Chunzi Ma

Establishing eutrophication assessment standards for four lake regions, China

The trophic status assessment of lakes in different lake regions may provide important and fundamental information for lake trophic state classification and eutrophication control. In this study, a region-specific lake eutrophication assessment standard was established through a frequency distribution method based on chlorophyll-a concentration. The assessment standards under the oligotrophic state for lakes in the Eastern plain, Yungui Plateau, Northeast Plain and Mountain Mongolia-Xinjiang regions are total phosphorus of 0.068, 0.005, 0.011, 0.005 mg/L; total nitrogen of 1.00, 0.16, 0.37, 0.60 mg/L; Secchi depth of 0.60, 8.00, 1.55, 3.00 m; and COD(Mn) of 2.24, 1.00, 5.11, 4.00 mg/L, respectively. Moreover, a region-specific comprehensive trophic level index was developed to provide an understandable assessment method for the public. The results indicated that the frequency distribution analysis based on chlorophyll-a combined with trophic level index provided a useful metric for the assessment of the lake trophic status. In addition, the difference of eutrophication assessment standards in different lake regions was analyzed, which suggested that the sensitivities of algae to nutrients and the assessment standard of trophic status possessed significant regional differences for the four lake ecoregions. Lake eutrophication assessment standards would contribute to maximizing the effectiveness of future management strategies, to control and minimize lake eutrophication problems.

Determining reference conditions for TN, TP, SD and Chl-a in eastern plain ecoregion lakes, China

Establishing the nutrient reference condition (baseline environmental condition) of lakes in an ecoregion is a critical consideration in the development of scientifically defensible aquatic nutrient criteria. Three methods were applied to determine reference conditions in the Eastern plain ecoregion lakes with respect to total phosphorus (TP), total nitrogen (TN), planktonic chlorophyll a (Chl-a) and Secchi depth (SD). The reference condition value for the lakes in the Eastern plain ecoregion by the trisection method is TP of 0.029 mg/L, TN of 0.67 mg/L, Chl-a of 3.92 mg/m3, SD of 0.85 m, and the reference condition range by the lake population distribution approach is TP of 0.014-0.043 mg/L, TN of 0.360-0.785 mg/L, Chl-a of 1.78-4.73 mg/m3, SD of 0.68-1.21 m. Additionally, empirical models were developed for estimating the reference Chl-a concentration and SD successfully for lakes in the Eastern plain ecoregion. Overall, the data suggest that multiple methods can be used to determine reference conditions and that in Eastern plain ecoregion lakes the reference condition corresponds to a mesotrophic status.

Stressor-response models: a practical application for the development of lake nutrient criteria in China.

C has numerous lakes with significant regional diversity that have been threatened by extensive eutrophication. The current water quality standards (WQS) for lake protection and eutrophication control were promulgated in 2002. However, the WQS are not supported by corresponding numeric nutrient criteria and do not consider regional differences. Therefore, regional lake nutrient criteria (LNC) must be developed to better reflect the regional ecoenvironment and current lake management needs in China. China has implemented the Regional Nutrient Criteria Research Plan since 2008 to formulate nutrient ecoregions and recommend regional LNC. Because there was no systematic research to support the development of LNC in China, the plan was mainly developed as a case study to explore the feasibility of the lake population distribution, reference lake, trisection, and model extrapolation methods recommended by the U.S. Environmental Protection Agency (EPA). However, these methods are not applicable to LNC establishment in China because of the widespread contamination of aquatic ecosystems by industrialization, urbanization, and agriculture across various lake ecoregions. Furthermore, these methods do not consider the attainment of designated water uses for determining LNC. Therefore, there is an urgent need to develop suitable methods for establishing LNC in China. Nutrients found in lakes, such as nitrogen (N) and phosphorus (P), are not toxic to aquatic organisms and humans at low concentrations, and methods to derive numeric criteria that represent the toxic effects of chemical pollutants using simple laboratory studies have limited applicability to LNC development. Excess nutrients stimulate the deleterious proliferation of planktonic algal, which leads to oxygen depletion, reduced light transparency, the loss of biodiversity, and the production of algal toxins, eventually disrupting aquatic life, recreation, and drinking water supplies. Thus, stressor− response models (SRMs) representing the most important known relationships between N and P concentrations and primary productivity have been developed based on analyses of observational data collected in the field. SRMs are suitable for deriving the nutrient criteria of lakes affected by anthropogenic activities based on a given algal biomass criterion to protect the designated water uses in China. Moreover, the chlorophyll a concentration (Chl a), which is strongly related to the algal biomass, can serve as an important variable that is linked to nutrient concentrations when developing LNC for designated water uses. For example, LNC in support of drinking water supplies are affected by increased levels of algal toxins and organic carbon associated with algal blooms. Therefore, a target value (or criterion) for the response to Chl a must be established before N and P criteria for drinking water supplies can be derived using SRMs. The US EPA has adopted the use of SRMs to derive numeric N and P criteria to develop designated water uses based on Chl a. To date, SRMs have not been extensively applied to the development of LNC in China. Therefore, it is necessary for Chinese researchers to begin to apply the currently available SRMs for nutrients to Chinese lakes and to conduct research necessary for the development of regional LNC, especially for lake ecoregions with severe anthropogenic activities that reflect the basin characteristics of Chinese lakes. The adoption of SRMs to determine the ecoregional LNC in China will be challenging for several reasons. (1) Determining or obtaining the relationship between Chl a and the key indicators reflecting the designated water uses is the first issue that should be resolved. To derive a nutrient criterion using SRMs, the criterion value for Chl a should be initially established for diverse designated water uses in different lake ecoregions. Moreover, when defining Chl a criteria for lakes that have a designated water use, the aforementioned causal chain that ultimately affects the attainment of designated uses for lakes should be clarified. (2) The sensitivity of algal to nutrients might display significant heterogeneity across various lake types. The SRMs are susceptible to being confounded with environment factors such as species biogeography, lake depth, watershed area, salinity, and water color. Hence, these factors

