Dry Atmospheric Deposition Dataset

698,245

Observations

525

Series

105

Subjects

1987–2026

Period covered

What this looks like

One real series from the dataset, and real rows from the head of its published extract. Neither is a mock-up: the rows below are the same rows, unchanged, that are in the file you would download.

Dry sulphate deposition at Oxford

The longest single series this dataset holds — 2,000 weekly values, one of 525. Drawn from 600 of them, evenly spaced across the record. The dataset is not this chart.

Drawn to show the shape and resolution of what the dataset contains, not to make a point about Oxford. Gaps are breaks, never interpolated.

View the data behind this chart

240 of 463 periods, evenly spaced across the record. Every value is in the download and the API; a table of all 463 would be longer than this page and unusable with a screen reader.
Period	Oxford (kg/ha)
1987.6666666666667	0.023
1987.8333333333333	0.0055
1988	0.024
1988.1666666666667	0.030
1988.3333333333333	0.043
1988.5	0.065
1988.6666666666667	0.027
1988.8333333333333	0.015
1988.9166666666667	0.016
1989.0833333333333	0.034
1989.25	0.048
1989.4166666666667	0.073
1989.5833333333333	0.071
1989.75	0.018
1989.9166666666667	0.015
1990.0833333333333	0.020
1990.25	0.038
1990.4166666666667	0.121
1990.5833333333333	0.083
1990.75	0.016
1990.9166666666667	0.0094
1991.0833333333333	0.027
1991.25	0.032
1991.3333333333333	0.086
1991.5	0.165
1991.6666666666667	0.033
1991.8333333333333	0.015
1992	0.016
1992.1666666666667	0.034
1992.3333333333333	0.071
1992.5	0.048
1992.6666666666667	0.052
1992.8333333333333	0.015
1993	0.022
1993.1666666666667	0.032
1993.3333333333333	0.044
1993.5	0.074
1993.6666666666667	0.062
1993.75	0.023
1993.9166666666667	0.013
1994.0833333333333	0.023
1994.25	0.032
1994.4166666666667	0.136
1994.5833333333333	0.117
1994.75	0.042
1994.9166666666667	0.020
1995.0833333333333	0.016
1995.25	0.025
1995.4166666666667	0.078
1995.5833333333333	0.092
1995.75	0.020
1995.9166666666667	0.010
1996.0833333333333	0.019
1996.1666666666667	0.029
1996.3333333333333	0.065
1996.5	0.041
1996.6666666666667	0.028
1996.8333333333333	0.011
1997	0.020
1997.1666666666667	0.024
1997.3333333333333	0.034
1997.5	0.098
1997.6666666666667	0.031
1997.8333333333333	0.018
1998	0.019
1998.1666666666667	0.051
1998.3333333333333	0.037
1998.5	0.059
1998.5833333333333	0.099
1998.75	0.019
1998.9166666666667	0.021
1999.0833333333333	0.018
1999.25	0.038
1999.4166666666667	0.089
1999.5833333333333	0.050
1999.75	0.023
1999.9166666666667	0.011
2000.0833333333333	0.025
2000.25	0.017
2000.4166666666667	0.037
2000.5833333333333	0.055
2000.75	0.035
2000.9166666666667	0.014
2001	0.018
2001.1666666666667	0.030
2001.3333333333333	0.048
2001.5	0.133
2001.6666666666667	0.045
2001.8333333333333	0.031
2002	0.014
2002.1666666666667	0.025
2002.3333333333333	0.058
2002.5	0.065
2002.6666666666667	0.057
2002.8333333333333	0.013
2003	0.010
2003.1666666666667	0.038
2003.3333333333333	0.050
2003.4166666666667	0.052
