Sorption and competition of two persistent organic pesticides onto marine sediments: Relevance to their distribution in aquatic system

Effect of salinity on the fate of pesticides in irrigated systems: a first overview

This review investigates the impact of salinity on the fate of the active compounds of pesticides in a cultivated environment. Due to the over-exploitation of water resources and intensification of agriculture, salinity outbreaks are being observed more often in cultivated fields under pesticide treatments. Nevertheless, there is a poor understanding of the incidence of varying water salt loads on the behavior of pesticides' active ingredients in soil and water bodies. The present review established that water salinity can affect the diffusion of pesticides' active ingredients through numerous processes. Firstly, by increasing the vapor pressure and decreasing the solubility of the compounds, which is known as the salting-out effect, salinity can change the colligative properties of water towards molecules and the modification of exchange capacity and sorption onto the chemicals. It has also been established that the osmotic stress induced by salinity could inhibit the biodegradation process by reducing the activity of sensitive microorganisms. Moreover, soil properties like dissolved organic matter, organic carbon, clay content, and soil texture control the fate and availability of chemicals in different processes of persistence in water and soil matrix. In the same line, salinity promotes the formation of different complexes, such as between humic acid and the studied active compounds. Furthermore, salinity can modify the water flux due to soil clogging because of the coagulation and dispersion of clay particle cycles, especially when the change in salinity ranges is severe.

Connecting the evidence about organic pollutant sorption on soils with environmental regulation and decision-making: A scoping review

There exists an increase of review articles of pollutant sorption on soils due to the relevance of this process in environmental fate. However, this information is not used to make environmental decisions. We conduct a scoping review to identify and categorize the state-of-the-art of pesticide sorption (organic pollutant model) and decision-making studies in 2015-2020 using databases (Web of Science, Scopus and ScieLo) to detect potential gaps and create a framework that guide the connection between scientific evidence and its institutionalization. We detect research gaps (inside sorption or decision-making studies) and evidence gaps (between sorption and decision-making) from literature based on five categories to describe sorption (sorbate-sorbent system, system variables to study the sorption process, objectives pursued by authors, experimental approaches to study the sorption process, and quantification of sorption) and four topics for regulatory contexts (sponsor contextualization, descriptive information, environmentally relevant issues and Sustainable Development Goals (SDGs)). The gaps included (i) unrelated study designs, (ii) unreliable causal mechanisms, (iii) unrelated SDGs, (iv) lack of collaboration, (v) lack of representativeness, (vi) lack of knowledge, (vii) lack of relevant studies, and (vii) unknown causal extrapolation. Our framework connected the gaps with relevant environmental issues and common research topics on sorption studies, including suggested solutions and inclusion of lacking SDG in literature. The framework can assist the science-policy interaction, promoting cooperation for different study designs, pollutant-soil systems, and socio-environmental applications, such as environmental fate and management, risk assessment, monitoring, remediation, and local regulations.

Spatial Distribution and Location of Natural Organic Matter on Sediment Particles by Scanning Electron Microscopic Analysis and the Development of a New Persistent Organic Pollutant-Sediment Kinetic Desorption Model

Natural organic matter (NOM) has long been shown to be the dominant factor in determining equilibrium and kinetic processes during sorption and desorption phenomena in sediment and soil experiments. Although several models have been suggested for predicting these processes, few offer mechanistic interpretations because the spatial location of organic matter on sediment particles is unknown. This investigation manually examined sediment particles from multiple locations, containing varying concentrations of NOM, using scanning electron microscopy with energy dispersive X-ray spectroscopy to determine the types of particles present by categorizing them as individual particles, aggregates, and "other" (detritus, algae, etc.). These types of particles were subsequently analyzed for their elemental composition, specifically the spatial location of carbon. By creating a carbon map of each particle, this investigation has determined that organic matter tends to occur in 2 forms: large aggregates or dispersed across individual sediment particles. These findings were then used to propose a more mechanistically sound mathematical model for pollutant desorption phenomena, assigning the traditional labile kinetic release component to the dispersed NOM spread randomly across sediment particles and the nonlabile kinetic release component to diffusion from densely packed NOM aggregates. Environ Toxicol Chem 2021;40:323-332. © 2020 SETAC.

