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© 2019 Riparian zones are essential to preserve water quality of rivers adjacent to large areas of irrigated agriculture. We used HYDRUS (2D/3D) to quantify the long-term (8 years) influence of crops (almonds, wine grapes and potato-carrot) irrigated with recycled water on water and solute exchange at the Gawler River interface in relation to vegetation buffer widths from 10 to 110 m. We found that under almond and annual horticulture the likely average annual water flow from the irrigated area to the river was nearly twice as much (2.1 and 1.8, respectively) that under wine grapes. The hydraulic exchange at river interface for different irrigated crops was found to be sensitive to the buffer widths. For wine grapes, almonds and annual horticulture, the average annual hydraulic balance reached an equilibrium at 20, 65 and 55 m buffer widths, respectively. Furthermore, for wine grapes, with a 20 m buffer width, the average annual load of salts became negligible. This study shows that buffer widths of 20, 60, and 40 m for irrigated wine grapes, almond, and annual horticulture, respectively, are needed to restrict the migration of salts to the river. Further refinements are possible by incorporating the influence of preferential flow paths, improved water stress response functions, and addressing the data limitations for calibration of the model for solute dynamics.

Plant protection products containing nanomaterials that alter the functionality or risk profile of active ingredients (nano-enabled pesticides) promise many benefits over conventional pesticide products. These benefits may include improved formulation characteristics, easier application, better targeting of pest species, increased efficacy, lower application rates, and enhanced environmental safety. After many years of research and development, nano-enabled pesticides are starting to make their way into the market. The introduction of this technology raises a number of issues for regulators, including how does the ecological risk assessment of nano-enabled pesticide products differ from that of conventional plant protection products? In this paper, a group drawn from regulatory agencies, academia, research, and the agrochemicals industry offers a perspective on relevant considerations pertaining to the problem formulation phase of the ecological risk assessment of nano-enabled pesticides. Refereed/Peer-reviewed

usc Refereed/Peer-reviewed The application of fixed bed high rate nitrifying trickling filters (NTFs) for the removal of track organic chemicals of concern (CoC) is less well known than their application to nutrient removal in water treatment. Particularly, the effect of exogenous organic carbon substrate (sucrose) loading on the performance of NTFs is not well understood. A laboratory-scale NTF system was operated in recirculation mode, with the objective of removing ammonia and CoC simultaneously. The efficiency of a high rate NTF for removal both of low concentration of ammonia (5 mg NH4-N L-1) and different concentrations of CoC in the presence of an exogenous organic carbon substrate (30 mg total organic carbon (TOC) L-1) was investigated. In the presence of exogenous organic carbon, the results demonstrated that the high rate NTF was able to successfully remove most of the CoCs investigated, with the removal ranging from 20.2% to 87.54%. High removal efficiencies were observed for acetaminophen (87.54%), bisphenol A (86.60%), trimethoprim (86.24%) and 17α-ethynylestradiol (80.60%). It was followed by the medium removal efficiency for N, N-diethyl-m-toluamide (61.31%) and atrazine (56.90%). In contrast, the removal of caffeine (28.43%) and benzotriazole (20.20%) was poorer in the presence of exogenous organic carbon. The removal efficiency for CoC was also compared with the results obtained in our previous study in the absence of exogenous organic carbon. The results showed that the addition of exogenous organic carbon was able to improve the removal of some of the CoC. Significant TOC percentage removals (45.68%-84.43%) and ammonia removal rate (mean value of 0.44 mg NH4-N L-1 h-1) were also achieved in this study. The findings from this study provide valuable information for optimising the efficiency of high rate NTF for the removal of ammonia, CoC and TOC.

Pesticides are essential tools for crop protection and disease prevention. These agricultural chemicals (and their associated uses) continue to be subject to increased regulatory scrutiny, even though modern pesticides have become safer, more effective, and target specific. Pesticide persistence, off-target movement to ground and surface water systems, and potential for impacting non-target organisms are the major focus for regulatory assessments. Sorption and degradation are among the dominant processes that determine the fate and ecological risk of pesticides in the environment. This book addresses pesticide sorption and degradation processes in the context of regulatory evaluation, yet with a special focus on the chemistry-soil-environment interactions to better quantify the increasingly observed non-first-order and time-despondent behavior in the environmental fate studies.

Cadmium (Cd) is of no known essential biological function and is toxic to plants and animals. Leaching of Cd through soil profiles has implications for both its accumulation in subsoil or contamination of ground-water. We measured adsorption and transport of Cd in the presence of Ca and Na salts of varying ionic strengths using batch and miscible displacement techniques. Two variable charge soils, an Oxisol and an Alfisol, were used in this study. The Alfisol, despite its lower clay content, showed an adsorption coefficient ( K ) that was four times higher than the clay-rich Oxisol. Such a difference in adsorption was attributed to the presence of 2 : 1 layer silicate minerals in the Alfisol and the consequent high surface negative charge density. In column experiments, a marked effect of ionic strength on the breakthrough curves (BTCs) of Cd was observed when the concentrations of NaNO 3 were increased from 0.03 M to 0.15 M in the background solutions. This increase caused nearly four times faster movement of Cd through the Oxisol soil column. The effect of increasing Ca(NO 3 ) 2 concentration on Cd adsorption and transport was relatively less pronounced than that recorded for the NaNO 3 solution. In the Alfisol, the increase in Ca(NO 3 ) 2 ionic strength from 0.05 M to 0.25 M resulted in four-fold smaller adsorption coefficient. For both soils, the movement of Cd at a constant ionic strength was, however, an order of magnitude faster in the presence of Ca(NO 3 ) 2 than that in the presence of NaNO 3 . To describe the combined effect of ionic strength and pH, we used the K values calculated from the BTCs with CXTFIT model to develop a simple theoretical relationship between Cd adsorption and [H + ], [Ca 2+ ] and [Cd 2+ ] in solution. The relation was found to be consistent with other published studies. The study demonstrated that Cd mobility in soils is strongly affected by the soil solution composition (ionic strength and type of cations).

Pharmaceuticals released into aquatic systems are expected to sorb to sediments to varying degrees. Their sorption is likely to influence their fate and, ultimately, the risk they pose to aquatic organisms. This has led to the European Medicines Agency requiring an assessment of affinity to solids, using batch sorption methods, for the environmental risk assessment (ERA) of new human medicines. However, a large body of data is generated before pharmaceuticals are released onto the market, including their extent of distribution throughout the human body, measured by the volume of distribution (VD). In the present study, batch sorption experiments were undertaken using 12 different soils and sediments to determine whether VD was a good indicator of experimental Kd values for 21 pharmaceuticals. The r2 values obtained from the regressions ranged from 0.39 to 0.76 (with a median value of 0.5) and all regressions were found to be significant. The use of this more comprehensive set of soils and sediments was consistent with previous studies comparing VD and Kd, despite the Kd values of the selected pharmaceuticals varying greatly between soils. The relationship between Kd and VD was greatly improved when zwitterionic antibiotics and carbamazepine were not included, possibly due to complex sorption or pharmacokinetic behavior. There are likely to be a number of factors affecting the sorption of pharmaceuticals that cannot be explained by VD. However, further work may elucidate how these factors can be accounted for, enabling VD to be effectively used to facilitate the ERA of human pharmaceuticals with already available information. Refereed/Peer-reviewed