The Tema Institute Campus Norrköping
Bachelor of Science Thesis, Environmental Science Programme, 2007
Maria Fredriksson
Organic chlorine in soil water-
Influence of Clear-cutting and
Rapporttyp Report category Licentiatavhandling Examensarbete AB-uppsats X C-uppsats D-uppsats Övrig rapport ________________ Språk Language Svenska/Swedish X Engelska/English Datum Date 2007-06-19 Nyckelord
Organiskt klor, avverkning, gödning, kväve, AOX
Keywords
Organic chlorine, Clorg, clear-cutting, fertilization, AOX ________________
Titel
Organiskt klor i markvatten - Påverkan av Avverkning och Kväve
Title
Organic chlorine in soilwater
-Influence of Clear-cuttning and Nitrogen
Författare Author
Maria Fredriksson
Sammanfattning
Klor är ett av de vanligaste ämnena på jorden och är viktig i alla levande e organismer, men klor kan också orsaka problem i miljön. Klor förekommer som oorgansiskt klor (Clin) samt organiskt klor (Clorg). Tidigare var den vanligaste uppfattningen att organsikt klor bara hade en antropgen källa, med de senaste årens forskning har visat att klor är den del av den biogeokemiska cyklen och att organiskt klor har även har en naturlig källa. Många klorföreningar är giftiga så denna nya forskning har fått stor uppmärksamhet. Gödning med kväve i skogsmark har visat oväntade effekter, tex ett ökat kväveläkage till mark och ytvatten. Avverkning är en störning på ekosystemet som är känsligt för störningar. På grund av att både klor och gödning kan skapa problem för miljön och att avverkning är en störning på miljön, kommer denna studie att undersöka om det är någon förändring på concentrationen av organiskt klor i markvatten efter avverkning och om gödning med kväve har någon påverkan på koncentrationen av organiskt klor. Studien gjordes på skogsmark i Värmland, Sverige (Hagfors). Kemiska analyser gjordes i laboratorier genom mätning av AOX (absorbable organic halogens). Resultatet av studien visar att avverkning troligtvis har en effekt på koncentrationen och att kvävet inte har det.
Abstract
Chlorine is one of most common element on earth and it is essential in every living organism, but can also cause problems in the environment. Chlorine can exist both as inorganic (Clin) and organically bound (Clorg). Earlier was the common opinion that Clorg only occurs from anthropogenic sources, but the last years, research has shown that chlorine is a part of the biogeochemical cycle and Clorg also can have natural sources. Many chlorinated substances are poisonous, so the fact that they have a natural source created attention. Fertilizations with nitrogen in forest areas have shown unexpected consequences, such as an increase leakage of nitrogen to ground and surface water. Clear-cutting is a disturbance on the ecosystem and the environment is sensitive for disturbances. Because of the fact that both chlorine and fertilization can be environmental problems and that clear-cutting is a big disturbance in the nature, this study will investigate if there are changes of organic chlorine (Clorg) in soil water after clear-cutting and if fertilization with nitrogen has any influence on the concentration of Clorg. This study was made in a forest area in Värmland, Sweden (Hagfors). Chemical analyses were made in the laboratory though measuring AOX (absorbable organic halogens). The result of this study showed that clear-cutting probably has some effect on the Clorg concentration and that nitrogen doesn’t have any influence.
ISBN _____________________________________________________ ISRN LIU-TEMA/MV-C--07/08--SE _________________________________________________________________ ISSN _________________________________________________________________ Serietitel och serienummer
Title of series, numbering
Handledare Tutor
Theresia Svensson URL för elektronisk version
http://www.ep.liu.se/index.sv.html
Institution, Avdelning
Department, Division
Tema vatten i natur och samhälle, Miljövetarprogrammet
Department of Water and Environmental Studies, Environmental Science Programme
Acknowledgement
I would like to thank my supervisor, Theresia Svensson for her help during this thesis, from the beginning with ideas and during the work in the laboratory, to find materials and for interesting discussion. I also want to thank Peter for all his help and support.
