Effect of pH and calcium on lead and cadmium uptake by earthworms in water

pH and calcium are important as factors determining heavy metal bioavailability to soil organisms. To study their intrinsic effect without the influence of soil adsorption, earthworms (Lumbricus rubellus) were exposed to lead and cadmium in reconstituted water adjusted to various levels of pH and calcium chloride. Concentration of cadmium in worms increased linearly with increasing concentration of exposure independent of pH. Concentration of Pb in worms, however, showed a pH-dependent increase with increasing concentration of exposure. The uptake of both metals was positively influenced by increasing pH. Calcium reduced the uptake of Cd, but had no significant effect on Pb uptake. It is suggested that Ca2+ and H+ compete with lead and cadmium ions for binding sites in the earthworm, and that the affinity for Pb is much greater than that for Cd. The results are discussed in relation to available data on Pb and Cd accumulation by earthworms in soil, showing the predominant importance of soil adsorption processes.     

Heavy Metals Alter the Survival, Growth, Metamorphosis, and Antipredatory Behavior of Columbia Spotted Frog (Rana luteiventris) Tadpoles

Amphibian populations appear to be declining around the world. Although there is no single cause, one factor may be pollution from heavy metals. As a result of mining in the Silver Valley of Idaho, heavy metals have been released into habitats containing many species of sensitive organisms, including spotted frogs (Rana luteiventris). While the gross extent of pollution has been well documented, the more subtle behavioral effects of heavy metals such as lead, zinc, and cadmium are less well studied. We tested the effects of heavy metals on the short-term survival (LC₅₀) of spotted frog tadpoles. Compared to single metals, metals presented together were toxic at lower doses. We also raised the tadpoles in outdoor mini-ecosystems containing either a single heavy metal or soil from an EPA Superfund site in the Silver Valley known to be composed of numerous heavy metals. Exposure to Silver Valley soil resulted in delayed metamorphosis. We tested the ability of metal-exposed tadpoles to detect and respond to chemical cues emanating from predacious rainbow trout. We found that high levels of Silver Valley soil, medium levels of zinc, and medium and high levels of lead resulted in a decreased fright response. Low levels of cadmium, zinc, and lead did not cause a significant effect, but low levels of soil did result in a decreased fright response. Heavy metals may alter interactions between tadpoles and their predators. Received: 9 October 1997/Accepted: 25 March 1998     

Adaptation to soil pollution by cadmium excretion in natural populations of Orchesella cincta (L.) (Collembola)

Population differentiation in Orchesella cincta (L.) (Collembola) populations, from various heavy metal contaminated sites, was studied by comparing cadmium excretion efficiency in first generation (F₁) laboratory individuals. Animals from sites with high metal concentrations in the litter and with a long history of contamination showed significantly higher excretion efficiencies than animals from low pollution, or reference sites. Differences found in the F₁ laboratory animals suggest evidence for genetic differences between the populations.Beneficial and detrimental effects of cadmium excretion were studied in relation to body growth and cadmium concentrations. In chronically exposed animals from an unpolluted site, no physiological acclimation was observed. Excretion efficiency was negatively correlated with body concentrations of cadmium. No detrimental effects were found.Whole-body equilibrium concentrations of cadmium and lead were similar in F₁ animals from the reference site and polluted sites. Significant differences in excretion efficiencies imply that the distribution of toxic metals over body compartments differs, tolerant populations having a higher proportion deposited in the gut. Body concentrations of zinc were consistently higher in animals from the polluted site, during both cadmium and zinc exposure. No detrimental effects of increased cadmium excretion on body concentrations of zinc were observed. Population comparisons of cadmium excretion efficiency data and growth reduction in F₁ laboratory animals showed that both parameters were inversely related. Cadmium and lead contamination were not the sole factors determining tolerance differentiation.     

Phytoextraction Potential of <Emphasis Type="Italic">Prosopis juliflora</Emphasis> (Sw.) DC. with Specific Reference to Lead and Cadmium

Root and shoot samples of Prosopis juliflora were assessed for their heavy metal content to evaluate the species as a green solution to decontaminate soils contaminated with lead and cadmium. The highest uptake of both the metals was observed in plants from industrial sites. Sites with more anthropogenic disturbance exhibited reduced chlorophyll levels, stunted growth, delayed and shortened reproductive phase. The ratios of lead and cadmium in leaves to lead and cadmium in soil were in the range of 0.62–1.46 and 0.55–1.71, respectively. Strong correlation between the degree of contamination and concentrations of lead and cadmium in plant samples identifies P. juliflora as an effective heavy metal remediator coupled with environmental stress.     

