IMPACTS OF  CONTAMINATED SOIL LEACHATES ON THE ENVIRONMENT

Prof.Dr. Adnan AYDIN

Marmara University, Director of Environmental Research Center, Göztepe  Campus, Kadıköy-İstanbul/Turkey

I am pleased to be here with you to present a paper in the  International Conference organized by the European Institute of Cyprus and Lefke Environmental Society.

Environmental pollution  today is an important problem which has been  strongly threatening our world. Industrial processes and the settlements of the people should be  strictly taken  under control by regarding regional and global  environmental affects. Circulation of material in different media, carries  the effects  of regional  pollutions to the near or far parts of the world. Thus, some regional problems may become  important  global problems by time. 

From environmental point of view, an industry  should be  judged along with its supporting  minor or  initial  activities.  For example,  paper consumption and marketing  data orient the processes in the paper manufacturing industry and the extent of the use of  forests. Uncontrolled destruction of forests  are believed to be responsible for   greenhouse effect and changes in climates.

Depletion of the ozone layer and greenhouse effect  are the global environmental problems. However, pollution  of   water bodies and air  are  also global problems. Pollution in  Danaube river,  as well as  extensive  marine transportation through Turkish Straits are  very important to protect the Black Sea-Marmara Sea-Mediterrenian Sea  System. In aqueous and gaseous phases, it is not possible to  trap the pollutants efficiently.

Pollutants ,regardless they are domestic or industrial in nature, can be easily transferred between physical phases. Soil, is a stationary solid phase, unless it is somehow moved, is an important trap for pollutants. However, it can release the pollutants into mobile phases by several activities  which  may be physical, chemical, biochemical or biological processes.

North Cyprus society has encountered  a challenging environmental pollution problem due to the older copper enrichment factory. The Conference Site is near of that area of idle mining and floatation factory  for copper. We have been informed that the area had several environmental problems since its running periods during which  the wastes of any kind  have not been treated by any means.

Cyprus Copper Mines  has not been running since 1975. The Gemikonağı Copper  Mining and Floatation  Factory is located by the Mediterranean shore at Gemikonağı in Northern Cyprus. It is known that   stormwater run off is  being discharged into the Mediterranean Sea. The  Surface Water Storage Reservoir by the area has also  been  seriously threatening by the storm water run off. The floatation pools are still  potential  polluting sources which are being activated  whenever it rains.

The mining area includes underground mining shafts, leaching ponds and  destroyed natural texture along with contaminated   piles of residues.  The residues are estimated to be around 2 million tons  which contain  sulfates of copper, iron, arsenic, lead, manganese and aluminium as well as their oxides, silicates etc.,

From the cyanide leaching applied in the mining processes also   left  partly leaked cyanide drums in the working area. Although the possibility for the existence of free cyanides is very low,  it can be told that some parts of the residues and wastes should contain  complexed cyanides which are more resistant against decomposition. However, they are potential  danger for the environmental health, since they are susceptible partially  against air oxidation, by which route, some of the polluting  heavy metals  can  be leached by rain and underground waters.      

In the area there are five circular wastewater  clarifiers  with around  100 m diameter and 3 m depth, and they contain around 100.000 tons of waste material which need to be handled.

As a result, from the mining , leaching and floatation  processes  the soil and sea water should be dangerously  contaminated to threaten the public health, agriculture and  ecological properties of the Sea. The contaminated area  covers approx. 4 square kilometers.

According to EPA,1991^*,1 13 metals are to be detected at hazardous waste sites.

                        Silver                                       Mercury

                        Arsenic                                  Lead

                        Barium                                                Selenium

                        Cadmium                               Thallium

                        Chromium                               Antimony

                        Nickel                                      Copper

*EPA (U.S.Environmental Protection Agency),(1991), Seminar Publication: Site Characterization for   Subsurface Remediation, Report No : EPA/ 625 / 4-91 / 026, Cincinnati, Ohio,45268.

The piles of residues from  the mining and floatation processes have most of these elements  in appreciable quantities.

Preliminary  analytical results of  the  environment  has indicated  that such contaminations are  at  serious  levels.  A blended soil sample taken from smelting facility has been found to have moisture 15.57%; lead 153 mg Pb/kg dry soil ; copper 510 mg Cu/kg dry soil and iron 153.333 mg Fe/kg dry soil².

