三橋 弘宗

Abstract Environmental pollution in stream networks is a major concern. In this study, the effects of land-use and geological characteristics on basin-scale sulfate and nitrate dynamics in the Chikusa River basin, Hyogo, Japan, where substantial environmental pollution has not yet been officially reported, were evaluated from the perspective of an overview. Using sulfate and nitrate concentrations as well as their isotopic signatures ( δ ¹⁵ N-NO ₃ ⁻ , δ ¹⁸ O-NO ₃ ⁻ , δ ³⁴ S-SO ₄ ²⁻ , δ ¹⁸ O-SO ₄ ²⁻ values) as response variables, we employed generalized linear mixed-effects models (GLMMs) to clarify the effects of land coverage, geological rock type, and season on the loading of these solutes. The results obtained showed an increase in sulfate concentration with an increase in the proportional area of exploited land regardless of the season. Isotopic signatures ( δ ³⁴ S-SO ₄ ²⁻ , δ ¹⁸ O-SO ₄ ²⁻ values) and the GLMMs suggested that sulfate primarily originated from the soil owing to rock weathering processes, and its distribution was mainly driven by the confluence of river branches along with altitude. In contrast, nitrate concentration varied with season, decreasing with an increase in the proportional area of exploited land in summer and showing an opposite trend in winter. The δ ¹⁵ N vs. δ ¹⁸ O plot showed that the impacts of direct nitrate input from precipitation and chemical fertilizer were negligible, while topically applied manure and septic waste played important roles. The GLMMs also indicated that the proportion of fertilized area affects the spatial distribution of δ ¹⁵ N-NO ₃ ⁻ values but not nitrate concentration, implying the existence of nitrate loading from fertilized areas that could not be detected via concentration-only measurements. Therefore, the combined use of isotopic signatures and GLMMs is expected to provide valuable information for discerning potential sources of pollution in areas without substantial environmental issues. Taken together, this approach could be applied as a “proactive indicator” particularly for areas without apparent pollution, to ensure effective river management.

We would like to introduce our recently developed systems for taking images of herbarium specimens and for the automatic extraction of data from specimen labels at the Herbarium of the Museum of Nature and Human Activities, Hyogo, Japan (HYO). Firstly, we designed a low-cost, but high-quality specimen imaging system for non-professional photographers to obtain images rapidly (Takano et al. 2019). Our system uses a mass-produced, mirrorless single-lens reflex (SLR) camera (SONY ILCE6300) with a zoom lens (Samyang Optics SYIO35AF-E35 mm F/2.8). We made a photo stand by ourselves to reduce costs. In addition, we have adopted an LED (light-emitting diode) lighting system with high color rendering. This imaging system has been introduced, with some improvements or adjustments for available space, to various herbaria in Japan (e.g., University of Tokyo (TI), Kyoto University (KYO)), contributing to the digitization of herbarium specimens across Japan. Next, we developed a system to extract label information from specimen images. The specimen image was uploaded to Google OCR and data were extracted in the form of text. Uploading the whole specimen image decreased the reading accuracy of the software because the plant images behaved as OCR (Optical Character Reader) noise. Therefore, the label part was cut out from the whole specimen image by using D-Lib*1 and uploaded to tesseract OCR*2 for OCR extraction of the label information (Aoki 2019, Takano et al. 2020). When installing this system for HYO, we designed it as an application accessible externally via the internet, which proved very useful during the coronavirus pandemic: part-time workers checked and conducted label data input from home. Finally, we decided to develop a system that would automatically label the text data extracted by OCR and input them into the appropriate cells of the database. Even though the text data could be extracted from specimen images, it needed a human to input them into the database. Therefore, we adopted Named Entity Recognition (NER), a system that extracts named entities such as place names, identifying proper nouns from unstructured text data. It enables information recorded in herbarium specimens to be tagged as named entities. We tried text matching at first, but the result was not satisfactory, so we started to use machine learning instead. We compared three natural language libraries for Japanese: BERT (Bidirectional Encoder Representations from Transformers), Albert (A Lite version of BERT), and SpaCy. Despite BERT and SpaCy returning similarly high f-scores (indicating good performance), we decided to use SpaCy because it runs better on ordinary PCs or servers. With sufficient machine learning after the creation of a text corpus (a specialised dataset) specific to labels on herbarium specimens, we successfully developed the application. The project files are available on GitHub*3 (Takano et al. 2024). We then examined whether this system could be applied to non-plant specimen images, i.e., fishes or birds, and found that it could efficiently extract data. Therefore, we decided to publicize this system on the cloud server and share it with other natural history museums in Japan*4. Curators can obtain a unique ID and password and upload specimen images from their collection to extract label data. The digitization of natural history collections in Japan has been long behind other countries, and this system will help to accelerate it. The system mentioned above is specialized for the natural history collections of Japan, but we believe it is possible to build similar programs in other countries, and we hope our experience will contribute to the mobilization of the world’s natural history collections.