The daily changing pattern of hydrogen peroxide in new zealand surface waters

652

Environmental Toxicology and Chemistry, Vol. 15, No. 5, pp. 652–662, 1996q 1996 SETAC

Printed in the USA0730-7268/96 $6.00 1 .00

THE DAILY CHANGING PATTERN OF HYDROGEN PEROXIDE IN NEW ZEALANDSURFACE WATERS

REIMER HERRMANNLehrstuhl fur Hydrologie, Universitat Bayreuth, 95440 Bayreuth, Germany

(Received 13 April 1995; Accepted 11 October 1995)

Abstract—Concentrations of hydrogen peroxide (H2O2) were measured during daytime every 2 h at several depths in a catena oflakes of different trophic states including oligotrophic lakes Selfe and Oxbow, eutrophic Lake Hayes, dystrophic Lake Hochstetter,and a hypertrophic oxidation pond. The daily patterns of H2O2 of the various lakes can be explained firstly by the turnover regimeof H2O2 which results out of simultaneous biological or chemical decay and formation yield (ratio of H2O2 formed per UV radiationdose) and secondly by internal transport. As in dystrophic, eutrophic, and hypertrophic lakes with high turnover, H2O2 is formednear the surface and the decay is rapid over the entire water column, a H2O2 pattern with sharp temporal and vertical gradientsdevelops. In contrast, oligotrophic lakes allow deeper penetration of UV radiation, thus H2O2 is formed over greater depths. Further,the (biological) decay is slower than in lakes of higher trophic state leading to less sharp gradients within the daily H2O2 pattern.Input of H2O2 by wet deposition can contribute considerably to the increase of H2O2 in lakes, whereas dry deposition and groundwaterflow do not.

Keywords—Hydrogen peroxide Surface waters Daily pattern New Zealand

INTRODUCTION

Concerns are rising about a global change of climate, whichis based on changes of UV irradiance, rainfall, and temperaturefor example. One possible impact of increased UV irradianceon lake ecosystems is increased formation of H2O2. Studies onthe temporal and spatial behavior of H2O2 in lake waters maybe a precondition for a better understanding of the impact ofH2O2 on aquatic ecosystems: Although H2O2 is not very re-active against organic compounds, it can be transformed intoa strong oxidant in combination with transition metals or UVradiation (photolysis of H2O2) as under such condition reactivehydroxy radicals may be formed. Reactions of transition metalswith H2O2 may change their redox state, further metal ionsadsorbed on iron and manganese (hydr)oxides may return intosolution after reaction of the oxides with H2O2, and the decayof H2O2 may be catalyzed by metals. Finally H2O2 acts as asource of free radicals, either forming ·OH by means of oxi-dation of transition metals or forming ·O2

2 by reducing tran-sition metals [1].

Transition metals can be made available as trace nutrientsfor aquatic organisms by H2O2 influencing their redox state [2,3].H2O2 is a poison to algae [4] and bacteria [5,6]. Draper andCrosby [7] report the decay of organic xenobiotica induced byH2O2. However, Frimmel [8] puts forward that irradiation in thepresence of H2O2 transforms and degrades humic substancesand that the degradation of pesticides decreases.

The aim of this study was to undertake a systematic fieldstudy of the chemodynamics and transport behavior of H2O2 ina catena of lakes ranging from oligotrophic (low productive)and eutrophic (high productive) to hypertrophic (extremely pro-ductive) and dystrophic (humic). In order to explain the behaviorof H2O2 I wanted to investigate those factors that possibly con-trol the changing pattern of concentrations of H2O2 within thelakes, as there are dry and wet deposition of H2O2 onto the

* To whom correspondence may be addressed.

lakes, inflow of H2O2 with groundwater, underwater UV irra-diance, dissolved organic carbon (DOC), bacteria, and wind-induced turbulence.

Excellent and comprehensive reviews exist on factors af-fecting the distribution of H2O2 in surface waters [9–11] andatmospheric chemistry [12]. Sturzenegger [1] gives an extensiveand comprehensive review on the photochemistry of H2O2.

The predominant photochemical mechanism for the forma-tion of H2O2 proceeds as follows [1]: Light excites dissolvedorganic matter, which then transfers an electron or a hydrogenatom onto oxygen or another reaction partner. The anionic orneutral radical formed herewith then transfers an electron ontoan oxygen molecule resulting in a superoxide anion (·O2

2). Someof this ·O2

2 then disproportionates to H2O2 and oxygen. In ad-dition, Cooper et al. [10] report that nonphotochemical andbiological processes do not significantly form H2O2. Thus, mostof the H2O2 production is confined to the depth of UV irradiancepenetration [13]. The breakdown of H2O2 in natural watersseems to be caused by bacterial catalases and peroxidases[10,14]. It may be possible that freshwater algae can form H2O2

under photosynthetic active light below the depth of UV irra-diance penetration and that they are also able to catalyze thedecay of H2O2 [15]. The importance of the two latter processesin the natural environment are not known. High concentrationsof dissolved organic matter (DOC 5 140 mg L21) in a NorthGerman peat lake caused a chemically induced decay of H2O2

via oxidation (unpublished results of another investigation ofthe author).