Maria Fredriksson
Abstract
Chlorine is one of most common element on earth and it is essential in every living organism,
but can also cause problems in the environment. Chlorine can exist both as inorganic (Clin)
and organically bound (Clorg). Earlier was the common opinion that Clorg only occurs from
anthropogenic sources, but the last years, research has shown that chlorine is a part of the
biogeochemical cycle and Clorg also can have natural sources. Many chlorinated substances
are poisonous, so the fact that they have a natural source created attention. Fertilizations with nitrogen in forest areas have shown unexpected consequences, such as an increase leakage of nitrogen to ground and surface water. Clear-cutting is a disturbance on the ecosystem and the environment is sensitive for disturbances. Because of the fact that both chlorine and
fertilization can be environmental problems and that clear-cutting is a big disturbance in the
nature, this study will investigate if there are changes of organic chlorine (Clorg) in soil water
after clear-cutting and if fertilization with nitrogen has any influence on the concentration of
Clorg. This study was made in a forest area in Värmland, Sweden (Hagfors). Chemical
analyses were made in the laboratory though measuring AOX (absorbable organic halogens).
The result of this study showed that clear-cutting probably has some effect on the Clorg
Contents Acknowledgement___________________________________________________________ 3 Abstract ___________________________________________________________________ 4 Contents __________________________________________________________________ 5 Introduction _______________________________________________________________ 6 Method ___________________________________________________________________ 7 Sample site ____________________________________________________________________ 7 Sampling _____________________________________________________________________ 8 Analysing the samples for Cl org___________________________________________________ 8
Preparing the samples __________________________________________________________ 8 Analysing the samples___________________________________________________________ 8 Statistical analyses _____________________________________________________________ 8
Result ____________________________________________________________________ 9
Clorg from the reference block, before clear-cutting compared with after clear-cutting _____ 9
Clorg, from the fertilized block, before clear-cutting compared with after clear-cutting _____ 9
Clorg compared with fertilized Clorg, both before and after clear-cutting _________________ 9
Clorg from the reference block compared with fertilized block after clear-cutting __________ 9
The first samplings compared with the last samplings, on both blocks __________________ 10
Discussion________________________________________________________________ 10
Clorg, impact of clear-cutting ____________________________________________________ 10
Influence of fertilization with nitrogen ____________________________________________ 10 Seasons variations _____________________________________________________________ 11 Other influences ______________________________________________________________ 11 Further studies _______________________________________________________________ 11
Conclusions ______________________________________________________________ 11 References________________________________________________________________ 12
Introduction
Chlorine is the 18 th most common element on earth (Winterton 2000), it is essential in every
living organism. Chlorine can exist both as inorganic (Clin) and organically bound (Clorg)
(Svensson 2006). Clin has a major source in the ocean and Clorg originates from different
sources. Chlorine belongs together with fluorine, bromide, iodine and astatine to the halogen group (Winterton 2000). This group is characterized by small bound energies and high electron affinities. Chlorine and fluorine are the most common halogens on earth. Chlorine participates probably in the production, transformation, transportation and degradation in natural processes (geological, chemical or biochemical) in both terrestrial and the aquatic
environment. Organically bound halogens (Clorg) are often used in manufacturing processes
(pulp and paper industry) and occur in pesticides/ herbicides such as PCD and DDT (Öberg
2005). Some decades ago the general opinion was that Clorg only had an anthropogenic source
(Johansson 2000), but in 1991 Asplund and Grimvall (1991) showed that chlorine is more widespread then previously assumed and that all chlorine in nature can´t be explained by pollution. A lot of studies followed which confirmed this theory (e.g. Johansson, 1996, Hjelm 1996, Öberg & Grön 1998). Hjelm (1996) showed for example in his study that chlorine is a natural constituent of soil organic matter.
The chlorine cycle is a biogeochemical cycle similar to the carbon cycle (Öberg et al. 2005). Studies have shown two different sources of chlorine, anthropogenic sources (solvents, pesticides, paper bleaching etc.) and from natural sources (Asplund and Grimvall 1991). The
information of the underlying mechanisms from the natural sources is scarcebut it appears
that Clorg is generally produced during decomposition of organic matter (Öberg 1996).
Examples of potential natural sources of Clorg in soil are precipitation, through fall, litter fall
and root exudates (Johansson 2000). Potential sinks in soil are leaching, volatilization and
mineralization. The focus in earlier research has been on either Clorg or Clin. The reason is an
old opinion, which says that Clorg and Clin are not connected or related for each other
(Svensson 2006). New studies have suggested that they are well connected in natural processes in soil (Johansson 2000; Johansson et al. 2003; Öberg et al. 2005; Öberg and
Sandén 2005). A theory is that inorganic chlorine Clin may transform to Clorg in soil and
vegetation (Asplund and Grimvall 1991; Winterton 2000).
