Widespread anthropogenic nitrogen in the northwestern Pacific Ocean sediment

Sediment samples from the East China and Yellow seas collected adjacent to continental China were found to have lower delta N-15 values (expressed as delta N-15 = [N-15:N-14(sample)/N-15:N-14(air) - 1] x 1000; the sediment N-15:N-14 ratio relative to the air nitrogen 15N:14N ratio). In contrast, the Arctic sediments from the Chukchi Sea, the sampling region furthest from China, showed higher delta N-15 values (2-3 higher than those representing the East China and the Yellow sea sediments). Across the sites sampled, the levels of sediment delta N-15 increased with increasing distance from China, which is broadly consistent with the decreasing influence of anthropogenic nitrogen (N-ANTH) resulting from fossil fuel combustion and fertilizer use. We concluded that, of several processes, the input of N-ANTH appears to be emerging as a new driver of change in the sediment delta N-15 value in marginal seas adjacent to China. The present results indicate that the effect of N-ANTH has extended beyond the ocean water column into the deep sedimentary environment, presumably via biological assimilation of N-ANTH followed by deposition. Further, the findings indicate that N-ANTH is taking over from the conventional paradigm of nitrate flux from nitrate-rich deep water as the primary driver of biological export production in this region of the Pacific Ocean.112Nsciescopu

Increase in anthropogenic mercury in marginal sea sediments of the Northwest Pacific Ocean

2

Increase in anthropogenic nitrogen and mercury in marginal sea sediments of the Northwest Pacific Ocean

1

Widespread Anthropogenic Nitrogen in Northwestern Pacific Ocean Sediment

Sediment samples from the East China and Yellow seas collected adjacent to continental China were found to have lower δ¹⁵N values (expressed as δ¹⁵N = [¹⁵N:¹⁴N_sample/¹⁵N:¹⁴N_air – 1] × 1000‰; the sediment ¹⁵N:¹⁴N ratio relative to the air nitrogen ¹⁵N:¹⁴N ratio). In contrast, the Arctic sediments from the Chukchi Sea, the sampling region furthest from China, showed higher δ¹⁵N values (2–3‰ higher than those representing the East China and the Yellow sea sediments). Across the sites sampled, the levels of sediment δ¹⁵N increased with increasing distance from China, which is broadly consistent with the decreasing influence of anthropogenic nitrogen (N^ANTH) resulting from fossil fuel combustion and fertilizer use. We concluded that, of several processes, the input of N^ANTH appears to be emerging as a new driver of change in the sediment δ¹⁵N value in marginal seas adjacent to China. The present results indicate that the effect of N^ANTH has extended beyond the ocean water column into the deep sedimentary environment, presumably via biological assimilation of N^ANTH followed by deposition. Further, the findings indicate that N^ANTH is taking over from the conventional paradigm of nitrate flux from nitrate-rich deep water as the primary driver of biological export production in this region of the Pacific Ocean