[Vertical Pollution Characteristics and Source Analysis of Soil PAHs in Different Land Use Types].

In order to study the vertical pollution characteristics of polycyclic aromatic hydrocarbons (PAHs) in soils of different land use types in suburban areas of Nanjing, 15 types of controlled PAHs were studied in each section (0-100 cm) of soils from six different land use types, including a vegetable field, forestland, residential area, urban land, paddy field, and industrial area. The vertical distribution and composition characteristics, influencing factors, and sources of PAHs were analyzed. The results showed that:the total concentrations of Σ15PAHs in the six sampling site profiles were as follows:vegetable field (69.3-299.2 µg·kg-1), forestland (20.8-128.3 µg·kg-1), residential area (30.7-142.1 µg·kg-1), urban land (185.6-1728.7 µg·kg-1), paddy field (208.3-693.0 µg·kg-1), and industrial area (165.6-739.2 µg·kg-1). There was no pollution in the residential area or forestland and a light pollution level in the vegetable field, medium pollution level in the paddy field and industrial area, and more serious pollution in the urban land. Soil PAHs were mainly distributed in the surface or subsurface layer, except in the residential area and urban land; however, they were still detected in the deep layers, and high-molecular-weight PAHs were dominant in most depths and sampling sites. The vertical distribution and migration of PAHs in soils were affected by molecular characteristics and component concentrations of PAHs, soil physical and chemical properties, and land use types. PMF source analysis indicated that coke sources, traffic sources, and coal combustion sources from human activities were the main sources of PAHs in this study region.

[Pollution Characteristics and Risk Assessment of Polycyclic Aromatic Hydrocarbons in Agricultural Soils of Different Land Use Types in Nanjing Suburbs].

In order to clarify the pollution characteristics of PAHs in suburban agricultural soils, the content of 16 types of PAHs was measured in agricultural soils with different land use types (paddy fields, vegetable fields, and forest land) in the suburbs of Nanjing. The results showed that acenaphthene (Acy) was not detected in any soil samples. The concentration of 15 PAHs in agricultural soil in suburban Nanjing ranged from 24.49 to 925.54 µg·kg-1, with an average concentration of 259.88 µg·kg-1. In different land use types, the order of PAHs concentration in soil from high to low was:forest land>paddy fields>vegetable fields, and the high-ring PAHs content was dominant in general. The effects of different soil physicochemical properties on PAHs showed that there was a certain correlation between soil organic carbon (TOC) and clay (clay) content and PAHs, whereas pH and total nitrogen (TN) had no significant correlation with PAHs. The toxic equivalence method and CSI index method were used for ecological risk assessment, which showed that the ecological risk of PAHs in agricultural soils in suburban Nanjing was relatively small; however, the ecological risk of PAHs in forest land should be given some attention, and supervision should be strengthened. Health risk assessment using incremental lifetime cancer risk (ILCR) showed that the threat to the health of children was slightly greater than that of adults, and the CR of forest land was significantly higher than that of vegetable and paddy fields, though still within an acceptable range. Uncertain health assessments were performed in adults, showing that risk analyses of deterministic health risks underestimated the health risks of PAHs. The results of sensitivity analysis showed that the input parameter that had the greatest impact on the total variance of the total carcinogenic risk CR was the exposure frequency EF (50.7%), followed by the pollutant concentration CS (43.3%).

[Predicting soil property in hilly regions by using landscape and multiscale micro-landform features]. / 基于景观及微地形特征的丘陵区土壤属性预测.

To assess the high-resolution digital soil mapping method for small watersheds in hilly areas, we explored the role of landscape classification and multiscale micro-landform features in predicting soil pH, soil clay content (SCC), and cation exchange capacity (CEC). Geomorphons (GM) terrain classification method was used to create landform units. The traditional digital elevation model (DEM) derivatives and remote sensing variables were employed for different combinations with landscape and micro-landform classification variables, with further compa-rison and analysis being conducted. In addition, three machine learning techniques, including support vector machine (SVM), partial least squares regression (PLSR), and random forest (RF), were used to build prediction models. The best method was then selected, and then combined with regression kriging by modeling spatial structure of the model residuals. The results showed that the application of landscape and multiscale micro-landform classification variables effectively improved the prediction accuracy of pH, SCC, and CEC by 18.8%, 8.2% and 8.7%, respectively. The map of landscape classification that contained vegetation coverage information had greater model contribution than land use data. The GM classification map with 5 m resolution was more suitable for high-precision DSM than those with lower resolution. The composite model of RF performed the best in predicting SCC, while the pH and CEC were not suitable for adding the residual regression kriging on the basis of RF model. Finally, the combination of landscape and multiscale micro-landform classification variables, DEM derivatives and remote sensing variables had the highest prediction accuracy for all the three soil properties. This result indicated that multivariable contained more effective soil information than single data source for rolling areas. The landscape variables composed of GM and surface classified data explained about 40% of the spatial variation of tested soil attributes in hilly area. Therefore, multi-resolution GM and landscape classified variables could be included into the construction of prediction model in research of soil mapping.

