The spatial and temporal variation of water quality at a community garden site in an urban setting: citizen science in action

Interest in urban agriculture has increased rapidly in recent decades, but little is known about the effect of potential contaminants, such as groundwater pollution, in urban areas. Furthermore, local and timely science necessary for developing place-based solutions and management plans are lacking. We present a citizen-science-driven case study of water quality in a large urban community garden in southwestern London that was initiated in response to the concerns of members about the effect of inorganic compounds in the water supply on organic produce. The 5.6-ha community garden has been cultivated for fruit and vegetables since 1921 and hand-pumped boreholes drawing water from an underlying shallow aquifer provide the only source of irrigation. We assessed the spatial and temporal distributions of specific conductance and tryptophan-like fluorescence to explore the dynamics of inorganic and organic pollution based on water drawn from the boreholes. A trained citizen scientist made measurements with a calibrated Manta II probe over a 28-mo period from 2014 to 2016. We also surveyed >80 members of the community garden to gain insight into cultivation practices. Results indicate that the concerns about external sources of pollution were unfounded. We found little evidence of the effect of potential adjacent sources of contamination or of changes in water quality in time. Distinct trends were absent, and evidence of poorer water quality close to possible sources of urban contamination was not apparent. However, significant interborehole variations in water quality were directly associated with the storage and use of manure on the site and local geological conditions. The study demonstrates the potential of citizen science to respond to community concerns and generate new and novel information when participants are engaged, trained, and equipped over longer periods of time.