Bioavailable EQS for Lead for European Surface Waters: DOC- and BLM-Based Approaches

Materials & Methods

Acknowledgement: Thanks to Stijn Baken, European Copper Institute for sharing monitoring datasets (original source: WCA and ARCHE).

Abstract: The current Environmental Quality Standard (EQS) for lead (Pb) under the Water Framework Directive (WFD) in the EU uses a bioavailability approach that

only takes account of dissolved organic carbon (DOC) to derive site-specific EQS for a freshwater ecosystem. While DOC is a major water chemistry factor to mitigate Pb

toxicity in freshwater, other parameters, specially water pH and calcium also have influence on Pb bioavailability. A chronic biotic ligand model (BLM) that accounts for

all of these factors were developed for Pb from a large array of ecotoxicological data and applied to derive EQS for selected European freshwater scenarios: Ditches (NL),

River Otter (UK), River Teme (UK), River Rhine (NL), River Ebro (ES), Lake Monate (IT), and neutral acidic lake (SE). The ranges of pH (6.7–8.2), DOC (2.5– 12.0 mg/L), and

Ca (8.7–60.1 mg/L) in these scenarios cover a wide range of water chemistry conditions to represent typical cases of bioavailability for European surface waters. Based

on the parametric best-fitting SSDs (species sensitivity distributions) that were normalized with the chronic BLM, the calculated 5th percentile hazardous concentrations

of Pb (i.e., ecological threshold concentrations or EQS protecting 95% of freshwater species) for the seven selected European freshwater scenarios were between 6.3 µg

Pb/L and 31.1 µg Pb/L. On the other hand, the EQSs calculated with the DOC equation used under the WFD vary between 3.0 µg Pb/L and 14.4 µg Pb/L for the same

scenarios. The reference EQS (1.2 µg Pb/L) that represents a situation of high bioavailability (DOC = 1 mg/L) and is currently used in the EU is significantly lower than

those for the above scenarios, highlighting the protectiveness of the current bioavailable EQS for Pb. This paper includes a comparative analysis of DOC- and BLM-based

approaches for a wider range of European surface waters.

DOC Tool: A single parameter equation accounting for DOC (dissolved organic carbon) effects in water and developed for the assessment of site-specific Pb

EQS under WFD (Water framework Directive) in the EU (www.wca-environment.com/models-and-downloads). This is currently the only legal method for assessing

bioavailable Pb EQS compliance under WFD.

EQSsite = EQSreference + (1.2 x (DOCsite – DOCreference)), where, EQSreference = 1.2 µg/L Pb and DOCreference = 1 mg/L.Required Input parameter: DOC; Output: Local (site-specific) EQS

Full Lead BLM: Lead biotic ligand model developed based on full consideration of lead chemistry and ecotoxicity data for freshwater (www.leadblm.com).

Required Input Parameters: Temperature, pH, DOC, Ca, Mg, Na, K, SO4, Cl, DIC; Output: bioavailability normalized SSD and Local HC5 for Pb

Biomet v4: User-friendly tool that runs as Excel spreadsheet (www.bio-met.net) developed for Cu, Ni, Zn & Pb based on full-BLMs. Version 4 includes lead.

Required Input Parameters: pH, DOC and Ca; Output: Local HC5, Bioavailable fraction (BioF), Bioavailable metal concentration, & Risk Characterization ratio (RCR)

PNEC-pro v6: User-friendly tool that runs as Excel spreadsheet developed by Deltares (www.pnec-pro.com) based on BLMs. Version 6 includes Cu, Ni, Zn & Pb.

Required Input Parameters: DOC (pH, Ca, Mg & Na are optional); Output: Local PNEC, RCR & Probability (P) for risk

M. Jasim Chowdhury1, Patrick Van Sprang2, and Frederik Verdonck2

1. International Lead Association (ILA), 2530 Meridian Parkway, Durham, NC 27713, USA; 2. ARCHE Consulting, Liefkensstraat 35d, 9032 Gent, BelgiumContact: chowdhury@ila-lead.org

Table 1: Lead EQS, HC5 or PNEC as estimated with DOC & BLM based tools for typical European freshwaters.

Fig. 1: Lead full BLM versus Biomet/PNEC-pro outputs for FOREGS datasets (Source: WCA, 2017)

European watertypes

DOC(mg/L)

pH Ca (Hardness)(mg/L)

DOC tool(µg/L Pb)

Full BLM(µg/L Pb)

Biomet(µg/L Pb)

PNEC-pro(µg/L Pb)

Lake Monate (IT) 2.5 7.7 13.6 (48) 3.0 8.1 6.2 8.1

River Otter (UK) 3.2 8.1 46.9 (165) 3.8 9.1 7.9 7.7

River Teme (UK) 8.0 7.6 50.1 (159) 9.6 17.3 19.9 19.5

River Rhine (NL) 2.8 7.8 68.9 (217) 3.4 6.3 6.4 5.5

River Ebro (ES) 3.7 8.2 72.9 (273) 4.5 7.0 6.7 7.4

Acidic lake (SE) 3.8 6.7 8.8 (28) 4.6 11.4 10.6 11.9

Ditch (NL) 12.0 6.9 60.1 (260) 14.4 31.1 22.8 29.0

Conclusions DOC is the major water chemistry factor to influence local lead EQS or PNEC in freshwater; water types with low pH and Ca (hardness) appear to be protective

Biomet predictions for local (site-specific) HC5 are comparable with those from chronic lead BLM for a wide range of water types in Europe

PNEC-pro also agrees with lead BLM for most of the water types, but in some cases it over predicts toxicity compared to other tools, with local PNECs being less than generic EQS.

The DOC correction tool generally yields local EQSs that are a factor of 2 lower than predictions from BLM based tools (with some exceptions for PNEC-pro).

The DOC based approach, which is currently used for assessing EQS compliance under WFD in the EU, is more stringent for protection but less scientifically robust relative to BLM

based approaches.

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Biomet (HC5) DOC tool (EQS) PNECpro (PNEC) Linear ()

Available DOC- and BLM-based tools to derive bioavailable EQS, HC5 or PNEC for lead

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Generic Pb EQSBioavailable = 1.2 µg/L

Predictions below generic EQS

Fig. 2: Local Pb EQS, HC5 or PNEC as estimated with user-friendly bioavailability tools for monitoring datasets from Austria, Belgium, Denmark, Germany, Netherlands, France, and UK (n = 542).

DOC(mg/L)

pH Ca(mg/

L)

DOC tool

(µg/L Pb)

PNEC-pro

(µg/L Pb)

2.1 8.4 72 2.5 3.5

1.8 8.4 93 2.1 1.4

1.8 8.0 117 2.2 0.2

2.1 8.0 124 2.5 0.5

1.4 7.8 98 1.6 0.3

1.6 8.1 95 1.9 0.9