We comprehensively compile and review N content in geologic materials to calculate a new N budget for Earth .
Using analyses of rocks and minerals in conjunction with N-Ar geochemistry demonstrates that the Bulk Silicate Earth ( BSE ) contains \sim 7 \pm 4 times present atmospheric N ( 4 \times 10 ^ { 18 } kg N , or PAN ) , with 27 \pm 16 \times 10 ^ { 18 } kg N. Comparison to chondritic composition , after subtracting N sequestered into the core , yields a consistent result , with BSE N between 17 \pm 13 \times 10 ^ { 18 } kg to 31 \pm 24 \times 10 ^ { 18 } kg N. Embedded in the chondritic comparison we calculate a N mass in Earth ’ s core ( 180 \pm 110 ~ { } \textrm { to } ~ { } 300 \pm 180 \times 10 ^ { 18 } kg ) as well as present discussion of the Moon as a proxy for the early mantle .

Significantly , our study indicates the majority of the planetary budget of N is in the solid Earth .
We suggest that the N estimate here precludes the need for a “ missing N ” reservoir .
Nitrogen-Ar systematics in mantle rocks and primary melts identify the presence of two mantle reservoirs : MORB-source like ( MSL ) and high-N. High-N mantle is composed of young , N-rich material subducted from the surface and identified in OIB and some xenoliths .
In contrast , MSL appears to be made of old material , though a component of subducted material is evident in this reservoir as well .

Taking into account N mass and isotopic character of the atmosphere and BSE , we calculate a \delta ^ { 15 } N value of \sim 2 \permil .
This value should be used when discussing bulk Earth N isotope evolution .
Additionally , our work indicates that all surface N could pass through the mantle over Earth history , and in fact the mantle may act as a long-term sink for N. Since N acts as a tracer of exchange between the atmosphere , oceans , and mantle over time , clarifying its distribution in the Earth is critical for evolutionary models concerned with Earth system evolution .
We suggest that N be viewed in the same light as carbon : it has a fast , biologically mediated cycle which connects it to a slow , tectonically-controlled geologic cycle .