As snow and rain can at times have high concentration (upto c(H2O2) 5 60 mmol L21) of H2O2 [12,16,17], the concentrationof near surface lake water can be increased by wet deposition[11]. Sturzenegger [1] shows that dry (vapor phase) depositionof H2O2 onto water surfaces seems to be negligible.

Holm et al. [18] found extremely low concentrations ofH2O2 in groundwater (c(H2O2) 5 0.02 mmol L21), a result that

Hydrogen peroxide in New Zealand surface waters Environ. Toxicol. Chem. 15, 1996 653

Table 1. Environmental setting of the lake catchments

Name

Maxi-mumdepth(m)

Area(ha) Parent rocks Soils Land use, vegetation Trophic state

Oxbow Lake within thebanks of the Wai-makariri R.

0.5 0.1 Greywacke gravel togreywacke-derived silt

No soil development Free of vegetation Oligotrophic

Lake Selfe 29 65 Greywacke and argillite High country yellow-brown earths, silt tostony loams [Ochrept]

Tussock grassland, ex-tensive pasture

Oligotrophic

Lake Hayes 35 203 Chlorite schists, schist-de-rived loess, till and ter-races

Yellow-gray earths, finesandy to sandy loams,mostly stony[Ochrept/Aquept]

Intensive pasture, vin-yards

Eutrophic

Lake Hochstetter 16.8 474 Slightly weathered grey-wacke-derived till andglacial outwash gravel

Podzolized yellow-brown earths and pod-zols, loams to sandyloams, peaty in places[Orthod/Aquod/Aquent]

Podocarp swamp for-est, clearings withfern and manuka

Dystrophic

Oxidation Pond 1.5 32Waters derived from separate sewer system, mechanical and biological treat-

ment (trickling tower), third of three oxidation ponds in a line Hypertrophic

Fig. 1. Study areas.

654 Environ. Toxicol. Chem. 15, 1996 R. Herrmann

Fig. 2. Variation of c(H2O2) with percentage of fallen rain (S P, %).– – –, 12.11.94, Lake Hochstetter; , 12.10.94, Webster’s Farm,West Melton, 20 km southwest of Christchurch.

Table 2. Some limnological properties of Oxbow Lake within thebanks of the Waimakariri (braided) River, 26.08.94

Time/variable

k20

(mScm21) pH

q(8C)

DOC(mg L21)

m*(m s21)

Bac-teriacells

(n 3 103

ml21)

09.50 NZWT12.0014.4516.45

69.9 7.58.37.97.9

5.9

11.0

1.9 0.81.41.40.5

0.1

Fig. 3. Westerly and northerly winds associated with depressions bring heavy rain to the west coast [32]. The source being in the subtropicscauses high c(H2O2) in rain (a). Easterly or southerly winds associated with cold fronts moving from the south cause rain with low c(H2O2) overthe east (b).

leads to the assumption that transport of H2O2 by groundwatershould be insignificant.

Finally, wind-induced turbulence transports H2O2, whichis formed near the surface into greater depths [10]. On thebasis of these controlling factors I would hypothesize thatone should observe a change of patterns of temporal andvertical variation of H2O2 within a lake depending on itstrophic state.

HYDROECOLOGICAL FEATURES OF THE LAKES

In order to encompass a wide range of factors affectingthe dynamics of H2O2 in surface waters like concentrationsof humic substances, concentration of bacteria, underwaterlight climate or mixing behavior, I selected a sequence oflakes of different trophic states (Table 1 and Fig. 1): LakeSelfe [19,20] and an oxbow lake [19,20] within the banks ofthe braided Waimakariri River had low concentrations ofDOC and bacteria and high light penetration; however, the(from now on thus called) Oxbow Lake was very shallow.Both lakes are oligotrophic. Lake Hayes with a higher con-centration of DOC, bacteria, and a lower light penetration isone of the few eutrophic lakes [21] of the South Island. Fi-nally, within this sequence, I selected the last of a series ofthree oxidation ponds behind the mechanical and biological(trickling tower) treatment of the sewage plant of Christ-

church as an example of a hypertrophic lake with high DOCconcentration, high bacteria concentration, and low light pen-etration. In order to study the case of a lake with low lightpenetration, high DOC concentration but low bacteria con-centrations I selected the dystrophic Lake Hochstetter [22].Humic acids are leached into Lake Hochstetter by heavy rain-fall (Pannual ca. 3,000 mm) from podzolized yellow-brownearths and podzols developed from greywacke till with lowbuffer capacity. The three deeper lakes (Hochstetter, Hayes,and Selfe) belong to the class of warm monomictic lakes thatare only stratified in summer. Otherwise, circulation occursin the whole vertical water column. The two shallow waters(Oxidation Pond and Oxbow Lakes) are polymictic. Duringthe time of this study there developed no stable stratificationin any lake. Detailed limnological data related to H2O2 dy-namics like pH, electric conductivity (k20), DOC, temperature(q), bacteria cells, and light climate are given in Figures 4–9 and Tables 2 and 5.