Use of biological detection methods to assess dioxin-like compounds in sediments of Bohai Bay, China

Bohai Bay, in the western region of northeastern China's Bohai Sea, receives water from large rivers containing various pollutants including dioxin-like compounds (DLCs). This study used the established zebrafish (Danio rerio) model, its known developmental toxicity endpoints and sensitive molecular analyses to evaluate sediments near and around an industrial effluent site in Bohai Bay. The primary objective was to assess the efficacy of rapid biological detection methods as an addition to chemical analyses. Embryos were exposed to various concentrations of sediment extracts as well as a 2, 3, 7, 8-tetrachlorodibenzo-p-dioxin (TCDD) positive control. Exposure to sediment extract nearest the discharge site (P1) resulted in the most severe- and highest rates of change in embryos and larvae, suggesting that DLC contaminated sediment probably did not occur much beyond it. P1 extract resulted in concentration dependent increases in mortality and pericardial edema. Its highest concentration caused up-regulation of P-450 (CYP)-1A1(CYP1A) mRNA expression at 72 h post fertilization (hpf), an increase in its expression in gill arches as observed by whole mount in situ hybridization, and an increased signal in the Tg(cyp1a: mCherry) transgenic line. The pattern and magnitude of response was very similar to that of TCDD and supported the presence of DLCs in these sediment samples. Follow-up chemical analysis confirmed this presence and identified H7CDF, O8CDF and O8CDD as the main components in P1 extract. This study validates the use of biological assays as a rapid, sensitive, and cost-effective method to evaluate DLCs and their effects in sediment samples. Additionally, it provides support for the conclusion that DLCs have limited remobilization capacity in marine sediments.

Sorption of pentachlorophenol (PCP) in the marine bottom sediments-batch sorption experiment at varying pressure

Study was undertaken to determine the effect of hydrostatic pressure on the sorption of pentachlorophenol (PCP). The experiment was conducted at atmospheric pressure (1000 hPa) and at increased pressure (6000 hPa) simulating conditions at the water depth of 50 m. The sorption of PCP was examined in an artificial environment (microcosm) consisting of the marine water and the bottom sediments from a Polish harbor and the southern Baltic Sea. The first part of the experiment comprised the determination of PCP sorption parameters in the microcosms and parameters of the sediments (organic matter content, conductivity) and of the overlying water (pH, ion concentration) at 1000 hPa. The second part of the experiment was conducted at 6000 hPa inside the hyperbaric chamber. The hyperbaric exposure affected parameters of the harbor sediments and the overlying water but had little influence on the concentration of PCP in the microcosms containing the southern Baltic Sea sediments. Considering the specific characteristics of the harbor sediments, it can be assumed that the impact of hydrostatic pressure on the sorption process of PCP at 50-m depth appears to be negligible.

Adsorption of polar organic molecules on sediments: Case-study on Callovian-Oxfordian claystone

The release and transport of anthropogenic organic matter through the geosphere is often an environmental criterion of safety. Sedimentary rocks are widely studied in this context as geological barriers for waste management. It is the case of Callovian-Oxfordian claystone (COx), for which several studies report adsorption of anthropogenic organic molecules. In this study, we evaluated and reviewed adsorption data of polar organic molecules on COx claystone. Experiments were performed on raw claystone, decarbonated and clay fractions. Adsorption isotherms were measured with adsorbates of various polarities: adipate, benzoate, ortho-phthalate, succinate, gluconate, oxalate, EDTA, citrate. A significant adsorption was observed for multidentate polycarboxylic acids as evidenced with phthalate, succinate, oxalate, gluconate, EDTA and citrate (R_d = 1.53, 3.52, 8.4, 8.8, 12.4, 54.7 L kg^-1 respectively). Multiple linear regression were performed as a statistical analysis to determine the predictors from these adsorption data. A linear correlation between adsorption data (R_d) and dipole moment (μ) of adsorbates was evidenced (R² = 0.91). Molecules with a high dipole moment, μ(D) > 2.5, displayed a significant adsorption, R_d≫1 L kg^-1. A qualitative correlation can be easily estimated using the water/octanol partition coefficient, P_ow, of adsorbates (R² = 0.77). In this case, two opposite trends were distinguished for polar and apolar molecules. The use of organic carbon content in sediments is relevant for predicting adsorption of apolar compounds, log (P_ow)>+1. The oxides/clays contents may be relevant regarding polar molecules, log (^apparentP_ow)<-1. The proposed scheme offers a general methodology for investigation of geo-barriers towards heterogeneous organic plumes.