Comparison of the Solubilizing Efficiencies of Some pH Lowering (Sulphur and (NH4)2SO4) Amendments on Cd and Zn Mobility in Soils

The use of conventional methods to clean up the soil is very expensive and destructive to the ecosystem. The concept of phytoextraction has been introduced to safely manage soils contaminated with heavy metals. However, using plants to remediate polluted soils is a lengthy process. This has necessitated the use of amendments to potentially enhance solubilization of metals in order to increase their bioavailability in the soil solution. A pot experiment was conducted to study the effect of some selected pH lowering amendments [elemental sulphur and (NH₄)₂SO₄] on the solubility and availability of Cd and Zn. The application of these amendments resulted in a decrease in the pH of the soil. The decrease in pH significantly enhanced the solubilization and the mobility of Cd and Zn into the soil solution. The CaCl₂ extraction protocol was employed to study the effects of the various amendments on the mobility of Cd and Zn.     

Accumulation and Elimination of Trace Metals in a Transplantation Experiment with Crassostrea rhizophorae

Oysters, Crassostrea rhizophorae, were reciprocally transplanted to two different sites: a contaminated site in the Cotegipe Channel at Aratu Bay and an uncontaminated site at Cacha-Prego, inside and outside of Todos os Santos Bay (Brazil), respectively. Trace metal accumulation was measured after 0, 15, 30, and 60 days of exposure at the contaminated site. Oysters transplanted for 60 days from the clean to the contaminated site had accumulated cadmium and lead to similar concentrations as found in the native oysters. They had also accumulated copper and zinc, but to lower levels compared to native specimens. Elimination experiments were carried out by transplanting oysters in the reverse direction. After 30 days, concentrations of cadmium and lead had decreased to levels comparable to those in the native specimen, whereas concentrations of copper and zinc did not diminish. A second elimination experiment, bringing back to Cacha-Prego oysters that had been exposed 60 days at Cotegipe Channel, indicated stronger decreases of copper and lead, but no clear changes of cadmium and zinc concentrations. The accumulation experiment with C. rhizophorae is useful to estimate trace metal bioavailability and changes in concentrations as a function of time at the contaminated site. The different results of elimination experiments in the uncontaminated site suggest different degrees of trace metal fixation after long-term and short-term accumulation periods. Received: 1 July 1998/Accepted: 12 May 1999     

Zinc,Cadmium and Lead Accumulation and Characteristics of Rhizosphere Microbial Population Associated with Hyperaccumulator <Emphasis Type="Italic">Sedum Alfredii</Emphasis> Hance Under Natural Conditions

A field survey was conducted to study the characteristics of zinc, cadmium, and lead accumulation and rhizosphere microbial population associated with hyperaccumulator Sedum alfredii Hance growing natively on an old lead/zinc mining site. We found significant hyperaccumulation of zinc and cadmium in field samples of S. alfredii, with maximal shoot concentrations of 9.10–19.61 g kg⁻¹ zinc and 0.12–1.23 g kg⁻¹ cadmium, shoot/root ratios ranging from 1.75 to 3.19 (average 2.54) for zinc, 3.36 to 4.43 (average 3.85) for cadmium, shoot bioaccumulation factors of zinc and cadmium being 1.46–4.84 and 7.35–17.41, respectively. While most of lead was retained in roots, thus indicating exclusion as a tolerance strategy for lead. Compared to the non-rhizosphere soil, organic matter and total nitrogen and phosphorus content, CEC and water extractable zinc, cadmium, and lead concentration were significantly higher, but pH was smaller in rhizosphere soil. The rhizosphere soil of S. alfredii harbored a wide variety of microorganism. In general, significantly higher numbers of culturable bacteria, actinomycetes, and fungi were found in the rhizosphere compared to bulk soil, confirming the stimulatory effect of the S. alfredii rhizosphere on microbial growth and proliferation. Analyses of BIOLOG data also showed that the growth of S. alfredii resulted in observable changes in BIOLOG metabolic profiles, utilization ability of different carbon substrates of microbial communities in the rhizosphere soil were also higher than the non-rhizosphere, confirming a functional effect of the rhizosphere of S. alfredii on bacterial population.     