Significant loss of soil inorganic carbon at the continental scale.

Widespread soil acidification due to atmospheric acid deposition and agricultural fertilization may greatly accelerate soil carbonate dissolution and CO2 release. However, to date, few studies have addressed these processes. Here, we use meta-analysis and nationwide-survey datasets to investigate changes in soil inorganic carbon (SIC) stocks in China. We observe an overall decrease in SIC stocks in topsoil (0-30 cm) (11.33 g C m-2 yr-1) from the 1980s to the 2010s. Total SIC stocks have decreased by ∼8.99 ± 2.24% (1.37 ± 0.37 Pg C). The average SIC losses across China (0.046 Pg C yr-1) and in cropland (0.016 Pg C yr-1) account for ∼17.6%-24.0% of the terrestrial C sink and 57.1% of the soil organic carbon sink in cropland, respectively. Nitrogen deposition and climate change have profound influences on SIC cycling. We estimate that ∼19.12%-19.47% of SIC stocks will be further lost by 2100. The consumption of SIC may offset a large portion of global efforts aimed at ecosystem carbon sequestration, which emphasizes the importance of achieving a better understanding of the indirect coupling mechanisms of nitrogen and carbon cycling and of effective countermeasures to minimize SIC loss.

[Pollution Characteristics and Risk Assessment of Polycyclic Aromatic Hydrocarbons in a Suburban Farmland Soil].

In order to assess the pollution of polycyclic aromatic hydrocarbons(PAHs) in a suburban farmland soil, 29 sampling sites were collected around Nanjing according to the grid method, and the contents of 15 different PAHs were determined. Acenaphthene(Ace) was not detected in any of the samples. The total content of PAHs in farmland soil ranged from 24.49 to 750.04 µg·kg-1, with an average of 226.64 µg·kg-1. The spatial distribution of high-ring PAHs, the main PAHs in the farmland soil, was similar to that of total PAHs. There was no significant correlation between PAHs and soil organic matter(SOM), pH, cation exchange capacity(CEC), and total nitrogen(TN), whereas bulk density and low ring PAHs were significantly correlated. The results of source apportionment show that the main source of PAHs in the farmland soil is a mixture of combustion and petroleum. The contamination severity index(CSI) index shows that the PAHs does not pose an ecological risk. The results of the health risk assessment show that there is no potential carcinogenic risk to children or adults, and the main sequence of exposure is skin contact>ingestion>inhalation.

[Landscape Patterns Characteristics of Soil Heavy Metal Pollution in a Town of Southern Jiangsu].

It is of great significance to evaluate the soil heavy metal pollution level and to know their spatial distribution characteristics. Taking soil heavy metals As, Cd, Cr, Cu, Hg, Ni, Pb and Zn in a town of southern Jiangsu as research objects, using the single factor evaluation method, Nemerow comprehensive evaluation method, geostatistical analysis method together with the landscape pattern grain effect and the landscape index analysis method, we studied their characteristics of landscape patterns in the study area based on pollution evaluation. The results showed that:① The average value range of single factor pollution index and Nemerow comprehensive evaluation index for soil heavy metals in study area was 0.145-0.893.The overall pollution level was low. The pollution level of south area was lower than that of north area; ② As, Pb, Hg, and Zn elements showed obvious non-point pollution characteristics.As and Pb showed a similar spatial distribution. So were Hg and Zn elements. In contrast, Cd, Cr, Cu and Ni elements showed obvious point pollution characteristics. Cd and Cr showed similar spatial distribution. So were Cu and Ni elements; ③ The suitable grain effect landscape index of nine soil heavy metals pollution landscape was 30-40 m; ④ The low concentration area of soil heavy metals in the study area accounted for the largest proportion. The border of lower concentration area was the most complex part. The distribution of all pollution level areas was relatively concentrated and the comprehensive pollution fragmentation degree was low. The source pollution of soil heavy metals was in concentrated distribution, and its number still counted low, but there was a tendency for further development. As a whole, it was still in the early pollution stage of soil heavy metals.

