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Fourteen field campaigns were conducted in five inland lakes during different seasons between 2006 and 2013, and a total of 398 water samples with varying optical characteristics were collected. The characteristics were analyzed based on remote sensing reflectance, and an automatic cluster two-step method was applied for water classification. The inland waters could be clustered into three types, which we labeled water types I, II and III. From water types I to III, the effect of the phytoplankton on the optical characteristics gradually decreased. Four chlorophyll-a retrieval algorithms for Case II water, a two-band, three-band, four-band and SCI (Synthetic Chlorophyll Index) algorithm were evaluated for three water types based on the MERIS bands. Different MERIS bands were used for the three water types in each of the four algorithms. The four algorithms had different levels of retrieval accuracy for each water type, and no single algorithm could be successfully applied to all water types. For water types I and III, the three-band algorithm performed the best, while the four-band algorithm had the highest retrieval accuracy for water type II. However, the three-band algorithm is preferable to the two-band algorithm for turbid eutrophic inland waters. The SCI algorithm is recommended for highly turbid water with a higher concentration of total suspended solids. Our research indicates that the chlorophyll-a concentration retrieval by remote sensing for optically contrasted inland water requires a specific algorithm that is based on the optical characteristics of inland water bodies to obtain higher estimation accuracy. [ABSTRACT FROM AUTHOR]

In the water shortage countries and areas, untreated sewage irrigation led to the extensive organic pollution of farmland soil, which seriously threatened environmental security. In this study, we selected Shenfu irrigation area (SIA) as the study area, and it was the first and largest organic sewage irrigation area in China. We analyzed the temporal and spatial variations in concentrations, risk and sources of polycyclic aromatic hydrocarbons (PAHs) in soil of the SIA. The results show that the PAH concentrations decreased slowly and environmental risk fluctuated after stopping sewage irrigation. However, the correlation and divergence analysis indicate that PAHs in surface soils might be derived from traffic emissions besides sewage irrigation. Based on factor analysis with non-negative constraints, the contribution of irrigation decreased from 92.9% to 59.4%, and contribution of traffic increased from 7.1% to 40.6%. Thus, the superposition of the residual PAHs from sewage irrigation and the new input PAHs from traffic emission should be considered for the pollution control. [ABSTRACT FROM AUTHOR]

Abstract Heavy metal cadmium (Cd) pollution in farmland has become a serious threat to food security globally. In this work, a grafting technique was applied to eggplant (Solanum melongena) and tomato (Solanum lycopersicum) plants using Solanum torvum as rootstock to investigate effects of grafting on Cd accumulation in shoots. The un-grafted, self-grafted, and grafted plants were grown in soils containing 2 mg kg−1 Cd. Results showed that grafting on S. torvum could efficiently reduce Cd accumulation in leaves of eggplant and tomato, and the decrease was 89% and 72%, respectively. With S. torvum as rootstock, Cd concentrations were 1.11 mg kg−1 and 6.58 mg kg−1 in leaves of grafted eggplant and tomato, which were significantly decreased as compared with un-grafted plants (10.12 mg kg−1 and 23.19 mg kg−1, respectively, p < 0.05). In addition, Cd concentrations were 12.11 mg kg−1 and 29.47 mg kg−1 in leaves of self-grafted eggplant and tomato, respectively, which was similar to those in un-grafted eggplant, but more than those in un-grafted tomato (p < 0.05). This suggests that the S. torvum rootstock, and not the grafting operation, was responsible for efficient reduction of Cd accumulation in shoots of eggplant and tomato plants. Furthermore, total sulfur and sulfate (SO 4 2−) concentrations analysis revealed that there was a similar trend between Cd accumulation and total sulfur or SO 4 2− concentrations in leaves of plants tested. Additionally, a strong positive correlation between Cd accumulation and total sulfur or SO 4 2− concentrations occurred in leaves of eggplant and tomato plants. Thus, sulfur, mainly SO 4 2−, in leaves may play an important regulatory role in Cd accumulation of eggplant and tomato plants. This study provides the theoretical and technical support for applying grafting technique for the safe practice of farming in Cd-contaminated agricultural soil. Graphical abstract Unlabelled Image Highlights • Grafting on S. torvum greatly reduced Cd accumulation in eggplant or tomato leaves. • Self-grafting did not directly redcue Cd accumulation in eggplant or tomato. • A close positive correlation occurred between Cd and sulfur accumulation in leaves. [ABSTRACT FROM AUTHOR]

Abstract This study is devoted to addressing the effects of algae blooms on sulfur cycle and the consequent phosphorus mobility in the sediments of freshwater lake ecosystems. A mesocosm experiment was conducted to investigate these effects through monitoring the dynamics of sulfur (S), iron (Fe) and phosphorus (P) in water and sediments, and their diffusion fluxes at the sediment-water interface (SWI). In addition, the abundance of sulfate-reducing bacteria (SRB) in the water column was also detected. The addition of the algae lead to an increase of SRB, a drastic decline of sulfate and a significant increase of total dissolved sulfide (ΣS2−, the peak value of near 3.0 mmol/L on day 6) in the water column. These results suggest the sulfate reduction was dramatically promoted during algae decomposition. Indeed the ΣS2− was 2 to 3 times of SO 4 2− initial concentration, and higher ΣS2− was produced with higher algal biomass. Moreover, the diffusive flux of ΣS2− at the SWI was negative, indicating that diffusion of ΣS2− from water column toward sediment was occurring. These results indicated that algae decomposition might also be another important source of ΣS2− (termed "algae-derived ΣS2−") in addition to sulfate reduction. The increase of Fe(II) in surface sediment pore-water was slightly delayed compared to the ΣS2− generation in the water column, which illustrated that Fe oxyhydroxides in sediments were transformed into Fe(II) through chemical reduction of ΣS2−. Concomitantly, the vertical distribution of PO 4 3− in high amounts algae group suggested that desorption and release of iron oxides-bound PO 4 3− occurred in sediments. Collectively, algae bloom can boost the lake eutrophication not only through direct release of nutrients but also through the high production of ΣS2−and indirect promotion of phosphorus mobility in sediment. Graphical abstract Unlabelled Image Highlights • Algae blooms significantly affect sulfide production and P mobility in sediments. • Abundant ΣS2− can be produced from algae decomposition (termed "algae-derived ΣS2−"). • ΣS2− diffused from water column to sediments can affect Fe and P cycles. • Iron reduction in sediments can be promoted by the chemically mediated of ΣS2−. • P mobility in sediments can be dramatically influenced by the reduction of iron oxides. [ABSTRACT FROM AUTHOR]

After large-scale outbreaks of algal blooms in eutrophic water, considerable amounts of algae residue accumulate in near-shore zones before fermenting rapidly and becoming malodorous. Taste and odor pollution caused by secondary metabolites from cyanobacterial blooms has become a serious and widespread environmental problem. Two typical odorous compounds, β-cyclocitral and β-ionone, have gained increasing attention in recent years. In this paper, the spatial distributions of β-cyclocitral and β-ionone in the sediments and overlying water off the west shore of Taihu Lake were investigated. The results showed that β-cyclocitral, β-ionone and nutrients are released during the degradation of fresh cyanobacteria, especially in the early stages. The odorous compounds and nutrients greatly decreased as the depth of sediment increased, indicating that reed roots can absorb β-cyclocitral, β-ionone and nutrients. Furthermore, removing cyanobacteria and dredging sludge might reduce the release of β-cyclocitral and β-ionone. [ABSTRACT FROM AUTHOR]