{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,3,29]],"date-time":"2026-03-29T06:13:30Z","timestamp":1774764810767,"version":"3.50.1"},"reference-count":69,"publisher":"MDPI AG","issue":"17","license":[{"start":{"date-parts":[[2024,8,29]],"date-time":"2024-08-29T00:00:00Z","timestamp":1724889600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"National Key Research and Development Program of China","award":["2022YFB3903302"],"award-info":[{"award-number":["2022YFB3903302"]}]},{"name":"National Key Research and Development Program of China","award":["202102020416"],"award-info":[{"award-number":["202102020416"]}]},{"name":"National Key Research and Development Program of China","award":["GD20YGL11"],"award-info":[{"award-number":["GD20YGL11"]}]},{"name":"National Key Research and Development Program of China","award":["2024A1515010110"],"award-info":[{"award-number":["2024A1515010110"]}]},{"name":"National Key Research and Development Program of China","award":["2021BCA220"],"award-info":[{"award-number":["2021BCA220"]}]},{"name":"Guangzhou Science and Technology Plan Project","award":["2022YFB3903302"],"award-info":[{"award-number":["2022YFB3903302"]}]},{"name":"Guangzhou Science and Technology Plan Project","award":["202102020416"],"award-info":[{"award-number":["202102020416"]}]},{"name":"Guangzhou Science and Technology Plan Project","award":["GD20YGL11"],"award-info":[{"award-number":["GD20YGL11"]}]},{"name":"Guangzhou Science and Technology Plan Project","award":["2024A1515010110"],"award-info":[{"award-number":["2024A1515010110"]}]},{"name":"Guangzhou Science and Technology Plan Project","award":["2021BCA220"],"award-info":[{"award-number":["2021BCA220"]}]},{"name":"Philosophy and Social Sciences Fund of the 13th Five-year Plan of Guangdong Province of China","award":["2022YFB3903302"],"award-info":[{"award-number":["2022YFB3903302"]}]},{"name":"Philosophy and Social Sciences Fund of the 13th Five-year Plan of Guangdong Province of China","award":["202102020416"],"award-info":[{"award-number":["202102020416"]}]},{"name":"Philosophy and Social Sciences Fund of the 13th Five-year Plan of Guangdong Province of China","award":["GD20YGL11"],"award-info":[{"award-number":["GD20YGL11"]}]},{"name":"Philosophy and Social Sciences Fund of the 13th Five-year Plan of Guangdong Province of China","award":["2024A1515010110"],"award-info":[{"award-number":["2024A1515010110"]}]},{"name":"Philosophy and Social Sciences Fund of the 13th Five-year Plan of Guangdong Province of China","award":["2021BCA220"],"award-info":[{"award-number":["2021BCA220"]}]},{"name":"Guangdong Basic and Applied Basic Research Foundation","award":["2022YFB3903302"],"award-info":[{"award-number":["2022YFB3903302"]}]},{"name":"Guangdong Basic and Applied Basic Research Foundation","award":["202102020416"],"award-info":[{"award-number":["202102020416"]}]},{"name":"Guangdong Basic and Applied Basic Research Foundation","award":["GD20YGL11"],"award-info":[{"award-number":["GD20YGL11"]}]},{"name":"Guangdong Basic and Applied Basic Research Foundation","award":["2024A1515010110"],"award-info":[{"award-number":["2024A1515010110"]}]},{"name":"Guangdong Basic and Applied Basic Research Foundation","award":["2021BCA220"],"award-info":[{"award-number":["2021BCA220"]}]},{"name":"Key R&amp;D projects in Hubei Province","award":["2022YFB3903302"],"award-info":[{"award-number":["2022YFB3903302"]}]},{"name":"Key R&amp;D projects in Hubei Province","award":["202102020416"],"award-info":[{"award-number":["202102020416"]}]},{"name":"Key R&amp;D projects in Hubei Province","award":["GD20YGL11"],"award-info":[{"award-number":["GD20YGL11"]}]},{"name":"Key R&amp;D projects in Hubei Province","award":["2024A1515010110"],"award-info":[{"award-number":["2024A1515010110"]}]},{"name":"Key R&amp;D projects in Hubei Province","award":["2021BCA220"],"award-info":[{"award-number":["2021BCA220"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>Soil heavy metal contamination