Risk Threshold and Assessment of Chloramphenicol Antibiotics in Sediment in the Fenhe River Basin, China.

Chloramphenicol antibiotics (CAs) are broad-spectrum antibiotics which are widely used in the prevention and treatment of infectious diseases in livestock and poultry breeding. However, overused CAs can enter the watershed and eventually enter the sediment. Antibiotics in sediment can cause secondary pollution through disturbance and suspension. In this study, taking the Fenhe River Basin as the research area, the risk of CAs in sediment were assessed by collecting sediment samples. The results showed that CAs were detected in all sediment samples of the Fenhe River Basin. The mean concentration of CAs was 79.1 µg/kg, and the concentration of thiamphenicol (THI) was dominant, which was up to 58.3 µg/kg. Temporally, there are great differences in different seasons; the concentration of CAs was higher in winter than that in summer, up to 4.79-174 times. Spatially, the mean concentration of CAs in midstream was 83.5 µg/kg, which was higher than that in the upstream and downstream. The concentration of CAs in tributaries were generally higher than that in the main stream, and the mean concentration of tributaries was 1.1 times that of the main stream. CAs in S2 (Lanhe River) was the most prominent among all sample sites; the concentration of CAs was 190.8 µg/kg. The risk threshold of CAs in the sediment was calculated using the Equilibrium Partitioning approach (EqP), based on the distribution coefficient (Kp) and the predicted no-effect concentration (PNEC) in the water, and the values were 0.091-1.44 mg/kg. Based on the risk threshold, the ecological risk of the CAs in sediment was assessed using risk quotients (RQ). The results showed that the Chloramphenicol (CHL) was the most prominent in the Fenhe River Basin, and the proportion of medium-risk areas reached 21.7%, while all the other areas showed low risk. Secondly, the proportion of medium-risk areas was 17.4% for THI, and all the other areas showed low risk. The risk for Florfenicol (FF) was least among all CAs, and the proportion of low-risk areas was only 8.7%, while all the other areas were of insignificant risk.

Multi-scenario simulation of ecological risk assessment based on ecosystem service values in the Beijing-Tianjin-Hebei region.

In this study, a framework for ecological risk assessment based on ecosystem service values and risk probability was established. Remote sensing was used to estimate the value of ecosystem services at the regional scale. Considering the natural and anthropogenic factors and using the entropy weight method to assign weights, probability index was constructed. In addition, multiple scenarios based on the ordered weighted averaging (OWA) method were simulated to reduce subjective uncertainty in the assessment. The results showed that the ecosystem service values generated by the gas regulation value accounted for the largest proportion, with a ratio of 46% in the Beijing-Tianjin-Hebei region. From 2005 to 2015, the value of ecosystem services decreased, falling by 2.5 × 107 Yuan. The level of ecological risk was relatively high, with a corresponding area ratio of 32.89%. Spatially, the areas with high risk were concentrated in the southeastern areas, and areas with relatively low risk were distributed in the western and northern areas. This high risk was probably caused by urbanization which was characterized by reduction of farmland and increase in impervious surface. Multi-scenario simulation showed that the areas of unstable ecological risk zones covered 30% and were mainly concentrated in the surroundings of developing cities. In areas of unstable risk distribution, the relationship between development and protection should be considered. This framework increases the reliability and practicability of ecological risk assessment results and has potential application value for regional risk control in the context of urbanization.

Occurrence, source apportionment and source-specific risk assessment of antibiotics in a typical tributary of the Yellow River basin.

The spatial distributions, sources, and source-specific risk apportionments of 26 antibiotics (5 categories) in the Fenhe River basin were determined based on sample data. The results showed that antibiotics were widely distributed in the surface water. There were significant differences between the different types of antibiotics, and the highest mean concentration was that of the sulfonamide category (33.74 ng/L), accounting for 36% of the total antibiotic concentration. Spatially, all antibiotics were mainly detected in the middle and downstream areas. The ecological risk assessment results showed that the significant risk rate of antibiotics accounted for 70% and was mainly distributed in the downstream area; however, the risks differed between the 5 categories. Quinolone antibiotics exhibited the highest significant risk rate, reaching 100%. The ecological risk associated with sulfamethoxazole was the highest among all detected antibiotics. The following five main factors influenced the antibiotic concentrations: aquaculture, pharmaceutical wastewater, livestock discharges, domestic sewage, and sewage treatment plants. Among these, pharmaceutical wastewater sources contributed the most (35%) to the total antibiotic concentration, and were distributed throughout the river. Although livestock discharges were not the main reason for the high level of ecological risk, these discharges were highest at certain sites in the midstream region. Different pollution sources posed different levels of ecological risk to the Fenhe River basin, the highest of which was pharmaceutical wastewater with a significant risk rate of 58%.