[Study on soil organic carbon pools and turnover characteristics along an elevation gradient in Qilian Mountain].

On the basis of the first order dynamic model combining with the laboratory soil incubation experiment, characteristics of soil organic carbon pools(Csoc), active carbon pools(Ca), slow carbon pools(Cs), passive carbon pools(Cr) and their turnover in Qilian Mountain were studied. It has been showed that the size of Csoc in horizon A and B ranges from 7.606- 89.026 g.kg - and 5.804-84.267 g.kg-1, which shows tendency of "increase-decrease-increase-decrease" with elevation. The size of Cs, Cs, and Cr in horizon A and B under different elevations respectively ranges from 0.180-1.328 g.kg-1, 0.159-1.273 g.kg-1; 3.650-35.173 g.kg-1, 3.703-43. 623 g.kg-1; 3.776-65.298 g.kg-1, 1.942-48. 121 g.kg-1, which incarnates no obvious variation law with elevation. The contents of Csoc, Cr and Cs significantly differ with different elevation gradients. There is no significant difference in the C, content between different elevation gradients. Decomposition rate of Csoc also has no evident change law in elevation. The peak of daily carbon release rate varies with carbon release rate in the whole incubation process, which could be used to present character of SOC turnover rate. It has been also showed that Caand peak of daily carbon release rate have a significant relationship, and they follow the linear relationship. The incubation reveals that Csoc turns over in sequence of Ca, Cs, and Cr,. Polynomial equation presents relation between total SOC release amount and time, of which cubic polynomial has achieved preferable precision(R2 >0.99).

Spatial variations of heavy metals in the soils of vegetable-growing land along urban-rural gradient of Nanjing, China.

China has experienced rapid urbanization in recent years. The acceleration of urbanization has created wealth and opportunity as well as intensified ecological and environmental problems, especially soil pollution. Our study concentrated on the variation of heavy metal content due to urbanization in the vegetable-growing soil. Laws and other causes of the spatial-temporal variation in heavy metal content of vegetable-growing soils were analyzed for the period of urbanization in Nanjing (the capital of Jiangsu province in China). The levels of Cu, Zn, Pb, Cd and Hg in samples of vegetable-growing soil were detected. The transverse, vertical spatio-temporal variation of heavy metals in soil was analyzed on the base of field investigations and laboratory analysis. The results show that: (1) in soil used for vegetable production, the levels of heavy metals decreased gradually from urban to rural areas; the levels of the main heavy metals in urban areas are significantly higher than suburban and rural areas; (2) the means of the levels of heavy metals, calculated by subtracting the sublayer (15-30 cm) from the toplayer (0-15 cm), are all above zero and large in absolute value in urban areas, but in suburban and rural areas, the means are all above or below zero and small in absolute value. The causes of spatial and temporal variation were analyzed as follows: one cause was associated with mellowness of the soil and the length of time the soil had been used for vegetable production; the other cause was associated with population density and industrial intensity decreasing along the urban to rural gradient (i.e., urbanization levels can explain the distribution of heavy metals in soil to some extent). Land uses should be planned on the basis of heavy metal pollution in soil, especially in urban and suburban regions. Heavily polluted soils have to be expected from food production. Further investigation should be done to determine whether and what kind of agricultural production could be established near urban centers.

[Study on canopy spectral characteristics of paddy polluted by heavy metals].

