mid_collection_date  bulk_d15N_500m  bulk_d15N_1500m  bulk_d15N_3200m  
2009-11-30           -999            -999             1.60             
2009-12-15           3.80            1.87             2.00             
2009-12-29           2.68            3.53             2.19             
2010-01-12           2.31            1.49             1.40             
2010-01-26           2.27            0.69             0.91             
2010-02-09           2.93            0.15             0.64             
2010-02-23           1.07            3.73             1.20             
2010-03-09           -0.17           -0.55            0.56             
2010-03-23           -999            -0.60            -0.22            
2010-04-06           -999            0.19             -0.09            
2010-04-22           -999            1.79             1.57             
2010-05-07           3.20            1.92             1.03             
2010-05-22           3.53            1.40             1.53             
2010-06-05           4.02            1.56             1.40             
2010-06-20           3.30            1.23             1.69             
2010-07-05           3.70            2.06             1.43             
2010-07-22           3.50            3.53             2.35             
2010-08-06           -999            1.86             2.61             
2010-08-21           1.99            2.23             2.41             
2010-09-05           3.34            2.93             1.62             
2010-09-20           2.23            4.32             2.55             
2010-10-05           3.24            1.91             2.09             
2010-10-19           4.06            2.47             1.75             
2010-11-02           3.54            2.56             1.62             
2010-11-16           4.66            5.12             2.32