Pollution characteristics, risk assessment, and source apportionment of heavy metals in road dust in Beijing, China.

To analyze the spatial distribution patterns, risks, and sources of heavy metals (As, Cd, Cr, Cu, Hg, Mn, Ni, Pb, Zn, Fe), 36 road dust samples were collected from an urbanized area of Beijing in June 2016. The mean concentration of most metals, except As and Mn, exceeded their corresponding background values, with the mean concentration of Cd being 8 times that of its background. Spatially, for most heavy metals, except As and Mn, the high concentration areas were mainly within the 5th ring road, especially the northern area. The geo-accumulation index of Cd and Cu indicated moderate contamination at many sites. The entire study area was prone to potential ecological risks, with higher risks within the 4th ring road. Cd caused high potential ecological risk at most sites. According to the health risk assessment results, the non-carcinogenic risks that human beings suffered from heavy metals were insignificant. However, the carcinogenic risks due to Ni and Cr exceeded the acceptable level. Based on the source apportionment using positive matrix factorization, four factors were defined for the heavy metals. Factor 1, which was traffic-related exhaust, accounted for 34.47% of the concentration of heavy metals. The contributions of Factors 2 and 3 were approximately 25% each. Factor 2 was potentially related to coal combustion, while Factor 3 could be related to the manufacture and use of metal components. Factor 4, which could be related to the use of pesticides, fertilizers, and medical devices, accounted for 14.88%, which was the lowest.

Spatial-temporal distribution and risk assessment of mercury in different fractions in surface sediments from the Yangtze River estuary.

The temporal and spatial distributions of mercury in different fractions and its potential ecological risk were investigated in sediments from the Yangtze River estuary (YRE) by analyzing data collected from the study area. The results showed that mercury in the organic and residual fractions had dominant proportions, from 15.2% to 48.52% and from 45.96% to 81.59%, respectively. The fractions were more susceptible to seasonal changes than other fractions. Higher proportions of mercury in organic fraction were found in wet seasons; the opposite was true for mercury in residual fraction. With respect to the spatial distribution, the concentration mercury in exchangeable, carbonate and Fe-Mn oxide fractions showed a decreasing trend from the inner estuary to the outer estuary, but no obvious trends were found in the distributions of mercury in the organic and residual fractions. The risk assessment code (RAC) was used to evaluate the potential ecological risk in the study area based on the proportions of exchangeable and carbonate fractions. The average RAC values during the four periods were 6.00%, 2.20%, 2.83%, and 0.61%. Although these values show that the risk in the study area is generally low, the distribution of RAC values indicates that the inner estuary has a medium risk, with a value up to 10%.

Bioavailability and risk assessment of arsenic in surface sediments of the Yangtze River estuary.

The bioavailability and risk assessment of As were studied in sediments of the Yangtze River estuary (YRE). Results showed that residual fractions dominated the As partition (>85%), which attenuated overall bioavailability. After the residual fraction, As mainly partitioned into the Fe-Mn oxides fraction (3.16-4.22%). Arsenic bound to Fe-Mn oxides was higher in wet seasons. The carbonate fraction was minimal, which may result from the negative state presence of As in sediments. According to the risk assessment code, the YRE was classified as low risk. Additionally, the reduction of As(V) to As(III) may occur due to the reducing condition in wet seasons. Considering As(III) is more toxic and mobile, As bound to the exchangeable and Fe-Mn oxides fractions may have more potential ecological risk. Thus, the speciation and fraction should be both considered on the ecological risk of As in sediments of the YRE.

Application of spatial Markov chains to the analysis of the temporal-spatial evolution of soil erosion.

Soil and water conservation in the Three Gorges Reservoir Area of China is important, and soil erosion is a significant issue. In the present study, spatial Markov chains were applied to explore the impacts of the regional context on soil erosion in the Xiangxi River watershed, and Thematic Mapper remote sensing data from 1999 and 2007 were employed. The results indicated that the observed changes in soil erosion were closely related to the soil erosion levels of the surrounding areas. When neighboring regions were not considered, the probability that moderate erosion transformed into slight and severe erosion was 0.8330 and 0.0049, respectively. However, when neighboring regions that displayed intensive erosion were considered, the probabilities were 0.2454 and 0.7513, respectively. Moreover, the different levels of soil erosion in neighboring regions played different roles in soil erosion. If the erosion levels in the neighboring region were lower, the probability of a high erosion class transferring to a lower level was relatively high. In contrast, if erosion levels in the neighboring region were higher, the probability was lower. The results of the present study provide important information for the planning and implementation of soil conservation measures in the study area.

Risk assessment and uncertainty analysis of PAHs in the sediments of the Yangtze River Estuary, China.

