Dynamic passive sampling of hydrophobic organic compounds in surface seawater along the South Atlantic Ocean east-to-west transect and across the Black Sea

Efficient and practical in-jar silicone rubber based passive sampling for simultaneous monitoring of emerging fungicides in water and soils

The occurrence and ecological impacts of emerging fungicides in the environment has gained increasing attention. This study applied an in-jar passive sampling device based on silicone rubber (SR) film to measuring the freely dissolved concentration (Cfree) of 6 current-use fungicides as a critical index of bioavailability in water and soils. The kinetics parameters including SR-water, soil-water, and organic carbon-water partition coefficients and sampling rates of the target fungicides were first attained and characterized well with their physicochemical properties. The in situ and ex situ field deployment in Hefei City provided the assessment of contaminated levels for these fungicides in rivers and soils. The Cfree of triadimefon and azoxystrobin was estimated at 0.54 ± 0.07-17.4 ± 2.5 ng L-1 in Nanfei River and Chao Lake, while triadimefon was only found in Dongpu Reservoir water with Cfree below 0.66 ± 0.04 ng L-1. The results exhibited that the equilibrium duration of 7 d was suitable for water application but a longer interval of 14 d was recommended for soil sampling. This work demonstrated the advantages of the proposed strategy in terms of fast monitoring within 2 weeks and high sensitivity down to detection limits in 0.5-5 ng L-1. The in-jar passive sampling device can be extrapolated to the evaluation for a wide coverage of organic pollutants in water and soils.

Occurrence, sources, and spatial variation of POPs in a mountainous tropical drinking water supply basin by passive sampling

Persistent organic pollutants (POPs) are widely distributed along the world and their levels in surface waters may pose a risk to human health due to consumption of contaminated water or fish long-term exposure to contaminated water. The occurrence of polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs) in the Piedras river (Colombia) is a problem of serious concern since freshwater is conducted to a drinking water supply system that provides more than 3 million users. In this research, we deployed silicone rubber membranes as passive samplers in two sampling campaigns at seven sampling stations selected along the river, to assess sources and spatial variation of POPs. The measurements confirmed freely dissolved concentration of the EPA prioritized PAHs (excluding naphthalene), PCBs, heptachlor isomers, dieldrin, endosulfan isomers, among other POPs at trace levels in the water source. The Risk Quotient (RQ) method was applied to prioritize POPs with the highest potential toxicity over aquatic ecosystems. The OCP Heptachlor overcome RQ, while Dieldrin and Endosulfan, and some PAHs congeners such as Perylene, Pyrene, Benzo[a]pyrene, and Fluoranthene displayed medium-risk RQ. Significant differences between sampling stations assessed by One-way ANOVA suggested that the main PAHs and PCBs sources to the river were the punctual discharge from the WWTP and a leachate discharge form a landfill located in the study area. Additionally, nonpoint sources of OCPs were identified. Our results showed that the origin of PAHs and PCBs are associated with urban activities, while the contribution of OCPs is related to the presence of legacy pesticides from past usage in agricultural activities in the basin.

Stochastic model for simulating levels of polychlorinated biphenyls in small tuna and planktons using Metropolis - Hastings algorithm

This paper proposes a stochastic model to simulate the occurrence and levels of polychlorinated biphenyls (PCBs) in juvenile tuna. This model can calculate the transport of PCBs in the ocean (macroscopic phenomena) and biomagnification in fish (microscopic phenomena). The uncertainty in the concentration of the PCBs encountered by fish was treated by adopting a random sampling from the probability distribution function using Metropolis-Hastings algorithm. The model was applied to one-dimensional cases with transported PCBs and swimming fish. The simulated PCBs levels in the fish agreed well with levels observed by previous studies. Influences of PCBs spatial distribution patterns and current velocity on the PCBs levels in fish body was examined. The results showed that the model was sensitive to the distribution pattern and moderately sensitive to the current velocity. The model has the potential to be extended to more realistic situations and to serve as a tool for environmental risk assessment.

Independent components of spatial-temporal structure of chlorophyll a patterns in the upper layer of the north-western shelf of the Black Sea

In the present study, the results of independent component decomposition of satellite-derived chlorophyll a (Chla) patterns for the north-western part of the Black Sea are presented. The study has been carried out on the basis of the DINEOF-reconstructed dataset of 8-day average log-transformed Chla (alChla) patterns for 1997-2016. The alChla patterns were decomposed into six independent components of its spatio-temporal variability in the north-western shelf of the Black Sea. The independent components reflect the spatial distribution of alChla anomalies which are likely to be formed under the influence of sea circulation factors driven by wind. The paper presents the results of the analysis of the intra-annual variability of independent components. The interpretation of the patterns of intra-annual independent components variability is given, taking into account the seasonal variability of the wind factor, the flow of the Danube, the Dnieper and Southern Bug rivers and the fact of modulation of independent components dynamics by seasonal phytoplankton succession.

Passive sampling and benchmarking to rank HOC levels in the aquatic environment

The identification and prioritisation of water bodies presenting elevated levels of anthropogenic chemicals is a key aspect of environmental monitoring programmes. Albeit this is challenging owing to geographical scales, choice of indicator aquatic species used for chemical monitoring, and inherent need for an understanding of contaminant fate and distribution in the environment. Here, we propose an innovative methodology for identifying and ranking water bodies according to their levels of hydrophobic organic contaminants (HOCs) in water. This is based on a unique passive sampling dataset acquired over a 10-year period with silicone rubber exposures in surface water bodies across Europe. We show with these data that, far from point sources of contamination, levels of hexachlorobenzene (HCB) and pentachlorobenzene (PeCB) in water approach equilibrium with atmospheric concentrations near the air/water surface. This results in a relatively constant ratio of their concentrations in the water phase. This, in turn, allows us to (i) identify sites of contamination with either of the two chemicals when the HCB/PeCB ratio deviates from theory and (ii) define benchmark levels of other HOCs in surface water against those of HCB and/or PeCB. For two polychlorinated biphenyls (congener 28 and 52) used as model chemicals, differences in contamination levels between the more contaminated and pristine sites are wider than differences in HCB and PeCB concentrations endorsing the benchmarking procedure.