DOI: 10.5285/59bdb8f6-fb1f-418f-a53c-394f6c68a334
title: Carbon and nutrient data for rainfall fractions in the Peruvian Amazon

description: Aquatic carbon (dissolved inorganic carbon (DIC), dissolved organic carbon (DOC) and particulate organic carbon and the carbon isotopic composition of DIC) and nutrients (calcium, magnesium, potassium, sodium, total soluble phosphorus and silica) in rainfall fractions (rainwater, throughfall, stemflow and overland flow) were sampled in the Western Amazonian basin. The samples were collected towards the end of a wet season April - May 2012. Rainfall and throughfall samples were collected in plastic buckets. Stemflow samples were collected using stemflow collection systems. Overland samples were collected using a a plastic pipe cut lengthways directing flow into a plastic bucket. Established standard methods were used to analyse the DIC, DOC and nutrients. These methods are outlined in the lineage. The samples were taken to understand the nutrient and carbon delivery in rainwater as well as leaching from tree canopies, stems and from the soil surface.

The data collection was carried out as part of the Natural Environment Research Council (NERC) funded Amazonica project (NE/F005482/1).
description: Throughfall and rain water were collected in 31.5 centimetre diameter plastic buckets covered with fine mesh to prevent litter entering. Four replicate throughfall collectors were deployed. Eight trees without visible defects were selected for stemflow collection in the same vicinity. The stemflow collection systems were made of flexible plastic piping cut in half, attached to the tree stems with minimal use of small nails and silicon sealant to close the gaps between the pipe edge and the tree stem to direct the stemflow into the collection system into a plastic collection bucket at the bottom of the tree. Rainwater was collect at an open area near approximately two kilometres away from the throughfall collectors as a suitable site could not be found close to the location of the throughfall and stemflow sites.

A plastic pipe cut in half lengthways was placed under the stream bank to capture the overland flow and set at an angle to drain into a receiver bucket through a hole cut on the side of the bucket. The bucket was covered with a lid to prevent leaves and other litter falling in. All collectors were emptied after each rain event and when sufficient volume had been collected. Samples were taken for Dissolved Organic Carbon (DOC) and Particulate Organic Carbon (POC) analysis. On a small subset Dissolved Inorganic Carbon (DIC) samples were also collected. DIC samples were collected in pre-acidified (150 micro litre of concentrated phosphoric acid) evacuated 12 millilitre (ml) exetainers (Labco Ltd). Using a 10 ml syringe (rinsed with sample water 3 times) sample was injected into the exetainers and the needle withdrawn under water to prevent air ingress. On each sampling occasion triplicate exetainers were filled. Nutrient cations were measured in rain water and throughfall only.

DOC samples were collected in polyethylene bottles and filtered through pre-furnaced (8 hours at 450 degrees Celsius) 0.7 micro metre glassfibre filter paper (Whatman GF/F) on the day of sampling and stored refrigerated in Nalgene bottles. Prior to the analysis aliquots of the samples were acidified to pH 3.9 and degassed to remove any DIC and analysed for DOC concentration by combustion (Thermalox TOC 2020, Analytical Sciences). The filter papers were air-dried and stored in air tight containers with indicating silica gel as a drying agent. POC concentration was measured by loss on ignition. In the laboratory the filter papers were first oven dried (3 hours at 105 degrees Celsius) to establish the dry weight which was measured on a five figure balance. Then the filter papers were furnace (16 hours at 375 degrees Celsius) and re-weighed. The weight loss was converted to mg C assuming percentage Organic Carbon is equal to 50 percent. 

Aliquots of the filtered water sample were analysed for calcium (Ca) and magnesium (Mg) by Atomic Absorption Spectrometry (Perkin Elmer Analyst 400). Potassium (K) and sodium (Na) concentrations were determined by flame photometry (Sherwood Scientific M410). Colorimetric method was used to measure total dissolved phosphorus (totP) and silicon (Si). Phosphorus analysis is based on the formation of a phosphomolybdate complex which is then reduced using ascorbic acid to give blue colour that can be measured at 880 or 700 Nano metres (nm). Silica was converted to a coloured compound using the Heteropoly Blue Molybdosilicate method (American Public Health Association, 1999) and measured at 650 nm.

Data was entered into Excel spreadsheets and exported as comma separated files for ingestion into the Environmental Information Data Centre (EIDC)