Atmospheric Environment Pergamon Press 1973. Vol. 7, pp. 587-588. Printed in Great Britain.

SHORT COMMUNICATION

K R A F T M I L L F A L L O U T A N D G R O U N D B E E T L E P O P U L A T I O N S

(First received 16 October 1972 and in final form 15 November 1972)

Abstraet--A negative correlation is found between the rate of fallout of SO42- and size of ground beetle populations near a kraft mill in Thunder Bay, Ontario, Canada.

MEASUREMENTS of SO42- fallout, probably in the form of Na2SO4, were made in the vicinity of a kraft mill near Thunder Bay, Ontario, in the winter of 1970-1971 and following summer (I-IASrlNGS et al., 1971 ; HASTINGS and FREITAG, 1972). During the summer of 1971 ground beetle populations in the same area were studied concurrently (FREITAG et al., 1973). A comparison of tbe data obtained in the three studios is presented here.

Details of the methods used in determining the rate of fallout and relative sizes of beetle populations are given in the above references and thus we need only outline them. The rate of fallout of SO, 2- was obtained along a transit running west or mainly downwind from the mill. The fallout rate during the winter was determined from the total accumulated concentration of SO4 z- found in snow samples. During the summer, rainwater was allowed to accumulate in tubs and was periodically analyzed for SO42 = concentration. Based on these data the average rate of fallout of S O ~ - as a function of distance from the mill was calculated.

The beetle populations were sampled by five pitfall trap stations each comprising 100 traps and located on the same transit used to collect the fallout. In all, 21 species of beeries were collected. Twenty species were members of the Family Carabidae (ground beetles), and one species was of the family Silphidae (carrion beetles).

40,

ol ~'3o

~ 2 0 o

o

IO O

O

• O

0

• Fallout 0 Beetles

I I I I 0 500 I000 1500 2000

Distance f rom mi l l , y

O I000

800

• 600

4 0 0

z

2 0 0

! 2500 3000

FiG. 1. Composite plot of average annual 1970-1971 SO42- fallout and size of summer 1971 beetle population samples versus distance from a kraft mill in Thunder Bay, Ontario.

FIGURE 1 is a composite plot showing both the average annual rate of fallout of SO42- (solid discs) and the total number of beetles collected (circles) at each station as functions of distance from the mill. The left ordinate represents the rate of fallout in mg m -2 per day, and the fight, the number of beetles trapped.

587

588 R. FREITAG and L. HASTINGS

It can be noted from FIG. 1 that the average rate of fallout generally decreased with increasing distance from the mill. There is evidently a slight increase in the rate of fallout for the two determina- tions furthest from the mill. The beetle population samples indicate a marked increase in population size with distance from the mill. While there appears to be a negative correlation between fallout and size of beetle population, the increase in fallout for the furthest distances used is not reflected in the size of the beetle samples obtained there.

In summary it may be concluded that fallout from the kraft mill effectively reduces the size of ground beetle populations near the mill. The toxic agent may either be SO42 - or some other particulate compound released into the air from the kraft mill flue stack.

The toxicity of such substances to ground beetles, and indeed the general sensitivity of ground beetles to air pollution are areas of research in which little has been done. As a method of measuring environmental alteration due to air pollution systematic pitfall trap collecting of ground beetles to determine population sizes seems a promising quantitative tool.

Lakehead University R. FRE1TAG* Thunder Bay L. HASTINGS'[" Ontario, Canada

* Department of Biology. Department of Physics.

R E F E R E N C E S

FREITAG R. and HASTINGS L. (1973). Ground beetle populations near a kraft mill. Can. Entomol. (In press).

HASTINGS L., FREITAG R. and SMITI-I A. (1972). Fallout of sodium sulphate near a kraft mill. Atmospheric Environment 6, 241-246.

HASTINOS L. and FREITAG R. (1972). A comparison of summer and winter fallout of sodium sulphate near a kraft mill. Atmospheric Environment 6, 947-948.