Risk Assessment of Gypsum Amendment on Agricultural Fields: Effects of Sulfate on Riverine Biota.

Gypsum (CaSO4 ∙2H2 O) amendment is a promising way of decreasing the phosphorus loading of arable lands, and thus preventing aquatic eutrophication. However, in freshwaters with low sulfate concentrations, gypsum-released sulfate may pose a threat to the biota. To assess such risks, we performed a series of sulfate toxicity tests in the laboratory and conducted field surveys. These field surveys were associated with a large-scale pilot exercise involving spreading gypsum on agricultural fields covering 18% of the Savijoki River (Finland) catchment area. The gypsum amendment in such fields resulted in approximately a four-fold increase in the mean sulfate concentration for a 2-month period, and a transient, early peak reaching approximately 220 mg/L. The sulfate concentration gradually decreased almost to the pregypsum level after 3 years. Laboratory experiments with Unio crassus mussels and gypsum-spiked river water showed significant effects on foot movement activity, which was more intense with the highest sulfate concentration (1100 mg/L) than with the control. Survival of the glochidia after 24 and 48 h of exposure was not significantly affected by sulfate concentrations up to 1000 mg/L, nor was the length growth of the moss Fontinalis antipyretica affected. The field studies on benthic algal biomass accrual, mussel and fish density, and Salmo trutta embryo survival did not show gypsum amendment effects. Gypsum treatment did not raise the sulfate concentrations even to a level just close to critical for the biota studied. However, because the effects of sulfate are dependent on both the spatial and the temporal contexts, we advocate water quality and biota monitoring with proper temporal and spatial control in rivers within gypsum treatment areas. Environ Toxicol Chem 2022;41:108-121. © 2021 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Lumbriculus variegatus (Annelida) biological responses and sediment sequential extractions indicate ecotoxicity of lake sediments contaminated by biomining.

We assessed potential ecotoxicity of lake sediments affected by biomining effluents in northeastern Finland. Growth, reproduction and behavior of the sediment-dwelling oligochaete Lumbriculus variegatus (Müller 1774) were used as ecotoxicity endpoints. Standardized chronic bioassays were used for growth and reproduction, and acute and chronic tests with Multispecies Freshwater Biomonitor (MFB) for behavior assessments. Sequential extractions were used to characterize metal bioavailability and exposure conditions in the sediments, which indicated mining-induced contamination gradients of S, Cu, Ni and U and also bioavailability gradients of S and Ni. Among the ecotoxicity endpoints, growth and reproduction responses of the standard bioassays appeared more sensitive than the behavioral responses at 21 d. In the two most mining-affected test sediments, mean number of worms and dry biomass decreased 35-42% and 46-51% in comparison to the reference sediment, respectively. The behavioral changes of worms, i.e. peristaltic and overall locomotory activity, decreased on average 20-70% and 2-61% at 21 d in the same sediments. However, these behavioral changes were observed at the onset of exposure indicating MFB technique is a suitable and rapid screening level ecotoxicity assessment tool.

Assessing ecotoxicity of biomining effluents in stream ecosystems by in situ invertebrate bioassays: A case study in Talvivaara, Finland.

Mining of sulfide-rich pyritic ores produces acid mine drainage waters and has induced major ecological problems in aquatic ecosystems worldwide. Biomining utilizes microbes to extract metals from the ore, and it has been suggested as a new sustainable way to produce metals. However, little is known of the potential ecotoxicological effects of biomining. In the present study, biomining impacts were assessed using survival and behavioral responses of aquatic macroinvertebrates at in situ exposures in streams. The authors used an impedance conversion technique to measure quantitatively in situ behavioral responses of larvae of the regionally common mayfly, Heptagenia dalecarlica, to discharges from the Talvivaara mine (Sotkamo, Northern Finland), which uses a biomining technique. Behavioral responses measured in 3 mine-impacted streams were compared with those measured in 3 reference streams. In addition, 3-d survival of the mayfly larvae and the oligochaete Lumbriculus variegatus was measured in the study sites. Biomining impacts on stream water quality included increased concentrations of sulfur, sulfate, and metals, especially manganese, cadmium, zinc, sodium, and calcium. Survival of the invertebrates in the short term was not affected by the mine effluents. In contrast, apparent behavioral changes in mayfly larvae were detected, but these responses were not consistent among sites, which may reflect differing natural water chemistry of the study sites. Environ Toxicol Chem 2017;36:147-155. © 2016 SETAC.

Inconsistency in the analysis of morphological deformities in chironomidae (Insecta: Diptera) larvae.

The incidence of morphological deformities of chironomid larvae as an indicator of sediment toxicity has been studied for decades. However, standards for deformity analysis are lacking. The authors evaluated whether 25 experts diagnosed larval deformities in a similar manner. Based on high-quality digital images, the experts rated 211 menta of Chironomus spp. larvae as normal or deformed. The larvae were from a site with polluted sediments or from a reference site. The authors revealed this to a random half of the experts, and the rest conducted the assessment blind. The authors quantified the interrater agreement by kappa coefficient, tested whether open and blind assessments differed in deformity incidence and in differentiation between the sites, and identified those deformity types rated most consistently or inconsistently. The total deformity incidence varied greatly, from 10.9% to 66.4% among experts. Kappa coefficient across rater pairs averaged 0.52, indicating insufficient agreement. The deformity types rated most consistently were those missing teeth or with extra teeth. The open and blind assessments did not differ, but differentiation between sites was clearest for raters who counted primarily absolute deformities such as missing and extra teeth and excluded apparent mechanical aberrations or deviations in tooth size or symmetry. The highly differing criteria in deformity assignment have likely led to inconsistent results in midge larval deformity studies and indicate an urgent need for standardization of the analysis.