2003.5833333333333	0.093
2003.75	0.013
2003.9166666666667	0.012
2004.0833333333333	0.027
2004.25	0.030
2004.4166666666667	0.053
2004.5833333333333	0.075
2004.75	0.030
2004.9166666666667	0.012
2005.0833333333333	0.037
2005.25	0.043
2005.4166666666667	0.099
2005.5833333333333	0.068
2005.75	0.038
2005.8333333333333	0.018
2006	0.013
2006.1666666666667	0.029
2006.3333333333333	0.023
2006.5	0.058
2006.6666666666667	0.052
2006.8333333333333	0.018
2007	0.014
2007.1666666666667	0.025
2007.3333333333333	0.036
2007.5	0.038
2007.6666666666667	0.066
2007.8333333333333	0.011
2008	0.014
2008.0833333333333	0.016
2008.25	0.041
2008.4166666666667	0.031
2008.5833333333333	0.016
2008.75	0.022
2008.9166666666667	0.011
2009.0833333333333	0.015
2009.25	0.039
2009.4166666666667	0.030
2009.5833333333333	0.028
2009.75	0.017
2009.9166666666667	0.013
2010.0833333333333	0.015
2010.25	0.028
2010.4166666666667	0.024
2010.5	0.049
2010.6666666666667	0.029
2010.8333333333333	0.012
2011	0.021
2011.1666666666667	0.022
2011.3333333333333	0.046
2011.5	0.070
2011.6666666666667	0.020
2011.8333333333333	0.0089
2012	0.014
2012.1666666666667	0.014
2012.3333333333333	0.025
2012.5	0.023
2012.6666666666667	0.021
2012.8333333333333	0.013
2012.9166666666667	0.0094
2013.0833333333333	0.015
2013.25	0.022
2013.4166666666667	0.034
2013.5833333333333	0.030
2013.75	0.012
2013.9166666666667	0.0083
2014.0833333333333	0.018
2014.25	0.028
2014.4166666666667	0.021
2014.5833333333333	0.020
2014.75	0.014
2014.9166666666667	0.010
2015.0833333333333	0.013
2015.25	0.010
2015.3333333333333	0.017
2015.5	0.016
2015.6666666666667	0.012
2015.8333333333333	0.0025
2016	0.0051
2016.25	0.012
2016.4166666666667	0.015
2016.5833333333333	0.0094
2016.75	0.0056
2016.9166666666667	0.0062
2017.0833333333333	0.0098
2017.25	0.014
2017.4166666666667	0.012
2017.5833333333333	0.018
2017.75	0.0081
2017.8333333333333	0.0040
2018	0.0054
2018.1666666666667	0.0070
2018.3333333333333	0.012
2018.5	0.015
2018.6666666666667	0.012
2018.8333333333333	0.0055
2019	0.0096
2019.1666666666667	0.010
2019.3333333333333	0.014
2019.5	0.012
2019.6666666666667	0.010
2019.8333333333333	0.0072
2020	0.0067
2020.1666666666667	0.0094
2020.25	0.0063
2020.4166666666667	0.0089
2020.5833333333333	0.012
2020.75	0.0068
2020.9166666666667	0.0080
2021.0833333333333	0.0052
2021.25	0.011
2021.4166666666667	0.013
2021.5833333333333	0.014
2021.75	0.012
2021.9166666666667	0.0039
2022.0833333333333	0.0081
2022.25	0.0081
2022.4166666666667	0.0068
2022.5833333333333	0.011
2022.6666666666667	0.0050
2022.8333333333333	0.0041
2023	0.0059
2023.1666666666667	0.0093
2023.3333333333333	0.010
2023.5	0.010
2023.6666666666667	0.0098
2023.8333333333333	0.0032
2024	0.0050
2024.1666666666667	0.0058
2024.3333333333333	0.0097
2024.5	0.0095
2024.6666666666667	0.0074
2024.8333333333333	0.0041
2025	0.0050
2025.0833333333333	0.0047
2025.25	0.0078
2025.4166666666667	0.012
2025.5833333333333	0.011
2025.75	0.0041
2025.9166666666667	0.0089
2026.0833333333333	0.0059
2026.25	0.010

