CSRQ: Communication-Efficient Secure Range Queries in Two-Tiered Sensor Networks.

In recent years, we have seen many applications of secure query in two-tiered wireless sensor networks. Storage nodes are responsible for storing data from nearby sensor nodes and answering queries from Sink. It is critical to protect data security from a compromised storage node. In this paper, the Communication-efficient Secure Range Query (CSRQ)-a privacy and integrity preserving range query protocol-is proposed to prevent attackers from gaining information of both data collected by sensor nodes and queries issued by Sink. To preserve privacy and integrity, in addition to employing the encoding mechanisms, a novel data structure called encrypted constraint chain is proposed, which embeds the information of integrity verification. Sink can use this encrypted constraint chain to verify the query result. The performance evaluation shows that CSRQ has lower communication cost than the current range query protocols.

[Quantification of Nitrate Sources to Groundwater in Karst Trough-valley Areas Based on Dual Stable Isotopes of δ15N-NO3- and δ18O-NO3- and the IsoSource Model].

Due to the vulnerability of karst hydrological systems, nitrate pollution in karst groundwater has become a global common and serious environmental problem. In order to ensure drinking water safety, it is very important to accurately identify groundwater nitrate sources. The groundwater hydrochemistry and δ15N-NO3- and δ18O-NO3- isotopes were analyzed in samples taken from a suburb of Chongqing:the Longfeng karst trough-valley, which is mainly affected by agricultural activities, and the Longche karst trough-valley, which is primarily affected by urbanization. The IsoSource model was then used to quantify the groundwater nitrate sources. The results showed that:① The NO3- concentration in groundwater ranged from 19.31 mg·L-1 to 37.01 mg·L-1(mean of 28.21 mg·L-1) in the Longfeng karst trough-valley, and from 2.15 mg·L-1 to 27.69 mg·L-1(mean of 10.31 mg·L-1) in the Longche karst trough-valley. The groundwater NO3- concentration exhibited an obvious seasonal variation in both valleys. ② The δ15N-NO3- and δ18O-NO3- isotopes in groundwater in the Longfeng karst trough-valley ranged from 3.29‰ to 11.03‰ (mean of 6.74‰) and 0.88‰ to 7.51‰ (mean of 3.18‰), respectively. In contrast, groundwater in the Longche karst trough-valley presented higher δ15N-NO3- and δ18O-NO3- values that ranged from 5.25‰ to 11.40‰ (mean of 7.95‰) and 2.90‰ to 19.94‰ (mean of 11.18‰), respectively. The lower values of δ15N-NO3- and δ18O-NO3- in groundwater in the Longfeng karst trough-valley suggest that groundwater NO3- was mainly sourced from agricultural N fertilizer, while the higher values of δ15N-NO3- and δ18O-NO3- in groundwater in the Longche karst trough-valley indicate that groundwater NO3- was primarily sourced from domestic sewage. Moreover, such δ15N-NO3- and δ18O-NO3- values in groundwater indicate that nitrification was the primary process for nitrogen conversion in both valleys. Meanwhile, significant seasonal differences in groundwater δ15N-NO3- and δ18O-NO3- were observed in both valleys; the δ15N-NO3- and δ18O-NO3- values were higher during the dry season (means of 8.83‰ and 2.79‰, respectively) than during the rainy season (means of 4.64‰ and 3.58‰, respectively) in the Longfeng karst trough-valley, whereas the δ15N-NO3- and δ18O-NO3- values were lower during the dry season (means of 9.79‰ and 14.56‰, respectively) than during the rainy season (means of 5.12‰ and 7.8‰, respectively) in the Longche trough-valley. This suggests that there were differences in the seasonal NO3- sources to groundwater in both valleys. During the rainy season, the groundwater NO3- concentration in the Longfeng karst trough-valley was mainly due to the nitrification of NH4+ in precipitation and fertilizer as well as organic nitrogen in soil, whereas during the dry season, the groundwater NO3- concentration primarily originated from domestic sewage. In contrast, the groundwater NO3- concentration in the Longche karst trough-valley primarily originated from domestic sewage in both seasons. ③ The results of the IsoSource model indicated that the nitrification of NH4+ from fertilizer and rainwater was the primary NO3- source to groundwater (44.63% of the total) in the Longfeng trough valley, and was followed by domestic sewage (29.5%), soil organic nitrogen (22.38%), and NO3- from rainwater and fertilizer (<10%). During the rainy season, the groundwater NO3- concentration was mainly due to the nitrification of NH4+ from fertilizer and rainwater (52.25% of the total) in Longfeng trough-valley, while groundwater NO3- concentration primarily originated from domestic sewage during the dry season (41% of the total). In contrast, the groundwater NO3- concentration was mainly from domestic sewage (36.17%) in Longche karst trough-valley, and was followed by the nitrification of NH4+ from fertilizer and rainwater (23.5%), soil organic nitrogen (22.5%), and NO3- from rainwater and fertilizer (<10%). The groundwater NO3- concentration in the Longche karst trough-valley primarily originated from domestic sewage in both seasons, and accounted for 47% and 25% during the rainy season and dry season, respectively.