SAMPLING AND CHEMICAL ANALYSIS

I sampled water of consecutive depths by means of a luer-lock silicone elastomere catheter (VYGON, Aachen), whichcan be coupled with a syringe for precise chemical depthprofiling. At each depth, two samples were taken. Water ofpredetermined depths was filled into quartz tubes and glasstubes, the latter wrapped into aluminum foil. The pairs oftubes were then suspended horizontally at the depths of originof the water between a buoy and an anchor. I determined theinitial H2O2 concentration within the tubes and exposed themfor 1–2 h. The formation yield a (mmol H2O2 L21 [kWh m22

of UV]21) [1] is defined as the ratio of H2O2 formed per UV


Table 3. Chemical and physical methods

Variable Apparatus Method

pH Ingold U 455 combined glasselectrode

Potentiometrically

k20, specific electrical con-ductivity

WTW, LF91 Conductimetrically

DOC Shimadzu TOC-5050 IR detection of CO2

Bacteria Zeiss microscope UMSP-50equipped for epifluores-cence

Staining of DNA with 4,6-diamidi-no-2-phenylindole hydrochloride(DAPI) [30]

Photosynthetic active radia-tion (PAR)

LI-192 SA underwater quan-tum sensor

Silicon photodiode with filters togive a response between 400 , l, 700 nm

UV radiation Eppley UV radiometer Photometer with bandpass filters 290, l , 380 nm

Shear flow velocity, m∗ Anemometer Computation from wind velocities attwo heights [31]

Temperature, q Temperature sensor TFK530-WTW

Thermocouples

Table 4. Concentration c(H2O2) in rain and wet deposition dw (H2O2), S P 5 total rainfall

Dateand site

S P(L m22)

c(H2O2)(mmolL21)

dw (H2O2)(1023 mmol

m22 s21) Weather situation

20.09.9422.09.9412.10.94

12.11.9413.12.9420.12.94

ChristchurchChristchurchWest Melton 20 km

SW ChristchurchL. HochstetterChristchurchNgatimoti/Nelson

0.22.84.2

22.0

1.45.31.3

27.27.33.9

0.060.460.38

16.60.283.5

Cold front, southwesterly airflowCold front, southerly airflowCold front, southwesterly airflow

Cold front, westerly airflowWeak cold front, southwesterly airflowCold front, southwesterly airflow

Table 5. Formation and decay of H2O2 in surface waters

Lake DOC Dose UV a b k t½ n

SelfeOxbowHayesHochstetterOxidation Pond

1.81.93.97.7

27.5

0.0510.0360.0670.0330.038

2.6 6 0.52.9 6 0.66.2 6 1.1

11.0 6 1.623.0 6 4.2

1.41.51.62.20.84

0.0400.0430.180.450.46

17.3 6 1.916.0 6 4.0

3.9 6 0.52.1 6 0.41.5 6 0.2

1 3 106

1 3 102a

5 3 106

1 3 102

3 3 106

Unit (dose UV) 5 kWh m22; unit (DOC) 5 mg L21; a [ formation yield, unit (a) 5 mmol L21 (kWhm22)21; b [ a DOC21, unit (b) 5 mmol L21 (kWh m22)21 (mg DOC L21)21; k [ decay rate constant, unit(k) 5 h21; unit (t½) 5 h; n [ bacteria concentration, unit (n) 5 cells ml21.

aThe low bacteria concentration may be explained by a rapid exchange of lake water by groundwater withinthe braided river system.

irradiance dose measured at the depth of exposure. The mea-sured UV dose is related to a spectral response of the UVradiometer increasing from 8 to 50% between 290 , l ,320 nm. The maximum response is reached at l 5 330 mmwith 60% from where it decreases to 1% at l 5 386 mm.Spectral data were not available during the studies; thus, theUV dose is related to the instrumental characteristic and canonly be used for the purpose of comparison between the lakesstudied.

I determined apparent first-order decay rates k and asso-ciated half lives t½ of H2O2 from the slope of ln(H2O2) plottedagainst the time [23]. At low c(H2O2) H2O2 was added toreach c(H2O2) ø 0.5 mmol L21 for the decay studies.

For analyzing H2O2 I used the DPD analytical technique[24] in which N,N-diethyl-p-phenylenediamine (DPD) is ox-idized by a peroxidase-catalyzed reaction. The resulting rad-ical cation DPD·1 forms a fairly stable color with absorption

maxima at l 5 510 and 551 nm. Measurements were per-formed immediately after sampling with a field photometer(WTW MPM 3000) with reactions directly in a 5-cm cell.Under field conditions a limit of determination (three timesthe standard deviation of five blank determinations) of XD 50.08 mmol L21 can be achieved.

