picked up by the wind. Juang and Johnson^ present data showing that part of 

 the chloride leaving a small watershed in northern New England likely comes 

 from dr>' fallout. Based on Figure 1, Jackson^, Juang^ and Pearson and Fisher, 10 

 the author believes 0.5 mg/£, is a reasonable estimate for average chloride 

 reaching land surface in New Hampshire. 



Igneous, Metamorphic and Sedimentary Rocks 



Few rocks with the exception of evaporites are likely to contain much 

 chloride within theirstructures. ^ Evaporite deposits are derived by evaporation 

 of sea and lake water usually in closed basins. Marine evaporites in particular are 

 likely to be extensive and high in chloride. Therefore, water associated with 

 these rocks will also be high. For example, the Pecos River receives a 

 considerable increment of chloride from evaporites in southeastern New 

 Mexico. 12 A consideration of regional geology should show whether evaporites 

 are likely to be present in any particular area. For example, they are not present 

 in New England. 



Concentrations in sedimentary, igneous and metamorphic rocks range from 

 15 mg/£ for sandstone up to 300 or more for shale. 13 Rock dissolution or 

 weathering will produce only very small concentrations in surface or ground 

 water although over time the accumulation may be large. Metamorphic rock 

 weathering is only a minor source in one small watershed in New Hampshire. 14 

 Chloride entrapped in sedimentary rocks leaving or entering after deposition can 

 be a significant item, and this will be discussed in the section on saline water. 



Saline Water 



Saline water may either be entrapped in sedimentary rocks during deposition 

 or may enter later. The former is probably most common in sandstone and shale 

 whereas the latter may occur in almost any rock near saline water. Two good 

 examples are brines found associated with petroleum deposits and sea-water 

 propagated inland by tides. The question of presence of brines is best answered 



Juang & Johnson, Cycling of Chlorine through a Forested Watershed in New England, 72 

 J. Geophysical Research 5641-5647 (1967). (hereinafter cited as Juang). 



^JACKSON. 



9 

 Juang. 



^°F. J. PEARSON, JR. & D. W. FISHER, CHEMICAL COMPOSITION OF ATMOS- 

 PHERIC PRECIPITATION IN THE NORTHEASTERN UNITED STATES (U.S. 

 Geological Survey Water-Supply Paper 15 35-P, 1971). 



Johns & Huang, Distribution of chlorine in terrestrial rocks, 31 Geochimica et 

 Cosmochimica Acta 35-49 (1967). 



l^HEM 174. 



l^Id. 171. 



Juang. 