Ecosystems are open systems, matter and energy can be supplied and be taken away from the ecosystem (Warfinge 1997). In an ecosystem can many types of microorganisms exists, which tie, refine and transform the different types of energy and material. The total amount of organic matter in living organism called biomass. When plants die, a lot of the organic chlorine goes back to the atmosphere and other nourishment, which were in the biomass, are released. In cold Nordic climate occur a slow decomposition with continuous storing in the ground, but the decomposition can be effected of many things (eg. temperature, pH, precipitation).
Disturbances such as climate, type of ecosystem and topography are factors that can have
effects on the Clorg concentration (Johansson 2000; Öberg 2003). Research indicated that
disturbances in the environment (e.g. clear-cutting) can have an effect on the concentration on
inorganic chlorine (Mannerkoski et al. 2005). Both Clorg and Clin are sensitive for this type of
disturbances. After clear-cutting, studies have shown a higher concentration of Clin in run-of
water and an leaching of Clorg (Kaufmann 2003; Lovett et al. 2004; Mannerkoski et al. 2005).
A study in Hubbard Brook (Lovett et al. 2004) hypothesise that a lot of Clin is taken up by
vegetation. Studies suggest a connection between the concentration of carbon in soil and the
concentration of Clorg in soil (Johansson et al. 2003). In a study made in 1989 it was
suggested that organic chlorine might be related to the amount of organic matter in soil (Asplund et al. 1989). This study showed that the chlorine-to-carbon ratio varies less then the
concentration of Clorg. Biomass contains Clin and Clorg (Öberg 2003), which can be released
when organic matter is being decomposed. The formation of Clorg seems to be closely related
to decomposition of organic matter in soil
Only one study has been made on the connection between Clorg and clear-cutting. In this study
Clorg seems to be lower after clear-cutting (Hoppe 2006). The study showed an indication that
clear-cutting had an impact on the Clorg concentration. That study was made on run-off water
and this was made on soil water so it´s not the same as this study.
For a long time it was common to give the forest nitrogen fertilization the year before clear-cutting (Warfinge 1997), to give the plants and trees a last chance to grow. In the south of Sweden is it forbidden today, but the nitrogen remains in the plants and soil for a long time. The reasons for the ban of nitrogen were unexpected consequences, such as an increase leakage of nitrogen to groundwater and surface water. When the organisms in soil has a surplus of nitrogen they use that for their need of nitrogen to save energy instead of break down organic matter that give a low value on the connection between carbon and nitrogen. Studies on the connection between fertilization and chlorine suggest that an addition of nitrogen decreased the formation of organically bound chlorine in litter (Öberg et al 1996). Even a study made by Johansson et al. (2000) indicates that fertilization causes a decrease in
the concentration of Clorg in soil.
The aim of this study is to observe changes of organic chlorine (Clorg) in soil water after
clear-cutting. This study will also observe if there is any difference in an area which has been fertilized with nitrogen. This study was made in a forest area in Värmland, Sweden (Hagfors). The former study made on run-of water (Hoppe 2006) has indicate that clear-cutting has an
influence on the concentration of Clorg, because of that it´s interesting to continue the studies
on that field. No former studies have been made on which effect nitrogen has on Clorg after
clear-cutting in soil water.
Method Sample site
165-Hagfors is situated in the county of Värmland in Sweden (60º00`N and 13º43`E). The annual precipitation in the area is about 730 mm and the mean air temperature is 3,5ºC (Alexandersson et. al 1991). The upper part of the soil is podzolized. The stand consists of Scots pine. At the time of establishment in 1981, the stand was 64 years old and on an average height of 17 m.
165- Hagfors is divided into blocks, which have been prepared in different ways. Two blocks have been fertilized with different intervals, and one is a reference plot without fertilization.
At each fertilization 150 kg N ha-1 was applied as ammonium nitrate at 4 or 8 years- intervals.
The total amount of N-fertilizer, applied since the first fertilization in 1981 until today, varies
from 900 to 1800 kg N ha-1. The study blocks are 30m x 30m. Each block has three replicates.
This study is delimitated to focus on the reference block and one fertilized block with 150 kgN/year and an interval of 4 years (1981, 1985, 1989, 1993, 1997 and 2001). The total amount of nitrogen is 900 kgN. That fertilized block was chosen for the reason that it had the same samples date as the reference block.
Sampling
The samplings were made with lysimeters. They were put in the ground with an angle of 75º to the horizon level to avoid water to come in wrong way. The lysimeter exists of a 9 cm long pipe, at which the last 5 cm is ceramic. The samplings are made at a depth of 45 cm in the mineral soil. The samples are taken out from the lysimeters with a water pump to a glass bottle and then transported from the sample site and stored in a deep freezer.