Water used for reagents and blanks was prepared the daybefore field work by double distillation of deionized water,which was then kept in a dark bottle with a platinum catalyst.Standard H2O2 solution was then made from 30% Perhydrol(Merck, p.a.), the concentration of which was calibrated byUV absorption (e 5 1.08 L mol21 cm21 at l 5 300 nm [25]).The determination of H2O2 was controlled by the standardaddition technique. The DPD method allows the detection ofinterferences of alkylperoxides and other oxidants. In suchcases a blank, in which H2O2 was selectively destroyed, wasmeasured separately. Standard deviations of replicate sam-


Fig. 4. Variation of temperature (q), pH, electric conductivity (k20), DOC and bacterial cells with depth z. Variation of PAR, UV irradiance, andc(H2O2) with time (hours, NZWT, horizontally) and depth (z, vertically). Oxidation Pond, sewage plant of Christchurch, 17.08.94, sunrise: 07.21,sunset: 17.47 NZWT. Note the depth scale! Sampling times and depths are indicated by a ●.

Fig. 5. Variation of UV irradiance and c(H2O2) in z 5 25 cm depthwith time (hours, NZWT and NZST, resp.), Oxbow Lake. 26.08.94,sunrise: 07.08, sunset: 17.47 NZWT. 26.12.94, sunrise: 05.46 andsunset: 21.13 NZST.

ples at the same depth and time were determined as s ø 0.02mmol L21 below and s ø 0.04 mmol L21 above c(H2O2) 50.35 mmol L21. Following the proposal of Sturzenegger [1]I measured dry deposition on water prepared for blanks andbuffered at pH 8 and with c(formaldehyde) 5 1 mmol L21

to mask sulfite anions in a wide open glass vessel in a calmshaded site. All other methods used during this survey areexplained in Table 3.

RESULTS AND DISCUSSION

The vertical and temporal variation of c(H2O2) in lakesresults out of the external input, internal formation and decay,and internal transport processes. However, the contributionof the various terms of an H2O2 balance equation to the patternof temporal and vertical change of H2O2 concentration differconsiderably. I will select those factors that predominantlyinfluence the formation of typical patterns of H2O2 behaviorin lakes within the catena of trophic states as a basis for theinterpretation of those patterns.

External input

In order to estimate the contribution of dry deposition ofH2O2 and wet one caused by rain, I measured the vapor phasedeposition into a wide open glass vessel filled with waterprepared for blanks as described above, and the c(H2O2) inrain.

The mean daytime dry deposition of dd 5 0.23 3 1023

mmol m22 s21 (standard deviation of dry deposition sd 5 0.153 1023 mmol m22 s21) was significantly higher than the meannighttime dry deposition dd 5 0.035 3 1023 mmol m22 s21

(standard deviation of dry deposition sd 5 0.011 3 1023 mmolm22 s21). I could not observe a clear seasonal variation be-tween August and December. Sturzenegger [1] estimated inZurich during September a flux of dry deposition of dd 5 3.53 1024 mmol m22 s21, which lies in the same order of mag-


Fig. 6. (Top) Variation of temperature (q), pH, electric conductivity (k20), DOC, and bacterial cells with depth z. Variation of PAR, UV irradiance,and c(H2O2) with time (hours, NZWT, horizontally) and depth (z, vertically). Lake Selfe, 09.09.94, sunrise: 06.44, sunset: 18.11 NZWT. (Bottom)Variation of temperature (q) and bacterial cells with depth z. Variation of PAR, UV irradiance and c(H2O2) with time (hours, NZST, horizontally)and depth (z, vertically). Lake Selfe, 06.12.94, sunrise: 05.43, sunset: 20.58 NZST.

nitude. This amounts to an insignificant contribution to theH2O2 budget of the lakes.

The contribution of wet deposition dw varies dependingon rainfall intensity and c(H2O2) in rain between 0.06 3 1023

, dw , 16.6 3 1023 mmol m22 s21 (Table 4). Heavy rainfall(S P 5 22 L m22) with high c(H2O2) (e.g., Lake Hochstetter,12.11.94, see Table 4) leads to an increase of c(H2O2) 5 0.4mmol L21 in lake water at a time when the formation rate islow (,0.02 mmol L21 h21) because of low UV irradiance (seeFig. 9, bottom).

Within rainfall events we observe strong temporal andspatial variations of c(H2O2) (see Fig. 2). Jacob et al. [26]and Gunz and Hoffmann [12] present data on H2O2 concen-trations in rain water from midlatitude to tropical regions.

These data indicate an increase in mean concentrations ofH2O2 from midlatitude sites to subtropical and tropical ones.In the case of New Zealand a comparison of the air flowdirection with the concentration of H2O2 in rain providessome evidence that westerly and northwesterly air flow,which however causes rainfall only over lakes at the westcoast, brings rain with higher c(H2O2) than air from the southand west (Fig. 3). I explain this with higher H2O2 concen-tration within air masses coming from the subtropics andtropics than within air masses from the Antarctic. From highUV irradiance caused by higher solar elevation and lowerozone concentration than in midlatitudes I deduce high H2O2

formation in subtropical air. My own data from analyses ofH2O2 in rain at Rarotonga (Cook Islands 1598449E, 218159S,


Fig. 7. Daily march of H2O2 formation rate (mmol L21 h21) and UV irradiance (W m22) near the surface (left side) and variation with depth zof formation rate and UV irradiance around noon in quartz tubes suspended in Lake Hayes, 20.10.94.