Biological and Chemical Characterization of Metal Bioavailability in Sediments from Lake Roosevelt,Columbia River,Washington, USA

We studied the bioavailability and toxicity of copper, zinc, arsenic, cadmium, and lead in sediments from Lake Roosevelt (LR), a reservoir on the Columbia River in Washington, USA that receives inputs of metals from an upstream smelter facility. We characterized chronic sediment toxicity, metal bioaccumulation, and metal concentrations in sediment and pore water from eight study sites: one site upstream in the Columbia River, six sites in the reservoir, and a reference site in an uncontaminated tributary. Total recoverable metal concentrations in LR sediments generally decreased from upstream to downstream in the study area, but sediments from two sites in the reservoir had metal concentrations much lower than adjacent reservoir sites and similar to the reference site, apparently due to erosion of uncontaminated bank soils. Concentrations of acid-volatile sulfide in LR sediments were too low to provide strong controls on metal bioavailability, and selective sediment extractions indicated that metals in most LR sediments were primarily associated with iron and manganese oxides. Oligochaetes (Lumbriculus variegatus) accumulated greatest concentrations of copper from the river sediment, and greatest concentrations of arsenic, cadmium, and lead from reservoir sediments. Chronic toxic effects on amphipods (Hyalella azteca; reduced survival) and midge larvae (Chironomus dilutus; reduced growth) in whole-sediment exposures were generally consistent with predictions of metal toxicity based on empirical and equilibrium partitioning-based sediment quality guidelines. Elevated metal concentrations in pore waters of some LR sediments suggested that metals released from iron and manganese oxides under anoxic conditions contributed to metal bioaccumulation and toxicity. Results of both chemical and biological assays indicate that metals in sediments from both riverine and reservoir habitats of Lake Roosevelt are available to benthic invertebrates. These findings will be used as part of an ongoing ecological risk assessment to determine remedial actions for contaminated sediments in Lake Roosevelt.     

Effect of Cd or Pb Addition to Cu-Contaminated Soil on Tissue Cu Accumulation in the Earthworm,Dendrobaena veneta

Generally, soil heavy metal contamination consists of a mixture of heavy metals. Soil chemical properties and interaction with other pollutants in soil affect the external heavy metal bioavailability. Moreover, interaction with other pollutants accumulated in organisms may change the toxicity of each pollutant. Therefore, the hypotheses was tested that addition of Cd or Pb to Cu-contaminated soil would lead to an increase in tissue Cu accumulation in the earthworm,Dendrobaena veneta,caused by (i) induction of metallothionein by Cd, or (ii) an increase in Cu concentration in soil solution due to the exchange of adsorbed Cu for Pb. Tissue heavy metal concentrations were determined after exposure in contaminated soils for 3 or 21 days. Considerable amounts of Cu, Cd, and Pb were accumulated, indicating that these heavy metals were available for uptake byD. veneta.Both Cd and Pb, however, did not significantly affect tissue Cu accumulation.     

Toxicity Assessment of Two Soils from Jales Mine (Portugal) Using Plants: Growth and Biochemical Parameters

Contaminants in soils can enter food chains through primary producers. Bioavailable contaminants can induce growth, and reproductive or biochemical changes in plants. To evaluate the bioavailability of heavy metals in two soils from Jales mine surroundings, bioassays with the plants Brassica rapa (RCBr) and Avena sativa were performed. Biochemical parameters (protein and malondialdehyde [MDA] content, and catalase and peroxidase activities) were also measured. The soils had different heavy metal contents: JNC soil contained low heavy metal concentrations, whereas JC soil had high heavy metal contents. Results stressed the difference between species sensitivity, with A. sativa showing no toxicity effects when exposed to both soils. On the other hand, B. rapa presented a decrease in growth parameters when exposed to JNC soil and no changes when exposed to JC soil. A Life Cycle Bioassay confirmed this trend for B. rapa exposed to JNC soil, but also evidenced that JC soil was affecting B. rapa in terms of flower and seed pod production. Biochemical assays showed that plants affected by heavy metals also displayed oxidative stress, with an increase in MDA production, reduction of protein content, and reduction of catalase and peroxidase activities. All bioassays revealed that JNC soil, although with a lower heavy metal content, had a higher bioavailable fraction when compared to JC soil, which consequently increased its toxicity to plants.     

