Regional Groundwater Hardness and Silicon, Cropland Fertility and CHD in Finland

The status of silicon (Si) in agriculture, veterinary and human medicine is not clear. This survey is based on old data, but groundwater (from springs and dugwells) data have been newly classified by 21 Rural Centers (RC). RC CHD has been estimated by provincial data. The aim of this paper is to clarify associations between CHD mortality, groundwater (GW) hardness (Ca+Mg), Si.gw, cropland (soil) (Ca+Mg) a measure of soil fertility and, pH and temperature (Temp) with regional parameters [latitude (Lat), longitude (Long)]. Regressions are given separately for the whole Finland (“21.RC”) and continental Finland (“20.RC”), i.e. without Åland the only RC with pH.soil > 6.2. Directions of trend lines of variables have been approximated. Results: CHD regressions by Si.gw, by (Ca+Mg).gw and by (combined) [Lat; Long], (Ca+Mg).gw regressions by (Ca+Mg).soil and by [Lat; Long] and, Si.gw regressions by (Ca+Mg).gw, by [Lat; Long], by [Temp;(Ca+Mg).soil] and by [Temp;pH.soil] have been computed. In RC.20 all associations were significant (p < 0.018). In RC.21 all regressions without Si.gw were stronger than in RC.20, but by including Si.gw associations were weaker with one exception: [Temp; pH.soil] explained Si.gw stronger than in RC.20. The approximated CHD trend line angle was smaller than the respective angles of Si.gw and (Ca+Mg). Conclusion: In RC.20, where soil pH was below 6.2, Si.gw and (Ca+Mg).gw were highly positively inter-correlated and soil fertility could be predicted by regional Si.gw. In RC.20 regression by Si.gw explained better CHD than by (Ca+Mg).gw. Supposedly the health effects of Si could be mediated directly through (soluble) Si in soil and via factors associated with (Ca+Mg). In regional gw analyses the effect of (mother earth) pH needs attention. Table 1: Location, soil and groundwater Ca, Mg and soil pH of Finnish Rural Centers. Location, soil and groundwater Ca, Mg and soil pH of Finnish Rural Centers Central Commune/ Town CHD Latitude Longitude Ca.soil Mg.soil K.soil Ca.gw Mg.gw pH.soil Temperature


Introduction
The role of silicon as a protective mineral element against biotic and a biotic stresses is not generally known [1] in spite of increasing data. Weak plant, animal and human tissues are vulnerable to bacteria, fungi, parasites and degeneration. In the common medical practice associations of Si is in general known as an inert or harmful (by its crystals). The aim of this study is to assess associations between regional CHD mortality, cropland parameters, gw hardness and (soluble) silicon, temperature and geographic location, in order to find, whether Si could explain the "hard water effects".

Materials and Methods
Groundwater parameters are from Groundwater database © Geological Survey of Finland 2017 [2] as in my earlier publications.
They are newly grouped by 21 Rural Centers (earlier Agricultural Advisory Centers). Soil values are from Viljavuuspalvelu Eurofins Oy [3] concerning only from period 1986-90. CHD mortality data of middle-aged men are from Valkonen and Martikainen (1990) [4] and their RC values are estimated as earlier in [5]. Latitude and longitude of each RC have been determined in two-phases: first by selecting approximately a central commune/town of each RC in the map [6] and then by opening its internet page, which gave the latitude and longitude of its center. Temperatures are approximated visually by the map [6] and the map of Finnish meteorogical institute [7]. Åland is in some registers a part of Finska Hushållningssällskapet. That's why "04.b" label has been given for it. The benefited data are in Table 1. Mean number of GW samples per RC was ca 35, SD ca 21.5. From "04.a Finska Hushållningss." were available only 2 or 3 samples, from "04.b Åland" 6 samples, from "16 Österbottens Svenska" 11 samples and from "06 Pirkanmaan" 13 samples. Low number of samples can cause big statistical error, but anyhow the RC springs and dugwells represent larger areas than single cropland samples. Number of cropland samples was ca 620,000 [8]. Regressions were calculated by IBM SPSS. Direction of geographic trend vectors for CHD, gw Si and gw (Ca+Mg) are estimated by tangent function of Excel by the coefficients of latitude ("c.lat") and longitude ("c. long") from the combined regressions. Because 10 ⁰E (longitude) responds only ca 5 ⁰N (latitude) in kilometers "c. long" has been divided by 2. So vector angle in radians = ATAN2 (½*c.long;c.lat). "In Fig. 5 -8 values of angles are given in degrees."

Discussion
(Ca+Mg) of cropland can be seen as a measure of soil fertility, because cropland (Ca+Mg) and (Ca+Mg+K) are generally highly associated (R square > 0.95, from Table 1). Åland was the only RC, where mean (Ca+Mg).gw (1,48 mmol/L) (Table 1) exceeded the lower limit of "hard water" (1.21 mmol/L, i.e. = 2.42 mEq/L) [9]. In Åland CHD mortality was the lowest in Finland (Table 1). Only in Åland the mean soil pH (6.31) (Tabl.1) was within the carbonate buffer range (over 6.2) [10] ( Table 2). This could explain low "soluble" Si, possibly without indicating as low Si availability to plants. The soil pH in the immediate vicinity of the plant roots can be different to those from soil analyses. It can be in silicate buffer range, although macroscopic pH is in the carbonate buffer range. In combined regression by [Temp; pH.soil] pH increase indicated decrease in Si.gw, too (Table 3).   [11]. Possibly because of mother soil included clay soil-types, too. Anyhow Mg deficiency is known to be very uncommon on carbonate soils [12], possibly because of different micro-milieu of roots. In Åland GW Si content (0.68 mEq/L) was below the inter-RC mean (0.98) (Table1). In the UK hard water Si (1.15 mEq/L) was 2.3-fold to the soft water content [11]. This can be dependent on e.g. statistical error (in Finland) and/or mixture of different mother soil-types in the UK. Post-glacial earth elevation [13,14] (Figure 15) can partially explain the soil juvenility of the western Finnish regions. Lower Nordic values can additively be explained by lower temperature, which is associated not only with weathering activity, but some more rapid inorganic phenomenons, too ( Figure 15). 10,000 years erosion, temperature and soil history can explain mortality and mineral element gradient towards northeast ( Figure 15) is skizze from [13].

Conclusion
In RC.20, where soil pH was below 6.2, Si.gw and (Ca+Mg).gw were highly positively inter-correlated and soil fertility could be predicted by regional Si.gw. In RC.20 regression by Si.gw explained better CHD than by (Ca+Mg).gw. Supposedly the health effects of Si could be mediated directly through (soluble) Si in soil and via factors associated with (Ca+Mg). In regional gw analyses the effect of (mother earth) pH needs attention.