2949775650

46

H. Maruszczak, M. Wilgat

SYt — total solute yield: 65.01 km^-2y^_1 — 100%

SYp — solute yield from precipitation: 9.01 km^_^y^{_ 1} — 13.8%,

SYch — solute yield from agricultural Chemicals, i.e. mainly from

fertilizers: 6.5 t km^-2y^-1 — 10.0%,

^J _0 _ 1

SYfs — solute yield from farm sewage: 1.0 t km y — 1.5%,

SYmis — solute yield from municipal and industrial wastewater:

18.2    t km^-2y^-1 — 28.0%,

SYd    — solute yield from Chemical denudation of the lithosphere:

30.3    t km^-2y^-1 — 46.6%.

Our supplementary explanation of the symbols is as follows: The component SYp now mainly contains "synthetic" substances produced by man; the index for these substances should be estimated at least 61 km^-2y^_1. The component SYmis contains not only "synthetic" substances, but also natural ones (pumped with groundwaters used by man). In the previous paper it was assumed that these natural substances accounted for almost half of the solutes coming from municipal and industrial wastewater. The data concerning upland areas were the basis for this estimation. Probably it was overestimated because solute concentration of groundwaters in other landscape belts of the Vistula river basin is not so high. Therefore, we assume now that in 18.2 t km^-2y^-1 of the solutes coming from municipal and industrial wastewater "synthetic" substances account for at least 10 t km^y^-1.

So, the amount of "synthetic" substances representing environmental pollutants can be estimated at about 23.5 t knr^jr¹ in the discussed period, that makes 36% of the total ąuantity of solutes transported by the Vistula river to the sea.

Between the two World Wars, the percentage of "synthetic" substances was many times lower with a considerably lower total solute yield. We can deduce the index of the total solute yield from the Vistula river basin in the 30’s from a few data published by M. Stangenberg (1958). Unfortunately, no information about the level of solute concentration in the Vistula river mouth has been given in this paper. We can estimate this value only on the basis of the series of solute concentration measurements on the Vistula river at Puławy in 1952; the average amounted to 256 mg dm^-3 at that time. In the 30’s, this index was probably even lower; such a conclusion can be drawn unequivocally on the basis of comparison of the content of chlorides in the Vistula river water at Warsaw. In 1934 it was 14.4 mg dm^-3, in 1948 — 16.5, and in 1952 — about 29 mg dm^-3 (Stangenberg 1958). Therefore, we can assume that before World War II the average solute concentration of the Vistula river water at Warsaw did not exceed 24 mg dm^{- 3}.⁽²⁾ Downstream of Warsaw

n    _n

The deduced index of solute concentration at the mouth of the Vistula river in 1934 (240 mg dm ) falls in the rangę of the measurement data of solute concentrations near the Warsaw Water Works, obtained ten years

_ n

earlier and eleven years later. Analyses carried out by T. Kirkor in 1924 gave 215 mg dm on average, with

—3    —3

extreme values of 136 and 283 mg dm , and analyses from 1945 — 258 mg dm , with extreme values of 172 and

_n

358 mg dm (see Dojlido and Woyciechowska 1985, p. 43).