NRCVAX is a complete system ~af programs, covering all aspects of crystal structure analysis from data reduction to the presentation of results. The system, which is written in a 'neutral' Fortran 77, presently exists in two forms. The first runs on a VAX computer under VMS, on an 80386 PC under UNIX and under IBM VM/CMS and MVS/TSO. The second is an adaptation which runs on PC-XT, AT, PS/2 and comparable microcomputers under MS-DOS. The two versions differ somewhat in structure, but very little in code, operation or functionality except for the graphics. The many options of the programs can be selected in a highly interactive manner and because of this the System is very flexible. Most options are assigned default values, however, and it is usually safe to run the routines with a minimum of user input using the defaults. The system will accept data from a wide variety of sources and has interface routines for several other systems. Graphics in the VAX/UNIX version are based on the widely available Tektronix 4000 series protocol, while the microcomputer version supports most common display adapters. It is also possible to prepare files for a variety of plotters, dot-matrix printers and laser printers.• Source code is distributed and it should not be difficult to adapt the system to any computer with virtual memory and a Fortran 77 compiler.

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Atmospheric deposition of polycyclic aromatic compounds (PACs) via and onto snow, and their releasing during spring snowmelt has been a concern in the Athabasca Oil Sands Region of Alberta. This study was designed to evaluate the concentrations, loadings, and distribution of PACs in springtime snowpack and how they have changed since the first study in 2008. Snowpack samples were collected in late winters 2011-2014 at varying distances from the main developments. PAC concentration and deposition declined exponentially with distance, with pyrenes, chrysenes, and dibenzothiophenes dominating the distribution within the first 50 km. The distribution of PACs was different between sites located close to upgraders and others located close to mining facilities. Overall, PAC loadings were correlated with priority pollutant elements and water chemistry parameters, while wind direction and speed were not strong contributors to the variability observed. Total PAC mass deposition during winter months and within the first 50 km was initially estimated by integrating the exponential decay function fitted through the data using a limited number of sites from 2011 to 2014: 1236 kg (2011), 1800 kg (2012), 814 kg (2013), and 1367 (2014). Total loadings were estimated to have a twofold increase between 2008 and 2014, although the increase observed was not constant. Finally, kriging interpolation is presented as an alternative and more robust approach to estimate PAC mass deposition in the area. After a more intensive sampling campaign in 2014, the PAC mass deposition was estimated to be 1968 kg.

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