To better explore the concentration of polycyclic aromatic hydrocarbons (PAHs) in the sediments of the Yangtze River Estuary (YRE), 16 priority PAHs were analyzed based on sampling data obtained in February 2011. The results showed that the total concentrations of PAHs in sediments of the YRE varied from 65.07 to 668.98ng·g-1. The results of toxic equivalent quantities of benzo[a]pyrene and the sediment quality guideline quotient suggested that PAHs had little or no adverse effects on the environment. The cancer risk results showed that the cancer risk at all sites exceeded 10-6, with 73% of sites exceeding 10-4, suggesting that people remain at risk of cancer as a result of their exposure to carcinogenic PAHs. However, the result of hazard index results showed that the non-cancer risks were substantially lower than one, indicating that PAHs in these sediments likely pose little or no adverse health threats to local inhabitants.

Spatial variation, environmental risk and biological hazard assessment of heavy metals in surface sediments of the Yangtze River estuary.

30 samples of eight heavy metals were collected in February 2011 within Yangtze River estuary (YRE). The mean concentrations met the primary standard criteria based on Marine Sediments Quality of China. The spatial distribution showed that a gradient concentration decreased gradually from inner-estuary to river mouth. Anthropogenic inputs might be the main contributor, and fine grained sediments might also aggravate the heavy metal contamination. The assessment results indicated that the YRE was in low risk of contamination caused by every single heavy metal. However, it was in considerable degree of contamination considering combination of all the heavy metals. The toxicities of heavy metals might be elevated when heavy metals were in combination. Arsenic should be of primary concern due to its higher assessment values and the potential of adverse biological effects. And the concentration of As in the YRE had a trend to increase because of anthropogenic activities nearby.

Cost-effectiveness and cost-benefit analysis of BMPs in controlling agricultural nonpoint source pollution in China based on the SWAT model.

Best management practices (BMPs) have been widely used in managing agricultural nonpoint source pollution (ANSP) at the watershed level. Most BMPs are related to land use, tillage management, and fertilizer levels. In total, seven BMP scenarios (Reforest1, Reforest2, No Tillage, Contour tillage, and fertilizer level 1-4) that are related to these three factors were estimated in this study. The objectives were to investigate the effectiveness and cost-benefit of these BMPs on ANSP reduction in a large tributary of the Three Gorges Reservoir (TGR) in China, which are based on the simulation results of the Soil and Water Assessment Tool (SWAT) model. The results indicated that reforestation was the most economically efficient of all BMPs, and its net benefits were up to CNY 4.36×10(7) years(-1) (about USD 7.08×10(6) years(-1)). Regarding tillage practices, no tillage practice was more environmentally friendly than other tillage practices, and contour tillage was more economically efficient. Reducing the local fertilizer level to 0.8-fold less than that of 2010 can yield a satisfactory environmental and economic efficiency. Reforestation and fertilizer management were more effective in reducing total phosphorus (TP), whereas tillage management was more effective in reducing total nitrogen (TN). When CNY 10,000 (about USD 162) was applied to reforestation, no tillage, contour tillage, and an 0.8-fold reduction in the fertilizer level, then annual TN load can be reduced by 0.08, 0.16, 0.11, and 0.04 t and annual TP load can be reduced by 0.04, 0.02, 0.01 and 0.03 t, respectively. The cost-benefit (CB) ratios of the BMPs were as follows: reforestation (207 %) > contour tillage (129 %) > no tillage (114 %) > fertilizer management (96 and 89 %). The most economical and effective BMPs can be designated as follows: BMP1 (returning arable land with slopes greater than 25° to forests and those lands with slopes of 15-25° to orchards), BMP2 (implementing no tillage on arable land with slopes less than 15°), and BMP5 (0.8-fold less than that of 2010).

Spatial variation, environmental assessment and source identification of heavy metals in sediments of the Yangtze River Estuary.

In order to analyze the spatial distribution patterns, pollution sources and ecological risks of heavy metals (As, Cd, Cr, Cu, Mn, Ni, Pb and Zn), 30 sediment samples were taken from in the Yangtze River Estuary (YRE). The results indicated that the contamination ranking of heavy metals was As>Cr>Cd>Ni>Mn>Pb>Zn>Cu. In the various areas, the pollution magnitude decreased as follows: adjacent sea>river mouth>inner-region. Compared to data published for other regions, the YRE data indicated that the sediment was not severely contaminated by heavy metals. In the YRE, natural and anthropogenic inputs dominated the distribution patterns of the heavy metals. Beyond that, the hydrodynamic conditions, such as the Taiwan warm current, coastal current and Yangtze diluted water, also caused distribution variations in the study areas.

Assessment of nitrogen and phosphorus loads and causal factors from different land use and soil types in the Three Gorges Reservoir Area.

