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In this study, ChemcatcherTM (CC) and Polar Organic Chemical Integrative Samplers (POCIS) passive samplers were chosen to investigate trace organic chemical residues in urban streams of the megacity of Sydney, Australia. In situ calibration with these passive samplers investigated 1392 organic chemicals. Six sets of CC passive samplers fitted with SDB-XC or SDB-RPS disks and six POCIS containing Oasis HLB sorbent were deployed at three sites. Every week for six weeks across three deployments, composite water samples were retrieved from autosamplers, along with one set of CC/POCIS passive samplers. Samples were analysed by Automated Identification and Quantification System (AIQS) GC/MS or LC/QTOF-MS database methods with 254 chemicals detected. The most frequently detected compounds under GC/MS analysis were aliphatic, pesticides, phenols, PAHs, sterols and fatty acid methyl esters while from LC/QTOF-MS analysis these were pesticides, pharmaceuticals, and personal care products. Sampling rates (R s) ranged between <0.001 - 0.132 L day−1 (CC SDB-XC, 18 chemicals), <0.001 - 0.291 L day−1 (CC SDB-RPS, 28 chemicals), and <0.001 - 0.576 L day−1 (POCIS Oasis HLB, 30 chemicals). Assessment of deployment duration indicated that about half of the chemicals that were continuously detected across all deployment weeks had maximal simple linear regression R2 values at four weeks for CC SDB-RPS (seven of 13 chemicals) and at three weeks for POCIS Oasis HLB (seven of 14 chemicals). Where ranges of R s recorded from the estuarine site were able to be compared to ranges of R s from one or both freshwater sites, only tributyl phosphate had a higher range of R s out of 21 possible chemical comparisons, and suggested salinity was an unlikely influence on R s. Whereas relatively higher rainfall of the third round of deployment aligned with higher R s across the estuarine and freshwater sites for CC SDB-RPS and POCIS for nearly all possible comparisons. [Display omitted] • Field comparison of Chemcatcher SDB-XC, SDB-RPS and POCIS Oasis HLB in urban waters. • Organic chemicals detected from assessment through multiresidue screening system databases. • LC-QTOF-MS analysis of SDB-RPS and POCIS Oasis HLB yielded a similar set of organic chemicals. • In situ calibration of 64 chemicals enabled by companion periodic spot water sample collection. [ABSTRACT FROM AUTHOR]

• DNA from bulk insect samples can be used to derive river health indices. • DNA derived indices correlate strongly with morphologically derived indices. • Reference libraries should contain a mix of local and global references. Macroinvertebrate surveys are commonly used for assessing the health of freshwater systems around the world. Traditionally, surveying involves morphologically identifying the families, and sometimes genera, present in samples. Biological indices, derived from taxonomic lists, provide convenient ways to summarise community data and may be fairly insensitive to species-level changes in community compositions. In recent years, molecular techniques for identifying taxa have become increasingly popular and metabarcoding approaches that offer the ability to identify species from mixtures of whole animals (bulk-samples) or from environmental samples have gained much attention. However, generating accurate species lists from metabarcode data is challenging and can be impacted by sample type, choice of primers, community composition within samples, and the availability of reference sequences. This study compares the performance of molecular data extracted from bulk-samples against morphological data in calculating two biological indices (the Stream Invertebrate Grade Number Average Level 2 (SIGNAL2), which is calculated from family-level data, and a genus-level equivalent of this index, SIGNAL_SG) and one biological metric (taxon richness). Further, molecular indices and metrics derived from global, local or mixed reference DNA libraries and with varying degrees of filtering processes applied to them, are compared with respect to the strength of their relationships with morphological indices and metrics. Molecularly derived SIGNAL2 and SIGNAL_SG scores correlated strongly with morphologically derived scores, and were strongest when using a reference library containing a mix of local and global data. Molecularly derived richness metrics were moderately correlated with morphological taxa richness; however, the strongest correlations were observed when taxa that could not be assigned SIGNAL grades were omitted from analyses. This study highlights the utility of using molecular data as an objective and sensitive alternative to traditional freshwater biological assessment using macroinvertebrates. [ABSTRACT FROM AUTHOR]