National investigation of semi-volatile organic compounds (PAHs, OCPs, and PCBs) in lake sediments of China: Occurrence, spatial variation and risk assessment

In this study, a large scale investigation of semi-volatile organic compounds (SVOCs) in sediments from 52 lakes, located in five geographic regions across China, was conducted to assess sediment quality in terms of organic contaminants. Concentrations of polycyclic aromatic hydrocarbons (PAHs), organochlorine pesticides (OCPs), and polychlorinated biphenyls (PCBs) in sediment were found to range between 17.00-6,633, 0.12-45.24, and 0.03-13.99ngg-1, respectively. Lake sediments from different regions exhibited variation in contamination levels, and in the compositions of isomers. The descending order of contamination levels for the three SVOCs groups (i.e., ∑PAHs, ∑OCPs, ∑PCBs) were as follows: the eastern plain region (EPR)>the Yunnan-Guizhou plateau (YGP)>the northeast China region (NCR)>the Qinghai-Tibet plateau (QTP)>the Mongolia-Xinjiang plateau (MXP). High molecular weight PAHs, OCPs and PCBs were found at high concentrations in parts of the EPR and YGP, while lighter isomers were likely to be atmospherically transported, resulting in their nationwide distribution. The sources and type variation (local input or atmospheric deposition) are the primary controls of spatial variation. Additionally, human related socio-economic factors, and geographic conditions also played important roles in influencing the spatial differentiation. According to simple sediment quality guidelines (SQG), the risks posed by PCBs in sediments were not as serious as those posed by PAHs and DDT.

Performance assessment of water quality monitoring system and identification of pollution source using pattern recognition techniques: a case study of Chaohu Lake, China

Abstract The present study intends to evaluate the properties of two pattern recognition methods, principal component analysis (PCA) and cluster analysis (CA), for a better management of the water quality monitoring systems, and then to identify those lake areas with similar pollution behaviors and possible pollution sources. These methods were employed to analyze the four indexes: chlorophyll-a, secchi depth, total nitrogen, and total phosphorus, and were compared with each other. The results indicated that the classification outcomes by the PCA were consistent with those by the CA. Twelve monitoring sites were classified into 5, 7, or 8 groups based on their similarity characteristics of the pollution level. In addition, the pollution sources in the Chaohu Lake were mainly exogenous pollution, derived from the four rivers into the lake. These facts demonstrated that the PCA and CA methods had a great application potential for a better management of the water quality monitoring system, and the present pa...

