Mogelijke risico’s van vislood in het aquatische milieu

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Stichting Gezond Water (SGW) approached the Science Shop of the WUR in 2020 with the question to investigate the risks of lost/released fishing lead to the aquatic environment. Since both professional and recreational fishing activities are very abundant in the Netherlands, and can occur on rather fixed locations lost lead accumulates locally. The use of fishing lead is officially subject to licensing under the Water Act, but this is not enforced by the responsible authorities. In 2021, the European body ECHA, as the authority responsible for regulating chemicals, submitted a proposal to phase out the use of lead in hunting and fishing. The aim is to reduce lead emissions to the environment and significantly reduce the risk of (direct and indirect) negative effects of lead on humans and ecosystems. The Commission will make a decision in 2023. -To delineate the interpretation of the experimental phase in this project on possible risks of fishing lead on the aquatic environment, literature research was conducted on the possible annual amount of fishing lead entering the environment via angling, measurements of concentrations of dissolved lead in Dutch surface water, and effect concentrations of lead in toxicity studies. Available data from various measurement sites show that the annual average throughout the Netherlands is below the environmental quality requirement (JG-MKE) of 1.2 µg/L free-dissolved lead, only sporadically has a measurement value above 1.2 µg/L been reported. In comparison, Dutch stormwater has an average lead concentration of 0.9 µg/L. Aquatic snails appear to be the most sensitive aquatic animals to dissolved lead, with a limit value of 12 μg/L below which no long-term effects are found. Moreover, lead toxicity appears to depend on certain water conditions, such as suspended solids in the water column, water hardness and pH. A previous experimental emission study with 4 lead pellets in sediment-water systems showed that lead concentrations above the JG-MKE can occur at neutral pH. The emission study with lead pellets was taken as a starting point for the experimental project phase. A dose-effect relationship was investigated with water snails, with 4 different densities of 3 mm split lead sinkers (0, 4, 20, 100 lead sinkers per jar containing 1 liter of water) both with and without a layer of 2 cm of fine sediment. After 4 weeks of lead incubation, snails were exposed for yet another 4 weeks. Dissolved lead concentrations (filtered over 45 μm) were also above the JG-MKE in the present experiment with 4 leads per liter of water in test systems without sediment, but no significant effect on mortality or growth on the (sub-)adult Physella acuta was detected. In test systems with sediment, most of the released lead was bound to sediment, but at 20 sinkers per liter of water in all replicates, dissolved lead concentrations were above the JG-MKE after 56 days. The water snail Physella acuta experienced no effects of lead on mortality, but compared to the control group, snail growth was significantly lower at 4 lead sinkers per jar of 1 liter of water. This corresponds to 108 cm2 of lead object per m2 of sediment surface area (1.1% of bottom surface area is lead). The emission rate of split lead on sediment was determined to be 3.1-3.8 mg/cm2/yr (0.26% of fish lead per year). The results of this laboratory study indicate that at the lowest density tested (lead sinkers covering 1.1% of bottom surface), lost sinkers on the water bottom surface in stagnant water pose an environmental risk. Lead densities in this study were well above those at typical fish sites (England, Wales, USA). Lead emission risks could be further tested on juvenile snails that experience greater growth than the sub-adult individuals currently used. The realistic risk to aquatic animals from dissolved lead released from sinkers in Dutch water systems is still difficult to estimate. For this, more insight is needed into, for example, the density of sinkers at popular fish sites, the extent to which sinkers stay at the sediment surface, the dilution factor (flow rate of water), the sedimentation rate of suspended solids (covering sinkers), and the influence of dredging. The area of lead objects at locations where there is a lot of recreational fishing activity seems not (yet) to be identified in the Netherlands, and should be further investigated in view of the decades-long lead backlog already present in the environment.
Original languageDutch
Place of PublicationWageningen
PublisherWetenschapswinkel Wageningen
Number of pages52
ISBN (Electronic)9789464476750
Publication statusPublished - May 2023

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NameRapport / Wageningen Wetenschapswinkel

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