Impact of marine traffic and dredging activities on resuspension and release of contaminants from sediments in the port of Antwerp Hanne Hetjens 1, Johannes Teuchies 1, Ronny Blust 1, Agnes Heylen 2 1 SPHERE, University of Antwerp, 2020 Antwerpen, Belgium 2 Port of Antwerp, Havenhuis, 2030 Antwerpen, Blegium Hanne.Hetjens@uantwerpen.be +32 (0) 32 65 35 32 1
The problem with sediment resuspension 2
The port of Antwerp - Located at the Scheldt estuary - Area of 12.068 hectares - Ma. water depth of ~18m - Highly industrialized area - Medium to bad water quality & (historically) polluted sediments (e.g. TBT, metals, PAHs )? - Intensive marine traffic (2014/2015 ~ 23.000 records) & maintenance dredging (vision 2020: ca 12.000.000 m 3 ) 3
Objectives 1. Evaluate the contribution of marine traffic and dredging activities on: - resuspension and transport of sediments and related contaminants 2. Characterize its impact on: - water quality and pollutant distribution within the port of Antwerp 4
What did we do? Field campaign -> 9 days on the boat (February April 2016) Peilboot ECHO IMDC Measurements: during resuspension events 5 - sediment concentrations, water velocity & salinity -> acoustic backscatter system: ADCP -> optical sensors: OBS-3A, SiltProfiler - water samples -> SPM concentrations -> Contaminants: TBT, PAH s, PCB s, Mineral Oil, Metals -> TOC, DOC Quantity, spatial and temporal distribution
Port of Antwerp right bank; 6.784 HA What did we do? Study area Dredging Pieter Coeke Bed levelling tug, Delwaidedok Dredging and dumping Sebastiano Caboto Trailing suction hopper dredger, Kanaaldok B1, AMORAS Departure Bow Firda, 4e Havendok Tanker: length 183 m, width 32 m, draught 10.5m Docking Marianne, 3e Havendok Tanker: length 97 m, width 16 m, draught 8.8 m 6 GoogleMaps 23 ship manoeuvres, 2 dredging campaigns
Results ADCP and Silt Profiler 7
Results 1. SPM Shipping Dredging d e 10 60 30 a b a c a Background concentration 8 p= 2.2e-16 *** Docking Departure Turning Passing TSHD dredging TSHD dumping BLT dredging X Other determining factors: TSH dredging & dumping > BLT dredging activities & shipping manoeuvres (p< 0.005) => strengths / direction of wind Docking & turning => use > of departure own propeller > passing (p< 0.005) => use of tug boats => activities of other vessels =>
Cd (µg/l) SPM (mg/l) TBT (µg/l) SPM (mg/l) Results 2. Contaminants PCBs -> concentrations below limit of quantification PAHs -> 3% of samples (pyrene) Metals and TBT Mineral oil -> 18% of the samples During resuspension Metals: Cd TBT 02 140 40 200 02 01 01 01 01 01 00 00 120 100 80 60 40 20 35 30 25 20 15 10 5 180 160 140 120 100 80 60 40 20 00 T=0 T=1 T=2 T=3 0 0 T=0 T=1 T=2 T=3 0 Cd tot Cd dis SPM TBT tot TBT dis SPM 9
Results 2. Contaminants: risk indicators Correlations: SPM <-> Total & Dissolved SPM <-> Particulate fractions ( => metals tot µg/l metals dis µg/l SPM (mg/l) SPM <-> LogKd ( => part (µg/kg) dis (µg/l) Particulate fractions <-> Dissolved fractions ) 1000 ) LogKd <-> Dissolved fractions 10
Results 2. Contaminants: risk indicators Metals: - total: - SPM - dissolved: - TBT: - total: - dissolved: LogKD 11
Cu (µg/l) Results 2. Contaminants correlations SPM <-> Copper (total and dissolved) 80 70 60 50 40 30 Total Dissolved 20 10 0 bc VLAREM standard 0 50 100 150 200 250 300 SPM (mg/l) 12
TBT logkd (L/Kg) Results 2. Contaminants correlations SPM <-> TBT Log Kd 10 9 8 7 6 5 4 3 2 1 0 0 50 100 150 200 250 SPM (mg/l) 13
Se dis (µg/l) Results 2. Contaminants correlations High eceedances of the WFD and VLAREM standards (>50%) by: - cadmium ; cobalt ; zinc ; arsenic & selenium (>30) - TBT 80 70 60 50 40 30 20 bc 10 0 0 50 100 150 200 250 300 SPM (mg/l) VLAREM standard higher than WFD, VLAREM standards -> ecotoicoligical risk 14
Pb predicted (µg/l) TBT predicted (µg/l) WFD standard Results 3. Contaminants: calculated <-> measured SPM (av.) during resuspension events contaminant conc. (av.) in the sediment (dock level) Metals: Lead 50 45 40 35 30 25 20 15 10 5 0 0 5 10 15 20 25 30 35 40 45 50 Pb measured (µg/l) TBT 0,3 0,25 0,2 0,15 0,1 0,05 0 0 0,05 0,1 0,15 0,2 0,25 0,3 TBT measured (µg/l) Measured < calculated 15
16 Conclusion and Discussion 1. SPM: TSH dredging highest effect on sediment resuspension followed by BLT dredging and shipping manoeuevres Highly variable factors important for resuspension intensity -> difficult to predict 2. Contaminants: Effects of sediment resuspension on contaminant concentrations in the water layer much smaller than epected -> overall eceedances of WFD and VLAREM standards system already under pressure -> surface water contamination not caused/worsened by sediment resuspension events -> even positive effects found 3. Calculated <-> measured: Often no correlation between contaminant and SPM concentrations in the water Measured concentrations mostly lower than calculated High variation in the dataset (e.g. SPM resuspension, KD values, calculated <-> measured etc.) predictions still highly comple and unsure
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Theoretical background 1. Ship propeller main and bow propeller - Diameter propeller - Capacity - Distance to sediment 2. Return current - Speed of ship - Ratio cross section ship/ water body - Distance to shore/quay wall 3. Waves 4. Ship Maneuvre - Passage - Docking - Departure - Turning Ji et al. 2014 18