Biogeochemical data from urban ponds in Brussels

The dataset comprises two files, each containing geo-referenced information with corresponding timestamps.The names of the ponds are written in French according to the official name defined by Brussels Environment (BE).

Brussels_ponds_all.xlsx contains pH, Conductivity, dissolved oxygen saturation,  CO2, CH4, N2O dissolved concentrations, chlorophyll-a concentrations, inorganic nutrients (NO3-, NO2-, NH4+, PO43-) concentrations, total phosphorus and total suspended matter concentrations collected during four surveys (November 2021, February 2022, May 2022 and August 2022) on 22 ponds

Brussels_ponds_Chla_temporal.xlsx  contains chlorophyll-a concentration of two ponds monitored on a recurring basis (1-2 times a month) from June 2021 to December 2022.

All ponds have pontoons, raised above the water surface, which allow sampling at least 2m further from the banks. Water pH, temperature, conductivity and oxygen saturation level (%O2) were measured by a VWR MU 6100 H probe. Water was collected in 2L polypropylene bottles for subsequent analysis of chlorophyll a (Chl-a), total suspended matter (TSM) and dissolved nutrients (ammonium (NH4+), nitrite (NO2-), nitrate (NO3-), soluble reactive phosphorus (SRP)). Three 50mL falcons were filled with unfiltered water and stabilised with 200µL HNO3 (65%) for total phosphorus (Ptot) analysis.

Filtration on Whatman filters 0.7µm GF/F glass microfibres with diameter of 47mm was carried out. For TSM, 1 pre-weighed filter was weighed after drying at 100°C for 48h in order to obtain the TSM concentration. For Chl-a, a filter was placed after filtration in 90% acetone to extract the Chl-a, which was then measured by fluorimetry (Kontron SFM 25 model) at an excitation length of 430nm and emission length of 664nm (Yentsch and Menzel, 1963). Nutrient concentrations were determined spectrophotometrically (Perkin-Elmer Lambda 650 S model) by coloration of the filtrates obtained after filtration through 0.7µm Whatman GF/F filters. NH4+ was determined by coloration with nitroprusside-hypochlorite-phenol (Grasshoff and Johannsen, 1972) at 630nm. NO2- and NO3- are determined before and after reduction of NO3- to NO2- by passage through a cadmium-copper column. The NO2- is then reacted with Griess' reagent in acidic medium (Grasshoff et al., 1983) at 540nm. The SRP is determined after colorimetric reaction with ammonium molybdate, ascorbic acid and potassium antimony tartrate (Koroleff, 1983) at 885nm.

Ptot was determined by inductively coupled plasma spectroscopy (ICP) on an ICP-OES Perkin Elmer Avio 200 model. The assay protocol was based on the US EPA (1994)  method 200.7 for analysis of metals and trace elements in water by ICP with prior microwave acid digestion based on US EPA, (2007) method 3015A.

CO2 measurements were carried out on the field with a Li-Cor Li-840 IR-CO2/H2O gas analyser calibrated before each campaign, using the headspace technique with 4 polypropylene syringes (Abril et al., 2015). Samples for CH4 and N2O were collected via a silicone tube into 60mL borosilicate serum bottles and poisoned with 200µL of saturated HgCl2 solution. The vials were sealed with a butyl stopper and crimped with an aluminium cap. Measurements were carried out using the headspace technique (Weiss, 1974) and a gas chromatography measurement (model SRI 8610C) with a flame ionisation detector (FID) for CH4 and an electron capture detector (ECD) for N2O.

References:

Abril, G., Bouillon, S., Darchambeau, F., Teodoru, C.R., Marwick, T.R., Tamooh, F., Omengo, Ochieng Omengo, F., Geeraert, N., Deirmendjian, L., Polsenaere, P., Borges, A.V., (2015). Technical Note : Large overestimation of p CO2 calculated from pH and alkalinity in acidic , organic-rich freshwaters Biogeosciences 12, 67–78. https://doi.org/10.5194/bg-12-67-2015

Grasshoff, K., & Johannsen, H. (1972). A new sensitive and direct method for the automatic determination of ammonia in sea water. ICES Journal of Marine Science, 34(3), 516-521. https://doi.org/10.1093/icesjms/34.3.516

Grasshoff, K., Kremling, K., & Ehrhardt, M. (Eds.). (1983). Methods of seawater analysis : Determination of nitrite. John Wiley & Sons

Koroleff, J. (1983). Determination of total phosphorus by alkaline persulphate oxidation. Methods of Seawater Analysis. Verlag Chemie, Wienheim, 136-138.

U.S. EPA. 1994. “Method 200.7: Determination of Metals and Trace Elements in Water and Wastes by Inductively Coupled Plasma-Atomic Emission Spectrometry,” Revision 4.4. Cincinnati, OH. https://www.epa.gov/esam/method-2007-determination-metals-and-trace-elements-water-and-wastes-inductively-coupled

U.S. EPA. 2007. “Method 3015A (SW-846): Microwave Assisted Acid Digestion of Aqueous Samples and Extracts,” Revision 1. Washington, DC https://www.epa.gov/esam/epa-method-3015a-microwave-assisted-acid-digestion-aqueous-samples-and-extracts

Weiss, R. (1974). Carbon dioxide in water and seawater: the solubility of a non-ideal gas. Marine chemistry, 2(3), 203-215. https://doi.org/10.1016/0304-4203(74)90015-2

Yentsch, C. S., & Menzel, D. W. (1963, July). A method for the determination of phytoplankton chlorophyll and phaeophytin by fluorescence. In Deep Sea Research and Oceanographic Abstracts (Vol. 10, No. 3, pp. 221-231). Elsevier. https://doi.org/10.1016/0011-7471(63)90358-9