Cadmium and Lead Accumulation in Three Endogeic Earthworm Species

The objective of this study was to assess the capability of earthworms from the same ecological group as heavy metal bioindicators. Three earthworm species from the endogeic group were studied: Aporrectodea caliginosa (Savigny, 1826), Perelia kaznakovi (Michaelsen, 1910) and Octolasion lacteum (Örley, 1885). Their accumulation of the heavy metals lead (Pb) and cadmium (Cd) were studied from three stations in Tehran province, Iran. O. lacteum was used to compare metal accumulations in two sites located next to a highway. A. caliginosa and P. kaznakovi were used at a third site located near the edge of a sewage system to compare metal accumulations between the two endogeic species in this area. At both locations, the concentrations of Cd and Pb in earthworms were higher than in the surrounding soil. The results of the study revealed that P. kaznakovi and A. caliginosa were better bioindicators for Pb, but O. lacteum was a better bioindicator for Cd. These earthworms can therefore be used as Cd and Pb bioindicators in environmental assessment.     

Concentrations of heavy metals associated with urban runoff in fish living in stormwater treatment ponds

Redear sunfish (Lepomis microlophus), largemouth bass (Micropterus salmoides), and bluegill sunfish (Lepomis macrochirus) were collected from stormwater ponds and natural lakes and ponds (controls) in Orlando, Florida and analyzed for cadmium, nickel, copper, lead, and zinc in order to determine: (1) if fish that live in stormwater treatment ponds contained significant heavy metal concentrations and (2) if there were differences in heavy metal concentrations between species with different foraging strategies. Redear sunfish from stormwater ponds contained significantly higher (p<0.005) concentrations of cadmium, nickel, copper, lead, and zinc than redear from controls. Largemouth bass collected from stormwater ponds contained significantly higher (p<0.005) concentrations of cadmium and zinc than those from control sites. Bluegill from stormwater ponds contained significant copper concentrations (p<0.005) as compared to bluegill from control sites.     

Can Excrement and Feathers of Nestling Songbirds Be Used as Biomonitors for Heavy Metal Pollution?

Although birds have been frequently used as indicators of heavy metal pollution, few studies have examined pollutant levels in nestling passerines. In this paper we determined the levels of two essential (zinc and copper) and three nonessential heavy metals (lead, cadmium, and arsenic) in the excrement and feathers of great (Parus major) and blue tit (Parus caeruleus) nestlings at a polluted site (near a metallurgic factory) and a reference site (4 km farther east). The excrement of both great and blue tit nestlings contained significantly higher concentrations of arsenic, cadmium, copper, and lead at the polluted site. Zinc concentrations did not differ significantly between sites for both species. The feathers of great and blue tit nestlings accumulated significantly higher concentrations of lead at the polluted site than at the reference site. Zinc levels in the feathers of great tit nestlings were significantly higher at the reference site than at the polluted site. For all other elements considered, concentrations did not differ significantly between the two sites. There were no interspecific differences in metal levels between great and blue tits in both excrement and feathers. There was a significant positive correlation between the lead concentration in the excrement and feathers for both great and blue tits. We therefore conclude that excrement of great and blue tit nestlings can be used as a biomonitor for heavy metals (lead, cadmium, arsenic, and copper), whereas feathers appear only to be suitable as a biomonitor for lead pollution. Received: 21 March 2000/Accepted: 9 July 2000     

Bioavailability of Copper and Zinc in Mining Soils

The soil-contact exposure pathway can be the main driver of ecological risk assessments. There is currently no standard method to measure bioavailability of metals in soil to ecological receptors, yet the influence of metal bioavailability on toxicity has been known for decades and is a major factor influencing risk to ecological receptors. Bioavailability is to a large degree governed by varying soil characteristics within and among sites, yet ecological screening benchmarks are often derived on a total-concentration basis. We compared a calcium chloride (CaCl₂) extraction, cyclodextrin extraction, simulated earthworm gut (SEG) test, earthworm kinetic bioaccumulation test, and metal residues in plant tissues with a battery of invertebrate and toxicity tests using mining soils consisting of high organic-matter content cocontaminated with copper (Cu) and zinc (Zn). Earthworm (Eisenia andrei) tissue concentrations of Cu and Zn were regulated and were not predictive of invertebrate toxicity. All chemical measures of bioavailability correlated with several biological responses; however, CaCl₂-extractable Cu and SEG-extractable Cu and Zn best predicted effects to E. andrei. Total Cu concentrations in soil best correlated with effects to plants. Overall, a chemical measure was the best predictor of toxicity to each organism compared with biological measures, although the exact measure was dependent on organism and end point. Chemical-extraction techniques provide relatively quick, inexpensive indicators of essential metal bioavailability compared with biological measures; however, no single measure was indicative of all effects to all organisms.     