Analysing the samples for Cl org
Cl org is measured by AOX (absorbable organic halogens) using a Euroglas ECS 3000. AOX
represents a sum of all organically bound halogens in water (chlorine, bromide and iodine), which can be adsorbed on activated carbon (Johansson et. al 2003). The analysis gives a sum
of all the halogens, not only Clorg, but chlorine is considered to be the most abundant halogen,
and the other ones are not considered in this study.
Preparing the samples
4 ml sample was diluted with 96 ml RO-water. Drops of concentrated HNO3 were added to
ensure a pH under 3. 50 mg active carbon and 5 ml of a low nitrate stock solution (containing
2 ml of HNO3 , 20.2 g KNO3 and 98 ml RO-water), was added and put on a rotary shaker for
one hour (98 r.p.m). This procedure makes sure that the organic compounds in the samples were adsorbed to the carbon.
Analysing the samples
The samples were filtered through a membrane filter (0,4 µm) to get out the carbon with the bounded absorbable organically bound halogens (AOX) from the rest of the samples.
Nitrate washing solution and then RO-water was used to wash out extra chlorine. Afterwards, the filter was placed into the boat and inserted into the AOX oven. In the AOX instrument, the active carbon was combusted in an oxygen stream, and the organic halides determined using a microcolorometric titration. The temperature in the combustion chamber was about 1000ºC, and several replicates from each sampling date were analysed. Analysis and preparations were made according to SIS standard SS-EN 1585 (1997).
Statistical analyses
The statically method Mann-Whitney has been used to investigate if there was any statistically difference between the samples. Mann-Whitney test provides a nonparametric equivalent to a test that allows comparisons of samples which are not normally distributed
(Whether & Cook 2003). This test can also be applied to samples of different sizes.
Four different statistical analyses were made:
1) Clorg from the reference block, before clear-cutting compared with after clear-cutting,
2) Clorg, from the fertilized block, before clear-cutting compared with after clear-cutting,
3) Clorg compared with fertilized Clorg, both before and after clear-cutting
4) Clorg from the reference block compared with fertilized block after clear-cutting
5) The first samples compared with the last samples, on both blocks
The confidence interval was 95% and the significant level (p value) was 0.05 (Weather& Cook 2000)
A diagramwas used to illustrate the concentration of Clorg both before and after clear-cutting
and the difference on the samples with nitrogen.
Result
When looking at the diagram (figure 1) it seems that the reference and fertilized samples follow the same curve in the beginning and in the end. The concentration on the fertilized block seems to follow a smother curve.
Figure 1: The mean results from all analysed samples, the blue (dark) curve shows the results from the
reference block which, the pink (light) curve shows the result from the fertilized block. The first three dates (20051111, 20051124 and 20051207) are before the clear-cutting. The last five (20060626, 20060821, 20060928, 20061102 and 20061122) are after the clear-cutting. The clear-cutting was made in mars 2007.
Clorg from the reference block, before clear-cutting compared with after clear-cutting
There is a difference between the Clorg concentration after and before clear-cutting, but the
difference is not statistic significant, the p-value is 0.25 which is over the chosen level on 0.05.
Clorg, from the fertilized block, before clear-cutting compared with after clear-cutting
The concentration of Clorg on the block which has been fertilized seems to follow a smother
curve then those from the reference block. The two last concentrations are almost the same as
the curve for the reference block. There is no significant difference on Clorg concentration
before and after clear-cutting (p-value is 0.25).
Clorg compared with fertilized Clorg, both before and after clear-cutting
The concentration over the hole sampling period on the reference block and the hole sampling period from the fertilized block showed that there is no significant different (p-value is 0.88)
Concentration of Clorg
0 200 400 600 800 1000 1200 20 05- 11-11 20 05- 11-24 2005 -1 2-07 Clear -cut ting 20 06-06-2 6 20 06- 08-21 20 06-09-2 8 20 06- 11-02 20 06-11-2 2 Date µg /l reference fertilizedThe first samplings compared with the last samplings, on both blocks
Then looking at the diagram (fig.1), it´s possible to see, that the two first samples (in Nov 05) are higher than the two last (in Nov 06). It´s also confirm with the statistic test that the different is significant with a p-value on 0.01.
