi, a town located 72 km northeast of Enshi City, to assess the risk of human selenosis in the high Se area. Foods consumed typically by the local residents and their hair samples were analyzed for total Se concentration. Concentrations of Se in different diet categories were as follows: cereals: 0.96 ± 0.90 mg kg⁻¹ DW in rice and 0.43 ± 0.55 mg kg⁻¹ DW in corn; tuber: 0.28 ± 0.56 mg kg⁻¹ in potato and 0.36 ± 0.12 mg kg⁻¹ in sweet potato; vegetables: ranging from 0.23 ± 1.00 mg kg⁻¹ in carrot to 1.57 ± 1.06 mg kg⁻¹ in kidney bean; animal proteins: 1.99 ± 1.11 mg kg⁻¹ in chicken and egg. Based on the food Se concentrations and the daily per-capita consumption, the estimated daily Se intake in Shadi was 550 ± 307 µg per capita. Moreover, the Se concentrations in the hairs of local adult residents were 3.13 ± 1.91 mg kg⁻¹ (n = 122) and 2.21 ± 1.14 mg kg⁻¹ (n = 122) for females and males, respectively, suggesting that females might be exposed to higher levels of Se from daily cooking. Although there was no human selenosis occurrence in recent years, the high level of the daily Se intake suggested that the potential risk of selenosis for local residents, especially females, might be a matter of concern.     

Exposure of urban applicators to carbaryl

Thirty-eight urban volunteers from the Lincoln and Omaha, Nebraska areas were monitored for carbaryl exposure during the summer of 1979. All volunteers were involved in the application of carbaryl incidental to their employment or leisure activities. The investigators made no attempt to affect the method of carbaryl application. The mean rates of carbaryl exposure were 3.85 and 0.26g cm^–2 hr^–1, respectively, for the outside of the clothing and the skin beneath the clothing; clothing apparently provided an effective barrier to carbaryl penetration. The rate of carbaryl exposure to the hands of applicators was 2.36 and 24.96g cm^–1 hr^–1, respectively, for applicators with and without gloves. The maximum dermal exposure recorded in this study was 2.86 mg kg^–1 hr^–1 which is significantly less than the stimated dermal LD₅₀ value for carbaryl (4000 mg kg^–1). The maximum air concentration of carbaryl was 0.28g L^–1, far less than the Threshold Limit Value of 5g L^–1. Only a small mean decrease was found in the applicators serum (–1.01%) or erythrocyte (–1.39%) acetylcholinesterase activity. Although some applicators had decreases in either serum or erythrocyte acetylcholinesterase activity greater than 20%, an equal number had increases of the same magnitude. The mean total carbaryl exposure to the applicators, expressed as a percent of toxic dose per hr, was 0.01%, with a maximum estimated exposure of 0.08%.Published with the permission of the Director of the Nebraska Agric. Exp. Sta. as Journal Article No. 6001. This research was funded as Grant No. 85-288-042-01 & 02 from the North Central Regional Pesticide Impact Assessment Program, USDA/SEA-CR.     

An Ecotoxicological Approach to Assessing the Impact of Tanning Industry Effluent on River Health

A study was conducted to investigate the sediment health and water quality of the River Sagana, Kenya, as impacted by the local tanning industry. Chemical analysis identified the main chemical pollutants (pentachlorophenols and chromium) while a bioassay addressed pollutant bioavailability. The bioassay, exploiting the luminescence response of a lux marked bacterial biosensor, was coupled to a dehydrogenase and Dapnia magna test to determine toxicity effects on sediments. Results highlighted the toxicity of the tannery effluent to the sediments at the point of discharge (64% of control bioluminescence) with gradual improvement downstream. There was a significant increase in dehydrogenase downstream, with the enzyme activity attaining a peak at 600 m, also indicating a gradual reduction of toxicity. Biological oxygen demand (19.56 mg L⁻¹) dissolved oxygen (3.97 mg L⁻¹) and high lethal dose value (85%) of D. magna also confirmed an initial stress at the point of discharge and recovery downstream. Optical density of surface water demonstrated an increase in suspended particulates and colour after the discharge point, eventually decreasing beyond 400 m. In conclusion, the study highlighted the importance of understanding the biogeochemistry of river systems impacted by industries discharging effluent into them and the invaluable role of a biosensor-based ecotoxicological approach to address effluent hazards, particularly in relation to river sediments.     

