Determination of the Source of Bioavailable Sr Using ⁸⁷Sr/⁸⁶Sr Tracers: A Case Study of Hot Pepper and Rice

The geographical origin of agricultural products has been intensively studied, but links between agricultural products and the environments are poorly established. Soils, water (streamwater and groundwater), and plants (hot pepper, Capsicum annuum; and rice, Oryza sativa) were collected from all regions of South Korea and measured Sr isotope ratios (⁸⁷Sr/⁸⁶Sr). Sequential leaching of soil showed that Sr in the exchangeable and carbonate fractions (bioavailable) had a lower ⁸⁷Sr/⁸⁶Sr ratio than that in the silicate fraction, consistent with a low ⁸⁷Sr/⁸⁶Sr ratio in the plant. Although the bedrock–soil–water–plant system is closely linked, statistical analysis indicated that ⁸⁷Sr/⁸⁶Sr ratios of the plant showed the greatest agreement with those of water and the exchangeable fraction of soil. This study is the first report of ⁸⁷Sr/⁸⁶Sr isoscapes in South Korea and first demonstrates that the agricultural product is strongly linked with the exchangeable fraction of soil and water

Fig 3 -

Boxplots showing (A) δ13C, (B) δ15N, and (C) δ34S values in human hair samples collected from nine administrative provinces (GG through JJ) and major metropolitan cities (MC) in Korea. Provinces are abbreviated as: Gyeonggi (GG), Gangwon (GW), Chungbuk (CB), Chungnam (CN), Jeonbuk (JB), Jeonnam (JN), Gyeongbuk (GB), Gyeongnam (GN), and Jeju (JJ). Seven metropolitan cities (hatched areas) are also shown. Dashed lines represent the mean isotope values of all samples. Colored bars represent the standard deviations of isotope values for all samples.</p

Fig 2 -

Relationships between (A) δ13C and δ15N, and (B) δ15N and δ34S values obtained from human hair and food samples collected across South Korea.</p

<i>δ</i>¹³C, <i>δ</i>¹⁵N, and <i>δ</i>³⁴S values of food samples (n = 34) collected from metropolitan cities supermarkets in South Korea.

(XLSX)</p

DataSheet1_Dynamics of trace and rare earth elements during long-term (over 4 years) decomposition in Scots pine and Norway spruce forest stands, Southern Sweden.docx

The temporal dynamics of 33 major, trace, and rare earth elements (REEs) were studied in the litter samples containing Swedish Norway spruce (Picea abies) (NSL) and Scots pine (Pinus sylvestris) (SPL), with the aim to assess their release and accumulation dynamics. Litter bags (8 × 8 cm) were incubated in paired monoculture stands with both the species for up to 5 years from 1979 to 1984 according to a randomized block design comprising 25 blocks (1 × 1 m) within an area of 625 m2. The decomposition rate was slightly higher for Scots pine litter (k = 0.315) than for Norway spruce litter (k = 0.217). During litter decomposition, at ∼70% accumulated mass loss (AML), the concentration of trace elements increased by >50% in both litter types compared to initial concentrations. The concentration change took place in a non-linear pattern, and polynomial quadratic regression between concentration change and accumulated mass loss resulted in significant relationships (adj R2 = 0.20–0.97; p = 0.15–2 = >0.95). A general upward convexity in the dynamics suggests that if further incubated in the field, decomposing litter could have accumulated more REEs in the organic matter. The results of this study can be useful for future studies in other ecosystems including metal-contaminated sites or element-depleted sites. Plant litter accumulation, its decomposition, and build-up of humic substances in the decomposing organic matter can act as a sink for elements and can be used as a management tool for ecological amelioration of metal-contaminated sites as well as natural systems that are impoverished, especially recuperating sites. The study’s findings have implications beyond such sites and can be useful in any research that seeks to understand the patterns of accumulation and release related to decomposition in different ecosystems.</p

Plots of <i>δ</i>¹³C and <i>δ</i>¹⁵N values of human hair.

(A) δ13C and δ15N values found in human hair in South Korea, China, and Japan and (B) the same data including observations from Mongolia, Oceania, USA, Canada and Europe for comparison. In the figure on the left, symbols without error bars represent the average values of individual studies in each country (circle: South Korea, square: Japan, triangle: China). Data sources: South Korea [3, 42], Japan [3, 42–44], China [18, 44, 45], Mongolia [3, 42], Oceania [18, 44, 46–48], USA [2, 4, 6, 18, 42, 49, 50], Canada [18, 19, 44], Europe [6, 8, 18, 44, 51, 52].</p

Fig 1 -

Frequency distributions of (A) δ13C, (B) δ15N, and (C) δ34S values in human hair and food samples collected across South Korea.</p

<i>δ</i>¹³C, <i>δ</i>¹⁵N, and <i>δ</i>³⁴S values of human hair samples (n = 264) collected from South Korea.

(XLSX)</p

Carbon, nitrogen and sulfur isotope values of food samples collected from South Korea.

Carbon, nitrogen and sulfur isotope values of food samples collected from South Korea.</p

S2 Fig -

Fish and animal contribution to protein supply for East Asian countries since 1961: (A) fish/total proteins, (B) animal/total proteins and (C) (fish+animal)/total proteins. (TIF)</p