Prediction of physico-chemical variables and chlorophyll a criteria for ecoregion lakes using the ratios of land use to lake depth

Establishing nutrient criteria for regional lakes is necessary to assess human impact on lake aquatic ecosystems and protect water quality and biotic integrity. Multiple linear regression models, in which the ratios of land use to mean lake depth (DEP) are the predictor variables, and the logarithms of physico-chemical variables and Chl a concentrations are the dependent variables, were developed to predict physico-chemical variables and chlorophyll a criteria for Yungui Plateau Ecoregion lakes. The contemporary land use data of 22 lake watersheds were analyzed and employed to develop the spatial relationship with the regression models. The data of five lake watersheds in four periods were used to verify the accuracy of the regression models, and to test their applicability in time scale. The intercept of these models (i.e., expected physico-chemical variables and Chl a concentrations in the absence of human activities) represents the criterion concentrations. Results suggested that the percentages of other construction land/DEP had strong positive influences on the concentrations of all variables (except electrical conductivity). The multiple linear regression models offered a potential method for regions with heavy anthropogenic disturbances to develop the physico-chemical variables and Chl a criteria.

Establishing Reference Conditions for Lake Water Quality: A Novel Extrapolation Approach

The serious lake eutrophication has drawn increasingly attention, requiring further and deeper knowledge to understand its restriction factors of pre-disturbance conditions or historical reference conditions. In the meanwhile, Lake Nutrient Reference Conditions (LNRCs) are important indicators of eutrophication but hardly determined in the presence of eutrophication. In this research, a novel extrapolation approach was raised to determine LNRCs and its impacts on eutrophication, with the integral model of Optimal Map Recognition (OMR) and Pattern Recognition Inverse Mapping (PRIM). Validated with public data and experimental simulation, the approach was suggested as a reliable extrapolation for LNRCs determination. Further case study on Dianshan Lake and Chenghai Lake applied the novel extrapolation model in real eutrophication estimation and prediction, the results of which were in good agreement with those deduced by other techniques.

Development of methods for establishing nutrient criteria in lakes and reservoirs: A review

Nutrient criteria provide a scientific foundation for the comprehensive evaluation, prevention, control and management of water eutrophication. In this review, the literature was examined to systematically evaluate the benefits, drawbacks, and applications of statistical analysis, paleolimnological reconstruction, stressor-response model, and model inference approaches for nutrient criteria determination. The developments and challenges in the determination of nutrient criteria in lakes and reservoirs are presented. Reference lakes can reflect the original states of lakes, but reference sites are often unavailable. Using the paleolimnological reconstruction method, it is often difficult to reconstruct the historical nutrient conditions of shallow lakes in which the sediments are easily disturbed. The model inference approach requires sufficient data to identify the appropriate equations and characterize a waterbody or group of waterbodies, thereby increasing the difficulty of establishing nutrient criteria. The stressor-response model is a potential development direction for nutrient criteria determination, and the mechanisms of stressor-response models should be studied further. Based on studies of the relationships among water ecological criteria, eutrophication, nutrient criteria and plankton, methods for determining nutrient criteria should be closely integrated with water management requirements.

Phytoplankton response to climate changes and anthropogenic activities recorded by sedimentary pigments in a shallow eutrophied lake

Studies that address the potential effects of climate and anthropogenic activities on lacustrine phytoplankton succession are scarce in the shallow lakes. In the present work, the succession of phytoplankton community inferred from sedimentary pigments has been investigated; the impacts of climate and anthropogenic activities on the succession have been evaluated by the generalized additive models (GAMs) in a shallow eutrophied lake, Lake Chaohu, located eastern China. The results show that phytoplankton succession can be divided into two periods: pre-1960s and post 1960s. The mean values of ββ‑Car and Chl a increased after the 1960s at both sites sampled, from 0.013 to 0.359, and 0.013 to 1.382 μg g-1, respectively (site C4), and from 0.015 to 0.530, and 0.010 to 0.921 μg g-1, respectively (site C14), reflecting significant increases of primary productivity since the 1960s. The percentage of diatoms and dinoflagellates preserved in sediments decreased from ~90% to ~15% since the 1960s, while cyanobacteria and green algae increased from ~5% to ~35%, respectively, reflecting the shift of the lake phytoplankton community. This succession was related to construction of the Chaohu Dam in 1963, increasing discharges of anthropogenic N and P into the Lake, and a generally warming environment as reflected by increasing average air temperatures. The results of GAMs showed aquatic total phosphorus (TP) concentration is the dominant contributor to phytoplankton community change, explaining 42.74%, 40.27%, 40.77% and 72.28% of the variance of total algae, cyanobacteria, green algae, and diatoms and dinoflagellates, respectively. The positive impacts of increasing TP concentrations on abundances of total algae, cyanobacteria, and green algae were observed during periods of relatively high TP concentrations since the mid-1970s. The positive responses of total algae, cyanobacteria, green algae and diatoms and dinoflagellates to increasing average air temperatures were observed since the mid-1990s, showing that a generally warmer environment facilitated algae proliferation.