Translocation and Bioaccumulation of Metals in Oryza sativa and Zea mays Growing in Chromite-Asbestos Contaminated Agricultural Fields,Jharkhand, India

The present study involves the assessment of metals (Cr, Ni, Pb and Cd) in contaminated agricultural soil (CAS) and abandoned chromite-asbestos waste (CW). High concentrations of Cr and Ni were found in CW (1,121–2,802 mg Cr kg^?1; 985–1,720 mg Ni kg^?1), which CAS (1,058–1,242 mg Cr kg^?1; 1,002–1,295 mg Ni kg^?1). Zea mays and Oryza sativa showed significant amounts of metals in root and aerial parts. The primary factors only consider the changes in metal concentrations in soil and plant, while dynamic factor includes both changes in metal concentration and environmental processes. In spite of the high concentration of Cr present in contaminated soils and crops, significant translocation of metals (>1) were found only for Pb and Ni, when primary factor was used. When dynamic factor was used, higher translocation (>1) and bioaccumulation (>1) were found for Cr along with Pb and Ni. The current study concludes that assessment of metal toxicity in CAS and crops could be better evaluated by using both primary and dynamic factors.     

Protective effect and the therapeutic index of indralin in juvenile rhesus monkeys

The radioprotective effect of indralin in rhesus monkeys was examined over 60 d following gamma irradiation. Male and female rhesus macaques (Macaca mulatta) 2–3-years-old and weighing 2.1–3.5 kg were used. Animals were exposed to total-body gamma irradiation from ⁶⁰Co at a dose of 6.8 Gy (lethal dose, 100% lethality over 30 days). Indralin (40–120 mg kg^–1) was administered intramuscularly 5 min prior to radiation exposure. Indralin taken at a dose of 120 mg kg^–1 protected five out of six monkeys (compared with the radiation control group, in which all 10 animals died). The average effective dose of indralin in the monkeys exposed to gamma irradiation for 30 min was equal to 77.3 (63.3–94.3) mg kg^–1, and the maximum tolerated dose of indralin administered to monkeys was 800 mg kg^–1. Indralin reduced radiation-induced injuries in macaques, thus resulting in a less severe course of acute radiation syndrome. Delayed and less pronounced manifestation of the haemorrhagic syndrome of the disease, and milder forms of both leukopenia and anaemia were also noted. The therapeutic index for indralin, expressed as the ratio of the maximum tolerated dose to the average effective dose_, was equal to 10. Therefore, indralin has a significant radioprotective effect against radiation and has a high therapeutic index in rhesus monkeys.     

Transfer of nodularin to three-spined stickleback (Gasterosteus aculeatus L.), herring (Clupea harengus L.), and salmon (Salmo salar L.) in the northern Baltic Sea

Nodularin (NODLN) is a hepatotoxin produced by the cyanobacterium Nodularia spumigena, which occurs regularly in the Baltic Sea. The primary aim of this study was to study the transfer of NODLN to three-spined stickleback (Gasterosteus aculeatus L.), herring (Clupea harengus membras L.), and salmon (Salmo salar L.), which were caught from the northern Baltic Sea between August 2002 and August 2003. Liquid chromatography mass spectrometry (LC-MS) was used for NODLN analysis. NODLN was found in both herring (0–90 μg kg⁻¹ dw) and three-spined sticklebacks samples (2.8–700 μg kg⁻¹ dw). The recovery for the spiked stickleback samples in vitro was 28%. Only 1 salmon of a total of 10 contained a small amount of NODLN (10 μg kg⁻¹ dw). However, the high concentrations in individual stickleback suggest that possible transfer to higher trophic levels deserves more research.     

Heavy Metal Contamination of Arable Soil and Corn Plant in the Vicinity of a Zinc Smelting Factory and Stabilization by Liming