Discussion
Clorg, impact of clear-cutting
In this study it seems to be some diffrent before and after clear-cutting, but it´s not statistical significant. The first sampling (June -06) after clear-cutting showed a low value. Two days before the sampling there was a heavy rain (Svt 2006) which can affect the concentration. Due to Svenssons study (2006) made on run-off water, an increase in water discharge during
wet periods has a small or no influence on Clorg. That study also showed that Clorg
concentrations are higher during the summer, depending on higher amount of topsoil-leached
Clorg. The result in this study showed a low amount in the summer and after rain. One theory
is when the rain flowed through the soil the Clorg concentration was diluted and a consequence
of that is lower concentration. Another theory is because of high value in the runoff water in
Svenssons study (2006), the Clorg is leaching out to the run-off water and flushed away from
the soil water. A result from that can be lower concentration of Clorg in soil water.
The increasing after clear-cutting is expect since the concentration of Clorg is strongly
connected to organic carbon (Öberg 2003; Johansson et al. 2001). When the area is clear-cut there might be a release of organic matter, but the biomass have to be decomposed by
microorganisms before a release of Clorg can be done and a higher concentration can be seen.
Some month after clear-cutting showed the curve a decrease. This can be explained with the autumn and winter. All process in the ground during the winter is slowing down. Hoppe
(2006) has a theory that the concentration of Clorg also depend on how much biomass is on the
ground, after clear-cutting it can take some time before all trees have been removed and when
they are removed the release of biomass and Clorg is slowing down. The study by Öberg et al.
(1996) showed that a net formation of Clorg until 30-40 % of the needles were gone, that can
also explain why the values are decreasing.
There is a statistic different when comparing the first samples with the last, that showed that
clear-cutting probably has an influence on the Clorg concentration after clear-cutting. That can
be explained with the theory that it takes time for processes in the soil.
Influence of fertilization with nitrogen
This study showed that there is no significant difference on the samples from the fertilized and them from the reference block. When comparing the fertilized curve with the reference curve it´s seems that the fertilized curve is smoother, but it´s possible to see the same trend on both curves (especially in the beginning and end of the period). Former studies have shown
that nitrogen hampered the concentration of Clorg (Öberg et al. 2006). This is not clear in this
study, there is no significant difference on the nitrogen plots but they are rather higher than lower comparing to the reference block. Öberg et al. (2006) study was made with incubation
in laboratory. Also a study made by Johansson et al. (2001) showed a decrease of Clorg after
fertilization, also this study was made with incubation in laboratory. Due to the theory that
carbon and Clorg is connected (Johansson et al. 2003) and that organism prefer to use nitrogen
direct instead for decomposition of organic matter (Warfinge 1997) also confirm the theory
that nitrogen hamper Clorg concentration. So if there is enough nitrogen in the ground, it´s
possible that it doesn’t matter if the area is clear-cut or not. The former studies (Öberg et al. 2006 and Johansson et al. 2001) showed an increase in their result. Those two studies together with this study show that the nature is not always the same as laboratory studies.
Theory is that something in the nature has an influence on the connection between Clorg and
nitrogen. It could be interesting to continue with more studies in that field. It´s also possible that the amount of nitrogen in this study was to low and that a bigger addition of nitrogen can show a different result.
Seasons variations
Hoppe (2006) found in her study that the highest concentrations of Clorg were between May
and August. Also Svensson (2006) found higher amounts of Clorg in summer. This can be
explained by an increase amount of top-leached Clorg. Both this studies were made on run-off
water. Unfortunately it is difficult to see any clear difference over seasons in this study, more samples must be taken and over a longer time to se that. There are samples from both
November 2005 and November 2006 and there is a different between them, but it´s difficult to know if the different is from the clear-cutting or not. It can be important to have in mind that
the season can have an impact on the Clorg concentration.
Other influences
In the nature can many things influence the concentration of Clorg, both Johansson (2000) and
Öberg (2003) suggest that Clorg are sensitive to disturbances in the ecosystem and that can
also be seen in this study. Examples of what can effect the concentration of Clorg are distance
to sea, amount of precipitation and amount evapotranspiration (Johansson et al. 2001). It´s also possible that other substances in the soil have influence on the concentration.
Further studies
It is interesting for further studies to complement this study with a measurement on the
concentration of Clin, to compare with the concentration of Clorg. It´s also interesting for the
further to make more studies in nitrogen’s influence on chlorine and why the results are different in nature compared to the studies made in laboratory. It can be interesting to study how different amounts of nitrogen can affect the results.
Conclusions
Clear-cutting has probably an influence on the Clorg concentration. The different is not
significant when comparing all the samples with each other, but when comparing the first samples before clear-cutting with the last after clear-cutting, is the different significant. There is no difference between the reference block and the block which has been fertilized.
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