Sample rows

12 of 1,426,840 rows Taken from the start of observations-atmospheric-us-epa-castnet.csv. These are sample rows, not the dataset.

Sample rows from the Dry Atmospheric Deposition Dataset extract
`metric_id`	`subject_id`	`subject_kind`	`value`	`censored`	`censor_operator`	`censor_threshold`	`censor_limit`	`censor_reported`	`unit`	`period_start`	`period_end`	`period_kind`	`basis`	`confidence`	`source_id`	`source_ref`	`qualifier`	`superseded`	`retrieved`
air-nitric-acid	castnet-abt147	geography	1.5911	—	—	—	—	—	µg/m³	1994-01-06	—	week	measured	high	us-epa-castnet	drychem.csv	—	—	2026-08-28
air-nitric-acid	castnet-abt147	geography	2.0533	—	—	—	—	—	µg/m³	1994-01-11	—	week	measured	high	us-epa-castnet	drychem.csv	—	—	2026-08-28
air-nitric-acid	castnet-abt147	geography	2.7979	—	—	—	—	—	µg/m³	1994-01-21	—	week	measured	high	us-epa-castnet	drychem.csv	—	—	2026-08-28
air-nitric-acid	castnet-abt147	geography	1.4102	—	—	—	—	—	µg/m³	1994-01-25	—	week	measured	high	us-epa-castnet	drychem.csv	—	—	2026-08-28
air-nitric-acid	castnet-abt147	geography	4.2669	—	—	—	—	—	µg/m³	1994-02-01	—	week	measured	high	us-epa-castnet	drychem.csv	—	—	2026-08-28
air-nitric-acid	castnet-abt147	geography	1.4562	—	—	—	—	—	µg/m³	1994-02-08	—	week	measured	high	us-epa-castnet	drychem.csv	—	—	2026-08-28
air-nitric-acid	castnet-abt147	geography	3.8997	—	—	—	—	—	µg/m³	1994-02-15	—	week	measured	high	us-epa-castnet	drychem.csv	—	—	2026-08-28
air-nitric-acid	castnet-abt147	geography	1.6216	—	—	—	—	—	µg/m³	1994-03-01	—	week	measured	high	us-epa-castnet	drychem.csv	—	—	2026-08-28
air-nitric-acid	castnet-abt147	geography	2.4045	—	—	—	—	—	µg/m³	1994-03-08	—	week	measured	high	us-epa-castnet	drychem.csv	—	—	2026-08-28
air-nitric-acid	castnet-abt147	geography	2.1742	—	—	—	—	—	µg/m³	1994-03-15	—	week	measured	high	us-epa-castnet	drychem.csv	—	—	2026-08-28
air-nitric-acid	castnet-abt147	geography	2.6266	—	—	—	—	—	µg/m³	1994-03-29	—	week	measured	high	us-epa-castnet	drychem.csv	—	—	2026-08-28
air-nitric-acid	castnet-abt147	geography	1.7103	—	—	—	—	—	µg/m³	1994-04-05	—	week	measured	high	us-epa-castnet	drychem.csv	—	—	2026-08-28

Download these rows as CSV — the same twelve, with the column header, for testing a loader before committing to the full file.

Methodology

Collected from the EPA CASTNET open data directory and stored as published. The flux is not measured: the publisher computes it as the measured weekly air concentration multiplied by a deposition velocity modelled from meteorology, land cover and surface properties, under the inferential method. Every value is therefore stored with basis modelled. The publisher reports what share of each week’s deposition velocity had to be substituted for missing inputs, and that share is not uniform through the record.

What this dataset cannot tell you

Read before relying on these figures

Modelled, not measured. The concentration was observed; the deposition velocity was not. The flux is their product and inherits every assumption in the velocity model.
The deposition velocity is substituted where the inputs to model it are missing. Across the record 38% of weeks are fully substituted, and in 2017 to 2021 that reaches 85 to 87% as on-site meteorology was reduced — so the series carries a change in how it was produced partway through, and a trend read across that change is partly a trend in method.
Dry deposition only. Wet deposition — what rain brings down, and often the larger share — is measured by a different programme and is not held, so nothing here is total deposition and total cannot be computed from it.
A flux at a site is not additive across sites. Adding two weekly fluxes from different places produces a number with no area behind it.
Deposition onto a monitoring site is not deposition onto a catchment. It is a point estimate for one surface, and real catchments vary in land cover, roughness and elevation, all of which change the velocity.
United States only.

Coverage

Subjects	United States CASTNET rural monitoring sites with a long record — 105 held
Period	1987–2026
Units	kg/ha
Update cadence	Weekly
Identifier	`dry-deposition` v1.0.0

Fields

Data dictionary →

Every metric this dataset carries, with the unit it is stored in and the geography level it is reported at. Full definitions are in the data dictionary.

