Meta-analyses on published data of pollutant concentrations in various environmental media are valuable methods for studying temporal trends when long-term monitoring data are unavailable.
Meta-analysis is a statistical method for combining results from multiple studies in an effort to increase inference power. Metaanalyses were conducted to learn the temporal trends of pollutants in the environment and their environmental fates (Chen et al.,2012; Net et al., 2015). Such kinds of studies provide deeper insights into environmental behaviors of pollutants than individual field surveys. However, meta-analysis on heavy metal concentrations in farmland topsoil of the YRD is not available. Thus, meta-analysis for evaluating the temporal trends of heavy metals in farmland soils is conducted.