Cd, Pb and Zn oral bioaccessibility in urban soils in the vicinity of two lead and zinc smelters

Transcription

1 Cd, Pb and Zn oral bioaccessibility in urban soils in the vicinity of two lead and zinc smelters Roussel H., Waterlot C., Pruvot C., Douay F. Laboratory of Soils and Environment, Institut Supérieur d Agriculture, 48 boulevard Vauban, Lille - France

2 Context Historic contamination Umicore (Auby) = Zinc smelter Metaleurop Nord (Noyelles-Godault) = Lead smelter

3 Context Pb isoconcentration curves (mg/kg) Agricultural topsoils

4 Context High contamination of urban soils used for recreational purposes or vegetables production.

5 Context METALEUROP (Pb smelter) UMICORE (Zn smelter) Ratio of Urban vs Regional agricultural topsoils Ag As Bi Cd Co Cr Cu Hg In Ni Pb Sb Se Sn Th Tl U Zn ME UM Ratio of Urban vs Local agricultural topsoils Ag As Bi Cd Co Cr Cu Hg In Ni Pb Sb Se Sn Th Tl U Zn ME UM (Douay et al. 2008)

6 Context Soil ingestion with hand to mouth transfer

7 Context Lead blood level (> 100 µg L -1 ) 10 to 15 % of children (2 to 4 years old, from 1994 to 2002) up to 30 % under the prevailing winds 2.4 % in 2004 after smelter closedown But the actual mean lead blood level is still over the national mean value (42 µg L -1 instead of 27 µg L -1 respectively) 7

8 Aims Evaluate Bioaccessibility of Cd, Pb and Zn in urban soils for human health risk assessment Differentiate bioaccessibility between smelters Understand the impact of soils physico-chemical chemical parameters Predict Bioaccessibility with multiple parameter equations

9 Materials and methods 27 urban topsoils were sampled 20 soils around Metaleurop Nord (ME) 7 soils around Umicore (U) 12 lawns and 15 kitchen gardens

10 Materials and methods Pooled (5 to 13 elementary samples) topsoil samples (0-25 cm) taken with a stainless steel auger. Total Cd, Pb, Zn concentrations, in vitro bioaccessibility tests, CEC, ph, Carbonates, Organic matter, etc.

11 Materials and methods Physico-chemical chemical parameters Mean SD Min Max Clay % Silt % Sand % ph Organic carbon g kg Total nitrogen g kg Total CaCO 3 g kg P 2 O 5 g kg CEC cmol+ kg

12 Materials and methods Physico-chemical chemical parameters Mean SD Min Max Total Cd mg kg Total Pb mg kg Total Zn mg kg

13 Materials and methods In vitro Bioaccessibility test (following BARGE UBM protocol) Filtration 27µm (Whatman n 41) Gastric extraction... Residual soil... Chyme Analysis AAS g soil Manual shaking 5-15 min ml Saliva ml Gastric juice (ph = 6.5+_ 0.5) ph = End-over-end rotation 1h00-37 C Gastro-intestinal extraction Centrifugation 3000 g - 5 min + 27 ml jus Duodenal + 9 ml Bile (ph = 6.3+_ 0.5)... End-over-end rotation 4h00-37 C... Centrifugation 3000 g - 5 min Residual soil... Chyme Filtration 27µm (Whatman n 41) Analysis AAS

14 Results Reference NIST 2710 Total (mg kg -1 ) (Ellickson et al., 2001) (Denys et al., 2007) (Oomen et al.,2004) This study Gastric Intestinal Gastric Intestinal Intestinal Gastric Intestinal Cd 21, ± ± 8.3 Pb ± ± ± 4 25 ± ± ± 2.5 Zn ± ± 1.2

15 Results Percentage of bioaccessible fraction of Cd, Pb and Zn expressed as a percentage of total concentration in soil. Gastric Gastro-intestinal Cd Pb Zn Cd Pb Zn Mean SD Min Max

16 Pb bioaccessible (mg/kg) Zn bioaccessible (mg/kg) Cd bioaccessible (mg/kg) Cd y = x R 2 = y = x R 2 = Pb Cd total (mg/kg) y = x R 2 = Results y = x R 2 = Zn Pb total (mg/kg) y = x R 2 = y = x R 2 = Zn total (mg/kg) No clear differences of bioaccessibility (related to total concentration) among smelters Umicore Metaleurop

17 Cd bioaccessible (mg kg - Pb bioaccessible (mg kg-1) Cd ) 5 y = x R 2 = Results y = x R 2 = Pb Gastric Gastro-intestinal Cd total (mg kg -1 ) y = 0.626x R 2 = y = x R 2 = Pb total (mg kg -1 ) R²=0.81 R²=0.89 Zn bioaccessible (mg kg-1) Relationships between bioaccessible Cd, Pb and Zn and total concentrations in soils. Zn y = x R 2 = y = x R 2 = Zn total (mg kg -1 ) R²=0.95

18 Results Relationship between predicted bioaccessible concentrations of Cd, Pb and Zn and soil parameters given by stepwise regression models. Cd Pb Zn Equation Bioacc Cd= 0.414*[Cdtot]-0.140*[CEC] *[CaCO 3 ]-0.45*[P 2 O 5 ]+1.77 Bioacc Pb=0.395*[Pbtot]-1.04*[CaCO 3 ] *[Ntot]-81.75*pH Bioacc Zn=0.412*[Zntot]-14.58*[Clay] *[P 2 O 5 ]-1.59*[CaCO 3 ] R² R²= P<0.001 R²=0.81 P<0.001 P<0.001 R²=0.95

19 Discussion Stepwise multiple regression showed that total concentration was positively correlated to bioaccessibility and P 2 O 5, CEC, Clay, ph or CaCO 3 where negatively related. HOWEVER... As shown by Denys and co- authors (2007) carbonates can be positively related with bioaccessibility (PbCO 3 ) Urban vs.. minig soils behave differently (Pb bioaccessibility between 40-84% and 10-60% in Caboche and co-authors presentation Wed a.m).

20 Conclusion Real importance of the source of contamination (speciation) and the receiving matrix (soil quality)

21 Thank you for your attention! Post Doctoral position available Oral bioavailability assessment of trace elements in soils and dust from an area heavily contaminated by a former lead smelter