Investigation of N and P Non-Point Source Pollution Status of Vegetable Fields in the Suburb of Fuzhou City

N and P non-point source pollution status of vegetable fields in the suburb of Fuzhou city was evaluated by testing samples of vegetable (120 samples), soil surface water (16 samples) and groundwater (11 samples) collected from 14 pieces of vegetable fields which were located at the suburb of that city according to the related criteria in this paper. Results showed that (1) Proportions of vegetable samples of which nitrate content fell into serious pollution level (NO₃^- ≥3 100 mg·kg^-1), heavy pollution level (NO₃^- ≥ 1 440 mg·kg^-1) and moderate pollution level (NO₃^- ≥ 785 mg·kg^-1) were 13.33%, 32.5% and 50.83%, respectively. (2) Proportions of soil surface water samples of which ammonia nitrogen content was beyond the water quality criteria of Grade III (1 mg L^-1) and Grade V (2 mg L^-1) were 62.5% and 56.25% in vegetable field, respectively. The proportion of soil surface water samples of which nitrate nitrogen content was beyond the water quality criterion of the national centralized drinking water standards for surface water (10 mg L^-1) was 12.5% in vegetable field. Compared with the surface water quality criteria of Grade V (2 mg N L^-1, 0.4 mg P L^-1), the average and maximal total N, P content of soil surface water samples of vegetable were 10.99 and 33.80 mg L^-1, 4.75 and 12.75 mg L^-1, respectively. (3) The proportion of vegetable field groundwater samples of which ammonia-N content was beyond the water quality criteria of Grade V (0.5 mg·L^-1) was 18.18%. Proportions of groundwater samples of which nitrate content was super-scale (≥10 mg L^-1) and serious super-scale (≥20 mg L^-1) were 54.55% and 27.27%, respectively. The content of total N of all groundwater samples detected was beyond the water quality criteria of Grade V (2 mg N L^-1, GB3838-2002). And the proportion of vegetable field groundwater samples of which total P content was beyond the water quality criteria of Grade V (0.4 mg P L^-1, GB3838-2002) was 81.82%.