Identifier	Field	Unit	Reported at
`sulphate-deposition-dry`	Dry sulphate deposition Modelled dry deposition of sulphate over one week, in kilograms per hectare.	kg/ha	monitoring-station
`sulphur-dioxide-deposition-dry`	Dry sulphur dioxide deposition Modelled dry deposition of sulphur dioxide over one week, in kilograms per hectare.	kg/ha	monitoring-station
`nitrate-deposition-dry`	Dry particulate nitrate deposition Modelled dry deposition of particulate nitrate over one week, in kilograms per hectare.	kg/ha	monitoring-station
`nitric-acid-deposition-dry`	Dry nitric acid deposition Modelled dry deposition of nitric acid over one week, in kilograms per hectare.	kg/ha	monitoring-station
`ammonium-deposition-dry`	Dry ammonium deposition Modelled dry deposition of ammonium over one week, in kilograms per hectare.	kg/ha	monitoring-station

Rights and access

Licence position

Open. Derivative use true; redistribution true; commercial reuse true.

Applies to material authored by US federal agencies. Third-party material carried within a federal product may be separately protected.

Permitted uses

Public display
Derived analysis
API delivery
Bulk download
Commercial use

Available to: Public, Developer, Research, Professional, Enterprise. These follow from the rights of the contributing publishers, not from a Hydrionis pricing decision — no access tier can widen what a publisher withheld.

Contributing sources

United States Environmental Protection Agency — Clean Air Status and Trends Network (US Government work — public domain)

Attribution and citation

Cite and reuse →

Two different obligations, deliberately kept apart. One is a condition of somebody else's licence; the other is a request Hydrionis has no standing to enforce.

Suggested citation for Hydrionis

Hydrionis (2026), Dry Atmospheric Deposition Dataset, version 1.0.0, accessed 2026-09-02, hydrionis.com/data/datasets/dry-deposition/

Cite Hydrionis where you rely on the compilation, the normalisation, the eligibility judgements or a chart. Where you use an unmodified published value, the publisher’s attribution is the one that is required; crediting Hydrionis as well is welcome and is not something Hydrionis can require of you.

Recommended, not required. Hydrionis does not claim rights over unmodified public data it relayed, and doing arithmetic on somebody else’s measurements does not make them Hydrionis’s. Cite the version and the access date: Dry Atmospheric Deposition Dataset changes as publishers release and as methods are revised, and a citation without both cannot be checked later. Full guidance is on cite and reuse.

None of the contributing licences requires attribution. Crediting the publishers is still good practice and they are listed above.

Changelog

Version 1.0.0 — 2026-08-28

First release.

Additions

Five modelled dry deposition fluxes at United States rural sites, from 1987.

Use this data

Download atmospheric observations from EPA CASTNET, part 1 of 2 (1,000,000 rows) (CSV)
Download atmospheric observations from EPA CASTNET, part 2 of 2 (426,840 rows) (CSV)
Machine-readable JSON /api/v1/datasets/dry-deposition.json
How to cite this, and who you must credit
How these figures were produced
Request this at a different scale, format or geography

Every bulk extract ships with a companion metadata file carrying this dataset’s version, its sources, their licences, the attribution you are required to give and the suggested citation — so the terms travel with the file rather than staying on this page.

About this data

The fields a professional user needs to judge whether this is fit for a particular purpose. Deliberately not a score.

About this data

Everything below is a property of the data rather than a rating of it. There is deliberately no single confidence score: how much a gap matters depends on what you are about to do with the series, and only you know that.

Source	United States Environmental Protection Agency — Clean Air Status and Trends Network · US Government work — public domain
How the values came to exist	Mixed across the series — the basis is recorded on every individual value.
Period held	1987–2026
Known gaps	Modelled, not measured. The concentration was observed; the deposition velocity was not. The flux is their product and inherits every assumption in the velocity model. The deposition velocity is substituted where the inputs to model it are missing. Across the record 38% of weeks are fully substituted, and in 2017 to 2021 that reaches 85 to 87% as on-site meteorology was reduced — so the series carries a change in how it was produced partway through, and a trend read across that change is partly a trend in method. Dry deposition only. Wet deposition — what rain brings down, and often the larger share — is measured by a different programme and is not held, so nothing here is total deposition and total cannot be computed from it.
Continuity	Version 1.0.0, released 2026-08-28. 1 recorded version; breaking changes and corrections are listed in the changelog above.
Last read from the publisher	2026-08-28 · publisher updates weekly
Redistribution	Permitted by the upstream licences
Commercial reuse	Permitted by the upstream licences. No Hydrionis access tier can widen this.
Methodology	How this was produced