It is important to identify nitrogen (N) and phosphorus (P) from non-point sources (NPS) to protect watershed water quality. However, few studies have been conducted in a large basin to determine the sources and causal factors of N and P from multiple land use and soil types. In this study, the Soil and Water Assessment Tool (SWAT) was applied in support of the Small-scale Watershed Extended Method (SWEM) in the Three Gorges Reservoir Region (TGRR), China. The first-order error analysis (FOEA) was used to identify the key sub-processes that affected the occurrence of NPS pollution. Based on this study, runoff from the dry land and paddy fields was enriched with nutrients, while runoff from purplish soils, paddy soils and yellow earths made up the largest amount of nutrient loads. The results showed that the contributions of individual parameters to the total uncertainty were different among land use and soil types. This study indicated that management efforts for dry land must explicitly account for conservation practices and proper land covers, while conscientious fertilization practices would result in a greater decrease of NPS yields for paddy fields. Grazing practices should be considered for the purpose of N management for yellow earths, while plant density is important to control soil erosion for purple soils.

[Risk assessment of nitrogen and phosphorus export in upper reach of Daliao river watershed].

With the development of point pollution control, non-point source pollution has become an important environmental and water quality management problem. Land cover composition across a watershed is a dominant factor in controlling the amount of nitrogen and phosphorus exported from a watershed. Generally, urban and agricultural land covers are considered as principal sources of excess loads of nitrogen (N) and phosphorous (P) in receiving waters. A well developed literature of nutrient export coefficients by land-cover class was used to model the risk of equaling or exceeding specified levels of nutrient export in drainage basin of Dahuofang Reservoir. The model was applied to about 513 comparatively small watersheds mapped for the drainage basin of Dahuofang Reservoir for environmental analysis and planning. The results suggest that the probabilities of risk are 19.31% and 8.95% for N and P nutrient respectively. As the spatial distribution concerned, risk estimates generally differed with different slope degrees and districts. Risk estimates generally increased from the places where lies near the rivers to the places where are far from the river, but numerous areas of high variability were evident.

[Regional environment risk assessment and probability distribution of topsoil PAHs in Tianjin area].

Based on some foreign standards of soil PAHs assessment, regional environment risk assessment of topsoil PAHs in Tianjin Area was discussed using the method of indicator Kriging. The results using different standards are also compared. It is shown that Bap is the only one component which exceeds the preliminary remedial goals and risk based concentration of U.S. in Tianjin area and the regions of exceeding standards are about 8.12% and 2.34% respectively. Most components of soil PAHs in Tianjin area are exceed the standard of Holland. The regions of exceeding standard are mostly 90% except the components of Ant (5.26%) and Bas (68.42%). Otherwise, the regions of exceeding Canada standard are mostly under 5% except Nap (97.89%), Phe (56.84%) and Pyr (47.65%). Based on the Soil Plan Zealand of Denmark, Nap is the only one component which exceeds the standard in Tianjin area and the region is about 9.26%. Comparing these risk distribution maps and spatial distribution maps of PAHs, it is found that the areas with high risk are mainly fallen in the areas with high concentrations of PAHs. The probability maps of PAHs risk are helpful for regional environmental management and planning.

Parameter uncertainty analysis of the non-point source pollution in the Daning River watershed of the Three Gorges Reservoir Region, China.

The generation and formation of non-point source pollution involves great uncertainty, and this uncertainty makes monitoring and controlling pollution very difficult. Understanding the main parameters that affect non-point source pollution uncertainty is necessary to provide the basis for the planning and design of control measures. In this study, three methods were adopted to do the parameter uncertainty analysis with the Soil and Water Assessment Tool (SWAT). Based on the results of parameter sensitivity analysis by the Morris screening method, the ten parameters that most affect runoff, sediment, organic N, nitrate, and total phosphorous (TP) were chosen for further uncertainty analysis. First-order error analysis (FOEA) and the Monte Carlo method (MC) were used to analyze the effect of parameter uncertainty on model outputs. FOEA results showed that only a few parameters had significantly affected the uncertainty of the final simulation results, and many parameters had little or no effect. The SCS curve number was the parameter with significant uncertainty impact on runoff, sediment, organic N, nitrate and TP, and it showed that the runoff process was mainly responsible for the uncertainty of non-point source pollution load. The uncertainty of sediment was the biggest among the five model output results described above. MC results indicated that neglecting the parameter uncertainty of the model would underestimate the non-point source pollution load, and that the relationship between model input and output was non-linear. The uncertainty of non-point source pollution exhibited a temporal pattern: It was greater in summer than in winter. The uncertainty of runoff was smaller compared to that of sediment, organic N, nitrate, and TP, and the source of uncertainty was mainly affected by parameters associated with runoff.