7/8.1.1995), which lie between 29 , c(H2O2) , 60 mmol L21

at a total rainfall of S P 5 40 L m22 give some evidence thatwesterly and northwesterly winds originating in the subtrop-ics may contribute to higher wet deposition of H2O2 at thewest coast of New Zealand.

Thus, depending on origin of air flow and location of lake,the contribution of wet deposition of H2O2 can increase theconcentration of H2O2 considerably above levels before onsetof rain (cf. Fig. 9, bottom [11]).

Concentrations of c(H2O2) near the limit of detection ingroundwater demonstrate that groundwater inflow can onlydilute the concentrations of H2O2 in lakes. This conclusioncan also be confirmed by data of Holm et al. [18] who an-alyzed 111 groundwater samples under field conditions andfound extremely low (c(H2O2) 5 0.02 6 0.007 mmol L21)concentrations. I assume that the concentrations of H2O2 willbe further decreased when groundwater is passing reducingsediments.

I investigated the vertical distribution of c(H2O2) awayfrom inflowing creeks. Their input of H2O2 is not known butshould not have had significant influence on the daily patternof H2O2 at the measuring sites.

Internal formation and decay

Intensive earlier studies [1,10] indicate that the predom-inant mechanisms of formation of H2O2 are sunlight-initiatedreactions of humic substances in surface waters. The increaseof formation yield a reflects the increase of formation ofH2O2 with increase of DOC within the various lakes (seeTable 5). Scully et al. [27] found that the relationship betweenH2O2 formation rate and DOC follows a power function. Theformation yield a is not significantly correlated with UVirradiance (r 5 20.3, n 5 6). It must be admitted, however,that DOC exhibits a natural variability with respect to H2O2

formation [10], which was not examined in this study. Fur-ther, the difference between formation yields of Lakes Selfeand Oxbow is not significant. The rate constant b, whichrelates a to the different DOCs, indicates that all b-valueslie within a narrow range (see Table 5). The differences mightbe caused by different composition of DOC and/or the dif-

ferent spectral composition of UV irradiance at different sam-pling times [28].

Cooper and Lean [9] subjected pure strains of bacteria tomicrobial inhibitors, sterilization, filtration through variouspore size filters, and use kinetic analyses for the explanationof the decomposition of H2O2 and then conclude that thebiologically induced decay by bacteria seems to be moreimportant than the chemically induced decay caused by redoxreactions. Comparing the decay rate constant k or the halflife t½ with the bacteria count (Table 5) of the various lakes,I infer that the relationship to bacterial breakdown is lessconclusive from these field data. In particular, the short halflife of H2O2 in the dystrophic Lake Hochstetter with verylow bacteria (n 5 102 cells ml21) concentration provides ev-idence of the importance of chemically induced rather thanbiologically induced decay for at least some surface waters.

In general, the half life of c(H2O2) seems to decrease withthe increase of the DOC concentration and the trophic state.

Because of the variability of the incoming UV irradiance,we observe a distinct daily change of the formation rate (seeFig. 7). Further, the strong absorption of UV irradiance inwater, especially water-rich in humic substances, results ina formation rate that declines with depth (see Fig. 7). Thesefindings are related to the strong correlation of UV irradiancewith H2O2 formation.

The three dominant mechanisms that control the temporaland vertical variation of c(H2O2) in lakes, viz. formation byphotochemical reaction, biological and chemical decay, anddispersion, act together and—due to their individual contri-bution—cause a distinct daily pattern with a near surfacemaximum shifted into the afternoon (see Fig. 5). Lakes witha high extinction by DOC like Oxidation Pond and LakeHochstetter (see Figs. 4 and 9) exhibit a concentration of theformation reactions near the surface, whereas in transparentlakes like Lake Selfe (see Fig. 6, top) H2O2 is formed overa greater depth and thus the near-surface maximum is lessmarked. However, dispersion by light wind or low radiationblur these patterns considerably.

At one occasion a secondary maximum of H2O2 concen-tration in greater depth could be observed (Fig. 6, bottom),which might be explained by horizontal dispersion.


Fig. 8. (Top) Variation of temperature, pH, electric conductivity (k20), DOC, and bacterial cells with depth z. Variation of PAR, UV irradiance,and c(H2O2) with time (hours, NZST, horizontally) and depth (z, vertically). Lake Hayes, 20.10.94, sunrise: 06.33, sunset: 19.57 NZST. (Bottom)Variation of temperature with depth z. Variation of PAR, UV irradiance, and c(H2O2) with time (hours, NZST, horizontally) and depth (z, vertically).Lake Hayes, 22.10.94, sunrise: 06.28, sunset: 08.01 NZST.