Copper, zinc, and cadmium concentrations in Peromyscus maniculatus sampled near an abandoned copper mine

Concentrations of zinc, copper, and cadmium were determined in soil and liver, kidney, bone and stomach contents of deer mice (Peromyscus maniculatus) from two sites near an abandoned mine and one control site, on Vancouver Island, British Columbia, Canada. Soil concentrations of copper were significantly elevated at the mine and off site vs the reference site. In contrast, there was no difference in soil cadmium and zinc concentrations between the mine and reference site. Concentrations of copper, cadmium and zinc in livers of mice from the mine site were significantly elevated relative to the reference and off site locations. Cadmium kidney concentrations tended to be greater in mice from the mine versus the off site and reference site. No differences in bone cadmium, copper and zinc and, kidney copper and zinc concentrations were noted among mice from the three locations. Diet of mice from mine and off sites contained significantly greater copper concentrations than the reference population; no differences in cadmium or zinc diet concentrations in mice from the three sites were noted. Comparison of ratios of metal concentrations in diet:soil and concentrations in liver:soil suggest that for zinc and copper, soil and diet are of equal importance as a source of metal contamination to these mice. In contrast, cadmium diet:soil and cadmium liver:soil ratios were much greater than one indicative of bioconcentration of cadmium from soil to diet and from soil to liver. For assessing routes of metal exposure, in this case for deer mice inhabiting an abandoned mine site, for copper and zinc, soil will most likely be indicative of exposure conditions. In contrast, concentrations of cadmium in diet will be more representative of amounts that the animal is potentially ingesting. Of further importance is that relative to reference sites, mice inhabiting an abandoned copper mine site have significantly elevated tissue levels of copper. This is turn will provide a route of metal exposure to canivorous birds such as owls and hawks. The toxicological significance of this exposure to birds of prey has yet to be assessed adequately.     

Enhanced Phytoextraction for Co-contaminated Soil with Cd and Pb by Ryegrass (Lolium perenne L.)

A pot experiment was conducted to investigate the effect of three additives – citric acid (CA), polyaspartic acid (PASP), and FeCl₃ – on the phytoextraction efficiency of cadmium (Cd) and lead (Pb) by ryegrass (Lolium perenneL.) from artificially contaminated soils with different heavy metal concentrations. The results showed that as the concentration of pollutants increased, the TI (tolerance index) and BCF (bio-concentration factor) of ryegrass gradually increased only when FeCl₃ was applied. FeCl₃ also exhibited the most significant biomass enhancement and heavy metal accumulation of ryegrass, as well as the highest phytoextraction efficiency in heavily-polluted soils. The overall orders of the optimal phytoextraction efficiency for the three additives in terms of their MER (metal extraction ratio) were: FeCl₃ > PASP > CA. Therefore, FeCl₃ can be used to improve the Cd and Pb phytoextraction efficiency of ryegrass in heavily-polluted soils.

     

Evaluation of different phosphate amendments on availability of metals in contaminated soil

A pot trial was conducted to assess the efficiency of P-induced metal immobilization in soils. Natural hydroxyapatite (HA), phosphate rock (PR), triple-superphosphate (TSP), and diammonium phosphate (DAP) were evaluated for their ability to reduce cadmium (Cd), lead (Pb), and zinc (Zn) bioavailability in an artificially metal-contaminated soil with three addition levels: T0 (without metals added), T1 (Cd/Pb/Zn:0.6/100/66 mgkg(-1)), and T2 (Cd/Pb/Zn: 1.5/300/200 mgkg(-1)). Phosphate compounds were applied at 2500 mg P(2)O(5) kg(-1) soil for each metal level with five treatments: CK (control), TSP, DAP, PR, and HA, respectively. The immobilization and bioavailability of Cd, Pb, and Zn were determined by plant (Brassica campestris L.) uptake, scanning electron microscope (SEM), and sequential extraction. The results showed that HA was superior to all other materials for reducing Pb, Zn, and Cd uptake in shoot with reductions of 34.6-53.3% for Pb, 31.2-47.3% for Zn, and 39.1-42.4% for Cd, respectively, as compared with the control treatment. The mechanisms of Pb immobilization in the soil and the decreased Pb translocation from the plant root to shoot induced by added phosphate were identified with scanning electron microscope (SEM) equipped with energy dispersive X-ray elemental spectrometry (EDS). Sequential extraction results indicated that the phosphate amendments converted significant amounts of the soil Pb, Zn, and Cd from exchangeable (EX), organic bound (OC), carbonate bound (CB), amorphous Fe and Al oxides-bound (OX) (non-residual (RES) fractions) to RES fraction. In general, the effect of different phosphates on plant uptake of Pb, Zn, and Cd followed the order: HA>PR>DAP>TSP. The results suggested that HA and PR amendments could significantly reduce the bioavailability and increase the geochemical stability of soil Pb, Zn, and Cd in contaminated soils.     