Short Analysis of Blended Soil Sample Taken From Floatation Facility (*^,2)

pH                                          2.73                             Cu (mg Cu/kg dry soil)       510

H₂O (%)                              15.57                           Fe (mg Fe/kg dry soil)        153.333

(*) Bilge Alpaslan, M.A.Yükselen,”Remediation of Heavy Metal Contaminated Soils” MSc Thesis on Env.Eng.,Marmara University, Institute  for Graduate Studies in Pure and Applied Sciences, 1999.

At some sites, arsenic, chromium, selenium and manganese have been found in soil by TCLP (Toxicity Characterization Leaching Procedure ) at appreciable concentrations. Cyanide, sulfate, arsenate and chloride are the most abundant anions which have been extracted by water.

Since the contamination levels are to be  different  for a specific pollutant from site to site, in the future a detailed study need to be taken into  consideration.

Remediation of the Site

The landfilling of the mining, leaching and/or floatation wastes which can be a choice to regain the agricultural area  needs  carefull examinations of the filling site in order to determine its geology as well as its hydrogeology.

However, landfilling is not always the solving of the problem. The filled land also may act as an continous polluting source. Thus, a proper remediation project is needed for the site.

In-situ treatment technique soil flushing and other techniques may be of worth in future for special restricted areas. Leachability of heavy metals from soil can be decreased by use of stabilization/solidification(immobilization) techniques. Application principles of these techniques may be selected regarding the properties of contaminated site and the intended use of site.

Recreation  activities  at  the mining site is also a problem which should  be planned before the new attempts are held to run the mine and the factory.

For  a mid-term conservation, my opinion is that  the piles and the  silt could be  prevented from  conducting with storm waters by use of water-proof clay layers which are spreaded 1 m beneath  the contaminated soil. The clay application can be done  by preparing  the compartments of piles. Polluting heavy metals and anions can be taken by the properly chosen  plants from the polluted soil. Thus, selective plantation at the area  may help to inhibit the wind errosion and the surface soil layer can  be  freed  from the metallic contaminants  by several harvestes. The harvested plants  need to be fired under control of  wastegases.

Transfer of Pollution

As previously  given, transfer of pollution is one of the most important environmental problems. The natural means of pollution transfer are air and water  circulations. Water supplies and uncontaminated soils can be  easily contaminated by drainage of polluted water through the soil layers or by the surface waters. For agricultural and domestic usage, polluted underground water need to be  effectively treated or otherwise should be prevented from use. Polluted soil is always a pollution source since it is  open to uncontrollable chemical reactions and   to both the biological and biochemical  activities.

Mobility of metals in soil depends upon their reaction capability with the soil components. This can also be  seen from the laboratory experiments. In the thesis of Alpaslan, extraction of metals by use of  water with pH 2 or with pH 4 has given the mobility order  as Cu > Fe > Pb.  By 24 hrs contact time at pH 2 , 3% of Pb; 95% of Cu and 10% of Fe have been leached. At pH 4 , extraction yields are reduced  by around  25%.

However, the most emergent problem arises  from the  storm water drainage of  mining and  factory area  into  the sea.

The metals in the  processed  mining material may be transferred  into the aqueous phase by chemical or biochemical reactions. Acidity or in some cases the alkalinity of the water contacted with solid material  causes  dissolution of  heavy metals and  other polluting  ions such as complexed cyanides etc. In that case,  stormwater  can be regarded as a secondary leachate from the site.

Impact On Natural  Water Bodies

Elements occur in nature in their most stable states and metals  in natural waters may exist in dissolved, particulate or colloidal forms. Dissolved forms are the metal ions complexed with water or with several ligands. Insoluble metallic oxides, hydroxides, carbonates, sulfides or  silicates may yield colloidal or particulate forms.  Metallic ions may also be adsorbed or complexed  on insoluble colloids of organic or inorganic matrix.

The redox and hydrolysis  are important processes in the  heavy/transition metals’ chemistry.

Ecological results of flowing of  such leachates to natural water reservoirs have been the subjects for several studies. The quantity and load of the leachates leaving the site determine the point where it would ultimately drain to.

The stormwater does not have only the ions or molecules but also contains  insoluble soil material.  This material covers the bottom of the sea and in the new  chemical environment further reactions occur.  Thus, the impact of  stormwater contents  on other components of the environment yield different equilibria competing with each other.