H2O2 turnover regimes

The H2O2 turnover in lake water is governed by simul-taneous formation (expressed by the formation yield a) anddecay (expressed by the half life t½ of H2O2). When plottingt½ against a of the various lakes (see Fig. 10), we find lakeswith a low turnover, like oligotrophic Lake Selfe and OxbowLake, which are characterized by a low formation yield a (a

5 2.6 and 2.9 mmol L21 [kWh m22]21, resp.) and a low decay(long half life) (t½ 5 17.3 and 16.0 h, resp.). In contrast onegroup of eutrophic, hypertrophic, and dystrophic lakes, LakeHayes, Oxidation Pond, and Lake Hochstetter, exhibits a highturnover that is attributed to high formation yield (a 5 6.2–23 mmol L21 [kWh m22]21) and high decay (short half life)(t½ 5 3.9–1.5 h) at the same time.


Fig. 9. (Top) Variation of temperature, pH, electric conductivity (k20), DOC, bacterial cells, and c(H2O2) with depth z. Variation of PAR and UVirradiance with time (hours, NZST, horizontally) and depth (z, vertically). Lake Hochstetter, 11.11.94, sunrise: 06.00, sunset: 20.28 NZST. (Bottom)Variation of temperature and c(H2O2) with depth z. Variation of PAR and UV irradiance with time (hours, NZST, horizontally) and depth (z,vertically) in lake water. Wet deposition of H2O2 and concentration of H2O2 at the lake surface (right figure). Lake Hochstetter, 12.11.94. Rainfall,heavy after 10.30 until 14.45.

However, we have to consider that the formation declineswith increasing depth and with greater humic substances con-centrations, whereas the decay rate constant does not changevery much with depth.

The combination of these considerations results in typesof lakes with a low turnover of H2O2 and a formation reachinggreater depths. These characteristics belong to oligotrophic

lakes. On the other hand we find lakes with a high turnovernear the surface and a strong decline of formation with depth.This behavior is typical of hypertrophic, eutrophic, and dys-trophic lakes.

Under equal external (wind and light) conditions the‘‘highturnover’’ lakes show a more clearly structured pat-tern of c(H2O2), especially a steeper vertical concentration


Fig. 10. Turnover regimes of waters of some N.Z. Lakes. a: H2O2

formation yield; t½: Half life of H2O2.

gradient (see Fig. 4, Oxidation Pond) than the ‘‘low-turn-over’’ lakes, which are characterized by a less marked patternand a less steep vertical gradient (see Fig. 6, bottom, LakeSelfe).

Factors like wind-induced mixing (see Fig. 8, top) or ther-mal stratification (during my stay in New Zealand I couldnot observe a case) will of course weaken or strengthen thestructure of the general pattern.

Cooper et al. [13] observed a strong positive correlationbetween the accumulation rates of H2O2 and DOC concen-trations. However, Scully et al. [29] proved that the arealformation rates of H2O2 (integrated over time and depth ofa lake) are independent of DOC.

The authors resolve this apparent contradiction as follows:as the chromophores responsible for H2O2 formation are alsolikely to be the same as those responsible for the attenuationof UV radiation, it is evident that on an areal basis there isno increase in H2O2 with an increase in DOC. The study ofScully et al. [29] makes clear that the total formation of H2O2

in a lake is a function of the formation efficiency of the water(ratio of number of moles of H2O2 formed per mole UV pho-tons absorbed) and the number of photons impinging on thelake surface. It is obvious that the term formation efficiencyof Scully et al. [29] is equivalent to the term formation yieldin this study.

Typical daytime isopleths of c(H2O2) show high concen-trations (0.3 , c(H2O2) , 0.6 mmol L21) during the earlyafternoon near the surface (Figs. 4, 6, and 8). As H2O2 ispredominantly generated by UV light, this pattern has to beexpected and in fact has been found earlier [23]. The initialvertical distribution of H2O2 concentrations before sunriseare a function of vertical dispersion, previous formation, anddecay of H2O2.

Photochemical formation follows a seasonal variation.Due to higher radiation during summer we observe higherc(H2O2) than in winter. This can be very marked, as can beseen from the comparison of daily variation of H2O2 in theshallow Oxbow Lake of clear days in summer and winter(Fig. 5). A similar, but not as marked, difference can beobserved comparing the daily variation of c(H2O2) of earlyspring and early summer in Lake Selfe (Fig. 6a, b). It is notonly that the radiation received at the surface of the lake in

winter is smaller than in summer, but the relative amount ofUVB light decreases in winter.

Internal transport

Vertical mixing smoothes the vertical gradient of c(H2O2)as can be seen from the example of Lake Hayes (Fig. 8a, b):On 20 October 1994 gusty winds with a friction velocity ofm* ø 1 m s21 caused deep mixing of H2O2, and a weak verticalgradient developed only later in the afternoon. This contrastsstrongly with a highly structured pattern 2 d later when thefriction velocity was m* , 0.01 m s21. A similar differencein vertical gradients can be observed in the case of LakeSelfe (Fig. 6a, b). Heavy foehn winds (m* . 1 m s21) turnedover the lake on the morning of 9 September 1994, easingbefore noon. There was only a small gradient of water tem-perature. During 3 h of calm weather after noon, higher con-centrations of H2O2 could be formed near the surface but theywere disturbed after 15.30 by the onset of an anabatic (upval-ley) wind. In contrast, on 6 December 1994 the weather wascalm during the morning, but at noon winds between 0.2 ,m* , 0.5 m s21 caused mixing, and the pattern of strongafternoon gradients could not develop.

