Accumulation and Elimination Kinetics of 2-Methylisoborneol in Crucian Carp (Carassius carassius)

2-methylisoborneol(2-MIB) is a common, earthysmelling compound that causes taste and odor issues in aquaculture. To quantify the distribution, absorption, and depuration of 2-MIB in crucian carp(Carassius carassius), we detected and measured 2-MIB it via microwave, headspace solid-phase microextraction(HS-SPME), and gas chromatography before and after exposing fish to two different concentrations of 2-MIB(200 ng/L and 500 ng/L). The results showed that during the exposure time, the fish absorbed 2-MIB rapidly within 4 h. After exposure to 2-MIB for 120 h, the 2-MIB in gill and liver were rapidly removed. The processes of accumulation and elimination of 2-MIB in fish were investigated using the one-compartment kinetic model. The modeling results showed that the range of the uptake rate constant(k1) was 0.49-6.91. The range of the elimination rate constant(k2) was 0.05-0.27 and uptake rates were higher than elimination rates. The bioconcentration factor(BCF) was estimated according to the physicochemical properties of 2-MIB, and the bioaccumulation of 2-MIB in fish had a close correlation with the octanol/water partition coefficient(Kow).

Spatiotemporal variations of CO_(2) fluxes in a Cynodon-dominated riparian zone of the Three Gorges Reservoir(TGR),China

Aims Riparian ecosystems play an important role in overall ecosystem function,including the global carbon cycle of terrestrial ecosystems,at both landscape and global scales.Yet few studies have reported in situ measurements of CO_(2) in riparian areas where flooding is a unique disturbance to carbon cycling.Methods At multiple locations across riparian zones(RZ)with different water submergences in Xiangxi Bay(XXB),we studied seasonal variations of CO_(2) exchange between this Cynodon-dominated community and the atmosphere for 2 years by using static chambers.Important Findings We found that the seasonal changes in CO_(2) fluxes were apparent and dependent on the biophysical environment.In the beginning of spring,low gross primary productivity(GPP)in lightly flooded zones(LFZ)resulted in a positive net ecosystem exchange(NEE),indicating a net CO_(2) source.With the increase in temperature,more species and vegetation abundance appeared,and the increased GPP turned the LFZ from a net CO_(2) source into a sink.This transi-tion seemed predominantly controlled by the physiological growth of vegetation.The mean NEEs,REs and the light-use efficiency(α)of the vegetation at HFZ and MFZ were significantly higher than those at LFZ and UFZ.Yet the coefficients of variation(CV)of NEE and RE at MFZ and HFZ were lower than those at LFZ and UFZ.Submergence promoted the emission and uptake of CO_(2) to the atmosphere.Elongated submergence reduced the number of spe-cies and lowered the spatial variability of the RZ,further lowering the variation of the CO_(2) exchange.

Olfactory Threshold Concentration of Two Typical Earthy-Musty Odour Compounds in Black Carps and Bighead Carps

2-methylisoboneol(2-MIB)and geosmin are two typical earthy-musty odour compounds in freshwater.In order to investigate the olfactory thresholds of 2-MIB and geosmin in black carp(Mylopharyngodon piceus)and bighead carp(Hypophthalmichthys nobilis),an improved and optimized pre-treatment method of adsorbing the earthy-musty odours combined with the technology of gas chromatography following microwave distillation-headspace solid-phase microextraction was developed.The fish back muscle samples were placed in vials with the 2-MIB/geosmin solution and reached the adsorption equilibrium.Some samples were evaluated by a panel of ten members using Flavour Profile Analysis(FPA)method,the remaining sample was used for instrumental analysis.In fish muscle blocks,it took 90 and 105 min to establish the absorption equilibrium of 2-MIB and geosmin,respectively.The olfactory thresholds of 2-MIB in the bodies of black carps and bighead carps were 0.35μg/kg and 0.30μg/kg,respectively,while the geosmin thresholds were 0.59μg/kg and 0.51μg/kg,respectively.The concentrations of 2-MIB and geosmin in the bodies of black carps were slightly higher than in bighead carps,which were probably caused by the differences in the body fat content and the volatility of 2-MIB and geosmin.

Reduction of Soil Cadmium Bioavailability by Using Industrial Byproduct Phosphorus Slag

In this study,an alternative and cost-effective industrial byproduct phosphorus slag(PS)was utilized to treat simulated Cd-contaminated soil.The modified European Community Bureau of Reference(BCR)sequential extraction procedure was applied to assess the ability of PS to reduce Cd mobility in contaminated soil by the incubation experiments.The results showed 2%(W/W)PS reduced the exchangeable fraction of Cd by 99.7%,which also increased the pH,electrical conductivity,cation exchange capacity,available phosphorus,and available silicon of the soil.The results suggested that the PS could decrease Cd bioavailability and improve soil nutrition.This was demonstrated by the pot experiments.The Cd accumulation in both pakchoi(Brassica chinensis L.)leaf and root was reduced along with the reduction of the Cd translocation factor(TF)and the bioaccumulation factors(BCF)in pakchoi.In Cd-contaminated soil(3.16 mg·kg^–1),the 2%(W/W)PS reduced the Cd content in the leaf and root of pakchoi by 70.7%and 58.7%,respectively.Meanwhile,the increase of the chlorophyll content in pakchoi and the promotion of pakchoi root system development suggested healthy plant growth in the PS treated soil.