Because of frequent mining, heavy metals are brought into environment like soils, water and atmosphere, resulting heavy metal contamination in the agricultural region beside mines. Heavy metals contamination causes vegetation stress like destruction of chloroplast structure, chlorophyll content decrease, blunt photosynthesis, etc. Spectral responses to changes in chlorophyll content and photosynthesis make it possible that remote sensing is applied in monitoring heavy metals stress on paddy plants. Field spectroradiometer was used to acquire canopy reflectance spectra of paddy plants contaminated by heavy metals released from local mining. The present study was conducted to (1) investigate discrimination of canopy reflectance spectra of heavy metal polluted and normal paddy plants; (2) extract spectral characteristics of contaminated paddy plants and compare them. By means of correlation analysis, sensitive bands (SB) were firstly picked out from canopy spectra. Secondly, on the basis of these sensitive bands, normalized difference vegetation indices (NDVI) were established, and then red edge position (REP) was extracted from canopy spectra via curve fitting of inverted Gaussian model. As a result of correlation analysis, 460, 560, 660 and 1 100 nm were considered respectively as sensitive band for Pb, Zn, Cu and As concentration in paddy leaves. Furthermore, heavy metal concentrations (Pb, Zn, Cu and As) were significantly correlated with NDVIs (Pb, NDV(510, 810); Zn, NDVI(510, 870; Cu, NDVI(660, 870); As, NDVI(510, 810)). Heavy metals were also significantly correlated with REP, however, the inflexion termed as spectral critical value (SCV) between low and high heavy metals concentrations should be considered during applying REP in remote sensing monitoring. Moreover, NDVI and REP are much better than SB in terms of capability of expressing spectral information. Therefore, heavy metals contamination in paddy plants can be remotely monitored via ground spectroradiometer when NDVI and REP are selected as spectral characteristics.

[Simulation of methane emissions from rice fields in the Taihu Lake region, China by using different unit of soil database with the DNDC model].

Application of a biogeochemical model, DeNitrification and DeComposition or DNDC, was discussed to assess the impact of CH4 emissions on different soil database from rice fields in Taihu Lake region of China. The results showed that CH4 emissions of the polygon-based soil database of 1:50000, which contained 52034 polygons of paddy soils representing 1107 paddy soil profiles extracted from the latest national soil map (1:50000), were located within the ranges produced by the county-based soil database of 1:50000. However, total emissions of the whole area differed by about 1680 Gg CH4-C. Moreover, CH4 emissions of the polygon-based soil database of 1:50000 and the county-based soil database of 14,000,000, which was the most popular data source when DNDC model was applied in China, have a big estimation discrepancy among each county-based unit in spite of total emissions of the whole area by a difference of 180 Gg CH4-C. This indicated that the more precise soil database was necessary to better simulate CH4 emissions from rice fields in Taihu Lake region using the DNDC model.

[Effects of different types of litters on soil organic carbon mineralization].

Using litter incubation experiment in laboratory, decomposition discrepancies of four typical litters from Zijin Mountain were analyzed. The results show that organic carbon mineralization rates of soil with litters all involve fast and slow decomposition stages, and the differences are that the former has shorter duration,more daily decomposition quantity while the latter is opposite. Organic carbon mineralization rates of soil with litters rapidly reached maximum in the early days of incubation, and the order is soil with Cynodon dactylon litter (CK + BMD) (23.88 +/- 0.62) mg x d(-1), soil with Pinus massoniana litter (CK+ PML) (17.93 +/- 0.99) mg x d(-1), soil with Quercus acutissima litter (CK+ QAC) (15.39 +/- 0.16) mg x d(-1) and soil with Cyclobalanopsis glauca litter (CK + CGO) (7.26 +/- 0.34) mg x d(-1), and with significant difference between each other (p < 0.05). This order has not significant correlation to litter initial chemical elements. The amount of organic carbon mineralized accumulation within three months incubation is (CK + BMD) (338.21 +/- 6.99) mg, (CK + QAC) (323.48 +/- 13.68) mg, (CK + PML) (278.34 +/- 13.91) mg and (CK + CGO) (245.21 +/- 4.58) mg. 198.17-297.18 mg CO2-C are released during litter incubation, which occupies 20.29%-31.70% of the total litter organic carbon amounts. Power curve model can describe the trends of organic carbon mineralization rate and mineralized accumulation amount,which has a good correlation with their change.

[Analysis of visible and near-infrared spectra of As-contaminated soil in croplands beside mines].

