are in the oxyanion forms (that is, bound to oxygen atoms). For instance, dissolved Se may exist 

 as H SeO or HjSeO^, and any of the conjugate forms. Organic methylated forms of Se may also 

 be present in significant quantities tmd are included along with the oxyanions in the reported 

 total concentration value. The speciation of each element is essential in conclusively determin- 

 ing the fate and toxicological impact. 



Boron concentrations are generally in the order of mg/L while the other three trace 

 elements are present in the order of )ig/L. An extremely high level of B (226.9 mg/L) was observed 

 in cell 2 of Pryse pond in August 1988 compared to the 3 year average of 70.60 mg^. The 

 conservancy (i.e., non-reactivity) of B is well illustrated by the similarity in the rise of CI" and 

 B concentrations, each almost showing a ten fold increase. 



Selenium concentrations are below quantitation levels at Barbizon pond while it is 

 barely detectable at Pryse pond and occasionally exceeds 1 mg/L at Peck pond especially in cell 



5. 



Arsenic concentrations greater than 1 mg/L have been detected in Pryse and Barbizon 

 pond waters while the highest concentration at Peck pond is 0.95 mg/L which was found in one 

 inflow sample. The highest pond water As concentration at Peck pond is 0.84 mg/L and this was 

 during the time the pond cell was being drained to dryness. Concentrations exceeding 2 mg/L 

 were found for Mo in many samples from all ponds. Additionally, Pryse inflow and pond waters 

 showed extremely high levels of Mo rangingfrom a minimum of L40 mg/L in inflow to 24.51 mg/ 

 L in cell 2. While other solute concentrations in the pond water decreased with the lowering of 

 the degree of salinity as indicated by a 58.3 dS/m drop in EC, Mo increased from the previous 

 season because of a greater than three-fold increase in the inflow water Mo concentration. 



It should be noted that the analytical data reported for As and Mo, as determined by the 

 ICP, are consistently higher than those reported by the CVRWQCB and DWR for the period 1986- 



88 (Personal communication, D. Westcot and S. Ford). The extent of the data discrepancies 

 varied depending on the element and pond. Despite the differences, the database is subsequently 

 used in section 6 of this report because the error appears systematic rather than random. 



The presence of trace elements in the drainage waters and consequently pond waters 

 may be associated with the distribution of trace elements in the San Joaquin Valley. Bradford 

 et al., (1989a) have reported on the distribution of 20 trace elements on the basis of three geologic 

 regions: the Alluvial Fan (AF) region, the Basin Rim (BR) region and the Lakebed (LB) region 

 (Table 2.2). Peck pond is situated in the AF region while Barbizon pond is in the BR region and 

 Pryse pond in the LB region. Of the four trace elements of interest here, the AF region is high 

 inB,MoandSe. The BRregionishigh in B only, and the LB region is high in As, Band Mo. These 

 observations are mostly consistent with the regional dominance of certain trace elements in 

 different ponds: B is high in all ponds; Se is high at Pryse pond; As and Mo are relatively 

 dominant in Pryse pond. 



Table 2^ Distribution of Trace Elements in the San Joaquin Valley 

 (L = low, M = moderate, H = high) 



REGION As B Mo Se_ 



Alluvial Fan L H M H 



Basin Rim L M L L 



Lakebed H H H L 



page 2.3 



