High-resolution records of porewater sulfate concentrations are critical to understanding the modern biogeochemical sulfur cycle, particularly the connection between microbial metabolic activity, ambient geochemistry, and feedbacks on global carbon cycling and climate. To date, the nature of sulfate measurements requires extraction of fluids or sediments from the field, often leading to significant disturbances in the systems studied. Further, the resulting data may have limited spatial resolution (due to volume restrictions of porewater sampling), hindering the ability to reconstruct key biological and geochemical processes. Here a novel passive sampler that is seeded with barium oxalate is optimized for the in situ sampling of sulfate to improve both the fidelity and the spatial resolution of sulfate profiles that may be obtained. Simulated sediment studies showed that consistent profiles could be resolved in both 2 and 6 h deployments that were in good agreement with traditional porewater reconstructions from adjacent core samples. Although the sampler has been calibrated for water concentrations between 2 to 28 mM of sulfate, the detection limits may be improved with modified sampler geometry or longer deployment times.Keywords: marine sulfate; passive sampling; Sulfate isotopes; sulfate sampler; sulfate sampling;

•EVA plates had highest precision of the three methods in lab and field trials.•EVA plates had the highest extraction efficiency of the three methods.•Of the methods, EVA plates detect compounds with broadest range of properties.•EVA plate performance is an effective passive sampling method.•Predictive relationships for pesticide partitioning were developed.Laboratory and field trials evaluated the efficacy of three methods of detecting aquatic pesticide concentrations. Currently used pesticides: atrazine, metolachlor, and diazinon and legacy pesticide dieldrin were targeted. Pesticides were extracted using solid-phase extraction (SPE) of water samples, titanium plate passive samplers coated in ethylene vinyl acetate (EVA) and eastern oysters (Crassostrea viginica) as biosamplers. A laboratory study assessed the extraction efficiencies and precision of each method. Passive samplers yielded the highest precision of the three methods (RSD: 3–14% EVA plates; 19–60% oysters; and 25–56% water samples). Equilibrium partition coefficients were derived. A significant relationship was found between the concentration in oyster tissue and the ambient aquatic concentration. In the field (Housatonic River, CT (U.S.)) water sampling (n = 5) detected atrazine at 1.61–7.31 μg L−1, oyster sampling (n = 2 × 15) detected dieldrin at n.d.–0.096 μg L−1 SW and the passive samplers (n = 5 × 3) detected atrazine at 0.97–3.78 μg L−1 SW and dieldrin at n.d.–0.68 μg L−1 SW.