A new DGT technique comprised in a hybrid sensor for the simultaneous measurement of ammonium, nitrate, phosphorus and dissolved oxygen

Mingyi Ren; Shiming Ding; Dan Shi; Zhilin Zhong; Jingxin Cao; Liyuan Yang; Daniel C W Tsang; Dan Wang; Donghua Zhao; Yan Wang

doi:10.1016/j.scitotenv.2020.138447

A new DGT technique comprised in a hybrid sensor for the simultaneous measurement of ammonium, nitrate, phosphorus and dissolved oxygen

Sci Total Environ. 2020 Jul 10:725:138447. doi: 10.1016/j.scitotenv.2020.138447. Epub 2020 Apr 4.

Authors

Mingyi Ren¹, Shiming Ding², Dan Shi³, Zhilin Zhong¹, Jingxin Cao¹, Liyuan Yang³, Daniel C W Tsang⁴, Dan Wang⁵, Donghua Zhao⁵, Yan Wang⁶

Affiliations

¹ State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008, China; University of Chinese Academy of Sciences, Beijing 100049, China.
² State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008, China; Nanjing EasySensor Environmental Technology Co., Ltd, Nanjing 210018, China,. Electronic address: smding@niglas.ac.cn.
³ School of Resources and Environment, University of Jinan, Jinan 250022, China.
⁴ Department of Civil and Environmental Engineering, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, China.
⁵ Shanghai Waterway Engineering Design and Consulting Co., Ltd., Shanghai 200120, China.
⁶ State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008, China; Nanjing EasySensor Environmental Technology Co., Ltd, Nanjing 210018, China.

PMID: 32305641
DOI: 10.1016/j.scitotenv.2020.138447

Abstract

A new diffusive gradients in thin films technique (ZrO-AT DGT) with zirconium oxide, A-62 MP and T-42H resins containing in a single binding gel was developed for simultaneous measurement of nitrate (NO₃-N), ammonium (NH₄-N) and phosphate (PO₄-P). The DGT uptake was found to be independent of pH variation from 3.2-8.7. Ionic strengths below 5, 10 and 750 mmol·L^-1 NaCl did not affect DGT uptake of NH₄-N, NO₃-N and PO₄-P, respectively. This new DGT was deployed in natural freshwater environments, with in situ measurements of the three nutrients found to be accurate. It ensured that rinsing the exposed surface of the DGT device at 3-day intervals can prevent biofouling. Additionally, a hybrid sensor comprising the novel DGT binding layer overlying an O₂ planar optrode was tested in sediments to evaluate the dynamics of O₂ and the three nutrients. Results showed that PO₄-P and NO₃-N fluxes decreased while fluxes of NH₄-N increased under aerobic conditions. Nearly simultaneous variation in O₂ and NO₃-N was observed at the sediment-water interface (SWI) and transformation of NO₃-N and PO₄-P was found to be sensitively influenced by O₂ dynamics.

Keywords: Ammonium; Nitrate; Passive sampling; Phosphorus; Simultaneous measurement.