Bioavailability indices for uranium: Effect of concentration in eleven soils

Bioavailability indices have not been developed for uranium (U) in soils. Eleven soils, covering a broad range in soil properties, were treated to achieve U concentrations ranging from background to 10,000 mg U/kg dry soil. Uptake by radish and beans, accumulation by earthworms and extraction with two chemicals were investigated. The extraction efficiency of NaHCO₃ was very high and reflected total soil U levels rather than bioavailable soil U levels. The extraction efficiency of CH₃COONH₄ was lower and was well correlated to the concentration ratios for plants and earthworms. These latter three indices were all negatively correlated to soil cation exchange capacity and organic matter contents. These indices were not constant across soil U concentrations. In several soils, the bioavailability of U was at a minima in the range of 10 to 100 mg U/kg dry soil. The mechanism for this is not clear, but sublethal toxicity may be involved.     

The Effect of Tributyltin-Oxide on Earthworms, Springtails, and Plants in Artificial and Natural Soils

Chemical bioavailability in Organisation for Economic Co-operation and Development (OECD) artificial soil can contrast with bioavailability in natural soils and produce ecotoxicologic benchmarks that are not representative of species’ exposure conditions in the field. Initially, reproduction and growth of earthworm and Collembolan species, and early seedling growth of a dicotyledonous plant species, in nine natural soils (with a wide range of physicochemical properties) and in OECD soil were evaluated. Soils that supported reproduction and growth of the test species were then used to investigate the toxicity of tributyltin-oxide (TBT-O). Natural soils caused greater toxicity of TBT-O to earthworms (EC₅₀ values varied from 0.5 to 4.7 mg/kg soil dry weight [dw]) compared with toxicity in OECD soil (EC₅₀ = 13.4 mg/kg dw). Collembolans were less sensitive to TBT-O than earthworms in natural soils, with EC₅₀ values ranging from 23.4 to 177.8 mg/kg dw. In contrast, the toxicity of TBT-O to collembolans in OECD soil (EC₅₀ = 104.0 mg/kg dw) was within the range of EC₅₀ values in natural soils. Phytotoxicity tests revealed even greater difference between the effects in natural soils (EC₅₀ values ranged from 10.7 to 189.2 mg/kg dw) and in OECD soil (EC₅₀ = 535.5 mg/kg dw) compared with results of the earthworm tests. Studies also showed that EC₅₀ values were a more robust end point compared with EC₁₀ values based on comparisons of coefficients of variation. These results show that toxicity testing should include studies with natural soils in addition to OECD soil to better reflect exposure conditions in the field.     

Elemental Composition and Sources of Fine Particulate Matter (PM2.5) in Delhi,India

It is essential to understand the occurrence from and plant bioavailability of soil microplastics to heavy metals in soils to assess their environmental fate and risk. The purpose of this study was to evaluate the effect of different microplastic concentrations on the bioavailability of copper and zinc in soil. The relationship between the availability of heavy metals in soil assessed by chemical methods (soil fractionation) and the bioavailability of copper and zinc assessed by biological methods (accumulation in maize and cucumber leaves) in relation to the concentration of microplastics. The results showed that copper and zinc in soil shifted from stable to effective fraction with increasing polystyrene concentrations, which would increase the toxicity and bioavailability of heavy metals. When the concentration of polystyrene microplastics increased, copper and zinc accumulation in plants increased, chlorophyll a and chlorophyll b decreased, and malondialdehyde increased. It is shown that the addition of polystyrene microplastics promoted the toxicity of copper and zinc and inhibited plant growth.