Validation of mega composite sampling and nationwide mass inventories for 26 previously unmonitored contaminants in archived biosolids from the U.S National Biosolids Repository

Abstract

In the present study, archived U.S biosolids from the 2001 Environmental Protection Agency (EPA) National Sewage Sludge Survey were analyzed with an expanded U.S EPA Method 1694, to determine the occurrence of 26 previously unmonitored pharmaceuticals and personal care products (PPCPs) among a total of 120 analytes. The study further served to examine the reproducibility of a mega-composite approach for creating chemical mass inventories in biosolids based on pooled samples from wastewater treatment plants (WWTPs) nationwide. Five mega-composites reflecting 94 WWTPs in 32 states and the District of Columbia were constructed from archived biosolids and analyzed by LC/ESI-MS/MS using a newly introduced analytical method expanding upon U.S EPA Method 1694. In addition, soil-biosolids mixtures from a mesocosm setup were analyzed to experimentally determine the half-lives of biosolids-borne compounds applied on U.S land. Among 59 analytes detected, 33 had been reported previously, whereas 26 are reported in biosolids for the first time, at levels ranging from 1.65 to 673 μg kg⁻¹ dry weight. Newly recognized biosolids constituents were identified as Ca²⁺ channel blockers, antidepressants, diuretics, β-blockers and analgesics. Using a mass balance approach, the total loading of these 26 pharmaceuticals to U.S soils from biosolids land application was estimated at 5-15 tons year⁻¹. Past and present datasets for 30 pharmaceuticals and personal care products (PPCPs) were determined to be statistically indistinguishable (paired t-test; p = 0.01). This study expands the list of PPCPs reported in U.S biosolids, provides the first estimates of nationwide release rates to and environmental half-lives in U.S agricultural soils, and confirms the utility of using mega-composite sampling for economical tracking of chemical inventories in biosolids on a national scale.

Fig. 1

Rank order of mean concentrations of 26 previously unmonitored PPCPs that were detected for the first time in composites of 110 U.S biosolids samples from the 2001 NSSS. Error bars depict ± one standard deviation (n = 5), and asterisks (*) indicate compounds that were detected inconsistently.

Fig. 2

Log–log scatterplot comparing mean concentrations from the present study to those reported previously for 30 compounds commonly detected. Both datasets represent results obtained from analysis of composites created two years apart from the same group of archived samples.

Fig. 3

Decreasing concentrations of compounds plotted as natural logarithms vs. time (common x-axis). Compound structures were obtained from the database of the Royal Society of Chemistry.

Fig. 4

Predicted porewater concentration range (A) and equilibrium concentration range in soils-biosolids mixtures (B) for 26 PPCPs at environmentally relevant pH range 7–9. Concentration range for each compound has been printed with corresponding mean values in parenthesis. Compounds marked with (*) were inconsistently detected.

Fig. 5

Predicted EC₅₀ values for 22 compounds. Values for some compounds could not be calculated and may represent a potential hazard to aquatic organisms. Compounds marked with (*) indicate inconsistent detection.