Conclusion

Comparing the daily patterns of H2O2 concentrations inlakes of different trophic state it becomes evident that lakeswith a high turnover regime exhibit distinct vertical and tem-poral variation. This can be explained by high formation ratescaused by UV absorption by DOC near the surface and a fastbiological or chemical decay rate. These lakes include eu-trophic Lake Hayes, dystrophic Lake Hochstetter, and hy-pertrophic Oxidation Pond. In contrast lakes with a low turn-over, including oligotrophic Lake Selfe and Oxbow Lake,exhibit a more even distribution of c(H2O2) over time anddepth. This pattern results from a deeper penetration of UVradiation and a lower decay rate.

During turbulent mixing H2O2 will be transported down-ward depending on the vertical mixing depth, thus blurringthe pattern considerably.

It is evident that the governing factors, formation yieldand decay, are not independent from each other: formationyield increases with DOC and decay increases also with DOCas in productive waters, which are also rich in DOC, oneobserves increased biological breakdown. Further, I have ob-served chemically induced decay in dystrophic lakes withhigh concentrations (DOC . 7 mg L21) of DOC.

Acknowledgement—I thank the German Research Council for sup-port of this work. Landcare Research, New Zealand at Christchurch,provided laboratory space, instrumentation, and logistic help. Igratefully acknowledge valuable advice of J. Hunt and help of theChristchurch Landcare staff. J. and N. Newman, put their epiflu-orescence microscope at my disposal. I owe the term formation yieldto an anonymous reviewer. I thank E. Misch and E. Schill for prep-aration of the manuscript and the illustrations.

REFERENCES

1. Sturzenegger, V. 1989. Bildung und Abbau von Wassersto-ffperoxid in belichtetem Oberflachenwasser. Ph.D. thesis.Eidgenossische Technische Hochschule Zurich, Switzerland.

2. Moffett, J.W. and R.G. Zika. 1987. Reaction kinetics of hy-drogen peroxide with copper and iron in seawater. Environ. Sci.Technol. 21:804–810.

3. Martin, J.H. and S.E. Fitzwater. 1988. Iron deficiency limits


phytoplankton growth in northeast Pacific subarctic. Nature331:341–343.

4. Skurlatov, Y. 1990. Effects of solar UV-radiation on hydrogenperoxide content and radical self purification. In N.V. Bloughand R.G. Zepp, eds., Proceedings, Effects of Solar UltravioletRadiation in Biogeochemical Dynamics in Aquatic Environ-ments. Woods Hole, MA, USA, October 23–26, 1989, p. 96.

5. Pardieck, D.L., E.J. Bouwer and A.T. Stone. 1992. Hydrogenperoxide use to increase oxidant capacity for in situ biomedia-tion of contaminated soils and aquifers: A review. J. Contam.Hydrol. 9:221–242.

6. Arana, I., A. Muela, J. Iriberri, L. Egea and I. Barcina. 1992.Role of hydrogen peroxide in loss of culturability mediated byvisible light in Eschericia coli in a freshwater ecosystem. Appl.Environ. Microbiol. 58:3903–3907.

7. Draper, W.M. and D.G. Crosby. 1984. Solar photooxidationof pesticides in dilute hydrogen peroxide. J. Agric. Food Chem.32:231–237.

8. Frimmel, F.H. 1994. Photochemical aspects related to humicsubstances. Environ. Int. 20:373–385.

9. Cooper, W.J. and D.R.S. Lean. 1992. Hydrogen peroxide dy-namics in marine and fresh water systems. In W.A. Nierenberg,ed., Encyclopedia of Earth System Sciences, Vol. 2. Academic,San Diego, CA, USA, pp. 527–535.

10. Cooper, W.J., C. Shao, D.R.S. Lean, A. Gordon and F.E.Scully. 1994. Factors affecting the distribution of H2O2 in sur-face waters. In L.A. Baker, ed., Environmental Chemistry ofLakes and Reservoirs. ACS 237. American Chemical Society,Washington, DC, pp. 391–422.

11. Lean, D.R.S., W.J. Cooper and F.R. Pick. 1994. Hydrogenperoxide formation and decay in lake waters. In G.R. Helz, R.G.Zepp and D.G. Crosby, eds., Aquatic and Surface Photochem-istry. Lewis, Boca Raton, FL, USA, pp. 207–221.

