Lead :: all ecosystems

Key Concerns

Effects of lead on plants include reductions in growth, photosynthesis, mitosis and water adsorption (Eisler 1989).

Ecosystem specific infromation

Arable habitats - these effects have been reported in various grasses and crops, including barley, ryegrass, clover, plantain, cress, mustard, and sunflowers exposed to solutions containing lead salts ranging from 0.005 to 2000 mg/l (WHO 1989). However, as lead has limited bioavailability in soil, effects are only likely to be found at very high lead concentrations. Plants growing in highly contaminated areas have often developed a tolerance to lead, although the degree of tolerance varies according to various factors, including lead concentration and the characteristics of the local plant populations (WHO 1989).

Bogs, wetland and heath -  elevated lead concentrations have been reported in soil sampled form a seasonal wetland situated to industrial sites. Concentrations were highest at sampling sites closest to the source, suggesting limited dispersion of lead (Perkins et al. 2000). The concentrations in arthropods and house mice (Mus musculusI) from the wetland were similar to those found at control sites, suggesting limited bioavailability of the lead (Torres and Johnson 2001).

Coastal and rocky habitat – lead has been reported to inhibit the growth of the marine diatom, Skeletonema costatum, with 100% and 50% in hibition reported at 0.01 and 0.005 mg/l, respectively. The No Effect Concentration was 0.00005 mg/l (Eisler 1989). LC50 values (for 48-96 hour exposures) reported for marine invertebrates range from 0.6 to >500 mg/l (Eisler 1989; WHO 1989). LC50 values reported for marine fish are also variable, ranging from 0.3 to 100 mg/l (Eisler 1989; WHO 1989). Evaluation of these data are difficult as the bioavailability of lead, (and its subsequent toxicity) will vary according to many factors including water hardness, pH, and the presence of anions and complexing agents. Organic lead compounds are generally 10 to 100 times more toxic to freshwater organisms than inorganic lead compounds. Organisms living in contaminated areas may demonstrate a tolerance to lead which is not found in organisms sampled from non-contaminated areas (WHO 1989).

Freshwater – there is little evidence of the effects of lead on aquatic plants at concentrations below 1 to 15 mg/l, especially in the presence of sediment, which reduces the bioavailability of lead (WHO 1989). LC50 values (for 48-96 hour exposures) reported for freshwater invertebrates range from 0.45 to >500 mg/l. LC50 values reported for freshwater fish are also variable, ranging from 1 to 100 mg/l. Evaluation of these data are difficult as the bioavailability of lead, (and its subsequent toxicity) will vary acc ording to many factors including water hardness, pH, and the presence of anions and complexing agents. Organic lead compounds are generally 10 to 100 times more toxic to freshwater organisms than inorganic lead compounds. Organisms living in contaminated areas may demonstrate a tolerance to lead which is not found in organisms sampled from non-contaminated areas (WHO 1989).

Grassland – increased concentrations of lead have been reported in the various species of woodlice sampled from a meadow situated beside a main road. The mean lead concentrations in woodlice from the meadow was 4.22 mg/kg dry weight, compared to 2.40 mg/kg dry weight reported in woodlice from a control (forest) area. The lead concentrations in the soil were also significantly different, with 43.32 mg/kg dry weight reported in soil from the meadow, compared to 34.60 mg/kg dry weight in the forest soil (Blanusa et al. 2002). The concentration of lead in grassland vegetation did not increase following a single application of sewage sludge, despite an increase in soil lead concentration (Wilkinson et al. 2003). The concentration of lead in lambs grazing on the grassland following the sludge application was generally low.

Woodland and hedgerow – increased concentrations of lead have been reported in the various species of woodlice sampled from a meadow situated beside a main road. The mean lead concentrations in woodlice from the meadow was 4.22 mg/kg dry weight, compared to 2.40 mg/kg dry weight reported in woodlice from a control (forest) area. The lead concentrations in the soil were also significantly different, with 43.32 mg/kg dry weight reported in soil from the meadow, compared to 34.60 mg/kg dry weight in the forest soil (Blanusa et al. 2002). The concentration of lead in grassland vegetation did not increase following a single application of sewage sludge, despite an increase in soil lead concentration (Wilkinson et al. 2003). The concentration of lead in lambs grazing on the grassland following the sludge application was generally low.

Additional Comments

Airborne lead tends to be deposited close to sources, such as smelters or roads, although 20% of the airborne-fraction can be dispersed widely, with lead a ccumulation reported at sites remote from anthropogenic activity (WHO 1989). Plants may acquire lead by surface deposition from rainfall, dust and soil (Eisler 1989). Inorganic lead has a tendency to form highly insoluble salts and complexes with various anions which bind tightly to soil, thus reducing the bioavailability to terrestrial plants via the roots (WHO 1989). Bioavailability is higher in acidic soils (Eisler 1989).