[Phosphorus Forms and Release Risk of Sediments in Urban Sewage Treatment Plant Effluent and Receiving Stream Reach].

From October 2018 to April 2019, the surface sediment and overlying water samples were collected every two months from the upstream and downstream of the effluent outlet of the Caitianpu sewage treatment plant in the Banqiao River, Hefei City. The effects of the sewage treatment plant effluent on both phosphorus forms and the equilibrium phosphate concentration (EPC0) in sediments were analyzed. The response of equilibrium phosphate concentration to external carbon (sodium acetate) and the release risk of phosphorus in sediments were investigated. Result show that the phosphorus pollution in Banqiao River was more severe. The average values of total phosphorus in the sediments at the upper and lower effluent outlet were 789.39 mg·kg-1 and 854.41 mg·kg-1, respectively, and the average bio-available phosphorus amounts were 157.19 mg·kg-1 and 173.37 mg·kg-1, respectively. The EPC0 values of the four sampling points decreased in the order SP1 > SP2 > SP3 > CP, indicating that the sewage treatment plant effluent increased the EPC0 level and phosphorus release risk of the stream sediments. Moreover, the addition of exogenous carbon significantly decreased the EPC0 value of the sediment, especially in SP1, suggesting that the addition of exogenous carbon decreased the risk of phosphorus release from sediments.

[Effects of Photosynthesis of Submerged Aquatic Plants on CDOM in a Karst Water System: A Case Study from Xueyu Cave, Chongqing, China].

Dissolved organic matter (DOM) in karst water is one of the most important carbon sink components, whose origins, distributions, and transport processes are of significance to carbon sink studies. Chromophoric dissolved organic matter (CDOM) can be utilized to express the composition and structural properties of DOM. In this paper, water samples were collected monthly from Xueyu Cave in a karst underground river from both inside and outside the cave. The changes in hydrochemistry and CDOM spectral characteristics as well as the influencing factors for CDOM changes were studied, with the aim of providing experimental support for carbon sink fluxes in karst processes. The main results were as follows. ① The dominant type of CDOM in Xueyu Cave karst water consisted of small molecular weight organic matter that was autochthonously derived and easily bio-degraded, and the tryptophan-like and tyrosine-like components accounted for more than 60% of the total CDOM. ② The most effective influencing factor inside the cave was microbes, which degraded the small molecular DOM in groundwater and induced slight decreases in the TOC and DOC concentrations; they also increased the humic index (HIX). ③ However, the dominant factor outside the cave was submerged aquatic plant photosynthesis, which induced significant increases in the TOC and DOC concentrations and autochthonous small molecular weight DOM contents.