Summary of main results

Based on the primary results obtained by the models, it was concluded that:

• Over the past few decades, emissions of copper, zinc, lead and cadmium to air and water have decreased considerably. Today, the emissions of all four metals are very small compared to the flows through the economy. The inflow of these metals into the Dutch economy has remained at the same level. Instead of being emitted, these metals now accumulate in the Dutch economy in a number of stocks of products and in a number of closed loops connected, in particular, with agriculture.

• The accumulation does not cause risk levels to be transgressed at present. However, the authors claim that if the present management regime continues to be pursued, emissions will rise again in the future, owing to the increased stocks, causing transgression of human and ecosystem health standards, especially for copper and zinc.

• For copper, zinc and lead, a significant "back-flow" can be observed, indicating that a large fraction of the waste materials is recycled. For cadmium, this is not the case: waste materials either end up in landfills or are re-used as building and road construction materials containing cadmium as a trace contaminant.

• For lead, the problems can be expected to disappear owing to the penetration of lead-free gasoline since 1990.

• Surprisingly, cadmium concentrations appear to remain within the standard limits, both at present and in the steady-state situation.

• For copper and zinc, however, the authors do not find that there are any signs of these problems to be resolved in the future.

The main problem for copper and zinc was found to be related to agricultural soil and aquatic ecosystems. Under the present management regime, it was concluded that large-scale transgression of health standards may be expected roughly within a decade for aquatic ecosystems and within a century for agricultural soils. In addition, it was assumed that the quantity of metals entering the waste stage may pose a management problem: although recycling is a good option for many applications, processing large amounts of copper and zinc gives rise to a considerable volume of metal-containing waste-treatment residues which eventually leach into the environment. In the steady state, both waste generation and leaching of copper and zinc from landfill sites was found to be significantly greater than in the 1990 situation (van der Voet and van Oers, 2000).

Table 3.4. Origins of the immission of copper and zinc in surface waters in the Netherlands. S.S. stands for a steady-state scenario. After van der Voet and van Oers, 2000.

Origins

Cu (1990)

Cu (S.S)

Zn (1990)

Zn( S.S)

Total immission, t/y

570

1,050

2,78

3,580

Transboundary inflow

68%

37%

73%

56%

Effluent, sewage treatment

12%

21%

5%

4%

Anti-fouling treatment

9%

5%

-

-

Corrosion from building materials

-

-

10%

24%

Industrial emissions

3%

3%

4%

3%

Dissipative applications

2%

17%

3%

2%

Atmospheric deposition

2%

1%

2%

2%

Runoff from soils

3%

16%

3%

8%

Runoff from landfill sites

-

"very high"

-

"very high

For aquatic ecosystems, the main source of both copper and zinc pollution is the transboundary inflow via the rivers Rhine and Meuse: in 1990, some 68% of the total copper immission in surface waters of the Netherlands (570 t/y) and about 73% of the total zinc immission (2,780 t/y) was caused by transboundary inflow. In the case of copper in 1990, other noteworthy contributions were from sewage treatment effluents (12%) and antifouling treatments of ships (9%), while other significant contributions to the zinc immission in 1990 were via corrosion of building materials (10%) and sewage (5%), see Table 3.4.

In the steady-state situation, with a much higher immission into surface waters (1,050 t/y of copper and >3,580 t/y of zinc) the transboundary inflow appears to lose some of its importance (37% and 56%, respectively). For copper, the most important increases (compared to the situation in 1990)

were for "dissipative applications" (17% of total immission), runoff from soils and landfill sites, as well as sewage effluents. The latter is supposed to depend on an expected substantial increase in the corrosion of copper water pipes. Considerable increases in zinc immission were estimated to occur for corrosion of building material (24%) as well as for runoff from soils and landfill sites. Agriculture is a minor source for both copper and zinc immision in 1990, but in the steady-state situation, its contribution is supposed to have increased by a factor of 4. The only industrial source showing a marked increase between the 1990 and the steady-state situation is the food industry, due to higher copper and zinc contents in agricultural products. For surface waters, however, this remains a minor source.

The authors found that since transboundary inflow from foreign countries cannot be regulated by the Dutch policy, it is even more important to address the following domestic sources:

• copper water pipes

• anti-fouling treatment of ships with copper-containing materials

• zinc building materials or building materials coated with zinc

• emissions from landfill sites (especially in the long term)

• agricultural flows of both copper and zinc (in the long term).

The dominating origin of copper and zinc in agricultural soils is animal manure (79% of the total immission of 1,020 t/y for copper and 79% of the total zinc immission of 2,290 t/y, in both cases for the year 1990) and this origin will become even more dominant (82% and 86%, respectively) in the steady-state situation, Table 3.5.

Table 3.5. Origins of the immision of copper and zinc in agricultural soils in the Netherlands. S.S. stands for a steady-state scenario. After van der Voet and van Oers, 2000.

Origins Cu (1990) Cu (S.S) Zn (1990) Zn ( S.S)

Total immission, t/y

1,020

1,960

2,290

3,420

Animal manure

79%

82%

79%

86%

Phosphate fertiliser

11%

6%

1%

1%

Compost

6%

10%

4%

3%

Pesticides

1%

-

3%

2%

Atmospheric deposition

4%

2%

13%

9%

The predominance as well as the increase of this origin for copper and zinc is explained by the fact that animal manure is part of a closed loop and the main addition from outside to this loop (animals eat fodder, which is grown with manure, which is produced by animals eating fodder, etc.) is copper and zinc intentionally added to the fodder for productivity reasons. The authors point out that such a closed loop implies that even with relatively small additions - and the additions are indeed small compared to other zinc and copper flows - environmental stocks may rise above health risk standards. For a further discussion of the copper and zinc balances in agricultural soils, the reader is referred to sections 4.2.4 and 4.2.5 of this report.

When it comes to the most important origins of copper and zinc in the waste management system, 90% of the total amount of waste copper generated in the Netherlands (50,400 t/y) and 76% of the zinc waste (42,400 t/y) originates from building and demolition waste, Table 3.6. This fraction will decrease for copper (to 80%) but increase (to 59,200) in absolute number in the steady-state situation, and will increase for zinc both in relative (to 82%) and absolute numbers (to 53,800 t/y). Consumer applications contribute by <10% for the two metals both in 1990 and in a steady-state scenario, while industrial sources are important only in the case of zinc (13 and 8%, respectively).

Table 3.6. Origins of copper and zinc in the waste management system in the Netherlands. S.S. stands for a steady-state scenario. After van der Voet and van Oers, 2000.

Origins

Cu (1990)

Cu (S.S)

Zn(1990)

Zn (S.S)

Total waste generated in NL*, t/y

50,400

74,000

42,400

65,600

Building and demolition waste

90%

80%

76%

82%

Contaminant in concrete/iron & steel

1%

4%

1%

-

Discarded consumer applications

8%

9%

9%

7%

Industrial waste

-

-

13%

8%

Other waste materials

-

6%

1%

2%

* NL = The Netherlands

* NL = The Netherlands

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