The leachates from the factory site  can be in acidic in nature. The acidic solutions of metallic sulfates, such as ferrous and copper sulfates, will be carried by surface waters into the sea and will be diluted and neutralized. In the sea water, the chemical species will be oxidized and hydrolyzed.

The leachates  from mining area should be mainly in inorganic nature and would not have direct correlation with eutrophication, but would cause changes in specific diversity of planktones which affect the  food chain.

By the effect of leachate, the water columns as well as the bottom sediments should be enriched by heavy metals. The sediment column should be  the major reservoir of metals.

The sediments are the main carrier phases for trace elements. At the sediment-water interface, during the recycling between phases,metals are buried in the sediment by adsorption or by complexation and at the same time they are released into the pore water by diffusion. Metal ion exchanges into the main water body also occur.

Scavenging, the adsorption and removal of dissolved elements from the water column by sinking particles, is an important process and its rate could be strongly correlated with the primary productivity at the sea surface.

The processes called mineral weathering, such as dissolution of oxides, hydroxides and carbonates;incongruent dissolution of aluminosilicates; or sulfate adsorption onto metal oxides as well as sulfate reduction and assimilation  would effect the alkalinity  of sea water.

The nutrients such as phosphate also react with metallic ions such as  iron(II) to yield insoluble hydroxyphosphate particles.

Regarding the points given above,  in contact with the leachates, the sea-water fauna and flora may be exposed to several factors :

.  Acidification of the water column via the hydrolysis of metallic salts ;

.  Lowering pH of the water ( pH <2) column contacted with acidic leachate;

.  High oxygen consumption during the oxidation of metals in lower states;

.  Heavy metal accumulation in flora and  fauna  species;

.  Toxicity on flora and fauna ;

.  Increase in water turbidity, which effects  the sun light penetration through water  to prevent photosynthesis. The weakened light illumination  may  impact on bottom macroalgae both in coastal zone and  in the offshore areas starting from different depths.

.  Stratifications resulting from different salt content reduce the mix-up of the water creating different environments for the same or similar living species.

.  Jelly precipitates  accumulate on algae which are important in food chain. Consequently,  effective photosynthesis and oxygen releasing into the water are prevented.

The health of the environment can be assessed by the observation of biodiversity. The element cycle is to be  prevented from breaks.   The biological effects of wastes should be evaluated and should force  to introduce changes in the applied technologies. The process technologies should be rearranged.

At the interested area, probably, the influence of pollution on benthic organisms should be  significant in the shelf and coastal zones.

 Pollution Monitoring and  Research  on Ecological Damages

We are strongly interested in  the  ecological situations  concerned with the pollution  coming from the mining and  floatation site.

As far as we know, there  are  also considerable gaps in the background informations both  on geochemistry of   the shelf  and  on the metal  distributions in the  sea water as well as in the  bottom sediments  of  coastal zone and  offshore areas.

The marine pollution and ecological monitoring work should be carried out simultaneously. The network of sampling stations are to be selected to include the points where potential impacts may be occurred as well as the points in the undisturbed areas.

It is essential that continous scientific monitoring of water columns, bottom sediments and marine organisms are needed  to notice the possible ecological damages.

The aims of our research programme on the water pollution  can be outlined   as  :

. to  maintain background data for specific  uncontaminated areas;

.  to be alert  to environmental emergencies coming  from the mining and floatation area;

.to reach the knowledge of restoring and conserving of natural sources;

. to get    environmentally safe  routes  to manage the area;

. to get the transboundary effects of hot points on fisheries, on biodiversity and on public health including economical aspects.

The long-term project not only will achieve  the  ecological background data of  water bodies, sediments and soils; but also will  give  scientific supports for the recreation and remediation of the mining  and floatation site.

The public health is an important branch of environmental protection and the public  health screening affairs should be  performed and statistical data of the past years  regarding the public health should be gathered from official  registrations as well as   people  of the region.

REFERENCES

[1]  EPA (U.S.Environmental Protection Agency),(1991), Seminar Publication: Site Characterization for   Subsurface Remediation, Report No : EPA/ 625 / 4-91 / 026, Cincinnati, Ohio,45268.

[2]  Bilge Alpaslan, M.A.Yükselen,”Remediation of Heavy Metal Contaminated Soils” MSc Thesis on Env.Eng.,Marmara University, Institute  for Graduate Studies in Pure and Applied Sciences, 1999.