Soil samples in the depth from 0 to 20 cm were scooped from agricultural region beside mines and prepared for determination of As concentration, Fe concentrations and organic matter content. At the same time they were scanned by mobile hyperspectral radiometer for visible and near-infrared spectra. Savitzky-Golay filter was used to smooth noises in spectrum curve because of some low signal-to-noise ratios in some regions of visible and near-infrared light, and all the spectra were resampled with the spectral interval of 10 nm. Before principal component regression and partial least square regression models were constructed for predicting As concentration, Fe concentrations and OM content, several spectral preprocessing techniques like first/second derivative (F/SD), baseline correction (B), standard normalized variate (SNV), multiplicative scatter correction (MSC) and continuum removal (CR) were used for promotion of models' robustness and predicting performance. For limited samples, cross validation was carried out by repeated leave-one-out procedure, and root mean square error of prediction (RMSEP) was used for validating the prediction ability of constructed models. In this study principal component regression models behave better than partial least square regression models in representing regressing ability, reducing risk of over-fitting with less factors and ensuring models' accuracy and pertinences (relative RMSEP and R2). Preprocessing techniques of SNV, MSC and CR improve obviously the prediction ability of models for As concentration, Fe concentrations and OM content with relative RMSEP equal to 0.3040, 0.1443 and 0.1712, with number of factors equal to 5, 3 and 3, respectively. The analysis of regression vectors of selected optimal PCR models shows that several important wavelengths are simultaneously taken and helpful for prediction performance: 450, 1,000, 1,400, 1,900, 2,050, 2,200, 2,250, 2,400 and 2,470 nm. Application of the calibrated models to soil contamination of croplands is promising. Concentrations of soil contaminants and contents of other matter can be determined by reflectance spectroscopy with high spectra resolution, which would provide potent reference for remote sensing monitoring of soil and environmental quality.

[Study on intelligent system of hyper-spectral data gathering based on wireless data communication technology in farm machinery].

In order to meet the needs of highly dense and overall farmland information gathering, wireless data communicating, and real-time processing in the precision agriculture, this system integrated GPS, GIS and RS based on the technology of computer and wireless data transmission. On the one hand, the system makes DGPS and Hyper-spectrograph integrated through the AT891v52 MCU, providing the accurate space position and realizing the integration of spectrum data acquisition and orientation. On the other hand, the system realizes the communication between the data gathering control system and the microcomputer by using the nRF905 system. Meanwhile the system has realized the visualized analysis and management of the spectrum data by integrating Visual Basic and Map-Objects into GIS, displaying real-time trace of moving point and some related attributes of the moving point in map layers, and calculating crop derivative spectra and crop vegetation index NDVI etc. Thus, sufficient information was provided for expert system and decision support system of precision agriculture.

[Study on intelligent system of hyper-spectral data gathering based on GPS in farm machinery].

In order to meet the precision agriculture needs that highly dense and overall farmland information is gathered, this system uses Visual Basic and Map-Objects to carry on integration of GPS, GIS and RS. On the one hand, the system can provide the space seat attribute of high precision for the spectral data gathered by way of integration GPS, and realizes integration in spectrum data gathering, orientation and storage. On the other hand, by way of integrated GIS, the system has realized the function of visualizing analysis and management of the spectrum data, displaying real-time trace of moving point, providing some related attribute of the moving point in map layers, and calculating crop derivative spectra and crop vegetation index NDVI etc. The sufficient information is put forward for expert system and decision support system of precision agriculture.

[Role of mass media during the severe acute respiratory syndrome epidemic].

OBJECTIVE: To understand the impact of effective interaction between public and media on the prevention and control of severe acute respiratory syndrome (SARS). METHODS: Based on the theory of field epidemiology, the traditional and modern technologies were brought forward. In the late period of SARS epidemic, investigation on knowledge, attitude and practice on SARS prevention and control among general population was conducted. RESULTS: During the 3 month period of SARS epidemic in Shenzhen, techniques of the "E-health and public health informatics" as an emerging fields were used to focus on population to eventually improve the health of entire population. Methods as television, radio, newspapers, magazines, printing and distribution of specific materials on SARS were included, and hotlines of telephone and mobile phone, web-based sites, electronic screening advertisements, and consultation or forum for the public etc. were used. Among 3405 subjects interviewed, more than 95% gave right answers on the SARS related questions. Most of them held the optimistic and scientific attitude. 80% of the population had taken the measures as recommended. 82.4% of the citizens were happy about the local government's action and 93.8% thought hospitals and healthcare workers should be respected and honored. CONCLUSION: Dealing with the urgent public health problems and emerging infectious diseases outbreak, epidemiologists need to keep good relations with media, and making use of modern electronic technologies to communicate with the public.