The heavy metal contamination in soils and cultivated corn plants affected by zinc smelting activities in the vicinity of a zinc smelting factory in Korea was studied. Soils and corn plants were sampled at the harvesting stage and analyzed for cadmium (Cd) and zinc (Zn) concentration, as well as Cd and Zn fraction and other chemical properties of soils. Cd and Zn were highly accumulated in the surface soils (0–20 cm), at levels higher than the Korean warning criteria (Cd, 1.5; Zn, 300 mg kg⁻¹), with corresponding mean values of 1.7 and 407 mg kg⁻¹, respectively, but these metals decreased significantly with increasing soil depth and distance from the factory, implying that contaminants may come from the factory through aerosol dynamics (Hong et al., Kor J Environ Agr 26(3):204–209, 2007a; Environ Contam Toxicol 52:496–502, 2007b) and not from geological sources. The leaf part had higher Cd and Zn concentrations, with values of 9.5 and 1733 mg kg⁻¹, compared to the stem (1.6 and 547 mg kg⁻¹) and grain (0.18 and 61 mg kg⁻¹) parts, respectively. Cd and Zn were higher in the oxidizable fraction, at 38.5% and 46.9% of the total Cd (2.6 mg kg⁻¹) and Zn (407 mg kg⁻¹), but the exchangeable + acidic fraction of Cd and Zn as the bioavailable phases was low, 0.2 and 50 mg kg⁻¹, respectively. To study the reduction of plant Cd and Zn uptake by liming, radish (Raphanus sativa L.) was cultivated in one representative field among the sites investigated, and Ca(OH)₂ was applied at rates of 0, 2, 4, and 8 mg ha⁻¹. Plant Cd and Zn concentrations and NH₄OAc extractable Cd and Zn concentrations of soil decreased significantly with increasing Ca(OH)₂ rate, since it markedly increases the cation exchange capacity of soil induced by increased pH. As a result, liming in this kind of soil could be an effective countermeasure in reducing the phytoextractability of Cd and Zn.     

Toxicity of heavy metals and salts to eurasian watermilfoil (Myriophyllum spicatum L.)

The toxicity of various heavy metals and salts to Eurasian watermilfoil (Myriophyllum spicatum L.) was determined under controlled growth conditions. Toxicants were added to water or to soil in systems with and without woods earth in the substrate.Fifty precent inhibition of root weight occurred with concentrations of 0.25 ppm Cu⁺², 1.9 ppm Cr₂O₇ ^–2, 3.4 ppm Hg⁺², 2.9 ppm AsO₂ ^–1, 7.4 ppm Cd⁺², 2.5 ppm Al⁺³, 9.9 ppm Cr⁺³, 41.2 ppm Ba⁺², 21.6 ppm Zn⁺², 13.3 ppm NH₄ ⁺¹, 22.4 ppm CN^–1, 143 ppm B₄O₇ ^–2, 363 ppm Pb⁺², 10,228 ppm Na₂SO₄, and 8,183 ppm NaCl. Soil increased toxicity of Cr⁺² and Ba⁺² but decreased toxicity of Cr₂O₇ ^–2, Cu⁺², Cd⁺², Al⁺³, and Hg⁺². In distilled water, CaCl₂ increased toxicity of Cr⁺³ but not Cr₂O₇ ^–2.For most toxicants there was a consistent relationship between inhibition of length and inhibition of weight and between inhibition of roots and inhibition of shoots. However, Cr₂O₇ ^–2 disproportionately decreased dry weight, and Hg⁺² and Na₂SO₄ disproportionately decreased stem length growth. With Cd⁺² and Cu⁺² stem length was greater relative to other measures of growth. Toxicity of Na₂SO₄ and NaCl was the same when concentrations were calculated as osmotic pressure but not when calculated as Na atoms or as total molecules/L.     

Toxicity and removal of heavy metals (cadmium, copper, and zinc) by Lemna gibba

Effects of cadmium, copper, and zinc on the aquatic plant Lemna gibba were determined under controlled conditions; in parallel their removal from the growth medium was followed. The results showed that the three heavy metals affected growth, a physiological stress index defined as the ratio of Chlorophyll to phaeophytin (D665/D665a), and the contents of proline. After 4 days, 10⁻³–10⁻¹ mg/L Cd inhibited growth by 25–100%, reduced D665/D665a by 35–89%, and increased proline content by 44–567%. Under the same conditions, 10⁻⁴–10⁻¹ μg/L Cu inhibited growth by 36–75%, reduced D665/D665a by 19–81%, and increased proline content by 67–288%. Comparable concentrations of Zn had little effect. However, higher concentrations (4, 30, and 50 mg/L) inhibited growth by 50–79%. Also, 0.1 and 30 mg/L induced a small reduction of D665/D665a (−3.8% and −22%) and an increase in proline contents (+144% and +177%). When it was observed, proline accumulation was always transient and the maximum was reached after 4 days. Monitoring metal concentration in the medium showed that L. gibba was able to remove metals from the medium. Zn and Cu removal was biphasic, it was rapid during the first 2 days (> 60% reduction) and slow (10–20%) during the following 8 days. For Cd, removal was linear and depended on the initial concentration. It reached approximately 90% after 6 or 8 days for initial concentrations of 10⁻¹ and 10⁻³ mg/L, respectively.