Why Biodegradable Chemicals Persist in the Environment? A Look at Bioavailability

Concerted Evaluation of Pesticides in Soils of Extensive Grassland Sites and Organic and Conventional Vegetable Fields Facilitates the Identification of Major Input Processes

“…The difference between observed field dissipation and laboratory rate constants from literature could, on the other hand, also be due to the dissimilarity in partial sequestration of the pesticides, 46 which leads to their reduced availability for subsequent dissipation. 25 For literature-based data, this underestimation of the sequestration process could most likely be due to the fact that environmental factors, such as varying soil temperature and moisture contents, are not taken into account during dissipation studies for risk assessments or registration processes. 47 We also examined substance properties of the pesticides to determine if commonalities were evident among the substances that deviate strongly from expected values and if these properties could account for the greater deviation in the dissipation behavior of these substances compared to the literature values.…”

“…However, for pesticides with a low half-life, it appears that the assumption of first-order dissipation may not be suitable for estimation over an extended period of time of more than a couple of half-lives as the discrepancy in observed and predicted dissipation was particularly striking for them. The difference between observed field dissipation and laboratory rate constants from literature could, on the other hand, also be due to the dissimilarity in partial sequestration of the pesticides, which leads to their reduced availability for subsequent dissipation . For literature-based data, this underestimation of the sequestration process could most likely be due to the fact that environmental factors, such as varying soil temperature and moisture contents, are not taken into account during dissipation studies for risk assessments or registration processes .…”

“… 15 , 24 These properties are responsible for volatilization, sorption, leaching to groundwater, uptake by plants or organisms, and abiotic and microbial transformation, with sorption and biodegradation being the most relevant for the fate of the substances. 6 , 7 , 25 Concerning the soil characteristics, it is mainly the soil mineralogy (solid inorganic phases) and soil texture (especially clay content), the amount of soil organic matter, pH, the moisture levels, and the soil temperature that influence the behavior of pesticides over time. 24 …”

“…Volatilization is the origin of long-range transport via air and subsequent wet or dry deposition, causing pesticide contamination in places where they most likely were never applied, such as the Arctic or pristine mountain regions. − Whether and to which degree volatilization takes place is dependent on meteorological and environmental conditions, such as humidity and nature of the surface as well as temperature, wind, and the chemical’s vapor pressure . For atrazine, for instance, it has been shown that it can be volatilized, transported, and detected in rain water years after application. , However, recent studies showed that this is not only the case for older and more persistent pesticides but also for currently used ones including alachlor, chlorpyrifos, chlorothalonil, and S-metolachlor. , To what extent substances are further dispersed or mostly remain as residues in the soil depends on both the physicochemical properties of the pesticides and soil characteristics. , These properties are responsible for volatilization, sorption, leaching to groundwater, uptake by plants or organisms, and abiotic and microbial transformation, with sorption and biodegradation being the most relevant for the fate of the substances. ,, Concerning the soil characteristics, it is mainly the soil mineralogy (solid inorganic phases) and soil texture (especially clay content), the amount of soil organic matter, pH, the moisture levels, and the soil temperature that influence the behavior of pesticides over time …”

Evaluating the Impact of Nutrient Doses on Biostimulation of Petroleum Hydrocarbon Biodegradation in Cold Region Soils

“…The contrasting outcomes of N and P addition on biodegradation enhancements as described above are poorly explained but could be attributed to (i) the presence of significantly different amounts of bioavailable background N and P in the soils; (ii) the lack of bioavailability of the amended nutrients due to chemisorption to soil or other processes; (iii) impacts of diesel and nutrients on the soil microbial community, including compositional differences in microbial R and K strategists; or (iv) concentrations and types of petroleum hydrocarbon sources. ,− R-strategists are species that grow in substrate-rich environments, in contrast to K-strategists that grow in substrate-limited environments…”