Analysis of surface water and groundwater nitrate sources in Binzhou City in the Yellow River Delta using isotopes of nitrogen and oxygen

The Yellow River Delta area is well developed in both agriculture and industry, but with frequent nitrate pollution in surface water and groundwater．δ(¹⁵N) and δ(¹⁸O) isotopic tracing of nitrate was used in the present study to identify major pollution sources in Binzhou City．Nitrate concentrations in surface water and groundwater was found to range from 0 to 168.07 and 0 to 336.04 mg·L⁻¹, with a over-standard rate of 8.70% and 27.78%, respectively．Surface water nitrate pollution became more serious down the river, nitrate concentrations in groundwater fluctuated greatly as well．δ(¹⁵N-NO₃) was found to range in surface water and groundwater from 4.02‰-10.10‰ and 9.07‰-18.75‰, δ(¹⁸O-NO₃) from 2.24‰-6.14‰ and 4.93‰-10.64‰, respectively．Manure and septic waste were found to be the major sources of nitrate pollution both in surface water and groundwater, with a contribution rate of 45% and 81%, respectively．Artificial N fertilizer was the second largest source of nitrate pollution in surface water and groundwater, with a contribution rate of 26% and 17%, respectively．These data will be helpful when making policies to prevent nitrate pollution in surface water and groundwater in the Yellow River Delta．