Kinetics and thermodynamics of dissolved petroleum hydrocarbons in sediment under sophorolipid application and their effects on oil behaviour end-results in marine environment

The behaviour end-result of dissolved petroleum hydrocarbons (DPHs) is known to interact with sediments in marine environments.

Toxaphene levels in retail food from the Pearl River Delta area of South China and an assessment of dietary intake

Limited literature exists on toxaphene contamination in food worldwide, particularly in mainland China. In this study, three toxaphene congeners, Parlar 26 (B8-1413), Parlar 50 (B9-1679) and Parlar 62 (B9-1025), were analyzed in five different food categories from the Pearl River Delta Area in China using isotope dilution high-resolution gas chromatography/high-resolution mass spectrometry (HRGC/HRMS), and toxaphene levels in food were reported and toxaphene dietary intake by local residents estimated. The results showed that fish contained the highest toxaphene level with a median of 12.87 pg/g wet weight (ww), followed by poultry meat, egg products, livestock meat and vegetable, which had median levels of 5.8, 2.2, 1.89 and 0.67 pg/g ww, respectively. Parlar 50 and Parlar 26 were the predominant characteristic congeners in fish, and Parlar 26 was the predominant congener not only in poultry products and eggs, but also in livestock and vegetable. The estimated average daily intake found by local residents was 35.57 pg/kg body weight/day. Overall toxaphene levels and estimated dietary intake in the Pearl River Delta Area of South China are far lower than the European Maximum Residue Limits (EU MRLs), the German MRL for fish, and other international literature data. Therefore, the risk of adverse health effects from dietary intakes of toxaphene for the local residents is not considerable at the current time, but follow-ups are warranted to study dynamic changes of toxaphene in food in this area.

Pesticides in the Ebro River basin: Occurrence and risk assessment

In this study, 50 pesticides were analyzed in the Ebro River basin in 2010 and 2011 to assess their impact in water, sediment and biota. A special emphasis was placed on the potential effects of both, individual pesticides and their mixtures, in three trophic levels (algae, daphnia and fish) using Risk Quotients (RQs) and Toxic Units (TUs) for water and sediments. Chlorpyrifos, diazinon and carbendazim were the most frequent in water (95, 95 and 70% of the samples, respectively). Imazalil (409.73 ng/L) and diuron (150 ng/L) were at the highest concentrations. Sediment and biota were less contaminated. Chlorpyrifos, diazinon and diclofenthion were the most frequent in sediments (82, 45 and 21% of the samples, respectively). The only pesticide detected in biota was chlorpyrifos (up to 840.2 ng g(-1)). Ecotoxicological risk assessment through RQs showed that organophosphorus and azol presented high risk for algae; organophosphorus, benzimidazoles, carbamates, juvenile hormone mimic and other pesticides for daphnia, and organophosphorus, azol and juvenile hormone mimics for fish. The sum TUsite for water and sediments showed values < 1 for the three bioassays. In both matrices, daphnia and fish were more sensitive to the mixture of pesticide residues present.

Spatio-temporal patterns of pesticide residues in the Turia and Júcar Rivers (Spain)

A study was conducted on the occurrence of 50 pesticides in water and sediments of Turia and Júcar Rivers (Valencian Community, Eastern Spain) for a period of two consecutive years each, 2010/2011 and 2012/2013, respectively to assess the contribution of agriculture and urban activities on pesticide pollution. The results showed that mean concentrations of pesticides ranged from <LOQ up to 200 ng/L. Chlorpyrifos was the most frequent pesticide whereas imazalil, thiabendazole, tolclofos methyl, ethion and carbofuran were those found at higher concentrations. Ubiquitous pesticides are those with long half-lives. The most polluted parts of the rivers were the headwaters and the mouth, which could be related to the agricultural practices and rainfall. Contrarily, in the abrupt part of the rivers of difficult access the contamination is low. Other quality parameters monitored in this study also corroborate the worst water quality in the alluvial plains that coincides with higher anthropic pressure. The temporal variations also indicated a strong relation of pesticide concentrations with hydrology, the higher the river flow, the higher number and frequency of pesticides but at lower concentrations. On the contrary, at lower river flows higher pesticide concentrations were detected. The risk assessment for aquatic biota pointed out that organophosphorus and fungicides are a threat to fish and daphnia and herbicides and fungicides are hazards for algae. Thus, the strict control of pesticide concentrations is important to preserve the aquatic ecosystems health.