in urban land can affect biodiversity, ecosystem functions, and the health of city residents. Visible and near-infrared (Vis-NIR) spectroscopy is fast, inexpensive, non-destructive, and environmentally friendly compared to traditional methods of monitoring soil Cu, a common heavy metal found in urban soils. However, there has been limited research on using spatially nearby samples to build the Cu estimation model. Our study aims to investigate how spatially nearby samples influence the Cu estimation model. In our study, we collected 250 topsoil samples (0\u201320 cm) from China\u2019s third-largest city and analyzed their spectra (350\u20132500 nm). For each unknown validation sample, we selected its spatially nearby samples to construct the Cu estimation model. The results showed that compared to the traditional method (Rp2 = 0.75, RMSEP = 8.56, RPD = 1.73), incorporating nearby samples greatly improved the model (Rp2 = 0.93, RMSEP = 4.02, RPD = 3.89). As the number of nearby samples increased, the performance of the Cu estimation model followed an inverted U-shaped curve\u2014initially increasing and then declining. The optimal number of nearby samples is 125 (62.5% of the total), and the mean distance between validation and calibration samples is 17 km. Therefore, we conclude that using nearby samples significantly enhances the Cu estimation model. The optimal number of nearby samples should strike a balance, covering a moderate area without there being too few or too many.<\/jats:p>","DOI":"10.3390\/s24175612","type":"journal-article","created":{"date-parts":[[2024,8,29]],"date-time":"2024-08-29T11:33:37Z","timestamp":1724931217000},"page":"5612","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":2,"title":["Monitoring Soil Copper in Urban Land Using Visibale and Near-Infrared Spectroscopy with Spatially Nearby Samples"],"prefix":"10.3390","volume":"24","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-4443-9440","authenticated-orcid":false,"given":"Yi","family":"Liu","sequence":"first","affiliation":[{"name":"School of Public Administration, Guangdong University of Finance & Economics, Guangzhou 510320, China"}]},{"given":"Tiezhu","family":"Shi","sequence":"additional","affiliation":[{"name":"State Key Laboratory of Subtropical Building and Urban Science & Guangdong\u2013Hong Kong-Macau Joint Laboratory for Smart Cities & MNR Key Laboratory for Geo-Environmental Monitoring of Great Bay Area, Shenzhen University, Shenzhen 518060, China"}]},{"given":"Zeying","family":"Lan","sequence":"additional","affiliation":[{"name":"School of Management, Guangdong University of Technology, Guangzhou 510520, China"}]},{"given":"Kai","family":"Guo","sequence":"additional","affiliation":[{"name":"School of Geography and Remote Sensing, Guangzhou University, Guangzhou 510006, China"}]},{"given":"Chao","family":"Yang","sequence":"additional","affiliation":[{"name":"State Key Laboratory of Subtropical Building and Urban Science & Guangdong\u2013Hong Kong-Macau Joint Laboratory for Smart Cities & MNR Key Laboratory for Geo-Environmental Monitoring of Great Bay Area, Shenzhen University, Shenzhen 518060, China"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-7442-3239","authenticated-orcid":false,"given":"Yiyun","family":"Chen","sequence":"additional","affiliation":[{"name":"School of Resource and Environmental Sciences, Wuhan University, Wuhan 430079, China"},{"name":"Key Laboratory of Geographic Information System of the Ministry of Education, Wuhan University, Wuhan 430079, China"},{"name":"Hubei Luojia Laboratory, Wuhan 430079, China"}]}],"member":"1968","published-online":{"date-parts":[[2024,8,29]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"1706","DOI":"10.1038\/s41467-023-37428-6","article-title":"Soil contamination in nearby natural areas mirrors that in urban greenspaces worldwide","volume":"14","author":"Liu","year":"2023","journal-title":"Nat. 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