Lead pollution in subtropical ecosystems on the SE Gulf of California Coast: A study of concentrations and isotopic composition

• Published in: Marine environmental research 2008-10, Vol.66 (4), p.451-458
• Main Authors: Soto-Jiménez, Martin F., Páez-Osuna, Federico, Scelfo, Genine, Hibdon, Sharon, Franks, Rob, Aggarawl, Jugdeep, Flegal, A. Russell
• Format: Article
• Language: English
• Subjects: Animal, plant and microbial ecology; Animals; Applied ecology; Biological and medical sciences; Biological indicators; Brackish; Ecosystem; Ecotoxicology, biological effects of pollution; Environmental Monitoring; Eukaryota - chemistry; Fundamental and applied biological sciences. Psychology; Geologic Sediments - chemistry; Gulf of California; Isotopes - chemistry; Lead - analysis; Marine; Marine and brackish environment; Mexico; Pb pollution; Rhizophoraceae - chemistry; Seawater - chemistry; Sources and isotopic ratios; Water Pollutants, Chemical - analysis
• ISSN: 0141-1136; 1879-0291
• DOI: 10.1016/j.marenvres.2008.07.009

Lead pollution was investigated in environmental matrices and biological indicators collected from two typical subtropical coastal ecosystems in the southeast Gulf of California, Mexico. Lead concentrations and isotopic compositions ( 206Pb/ 207Pb and 208Pb/ 207Pb) were measured using high resolution inductively-coupled plasma-mass spectrometry (HR-ICP-MS) and thermal ionization mass spectrometry (TIMS), respectively. Lead in surface estuary sediments (10.0–34.2 μg g −1) and particulate Pb (25.0–128.7 μg g −1, >98% of total Pb) in the water column were significantly higher than levels in natural bedrock soils (15.1 ± 8.3 μg g −1) and river runoff (1.9 ± 1.4 μg g −1). Aquatic plants had Pb concentrations between 2.5 and 7.2 μg g −1, while those in macroalgae ranged from 3 to 5 μg g −1. The ranges of mean Pb concentrations in the aquatic animals studied (ranges in μg g −1) were as follows: zooplankton 32 ± 3, mussels 2.3–3.9, oysters 1.9–7.9, snail 2.0–7.7, barnacles 0.1–18.5, fish 1.4–8.9, crab 6.3–40.2 and polychaetae 8.5–16.7. Pb values in 20–40% of oyster and fish samples and in all samples of crab exceeded acceptable levels for a food source for human consumption. Pb isotope ratios 206Pb/ 207Pb, 208Pb/ 207Pb in biota ranged from 1.188 to 1.206 and 2.448 to 2.470, respectively. A plot of 206Pb/ 207Pb versus 208Pb/ 207Pb for the environmental and biological samples collected from two study areas indicates that they contain lead from ores mined in Mexico and used in the past to produce leaded gasoline in use until 1997, natural Pb weathered from the Sierra Madre Occidental mother rock, and the later influence of inputs from a more radiogenic source related to industrial activity in the United States. Statistical software IsoSource results revealed that the Pb contained in environmental matrices and biomonitors is mostly derived from gasoline (20–90%) and US emissions (10–40%).