12. Gunz, D.W. and M.R. Hoffmann. 1990. Atmospheric chem-istry of peroxides: A review. Atmos. Environ. 24A:1601–1633.

13. Cooper, W.J., R.G. Zika, R.G. Petasne and A.M. Fischer.1988. Sunlight induced photochemistry of humic substances innatural waters: Major reactive species. In P. McCarthy and I.H.Suffet, eds., Influence of Aquatic Humic Substances on Fate andTreatment of Pollutants. ACS 219. American Chemical Society,Washington, DC, pp. 333–362.

14. Cooper, W.J. and R.G. Zepp. 1990. Hydrogen peroxide decayin waters with suspended soils: Evidence for biologically me-diated processes. Can. J. Fish. Aquat. Sci. 47:888–893.

15. Zepp, R.G., Y.I. Skurlatov and J.T. Pierce. 1987. Algal- in-duced decay and formation of hydrogen peroxide in water. Itspossible role in oxidation of anilines by algae. In R.G. Zika andW.J. Cooper, eds., Photochemistry of Environmental AquaticSystems. ACS 327. American Chemical Society, Washington,DC, pp. 215–224.

16. Jacob, P. 1987. Wasserstoffperoxid in der atmospharischenGas-und Flussigphasenchemie: Laborstudien und Felduntersu-chungen. Ph.D. thesis. University of Dortmund, Dortmund, Ger-many.

17. Klockow, D. and P. Jacob. 1986. The peroxyoxalate chemi-

luminescence and its application to the determination of hy-drogen peroxide in precipitation. In W. Jaeschke, ed., Chemistryof Multiphase Atmospheric Systems. NATO ASI Series G 6.Springer-Verlag, Berlin, Germany, pp. 117– 130.

18. Holm, T.R., G.K. George and M.J. Barcelona. 1987. Fluo-rometric determination of hydrogen peroxide. Anal. Chem. 59:582–586.

19. Timperley, M.H. 1987. Regional influences on lake waterchemistry. In A.B. Viner, ed., Inland Waters of New Zealand.Science Information Publishing Centre, Wellington, New Zea-land, pp. 97–111.

20. Viner, A.B. and E. White. 1987. Phytoplankton growth. In A.B.Viner, ed., Inland Waters of New Zealand. Science InformationPublishing Centre, Wellington, New Zealand, pp. 191–223.

21. Mitchell, S.F. and C.W. Burns. 1981. Phytoplancton photo-synthesis and its relation to standing crop and nutrients in twowarm- monomictic South Island lakes. N.Z. J. Mar. FreshwaterRes. 15:51–67.

22. Paerl, H.W., G.W. Payne, A.L. Mackenzie, P.E. Kellar andM.T. Downes. 1979. Limnology of nine Westland beech forestlakes. N.Z. J. Mar. Freshwater Res. 13:47–57.

23. Cooper, W.J., D.R.S. Lean and J.H. Carey. 1989. Spatial andtemporal patterns of hydrogen peroxide in lake waters. Can. J.Fish. Aquat. Sci. 46:1227–1231.

24. Bader, H., V. Sturzenegger and J. Hoigne. 1988. Photometricmethod for the determination of low concentrations of hydrogenperoxide by the peroxidase catalysed oxidation of N,N-diethyl-p-phenylendiamine (DPD). Water Res. 22:1109–1115.

25. Zepp, R.G., Y.I. Skurlatov and L.F. Ritmiller. 1988. Effectsof aquatic humic substances on analysis for hydrogen peroxideusing peroxidase- catalyzed oxidations of triarylmethanes or p-hydroxyphenylacetic acid. Environ. Technol. Lett. 9:287–298.

26. Jacob, P., T.M. Tavares, V.C. Rocha and D. Klockow. 1990.Atmospheric H2O2 field measurements in a tropical environ-ment: Bahia, Brazil. Atmos. Environ. 24A:377–382.

27. Scully, N.M., D.R.S. Lean, D.J. McQueen and W.D. Cooper.1996. Hydrogen peroxide formation: The interaction of ultra-violet radiation and dissolved organic carbon in lakewatersalong a latitude (43–758N) gradient. Limnol. Oceanogr. (inpress).

28. Scully, N.M. and D.R.S. Lean. 1994. The attenuation of ultra-violet radiation in temperate lakes. Arch. Hydrobiol. Beih. Er-geb. Limnol. 43:135–144.

29. Scully, N.M., D.R.S. Lean, D.J. McQueen and W.D. Cooper.1996. Photochemical formation of hydrogen peroxide in lakes:Effects of dissolved organic carbon and ultraviolet radiation.Can. J. Fish. Aquat. Sci. (in press).

30. Porter, K.G. and Y. Feig. 1980. The use of DAPI for identifyingand counting aquatic microflora. Limnol. Oceanogr. 25:943–948.

31. Monteith, J.L. 1978. Grundzuge der Umweltphysik. Steinkopf,Darmstadt, Germany, pp. 1–183.

32. De Lisle, J.F. and M.L. Browne. (no year). The climate andweather of the Otago Region, New Zealand. New Zealand Me-teorological Service Miscellaneous Publication 115.

Documents

The daily changing pattern of hydrogen peroxide in new zealand surface waters